From 692c0c155dd2f9c8285fb95ede288a18f2ded600 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 24 Nov 2022 23:13:05 +0100
Subject: [PATCH 01/64] Begin refactoring ItemsPresenter.

A lot still broken, in particular virtualization is completely removed.`ItemsPresenter` now no longer has an `Items` or `ItemTemplate` property; it detects when it's hosted in an `ItemsControl`. `IItemsPresenter` interface removed.
---
 .../ControlCatalog/Pages/DialogsPage.xaml.cs  |  588 +++---
 .../HamburgerMenu/HamburgerMenu.xaml          |    4 +-
 .../Themes/Fluent/ColorView.xaml              |    5 +-
 .../Themes/Simple/ColorView.xaml              |    5 +-
 src/Avalonia.Controls/ComboBox.cs             |    2 +-
 src/Avalonia.Controls/IVirtualizingPanel.cs   |   78 -
 src/Avalonia.Controls/ItemsControl.cs         |   12 +-
 src/Avalonia.Controls/ListBox.cs              |    2 +-
 .../Presenters/CarouselPresenter.cs           |  344 ++--
 .../Presenters/IItemsPresenter.cs             |   18 -
 .../Presenters/IItemsPresenterHost.cs         |    4 +-
 .../Presenters/ItemContainerSync.cs           |  125 --
 .../Presenters/ItemVirtualizer.cs             |  303 ---
 .../Presenters/ItemVirtualizerNone.cs         |  106 -
 .../Presenters/ItemVirtualizerSimple.cs       |  606 ------
 .../Presenters/ItemsPresenter.cs              |  187 +-
 .../Presenters/ItemsPresenterBase.cs          |  308 ---
 .../ItemsPresenterContainerGenerator.cs       |  108 +
 .../Primitives/SelectingItemsControl.cs       |    2 +-
 .../VirtualizingStackPanel.cs                 |  252 +--
 .../Controls/Carousel.xaml                    |    1 -
 .../Controls/ComboBox.xaml                    |    5 +-
 .../Controls/ContextMenu.xaml                 |    2 -
 .../Controls/ItemsControl.xaml                |    4 +-
 .../Controls/ListBox.xaml                     |    5 +-
 .../Controls/ManagedFileChooser.xaml          |    5 +-
 src/Avalonia.Themes.Fluent/Controls/Menu.xaml |    4 -
 .../Controls/MenuFlyoutPresenter.xaml         |    2 -
 .../Controls/MenuItem.xaml                    |    2 -
 .../Controls/TabControl.xaml                  |    2 -
 .../Controls/TabStrip.xaml                    |    4 +-
 .../Controls/TreeView.xaml                    |    1 -
 .../Controls/TreeViewItem.xaml                |    1 -
 .../Controls/Carousel.xaml                    |    1 -
 .../Controls/ComboBox.xaml                    |    5 +-
 .../Controls/ContextMenu.xaml                 |    2 -
 .../Controls/ItemsControl.xaml                |    2 -
 .../Controls/ListBox.xaml                     |    5 +-
 src/Avalonia.Themes.Simple/Controls/Menu.xaml |    4 -
 .../Controls/MenuFlyoutPresenter.xaml         |    2 -
 .../Controls/MenuItem.xaml                    |    2 -
 .../Controls/TabControl.xaml                  |    2 -
 .../Controls/TabStrip.xaml                    |    2 -
 .../Controls/TreeView.xaml                    |    1 -
 .../Controls/TreeViewItem.xaml                |    1 -
 .../CarouselTests.cs                          |    1 -
 .../ComboBoxTests.cs                          |    1 -
 .../ItemsControlTests.cs                      |    4 +-
 .../ListBoxTests.cs                           |   52 +-
 .../ListBoxTests_Multiple.cs                  |    1 -
 .../ListBoxTests_Single.cs                    |    1 -
 .../Presenters/CarouselPresenterTests.cs      | 1464 ++++++-------
 .../Presenters/ItemsPresenterTests.cs         |  370 +---
 .../ItemsPresenterTests_Virtualization.cs     |  748 +++----
 ...emsPresenterTests_Virtualization_Simple.cs | 1822 ++++++++---------
 .../Primitives/PopupTests.cs                  |    5 +-
 .../Primitives/SelectingItemsControlTests.cs  |    2 -
 .../SelectingItemsControlTests_AutoSelect.cs  |    1 -
 .../SelectingItemsControlTests_Multiple.cs    |    1 -
 .../Primitives/TabStripTests.cs               |    1 -
 .../TreeViewTests.cs                          |    2 -
 .../VirtualizingStackPanelTests.cs            |  522 ++---
 .../AutoDataTemplateBindingHookTest.cs        |    1 -
 tests/Avalonia.UnitTests/TestExtensions.cs    |    1 -
 64 files changed, 3040 insertions(+), 5086 deletions(-)
 delete mode 100644 src/Avalonia.Controls/Presenters/IItemsPresenter.cs
 delete mode 100644 src/Avalonia.Controls/Presenters/ItemContainerSync.cs
 delete mode 100644 src/Avalonia.Controls/Presenters/ItemVirtualizer.cs
 delete mode 100644 src/Avalonia.Controls/Presenters/ItemVirtualizerNone.cs
 delete mode 100644 src/Avalonia.Controls/Presenters/ItemVirtualizerSimple.cs
 delete mode 100644 src/Avalonia.Controls/Presenters/ItemsPresenterBase.cs
 create mode 100644 src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs

diff --git a/samples/ControlCatalog/Pages/DialogsPage.xaml.cs b/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
index 67e9ef4e407..41a5b86ebda 100644
--- a/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
+++ b/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
@@ -24,301 +24,301 @@ public DialogsPage()
         {
             this.InitializeComponent();
 
-            var results = this.Get<ItemsPresenter>("PickerLastResults");
-            var resultsVisible = this.Get<TextBlock>("PickerLastResultsVisible");
-            var bookmarkContainer = this.Get<TextBox>("BookmarkContainer");
-            var openedFileContent = this.Get<TextBox>("OpenedFileContent");
-            var openMultiple = this.Get<CheckBox>("OpenMultiple");
-
-            IStorageFolder? lastSelectedDirectory = null;
-
-            List<FileDialogFilter> GetFilters()
-            {
-                if (this.Get<CheckBox>("UseFilters").IsChecked != true)
-                    return new List<FileDialogFilter>();
-                return  new List<FileDialogFilter>
-                {
-                    new FileDialogFilter
-                    {
-                        Name = "Text files (.txt)", Extensions = new List<string> {"txt"}
-                    },
-                    new FileDialogFilter
-                    {
-                        Name = "All files",
-                        Extensions = new List<string> {"*"}
-                    }
-                };
-            }
-
-            List<FilePickerFileType>? GetFileTypes()
-            {
-                if (this.Get<CheckBox>("UseFilters").IsChecked != true)
-                    return null;
-                return new List<FilePickerFileType>
-                {
-                    FilePickerFileTypes.All,
-                    FilePickerFileTypes.TextPlain
-                };
-            }
-
-            this.Get<Button>("OpenFile").Click += async delegate
-            {
-                // Almost guaranteed to exist
-                var uri = Assembly.GetEntryAssembly()?.GetModules().FirstOrDefault()?.FullyQualifiedName;
-                var initialFileName = uri == null ? null : System.IO.Path.GetFileName(uri);
-                var initialDirectory = uri == null ? null : System.IO.Path.GetDirectoryName(uri);
-
-                var result = await new OpenFileDialog()
-                {
-                    Title = "Open file",
-                    Filters = GetFilters(),
-                    Directory = initialDirectory,
-                    InitialFileName = initialFileName
-                }.ShowAsync(GetWindow());
-                results.Items = result;
-                resultsVisible.IsVisible = result?.Any() == true;
-            };
-            this.Get<Button>("OpenMultipleFiles").Click += async delegate
-            {
-                var result = await new OpenFileDialog()
-                {
-                    Title = "Open multiple files",
-                    Filters = GetFilters(),
-                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
-                    AllowMultiple = true
-                }.ShowAsync(GetWindow());
-                results.Items = result;
-                resultsVisible.IsVisible = result?.Any() == true;
-            };
-            this.Get<Button>("SaveFile").Click += async delegate
-            {
-                var filters = GetFilters();
-                var result = await new SaveFileDialog()
-                {
-                    Title = "Save file",
-                    Filters = filters,
-                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
-                    DefaultExtension = filters?.Any() == true ? "txt" : null,
-                    InitialFileName = "test.txt"
-                }.ShowAsync(GetWindow());
-                results.Items = new[] { result };
-                resultsVisible.IsVisible = result != null;
-            };
-            this.Get<Button>("SelectFolder").Click += async delegate
-            {
-                var result = await new OpenFolderDialog()
-                {
-                    Title = "Select folder",
-                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null
-                }.ShowAsync(GetWindow());
-                if (string.IsNullOrEmpty(result))
-                {
-                    resultsVisible.IsVisible = false;
-                }
-                else
-                {
-                    lastSelectedDirectory = new BclStorageFolder(new System.IO.DirectoryInfo(result));
-                    results.Items = new[] { result };
-                    resultsVisible.IsVisible = true;
-                }
-            };
-            this.Get<Button>("OpenBoth").Click += async delegate
-            {
-                var result = await new OpenFileDialog()
-                {
-                    Title = "Select both",
-                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
-                    AllowMultiple = true
-                }.ShowManagedAsync(GetWindow(), new ManagedFileDialogOptions
-                {
-                    AllowDirectorySelection = true
-                });
-                results.Items = result;
-                resultsVisible.IsVisible = result?.Any() == true;
-            };
-            this.Get<Button>("DecoratedWindow").Click += delegate
-            {
-                new DecoratedWindow().Show();
-            };
-            this.Get<Button>("DecoratedWindowDialog").Click += delegate
-            {
-                _ = new DecoratedWindow().ShowDialog(GetWindow());
-            };
-            this.Get<Button>("Dialog").Click += delegate
-            {
-                var window = CreateSampleWindow();
-                window.Height = 200;
-                _ = window.ShowDialog(GetWindow());
-            };
-            this.Get<Button>("DialogNoTaskbar").Click += delegate
-            {
-                var window = CreateSampleWindow();
-                window.Height = 200;
-                window.ShowInTaskbar = false;
-                _ = window.ShowDialog(GetWindow());
-            };
-            this.Get<Button>("OwnedWindow").Click += delegate
-            {
-                var window = CreateSampleWindow();
-
-                window.Show(GetWindow());
-            };
-
-            this.Get<Button>("OwnedWindowNoTaskbar").Click += delegate
-            {
-                var window = CreateSampleWindow();
-
-                window.ShowInTaskbar = false;
-
-                window.Show(GetWindow());
-            };
-
-            this.Get<Button>("OpenFilePicker").Click += async delegate
-            {
-                var result = await GetStorageProvider().OpenFilePickerAsync(new FilePickerOpenOptions()
-                {
-                    Title = "Open file",
-                    FileTypeFilter = GetFileTypes(),
-                    SuggestedStartLocation = lastSelectedDirectory,
-                    AllowMultiple = openMultiple.IsChecked == true
-                });
-
-                await SetPickerResult(result);
-            };
-            this.Get<Button>("SaveFilePicker").Click += async delegate
-            {
-                var fileTypes = GetFileTypes();
-                var file = await GetStorageProvider().SaveFilePickerAsync(new FilePickerSaveOptions()
-                {
-                    Title = "Save file",
-                    FileTypeChoices = fileTypes,
-                    SuggestedStartLocation = lastSelectedDirectory,
-                    SuggestedFileName = "FileName",
-                    DefaultExtension = fileTypes?.Any() == true ? "txt" : null,
-                    ShowOverwritePrompt = false
-                });
-
-                if (file is not null && file.CanOpenWrite)
-                {
-                    // Sync disposal of StreamWriter is not supported on WASM
-#if NET6_0_OR_GREATER
-                    await using var stream = await file.OpenWriteAsync();
-                    await using var reader = new System.IO.StreamWriter(stream);
-#else
-                    using var stream = await file.OpenWriteAsync();
-                    using var reader = new System.IO.StreamWriter(stream);
-#endif
-                    await reader.WriteLineAsync(openedFileContent.Text);
-
-                    lastSelectedDirectory = await file.GetParentAsync();
-                }
-
-                await SetPickerResult(file is null ? null : new [] {file});
-            };
-            this.Get<Button>("OpenFolderPicker").Click += async delegate
-            {
-                var folders = await GetStorageProvider().OpenFolderPickerAsync(new FolderPickerOpenOptions()
-                {
-                    Title = "Folder file",
-                    SuggestedStartLocation = lastSelectedDirectory,
-                    AllowMultiple = openMultiple.IsChecked == true
-                });
-
-                await SetPickerResult(folders);
-
-                lastSelectedDirectory = folders.FirstOrDefault();
-            };
-            this.Get<Button>("OpenFileFromBookmark").Click += async delegate
-            {
-                var file = bookmarkContainer.Text is not null
-                    ? await GetStorageProvider().OpenFileBookmarkAsync(bookmarkContainer.Text)
-                    : null;
-
-                await SetPickerResult(file is null ? null : new[] { file });
-            };
-            this.Get<Button>("OpenFolderFromBookmark").Click += async delegate
-            {
-                var folder = bookmarkContainer.Text is not null
-                    ? await GetStorageProvider().OpenFolderBookmarkAsync(bookmarkContainer.Text)
-                    : null;
-
-                await SetPickerResult(folder is null ? null : new[] { folder });
+////            var results = this.Get<ItemsPresenter>("PickerLastResults");
+////            var resultsVisible = this.Get<TextBlock>("PickerLastResultsVisible");
+////            var bookmarkContainer = this.Get<TextBox>("BookmarkContainer");
+////            var openedFileContent = this.Get<TextBox>("OpenedFileContent");
+////            var openMultiple = this.Get<CheckBox>("OpenMultiple");
+
+////            IStorageFolder? lastSelectedDirectory = null;
+
+////            List<FileDialogFilter> GetFilters()
+////            {
+////                if (this.Get<CheckBox>("UseFilters").IsChecked != true)
+////                    return new List<FileDialogFilter>();
+////                return  new List<FileDialogFilter>
+////                {
+////                    new FileDialogFilter
+////                    {
+////                        Name = "Text files (.txt)", Extensions = new List<string> {"txt"}
+////                    },
+////                    new FileDialogFilter
+////                    {
+////                        Name = "All files",
+////                        Extensions = new List<string> {"*"}
+////                    }
+////                };
+////            }
+
+////            List<FilePickerFileType>? GetFileTypes()
+////            {
+////                if (this.Get<CheckBox>("UseFilters").IsChecked != true)
+////                    return null;
+////                return new List<FilePickerFileType>
+////                {
+////                    FilePickerFileTypes.All,
+////                    FilePickerFileTypes.TextPlain
+////                };
+////            }
+
+////            this.Get<Button>("OpenFile").Click += async delegate
+////            {
+////                // Almost guaranteed to exist
+////                var uri = Assembly.GetEntryAssembly()?.GetModules().FirstOrDefault()?.FullyQualifiedName;
+////                var initialFileName = uri == null ? null : System.IO.Path.GetFileName(uri);
+////                var initialDirectory = uri == null ? null : System.IO.Path.GetDirectoryName(uri);
+
+////                var result = await new OpenFileDialog()
+////                {
+////                    Title = "Open file",
+////                    Filters = GetFilters(),
+////                    Directory = initialDirectory,
+////                    InitialFileName = initialFileName
+////                }.ShowAsync(GetWindow());
+////                results.Items = result;
+////                resultsVisible.IsVisible = result?.Any() == true;
+////            };
+////            this.Get<Button>("OpenMultipleFiles").Click += async delegate
+////            {
+////                var result = await new OpenFileDialog()
+////                {
+////                    Title = "Open multiple files",
+////                    Filters = GetFilters(),
+////                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
+////                    AllowMultiple = true
+////                }.ShowAsync(GetWindow());
+////                results.Items = result;
+////                resultsVisible.IsVisible = result?.Any() == true;
+////            };
+////            this.Get<Button>("SaveFile").Click += async delegate
+////            {
+////                var filters = GetFilters();
+////                var result = await new SaveFileDialog()
+////                {
+////                    Title = "Save file",
+////                    Filters = filters,
+////                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
+////                    DefaultExtension = filters?.Any() == true ? "txt" : null,
+////                    InitialFileName = "test.txt"
+////                }.ShowAsync(GetWindow());
+////                results.Items = new[] { result };
+////                resultsVisible.IsVisible = result != null;
+////            };
+////            this.Get<Button>("SelectFolder").Click += async delegate
+////            {
+////                var result = await new OpenFolderDialog()
+////                {
+////                    Title = "Select folder",
+////                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null
+////                }.ShowAsync(GetWindow());
+////                if (string.IsNullOrEmpty(result))
+////                {
+////                    resultsVisible.IsVisible = false;
+////                }
+////                else
+////                {
+////                    lastSelectedDirectory = new BclStorageFolder(new System.IO.DirectoryInfo(result));
+////                    results.Items = new[] { result };
+////                    resultsVisible.IsVisible = true;
+////                }
+////            };
+////            this.Get<Button>("OpenBoth").Click += async delegate
+////            {
+////                var result = await new OpenFileDialog()
+////                {
+////                    Title = "Select both",
+////                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
+////                    AllowMultiple = true
+////                }.ShowManagedAsync(GetWindow(), new ManagedFileDialogOptions
+////                {
+////                    AllowDirectorySelection = true
+////                });
+////                results.Items = result;
+////                resultsVisible.IsVisible = result?.Any() == true;
+////            };
+////            this.Get<Button>("DecoratedWindow").Click += delegate
+////            {
+////                new DecoratedWindow().Show();
+////            };
+////            this.Get<Button>("DecoratedWindowDialog").Click += delegate
+////            {
+////                _ = new DecoratedWindow().ShowDialog(GetWindow());
+////            };
+////            this.Get<Button>("Dialog").Click += delegate
+////            {
+////                var window = CreateSampleWindow();
+////                window.Height = 200;
+////                _ = window.ShowDialog(GetWindow());
+////            };
+////            this.Get<Button>("DialogNoTaskbar").Click += delegate
+////            {
+////                var window = CreateSampleWindow();
+////                window.Height = 200;
+////                window.ShowInTaskbar = false;
+////                _ = window.ShowDialog(GetWindow());
+////            };
+////            this.Get<Button>("OwnedWindow").Click += delegate
+////            {
+////                var window = CreateSampleWindow();
+
+////                window.Show(GetWindow());
+////            };
+
+////            this.Get<Button>("OwnedWindowNoTaskbar").Click += delegate
+////            {
+////                var window = CreateSampleWindow();
+
+////                window.ShowInTaskbar = false;
+
+////                window.Show(GetWindow());
+////            };
+
+////            this.Get<Button>("OpenFilePicker").Click += async delegate
+////            {
+////                var result = await GetStorageProvider().OpenFilePickerAsync(new FilePickerOpenOptions()
+////                {
+////                    Title = "Open file",
+////                    FileTypeFilter = GetFileTypes(),
+////                    SuggestedStartLocation = lastSelectedDirectory,
+////                    AllowMultiple = openMultiple.IsChecked == true
+////                });
+
+////                await SetPickerResult(result);
+////            };
+////            this.Get<Button>("SaveFilePicker").Click += async delegate
+////            {
+////                var fileTypes = GetFileTypes();
+////                var file = await GetStorageProvider().SaveFilePickerAsync(new FilePickerSaveOptions()
+////                {
+////                    Title = "Save file",
+////                    FileTypeChoices = fileTypes,
+////                    SuggestedStartLocation = lastSelectedDirectory,
+////                    SuggestedFileName = "FileName",
+////                    DefaultExtension = fileTypes?.Any() == true ? "txt" : null,
+////                    ShowOverwritePrompt = false
+////                });
+
+////                if (file is not null && file.CanOpenWrite)
+////                {
+////                    // Sync disposal of StreamWriter is not supported on WASM
+////#if NET6_0_OR_GREATER
+////                    await using var stream = await file.OpenWriteAsync();
+////                    await using var reader = new System.IO.StreamWriter(stream);
+////#else
+////                    using var stream = await file.OpenWriteAsync();
+////                    using var reader = new System.IO.StreamWriter(stream);
+////#endif
+////                    await reader.WriteLineAsync(openedFileContent.Text);
+
+////                    lastSelectedDirectory = await file.GetParentAsync();
+////                }
+
+////                await SetPickerResult(file is null ? null : new [] {file});
+////            };
+////            this.Get<Button>("OpenFolderPicker").Click += async delegate
+////            {
+////                var folders = await GetStorageProvider().OpenFolderPickerAsync(new FolderPickerOpenOptions()
+////                {
+////                    Title = "Folder file",
+////                    SuggestedStartLocation = lastSelectedDirectory,
+////                    AllowMultiple = openMultiple.IsChecked == true
+////                });
+
+////                await SetPickerResult(folders);
+
+////                lastSelectedDirectory = folders.FirstOrDefault();
+////            };
+////            this.Get<Button>("OpenFileFromBookmark").Click += async delegate
+////            {
+////                var file = bookmarkContainer.Text is not null
+////                    ? await GetStorageProvider().OpenFileBookmarkAsync(bookmarkContainer.Text)
+////                    : null;
+
+////                await SetPickerResult(file is null ? null : new[] { file });
+////            };
+////            this.Get<Button>("OpenFolderFromBookmark").Click += async delegate
+////            {
+////                var folder = bookmarkContainer.Text is not null
+////                    ? await GetStorageProvider().OpenFolderBookmarkAsync(bookmarkContainer.Text)
+////                    : null;
+
+////                await SetPickerResult(folder is null ? null : new[] { folder });
                 
-                lastSelectedDirectory = folder;
-            };
-
-            async Task SetPickerResult(IReadOnlyCollection<IStorageItem>? items)
-            {
-                items ??= Array.Empty<IStorageItem>();
-                bookmarkContainer.Text = items.FirstOrDefault(f => f.CanBookmark) is { } f ? await f.SaveBookmarkAsync() : "Can't bookmark";
-                var mappedResults = new List<string>();
-
-                if (items.FirstOrDefault() is IStorageItem item)
-                {
-                    var resultText = item is IStorageFile ? "File:" : "Folder:";
-                    resultText += Environment.NewLine;
-
-                    var props = await item.GetBasicPropertiesAsync();
-                    resultText += @$"Size: {props.Size}
-DateCreated: {props.DateCreated}
-DateModified: {props.DateModified}
-CanBookmark: {item.CanBookmark}
-";
-                    if (item is IStorageFile file)
-                    {
-                        resultText += @$"
-CanOpenRead: {file.CanOpenRead}
-CanOpenWrite: {file.CanOpenWrite}
-Content:
-";
-                        if (file.CanOpenRead)
-                        {
-#if NET6_0_OR_GREATER
-                            await using var stream = await file.OpenReadAsync();
-#else
-                            using var stream = await file.OpenReadAsync();
-#endif
-                            using var reader = new System.IO.StreamReader(stream);
-
-                            // 4GB file test, shouldn't load more than 10000 chars into a memory.
-                            const int length = 10000;
-                            var buffer = ArrayPool<char>.Shared.Rent(length);
-                            try
-                            {
-                                var charsRead = await reader.ReadAsync(buffer, 0, length);
-                                resultText += new string(buffer, 0, charsRead);
-                            }
-                            finally
-                            {
-                                ArrayPool<char>.Shared.Return(buffer);
-                            }
-                        }
-                    }
-
-                    openedFileContent.Text = resultText;
-
-                    lastSelectedDirectory = await item.GetParentAsync();
-                    if (lastSelectedDirectory is not null)
-                    {
-                        mappedResults.Add(FullPathOrName(lastSelectedDirectory));
-                    }
-
-                    foreach (var selectedItem in items)
-                    {
-                        mappedResults.Add("+> " + FullPathOrName(selectedItem));
-                        if (selectedItem is IStorageFolder folder)
-                        {
-                            foreach (var innerItems in await folder.GetItemsAsync())
-                            {
-                                mappedResults.Add("++> " + FullPathOrName(innerItems));
-                            }
-                        }
-                    }
-                }
-
-                results.Items = mappedResults;
-                resultsVisible.IsVisible = mappedResults.Any();
-            }
+////                lastSelectedDirectory = folder;
+////            };
+
+////            async Task SetPickerResult(IReadOnlyCollection<IStorageItem>? items)
+////            {
+////                items ??= Array.Empty<IStorageItem>();
+////                bookmarkContainer.Text = items.FirstOrDefault(f => f.CanBookmark) is { } f ? await f.SaveBookmarkAsync() : "Can't bookmark";
+////                var mappedResults = new List<string>();
+
+////                if (items.FirstOrDefault() is IStorageItem item)
+////                {
+////                    var resultText = item is IStorageFile ? "File:" : "Folder:";
+////                    resultText += Environment.NewLine;
+
+////                    var props = await item.GetBasicPropertiesAsync();
+////                    resultText += @$"Size: {props.Size}
+////DateCreated: {props.DateCreated}
+////DateModified: {props.DateModified}
+////CanBookmark: {item.CanBookmark}
+////";
+////                    if (item is IStorageFile file)
+////                    {
+////                        resultText += @$"
+////CanOpenRead: {file.CanOpenRead}
+////CanOpenWrite: {file.CanOpenWrite}
+////Content:
+////";
+////                        if (file.CanOpenRead)
+////                        {
+////#if NET6_0_OR_GREATER
+////                            await using var stream = await file.OpenReadAsync();
+////#else
+////                            using var stream = await file.OpenReadAsync();
+////#endif
+////                            using var reader = new System.IO.StreamReader(stream);
+
+////                            // 4GB file test, shouldn't load more than 10000 chars into a memory.
+////                            const int length = 10000;
+////                            var buffer = ArrayPool<char>.Shared.Rent(length);
+////                            try
+////                            {
+////                                var charsRead = await reader.ReadAsync(buffer, 0, length);
+////                                resultText += new string(buffer, 0, charsRead);
+////                            }
+////                            finally
+////                            {
+////                                ArrayPool<char>.Shared.Return(buffer);
+////                            }
+////                        }
+////                    }
+
+////                    openedFileContent.Text = resultText;
+
+////                    lastSelectedDirectory = await item.GetParentAsync();
+////                    if (lastSelectedDirectory is not null)
+////                    {
+////                        mappedResults.Add(FullPathOrName(lastSelectedDirectory));
+////                    }
+
+////                    foreach (var selectedItem in items)
+////                    {
+////                        mappedResults.Add("+> " + FullPathOrName(selectedItem));
+////                        if (selectedItem is IStorageFolder folder)
+////                        {
+////                            foreach (var innerItems in await folder.GetItemsAsync())
+////                            {
+////                                mappedResults.Add("++> " + FullPathOrName(innerItems));
+////                            }
+////                        }
+////                    }
+////                }
+
+////                results.Items = mappedResults;
+////                resultsVisible.IsVisible = mappedResults.Any();
+////            }
         }
 
         protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
diff --git a/samples/SampleControls/HamburgerMenu/HamburgerMenu.xaml b/samples/SampleControls/HamburgerMenu/HamburgerMenu.xaml
index f36b79224a2..8bdcf2bb0a7 100644
--- a/samples/SampleControls/HamburgerMenu/HamburgerMenu.xaml
+++ b/samples/SampleControls/HamburgerMenu/HamburgerMenu.xaml
@@ -168,9 +168,7 @@
                               HorizontalScrollBarVisibility="{TemplateBinding (ScrollViewer.HorizontalScrollBarVisibility)}"
                               VerticalScrollBarVisibility="{TemplateBinding (ScrollViewer.VerticalScrollBarVisibility)}">
                   <ItemsPresenter Name="PART_ItemsPresenter"
-                                  HorizontalAlignment="Stretch"
-                                  ItemTemplate="{TemplateBinding ItemTemplate}"
-                                  Items="{TemplateBinding Items}">
+                                  HorizontalAlignment="Stretch">
                     <ItemsPresenter.ItemsPanel>
                       <ItemsPanelTemplate>
                         <StackPanel x:Name="HamburgerItemsPanel"
diff --git a/src/Avalonia.Controls.ColorPicker/Themes/Fluent/ColorView.xaml b/src/Avalonia.Controls.ColorPicker/Themes/Fluent/ColorView.xaml
index f9c4f9b57a4..286ca71bc2f 100644
--- a/src/Avalonia.Controls.ColorPicker/Themes/Fluent/ColorView.xaml
+++ b/src/Avalonia.Controls.ColorPicker/Themes/Fluent/ColorView.xaml
@@ -98,11 +98,8 @@
                         IsScrollChainingEnabled="{TemplateBinding (ScrollViewer.IsScrollChainingEnabled)}"
                         AllowAutoHide="{TemplateBinding (ScrollViewer.AllowAutoHide)}">
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
-                            Margin="{TemplateBinding Padding}"
-                            VirtualizationMode="{TemplateBinding VirtualizationMode}" />
+                            Margin="{TemplateBinding Padding}"/>
           </ScrollViewer>
         </Border>
       </ControlTemplate>
diff --git a/src/Avalonia.Controls.ColorPicker/Themes/Simple/ColorView.xaml b/src/Avalonia.Controls.ColorPicker/Themes/Simple/ColorView.xaml
index 554bca3b63c..556099f56b8 100644
--- a/src/Avalonia.Controls.ColorPicker/Themes/Simple/ColorView.xaml
+++ b/src/Avalonia.Controls.ColorPicker/Themes/Simple/ColorView.xaml
@@ -98,11 +98,8 @@
                         IsScrollChainingEnabled="{TemplateBinding (ScrollViewer.IsScrollChainingEnabled)}"
                         AllowAutoHide="{TemplateBinding (ScrollViewer.AllowAutoHide)}">
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
-                            Margin="{TemplateBinding Padding}"
-                            VirtualizationMode="{TemplateBinding VirtualizationMode}" />
+                            Margin="{TemplateBinding Padding}"/>
           </ScrollViewer>
         </Border>
       </ControlTemplate>
diff --git a/src/Avalonia.Controls/ComboBox.cs b/src/Avalonia.Controls/ComboBox.cs
index f02df2e9c1a..f8b0ebbbce1 100644
--- a/src/Avalonia.Controls/ComboBox.cs
+++ b/src/Avalonia.Controls/ComboBox.cs
@@ -57,7 +57,7 @@ public class ComboBox : SelectingItemsControl
         /// Defines the <see cref="VirtualizationMode"/> property.
         /// </summary>
         public static readonly StyledProperty<ItemVirtualizationMode> VirtualizationModeProperty =
-            ItemsPresenter.VirtualizationModeProperty.AddOwner<ComboBox>();
+            VirtualizingStackPanel.VirtualizationModeProperty.AddOwner<ComboBox>();
 
         /// <summary>
         /// Defines the <see cref="PlaceholderText"/> property.
diff --git a/src/Avalonia.Controls/IVirtualizingPanel.cs b/src/Avalonia.Controls/IVirtualizingPanel.cs
index 9cdbc69cfb9..eff469f37af 100644
--- a/src/Avalonia.Controls/IVirtualizingPanel.cs
+++ b/src/Avalonia.Controls/IVirtualizingPanel.cs
@@ -7,83 +7,5 @@ namespace Avalonia.Controls
     /// </summary>
     public interface IVirtualizingPanel
     {
-        /// <summary>
-        /// Gets the children of the panel.
-        /// </summary>
-        Controls Children { get; }
-
-        /// <summary>
-        /// Gets or sets the controller for the virtualizing panel.
-        /// </summary>
-        /// <remarks>
-        /// A virtualizing controller is responsible for maintaining the controls in the virtualizing
-        /// panel. This property will be set by the controller when virtualization is initialized.
-        /// Note that this property may remain null if the panel is added to a control that does
-        /// not act as a virtualizing controller.
-        /// </remarks>
-        IVirtualizingController? Controller { get; set; }
-
-        /// <summary>
-        /// Gets a value indicating whether the panel is full.
-        /// </summary>
-        /// <remarks>
-        /// This property should return false until enough children are added to fill the space
-        /// passed into the last measure or arrange in the direction of scroll. It should be
-        /// updated immediately after a child is added or removed.
-        /// </remarks>
-        bool IsFull { get; }
-
-        /// <summary>
-        /// Gets the number of items that can be removed while keeping the panel full.
-        /// </summary>
-        /// <remarks>
-        /// This property should return the number of children that are completely out of the
-        /// panel's current bounds in the direction of scroll. It should be updated after an
-        /// arrange.
-        /// </remarks>
-        int OverflowCount { get; }
-
-        /// <summary>
-        /// Gets the direction of scroll.
-        /// </summary>
-        Orientation ScrollDirection { get; }
-
-        /// <summary>
-        /// Gets the average size of the materialized items in the direction of scroll.
-        /// </summary>
-        double AverageItemSize { get; }
-
-        /// <summary>
-        /// Gets or sets a size in pixels by which the content is overflowing the panel, in the
-        /// direction of scroll.
-        /// </summary>
-        /// <remarks>
-        /// This may be non-zero even when <see cref="OverflowCount"/> is zero if the last item
-        /// overflows the panel bounds.
-        /// </remarks>
-        double PixelOverflow { get; }
-
-        /// <summary>
-        /// Gets or sets the current pixel offset of the items in the direction of scroll.
-        /// </summary>
-        double PixelOffset { get; set; }
-
-        /// <summary>
-        /// Gets or sets the current scroll offset in the cross axis.
-        /// </summary>
-        double CrossAxisOffset { get; set; }
-
-        /// <summary>
-        /// Invalidates the measure of the control and forces a call to 
-        /// <see cref="IVirtualizingController.UpdateControls"/> on the next measure.
-        /// </summary>
-        /// <remarks>
-        /// The implementation for this method should call
-        /// <see cref="Layoutable.InvalidateMeasure"/> and also ensure that the next call to
-        /// <see cref="Layoutable.Measure(Size)"/> calls
-        /// <see cref="IVirtualizingController.UpdateControls"/> on the next measure even if
-        /// the available size hasn't changed.
-        /// </remarks>
-        void ForceInvalidateMeasure();
     }
 }
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index e6c3d67bf46..e51296cdecf 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -174,7 +174,7 @@ public IDataTemplate? ItemTemplate
         /// <summary>
         /// Gets the items presenter control.
         /// </summary>
-        public IItemsPresenter? Presenter
+        public ItemsPresenter? Presenter
         {
             get;
             protected set;
@@ -189,7 +189,7 @@ event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexCh
         }
 
         /// <inheritdoc/>
-        void IItemsPresenterHost.RegisterItemsPresenter(IItemsPresenter presenter)
+        void IItemsPresenterHost.RegisterItemsPresenter(ItemsPresenter presenter)
         {
             if (Presenter is IChildIndexProvider oldInnerProvider)
             {
@@ -408,12 +408,6 @@ protected virtual void ItemsChanged(AvaloniaPropertyChangedEventArgs e)
             UpdateItemCount();
             RemoveControlItemsFromLogicalChildren(oldValue);
             AddControlItemsToLogicalChildren(newValue);
-
-            if (Presenter != null)
-            {
-                Presenter.Items = newValue;
-            }
-
             SubscribeToItems(newValue);
         }
 
@@ -437,8 +431,6 @@ protected virtual void ItemsCollectionChanged(object sender, NotifyCollectionCha
                     RemoveControlItemsFromLogicalChildren(e.OldItems);
                     break;
             }
-
-            Presenter?.ItemsChanged(e);
         }
 
         /// <summary>
diff --git a/src/Avalonia.Controls/ListBox.cs b/src/Avalonia.Controls/ListBox.cs
index 7e5981688ce..0adc8a61ba9 100644
--- a/src/Avalonia.Controls/ListBox.cs
+++ b/src/Avalonia.Controls/ListBox.cs
@@ -51,7 +51,7 @@ public class ListBox : SelectingItemsControl
         /// Defines the <see cref="VirtualizationMode"/> property.
         /// </summary>
         public static readonly StyledProperty<ItemVirtualizationMode> VirtualizationModeProperty =
-            ItemsPresenter.VirtualizationModeProperty.AddOwner<ListBox>();
+            VirtualizingStackPanel.VirtualizationModeProperty.AddOwner<ListBox>();
 
         private IScrollable? _scroll;
 
diff --git a/src/Avalonia.Controls/Presenters/CarouselPresenter.cs b/src/Avalonia.Controls/Presenters/CarouselPresenter.cs
index 7b435e287db..d5b89a1bdc1 100644
--- a/src/Avalonia.Controls/Presenters/CarouselPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/CarouselPresenter.cs
@@ -12,7 +12,7 @@ namespace Avalonia.Controls.Presenters
     /// <summary>
     /// Displays pages inside an <see cref="ItemsControl"/>.
     /// </summary>
-    public class CarouselPresenter : ItemsPresenterBase
+    public class CarouselPresenter : ItemsPresenter
     {
         /// <summary>
         /// Defines the <see cref="IsVirtualized"/> property.
@@ -43,8 +43,8 @@ public class CarouselPresenter : ItemsPresenterBase
         /// </summary>
         static CarouselPresenter()
         {
-            IsVirtualizedProperty.Changed.AddClassHandler<CarouselPresenter>((x, e) => x.IsVirtualizedChanged(e));
-            SelectedIndexProperty.Changed.AddClassHandler<CarouselPresenter>((x, e) => x.SelectedIndexChanged(e));
+            ////IsVirtualizedProperty.Changed.AddClassHandler<CarouselPresenter>((x, e) => x.IsVirtualizedChanged(e));
+            ////SelectedIndexProperty.Changed.AddClassHandler<CarouselPresenter>((x, e) => x.SelectedIndexChanged(e));
         }
 
         /// <summary>
@@ -71,14 +71,14 @@ public int SelectedIndex
 
             set
             {
-                var old = SelectedIndex;
-                var effective = (value >= 0 && value < Items?.Cast<object>().Count()) ? value : -1;
+                ////var old = SelectedIndex;
+                ////var effective = (value >= 0 && value < Items?.Cast<object>().Count()) ? value : -1;
 
-                if (old != effective)
-                {
-                    _selectedIndex = effective;
-                    RaisePropertyChanged(SelectedIndexProperty, old, effective, BindingPriority.LocalValue);
-                }
+                ////if (old != effective)
+                ////{
+                ////    _selectedIndex = effective;
+                ////    RaisePropertyChanged(SelectedIndexProperty, old, effective, BindingPriority.LocalValue);
+                ////}
             }
         }
 
@@ -92,185 +92,185 @@ public IPageTransition? PageTransition
         }
 
         /// <inheritdoc/>
-        protected override void ItemsChanged(NotifyCollectionChangedEventArgs e)
-        {
-            if (!IsVirtualized)
-            {
-                base.ItemsChanged(e);
+        ////protected override void ItemsChanged(NotifyCollectionChangedEventArgs e)
+        ////{
+        ////    if (!IsVirtualized)
+        ////    {
+        ////        base.ItemsChanged(e);
 
-                if (Items == null || SelectedIndex >= Items.Count())
-                {
-                    SelectedIndex = Items.Count() - 1;
-                }
+        ////        if (Items == null || SelectedIndex >= Items.Count())
+        ////        {
+        ////            SelectedIndex = Items.Count() - 1;
+        ////        }
 
-                foreach (var c in ItemContainerGenerator.Containers)
-                {
-                    c.ContainerControl.IsVisible = c.Index == SelectedIndex;
-                }
-            }
-            else if (SelectedIndex != -1 && Panel != null)
-            {
-                switch (e.Action)
-                {
-                    case NotifyCollectionChangedAction.Add:
-                        if (e.NewStartingIndex > SelectedIndex)
-                        {
-                            return;
-                        }
-                        break;
-                    case NotifyCollectionChangedAction.Remove:
-                        if (e.OldStartingIndex > SelectedIndex)
-                        {
-                            return;
-                        }
-                        break;
-                    case NotifyCollectionChangedAction.Replace:
-                        if (e.OldStartingIndex > SelectedIndex ||
-                            e.OldStartingIndex + e.OldItems!.Count - 1 < SelectedIndex)
-                        {
-                            return;
-                        }
-                        break;
-                    case NotifyCollectionChangedAction.Move:
-                        if (e.OldStartingIndex > SelectedIndex &&
-                            e.NewStartingIndex > SelectedIndex)
-                        {
-                            return;
-                        }
-                        break;
-                }
+        ////        foreach (var c in ItemContainerGenerator.Containers)
+        ////        {
+        ////            c.ContainerControl.IsVisible = c.Index == SelectedIndex;
+        ////        }
+        ////    }
+        ////    else if (SelectedIndex != -1 && Panel != null)
+        ////    {
+        ////        switch (e.Action)
+        ////        {
+        ////            case NotifyCollectionChangedAction.Add:
+        ////                if (e.NewStartingIndex > SelectedIndex)
+        ////                {
+        ////                    return;
+        ////                }
+        ////                break;
+        ////            case NotifyCollectionChangedAction.Remove:
+        ////                if (e.OldStartingIndex > SelectedIndex)
+        ////                {
+        ////                    return;
+        ////                }
+        ////                break;
+        ////            case NotifyCollectionChangedAction.Replace:
+        ////                if (e.OldStartingIndex > SelectedIndex ||
+        ////                    e.OldStartingIndex + e.OldItems!.Count - 1 < SelectedIndex)
+        ////                {
+        ////                    return;
+        ////                }
+        ////                break;
+        ////            case NotifyCollectionChangedAction.Move:
+        ////                if (e.OldStartingIndex > SelectedIndex &&
+        ////                    e.NewStartingIndex > SelectedIndex)
+        ////                {
+        ////                    return;
+        ////                }
+        ////                break;
+        ////        }
 
-                if (Items == null || SelectedIndex >= Items.Count())
-                {
-                    SelectedIndex = Items.Count() - 1;
-                }
+        ////        if (Items == null || SelectedIndex >= Items.Count())
+        ////        {
+        ////            SelectedIndex = Items.Count() - 1;
+        ////        }
 
-                Panel.Children.Clear();
-                ItemContainerGenerator.Clear();
+        ////        Panel.Children.Clear();
+        ////        ItemContainerGenerator.Clear();
 
-                if (SelectedIndex != -1)
-                {
-                    GetOrCreateContainer(SelectedIndex);
-                }
-            }
-        }
+        ////        if (SelectedIndex != -1)
+        ////        {
+        ////            GetOrCreateContainer(SelectedIndex);
+        ////        }
+        ////    }
+        ////}
 
-        protected override void PanelCreated(Panel panel)
-        {
-            ItemsChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
-        }
+        ////protected override void PanelCreated(Panel panel)
+        ////{
+        ////    ItemsChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        ////}
 
-        /// <summary>
-        /// Moves to the selected page, animating if a <see cref="PageTransition"/> is set.
-        /// </summary>
-        /// <param name="fromIndex">The index of the old page.</param>
-        /// <param name="toIndex">The index of the new page.</param>
-        /// <returns>A task tracking the animation.</returns>
-        private async Task MoveToPage(int fromIndex, int toIndex)
-        {
-            if (fromIndex != toIndex)
-            {
-                var generator = ItemContainerGenerator;
-                Control? from = null;
-                Control? to = null;
+        /////// <summary>
+        /////// Moves to the selected page, animating if a <see cref="PageTransition"/> is set.
+        /////// </summary>
+        /////// <param name="fromIndex">The index of the old page.</param>
+        /////// <param name="toIndex">The index of the new page.</param>
+        /////// <returns>A task tracking the animation.</returns>
+        ////private async Task MoveToPage(int fromIndex, int toIndex)
+        ////{
+        ////    if (fromIndex != toIndex)
+        ////    {
+        ////        var generator = ItemContainerGenerator;
+        ////        Control? from = null;
+        ////        Control? to = null;
 
-                if (fromIndex != -1)
-                {
-                    from = generator.ContainerFromIndex(fromIndex);
-                }
+        ////        if (fromIndex != -1)
+        ////        {
+        ////            from = generator.ContainerFromIndex(fromIndex);
+        ////        }
 
-                if (toIndex != -1)
-                {
-                    to = GetOrCreateContainer(toIndex);
-                }
+        ////        if (toIndex != -1)
+        ////        {
+        ////            to = GetOrCreateContainer(toIndex);
+        ////        }
 
-                if (PageTransition != null && (from != null || to != null))
-                {
-                    await PageTransition.Start((Visual?)from, (Visual?)to, fromIndex < toIndex, default);
-                }
-                else if (to != null)
-                {
-                    to.IsVisible = true;
-                }
+        ////        if (PageTransition != null && (from != null || to != null))
+        ////        {
+        ////            await PageTransition.Start((Visual?)from, (Visual?)to, fromIndex < toIndex, default);
+        ////        }
+        ////        else if (to != null)
+        ////        {
+        ////            to.IsVisible = true;
+        ////        }
 
-                if (from != null)
-                {
-                    if (IsVirtualized)
-                    {
-                        Panel!.Children.Remove(from);
-                        generator.Dematerialize(fromIndex, 1);
-                    }
-                    else
-                    {
-                        from.IsVisible = false;
-                    }
-                }
-            }
-        }
+        ////        if (from != null)
+        ////        {
+        ////            if (IsVirtualized)
+        ////            {
+        ////                Panel!.Children.Remove(from);
+        ////                generator.Dematerialize(fromIndex, 1);
+        ////            }
+        ////            else
+        ////            {
+        ////                from.IsVisible = false;
+        ////            }
+        ////        }
+        ////    }
+        ////}
 
-        private Control? GetOrCreateContainer(int index)
-        {
-            var container = ItemContainerGenerator.ContainerFromIndex(index);
+        ////private Control? GetOrCreateContainer(int index)
+        ////{
+        ////    var container = ItemContainerGenerator.ContainerFromIndex(index);
 
-            if (container == null && IsVirtualized)
-            {
-                var item = Items!.Cast<object>().ElementAt(index);
-                var materialized = ItemContainerGenerator.Materialize(index, item);
-                Panel!.Children.Add(materialized.ContainerControl);
-                container = materialized.ContainerControl;
-            }
+        ////    if (container == null && IsVirtualized)
+        ////    {
+        ////        var item = Items!.Cast<object>().ElementAt(index);
+        ////        var materialized = ItemContainerGenerator.Materialize(index, item);
+        ////        Panel!.Children.Add(materialized.ContainerControl);
+        ////        container = materialized.ContainerControl;
+        ////    }
 
-            return container;
-        }
+        ////    return container;
+        ////}
 
-        /// <summary>
-        /// Called when the <see cref="IsVirtualized"/> property changes.
-        /// </summary>
-        /// <param name="e">The event args.</param>
-        private void IsVirtualizedChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            if (Panel != null)
-            {
-                ItemsChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
-            }
-        }
+        /////// <summary>
+        /////// Called when the <see cref="IsVirtualized"/> property changes.
+        /////// </summary>
+        /////// <param name="e">The event args.</param>
+        ////private void IsVirtualizedChanged(AvaloniaPropertyChangedEventArgs e)
+        ////{
+        ////    if (Panel != null)
+        ////    {
+        ////        ItemsChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        ////    }
+        ////}
 
-        /// <summary>
-        /// Called when the <see cref="SelectedIndex"/> property changes.
-        /// </summary>
-        /// <param name="e">The event args.</param>
-        private async void SelectedIndexChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            if (Panel != null)
-            {
-                if (_currentTransition == null)
-                {
-                    int fromIndex = (int)e.OldValue!;
-                    int toIndex = (int)e.NewValue!;
+        /////// <summary>
+        /////// Called when the <see cref="SelectedIndex"/> property changes.
+        /////// </summary>
+        /////// <param name="e">The event args.</param>
+        ////private async void SelectedIndexChanged(AvaloniaPropertyChangedEventArgs e)
+        ////{
+        ////    if (Panel != null)
+        ////    {
+        ////        if (_currentTransition == null)
+        ////        {
+        ////            int fromIndex = (int)e.OldValue!;
+        ////            int toIndex = (int)e.NewValue!;
 
-                    for (;;)
-                    {
-                        _currentTransition = MoveToPage(fromIndex, toIndex);
-                        await _currentTransition;
+        ////            for (;;)
+        ////            {
+        ////                _currentTransition = MoveToPage(fromIndex, toIndex);
+        ////                await _currentTransition;
 
-                        if (_queuedTransitionIndex != -1)
-                        {
-                            fromIndex = toIndex;
-                            toIndex = _queuedTransitionIndex;
-                            _queuedTransitionIndex = -1;
-                        }
-                        else
-                        {
-                            _currentTransition = null;
-                            break;
-                        }
-                    }
-                }
-                else
-                {
-                    _queuedTransitionIndex = (int)e.NewValue!;
-                }
-            }
-        }
+        ////                if (_queuedTransitionIndex != -1)
+        ////                {
+        ////                    fromIndex = toIndex;
+        ////                    toIndex = _queuedTransitionIndex;
+        ////                    _queuedTransitionIndex = -1;
+        ////                }
+        ////                else
+        ////                {
+        ////                    _currentTransition = null;
+        ////                    break;
+        ////                }
+        ////            }
+        ////        }
+        ////        else
+        ////        {
+        ////            _queuedTransitionIndex = (int)e.NewValue!;
+        ////        }
+        ////    }
+        ////}
     }
 }
diff --git a/src/Avalonia.Controls/Presenters/IItemsPresenter.cs b/src/Avalonia.Controls/Presenters/IItemsPresenter.cs
deleted file mode 100644
index dea8d4960e7..00000000000
--- a/src/Avalonia.Controls/Presenters/IItemsPresenter.cs
+++ /dev/null
@@ -1,18 +0,0 @@
-using System.Collections;
-using System.Collections.Specialized;
-using Avalonia.Metadata;
-
-namespace Avalonia.Controls.Presenters
-{
-    [NotClientImplementable]
-    public interface IItemsPresenter : IPresenter
-    {
-        IEnumerable? Items { get; set; }
-
-        Panel? Panel { get; }
-
-        void ItemsChanged(NotifyCollectionChangedEventArgs e);
-
-        void ScrollIntoView(int index);
-    }
-}
diff --git a/src/Avalonia.Controls/Presenters/IItemsPresenterHost.cs b/src/Avalonia.Controls/Presenters/IItemsPresenterHost.cs
index a73d2abb5f6..8bf190dbda7 100644
--- a/src/Avalonia.Controls/Presenters/IItemsPresenterHost.cs
+++ b/src/Avalonia.Controls/Presenters/IItemsPresenterHost.cs
@@ -18,9 +18,9 @@ namespace Avalonia.Controls.Presenters
     public interface IItemsPresenterHost
     {
         /// <summary>
-        /// Registers an <see cref="IItemsPresenter"/> with a host control.
+        /// Registers an <see cref="ItemsPresenter"/> with a host control.
         /// </summary>
         /// <param name="presenter">The items presenter.</param>
-        void RegisterItemsPresenter(IItemsPresenter presenter);
+        void RegisterItemsPresenter(ItemsPresenter presenter);
     }
 }
diff --git a/src/Avalonia.Controls/Presenters/ItemContainerSync.cs b/src/Avalonia.Controls/Presenters/ItemContainerSync.cs
deleted file mode 100644
index 7346a074f30..00000000000
--- a/src/Avalonia.Controls/Presenters/ItemContainerSync.cs
+++ /dev/null
@@ -1,125 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Collections.Specialized;
-using Avalonia.Controls.Generators;
-using Avalonia.Controls.Utils;
-
-namespace Avalonia.Controls.Presenters
-{
-    internal static class ItemContainerSync
-    {
-        public static void ItemsChanged(
-            ItemsPresenterBase owner,
-            IEnumerable? items,
-            NotifyCollectionChangedEventArgs e)
-        {
-            var generator = owner.ItemContainerGenerator;
-            var panel = owner.Panel;
-
-            if (panel == null)
-            {
-                return;
-            }
-
-            void Add()
-            {
-                if (e.NewStartingIndex + e.NewItems!.Count < items!.Count())
-                {
-                    generator.InsertSpace(e.NewStartingIndex, e.NewItems.Count);
-                }
-
-                AddContainers(owner, e.NewStartingIndex, e.NewItems);
-            }
-
-            void Remove()
-            {
-                RemoveContainers(panel, generator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count));
-            }
-
-            switch (e.Action)
-            {
-                case NotifyCollectionChangedAction.Add:
-                    Add();
-                    break;
-
-                case NotifyCollectionChangedAction.Remove:
-                    Remove();
-                    break;
-
-                case NotifyCollectionChangedAction.Replace:
-                    RemoveContainers(panel, generator.Dematerialize(e.OldStartingIndex, e.OldItems!.Count));
-                    var containers = AddContainers(owner, e.NewStartingIndex, e.NewItems!);
-
-                    var i = e.NewStartingIndex;
-
-                    foreach (var container in containers)
-                    {
-                        panel.Children[i++] = container.ContainerControl;
-                    }
-
-                    break;
-
-                case NotifyCollectionChangedAction.Move:
-                    Remove();
-                    Add();
-                    break;
-
-                case NotifyCollectionChangedAction.Reset:
-                    RemoveContainers(panel, generator.Clear());
-
-                    if (items != null)
-                    {
-                        AddContainers(owner, 0, items);
-                    }
-
-                    break;
-            }
-        }
-
-        private static IList<ItemContainerInfo> AddContainers(
-            ItemsPresenterBase owner,
-            int index,
-            IEnumerable items)
-        {
-            var generator = owner.ItemContainerGenerator;
-            var result = new List<ItemContainerInfo>();
-            var panel = owner.Panel;
-
-            foreach (var item in items)
-            {
-                var i = generator.Materialize(index++, item);
-
-                if (i.ContainerControl != null)
-                {
-                    if (i.Index < panel!.Children.Count)
-                    {
-                        // TODO: This will insert at the wrong place when there are null items.
-                        panel.Children.Insert(i.Index, i.ContainerControl);
-                    }
-                    else
-                    {
-                        panel.Children.Add(i.ContainerControl);
-                    }
-                }
-
-                result.Add(i);
-            }
-
-            return result;
-        }
-
-        private static void RemoveContainers(
-            Panel panel,
-            IEnumerable<ItemContainerInfo> items)
-        {
-            foreach (var i in items)
-            {
-                if (i.ContainerControl != null)
-                {
-                    panel.Children.Remove(i.ContainerControl);
-                }
-            }
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Presenters/ItemVirtualizer.cs b/src/Avalonia.Controls/Presenters/ItemVirtualizer.cs
deleted file mode 100644
index 1f0f2a2f67f..00000000000
--- a/src/Avalonia.Controls/Presenters/ItemVirtualizer.cs
+++ /dev/null
@@ -1,303 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Specialized;
-using System.Reactive.Linq;
-using Avalonia.Controls.Primitives;
-using Avalonia.Controls.Utils;
-using Avalonia.Input;
-using Avalonia.Layout;
-using Avalonia.VisualTree;
-
-namespace Avalonia.Controls.Presenters
-{
-    /// <summary>
-    /// Base class for classes which handle virtualization for an <see cref="ItemsPresenter"/>.
-    /// </summary>
-    internal abstract class ItemVirtualizer : IVirtualizingController, IDisposable
-    {
-        private double _crossAxisOffset;
-        private IDisposable? _subscriptions;
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ItemVirtualizer"/> class.
-        /// </summary>
-        /// <param name="owner"></param>
-        public ItemVirtualizer(ItemsPresenter owner)
-        {
-            Owner = owner;
-            Items = owner.Items;
-            ItemCount = owner.Items.Count();
-
-            var panel = VirtualizingPanel;
-
-            if (panel != null)
-            {
-                _subscriptions = ((AvaloniaObject)panel).GetObservable(Panel.BoundsProperty)
-                    .Skip(1)
-                    .Subscribe(_ => InvalidateScroll());
-            }
-        }
-
-        /// <summary>
-        /// Gets the <see cref="ItemsPresenter"/> which owns the virtualizer.
-        /// </summary>
-        public ItemsPresenter Owner { get; }
-
-        /// <summary>
-        /// Gets the <see cref="IVirtualizingPanel"/> which will host the items.
-        /// </summary>
-        public IVirtualizingPanel? VirtualizingPanel => Owner.Panel as IVirtualizingPanel;
-
-        /// <summary>
-        /// Gets the items to display.
-        /// </summary>
-        public IEnumerable? Items { get; private set; }
-
-        /// <summary>
-        /// Gets the number of items in <see cref="Items"/>.
-        /// </summary>
-        public int ItemCount { get; private set; }
-
-        /// <summary>
-        /// Gets or sets the index of the first item displayed in the panel.
-        /// </summary>
-        public int FirstIndex { get; protected set; }
-
-        /// <summary>
-        /// Gets or sets the index of the first item beyond those displayed in the panel.
-        /// </summary>
-        public int NextIndex { get; protected set; }
-
-        /// <summary>
-        /// Gets a value indicating whether the items should be scroll horizontally or vertically.
-        /// </summary>
-        public bool Vertical => VirtualizingPanel?.ScrollDirection == Orientation.Vertical;
-
-        /// <summary>
-        /// Gets a value indicating whether logical scrolling is enabled.
-        /// </summary>
-        public abstract bool IsLogicalScrollEnabled { get; }
-
-        /// <summary>
-        /// Gets the value of the scroll extent.
-        /// </summary>
-        public abstract double ExtentValue { get; }
-
-        /// <summary>
-        /// Gets or sets the value of the current scroll offset.
-        /// </summary>
-        public abstract double OffsetValue { get; set; }
-
-        /// <summary>
-        /// Gets the value of the scrollable viewport.
-        /// </summary>
-        public abstract double ViewportValue { get; }
-
-        /// <summary>
-        /// Gets the <see cref="ExtentValue"/> as a <see cref="Size"/>.
-        /// </summary>
-        public Size Extent
-        {
-            get
-            {
-                if (IsLogicalScrollEnabled && Owner.Panel is Panel panel)
-                {
-                    return Vertical ?
-                        new Size(panel.DesiredSize.Width, ExtentValue) :
-                        new Size(ExtentValue, panel.DesiredSize.Height);
-                }
-
-                return default;
-            }
-        }
-
-        /// <summary>
-        /// Gets the <see cref="ViewportValue"/> as a <see cref="Size"/>.
-        /// </summary>
-        public Size Viewport
-        {
-            get
-            {
-                if (IsLogicalScrollEnabled && Owner.Panel is Panel panel)
-                {
-                    return Vertical ?
-                        new Size(panel.Bounds.Width, ViewportValue) :
-                        new Size(ViewportValue, panel.Bounds.Height);
-                }
-
-                return default;
-            }
-        }
-
-        /// <summary>
-        /// Gets or sets the <see cref="OffsetValue"/> as a <see cref="Vector"/>.
-        /// </summary>
-        public Vector Offset
-        {
-            get
-            {
-                if (IsLogicalScrollEnabled)
-                {
-                    return Vertical ? new Vector(_crossAxisOffset, OffsetValue) : new Vector(OffsetValue, _crossAxisOffset);
-                }
-
-                return default;
-            }
-
-            set
-            {
-                if (!IsLogicalScrollEnabled)
-                {
-                    throw new NotSupportedException("Logical scrolling disabled.");
-                }
-
-                var oldCrossAxisOffset = _crossAxisOffset;
-
-                if (Vertical)
-                {
-                    OffsetValue = value.Y;
-                    _crossAxisOffset = value.X;
-                }
-                else
-                {
-                    OffsetValue = value.X;
-                    _crossAxisOffset = value.Y;
-                }
-
-                if (_crossAxisOffset != oldCrossAxisOffset)
-                {
-                    Owner.InvalidateArrange();
-                }
-            }
-        }
-        
-        /// <summary>
-        /// Creates an <see cref="ItemVirtualizer"/> based on an item presenter's 
-        /// <see cref="ItemVirtualizationMode"/>.
-        /// </summary>
-        /// <param name="owner">The items presenter.</param>
-        /// <returns>An <see cref="ItemVirtualizer"/>.</returns>
-        public static ItemVirtualizer? Create(ItemsPresenter owner)
-        {
-            if (owner.Panel == null)
-            {
-                return null;
-            }
-
-            var virtualizingPanel = owner.Panel as IVirtualizingPanel;
-            var scrollContentPresenter = owner.Parent as IScrollable;
-            ItemVirtualizer? result = null;
-
-            if (virtualizingPanel != null && scrollContentPresenter is object)
-            {
-                switch (owner.VirtualizationMode)
-                {
-                    case ItemVirtualizationMode.Simple:
-                        result = new ItemVirtualizerSimple(owner);
-                        break;
-                }
-            }
-
-            if (result == null)
-            {
-                result = new ItemVirtualizerNone(owner);
-            }
-
-            if (virtualizingPanel != null)
-            {
-                virtualizingPanel.Controller = result;
-            }
-
-            return result;
-        }
-
-        /// <summary>
-        /// Carries out a measure for the related <see cref="ItemsPresenter"/>.
-        /// </summary>
-        /// <param name="availableSize">The size available to the control.</param>
-        /// <returns>The desired size for the control.</returns>
-        public virtual Size MeasureOverride(Size availableSize)
-        {
-            Owner.Panel!.Measure(availableSize);
-            return Owner.Panel.DesiredSize;
-        }
-
-        /// <summary>
-        /// Carries out an arrange for the related <see cref="ItemsPresenter"/>.
-        /// </summary>
-        /// <param name="finalSize">The size available to the control.</param>
-        /// <returns>The actual size used.</returns>
-        public virtual Size ArrangeOverride(Size finalSize)
-        {
-            if (VirtualizingPanel != null)
-            {
-                VirtualizingPanel.CrossAxisOffset = _crossAxisOffset;
-                Owner.Panel!.Arrange(new Rect(finalSize));
-            }
-            else
-            {
-                var origin = Vertical ? new Point(-_crossAxisOffset, 0) : new Point(0, _crossAxisOffset);
-                Owner.Panel!.Arrange(new Rect(origin, finalSize));
-            }
-
-            return finalSize;
-        }
-
-        /// <inheritdoc/>
-        public virtual void UpdateControls()
-        {
-        }
-
-        /// <summary>
-        /// Gets the next control in the specified direction.
-        /// </summary>
-        /// <param name="direction">The movement direction.</param>
-        /// <param name="from">The control from which movement begins.</param>
-        /// <returns>The control.</returns>
-        public virtual Control? GetControlInDirection(NavigationDirection direction, Control? from)
-        {
-            return null;
-        }
-
-        /// <summary>
-        /// Called when the items for the presenter change, either because 
-        /// <see cref="ItemsPresenterBase.Items"/> has been set, the items collection has been
-        /// modified, or the panel has been created.
-        /// </summary>
-        /// <param name="items">The items.</param>
-        /// <param name="e">A description of the change.</param>
-        public virtual void ItemsChanged(IEnumerable? items, NotifyCollectionChangedEventArgs e)
-        {
-            Items = items;
-            ItemCount = items?.Count() ?? 0;
-        }
-
-        /// <summary>
-        /// Scrolls the specified item into view.
-        /// </summary>
-        /// <param name="index">The index of the item.</param>
-        public virtual void ScrollIntoView(int index)
-        {
-        }
-
-        /// <inheritdoc/>
-        public virtual void Dispose()
-        {
-            _subscriptions?.Dispose();
-            _subscriptions = null;
-
-            if (VirtualizingPanel != null)
-            {
-                VirtualizingPanel.Controller = null;
-                VirtualizingPanel.Children.Clear();
-            }
-
-            Owner.ItemContainerGenerator.Clear();
-        }
-
-        /// <summary>
-        /// Invalidates the current scroll.
-        /// </summary>
-        protected void InvalidateScroll() => ((ILogicalScrollable)Owner).RaiseScrollInvalidated(EventArgs.Empty);
-    }
-}
diff --git a/src/Avalonia.Controls/Presenters/ItemVirtualizerNone.cs b/src/Avalonia.Controls/Presenters/ItemVirtualizerNone.cs
deleted file mode 100644
index c1b6842b88c..00000000000
--- a/src/Avalonia.Controls/Presenters/ItemVirtualizerNone.cs
+++ /dev/null
@@ -1,106 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Collections.Specialized;
-using Avalonia.Controls.Generators;
-using Avalonia.Controls.Utils;
-
-namespace Avalonia.Controls.Presenters
-{
-    /// <summary>
-    /// Represents an item virtualizer for an <see cref="ItemsPresenter"/> that doesn't actually
-    /// virtualize items - it just creates a container for every item.
-    /// </summary>
-    internal class ItemVirtualizerNone : ItemVirtualizer
-    {
-        public ItemVirtualizerNone(ItemsPresenter owner)
-            : base(owner)
-        {
-            if (Items != null && owner.Panel != null)
-            {
-                AddContainers(0, Items);
-            }
-        }
-
-        /// <inheritdoc/>
-        public override bool IsLogicalScrollEnabled => false;
-
-        /// <summary>
-        /// This property should never be accessed because <see cref="IsLogicalScrollEnabled"/> is
-        /// false.
-        /// </summary>
-        public override double ExtentValue
-        {
-            get { throw new NotSupportedException(); }
-        }
-
-        /// <summary>
-        /// This property should never be accessed because <see cref="IsLogicalScrollEnabled"/> is
-        /// false.
-        /// </summary>
-        public override double OffsetValue
-        {
-            get { throw new NotSupportedException(); }
-            set { throw new NotSupportedException(); }
-        }
-
-        /// <summary>
-        /// This property should never be accessed because <see cref="IsLogicalScrollEnabled"/> is
-        /// false.
-        /// </summary>
-        public override double ViewportValue
-        {
-            get { throw new NotSupportedException(); }
-        }
-
-        /// <inheritdoc/>
-        public override void ItemsChanged(IEnumerable? items, NotifyCollectionChangedEventArgs e)
-        {
-            base.ItemsChanged(items, e);
-            ItemContainerSync.ItemsChanged(Owner, items, e);
-            Owner.InvalidateMeasure();
-        }
-
-        /// <summary>
-        /// Scrolls the specified item into view.
-        /// </summary>
-        /// <param name="index">The index of the item.</param>
-        public override void ScrollIntoView(int index)
-        {
-            if (index != -1)
-            {
-                var container = Owner.ItemContainerGenerator.ContainerFromIndex(index);
-                container?.BringIntoView();
-            }
-        }
-
-        private IList<ItemContainerInfo> AddContainers(int index, IEnumerable items)
-        {
-            var generator = Owner.ItemContainerGenerator;
-            var result = new List<ItemContainerInfo>();
-            var panel = Owner.Panel;
-
-            foreach (var item in items)
-            {
-                var i = generator.Materialize(index++, item);
-
-                if (i.ContainerControl != null)
-                {
-                    if (i.Index < panel!.Children.Count)
-                    {
-                        // TODO: This will insert at the wrong place when there are null items.
-                        panel.Children.Insert(i.Index, i.ContainerControl);
-                    }
-                    else
-                    {
-                        panel.Children.Add(i.ContainerControl);
-                    }
-                }
-
-                result.Add(i);
-            }
-
-            return result;
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Presenters/ItemVirtualizerSimple.cs b/src/Avalonia.Controls/Presenters/ItemVirtualizerSimple.cs
deleted file mode 100644
index f010c46c1ab..00000000000
--- a/src/Avalonia.Controls/Presenters/ItemVirtualizerSimple.cs
+++ /dev/null
@@ -1,606 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Specialized;
-using System.Linq;
-using Avalonia.Controls.Primitives;
-using Avalonia.Controls.Utils;
-using Avalonia.Input;
-using Avalonia.Layout;
-using Avalonia.Utilities;
-using Avalonia.VisualTree;
-
-namespace Avalonia.Controls.Presenters
-{
-    /// <summary>
-    /// Handles virtualization in an <see cref="ItemsPresenter"/> for
-    /// <see cref="ItemVirtualizationMode.Simple"/>.
-    /// </summary>
-    internal class ItemVirtualizerSimple : ItemVirtualizer
-    {
-        private int _anchor;
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ItemVirtualizerSimple"/> class.
-        /// </summary>
-        /// <param name="owner"></param>
-        public ItemVirtualizerSimple(ItemsPresenter owner)
-            : base(owner)
-        {
-            // Don't need to add children here as UpdateControls should be called by the panel
-            // measure/arrange.
-        }
-
-        /// <inheritdoc/>
-        public override bool IsLogicalScrollEnabled => true;
-
-        /// <inheritdoc/>
-        public override double ExtentValue => ItemCount;
-
-        /// <inheritdoc/>
-        public override double OffsetValue
-        {
-            get
-            {
-                var offset = VirtualizingPanel.PixelOffset > 0 ? 1 : 0;
-                return FirstIndex + offset;
-            }
-
-            set
-            {
-                var panel = VirtualizingPanel;
-                var offset = VirtualizingPanel.PixelOffset > 0 ? 1 : 0;
-                var delta = (int)(value - (FirstIndex + offset));
-
-                if (delta != 0)
-                {
-                    var newLastIndex = (NextIndex - 1) + delta;
-
-                    if (newLastIndex < ItemCount)
-                    {
-                        if (panel.PixelOffset > 0)
-                        {
-                            panel.PixelOffset = 0;
-                            delta += 1;
-                        }
-
-                        if (delta != 0)
-                        {
-                            RecycleContainersForMove(delta);
-                        }
-                    }
-                    else
-                    {
-                        // We're moving to a partially obscured item at the end of the list so
-                        // offset the panel by the height of the first item.
-                        var firstIndex = ItemCount - panel.Children.Count;
-                        RecycleContainersForMove(firstIndex - FirstIndex);
-
-                        double pixelOffset;
-                        var child = panel.Children[0];
-
-                        if (child.IsArrangeValid)
-                        {
-                            pixelOffset = VirtualizingPanel.ScrollDirection == Orientation.Vertical ?
-                                                    child.Bounds.Height :
-                                                    child.Bounds.Width;
-                        }
-                        else
-                        {
-                            pixelOffset = VirtualizingPanel.ScrollDirection == Orientation.Vertical ?
-                                                    child.DesiredSize.Height :
-                                                    child.DesiredSize.Width;
-                        }
-
-                        panel.PixelOffset = pixelOffset;
-                    }
-                }
-            }
-        }
-
-        /// <inheritdoc/>
-        public override double ViewportValue
-        {
-            get
-            {
-                // If we can't fit the last item in the panel fully, subtract 1 from the viewport.
-                var overflow = VirtualizingPanel.PixelOverflow > 0 ? 1 : 0;
-                return VirtualizingPanel.Children.Count - overflow;
-            }
-        }
-
-        public new IVirtualizingPanel VirtualizingPanel => base.VirtualizingPanel!;
-
-        /// <inheritdoc/>
-        public override Size MeasureOverride(Size availableSize)
-        {
-            var scrollable = (ILogicalScrollable)Owner;
-            var visualRoot = Owner.GetVisualRoot();
-            var maxAvailableSize = (visualRoot as WindowBase)?.PlatformImpl?.MaxAutoSizeHint
-                 ?? (visualRoot as TopLevel)?.ClientSize;
-
-            // If infinity is passed as the available size and we're virtualized then we need to
-            // fill the available space, but to do that we *don't* want to materialize all our
-            // items! Take a look at the root of the tree for a MaxClientSize and use that as
-            // the available size.
-            if (VirtualizingPanel.ScrollDirection == Orientation.Vertical)
-            {
-                if (availableSize.Height == double.PositiveInfinity)
-                {
-                    if (maxAvailableSize.HasValue)
-                    {
-                        availableSize = availableSize.WithHeight(maxAvailableSize.Value.Height);
-                    }
-                }
-
-                if (scrollable.CanHorizontallyScroll)
-                {
-                    availableSize = availableSize.WithWidth(double.PositiveInfinity);
-                }
-            }
-            else
-            {
-                if (availableSize.Width == double.PositiveInfinity)
-                {
-                    if (maxAvailableSize.HasValue)
-                    {
-                        availableSize = availableSize.WithWidth(maxAvailableSize.Value.Width);
-                    }
-                }
-
-                if (scrollable.CanVerticallyScroll)
-                {
-                    availableSize = availableSize.WithHeight(double.PositiveInfinity);
-                }
-            }
-
-            Owner.Panel!.Measure(availableSize);
-            return Owner.Panel.DesiredSize;
-        }
-
-        /// <inheritdoc/>
-        public override void UpdateControls()
-        {
-            CreateAndRemoveContainers();
-            InvalidateScroll();
-        }
-
-        /// <inheritdoc/>
-        public override void ItemsChanged(IEnumerable? items, NotifyCollectionChangedEventArgs e)
-        {
-            base.ItemsChanged(items, e);
-
-            var panel = VirtualizingPanel;
-
-            if (items != null)
-            {
-                switch (e.Action)
-                {
-                    case NotifyCollectionChangedAction.Add:
-                        CreateAndRemoveContainers();
-
-                        if (e.NewStartingIndex < NextIndex)
-                        {
-                            RecycleContainers();
-                        }
-
-                        panel.ForceInvalidateMeasure();
-                        break;
-
-                    case NotifyCollectionChangedAction.Remove:
-                        if (e.OldStartingIndex < NextIndex ||
-                            panel.Children.Count > ItemCount)
-                        {
-                            RecycleContainersOnRemove();
-                        }
-
-                        panel.ForceInvalidateMeasure();
-                        break;
-
-                    case NotifyCollectionChangedAction.Move:
-                    case NotifyCollectionChangedAction.Replace:
-                        RecycleContainers();
-                        break;
-
-                    case NotifyCollectionChangedAction.Reset:
-                        RecycleContainersOnRemove();
-                        CreateAndRemoveContainers();
-                        panel.ForceInvalidateMeasure();
-                        break;
-                }
-            }
-            else
-            {
-                Owner.ItemContainerGenerator.Clear();
-                VirtualizingPanel.Children.Clear();
-                FirstIndex = NextIndex = 0;
-            }
-
-            // If we are scrolled to view a partially visible last item but controls were added
-            // then we need to return to a non-offset scroll position.
-            if (panel.PixelOffset != 0 && FirstIndex + panel.Children.Count < ItemCount)
-            {
-                panel.PixelOffset = 0;
-                RecycleContainersForMove(1);
-            }
-
-            InvalidateScroll();
-        }
-
-        public override Control? GetControlInDirection(NavigationDirection direction, Control? from)
-        {
-            var generator = Owner.ItemContainerGenerator;
-            var panel = VirtualizingPanel;
-            var itemIndex = generator.IndexFromContainer(from);
-            var vertical = VirtualizingPanel.ScrollDirection == Orientation.Vertical;
-
-            var newItemIndex = -1;
-
-            switch (direction)
-            {
-                case NavigationDirection.First:
-                    newItemIndex = 0;
-                    break;
-
-                case NavigationDirection.Last:
-                    newItemIndex = ItemCount - 1;
-                    break;
-
-                default:
-                    if (itemIndex == -1)
-                    {
-                        return null;
-                    }
-                    break;
-            }
-
-            switch (direction)
-            {
-                case NavigationDirection.Up:
-                    if (vertical)
-                    {
-                        newItemIndex = itemIndex - 1;
-                    }
-
-                    break;
-                case NavigationDirection.Down:
-                    if (vertical)
-                    {
-                        newItemIndex = itemIndex + 1;
-                    }
-
-                    break;
-
-                case NavigationDirection.Left:
-                    if (!vertical)
-                    {
-                        newItemIndex = itemIndex - 1;
-                    }
-                    break;
-
-                case NavigationDirection.Right:
-                    if (!vertical)
-                    {
-                        newItemIndex = itemIndex + 1;
-                    }
-                    break;
-
-                case NavigationDirection.PageUp:
-                    newItemIndex = Math.Max(0, itemIndex - (int)ViewportValue);
-                    break;
-
-                case NavigationDirection.PageDown:
-                    newItemIndex = Math.Min(ItemCount - 1, itemIndex + (int)ViewportValue);
-                    break;
-            }
-
-            return ScrollIntoViewCore(newItemIndex);
-        }
-
-        /// <inheritdoc/>
-        public override void ScrollIntoView(int index)
-        {
-            if (index != -1)
-            {
-                ScrollIntoViewCore(index);
-            }
-        }
-
-        /// <summary>
-        /// Creates and removes containers such that we have at most enough containers to fill
-        /// the panel.
-        /// </summary>
-        private void CreateAndRemoveContainers()
-        {
-            var generator = Owner.ItemContainerGenerator;
-            var panel = VirtualizingPanel;
-            var panelControl = (Control)panel;
-
-            if (!panel.IsFull && Items != null && panelControl.IsAttachedToVisualTree)
-            {
-                var index = NextIndex;
-                var step = 1;
-
-                while (!panel.IsFull && index >= 0)
-                {
-                    if (index >= ItemCount)
-                    {
-                        // We can fit more containers in the panel, but we're at the end of the
-                        // items. If we're scrolled to the top (FirstIndex == 0), then there are
-                        // no more items to create. Otherwise, go backwards adding containers to
-                        // the beginning of the panel.
-                        if (FirstIndex == 0)
-                        {
-                            break;
-                        }
-                        else
-                        {
-                            index = FirstIndex - 1;
-                            step = -1;
-                        }
-                    }
-
-                    var materialized = generator.Materialize(index, Items.ElementAt(index)!);
-
-                    if (step == 1)
-                    {
-                        panel.Children.Add(materialized.ContainerControl);
-                    }
-                    else
-                    {
-                        panel.Children.Insert(0, materialized.ContainerControl);
-                    }
-
-                    index += step;
-                }
-
-                if (step == 1)
-                {
-                    NextIndex = index;
-                }
-                else
-                {
-                    NextIndex = ItemCount;
-                    FirstIndex = index + 1;
-                }
-            }
-
-            if (panel.OverflowCount > 0)
-            {
-                if (_anchor <= FirstIndex)
-                {
-                    RemoveContainers(panel.OverflowCount);
-                }
-            }
-        }
-
-        /// <summary>
-        /// Updates the containers in the panel to make sure they are displaying the correct item
-        /// based on <see cref="ItemVirtualizer.FirstIndex"/>.
-        /// </summary>
-        /// <remarks>
-        /// This method requires that <see cref="ItemVirtualizer.FirstIndex"/> + the number of
-        /// materialized containers is not more than <see cref="ItemVirtualizer.ItemCount"/>.
-        /// </remarks>
-        private void RecycleContainers()
-        {
-            var panel = VirtualizingPanel;
-            var generator = Owner.ItemContainerGenerator;
-            var containers = generator.Containers.ToList();
-            var itemIndex = FirstIndex;
-
-            foreach (var container in containers)
-            {
-                var item = Items!.ElementAt(itemIndex)!;
-
-                if (!object.Equals(container.Item, item))
-                {
-                    if (!generator.TryRecycle(itemIndex, itemIndex, item))
-                    {
-                        throw new NotImplementedException();
-                    }
-                }
-
-                ++itemIndex;
-            }
-        }
-
-        /// <summary>
-        /// Recycles containers when a move occurs.
-        /// </summary>
-        /// <param name="delta">The delta of the move.</param>
-        /// <remarks>
-        /// If the move is less than a page, then this method moves the containers for the items
-        /// that are still visible to the correct place, and recycles and moves the others. For
-        /// example: if there are 20 items and 10 containers visible and the user scrolls 5
-        /// items down, then the bottom 5 containers will be moved to the top and the top 5 will
-        /// be moved to the bottom and recycled to display the newly visible item. Updates 
-        /// <see cref="ItemVirtualizer.FirstIndex"/> and <see cref="ItemVirtualizer.NextIndex"/>
-        /// with their new values.
-        /// </remarks>
-        private void RecycleContainersForMove(int delta)
-        {
-            var panel = VirtualizingPanel;
-            var generator = Owner.ItemContainerGenerator;
-
-            //validate delta it should never overflow last index or generate index < 0 
-            delta = MathUtilities.Clamp(delta, -FirstIndex, ItemCount - FirstIndex - panel.Children.Count);
-
-            var sign = delta < 0 ? -1 : 1;
-            var count = Math.Min(Math.Abs(delta), panel.Children.Count);
-            var move = count < panel.Children.Count;
-            var first = delta < 0 && move ? panel.Children.Count + delta : 0;
-
-            for (var i = 0; i < count; ++i)
-            {
-                var oldItemIndex = FirstIndex + first + i;
-                var newItemIndex = oldItemIndex + delta + ((panel.Children.Count - count) * sign);
-
-                var item = Items!.ElementAt(newItemIndex)!;
-
-                if (!generator.TryRecycle(oldItemIndex, newItemIndex, item))
-                {
-                    throw new NotImplementedException();
-                }
-            }
-
-            if (move)
-            {
-                if (delta > 0)
-                {
-                    panel.Children.MoveRange(first, count, panel.Children.Count);
-                }
-                else
-                {
-                    panel.Children.MoveRange(first, count, 0);
-                }
-            }
-
-            FirstIndex += delta;
-            NextIndex += delta;
-        }
-
-        /// <summary>
-        /// Recycles containers due to items being removed.
-        /// </summary>
-        private void RecycleContainersOnRemove()
-        {
-            var panel = VirtualizingPanel;
-
-            if (NextIndex <= ItemCount)
-            {
-                // Items have been removed but FirstIndex..NextIndex is still a valid range in the
-                // items, so just recycle the containers to adapt to the new state.
-                RecycleContainers();
-            }
-            else
-            {
-                // Items have been removed and now the range FirstIndex..NextIndex goes out of 
-                // the item bounds. Remove any excess containers, try to scroll up and then recycle
-                // the containers to make sure they point to the correct item.
-                var newFirstIndex = Math.Max(0, FirstIndex - (NextIndex - ItemCount));
-                var delta = newFirstIndex - FirstIndex;
-                var newNextIndex = NextIndex + delta;
-
-                if (newNextIndex > ItemCount)
-                {
-                    RemoveContainers(newNextIndex - ItemCount);
-                }
-
-                if (delta != 0)
-                {
-                    RecycleContainersForMove(delta);
-                }
-
-                RecycleContainers();
-            }
-        }
-
-        /// <summary>
-        /// Removes the specified number of containers from the end of the panel and updates
-        /// <see cref="ItemVirtualizer.NextIndex"/>.
-        /// </summary>
-        /// <param name="count">The number of containers to remove.</param>
-        private void RemoveContainers(int count)
-        {
-            var index = VirtualizingPanel.Children.Count - count;
-
-            VirtualizingPanel.Children.RemoveRange(index, count);
-            Owner.ItemContainerGenerator.Dematerialize(FirstIndex + index, count);
-            NextIndex -= count;
-        }
-
-        /// <summary>
-        /// Scrolls the item with the specified index into view.
-        /// </summary>
-        /// <param name="index">The item index.</param>
-        /// <returns>The container that was brought into view.</returns>
-        private Control? ScrollIntoViewCore(int index)
-        {
-            var panel = VirtualizingPanel;
-            var panelControl = (Control)panel;
-            var generator = Owner.ItemContainerGenerator;
-            var newOffset = -1.0;
-
-            //better not trigger any container generation/recycle while  or layout stuff
-            //before panel is attached/visible
-            if (!panelControl.IsAttachedToVisualTree)
-            {
-                return null;
-            }
-
-            if (!panelControl.IsMeasureValid && panelControl.PreviousMeasure.HasValue)
-            {
-                //before any kind of scrolling we need to make sure panel measure is valid
-                //or we risk get panel into not valid state
-                //we make a preemptive quick measure so scrolling is valid
-                panelControl.Measure(panelControl.PreviousMeasure.Value);
-            }
-
-            if (index >= 0 && index < ItemCount)
-            {
-                if (index <= FirstIndex)
-                {
-                    newOffset = index;
-                }
-                else if (index >= NextIndex)
-                {
-                    newOffset = index - Math.Ceiling(ViewportValue - 1);
-                }
-
-                if (newOffset != -1)
-                {
-                    OffsetValue = newOffset;
-                }
-
-                var container = generator.ContainerFromIndex(index);
-                var layoutManager = (Owner.GetVisualRoot() as ILayoutRoot)?.LayoutManager;
-
-                // We need to do a layout here because it's possible that the container we moved to
-                // is only partially visible due to differing item sizes. If the container is only 
-                // partially visible, scroll again. Don't do this if there's no layout manager:
-                // it means we're running a unit test.
-                if (container != null && layoutManager != null)
-                {
-                    _anchor = index;
-                    layoutManager.ExecuteLayoutPass();
-                    _anchor = -1;
-
-                    if (newOffset != -1 && newOffset != OffsetValue)
-                    {
-                        OffsetValue = newOffset;
-                    }
-                    
-                    if (panel.ScrollDirection == Orientation.Vertical)
-                    {
-                        if (container.Bounds.Y < panelControl.Bounds.Y || container.Bounds.Bottom > panelControl.Bounds.Bottom)
-                        {
-                            OffsetValue += 1;
-                        }
-                    }
-                    else
-                    {
-                        if (container.Bounds.X < panelControl.Bounds.X || container.Bounds.Right > panelControl.Bounds.Right)
-                        {
-                            OffsetValue += 1;
-                        }
-                    }
-                }
-
-                return container;
-            }
-
-            return null;
-        }
-
-        /// <summary>
-        /// Ensures an offset value is within the value range.
-        /// </summary>
-        /// <param name="value">The value.</param>
-        /// <returns>The coerced value.</returns>
-        private double CoerceOffset(double value)
-        {
-            var max = Math.Max(ExtentValue - ViewportValue, 0);
-            return MathUtilities.Clamp(value, 0, max);
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
index 924c4567f60..2a52e00d670 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
@@ -1,179 +1,88 @@
 using System;
+using System.Collections;
 using System.Collections.Specialized;
-using Avalonia.Controls.Primitives;
-using Avalonia.Input;
-using static Avalonia.Utilities.MathUtilities;
+using System.Diagnostics;
 
 namespace Avalonia.Controls.Presenters
 {
     /// <summary>
-    /// Displays items inside an <see cref="ItemsControl"/>.
+    /// Presents items inside an <see cref="Avalonia.Controls.ItemsControl"/>.
     /// </summary>
-    public class ItemsPresenter : ItemsPresenterBase, ILogicalScrollable
+    public class ItemsPresenter : Control
     {
         /// <summary>
-        /// Defines the <see cref="VirtualizationMode"/> property.
+        /// Defines the <see cref="ItemsPanel"/> property.
         /// </summary>
-        public static readonly StyledProperty<ItemVirtualizationMode> VirtualizationModeProperty =
-            AvaloniaProperty.Register<ItemsPresenter, ItemVirtualizationMode>(
-                nameof(VirtualizationMode),
-                defaultValue: ItemVirtualizationMode.None);
+        public static readonly StyledProperty<ITemplate<Panel>> ItemsPanelProperty =
+            ItemsControl.ItemsPanelProperty.AddOwner<ItemsPresenter>();
 
-        private bool _canHorizontallyScroll;
-        private bool _canVerticallyScroll;
-        private EventHandler? _scrollInvalidated;
+        private ItemsPresenterContainerGenerator? _generator;
 
         /// <summary>
-        /// Initializes static members of the <see cref="ItemsPresenter"/> class.
+        /// Gets or sets a template which creates the <see cref="Panel"/> used to display the items.
         /// </summary>
-        static ItemsPresenter()
+        public ITemplate<Panel> ItemsPanel
         {
-            KeyboardNavigation.TabNavigationProperty.OverrideDefaultValue(
-                typeof(ItemsPresenter),
-                KeyboardNavigationMode.Once);
-
-            VirtualizationModeProperty.Changed
-                .AddClassHandler<ItemsPresenter>((x, e) => x.VirtualizationModeChanged(e));
+            get => GetValue(ItemsPanelProperty);
+            set => SetValue(ItemsPanelProperty, value);
         }
 
         /// <summary>
-        /// Gets or sets the virtualization mode for the items.
+        /// Gets the panel used to display the items.
         /// </summary>
-        public ItemVirtualizationMode VirtualizationMode
-        {
-            get { return GetValue(VirtualizationModeProperty); }
-            set { SetValue(VirtualizationModeProperty, value); }
-        }
+        public Panel? Panel { get; private set; }
 
         /// <summary>
-        /// Gets or sets a value indicating whether the content can be scrolled horizontally.
+        /// Gets the owner <see cref="ItemsControl"/>.
         /// </summary>
-        bool ILogicalScrollable.CanHorizontallyScroll
-        {
-            get { return _canHorizontallyScroll; }
-            set
-            {
-                _canHorizontallyScroll = value;
-                InvalidateMeasure();
-            }
-        }
+        internal ItemsControl? ItemsControl { get; private set; }
 
-        /// <summary>
-        /// Gets or sets a value indicating whether the content can be scrolled horizontally.
-        /// </summary>
-        bool ILogicalScrollable.CanVerticallyScroll
+        public override sealed void ApplyTemplate()
         {
-            get { return _canVerticallyScroll; }
-            set
+            if (Panel is null)
             {
-                _canVerticallyScroll = value;
-                InvalidateMeasure();
+                Panel = ItemsPanel.Build();
+                Panel.SetValue(TemplatedParentProperty, TemplatedParent);
+                LogicalChildren.Add(Panel);
+                VisualChildren.Add(Panel);
+                CreateGeneratorIfSimplePanel();
             }
         }
-        /// <inheritdoc/>
-        bool ILogicalScrollable.IsLogicalScrollEnabled
-        {
-            get { return Virtualizer?.IsLogicalScrollEnabled ?? false; }
-        }
-
-        /// <inheritdoc/>
-        Size IScrollable.Extent => Virtualizer?.Extent ?? Size.Empty;
 
-        /// <inheritdoc/>
-        Vector IScrollable.Offset
+        protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
         {
-            get { return Virtualizer?.Offset ?? new Vector(); }
-            set
+            base.OnPropertyChanged(change);
+
+            if (change.Property == TemplatedParentProperty)
             {
-                if (Virtualizer != null)
+                _generator?.Dispose();
+                _generator = null;
+
+                if (change.NewValue is ItemsControl itemsControl)
                 {
-                    Virtualizer.Offset = CoerceOffset(value);
+                    ItemsControl = itemsControl;
+                    ((IItemsPresenterHost)itemsControl)?.RegisterItemsPresenter(this);
+                    CreateGeneratorIfSimplePanel();
                 }
             }
+            else if (change.Property == ItemsPanelProperty)
+            {
+                _generator?.Dispose();
+                _generator = null;
+                LogicalChildren.Clear();
+                VisualChildren.Clear();
+                Panel = null;
+                InvalidateMeasure();
+            }
         }
 
-        /// <inheritdoc/>
-        Size IScrollable.Viewport => Virtualizer?.Viewport ?? Bounds.Size;
-
-        /// <inheritdoc/>
-        event EventHandler? ILogicalScrollable.ScrollInvalidated
-        {
-            add => _scrollInvalidated += value;
-            remove => _scrollInvalidated -= value;
-        }
-
-        /// <inheritdoc/>
-        Size ILogicalScrollable.ScrollSize => new Size(ScrollViewer.DefaultSmallChange, 1);
-
-        /// <inheritdoc/>
-        Size ILogicalScrollable.PageScrollSize => Virtualizer?.Viewport ?? new Size(16, 16);
-
-        internal ItemVirtualizer? Virtualizer { get; private set; }
-
-        /// <inheritdoc/>
-        bool ILogicalScrollable.BringIntoView(Control target, Rect targetRect)
-        {
-            return false;
-        }
-
-        /// <inheritdoc/>
-        Control? ILogicalScrollable.GetControlInDirection(NavigationDirection direction, Control? from)
-        {
-            return Virtualizer?.GetControlInDirection(direction, from);
-        }
-
-        /// <inheritdoc/>
-        void ILogicalScrollable.RaiseScrollInvalidated(EventArgs e)
-        {
-            _scrollInvalidated?.Invoke(this, e);
-        }
-
-        public override void ScrollIntoView(int index)
-        {
-            Virtualizer?.ScrollIntoView(index);
-        }
-
-        /// <inheritdoc/>
-        protected override Size MeasureOverride(Size availableSize)
-        {
-            return Virtualizer?.MeasureOverride(availableSize) ?? Size.Empty;
-        }
-
-        protected override Size ArrangeOverride(Size finalSize)
-        {
-            return Virtualizer?.ArrangeOverride(finalSize) ?? Size.Empty;
-        }
-
-        /// <inheritdoc/>
-        protected override void PanelCreated(Panel panel)
-        {
-            Virtualizer?.Dispose();
-            Virtualizer = ItemVirtualizer.Create(this);
-            _scrollInvalidated?.Invoke(this, EventArgs.Empty);
-
-            KeyboardNavigation.SetTabNavigation(
-                (InputElement)panel,
-                KeyboardNavigation.GetTabNavigation(this));
-        }
-
-        protected override void ItemsChanged(NotifyCollectionChangedEventArgs e)
-        {
-            Virtualizer?.ItemsChanged(Items, e);
-        }
-
-        private Vector CoerceOffset(Vector value)
+        private void CreateGeneratorIfSimplePanel()
         {
-            var scrollable = (ILogicalScrollable)this;
-            var maxX = Math.Max(scrollable.Extent.Width - scrollable.Viewport.Width, 0);
-            var maxY = Math.Max(scrollable.Extent.Height - scrollable.Viewport.Height, 0);
-            return new Vector(Clamp(value.X, 0, maxX), Clamp(value.Y, 0, maxY));
-        }
+            if (ItemsControl is null || Panel is null || Panel is IVirtualizingPanel)
+                return;
 
-        private void VirtualizationModeChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            Virtualizer?.Dispose();
-            Virtualizer = ItemVirtualizer.Create(this);
-            _scrollInvalidated?.Invoke(this, EventArgs.Empty);
+            _generator?.Dispose();
+            _generator = new(this);
         }
     }
 }
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenterBase.cs b/src/Avalonia.Controls/Presenters/ItemsPresenterBase.cs
deleted file mode 100644
index 38a2a5722c1..00000000000
--- a/src/Avalonia.Controls/Presenters/ItemsPresenterBase.cs
+++ /dev/null
@@ -1,308 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Specialized;
-using Avalonia.Collections;
-using Avalonia.Controls.Generators;
-using Avalonia.Controls.Templates;
-using Avalonia.Controls.Utils;
-using Avalonia.Data;
-using Avalonia.LogicalTree;
-using Avalonia.Styling;
-
-namespace Avalonia.Controls.Presenters
-{
-    /// <summary>
-    /// Base class for controls that present items inside an <see cref="ItemsControl"/>.
-    /// </summary>
-    public abstract class ItemsPresenterBase : Control, IItemsPresenter, IChildIndexProvider
-    {
-        /// <summary>
-        /// Defines the <see cref="Items"/> property.
-        /// </summary>
-        public static readonly DirectProperty<ItemsPresenterBase, IEnumerable?> ItemsProperty =
-            ItemsControl.ItemsProperty.AddOwner<ItemsPresenterBase>(o => o.Items, (o, v) => o.Items = v);
-
-        /// <summary>
-        /// Defines the <see cref="ItemsPanel"/> property.
-        /// </summary>
-        public static readonly StyledProperty<ITemplate<Panel>> ItemsPanelProperty =
-            ItemsControl.ItemsPanelProperty.AddOwner<ItemsPresenterBase>();
-
-        /// <summary>
-        /// Defines the <see cref="ItemTemplate"/> property.
-        /// </summary>
-        public static readonly StyledProperty<IDataTemplate?> ItemTemplateProperty =
-            ItemsControl.ItemTemplateProperty.AddOwner<ItemsPresenterBase>();
-
-        /// <summary>
-        /// Defines the <see cref="DisplayMemberBinding" /> property
-        /// </summary>
-        public static readonly StyledProperty<IBinding?> DisplayMemberBindingProperty =
-            ItemsControl.DisplayMemberBindingProperty.AddOwner<ItemsPresenterBase>();
-        
-        private IEnumerable? _items;
-        private IDisposable? _itemsSubscription;
-        private bool _createdPanel;
-        private IItemContainerGenerator? _generator;
-        private EventHandler<ChildIndexChangedEventArgs>? _childIndexChanged;
-
-        /// <summary>
-        /// Initializes static members of the <see cref="ItemsPresenter"/> class.
-        /// </summary>
-        static ItemsPresenterBase()
-        {
-            TemplatedParentProperty.Changed.AddClassHandler<ItemsPresenterBase>((x,e) => x.TemplatedParentChanged(e));
-        }
-
-        /// <summary>
-        /// Gets or sets the items to be displayed.
-        /// </summary>
-        public IEnumerable? Items
-        {
-            get
-            {
-                return _items;
-            }
-
-            set
-            {
-                _itemsSubscription?.Dispose();
-                _itemsSubscription = null;
-
-                if (!IsHosted && _createdPanel && value is INotifyCollectionChanged incc)
-                {
-                    _itemsSubscription = incc.WeakSubscribe(ItemsCollectionChanged);
-                }
-
-                SetAndRaise(ItemsProperty, ref _items, value);
-
-                if (_createdPanel)
-                {
-                    ItemsChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
-                }
-            }
-        }
-
-        /// <summary>
-        /// Gets the item container generator.
-        /// </summary>
-        public IItemContainerGenerator ItemContainerGenerator
-        {
-            get
-            {
-                if (_generator == null)
-                {
-                    _generator = CreateItemContainerGenerator();
-                }
-
-                return _generator;
-            }
-
-            internal set
-            {
-                if (_generator != null)
-                {
-                    throw new InvalidOperationException("ItemContainerGenerator already created.");
-                }
-
-                _generator = value;
-            }
-        }
-
-        /// <summary>
-        /// Gets or sets a template which creates the <see cref="Panel"/> used to display the items.
-        /// </summary>
-        public ITemplate<Panel> ItemsPanel
-        {
-            get { return GetValue(ItemsPanelProperty); }
-            set { SetValue(ItemsPanelProperty, value); }
-        }
-
-        /// <summary>
-        /// Gets or sets the data template used to display the items in the control.
-        /// </summary>
-        public IDataTemplate? ItemTemplate
-        {
-            get { return GetValue(ItemTemplateProperty); }
-            set { SetValue(ItemTemplateProperty, value); }
-        }
-
-        /// <summary>
-        /// Gets or sets the <see cref="IBinding"/> to use for binding to the display member of each item.
-        /// </summary>
-        public IBinding? DisplayMemberBinding
-        {
-            get { return GetValue(DisplayMemberBindingProperty); }
-            set { SetValue(DisplayMemberBindingProperty, value); }
-        }
-
-        /// <summary>
-        /// Gets the panel used to display the items.
-        /// </summary>
-        public Panel? Panel
-        {
-            get;
-            private set;
-        }
-
-        protected bool IsHosted => TemplatedParent is IItemsPresenterHost;
-
-        event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexChanged
-        {
-            add => _childIndexChanged += value;
-            remove => _childIndexChanged -= value;
-        }
-
-        /// <inheritdoc/>
-        public override sealed void ApplyTemplate()
-        {
-            if (!_createdPanel)
-            {
-                CreatePanel();
-            }
-        }
-
-        /// <inheritdoc/>
-        public virtual void ScrollIntoView(int index)
-        {
-        }
-
-        /// <inheritdoc/>
-        void IItemsPresenter.ItemsChanged(NotifyCollectionChangedEventArgs e)
-        {
-            if (Panel != null)
-            {
-                ItemsChanged(e);
-
-                _childIndexChanged?.Invoke(this, ChildIndexChangedEventArgs.Empty);
-            }
-        }
-
-        /// <summary>
-        /// Creates the <see cref="ItemContainerGenerator"/> for the control.
-        /// </summary>
-        /// <returns>
-        /// An <see cref="IItemContainerGenerator"/> or null.
-        /// </returns>
-        protected virtual IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            var i = TemplatedParent as ItemsControl;
-            var result = i?.ItemContainerGenerator;
-
-            if (result == null)
-            {
-                result = new ItemContainerGenerator(this);
-                result.ItemTemplate = ItemTemplate;
-                result.DisplayMemberBinding = DisplayMemberBinding;
-            }
-
-            result.Materialized += ContainerActionHandler;
-            result.Dematerialized += ContainerActionHandler;
-            result.Recycled += ContainerActionHandler;
-
-            return result;
-        }
-
-        private void ContainerActionHandler(object? sender, ItemContainerEventArgs e)
-        {
-            for (var i = 0; i < e.Containers.Count; i++)
-            {
-                _childIndexChanged?.Invoke(this, new ChildIndexChangedEventArgs(e.Containers[i].ContainerControl));
-            }
-        }
-
-        /// <inheritdoc/>
-        protected override Size MeasureOverride(Size availableSize)
-        {
-            Panel!.Measure(availableSize);
-            return Panel.DesiredSize;
-        }
-
-        /// <inheritdoc/>
-        protected override Size ArrangeOverride(Size finalSize)
-        {
-            Panel!.Arrange(new Rect(finalSize));
-            return finalSize;
-        }
-
-        /// <summary>
-        /// Called when the <see cref="Panel"/> is created.
-        /// </summary>
-        /// <param name="panel">The panel.</param>
-        protected virtual void PanelCreated(Panel panel)
-        {
-        }
-
-        /// <summary>
-        /// Called when the items for the presenter change, either because <see cref="Items"/>
-        /// has been set, the items collection has been modified, or the panel has been created.
-        /// </summary>
-        /// <param name="e">A description of the change.</param>
-        /// <remarks>
-        /// The panel is guaranteed to be created when this method is called.
-        /// </remarks>
-        protected virtual void ItemsChanged(NotifyCollectionChangedEventArgs e)
-        {
-            ItemContainerSync.ItemsChanged(this, Items, e);
-        }
-
-        /// <summary>
-        /// Creates the <see cref="Panel"/> when <see cref="ApplyTemplate"/> is called for the first
-        /// time.
-        /// </summary>
-        private void CreatePanel()
-        {
-            Panel = ItemsPanel.Build();
-            Panel.SetValue(TemplatedParentProperty, TemplatedParent);
-
-            LogicalChildren.Clear();
-            VisualChildren.Clear();
-            LogicalChildren.Add(Panel);
-            VisualChildren.Add(Panel);
-
-            _createdPanel = true;
-
-            if (!IsHosted && _itemsSubscription == null && Items is INotifyCollectionChanged incc)
-            {
-                _itemsSubscription = incc.WeakSubscribe(ItemsCollectionChanged);
-            }
-
-            PanelCreated(Panel);
-        }
-
-        /// <summary>
-        /// Called when the <see cref="Items"/> collection changes.
-        /// </summary>
-        /// <param name="sender">The sender.</param>
-        /// <param name="e">The event args.</param>
-        private void ItemsCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
-        {
-            if (_createdPanel)
-            {
-                ItemsChanged(e);
-            }
-        }
-
-        private void TemplatedParentChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            (e.NewValue as IItemsPresenterHost)?.RegisterItemsPresenter(this);
-        }
-
-        int IChildIndexProvider.GetChildIndex(ILogical child)
-        {
-            if (child is Control control && ItemContainerGenerator is { } generator)
-            {
-                var index = ItemContainerGenerator.IndexFromContainer(control);
-
-                return index;
-            }
-
-            return -1;
-        }
-
-        bool IChildIndexProvider.TryGetTotalCount(out int count)
-        {
-            return Items.TryGetCountFast(out count);
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs b/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs
new file mode 100644
index 00000000000..4c2bd35f5a7
--- /dev/null
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs
@@ -0,0 +1,108 @@
+using System;
+using System.Collections;
+using System.Collections.Specialized;
+using System.Diagnostics;
+
+namespace Avalonia.Controls.Presenters
+{
+    /// <summary>
+    /// Generates containers for <see cref="ItemsPresenter"/>s that have non-virtualizing panels.
+    /// </summary>
+    internal class ItemsPresenterContainerGenerator : IDisposable
+    {
+        private static NotifyCollectionChangedEventArgs s_Reset = new(NotifyCollectionChangedAction.Reset);
+        private ItemsPresenter _presenter;
+
+        public ItemsPresenterContainerGenerator(ItemsPresenter presenter)
+        {
+            Debug.Assert(presenter.ItemsControl is not null);
+            Debug.Assert(presenter.Panel is not null or IVirtualizingPanel);
+            
+            _presenter = presenter;
+            _presenter.ItemsControl.PropertyChanged += OnItemsControlPropertyChanged;
+
+            if (_presenter.ItemsControl.Items is INotifyCollectionChanged incc)
+                incc.CollectionChanged += OnItemsChanged;
+
+            OnItemsChanged(null, s_Reset);
+        }
+
+        public void Dispose()
+        {
+            _presenter.ItemsControl!.PropertyChanged -= OnItemsControlPropertyChanged;
+
+            if (_presenter.ItemsControl.Items is INotifyCollectionChanged incc)
+                incc.CollectionChanged -= OnItemsChanged;
+
+            _presenter.Panel!.Children.Clear();
+        }
+
+        private void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+        {
+            if (e.Property == ItemsControl.ItemsProperty)
+            {
+                if (e.OldValue is INotifyCollectionChanged inccOld)
+                    inccOld.CollectionChanged -= OnItemsChanged;
+                OnItemsChanged(null, s_Reset);
+                if (e.NewValue is INotifyCollectionChanged inccNew)
+                    inccNew.CollectionChanged += OnItemsChanged;
+            }
+        }
+
+        private void OnItemsChanged(object? sender, NotifyCollectionChangedEventArgs e)
+        {
+            if (_presenter.ItemsControl?.Items is null || _presenter.Panel is null)
+                return;
+
+            var generator = _presenter.ItemsControl.ItemContainerGenerator;
+            var panel = _presenter.Panel;
+
+            void Add(int index, IEnumerable items)
+            {
+                var i = index;
+
+                foreach (var item in items)
+                {
+                    var c = generator.Materialize(i, item);
+                    panel.Children.Insert(i++, c.ContainerControl);
+                }
+            }
+            
+            void Remove(int index, int count)
+            {
+                for (var i = 0; i < count; ++i)
+                    panel.Children.RemoveAt(i + index);
+            }
+
+            switch (e.Action)
+            {
+                case NotifyCollectionChangedAction.Add:
+                    generator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
+                    Add(e.NewStartingIndex, e.NewItems!);
+                    break;
+                case NotifyCollectionChangedAction.Remove:
+                    generator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
+                    Remove(e.OldStartingIndex, e.OldItems!.Count);
+                    break;
+                case NotifyCollectionChangedAction.Replace:
+                    generator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
+                    Remove(e.OldStartingIndex, e.OldItems!.Count);
+                    generator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
+                    Add(e.NewStartingIndex, e.NewItems!);
+                    break;
+                case NotifyCollectionChangedAction.Move:
+                    generator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
+                    Remove(e.OldStartingIndex, e.OldItems!.Count);
+                    generator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
+                    Add(e.NewStartingIndex, e.NewItems!);
+                    break;
+                case NotifyCollectionChangedAction.Reset:
+                    generator.Clear();
+                    panel.Children.Clear();
+                    if (_presenter.ItemsControl.Items is { } items)
+                        Add(0, items);
+                    break;
+            }
+        }
+    }
+}
diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index 44fa78ac211..7f8d8f098ab 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -373,7 +373,7 @@ public override void EndInit()
         /// Scrolls the specified item into view.
         /// </summary>
         /// <param name="index">The index of the item.</param>
-        public void ScrollIntoView(int index) => Presenter?.ScrollIntoView(index);
+        public void ScrollIntoView(int index) => throw new NotImplementedException(); ////Presenter?.ScrollIntoView(index);
 
         /// <summary>
         /// Scrolls the specified item into view.
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index f7cf1b922d4..ea94440bf16 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -1,252 +1,20 @@
 using System;
-using System.Collections.Specialized;
-using Avalonia.Controls.Primitives;
-using Avalonia.Input;
-using Avalonia.Layout;
 
 namespace Avalonia.Controls
 {
-    public class VirtualizingStackPanel : StackPanel, IVirtualizingPanel
+    public class VirtualizingStackPanel : StackPanel
     {
-        private Size _availableSpace;
-        private double _takenSpace;
-        private int _canBeRemoved;
-        private double _averageItemSize;
-        private int _averageCount;
-        private double _pixelOffset;
-        private double _crossAxisOffset;
-        private bool _forceRemeasure;
+        /// <summary>
+        /// Defines the <see cref="VirtualizationMode"/> property.
+        /// </summary>
+        public static readonly StyledProperty<ItemVirtualizationMode> VirtualizationModeProperty =
+            AvaloniaProperty.Register<VirtualizingStackPanel, ItemVirtualizationMode>(
+                nameof(VirtualizationMode));
 
-        bool IVirtualizingPanel.IsFull
+        public ItemVirtualizationMode VirtualizationMode
         {
-            get
-            {
-                return Orientation == Orientation.Horizontal ?
-                    _takenSpace >= _availableSpace.Width :
-                    _takenSpace >= _availableSpace.Height;
-            }
-        }
-
-        IVirtualizingController? IVirtualizingPanel.Controller { get; set; }
-        int IVirtualizingPanel.OverflowCount => _canBeRemoved;
-        Orientation IVirtualizingPanel.ScrollDirection => Orientation;
-        double IVirtualizingPanel.AverageItemSize => _averageItemSize;
-
-        double IVirtualizingPanel.PixelOverflow
-        {
-            get
-            {
-                var bounds = Orientation == Orientation.Horizontal ?
-                    _availableSpace.Width : _availableSpace.Height;
-                return Math.Max(0, _takenSpace - bounds);
-            }
-        }
-
-        double IVirtualizingPanel.PixelOffset
-        {
-            get { return _pixelOffset; }
-
-            set
-            {
-                if (_pixelOffset != value)
-                {
-                    _pixelOffset = value;
-                    InvalidateArrange();
-                }
-            }
-        }
-
-        double IVirtualizingPanel.CrossAxisOffset
-        {
-            get { return _crossAxisOffset; }
-
-            set
-            {
-                if (_crossAxisOffset != value)
-                {
-                    _crossAxisOffset = value;
-                    InvalidateArrange();
-                }
-            }
-        }
-
-        private IVirtualizingController? Controller => ((IVirtualizingPanel)this).Controller;
-
-        void IVirtualizingPanel.ForceInvalidateMeasure()
-        {
-            InvalidateMeasure();
-            _forceRemeasure = true;
-        }
-
-        protected override Size MeasureOverride(Size availableSize)
-        {
-            if (_forceRemeasure || availableSize != PreviousMeasure)
-            {
-                _forceRemeasure = false;
-                _availableSpace = availableSize;
-                Controller?.UpdateControls();
-            }
-
-            return base.MeasureOverride(availableSize);
-        }
-
-        protected override Size ArrangeOverride(Size finalSize)
-        {
-            _availableSpace = finalSize;
-            _canBeRemoved = 0;
-            _takenSpace = 0;
-            _averageItemSize = 0;
-            _averageCount = 0;
-            var result = base.ArrangeOverride(finalSize);
-            _takenSpace += _pixelOffset;
-            Controller?.UpdateControls();
-            return result;
-        }
-
-        protected override void ChildrenChanged(object? sender, NotifyCollectionChangedEventArgs e)
-        {
-            base.ChildrenChanged(sender, e);
-
-            switch (e.Action)
-            {
-                case NotifyCollectionChangedAction.Add:
-                    foreach (Control control in e.NewItems!)
-                    {
-                        UpdateAdd(control);
-                    }
-
-                    break;
-
-                case NotifyCollectionChangedAction.Remove:
-                    foreach (Control control in e.OldItems!)
-                    {
-                        UpdateRemove(control);
-                    }
-
-                    break;
-            }
-        }
-
-        protected override IInputElement? GetControlInDirection(NavigationDirection direction, Control? from)
-        {
-            var logicalScrollable = Parent as ILogicalScrollable;
-
-            if (logicalScrollable?.IsLogicalScrollEnabled == true)
-            {
-                return logicalScrollable.GetControlInDirection(direction, from);
-            }
-            else
-            {
-                return base.GetControlInDirection(direction, from);
-            }
-        }
-
-        internal override void ArrangeChild(
-            Control child,
-            Rect rect,
-            Size panelSize,
-            Orientation orientation)
-        {
-            if (orientation == Orientation.Vertical)
-            {
-                rect = new Rect(
-                    rect.X - _crossAxisOffset,
-                    rect.Y - _pixelOffset,
-                    rect.Width,
-                    rect.Height);
-                child.Arrange(rect);
-
-                if (rect.Y >= _availableSpace.Height)
-                {
-                    ++_canBeRemoved;
-                }
-
-                if (rect.Bottom >= _takenSpace)
-                {
-                    _takenSpace = rect.Bottom;
-                }
-
-                AddToAverageItemSize(rect.Height);
-            }
-            else
-            {
-                rect = new Rect(
-                    rect.X - _pixelOffset,
-                    rect.Y - _crossAxisOffset,
-                    rect.Width,
-                    rect.Height);
-                child.Arrange(rect);
-
-                if (rect.X >= _availableSpace.Width)
-                {
-                    ++_canBeRemoved;
-                }
-
-                if (rect.Right >= _takenSpace)
-                {
-                    _takenSpace = rect.Right;
-                }
-
-                AddToAverageItemSize(rect.Width);
-            }
-        }
-
-        private void UpdateAdd(Control child)
-        {
-            var bounds = Bounds;
-            var spacing = Spacing;
-
-            child.Measure(_availableSpace);
-            ++_averageCount;
-
-            if (Orientation == Orientation.Vertical)
-            {
-                var height = child.DesiredSize.Height;
-                _takenSpace += height + spacing;
-                AddToAverageItemSize(height);
-            }
-            else
-            {
-                var width = child.DesiredSize.Width;
-                _takenSpace += width + spacing;
-                AddToAverageItemSize(width);
-            }
-        }
-
-        private void UpdateRemove(Control child)
-        {
-            var bounds = Bounds;
-            var spacing = Spacing;
-
-            if (Orientation == Orientation.Vertical)
-            {
-                var height = child.DesiredSize.Height;
-                _takenSpace -= height + spacing;
-                RemoveFromAverageItemSize(height);
-            }
-            else
-            {
-                var width = child.DesiredSize.Width;
-                _takenSpace -= width + spacing;
-                RemoveFromAverageItemSize(width);
-            }
-
-            if (_canBeRemoved > 0)
-            {
-                --_canBeRemoved;
-            }
-        }
-
-        private void AddToAverageItemSize(double value)
-        {
-            ++_averageCount;
-            _averageItemSize += (value - _averageItemSize) / _averageCount;
-        }
-
-        private void RemoveFromAverageItemSize(double value)
-        {
-            _averageItemSize = ((_averageItemSize * _averageCount) - value) / (_averageCount - 1);
-            --_averageCount;
+            get => GetValue(VirtualizationModeProperty);
+            set => SetValue(VirtualizationModeProperty, value);
         }
     }
 }
diff --git a/src/Avalonia.Themes.Fluent/Controls/Carousel.xaml b/src/Avalonia.Themes.Fluent/Controls/Carousel.xaml
index 2cac701e1b4..1dab50052d2 100644
--- a/src/Avalonia.Themes.Fluent/Controls/Carousel.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/Carousel.xaml
@@ -8,7 +8,6 @@
                 BorderThickness="{TemplateBinding BorderThickness}"
                 CornerRadius="{TemplateBinding CornerRadius}">
           <CarouselPresenter IsVirtualized="{TemplateBinding IsVirtualized}"
-                             Items="{TemplateBinding Items}"
                              ItemsPanel="{TemplateBinding ItemsPanel}"
                              Margin="{TemplateBinding Padding}"
                              SelectedIndex="{TemplateBinding SelectedIndex}"
diff --git a/src/Avalonia.Themes.Fluent/Controls/ComboBox.xaml b/src/Avalonia.Themes.Fluent/Controls/ComboBox.xaml
index 24d9d21df82..bc36ad987e8 100644
--- a/src/Avalonia.Themes.Fluent/Controls/ComboBox.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/ComboBox.xaml
@@ -128,11 +128,8 @@
                 <ScrollViewer HorizontalScrollBarVisibility="{TemplateBinding ScrollViewer.HorizontalScrollBarVisibility}"
                               VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}">
                   <ItemsPresenter Name="PART_ItemsPresenter"
-                                  Items="{TemplateBinding Items}"
                                   Margin="{DynamicResource ComboBoxDropdownContentMargin}"
-                                  ItemsPanel="{TemplateBinding ItemsPanel}"
-                                  ItemTemplate="{TemplateBinding ItemTemplate}"
-                                  VirtualizationMode="{TemplateBinding VirtualizationMode}" />
+                                  ItemsPanel="{TemplateBinding ItemsPanel}" />
                 </ScrollViewer>
               </Border>
             </Popup>
diff --git a/src/Avalonia.Themes.Fluent/Controls/ContextMenu.xaml b/src/Avalonia.Themes.Fluent/Controls/ContextMenu.xaml
index fdd79ed736a..f6900f785f8 100644
--- a/src/Avalonia.Themes.Fluent/Controls/ContextMenu.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/ContextMenu.xaml
@@ -56,9 +56,7 @@
                 CornerRadius="{TemplateBinding CornerRadius}">
           <ScrollViewer Theme="{StaticResource FluentMenuScrollViewer}">
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
                             Margin="{DynamicResource MenuFlyoutScrollerMargin}"
                             KeyboardNavigation.TabNavigation="Continue"
                             Grid.IsSharedSizeScope="True" />
diff --git a/src/Avalonia.Themes.Fluent/Controls/ItemsControl.xaml b/src/Avalonia.Themes.Fluent/Controls/ItemsControl.xaml
index fc85b7b9ff1..1306985f5ff 100644
--- a/src/Avalonia.Themes.Fluent/Controls/ItemsControl.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/ItemsControl.xaml
@@ -9,9 +9,7 @@
                 CornerRadius="{TemplateBinding CornerRadius}"
                 Padding="{TemplateBinding Padding}">
           <ItemsPresenter Name="PART_ItemsPresenter"
-                          Items="{TemplateBinding Items}"
-                          ItemsPanel="{TemplateBinding ItemsPanel}"
-                          ItemTemplate="{TemplateBinding ItemTemplate}"/>
+                          ItemsPanel="{TemplateBinding ItemsPanel}"/>
         </Border>
       </ControlTemplate>
     </Setter>
diff --git a/src/Avalonia.Themes.Fluent/Controls/ListBox.xaml b/src/Avalonia.Themes.Fluent/Controls/ListBox.xaml
index c17dc65cca4..ec0b876c717 100644
--- a/src/Avalonia.Themes.Fluent/Controls/ListBox.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/ListBox.xaml
@@ -34,11 +34,8 @@
                         IsScrollChainingEnabled="{TemplateBinding (ScrollViewer.IsScrollChainingEnabled)}"
                         AllowAutoHide="{TemplateBinding (ScrollViewer.AllowAutoHide)}">
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
-                            Margin="{TemplateBinding Padding}"
-                            VirtualizationMode="{TemplateBinding VirtualizationMode}" />
+                            Margin="{TemplateBinding Padding}"/>
           </ScrollViewer>
         </Border>
       </ControlTemplate>
diff --git a/src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml b/src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml
index d1707d0af26..cdfca65ff6d 100644
--- a/src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml
@@ -273,11 +273,8 @@
           <Border Name="border" BoxShadow="inset -6 0 3 -3 #20000000" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}">
             <ScrollViewer Name="PART_ScrollViewer" HorizontalScrollBarVisibility="{TemplateBinding (ScrollViewer.HorizontalScrollBarVisibility)}" VerticalScrollBarVisibility="{TemplateBinding (ScrollViewer.VerticalScrollBarVisibility)}">
               <ItemsPresenter Name="PART_ItemsPresenter"
-                              Items="{TemplateBinding Items}"
                               ItemsPanel="{TemplateBinding ItemsPanel}"
-                              ItemTemplate="{TemplateBinding ItemTemplate}"
-                              Margin="{TemplateBinding Padding}"
-                              VirtualizationMode="{TemplateBinding VirtualizationMode}"/>
+                              Margin="{TemplateBinding Padding}"/>
             </ScrollViewer>
           </Border>
         </ControlTemplate>
diff --git a/src/Avalonia.Themes.Fluent/Controls/Menu.xaml b/src/Avalonia.Themes.Fluent/Controls/Menu.xaml
index f5fd69a67fc..692bac958ac 100644
--- a/src/Avalonia.Themes.Fluent/Controls/Menu.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/Menu.xaml
@@ -48,9 +48,7 @@
                       CornerRadius="{DynamicResource OverlayCornerRadius}">
                 <ScrollViewer Theme="{StaticResource FluentMenuScrollViewer}">
                   <ItemsPresenter Name="PART_ItemsPresenter"
-                                  Items="{TemplateBinding Items}"
                                   ItemsPanel="{TemplateBinding ItemsPanel}"
-                                  ItemTemplate="{TemplateBinding ItemTemplate}"
                                   Margin="{DynamicResource MenuFlyoutScrollerMargin}"
                                   Grid.IsSharedSizeScope="True" />
                 </ScrollViewer>
@@ -101,9 +99,7 @@
                 HorizontalAlignment="Stretch"
                 Padding="{TemplateBinding Padding}">
           <ItemsPresenter Name="PART_ItemsPresenter"
-                          Items="{TemplateBinding Items}"
                           ItemsPanel="{TemplateBinding ItemsPanel}"
-                          ItemTemplate="{TemplateBinding ItemTemplate}"
                           VerticalAlignment="Stretch"
                           KeyboardNavigation.TabNavigation="Continue" />
         </Border>
diff --git a/src/Avalonia.Themes.Fluent/Controls/MenuFlyoutPresenter.xaml b/src/Avalonia.Themes.Fluent/Controls/MenuFlyoutPresenter.xaml
index 6bca00b2190..b1f44cc70d8 100644
--- a/src/Avalonia.Themes.Fluent/Controls/MenuFlyoutPresenter.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/MenuFlyoutPresenter.xaml
@@ -22,9 +22,7 @@
                         Theme="{StaticResource FluentMenuScrollViewer}"
                         VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}">
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
                             Margin="{DynamicResource MenuFlyoutScrollerMargin}"
                             KeyboardNavigation.TabNavigation="Continue"
                             Grid.IsSharedSizeScope="True" />
diff --git a/src/Avalonia.Themes.Fluent/Controls/MenuItem.xaml b/src/Avalonia.Themes.Fluent/Controls/MenuItem.xaml
index 4060d7efbef..e87f4b7d93e 100644
--- a/src/Avalonia.Themes.Fluent/Controls/MenuItem.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/MenuItem.xaml
@@ -131,9 +131,7 @@
                     CornerRadius="{DynamicResource OverlayCornerRadius}">
               <ScrollViewer Theme="{StaticResource FluentMenuScrollViewer}">
                 <ItemsPresenter Name="PART_ItemsPresenter"
-                                Items="{TemplateBinding Items}"
                                 ItemsPanel="{TemplateBinding ItemsPanel}"
-                                ItemTemplate="{TemplateBinding ItemTemplate}"
                                 Margin="{DynamicResource MenuFlyoutScrollerMargin}"
                                 Grid.IsSharedSizeScope="True" />
               </ScrollViewer>
diff --git a/src/Avalonia.Themes.Fluent/Controls/TabControl.xaml b/src/Avalonia.Themes.Fluent/Controls/TabControl.xaml
index 17d179e0cd6..cd89443e1f5 100644
--- a/src/Avalonia.Themes.Fluent/Controls/TabControl.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/TabControl.xaml
@@ -32,9 +32,7 @@
                 VerticalAlignment="{TemplateBinding VerticalAlignment}">
           <DockPanel>
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
                             DockPanel.Dock="{TemplateBinding TabStripPlacement}" />
             <ContentPresenter Name="PART_SelectedContentHost"
                               Margin="{TemplateBinding Padding}"
diff --git a/src/Avalonia.Themes.Fluent/Controls/TabStrip.xaml b/src/Avalonia.Themes.Fluent/Controls/TabStrip.xaml
index 59cb7f67524..ead6fc41ab5 100644
--- a/src/Avalonia.Themes.Fluent/Controls/TabStrip.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/TabStrip.xaml
@@ -19,9 +19,7 @@
                 CornerRadius="{TemplateBinding CornerRadius}"
                 Padding="{TemplateBinding Padding}">
           <ItemsPresenter Name="PART_ItemsPresenter"
-                          Items="{TemplateBinding Items}"
-                          ItemsPanel="{TemplateBinding ItemsPanel}"
-                          ItemTemplate="{TemplateBinding ItemTemplate}" />
+                          ItemsPanel="{TemplateBinding ItemsPanel}" />
         </Border>
       </ControlTemplate>
     </Setter>
diff --git a/src/Avalonia.Themes.Fluent/Controls/TreeView.xaml b/src/Avalonia.Themes.Fluent/Controls/TreeView.xaml
index c3405990008..c43e4161918 100644
--- a/src/Avalonia.Themes.Fluent/Controls/TreeView.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/TreeView.xaml
@@ -32,7 +32,6 @@
                         IsScrollChainingEnabled="{TemplateBinding (ScrollViewer.IsScrollChainingEnabled)}"
                         AllowAutoHide="{TemplateBinding (ScrollViewer.AllowAutoHide)}">
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
                             Margin="{TemplateBinding Padding}" />
           </ScrollViewer>
diff --git a/src/Avalonia.Themes.Fluent/Controls/TreeViewItem.xaml b/src/Avalonia.Themes.Fluent/Controls/TreeViewItem.xaml
index 9171791a0f0..834c2245a8e 100644
--- a/src/Avalonia.Themes.Fluent/Controls/TreeViewItem.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/TreeViewItem.xaml
@@ -95,7 +95,6 @@
           </Border>
           <ItemsPresenter Name="PART_ItemsPresenter"
                           IsVisible="{TemplateBinding IsExpanded}"
-                          Items="{TemplateBinding Items}"
                           ItemsPanel="{TemplateBinding ItemsPanel}" />
         </StackPanel>
       </ControlTemplate>
diff --git a/src/Avalonia.Themes.Simple/Controls/Carousel.xaml b/src/Avalonia.Themes.Simple/Controls/Carousel.xaml
index e79e3942c9c..66a4a1866a8 100644
--- a/src/Avalonia.Themes.Simple/Controls/Carousel.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/Carousel.xaml
@@ -10,7 +10,6 @@
                 CornerRadius="{TemplateBinding CornerRadius}">
           <CarouselPresenter Margin="{TemplateBinding Padding}"
                              IsVirtualized="{TemplateBinding IsVirtualized}"
-                             Items="{TemplateBinding Items}"
                              ItemsPanel="{TemplateBinding ItemsPanel}"
                              PageTransition="{TemplateBinding PageTransition}"
                              SelectedIndex="{TemplateBinding SelectedIndex}" />
diff --git a/src/Avalonia.Themes.Simple/Controls/ComboBox.xaml b/src/Avalonia.Themes.Simple/Controls/ComboBox.xaml
index d7dabae5164..1f4e48e4a8e 100644
--- a/src/Avalonia.Themes.Simple/Controls/ComboBox.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/ComboBox.xaml
@@ -62,10 +62,7 @@
                 <ScrollViewer HorizontalScrollBarVisibility="{TemplateBinding ScrollViewer.HorizontalScrollBarVisibility}"
                               VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}">
                   <ItemsPresenter Name="PART_ItemsPresenter"
-                                  ItemTemplate="{TemplateBinding ItemTemplate}"
-                                  Items="{TemplateBinding Items}"
-                                  ItemsPanel="{TemplateBinding ItemsPanel}"
-                                  VirtualizationMode="{TemplateBinding VirtualizationMode}" />
+                                  ItemsPanel="{TemplateBinding ItemsPanel}" />
                 </ScrollViewer>
               </Border>
             </Popup>
diff --git a/src/Avalonia.Themes.Simple/Controls/ContextMenu.xaml b/src/Avalonia.Themes.Simple/Controls/ContextMenu.xaml
index e99f1c5ac0c..3317178979b 100644
--- a/src/Avalonia.Themes.Simple/Controls/ContextMenu.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/ContextMenu.xaml
@@ -17,8 +17,6 @@
                 CornerRadius="{TemplateBinding CornerRadius}">
           <ScrollViewer Theme="{StaticResource SimpleMenuScrollViewer}">
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
                             KeyboardNavigation.TabNavigation="Continue" />
           </ScrollViewer>
diff --git a/src/Avalonia.Themes.Simple/Controls/ItemsControl.xaml b/src/Avalonia.Themes.Simple/Controls/ItemsControl.xaml
index d8cdf96abd5..d85cf193fa5 100644
--- a/src/Avalonia.Themes.Simple/Controls/ItemsControl.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/ItemsControl.xaml
@@ -10,8 +10,6 @@
                 BorderThickness="{TemplateBinding BorderThickness}"
                 CornerRadius="{TemplateBinding CornerRadius}">
           <ItemsPresenter Name="PART_ItemsPresenter"
-                          ItemTemplate="{TemplateBinding ItemTemplate}"
-                          Items="{TemplateBinding Items}"
                           ItemsPanel="{TemplateBinding ItemsPanel}" />
         </Border>
       </ControlTemplate>
diff --git a/src/Avalonia.Themes.Simple/Controls/ListBox.xaml b/src/Avalonia.Themes.Simple/Controls/ListBox.xaml
index 7308738681d..e1257ef10f7 100644
--- a/src/Avalonia.Themes.Simple/Controls/ListBox.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/ListBox.xaml
@@ -23,10 +23,7 @@
                         VerticalScrollBarVisibility="{TemplateBinding (ScrollViewer.VerticalScrollBarVisibility)}">
             <ItemsPresenter Name="PART_ItemsPresenter"
                             Margin="{TemplateBinding Padding}"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
-                            Items="{TemplateBinding Items}"
-                            ItemsPanel="{TemplateBinding ItemsPanel}"
-                            VirtualizationMode="{TemplateBinding VirtualizationMode}" />
+                            ItemsPanel="{TemplateBinding ItemsPanel}" />
           </ScrollViewer>
         </Border>
       </ControlTemplate>
diff --git a/src/Avalonia.Themes.Simple/Controls/Menu.xaml b/src/Avalonia.Themes.Simple/Controls/Menu.xaml
index 95b259bfa60..797aeedd233 100644
--- a/src/Avalonia.Themes.Simple/Controls/Menu.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/Menu.xaml
@@ -36,8 +36,6 @@
                   <ItemsPresenter Name="PART_ItemsPresenter"
                                   Margin="2"
                                   Grid.IsSharedSizeScope="True"
-                                  ItemTemplate="{TemplateBinding ItemTemplate}"
-                                  Items="{TemplateBinding Items}"
                                   ItemsPanel="{TemplateBinding ItemsPanel}" />
                 </ScrollViewer>
               </Border>
@@ -72,8 +70,6 @@
                 BorderThickness="{TemplateBinding BorderThickness}"
                 CornerRadius="{TemplateBinding CornerRadius}">
           <ItemsPresenter Name="PART_ItemsPresenter"
-                          ItemTemplate="{TemplateBinding ItemTemplate}"
-                          Items="{TemplateBinding Items}"
                           ItemsPanel="{TemplateBinding ItemsPanel}"
                           KeyboardNavigation.TabNavigation="Continue" />
         </Border>
diff --git a/src/Avalonia.Themes.Simple/Controls/MenuFlyoutPresenter.xaml b/src/Avalonia.Themes.Simple/Controls/MenuFlyoutPresenter.xaml
index d974c36d31a..05337d774fe 100644
--- a/src/Avalonia.Themes.Simple/Controls/MenuFlyoutPresenter.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/MenuFlyoutPresenter.xaml
@@ -20,8 +20,6 @@
             <ItemsPresenter Name="PART_ItemsPresenter"
                             Margin="{TemplateBinding Padding}"
                             Grid.IsSharedSizeScope="True"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
                             KeyboardNavigation.TabNavigation="Continue" />
           </ScrollViewer>
diff --git a/src/Avalonia.Themes.Simple/Controls/MenuItem.xaml b/src/Avalonia.Themes.Simple/Controls/MenuItem.xaml
index ec22ee413d7..de31f90d64a 100644
--- a/src/Avalonia.Themes.Simple/Controls/MenuItem.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/MenuItem.xaml
@@ -72,8 +72,6 @@
                   <ItemsPresenter Name="PART_ItemsPresenter"
                                   Margin="2"
                                   Grid.IsSharedSizeScope="True"
-                                  ItemTemplate="{TemplateBinding ItemTemplate}"
-                                  Items="{TemplateBinding Items}"
                                   ItemsPanel="{TemplateBinding ItemsPanel}" />
                 </ScrollViewer>
               </Border>
diff --git a/src/Avalonia.Themes.Simple/Controls/TabControl.xaml b/src/Avalonia.Themes.Simple/Controls/TabControl.xaml
index 4d1fcc0336e..c3cecb4fb82 100644
--- a/src/Avalonia.Themes.Simple/Controls/TabControl.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/TabControl.xaml
@@ -14,8 +14,6 @@
                 CornerRadius="{TemplateBinding CornerRadius}">
           <DockPanel>
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}" />
             <ContentPresenter Name="PART_SelectedContentHost"
                               Margin="{TemplateBinding Padding}"
diff --git a/src/Avalonia.Themes.Simple/Controls/TabStrip.xaml b/src/Avalonia.Themes.Simple/Controls/TabStrip.xaml
index 3960c1d275f..fd12eaa258d 100644
--- a/src/Avalonia.Themes.Simple/Controls/TabStrip.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/TabStrip.xaml
@@ -5,8 +5,6 @@
     <Setter Property="Template">
       <ControlTemplate>
         <ItemsPresenter Name="PART_ItemsPresenter"
-                        ItemTemplate="{TemplateBinding ItemTemplate}"
-                        Items="{TemplateBinding Items}"
                         ItemsPanel="{TemplateBinding ItemsPanel}" />
       </ControlTemplate>
     </Setter>
diff --git a/src/Avalonia.Themes.Simple/Controls/TreeView.xaml b/src/Avalonia.Themes.Simple/Controls/TreeView.xaml
index 2bc38a06735..8630c14aa23 100644
--- a/src/Avalonia.Themes.Simple/Controls/TreeView.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/TreeView.xaml
@@ -21,7 +21,6 @@
                         VerticalScrollBarVisibility="{TemplateBinding (ScrollViewer.VerticalScrollBarVisibility)}">
             <ItemsPresenter Name="PART_ItemsPresenter"
                             Margin="{TemplateBinding Padding}"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}" />
           </ScrollViewer>
         </Border>
diff --git a/src/Avalonia.Themes.Simple/Controls/TreeViewItem.xaml b/src/Avalonia.Themes.Simple/Controls/TreeViewItem.xaml
index 6ca3262419c..c36bf4c6737 100644
--- a/src/Avalonia.Themes.Simple/Controls/TreeViewItem.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/TreeViewItem.xaml
@@ -63,7 +63,6 @@
           </Border>
           <ItemsPresenter Name="PART_ItemsPresenter"
                           IsVisible="{TemplateBinding IsExpanded}"
-                          Items="{TemplateBinding Items}"
                           ItemsPanel="{TemplateBinding ItemsPanel}" />
         </StackPanel>
       </ControlTemplate>
diff --git a/tests/Avalonia.Controls.UnitTests/CarouselTests.cs b/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
index 76527b67e4f..1d9e5df74ac 100644
--- a/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
@@ -300,7 +300,6 @@ private Control CreateTemplate(Carousel control, INameScope scope)
             {
                 Name = "PART_ItemsPresenter",
                 [~CarouselPresenter.IsVirtualizedProperty] = control[~Carousel.IsVirtualizedProperty],
-                [~CarouselPresenter.ItemsProperty] = control[~Carousel.ItemsProperty],
                 [~CarouselPresenter.ItemsPanelProperty] = control[~Carousel.ItemsPanelProperty],
                 [~CarouselPresenter.SelectedIndexProperty] = control[~Carousel.SelectedIndexProperty],
                 [~CarouselPresenter.PageTransitionProperty] = control[~Carousel.PageTransitionProperty],
diff --git a/tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs b/tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs
index 1a8061bfd97..6eaef4c8490 100644
--- a/tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs
@@ -204,7 +204,6 @@ private static FuncControlTemplate GetTemplate()
                             Child = new ItemsPresenter
                             {
                                 Name = "PART_ItemsPresenter",
-                                [!ItemsPresenter.ItemsProperty] = parent[!ComboBox.ItemsProperty],
                             }.RegisterInNameScope(scope)
                         }.RegisterInNameScope(scope)
                     }
diff --git a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
index f803ea2d53f..ada5e10a7f4 100644
--- a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
@@ -544,7 +544,6 @@ public void Setting_Presenter_Explicitly_Should_Set_Item_Parent()
             var presenter = new ItemsPresenter
             {
                 [StyledElement.TemplatedParentProperty] = target,
-                [~ItemsPresenter.ItemsProperty] = target[~ItemsControl.ItemsProperty],
             };
 
             presenter.ApplyTemplate();
@@ -777,7 +776,6 @@ private static FuncControlTemplate GetTemplate()
                     Child = new ItemsPresenter
                     {
                         Name = "PART_ItemsPresenter",
-                        [~ItemsPresenter.ItemsProperty] = parent[~ItemsControl.ItemsProperty],
                     }.RegisterInNameScope(scope)
                 };
             });
@@ -785,7 +783,7 @@ private static FuncControlTemplate GetTemplate()
 
         private class TestItemsControl : ItemsControl
         {
-            public new IItemsPresenter Presenter
+            public new ItemsPresenter Presenter
             {
                 get { return base.Presenter; }
                 set { base.Presenter = value; }
diff --git a/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs b/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
index 2804078861a..b6375278b10 100644
--- a/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
@@ -1,3 +1,4 @@
+using System;
 using System.Collections.ObjectModel;
 using System.Linq;
 using System.Reactive.Subjects;
@@ -330,38 +331,39 @@ private void RaisePressedEvent(ListBox listBox, ListBoxItem item, MouseButton mo
         [Fact]
         public void ListBox_After_Scroll_IndexOutOfRangeException_Shouldnt_Be_Thrown()
         {
-            using (UnitTestApplication.Start(TestServices.StyledWindow))
-            {
-                var items = Enumerable.Range(0, 11).Select(x => $"{x}").ToArray();
+            throw new NotImplementedException();
+            ////using (UnitTestApplication.Start(TestServices.StyledWindow))
+            ////{
+            ////    var items = Enumerable.Range(0, 11).Select(x => $"{x}").ToArray();
 
-                var target = new ListBox
-                {
-                    Template = ListBoxTemplate(),
-                    Items = items,
-                    ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 11 })
-                };
+            ////    var target = new ListBox
+            ////    {
+            ////        Template = ListBoxTemplate(),
+            ////        Items = items,
+            ////        ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 11 })
+            ////    };
 
-                Prepare(target);
+            ////    Prepare(target);
 
-                var panel = target.Presenter.Panel as IVirtualizingPanel;
+            ////    var panel = target.Presenter.Panel as IVirtualizingPanel;
 
-                var listBoxItems = panel.Children.OfType<ListBoxItem>();
+            ////    var listBoxItems = panel.Children.OfType<ListBoxItem>();
 
-                //virtualization should have created exactly 10 items
-                Assert.Equal(10, listBoxItems.Count());
-                Assert.Equal("0", listBoxItems.First().DataContext);
-                Assert.Equal("9", listBoxItems.Last().DataContext);
+            ////    //virtualization should have created exactly 10 items
+            ////    Assert.Equal(10, listBoxItems.Count());
+            ////    Assert.Equal("0", listBoxItems.First().DataContext);
+            ////    Assert.Equal("9", listBoxItems.Last().DataContext);
 
-                //instead pixeloffset > 0 there could be pretty complex sequence for repro
-                //it involves add/remove/scroll to end multiple actions
-                //which i can't find so far :(, but this is the simplest way to add it to unit test
-                panel.PixelOffset = 1;
+            ////    //instead pixeloffset > 0 there could be pretty complex sequence for repro
+            ////    //it involves add/remove/scroll to end multiple actions
+            ////    //which i can't find so far :(, but this is the simplest way to add it to unit test
+            ////    panel.PixelOffset = 1;
 
-                //here scroll to end -> IndexOutOfRangeException is thrown
-                target.Scroll.Offset = new Vector(0, 2);
+            ////    //here scroll to end -> IndexOutOfRangeException is thrown
+            ////    target.Scroll.Offset = new Vector(0, 2);
 
-                Assert.True(true);
-            }
+            ////    Assert.True(true);
+            ////}
         }
 
         [Fact]
@@ -600,9 +602,7 @@ private static FuncControlTemplate ListBoxTemplate()
                     Content = new ItemsPresenter
                     {
                         Name = "PART_ItemsPresenter",
-                        [~ItemsPresenter.ItemsProperty] = parent.GetObservable(ItemsControl.ItemsProperty).ToBinding(),
                         [~ItemsPresenter.ItemsPanelProperty] = parent.GetObservable(ItemsControl.ItemsPanelProperty).ToBinding(),
-                        [~ItemsPresenter.VirtualizationModeProperty] = parent.GetObservable(ListBox.VirtualizationModeProperty).ToBinding(),
                     }.RegisterInNameScope(scope)
                 }.RegisterInNameScope(scope));
         }
diff --git a/tests/Avalonia.Controls.UnitTests/ListBoxTests_Multiple.cs b/tests/Avalonia.Controls.UnitTests/ListBoxTests_Multiple.cs
index 87d45fa1063..b358c98a620 100644
--- a/tests/Avalonia.Controls.UnitTests/ListBoxTests_Multiple.cs
+++ b/tests/Avalonia.Controls.UnitTests/ListBoxTests_Multiple.cs
@@ -93,7 +93,6 @@ private Control CreateListBoxTemplate(TemplatedControl parent, INameScope scope)
                 Content = new ItemsPresenter
                 {
                     Name = "PART_ItemsPresenter",
-                    [~ItemsPresenter.ItemsProperty] = ((Control)parent).GetObservable(ItemsControl.ItemsProperty).ToBinding(),
                 }.RegisterInNameScope(scope)
             };
         }
diff --git a/tests/Avalonia.Controls.UnitTests/ListBoxTests_Single.cs b/tests/Avalonia.Controls.UnitTests/ListBoxTests_Single.cs
index 03aac5e2f4d..cb4e81001fc 100644
--- a/tests/Avalonia.Controls.UnitTests/ListBoxTests_Single.cs
+++ b/tests/Avalonia.Controls.UnitTests/ListBoxTests_Single.cs
@@ -324,7 +324,6 @@ private Control CreateListBoxTemplate(TemplatedControl parent, INameScope scope)
                 Content = new ItemsPresenter
                 {
                     Name = "PART_ItemsPresenter",
-                    [~ItemsPresenter.ItemsProperty] = parent.GetObservable(ItemsControl.ItemsProperty).ToBinding(),
                 }.RegisterInNameScope(scope)
             };
         }
diff --git a/tests/Avalonia.Controls.UnitTests/Presenters/CarouselPresenterTests.cs b/tests/Avalonia.Controls.UnitTests/Presenters/CarouselPresenterTests.cs
index 1408b8760b1..f5094accb58 100644
--- a/tests/Avalonia.Controls.UnitTests/Presenters/CarouselPresenterTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Presenters/CarouselPresenterTests.cs
@@ -1,732 +1,732 @@
-using System.Linq;
-using Moq;
-using Avalonia.Controls.Generators;
-using Avalonia.Controls.Presenters;
-using Avalonia.Controls.Templates;
-using Xunit;
-using System.Collections.ObjectModel;
-using System.Collections;
-
-namespace Avalonia.Controls.UnitTests.Presenters
-{
-    public class CarouselPresenterTests
-    {
-        [Fact]
-        public void Should_Register_With_Host_When_TemplatedParent_Set()
-        {
-            var host = new Carousel();
-            var target = new CarouselPresenter();
-
-            Assert.Null(host.Presenter);
-
-            target.SetValue(Control.TemplatedParentProperty, host);
-
-            Assert.Same(target, host.Presenter);
-        }
-
-        [Fact]
-        public void ApplyTemplate_Should_Create_Panel()
-        {
-            var target = new CarouselPresenter
-            {
-                ItemsPanel = new FuncTemplate<Panel>(() => new Panel()),
-            };
-
-            target.ApplyTemplate();
-
-            Assert.IsType<Panel>(target.Panel);
-        }
-
-        [Fact]
-        public void ItemContainerGenerator_Should_Be_Picked_Up_From_TemplatedControl()
-        {
-            var parent = new TestItemsControl();
-            var target = new CarouselPresenter
-            {
-                [StyledElement.TemplatedParentProperty] = parent,
-            };
-
-            Assert.IsType<ItemContainerGenerator<TestItem>>(target.ItemContainerGenerator);
-        }
-
-        public class Virtualized
-        {
-            [Fact]
-            public void Should_Initially_Materialize_Selected_Container()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    SelectedIndex = 0,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Should_Initially_Materialize_Nothing_If_No_Selected_Container()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                Assert.Empty(target.Panel.Children);
-                Assert.Empty(target.ItemContainerGenerator.Containers);
-            }
-
-            [Fact]
-            public void Switching_To_Virtualized_Should_Reset_Containers()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    SelectedIndex = 0,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-                target.IsVirtualized = true;
-
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Changing_SelectedIndex_Should_Show_Page()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    SelectedIndex = 0,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-                AssertSingle(target);
-
-                target.SelectedIndex = 1;
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Should_Remove_NonCurrent_Page()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    IsVirtualized = true,
-                    SelectedIndex = 0,
-                };
-
-                target.ApplyTemplate();
-                AssertSingle(target);
-
-                target.SelectedIndex = 1;
-                AssertSingle(target);
-
-            }
-
-            [Fact]
-            public void Should_Handle_Inserting_Item_At_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                items.Insert(1, "item1a");
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Inserting_Item_Before_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 2,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                items.Insert(1, "item1a");
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Should_Do_Nothing_When_Inserting_Item_After_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-                var child = AssertSingle(target);
-                items.Insert(2, "after");
-                Assert.Same(child, AssertSingle(target));
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_Item_At_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                items.RemoveAt(1);
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_Item_Before_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                items.RemoveAt(0);
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Should_Do_Nothing_When_Removing_Item_After_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-                var child = AssertSingle(target);
-                items.RemoveAt(2);
-                Assert.Same(child, AssertSingle(target));
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_SelectedItem_When_Its_Last()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 2,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                items.RemoveAt(2);
-                Assert.Equal(1, target.SelectedIndex);
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_Last_Item()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 0,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                items.RemoveAt(0);
-                Assert.Empty(target.Panel.Children);
-                Assert.Empty(target.ItemContainerGenerator.Containers);
-            }
-
-            [Fact]
-            public void Should_Handle_Replacing_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                items[1] = "replaced";
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Should_Do_Nothing_When_Replacing_Non_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-                var child = AssertSingle(target);
-                items[0] = "replaced";
-                Assert.Same(child, AssertSingle(target));
-            }
-
-            [Fact]
-            public void Should_Handle_Moving_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                items.Move(1, 0);
-                AssertSingle(target);
-            }
-
-            private static Control AssertSingle(CarouselPresenter target)
-            {
-                var items = (IList)target.Items;
-                var index = target.SelectedIndex;
-                var content = items[index];
-                var child = Assert.Single(target.Panel.Children);
-                var presenter = Assert.IsType<ContentPresenter>(child);
-                var container = Assert.Single(target.ItemContainerGenerator.Containers);
-                var visible = Assert.Single(target.Panel.Children.Where(x => x.IsVisible));
-
-                Assert.Same(child, container.ContainerControl);
-                Assert.Same(child, visible);
-                Assert.Equal(content, presenter.Content);
-                Assert.Equal(content, container.Item);
-                Assert.Equal(index, container.Index);
-
-                return child;
-            }
-        }
-
-        public class NonVirtualized
-        {
-            [Fact]
-            public void Should_Initially_Materialize_All_Containers()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Initially_Show_Selected_Item()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    SelectedIndex = 1,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Switching_To_Non_Virtualized_Should_Reset_Containers()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    SelectedIndex = 0,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-                target.IsVirtualized = false;
-
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Changing_SelectedIndex_Should_Show_Page()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    SelectedIndex = 0,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-                AssertAll(target);
-
-                target.SelectedIndex = 1;
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Inserting_Item_At_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-
-                items.Insert(1, "item1a");
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Inserting_Item_Before_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 2,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-
-                items.Insert(1, "item1a");
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Do_Handle_Inserting_Item_After_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-                items.Insert(2, "after");
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_Item_At_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-
-                items.RemoveAt(1);
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_Item_Before_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-
-                items.RemoveAt(0);
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_Item_After_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-                items.RemoveAt(2);
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_SelectedItem_When_Its_Last()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 2,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-
-                items.RemoveAt(2);
-                Assert.Equal(1, target.SelectedIndex);
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_Last_Item()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 0,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-
-                items.RemoveAt(0);
-                Assert.Empty(target.Panel.Children);
-                Assert.Empty(target.ItemContainerGenerator.Containers);
-            }
-
-            [Fact]
-            public void Should_Handle_Replacing_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-
-                items[1] = "replaced";
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Moving_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-
-                items.Move(1, 0);
-                AssertAll(target);
-            }
-
-            private static void AssertAll(CarouselPresenter target)
-            {
-                var items = (IList)target.Items;
-
-                Assert.Equal(items?.Count ?? 0, target.Panel.Children.Count);
-                Assert.Equal(items?.Count ?? 0, target.ItemContainerGenerator.Containers.Count());
-
-                for (var i = 0; i < items?.Count; ++i)
-                {
-                    var content = items[i];
-                    var child = target.Panel.Children[i];
-                    var presenter = Assert.IsType<ContentPresenter>(child);
-                    var container = target.ItemContainerGenerator.ContainerFromIndex(i);
-
-                    Assert.Same(child, container);
-                    Assert.Equal(i == target.SelectedIndex, child.IsVisible);
-                    Assert.Equal(content, presenter.Content);
-                    Assert.Equal(i, target.ItemContainerGenerator.IndexFromContainer(container));
-                }
-            }
-        }
-
-        private class TestItem : ContentControl
-        {
-        }
-
-        private class TestItemsControl : ItemsControl
-        {
-            protected override IItemContainerGenerator CreateItemContainerGenerator()
-            {
-                return new ItemContainerGenerator<TestItem>(this, TestItem.ContentProperty, null);
-            }
-        }
-    }
-}
+////using System.Linq;
+////using Moq;
+////using Avalonia.Controls.Generators;
+////using Avalonia.Controls.Presenters;
+////using Avalonia.Controls.Templates;
+////using Xunit;
+////using System.Collections.ObjectModel;
+////using System.Collections;
+
+////namespace Avalonia.Controls.UnitTests.Presenters
+////{
+////    public class CarouselPresenterTests
+////    {
+////        [Fact]
+////        public void Should_Register_With_Host_When_TemplatedParent_Set()
+////        {
+////            var host = new Carousel();
+////            var target = new CarouselPresenter();
+
+////            Assert.Null(host.Presenter);
+
+////            target.SetValue(Control.TemplatedParentProperty, host);
+
+////            Assert.Same(target, host.Presenter);
+////        }
+
+////        [Fact]
+////        public void ApplyTemplate_Should_Create_Panel()
+////        {
+////            var target = new CarouselPresenter
+////            {
+////                ItemsPanel = new FuncTemplate<Panel>(() => new Panel()),
+////            };
+
+////            target.ApplyTemplate();
+
+////            Assert.IsType<Panel>(target.Panel);
+////        }
+
+////        [Fact]
+////        public void ItemContainerGenerator_Should_Be_Picked_Up_From_TemplatedControl()
+////        {
+////            var parent = new TestItemsControl();
+////            var target = new CarouselPresenter
+////            {
+////                [StyledElement.TemplatedParentProperty] = parent,
+////            };
+
+////            Assert.IsType<ItemContainerGenerator<TestItem>>(target.ItemContainerGenerator);
+////        }
+
+////        public class Virtualized
+////        {
+////            [Fact]
+////            public void Should_Initially_Materialize_Selected_Container()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    SelectedIndex = 0,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Should_Initially_Materialize_Nothing_If_No_Selected_Container()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                Assert.Empty(target.Panel.Children);
+////                Assert.Empty(target.ItemContainerGenerator.Containers);
+////            }
+
+////            [Fact]
+////            public void Switching_To_Virtualized_Should_Reset_Containers()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    SelectedIndex = 0,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+////                target.IsVirtualized = true;
+
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Changing_SelectedIndex_Should_Show_Page()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    SelectedIndex = 0,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+////                AssertSingle(target);
+
+////                target.SelectedIndex = 1;
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Should_Remove_NonCurrent_Page()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    IsVirtualized = true,
+////                    SelectedIndex = 0,
+////                };
+
+////                target.ApplyTemplate();
+////                AssertSingle(target);
+
+////                target.SelectedIndex = 1;
+////                AssertSingle(target);
+
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Inserting_Item_At_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.Insert(1, "item1a");
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Inserting_Item_Before_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 2,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.Insert(1, "item1a");
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Should_Do_Nothing_When_Inserting_Item_After_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+////                var child = AssertSingle(target);
+////                items.Insert(2, "after");
+////                Assert.Same(child, AssertSingle(target));
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_Item_At_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.RemoveAt(1);
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_Item_Before_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.RemoveAt(0);
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Should_Do_Nothing_When_Removing_Item_After_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+////                var child = AssertSingle(target);
+////                items.RemoveAt(2);
+////                Assert.Same(child, AssertSingle(target));
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_SelectedItem_When_Its_Last()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 2,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.RemoveAt(2);
+////                Assert.Equal(1, target.SelectedIndex);
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_Last_Item()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 0,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.RemoveAt(0);
+////                Assert.Empty(target.Panel.Children);
+////                Assert.Empty(target.ItemContainerGenerator.Containers);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Replacing_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items[1] = "replaced";
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Should_Do_Nothing_When_Replacing_Non_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+////                var child = AssertSingle(target);
+////                items[0] = "replaced";
+////                Assert.Same(child, AssertSingle(target));
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Moving_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.Move(1, 0);
+////                AssertSingle(target);
+////            }
+
+////            private static Control AssertSingle(CarouselPresenter target)
+////            {
+////                var items = (IList)target.Items;
+////                var index = target.SelectedIndex;
+////                var content = items[index];
+////                var child = Assert.Single(target.Panel.Children);
+////                var presenter = Assert.IsType<ContentPresenter>(child);
+////                var container = Assert.Single(target.ItemContainerGenerator.Containers);
+////                var visible = Assert.Single(target.Panel.Children.Where(x => x.IsVisible));
+
+////                Assert.Same(child, container.ContainerControl);
+////                Assert.Same(child, visible);
+////                Assert.Equal(content, presenter.Content);
+////                Assert.Equal(content, container.Item);
+////                Assert.Equal(index, container.Index);
+
+////                return child;
+////            }
+////        }
+
+////        public class NonVirtualized
+////        {
+////            [Fact]
+////            public void Should_Initially_Materialize_All_Containers()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Initially_Show_Selected_Item()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    SelectedIndex = 1,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Switching_To_Non_Virtualized_Should_Reset_Containers()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    SelectedIndex = 0,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+////                target.IsVirtualized = false;
+
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Changing_SelectedIndex_Should_Show_Page()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    SelectedIndex = 0,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+////                AssertAll(target);
+
+////                target.SelectedIndex = 1;
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Inserting_Item_At_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.Insert(1, "item1a");
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Inserting_Item_Before_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 2,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.Insert(1, "item1a");
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Do_Handle_Inserting_Item_After_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+////                items.Insert(2, "after");
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_Item_At_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.RemoveAt(1);
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_Item_Before_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.RemoveAt(0);
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_Item_After_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+////                items.RemoveAt(2);
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_SelectedItem_When_Its_Last()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 2,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.RemoveAt(2);
+////                Assert.Equal(1, target.SelectedIndex);
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_Last_Item()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 0,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.RemoveAt(0);
+////                Assert.Empty(target.Panel.Children);
+////                Assert.Empty(target.ItemContainerGenerator.Containers);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Replacing_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items[1] = "replaced";
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Moving_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.Move(1, 0);
+////                AssertAll(target);
+////            }
+
+////            private static void AssertAll(CarouselPresenter target)
+////            {
+////                var items = (IList)target.Items;
+
+////                Assert.Equal(items?.Count ?? 0, target.Panel.Children.Count);
+////                Assert.Equal(items?.Count ?? 0, target.ItemContainerGenerator.Containers.Count());
+
+////                for (var i = 0; i < items?.Count; ++i)
+////                {
+////                    var content = items[i];
+////                    var child = target.Panel.Children[i];
+////                    var presenter = Assert.IsType<ContentPresenter>(child);
+////                    var container = target.ItemContainerGenerator.ContainerFromIndex(i);
+
+////                    Assert.Same(child, container);
+////                    Assert.Equal(i == target.SelectedIndex, child.IsVisible);
+////                    Assert.Equal(content, presenter.Content);
+////                    Assert.Equal(i, target.ItemContainerGenerator.IndexFromContainer(container));
+////                }
+////            }
+////        }
+
+////        private class TestItem : ContentControl
+////        {
+////        }
+
+////        private class TestItemsControl : ItemsControl
+////        {
+////            protected override IItemContainerGenerator CreateItemContainerGenerator()
+////            {
+////                return new ItemContainerGenerator<TestItem>(this, TestItem.ContentProperty, null);
+////            }
+////        }
+////    }
+////}
diff --git a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests.cs b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests.cs
index 7024b1dde82..71f803fab7f 100644
--- a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests.cs
@@ -1,14 +1,15 @@
+using System;
+using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Linq;
-using Moq;
-using Avalonia.Collections;
-using Avalonia.Controls.Generators;
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Templates;
-using Avalonia.Input;
+using Avalonia.UnitTests;
 using Avalonia.VisualTree;
 using Xunit;
 
+#nullable enable
+
 namespace Avalonia.Controls.UnitTests.Presenters
 {
     public class ItemsPresenterTests
@@ -27,327 +28,126 @@ public void Should_Register_With_Host_When_TemplatedParent_Set()
         }
 
         [Fact]
-        public void Should_Add_Containers()
-        {
-            var target = new ItemsPresenter
-            {
-                Items = new[] { "foo", "bar" },
-            };
-
-            target.ApplyTemplate();
-
-            Assert.Equal(2, target.Panel.Children.Count);
-            Assert.IsType<ContentPresenter>(target.Panel.Children[0]);
-            Assert.IsType<ContentPresenter>(target.Panel.Children[1]);
-            Assert.Equal("foo", ((ContentPresenter)target.Panel.Children[0]).Content);
-            Assert.Equal("bar", ((ContentPresenter)target.Panel.Children[1]).Content);
-        }
-
-        [Fact]
-        public void Should_Add_Containers_Of_Correct_Type()
-        {
-            var target = new ItemsPresenter
-            {
-                Items = new[] { "foo", "bar" },
-            };
-
-            target.ItemContainerGenerator = new ItemContainerGenerator<ListBoxItem>(
-                target, 
-                ListBoxItem.ContentProperty,
-                null);
-            target.ApplyTemplate();
-
-            Assert.Equal(2, target.Panel.Children.Count);
-            Assert.IsType<ListBoxItem>(target.Panel.Children[0]);
-            Assert.IsType<ListBoxItem>(target.Panel.Children[1]);
-        }
-
-        [Fact]
-        public void Should_Create_Containers_Only_Once()
-        {
-            var parent = new TestItemsControl();
-            var target = new ItemsPresenter
-            {
-                Items = new[] { "foo", "bar" },
-                [StyledElement.TemplatedParentProperty] = parent,
-            };
-            var raised = 0;
-
-            parent.ItemContainerGenerator.Materialized += (s, e) => ++raised;
-
-            target.ApplyTemplate();
-
-            Assert.Equal(2, target.Panel.Children.Count);
-            Assert.Equal(2, raised);
-        }
-
-        [Fact]
-        public void ItemContainerGenerator_Should_Be_Picked_Up_From_TemplatedControl()
-        {
-            var parent = new TestItemsControl();
-            var target = new ItemsPresenter
-            {
-                [StyledElement.TemplatedParentProperty] = parent,
-            };
-
-            Assert.IsType<ItemContainerGenerator<TestItem>>(target.ItemContainerGenerator);
-        }
-
-        [Fact]
-        public void Should_Remove_Containers()
+        public void Panel_Should_Be_Visual_Child()
         {
-            var items = new AvaloniaList<string>(new[] { "foo", "bar" });
-            var target = new ItemsPresenter
-            {
-                Items = items,
-            };
-
-            target.ApplyTemplate();
-            items.RemoveAt(0);
+            var (target, _, _) = CreateTarget();
+            var child = target.GetVisualChildren().Single();
 
-            Assert.Single(target.Panel.Children);
-            Assert.Equal("bar", ((ContentPresenter)target.Panel.Children[0]).Content);
-            Assert.Equal("bar", ((ContentPresenter)target.ItemContainerGenerator.ContainerFromIndex(0)).Content);
+            Assert.Equal(target.Panel, child);
         }
 
-        [Fact]
-        public void Clearing_Items_Should_Remove_Containers()
+        public class NonVirtualizingPanel
         {
-            var items = new ObservableCollection<string> { "foo", "bar" };
-            var target = new ItemsPresenter
+            [Fact]
+            public void Creates_Containers_For_Initial_Items()
             {
-                Items = items,
-            };
+                using var app = Start();
+                var items = new[] { "foo", "bar", "baz" };
+                var (target, _, _) = CreateTarget(items);
+                var panel = Assert.IsType<StackPanel>(target.Panel);
 
-            target.ApplyTemplate();
-            items.Clear();
-
-            Assert.Empty(target.Panel.Children);
-            Assert.Empty(target.ItemContainerGenerator.Containers);
-        }
+                AssertContainers(panel, items);
+            }
 
-        [Fact]
-        public void Replacing_Items_Should_Update_Containers()
-        {
-            var items = new ObservableCollection<string> { "foo", "bar", "baz" };
-            var target = new ItemsPresenter
+            [Fact]
+            public void Creates_Containers_For_Inserted_Items()
             {
-                Items = items,
-            };
+                using var app = Start();
+                var items = new ObservableCollection<string>(new[] { "foo", "bar", "baz" });
+                var (target, _, root) = CreateTarget(items);
+                var panel = Assert.IsType<StackPanel>(target.Panel);
 
-            target.ApplyTemplate();
-            items[1] = "baz";
+                items.Insert(1, "foo2");
+                root.LayoutManager.ExecuteLayoutPass();
 
-            var text = target.Panel.Children
-                .OfType<ContentPresenter>()
-                .Select(x => x.Content)
-                .ToList();
-
-            Assert.Equal(new[] { "foo", "baz", "baz" }, text);
-        }
+                AssertContainers(panel, items);
+            }
 
-        [Fact]
-        public void Moving_Items_Should_Update_Containers()
-        {
-            var items = new ObservableCollection<string> { "foo", "bar", "baz" };
-            var target = new ItemsPresenter
+            [Fact]
+            public void Removes_Containers_For_Removed_Items()
             {
-                Items = items,
-            };
+                using var app = Start();
+                var items = new ObservableCollection<string>(new[] { "foo", "bar", "baz" });
+                var (target, _, root) = CreateTarget(items);
+                var panel = Assert.IsType<StackPanel>(target.Panel);
 
-            target.ApplyTemplate();
-            items.Move(2, 1);
+                items.RemoveAt(1);
+                root.LayoutManager.ExecuteLayoutPass();
 
-            var text = target.Panel.Children
-                .OfType<ContentPresenter>()
-                .Select(x => x.Content)
-                .ToList();
-
-            Assert.Equal(new[] { "foo", "baz", "bar" }, text);
-        }
+                AssertContainers(panel, items);
+            }
 
-        [Fact]
-        public void Inserting_Items_Should_Update_Containers()
-        {
-            var items = new ObservableCollection<string> { "foo", "bar", "baz" };
-            var target = new ItemsPresenter
+            [Fact]
+            public void Updates_Containers_For_Moved_Items()
             {
-                Items = items,
-            };
-
-            target.ApplyTemplate();
-            items.Insert(2, "insert");
-
-            var text = target.Panel.Children
-                .OfType<ContentPresenter>()
-                .Select(x => x.Content)
-                .ToList();
-
-            Assert.Equal(new[] { "foo", "bar", "insert", "baz" }, text);
-        }
+                using var app = Start();
+                var items = new ObservableCollection<string>(new[] { "foo", "bar", "baz" });
+                var (target, _, root) = CreateTarget(items);
+                var panel = Assert.IsType<StackPanel>(target.Panel);
 
-        [Fact]
-        public void Setting_Items_To_Null_Should_Remove_Containers()
-        {
-            var target = new ItemsPresenter
-            {
-                Items = new[] { "foo", "bar" },
-            };
+                items.Move(0, 2);
+                root.LayoutManager.ExecuteLayoutPass();
 
-            target.ApplyTemplate();
-            target.Items = null;
-
-            Assert.Empty(target.Panel.Children);
-            Assert.Empty(target.ItemContainerGenerator.Containers);
-        }
-
-        [Fact]
-        public void Should_Handle_Null_Items()
-        {
-            var items = new AvaloniaList<string>(new[] { "foo", null, "bar" });
+                AssertContainers(panel, items);
+            }
 
-            var target = new ItemsPresenter
+            [Fact]
+            public void Updates_Containers_For_Replaced_Items()
             {
-                Items = items,
-            };
-
-            target.ApplyTemplate();
+                using var app = Start();
+                var items = new ObservableCollection<string>(new[] { "foo", "bar", "baz" });
+                var (target, _, root) = CreateTarget(items);
+                var panel = Assert.IsType<StackPanel>(target.Panel);
 
-            var text = target.Panel.Children.Cast<ContentPresenter>().Select(x => x.Content).ToList();
+                items[1] = "bar2";
+                root.LayoutManager.ExecuteLayoutPass();
 
-            Assert.Equal(new[] { "foo", null, "bar" }, text);
-            Assert.NotNull(target.ItemContainerGenerator.ContainerFromIndex(0));
-            Assert.NotNull(target.ItemContainerGenerator.ContainerFromIndex(1));
-            Assert.NotNull(target.ItemContainerGenerator.ContainerFromIndex(2));
-
-            items.RemoveAt(1);
-
-            text = target.Panel.Children.Cast<ContentPresenter>().Select(x => x.Content).ToList();
-
-            Assert.Equal(new[] { "foo", "bar" }, text);
-            Assert.NotNull(target.ItemContainerGenerator.ContainerFromIndex(0));
-            Assert.NotNull(target.ItemContainerGenerator.ContainerFromIndex(1));
-        }
+                AssertContainers(panel, items);
+            }
 
-        [Fact]
-        public void Inserting_Then_Removing_Should_Add_Remove_Containers()
-        {
-            var items = new AvaloniaList<string>(Enumerable.Range(0, 5).Select(x => $"Item {x}"));
-            var toAdd = Enumerable.Range(0, 3).Select(x => $"Added Item {x}").ToArray();
-            var target = new ItemsPresenter
+            [Fact]
+            public void Updates_Containers_On_Items_Changed()
             {
-                VirtualizationMode = ItemVirtualizationMode.None,
-                Items = items,
-                ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 10 }),
-            };
+                using var app = Start();
+                var items = new ObservableCollection<string>(new[] { "foo", "bar", "baz" });
+                var (target, itemsControl, root) = CreateTarget(items);
+                var panel = Assert.IsType<StackPanel>(target.Panel);
 
-            target.ApplyTemplate();
+                var newItems = new[] { "qux", "quux", "corge" };
+                itemsControl.Items = newItems;
+                root.LayoutManager.ExecuteLayoutPass();
 
-            Assert.Equal(items.Count, target.Panel.Children.Count);
-
-            foreach (var item in toAdd)
-            {
-                items.Insert(1, item);
+                AssertContainers(panel, newItems);
             }
 
-            Assert.Equal(items.Count, target.Panel.Children.Count);
-
-            foreach (var item in toAdd)
+            private static void AssertContainers(StackPanel panel, IReadOnlyList<string> items)
             {
-                items.Remove(item);
-            }
+                Assert.Equal(items.Count, panel.Children.Count);
 
-            Assert.Equal(items.Count, target.Panel.Children.Count);
+                for (var i = 0; i < items.Count; i++)
+                {
+                    var container = Assert.IsType<ContentPresenter>(panel.Children[i]);
+                    Assert.Equal(items[i], container.DataContext);
+                    Assert.Equal(items[i], container.Content);
+                }
+            }
         }
 
-        [Fact]
-        public void Should_Handle_Duplicate_Items()
+        private static (ItemsPresenter, ItemsControl, TestRoot) CreateTarget(IReadOnlyList<string>? items = null)
         {
-            var items = new AvaloniaList<int>(new[] { 1, 2, 1 });
+            var result = new ItemsPresenter();
 
-            var target = new ItemsPresenter
+            var itemsControl = new ItemsControl
             {
                 Items = items,
+                Template = new FuncControlTemplate<ItemsControl>((_, _) => result)
             };
 
-            target.ApplyTemplate();
-            items.RemoveAt(2);
-
-            var numbers = target.Panel.Children
-                .OfType<ContentPresenter>()
-                .Select(x => x.Content)
-                .Cast<int>();
-            Assert.Equal(new[] { 1, 2 }, numbers);
-        }
-
-        [Fact]
-        public void Panel_Should_Be_Created_From_ItemsPanel_Template()
-        {
-            var panel = new Panel();
-            var target = new ItemsPresenter
-            {
-                ItemsPanel = new FuncTemplate<Panel>(() => panel),
-            };
-
-            target.ApplyTemplate();
-
-            Assert.Same(panel, target.Panel);
-            Assert.Same(target, target.Panel.Parent);
+            var root = new TestRoot(itemsControl);
+            root.LayoutManager.ExecuteInitialLayoutPass();
+            return (result, itemsControl, root);
         }
 
-        [Fact]
-        public void Panel_TabNavigation_Should_Be_Set_To_Once()
-        {
-            var target = new ItemsPresenter();
-
-            target.ApplyTemplate();
-
-            Assert.Equal(KeyboardNavigationMode.Once, KeyboardNavigation.GetTabNavigation((InputElement)target.Panel));
-        }
-
-        [Fact]
-        public void Panel_TabNavigation_Should_Be_Set_To_ItemsPresenter_Value()
-        {
-            var target = new ItemsPresenter();
-
-            KeyboardNavigation.SetTabNavigation(target, KeyboardNavigationMode.Cycle);
-            target.ApplyTemplate();
-
-            Assert.Equal(KeyboardNavigationMode.Cycle, KeyboardNavigation.GetTabNavigation((InputElement)target.Panel));
-        }
-
-        [Fact]
-        public void Panel_Should_Be_Visual_Child()
-        {
-            var target = new ItemsPresenter();
-
-            target.ApplyTemplate();
-
-            var child = target.GetVisualChildren().Single();
-
-            Assert.Equal(target.Panel, child);
-        }
-
-        private class Item
-        {
-            public Item(string value)
-            {
-                Value = value;
-            }
-
-            public string Value { get; }
-        }
-
-        private class TestItem : ContentControl
-        {
-        }
-
-        private class TestItemsControl : ItemsControl
-        {
-            protected override IItemContainerGenerator CreateItemContainerGenerator()
-            {
-                return new ItemContainerGenerator<TestItem>(this, TestItem.ContentProperty, null);
-            }
-        }
+        private static IDisposable Start() => UnitTestApplication.Start(TestServices.MockPlatformRenderInterface);
     }
 }
diff --git a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization.cs b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization.cs
index bf3d838849b..d0798d469f5 100644
--- a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization.cs
+++ b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization.cs
@@ -1,374 +1,374 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using Avalonia.Controls.Generators;
-using Avalonia.Controls.Presenters;
-using Avalonia.Controls.Primitives;
-using Avalonia.Controls.Templates;
-using Avalonia.Layout;
-using Avalonia.Platform;
-using Avalonia.Rendering;
-using Avalonia.UnitTests;
-using Avalonia.VisualTree;
-using Xunit;
-
-namespace Avalonia.Controls.UnitTests.Presenters
-{
-    public class ItemsPresenterTests_Virtualization
-    {
-        [Fact]
-        public void Should_Not_Create_Items_Before_Added_To_Visual_Tree()
-        {
-            var items = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-            var target = new TestItemsPresenter(true)
-            {
-                Items = items,
-                ItemsPanel = VirtualizingPanelTemplate(Orientation.Vertical),
-                ItemTemplate = ItemTemplate(),
-                VirtualizationMode = ItemVirtualizationMode.Simple,
-            };
-
-            var scroller = new ScrollContentPresenter
-            {
-                Content = target,
-            };
-
-            scroller.UpdateChild();
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Empty(target.Panel.Children);
-
-            var root = new TestRoot
-            {
-                Child = scroller,
-            };
-
-            target.InvalidateMeasure();
-            target.Panel.InvalidateMeasure();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(10, target.Panel.Children.Count);
-        }
-
-        [Fact]
-        public void Should_Return_IsLogicalScrollEnabled_False_When_Has_No_Virtualizing_Panel()
-        {
-            var target = CreateTarget();
-            target.ClearValue(ItemsPresenter.ItemsPanelProperty);
-
-            target.ApplyTemplate();
-
-            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
-        }
-
-        [Fact]
-        public void Should_Return_IsLogicalScrollEnabled_False_When_VirtualizationMode_None()
-        {
-            var target = CreateTarget(ItemVirtualizationMode.None);
-
-            target.ApplyTemplate();
-
-            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
-        }
-
-        [Fact]
-        public void Should_Return_IsLogicalScrollEnabled_False_When_Doesnt_Have_ScrollPresenter_Parent()
-        {
-            var target = new ItemsPresenter
-            {
-                ItemsPanel = VirtualizingPanelTemplate(),
-                ItemTemplate = ItemTemplate(),
-                VirtualizationMode = ItemVirtualizationMode.Simple,
-            };
-
-            target.ApplyTemplate();
-
-            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
-        }
-
-        [Fact]
-        public void Should_Return_IsLogicalScrollEnabled_True()
-        {
-            var target = CreateTarget();
-
-            target.ApplyTemplate();
-
-            Assert.True(((ILogicalScrollable)target).IsLogicalScrollEnabled);
-        }
-
-        [Fact]
-        public void Parent_ScrollContentPresenter_Properties_Should_Be_Set()
-        {
-            var target = CreateTarget();
-
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            var scroll = (ScrollContentPresenter)target.Parent;
-            Assert.Equal(new Size(10, 20), scroll.Extent);
-            Assert.Equal(new Size(100, 10), scroll.Viewport);
-        }
-
-        [Fact]
-        public void Should_Fill_Panel_With_Containers()
-        {
-            var target = CreateTarget();
-
-            target.ApplyTemplate();
-
-            target.Measure(new Size(100, 100));
-            Assert.Equal(10, target.Panel.Children.Count);
-
-            target.Arrange(new Rect(0, 0, 100, 100));
-            Assert.Equal(10, target.Panel.Children.Count);
-        }
-
-        [Fact]
-        public void Should_Only_Create_Enough_Containers_To_Display_All_Items()
-        {
-            var target = CreateTarget(itemCount: 2);
-
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(2, target.Panel.Children.Count);
-        }
-
-        [Fact]
-        public void Should_Expand_To_Fit_Containers_When_Flexible_Size()
-        {
-            var target = CreateTarget();
-
-            target.ApplyTemplate();
-            target.Measure(Size.Infinity);
-            target.Arrange(new Rect(target.DesiredSize));
-
-            Assert.Equal(new Size(10, 200), target.DesiredSize);
-            Assert.Equal(new Size(10, 200), target.Bounds.Size);
-            Assert.Equal(20, target.Panel.Children.Count);
-        }
-
-        [Fact]
-        public void Initial_Item_DataContexts_Should_Be_Correct()
-        {
-            var target = CreateTarget();
-            var items = (IList<string>)target.Items;
-
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            for (var i = 0; i < target.Panel.Children.Count; ++i)
-            {
-                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
-            }
-        }
-
-        [Fact]
-        public void Should_Add_New_Items_When_Control_Is_Enlarged()
-        {
-            var target = CreateTarget();
-            var items = (IList<string>)target.Items;
-
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(10, target.Panel.Children.Count);
-
-            target.Measure(new Size(120, 120));
-            target.Arrange(new Rect(0, 0, 100, 120));
-
-            Assert.Equal(12, target.Panel.Children.Count);
-
-            for (var i = 0; i < target.Panel.Children.Count; ++i)
-            {
-                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
-            }
-        }
-
-        [Fact]
-        public void Should_Not_Create_Virtualizer_Before_Panel()
-        {
-            var target = CreateTarget();
-
-            Assert.Null(target.Panel);
-            Assert.Null(target.Virtualizer);
-        }
-
-        [Fact]
-        public void Changing_VirtualizationMode_None_To_Simple_Should_Update_Control()
-        {
-            var target = CreateTarget(mode: ItemVirtualizationMode.None);
-            var scroll = (ScrollContentPresenter)target.Parent;
-
-            scroll.Measure(new Size(100, 100));
-            scroll.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(20, target.Panel.Children.Count);
-            Assert.Equal(new Size(100, 200), scroll.Extent);
-            Assert.Equal(new Size(100, 100), scroll.Viewport);
-
-            target.VirtualizationMode = ItemVirtualizationMode.Simple;
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(10, target.Panel.Children.Count);
-            Assert.Equal(new Size(10, 20), scroll.Extent);
-            Assert.Equal(new Size(100, 10), scroll.Viewport);
-        }
-
-        [Fact]
-        public void Changing_VirtualizationMode_None_To_Simple_Should_Add_Correct_Number_Of_Controls()
-        {
-            using (UnitTestApplication.Start(new TestServices()))
-            {
-                var target = CreateTarget(mode: ItemVirtualizationMode.None);
-                var scroll = (TestScroller)target.Parent;
-
-                scroll.Width = scroll.Height = 100;
-                scroll.LayoutManager.ExecuteInitialLayoutPass();
-
-                // Ensure than an intermediate measure pass doesn't add more controls than it
-                // should. This can happen if target gets measured with Size.Infinity which
-                // is what the available size should be when VirtualizationMode == None but not
-                // what it should after VirtualizationMode is changed to Simple.
-                target.Panel.Children.CollectionChanged += (s, e) =>
-                {
-                    Assert.InRange(target.Panel.Children.Count, 0, 10);
-                };
-
-                target.VirtualizationMode = ItemVirtualizationMode.Simple;
-                ((ILayoutRoot)scroll.GetVisualRoot()).LayoutManager.ExecuteLayoutPass();
-
-                Assert.Equal(10, target.Panel.Children.Count);
-            }
-        }
-
-        [Fact]
-        public void Changing_VirtualizationMode_Simple_To_None_Should_Update_Control()
-        {
-            var target = CreateTarget();
-            var scroll = (ScrollContentPresenter)target.Parent;
-
-            scroll.Measure(new Size(100, 100));
-            scroll.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(10, target.Panel.Children.Count);
-            Assert.Equal(new Size(10, 20), scroll.Extent);
-            Assert.Equal(new Size(100, 10), scroll.Viewport);
-
-            target.VirtualizationMode = ItemVirtualizationMode.None;
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            // Here - unlike changing the other way - we need to do a layout pass on the scroll
-            // content presenter as non-logical scroll values are only updated on arrange.
-            scroll.Measure(new Size(100, 100));
-            scroll.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(20, target.Panel.Children.Count);
-            Assert.Equal(new Size(100, 200), scroll.Extent);
-            Assert.Equal(new Size(100, 100), scroll.Viewport);
-        }
-
-        private static ItemsPresenter CreateTarget(
-            ItemVirtualizationMode mode = ItemVirtualizationMode.Simple,
-            Orientation orientation = Orientation.Vertical,
-            bool useContainers = true,
-            int itemCount = 20)
-        {
-            ItemsPresenter result;
-            var items = Enumerable.Range(0, itemCount).Select(x => $"Item {x}").ToList();
-
-            var scroller = new TestScroller
-            {
-                CanHorizontallyScroll = false,
-                CanVerticallyScroll = true,
-                Content = result = new TestItemsPresenter(useContainers)
-                {
-                    Items = items,
-                    ItemsPanel = VirtualizingPanelTemplate(orientation),
-                    ItemTemplate = ItemTemplate(),
-                    VirtualizationMode = mode,
-                }
-            };
-
-            scroller.UpdateChild();
-
-            return result;
-        }
-
-        private static IDataTemplate ItemTemplate()
-        {
-            return new FuncDataTemplate<string>((x, _) => new Canvas
-            {
-                Width = 10,
-                Height = 10,
-            });
-        }
-
-        private static ITemplate<Panel> VirtualizingPanelTemplate(
-            Orientation orientation = Orientation.Vertical)
-        {
-            return new FuncTemplate<Panel>(() => new VirtualizingStackPanel
-            {
-                Orientation = orientation,
-            });
-        }
-
-        private class TestScroller : ScrollContentPresenter, IRenderRoot, ILayoutRoot
-        {
-            public TestScroller()
-            {
-                LayoutManager = new LayoutManager(this);
-            }
-
-            public IRenderer Renderer { get; }
-            public Size ClientSize { get; }
-            public double RenderScaling => 1;
-
-            public Size MaxClientSize => Size.Infinity;
-
-            public double LayoutScaling => 1;
-
-            public ILayoutManager LayoutManager { get; }
-
-            public IRenderTarget CreateRenderTarget() => throw new NotImplementedException();
-            public void Invalidate(Rect rect) => throw new NotImplementedException();
-            public Point PointToClient(PixelPoint p) => throw new NotImplementedException();
-            public PixelPoint PointToScreen(Point p) => throw new NotImplementedException();
-        }
-
-        private class TestItemsPresenter : ItemsPresenter
-        {
-            private bool _useContainers;
-
-            public TestItemsPresenter(bool useContainers)
-            {
-                _useContainers = useContainers;
-            }
-
-            protected override IItemContainerGenerator CreateItemContainerGenerator()
-            {
-                return _useContainers ?
-                    new ItemContainerGenerator<TestContainer>(this, TestContainer.ContentProperty, null) :
-                    new ItemContainerGenerator(this);
-            }
-        }
-
-        private class TestContainer : ContentControl
-        {
-            public TestContainer()
-            {
-                Width = 10;
-                Height = 10;
-            }
-        }
-    }
-}
+////using System;
+////using System.Collections.Generic;
+////using System.Linq;
+////using Avalonia.Controls.Generators;
+////using Avalonia.Controls.Presenters;
+////using Avalonia.Controls.Primitives;
+////using Avalonia.Controls.Templates;
+////using Avalonia.Layout;
+////using Avalonia.Platform;
+////using Avalonia.Rendering;
+////using Avalonia.UnitTests;
+////using Avalonia.VisualTree;
+////using Xunit;
+
+////namespace Avalonia.Controls.UnitTests.Presenters
+////{
+////    public class ItemsPresenterTests_Virtualization
+////    {
+////        [Fact]
+////        public void Should_Not_Create_Items_Before_Added_To_Visual_Tree()
+////        {
+////            var items = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+////            var target = new TestItemsPresenter(true)
+////            {
+////                Items = items,
+////                ItemsPanel = VirtualizingPanelTemplate(Orientation.Vertical),
+////                ItemTemplate = ItemTemplate(),
+////                VirtualizationMode = ItemVirtualizationMode.Simple,
+////            };
+
+////            var scroller = new ScrollContentPresenter
+////            {
+////                Content = target,
+////            };
+
+////            scroller.UpdateChild();
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Empty(target.Panel.Children);
+
+////            var root = new TestRoot
+////            {
+////                Child = scroller,
+////            };
+
+////            target.InvalidateMeasure();
+////            target.Panel.InvalidateMeasure();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(10, target.Panel.Children.Count);
+////        }
+
+////        [Fact]
+////        public void Should_Return_IsLogicalScrollEnabled_False_When_Has_No_Virtualizing_Panel()
+////        {
+////            var target = CreateTarget();
+////            target.ClearValue(ItemsPresenter.ItemsPanelProperty);
+
+////            target.ApplyTemplate();
+
+////            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
+////        }
+
+////        [Fact]
+////        public void Should_Return_IsLogicalScrollEnabled_False_When_VirtualizationMode_None()
+////        {
+////            var target = CreateTarget(ItemVirtualizationMode.None);
+
+////            target.ApplyTemplate();
+
+////            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
+////        }
+
+////        [Fact]
+////        public void Should_Return_IsLogicalScrollEnabled_False_When_Doesnt_Have_ScrollPresenter_Parent()
+////        {
+////            var target = new ItemsPresenter
+////            {
+////                ItemsPanel = VirtualizingPanelTemplate(),
+////                ItemTemplate = ItemTemplate(),
+////                VirtualizationMode = ItemVirtualizationMode.Simple,
+////            };
+
+////            target.ApplyTemplate();
+
+////            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
+////        }
+
+////        [Fact]
+////        public void Should_Return_IsLogicalScrollEnabled_True()
+////        {
+////            var target = CreateTarget();
+
+////            target.ApplyTemplate();
+
+////            Assert.True(((ILogicalScrollable)target).IsLogicalScrollEnabled);
+////        }
+
+////        [Fact]
+////        public void Parent_ScrollContentPresenter_Properties_Should_Be_Set()
+////        {
+////            var target = CreateTarget();
+
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            var scroll = (ScrollContentPresenter)target.Parent;
+////            Assert.Equal(new Size(10, 20), scroll.Extent);
+////            Assert.Equal(new Size(100, 10), scroll.Viewport);
+////        }
+
+////        [Fact]
+////        public void Should_Fill_Panel_With_Containers()
+////        {
+////            var target = CreateTarget();
+
+////            target.ApplyTemplate();
+
+////            target.Measure(new Size(100, 100));
+////            Assert.Equal(10, target.Panel.Children.Count);
+
+////            target.Arrange(new Rect(0, 0, 100, 100));
+////            Assert.Equal(10, target.Panel.Children.Count);
+////        }
+
+////        [Fact]
+////        public void Should_Only_Create_Enough_Containers_To_Display_All_Items()
+////        {
+////            var target = CreateTarget(itemCount: 2);
+
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(2, target.Panel.Children.Count);
+////        }
+
+////        [Fact]
+////        public void Should_Expand_To_Fit_Containers_When_Flexible_Size()
+////        {
+////            var target = CreateTarget();
+
+////            target.ApplyTemplate();
+////            target.Measure(Size.Infinity);
+////            target.Arrange(new Rect(target.DesiredSize));
+
+////            Assert.Equal(new Size(10, 200), target.DesiredSize);
+////            Assert.Equal(new Size(10, 200), target.Bounds.Size);
+////            Assert.Equal(20, target.Panel.Children.Count);
+////        }
+
+////        [Fact]
+////        public void Initial_Item_DataContexts_Should_Be_Correct()
+////        {
+////            var target = CreateTarget();
+////            var items = (IList<string>)target.Items;
+
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            for (var i = 0; i < target.Panel.Children.Count; ++i)
+////            {
+////                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
+////            }
+////        }
+
+////        [Fact]
+////        public void Should_Add_New_Items_When_Control_Is_Enlarged()
+////        {
+////            var target = CreateTarget();
+////            var items = (IList<string>)target.Items;
+
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(10, target.Panel.Children.Count);
+
+////            target.Measure(new Size(120, 120));
+////            target.Arrange(new Rect(0, 0, 100, 120));
+
+////            Assert.Equal(12, target.Panel.Children.Count);
+
+////            for (var i = 0; i < target.Panel.Children.Count; ++i)
+////            {
+////                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
+////            }
+////        }
+
+////        [Fact]
+////        public void Should_Not_Create_Virtualizer_Before_Panel()
+////        {
+////            var target = CreateTarget();
+
+////            Assert.Null(target.Panel);
+////            Assert.Null(target.Virtualizer);
+////        }
+
+////        [Fact]
+////        public void Changing_VirtualizationMode_None_To_Simple_Should_Update_Control()
+////        {
+////            var target = CreateTarget(mode: ItemVirtualizationMode.None);
+////            var scroll = (ScrollContentPresenter)target.Parent;
+
+////            scroll.Measure(new Size(100, 100));
+////            scroll.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(20, target.Panel.Children.Count);
+////            Assert.Equal(new Size(100, 200), scroll.Extent);
+////            Assert.Equal(new Size(100, 100), scroll.Viewport);
+
+////            target.VirtualizationMode = ItemVirtualizationMode.Simple;
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(10, target.Panel.Children.Count);
+////            Assert.Equal(new Size(10, 20), scroll.Extent);
+////            Assert.Equal(new Size(100, 10), scroll.Viewport);
+////        }
+
+////        [Fact]
+////        public void Changing_VirtualizationMode_None_To_Simple_Should_Add_Correct_Number_Of_Controls()
+////        {
+////            using (UnitTestApplication.Start(new TestServices()))
+////            {
+////                var target = CreateTarget(mode: ItemVirtualizationMode.None);
+////                var scroll = (TestScroller)target.Parent;
+
+////                scroll.Width = scroll.Height = 100;
+////                scroll.LayoutManager.ExecuteInitialLayoutPass();
+
+////                // Ensure than an intermediate measure pass doesn't add more controls than it
+////                // should. This can happen if target gets measured with Size.Infinity which
+////                // is what the available size should be when VirtualizationMode == None but not
+////                // what it should after VirtualizationMode is changed to Simple.
+////                target.Panel.Children.CollectionChanged += (s, e) =>
+////                {
+////                    Assert.InRange(target.Panel.Children.Count, 0, 10);
+////                };
+
+////                target.VirtualizationMode = ItemVirtualizationMode.Simple;
+////                ((ILayoutRoot)scroll.GetVisualRoot()).LayoutManager.ExecuteLayoutPass();
+
+////                Assert.Equal(10, target.Panel.Children.Count);
+////            }
+////        }
+
+////        [Fact]
+////        public void Changing_VirtualizationMode_Simple_To_None_Should_Update_Control()
+////        {
+////            var target = CreateTarget();
+////            var scroll = (ScrollContentPresenter)target.Parent;
+
+////            scroll.Measure(new Size(100, 100));
+////            scroll.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(10, target.Panel.Children.Count);
+////            Assert.Equal(new Size(10, 20), scroll.Extent);
+////            Assert.Equal(new Size(100, 10), scroll.Viewport);
+
+////            target.VirtualizationMode = ItemVirtualizationMode.None;
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            // Here - unlike changing the other way - we need to do a layout pass on the scroll
+////            // content presenter as non-logical scroll values are only updated on arrange.
+////            scroll.Measure(new Size(100, 100));
+////            scroll.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(20, target.Panel.Children.Count);
+////            Assert.Equal(new Size(100, 200), scroll.Extent);
+////            Assert.Equal(new Size(100, 100), scroll.Viewport);
+////        }
+
+////        private static ItemsPresenter CreateTarget(
+////            ItemVirtualizationMode mode = ItemVirtualizationMode.Simple,
+////            Orientation orientation = Orientation.Vertical,
+////            bool useContainers = true,
+////            int itemCount = 20)
+////        {
+////            ItemsPresenter result;
+////            var items = Enumerable.Range(0, itemCount).Select(x => $"Item {x}").ToList();
+
+////            var scroller = new TestScroller
+////            {
+////                CanHorizontallyScroll = false,
+////                CanVerticallyScroll = true,
+////                Content = result = new TestItemsPresenter(useContainers)
+////                {
+////                    Items = items,
+////                    ItemsPanel = VirtualizingPanelTemplate(orientation),
+////                    ItemTemplate = ItemTemplate(),
+////                    VirtualizationMode = mode,
+////                }
+////            };
+
+////            scroller.UpdateChild();
+
+////            return result;
+////        }
+
+////        private static IDataTemplate ItemTemplate()
+////        {
+////            return new FuncDataTemplate<string>((x, _) => new Canvas
+////            {
+////                Width = 10,
+////                Height = 10,
+////            });
+////        }
+
+////        private static ITemplate<Panel> VirtualizingPanelTemplate(
+////            Orientation orientation = Orientation.Vertical)
+////        {
+////            return new FuncTemplate<Panel>(() => new VirtualizingStackPanel
+////            {
+////                Orientation = orientation,
+////            });
+////        }
+
+////        private class TestScroller : ScrollContentPresenter, IRenderRoot, ILayoutRoot
+////        {
+////            public TestScroller()
+////            {
+////                LayoutManager = new LayoutManager(this);
+////            }
+
+////            public IRenderer Renderer { get; }
+////            public Size ClientSize { get; }
+////            public double RenderScaling => 1;
+
+////            public Size MaxClientSize => Size.Infinity;
+
+////            public double LayoutScaling => 1;
+
+////            public ILayoutManager LayoutManager { get; }
+
+////            public IRenderTarget CreateRenderTarget() => throw new NotImplementedException();
+////            public void Invalidate(Rect rect) => throw new NotImplementedException();
+////            public Point PointToClient(PixelPoint p) => throw new NotImplementedException();
+////            public PixelPoint PointToScreen(Point p) => throw new NotImplementedException();
+////        }
+
+////        private class TestItemsPresenter : ItemsPresenter
+////        {
+////            private bool _useContainers;
+
+////            public TestItemsPresenter(bool useContainers)
+////            {
+////                _useContainers = useContainers;
+////            }
+
+////            protected override IItemContainerGenerator CreateItemContainerGenerator()
+////            {
+////                return _useContainers ?
+////                    new ItemContainerGenerator<TestContainer>(this, TestContainer.ContentProperty, null) :
+////                    new ItemContainerGenerator(this);
+////            }
+////        }
+
+////        private class TestContainer : ContentControl
+////        {
+////            public TestContainer()
+////            {
+////                Width = 10;
+////                Height = 10;
+////            }
+////        }
+////    }
+////}
diff --git a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs
index 08fd777ac65..131b86e4b16 100644
--- a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs
+++ b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs
@@ -1,1110 +1,1110 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Collections.ObjectModel;
-using System.Linq;
-using Avalonia.Collections;
-using Avalonia.Controls.Generators;
-using Avalonia.Controls.Presenters;
-using Avalonia.Controls.Primitives;
-using Avalonia.Controls.Templates;
-using Avalonia.Input;
-using Avalonia.Layout;
-using Avalonia.LogicalTree;
-using Avalonia.Platform;
-using Avalonia.Rendering;
-using Avalonia.Styling;
-using Avalonia.UnitTests;
-using Xunit;
-
-namespace Avalonia.Controls.UnitTests.Presenters
-{
-    public class ItemsPresenterTests_Virtualization_Simple
-    {
-        [Fact]
-        public void Should_Return_Items_Count_For_Extent_Vertical()
-        {
-            var target = CreateTarget();
-
-            target.ApplyTemplate();
-
-            Assert.Equal(new Size(0, 20), ((ILogicalScrollable)target).Extent);
-        }
-
-        [Fact]
-        public void Should_Return_Items_Count_For_Extent_Horizontal()
-        {
-            var target = CreateTarget(orientation: Orientation.Horizontal);
-
-            target.ApplyTemplate();
-
-            Assert.Equal(new Size(20, 0), ((ILogicalScrollable)target).Extent);
-        }
-
-        [Fact]
-        public void Should_Have_Number_Of_Visible_Items_As_Viewport_Vertical()
-        {
-            var target = CreateTarget();
-
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(new Size(100, 10), ((ILogicalScrollable)target).Viewport);
-        }
-
-        [Fact]
-        public void Should_Have_Number_Of_Visible_Items_As_Viewport_Horizontal()
-        {
-            var target = CreateTarget(orientation: Orientation.Horizontal);
-
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(new Size(10, 100), ((ILogicalScrollable)target).Viewport);
-        }
-
-        [Fact]
-        public void Should_Add_Containers_When_Panel_Is_Not_Full()
-        {
-            var target = CreateTarget(itemCount: 5);
-            var items = (IList<string>)target.Items;
-
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(5, target.Panel.Children.Count);
-
-            items.Add("New Item");
-
-            Assert.Equal(6, target.Panel.Children.Count);
-        }
-
-        [Fact]
-        public void Should_Remove_Items_When_Control_Is_Shrank()
-        {
-            var target = CreateTarget();
-            var items = (IList<string>)target.Items;
-
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(10, target.Panel.Children.Count);
-
-            target.Measure(new Size(100, 80));
-            target.Arrange(new Rect(0, 0, 100, 80));
-
-            Assert.Equal(8, target.Panel.Children.Count);
-        }
-
-        [Fact]
-        public void Should_Add_New_Containers_At_Top_When_Control_Is_Scrolled_To_Bottom_And_Enlarged()
-        {
-            var target = CreateTarget();
-            var items = (IList<string>)target.Items;
+////using System;
+////using System.Collections;
+////using System.Collections.Generic;
+////using System.Collections.ObjectModel;
+////using System.Linq;
+////using Avalonia.Collections;
+////using Avalonia.Controls.Generators;
+////using Avalonia.Controls.Presenters;
+////using Avalonia.Controls.Primitives;
+////using Avalonia.Controls.Templates;
+////using Avalonia.Input;
+////using Avalonia.Layout;
+////using Avalonia.LogicalTree;
+////using Avalonia.Platform;
+////using Avalonia.Rendering;
+////using Avalonia.Styling;
+////using Avalonia.UnitTests;
+////using Xunit;
+
+////namespace Avalonia.Controls.UnitTests.Presenters
+////{
+////    public class ItemsPresenterTests_Virtualization_Simple
+////    {
+////        [Fact]
+////        public void Should_Return_Items_Count_For_Extent_Vertical()
+////        {
+////            var target = CreateTarget();
+
+////            target.ApplyTemplate();
+
+////            Assert.Equal(new Size(0, 20), ((ILogicalScrollable)target).Extent);
+////        }
+
+////        [Fact]
+////        public void Should_Return_Items_Count_For_Extent_Horizontal()
+////        {
+////            var target = CreateTarget(orientation: Orientation.Horizontal);
+
+////            target.ApplyTemplate();
+
+////            Assert.Equal(new Size(20, 0), ((ILogicalScrollable)target).Extent);
+////        }
+
+////        [Fact]
+////        public void Should_Have_Number_Of_Visible_Items_As_Viewport_Vertical()
+////        {
+////            var target = CreateTarget();
+
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(new Size(100, 10), ((ILogicalScrollable)target).Viewport);
+////        }
+
+////        [Fact]
+////        public void Should_Have_Number_Of_Visible_Items_As_Viewport_Horizontal()
+////        {
+////            var target = CreateTarget(orientation: Orientation.Horizontal);
+
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(new Size(10, 100), ((ILogicalScrollable)target).Viewport);
+////        }
+
+////        [Fact]
+////        public void Should_Add_Containers_When_Panel_Is_Not_Full()
+////        {
+////            var target = CreateTarget(itemCount: 5);
+////            var items = (IList<string>)target.Items;
+
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(5, target.Panel.Children.Count);
+
+////            items.Add("New Item");
+
+////            Assert.Equal(6, target.Panel.Children.Count);
+////        }
+
+////        [Fact]
+////        public void Should_Remove_Items_When_Control_Is_Shrank()
+////        {
+////            var target = CreateTarget();
+////            var items = (IList<string>)target.Items;
+
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(10, target.Panel.Children.Count);
+
+////            target.Measure(new Size(100, 80));
+////            target.Arrange(new Rect(0, 0, 100, 80));
+
+////            Assert.Equal(8, target.Panel.Children.Count);
+////        }
+
+////        [Fact]
+////        public void Should_Add_New_Containers_At_Top_When_Control_Is_Scrolled_To_Bottom_And_Enlarged()
+////        {
+////            var target = CreateTarget();
+////            var items = (IList<string>)target.Items;
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            Assert.Equal(10, target.Panel.Children.Count);
+////            Assert.Equal(10, target.Panel.Children.Count);
 
-            ((IScrollable)target).Offset = new Vector(0, 10);
-            target.Measure(new Size(120, 120));
-            target.Arrange(new Rect(0, 0, 100, 120));
+////            ((IScrollable)target).Offset = new Vector(0, 10);
+////            target.Measure(new Size(120, 120));
+////            target.Arrange(new Rect(0, 0, 100, 120));
 
-            Assert.Equal(12, target.Panel.Children.Count);
+////            Assert.Equal(12, target.Panel.Children.Count);
 
-            for (var i = 0; i < target.Panel.Children.Count; ++i)
-            {
-                Assert.Equal(items[i + 8], target.Panel.Children[i].DataContext);
-            }
-        }
+////            for (var i = 0; i < target.Panel.Children.Count; ++i)
+////            {
+////                Assert.Equal(items[i + 8], target.Panel.Children[i].DataContext);
+////            }
+////        }
 
-        [Fact]
-        public void Should_Update_Containers_When_Items_Changes()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Should_Update_Containers_When_Items_Changes()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            target.Items = new[] { "foo", "bar", "baz" };
+////            target.Items = new[] { "foo", "bar", "baz" };
 
-            Assert.Equal(3, target.Panel.Children.Count);
-        }
+////            Assert.Equal(3, target.Panel.Children.Count);
+////        }
 
-        [Fact]
-        public void Should_Decrease_The_Viewport_Size_By_One_If_There_Is_A_Partial_Item()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Should_Decrease_The_Viewport_Size_By_One_If_There_Is_A_Partial_Item()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 95));
-            target.Arrange(new Rect(0, 0, 100, 95));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 95));
+////            target.Arrange(new Rect(0, 0, 100, 95));
 
-            Assert.Equal(new Size(100, 9), ((ILogicalScrollable)target).Viewport);
-        }
+////            Assert.Equal(new Size(100, 9), ((ILogicalScrollable)target).Viewport);
+////        }
 
-        [Fact]
-        public void Moving_To_And_From_The_End_With_Partial_Item_Should_Set_Panel_PixelOffset()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Moving_To_And_From_The_End_With_Partial_Item_Should_Set_Panel_PixelOffset()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 95));
-            target.Arrange(new Rect(0, 0, 100, 95));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 95));
+////            target.Arrange(new Rect(0, 0, 100, 95));
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 11);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 11);
 
-            var minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
-            Assert.Equal(new Vector(0, 11), ((ILogicalScrollable)target).Offset);
-            Assert.Equal(10, minIndex);
-            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
+////            var minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
+////            Assert.Equal(new Vector(0, 11), ((ILogicalScrollable)target).Offset);
+////            Assert.Equal(10, minIndex);
+////            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
 
-            minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
-            Assert.Equal(new Vector(0, 10), ((ILogicalScrollable)target).Offset);
-            Assert.Equal(10, minIndex);
-            Assert.Equal(0, ((IVirtualizingPanel)target.Panel).PixelOffset);
+////            minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
+////            Assert.Equal(new Vector(0, 10), ((ILogicalScrollable)target).Offset);
+////            Assert.Equal(10, minIndex);
+////            Assert.Equal(0, ((IVirtualizingPanel)target.Panel).PixelOffset);
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 11);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 11);
 
-            minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
-            Assert.Equal(new Vector(0, 11), ((ILogicalScrollable)target).Offset);
-            Assert.Equal(10, minIndex);
-            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
-        }
+////            minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
+////            Assert.Equal(new Vector(0, 11), ((ILogicalScrollable)target).Offset);
+////            Assert.Equal(10, minIndex);
+////            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
+////        }
 
-        [Fact]
-        public void Inserting_Items_Should_Update_Containers()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Inserting_Items_Should_Update_Containers()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
 
-            var expected = Enumerable.Range(5, 10).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(5, 10).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            items.Insert(6, "Inserted");
-            expected.Insert(1, "Inserted");
-            expected.RemoveAt(expected.Count - 1);
+////            items.Insert(6, "Inserted");
+////            expected.Insert(1, "Inserted");
+////            expected.RemoveAt(expected.Count - 1);
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Inserting_Items_Before_Visibile_Containers_Should_Update_Containers()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Inserting_Items_Before_Visibile_Containers_Should_Update_Containers()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
 
-            var expected = Enumerable.Range(5, 10).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(5, 10).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            items.Insert(0, "Inserted");
+////            items.Insert(0, "Inserted");
 
-            expected = Enumerable.Range(4, 10).Select(x => $"Item {x}").ToList();
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            expected = Enumerable.Range(4, 10).Select(x => $"Item {x}").ToList();
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Removing_First_Materialized_Item_Should_Update_Containers()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Removing_First_Materialized_Item_Should_Update_Containers()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            items.RemoveAt(0);
-            expected = Enumerable.Range(1, 10).Select(x => $"Item {x}").ToList();
+////            items.RemoveAt(0);
+////            expected = Enumerable.Range(1, 10).Select(x => $"Item {x}").ToList();
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Removing_Items_From_Middle_Should_Update_Containers_When_All_Items_Visible()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Removing_Items_From_Middle_Should_Update_Containers_When_All_Items_Visible()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 200));
-            target.Arrange(new Rect(0, 0, 100, 200));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 200));
+////            target.Arrange(new Rect(0, 0, 100, 200));
 
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(items, actual);
+////            Assert.Equal(items, actual);
 
-            items.RemoveAt(2);
+////            items.RemoveAt(2);
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(items, actual);
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(items, actual);
 
-            items.RemoveAt(items.Count - 2);
+////            items.RemoveAt(items.Count - 2);
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(items, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(items, actual);
+////        }
 
-        [Fact]
-        public void Removing_Last_Item_Should_Update_Containers_When_All_Items_Visible()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Removing_Last_Item_Should_Update_Containers_When_All_Items_Visible()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 200));
-            target.Arrange(new Rect(0, 0, 100, 200));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 200));
+////            target.Arrange(new Rect(0, 0, 100, 200));
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
 
-            var expected = Enumerable.Range(0, 20).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 20).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            items.Remove(items.Last());
-            expected.Remove(expected.Last());
+////            items.Remove(items.Last());
+////            expected.Remove(expected.Last());
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Removing_Items_When_Scrolled_To_End_Should_Recyle_Containers_At_Top()
-        {
-            var target = CreateTarget(useAvaloniaList: true);
+////        [Fact]
+////        public void Removing_Items_When_Scrolled_To_End_Should_Recyle_Containers_At_Top()
+////        {
+////            var target = CreateTarget(useAvaloniaList: true);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
 
-            var expected = Enumerable.Range(10, 10).Select(x => $"Item {x}").ToList();
-            var items = (AvaloniaList<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(10, 10).Select(x => $"Item {x}").ToList();
+////            var items = (AvaloniaList<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            items.RemoveRange(18, 2);
-            expected = Enumerable.Range(8, 10).Select(x => $"Item {x}").ToList();
+////            items.RemoveRange(18, 2);
+////            expected = Enumerable.Range(8, 10).Select(x => $"Item {x}").ToList();
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Removing_Items_When_Scrolled_To_Near_End_Should_Recycle_Containers_At_Bottom_And_Top()
-        {
-            var target = CreateTarget(useAvaloniaList: true);
+////        [Fact]
+////        public void Removing_Items_When_Scrolled_To_Near_End_Should_Recycle_Containers_At_Bottom_And_Top()
+////        {
+////            var target = CreateTarget(useAvaloniaList: true);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 9);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 9);
 
-            var expected = Enumerable.Range(9, 10).Select(x => $"Item {x}").ToList();
-            var items = (AvaloniaList<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(9, 10).Select(x => $"Item {x}").ToList();
+////            var items = (AvaloniaList<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            items.RemoveRange(15, 3);
-            expected = Enumerable.Range(7, 8).Select(x => $"Item {x}")
-                .Concat(Enumerable.Range(18, 2).Select(x => $"Item {x}"))
-                .ToList();
+////            items.RemoveRange(15, 3);
+////            expected = Enumerable.Range(7, 8).Select(x => $"Item {x}")
+////                .Concat(Enumerable.Range(18, 2).Select(x => $"Item {x}"))
+////                .ToList();
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Measuring_To_Infinity_When_Scrolled_To_End_Should_Not_Throw()
-        {
-            var target = CreateTarget(useAvaloniaList: true);
+////        [Fact]
+////        public void Measuring_To_Infinity_When_Scrolled_To_End_Should_Not_Throw()
+////        {
+////            var target = CreateTarget(useAvaloniaList: true);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
 
-            // Check for issue #589: this should not throw.
-            target.Measure(Size.Infinity);
+////            // Check for issue #589: this should not throw.
+////            target.Measure(Size.Infinity);
 
-            var expected = Enumerable.Range(0, 20).Select(x => $"Item {x}").ToList();
-            var items = (AvaloniaList<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 20).Select(x => $"Item {x}").ToList();
+////            var items = (AvaloniaList<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
-        }
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Replacing_Items_Should_Update_Containers()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Replacing_Items_Should_Update_Containers()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            items[4] = expected[4] = "Replaced";
+////            items[4] = expected[4] = "Replaced";
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Moving_Items_Should_Update_Containers()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Moving_Items_Should_Update_Containers()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            items.Move(4, 8);
-            var i = expected[4];
-            expected.RemoveAt(4);
-            expected.Insert(8, i);
+////            items.Move(4, 8);
+////            var i = expected[4];
+////            expected.RemoveAt(4);
+////            expected.Insert(8, i);
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Setting_Items_To_Null_Should_Remove_Containers()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Setting_Items_To_Null_Should_Remove_Containers()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            target.Items = null;
+////            target.Items = null;
 
-            Assert.Empty(target.Panel.Children);
-        }
+////            Assert.Empty(target.Panel.Children);
+////        }
 
-        [Fact]
-        public void Reassigning_Items_Should_Create_Containers()
-        {
-            var target = CreateTarget(itemCount: 5);
+////        [Fact]
+////        public void Reassigning_Items_Should_Create_Containers()
+////        {
+////            var target = CreateTarget(itemCount: 5);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
-            target.Items = expected;
+////            expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
+////            target.Items = expected;
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Inserting_Then_Removing_Should_Add_Remove_Containers()
-        {
-            var items = new AvaloniaList<string>(Enumerable.Range(0, 5).Select(x => $"Item {x}"));
-            var toAdd = Enumerable.Range(0, 3).Select(x => $"Added Item {x}").ToArray();
-            var target = new ItemsPresenter
-            {
-                VirtualizationMode = ItemVirtualizationMode.None,
-                Items = items,
-                ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 10 }),
-            };
+////        [Fact]
+////        public void Inserting_Then_Removing_Should_Add_Remove_Containers()
+////        {
+////            var items = new AvaloniaList<string>(Enumerable.Range(0, 5).Select(x => $"Item {x}"));
+////            var toAdd = Enumerable.Range(0, 3).Select(x => $"Added Item {x}").ToArray();
+////            var target = new ItemsPresenter
+////            {
+////                VirtualizationMode = ItemVirtualizationMode.None,
+////                Items = items,
+////                ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 10 }),
+////            };
 
-            target.ApplyTemplate();
+////            target.ApplyTemplate();
 
-            Assert.Equal(items.Count, target.Panel.Children.Count);
+////            Assert.Equal(items.Count, target.Panel.Children.Count);
 
-            int addIndex = 1;
-            foreach (var item in toAdd)
-            {
-                items.Insert(addIndex++, item);
-            }
+////            int addIndex = 1;
+////            foreach (var item in toAdd)
+////            {
+////                items.Insert(addIndex++, item);
+////            }
 
-            Assert.Equal(items.Count, target.Panel.Children.Count);
+////            Assert.Equal(items.Count, target.Panel.Children.Count);
 
-            foreach (var item in toAdd)
-            {
-                items.Remove(item);
-            }
-
-            Assert.Equal(items.Count, target.Panel.Children.Count);
-        }
-
-        [Fact]
-        public void Reassigning_Items_Should_Remove_Containers()
-        {
-            var target = CreateTarget(itemCount: 6);
+////            foreach (var item in toAdd)
+////            {
+////                items.Remove(item);
+////            }
+
+////            Assert.Equal(items.Count, target.Panel.Children.Count);
+////        }
+
+////        [Fact]
+////        public void Reassigning_Items_Should_Remove_Containers()
+////        {
+////            var target = CreateTarget(itemCount: 6);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
-            target.Items = expected;
+////            expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
+////            target.Items = expected;
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Clearing_Items_And_ReAdding_Should_Remove_Containers()
-        {
-            var target = CreateTarget(itemCount: 6);
+////        [Fact]
+////        public void Clearing_Items_And_ReAdding_Should_Remove_Containers()
+////        {
+////            var target = CreateTarget(itemCount: 6);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
-            target.Items = null;
-            target.Items = expected;
+////            expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
+////            target.Items = null;
+////            target.Items = expected;
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Scrolling_To_Partial_Last_Item_Then_Adding_Item_Updates_Containers()
-        {
-            var target = CreateTarget(itemCount: 10);
-            var items = (IList<string>)target.Items;
+////        [Fact]
+////        public void Scrolling_To_Partial_Last_Item_Then_Adding_Item_Updates_Containers()
+////        {
+////            var target = CreateTarget(itemCount: 10);
+////            var items = (IList<string>)target.Items;
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 95));
-            target.Arrange(new Rect(0, 0, 100, 95));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 95));
+////            target.Arrange(new Rect(0, 0, 100, 95));
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 1);
-            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 1);
+////            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
 
-            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
+////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
 
-            items.Add("Item 10");
+////            items.Add("Item 10");
 
-            expected = Enumerable.Range(1, 10).Select(x => $"Item {x}").ToList();
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-            Assert.Equal(0, ((IVirtualizingPanel)target.Panel).PixelOffset);
-        }
+////            expected = Enumerable.Range(1, 10).Select(x => $"Item {x}").ToList();
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////            Assert.Equal(0, ((IVirtualizingPanel)target.Panel).PixelOffset);
+////        }
 
-        [Fact]
-        public void Scrolling_To_Item_In_Zero_Sized_Presenter_Doesnt_Throw()
-        {
-            using (UnitTestApplication.Start(new TestServices()))
-            {
-                var target = CreateTarget(itemCount: 10);
-                var items = (IList<string>)target.Items;
-                target.ApplyTemplate();
-                target.Measure(Size.Empty);
-                target.Arrange(Rect.Empty);
+////        [Fact]
+////        public void Scrolling_To_Item_In_Zero_Sized_Presenter_Doesnt_Throw()
+////        {
+////            using (UnitTestApplication.Start(new TestServices()))
+////            {
+////                var target = CreateTarget(itemCount: 10);
+////                var items = (IList<string>)target.Items;
+////                target.ApplyTemplate();
+////                target.Measure(Size.Empty);
+////                target.Arrange(Rect.Empty);
 
-                // Check for issue #591: this should not throw.
-                target.ScrollIntoView(0);
-            }
-        }
+////                // Check for issue #591: this should not throw.
+////                target.ScrollIntoView(0);
+////            }
+////        }
 
-        [Fact]
-        public void InsertRange_Items_Should_Update_Containers()
-        {
-            var target = CreateTarget(useAvaloniaList: true);
+////        [Fact]
+////        public void InsertRange_Items_Should_Update_Containers()
+////        {
+////            var target = CreateTarget(useAvaloniaList: true);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-            var items = (AvaloniaList<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+////            var items = (AvaloniaList<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            var toAdd = Enumerable.Range(0, 3).Select(x => $"New Item {x}").ToList();
+////            var toAdd = Enumerable.Range(0, 3).Select(x => $"New Item {x}").ToList();
 
-            int index = 1;
+////            int index = 1;
 
-            items.InsertRange(index, toAdd);
-            expected.InsertRange(index, toAdd);
-            expected.RemoveRange(10, toAdd.Count);
+////            items.InsertRange(index, toAdd);
+////            expected.InsertRange(index, toAdd);
+////            expected.RemoveRange(10, toAdd.Count);
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void InsertRange_Items_Before_Last_Should_Update_Containers()
-        {
-            var target = CreateTarget(useAvaloniaList: true);
+////        [Fact]
+////        public void InsertRange_Items_Before_Last_Should_Update_Containers()
+////        {
+////            var target = CreateTarget(useAvaloniaList: true);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-            var items = (AvaloniaList<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+////            var items = (AvaloniaList<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            var toAdd = Enumerable.Range(0, 3).Select(x => $"New Item {x}").ToList();
+////            var toAdd = Enumerable.Range(0, 3).Select(x => $"New Item {x}").ToList();
 
-            int index = 8;
+////            int index = 8;
 
-            items.InsertRange(index, toAdd);
-            expected.InsertRange(index, toAdd);
-            expected.RemoveRange(10, toAdd.Count);
+////            items.InsertRange(index, toAdd);
+////            expected.InsertRange(index, toAdd);
+////            expected.RemoveRange(10, toAdd.Count);
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void RemoveRange_Items_Should_Update_Containers()
-        {
-            var target = CreateTarget(useAvaloniaList: true);
+////        [Fact]
+////        public void RemoveRange_Items_Should_Update_Containers()
+////        {
+////            var target = CreateTarget(useAvaloniaList: true);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 13).Select(x => $"Item {x}").ToList();
-            var items = (AvaloniaList<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 13).Select(x => $"Item {x}").ToList();
+////            var items = (AvaloniaList<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected.Take(10), actual);
+////            Assert.Equal(expected.Take(10), actual);
 
-            int index = 5;
-            int count = 3;
+////            int index = 5;
+////            int count = 3;
 
-            items.RemoveRange(index, count);
-            expected.RemoveRange(index, count);
+////            items.RemoveRange(index, count);
+////            expected.RemoveRange(index, count);
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void RemoveRange_Items_Before_Last_Should_Update_Containers()
-        {
-            var target = CreateTarget(useAvaloniaList: true);
+////        [Fact]
+////        public void RemoveRange_Items_Before_Last_Should_Update_Containers()
+////        {
+////            var target = CreateTarget(useAvaloniaList: true);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 13).Select(x => $"Item {x}").ToList();
-            var items = (AvaloniaList<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 13).Select(x => $"Item {x}").ToList();
+////            var items = (AvaloniaList<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected.Take(10), actual);
+////            Assert.Equal(expected.Take(10), actual);
 
-            int index = 8;
-            int count = 3;
+////            int index = 8;
+////            int count = 3;
 
-            items.RemoveRange(index, count);
-            expected.RemoveRange(index, count);
+////            items.RemoveRange(index, count);
+////            expected.RemoveRange(index, count);
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Should_Add_Containers_For_Items_After_Clear()
-        {
-            var target = CreateTarget(itemCount: 10);
-            var defaultItems = (IList<string>)target.Items;
-            var items = new AvaloniaList<string>(defaultItems);
-            target.Items = items;
+////        [Fact]
+////        public void Should_Add_Containers_For_Items_After_Clear()
+////        {
+////            var target = CreateTarget(itemCount: 10);
+////            var defaultItems = (IList<string>)target.Items;
+////            var items = new AvaloniaList<string>(defaultItems);
+////            target.Items = items;
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(target.DesiredSize));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(target.DesiredSize));
 
-            Assert.Equal(10, target.Panel.Children.Count);
+////            Assert.Equal(10, target.Panel.Children.Count);
 
-            items.Clear();
+////            items.Clear();
 
-            target.Panel.Measure(new Size(100, 100));
-            target.Panel.Arrange(new Rect(target.Panel.DesiredSize));
+////            target.Panel.Measure(new Size(100, 100));
+////            target.Panel.Arrange(new Rect(target.Panel.DesiredSize));
 
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(target.DesiredSize));
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(target.DesiredSize));
 
-            Assert.Empty(target.Panel.Children);
+////            Assert.Empty(target.Panel.Children);
 
-            items.AddRange(defaultItems.Select(s => s + " new"));
+////            items.AddRange(defaultItems.Select(s => s + " new"));
 
-            target.Panel.Measure(new Size(100, 100));
-            target.Panel.Arrange(new Rect(target.Panel.DesiredSize));
+////            target.Panel.Measure(new Size(100, 100));
+////            target.Panel.Arrange(new Rect(target.Panel.DesiredSize));
 
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(target.DesiredSize));
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(target.DesiredSize));
 
-            Assert.Equal(10, target.Panel.Children.Count);
-        }
+////            Assert.Equal(10, target.Panel.Children.Count);
+////        }
 
-        [Fact]
-        public void Scroll_To_Last_Should_Work()
-        {
-            var target = CreateTarget(itemCount: 11);
-            var scroller = (TestScroller)target.Parent;
+////        [Fact]
+////        public void Scroll_To_Last_Should_Work()
+////        {
+////            var target = CreateTarget(itemCount: 11);
+////            var scroller = (TestScroller)target.Parent;
 
-            scroller.Width = scroller.Height = 100;
-            scroller.LayoutManager.ExecuteInitialLayoutPass();
+////            scroller.Width = scroller.Height = 100;
+////            scroller.LayoutManager.ExecuteInitialLayoutPass();
 
-            var last = (target.Items as IList)[10];
+////            var last = (target.Items as IList)[10];
 
-            target.ScrollIntoView(10);
+////            target.ScrollIntoView(10);
 
-            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-            Assert.Same(target.Panel.Children[9].DataContext, last);
-        }
+////            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
+////            Assert.Same(target.Panel.Children[9].DataContext, last);
+////        }
 
-        [Fact]
-        public void Second_Scroll_To_Last_Should_Work()
-        {
-            var target = CreateTarget(itemCount: 11);
-            var scroller = (TestScroller)target.Parent;
+////        [Fact]
+////        public void Second_Scroll_To_Last_Should_Work()
+////        {
+////            var target = CreateTarget(itemCount: 11);
+////            var scroller = (TestScroller)target.Parent;
 
-            scroller.Width = scroller.Height = 100;
-            scroller.LayoutManager.ExecuteInitialLayoutPass();
+////            scroller.Width = scroller.Height = 100;
+////            scroller.LayoutManager.ExecuteInitialLayoutPass();
 
-            var last = (target.Items as IList)[10];
+////            var last = (target.Items as IList)[10];
 
-            target.ScrollIntoView(10);
+////            target.ScrollIntoView(10);
 
-            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-            Assert.Same(target.Panel.Children[9].DataContext, last);
+////            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
+////            Assert.Same(target.Panel.Children[9].DataContext, last);
 
-            target.ScrollIntoView(10);
+////            target.ScrollIntoView(10);
 
-            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-            Assert.Same(target.Panel.Children[9].DataContext, last);
-        }
+////            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
+////            Assert.Same(target.Panel.Children[9].DataContext, last);
+////        }
 
-        [Fact]
-        public void Scrolling_Less_Than_A_Page_Should_Move_Recycled_Items()
-        {
-            var target = CreateTarget();
-            var items = (IList<string>)target.Items;
+////        [Fact]
+////        public void Scrolling_Less_Than_A_Page_Should_Move_Recycled_Items()
+////        {
+////            var target = CreateTarget();
+////            var items = (IList<string>)target.Items;
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var containers = target.Panel.Children.ToList();
-            var scroller = (ScrollContentPresenter)target.Parent;
+////            var containers = target.Panel.Children.ToList();
+////            var scroller = (ScrollContentPresenter)target.Parent;
 
-            scroller.Offset = new Vector(0, 5);
+////            scroller.Offset = new Vector(0, 5);
 
-            var scrolledContainers = containers
-                .Skip(5)
-                .Take(5)
-                .Concat(containers.Take(5)).ToList();
+////            var scrolledContainers = containers
+////                .Skip(5)
+////                .Take(5)
+////                .Concat(containers.Take(5)).ToList();
 
-            Assert.Equal(new Vector(0, 5), ((ILogicalScrollable)target).Offset);
-            Assert.Equal(scrolledContainers, target.Panel.Children);
+////            Assert.Equal(new Vector(0, 5), ((ILogicalScrollable)target).Offset);
+////            Assert.Equal(scrolledContainers, target.Panel.Children);
 
-            for (var i = 0; i < target.Panel.Children.Count; ++i)
-            {
-                Assert.Equal(items[i + 5], target.Panel.Children[i].DataContext);
-            }
+////            for (var i = 0; i < target.Panel.Children.Count; ++i)
+////            {
+////                Assert.Equal(items[i + 5], target.Panel.Children[i].DataContext);
+////            }
 
-            scroller.Offset = new Vector(0, 0);
-            Assert.Equal(new Vector(0, 0), ((ILogicalScrollable)target).Offset);
-            Assert.Equal(containers, target.Panel.Children);
+////            scroller.Offset = new Vector(0, 0);
+////            Assert.Equal(new Vector(0, 0), ((ILogicalScrollable)target).Offset);
+////            Assert.Equal(containers, target.Panel.Children);
 
-            var dcs = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var dcs = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            for (var i = 0; i < target.Panel.Children.Count; ++i)
-            {
-                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
-            }
-        }
+////            for (var i = 0; i < target.Panel.Children.Count; ++i)
+////            {
+////                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
+////            }
+////        }
 
-        [Fact]
-        public void Scrolling_More_Than_A_Page_Should_Recycle_Items()
-        {
-            var target = CreateTarget(itemCount: 50);
-            var items = (IList<string>)target.Items;
+////        [Fact]
+////        public void Scrolling_More_Than_A_Page_Should_Recycle_Items()
+////        {
+////            var target = CreateTarget(itemCount: 50);
+////            var items = (IList<string>)target.Items;
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var containers = target.Panel.Children.ToList();
-            var scroller = (ScrollContentPresenter)target.Parent;
+////            var containers = target.Panel.Children.ToList();
+////            var scroller = (ScrollContentPresenter)target.Parent;
 
-            scroller.Offset = new Vector(0, 20);
+////            scroller.Offset = new Vector(0, 20);
 
-            Assert.Equal(new Vector(0, 20), ((ILogicalScrollable)target).Offset);
-            Assert.Equal(containers, target.Panel.Children);
+////            Assert.Equal(new Vector(0, 20), ((ILogicalScrollable)target).Offset);
+////            Assert.Equal(containers, target.Panel.Children);
 
-            for (var i = 0; i < target.Panel.Children.Count; ++i)
-            {
-                Assert.Equal(items[i + 20], target.Panel.Children[i].DataContext);
-            }
+////            for (var i = 0; i < target.Panel.Children.Count; ++i)
+////            {
+////                Assert.Equal(items[i + 20], target.Panel.Children[i].DataContext);
+////            }
 
-            scroller.Offset = new Vector(0, 0);
+////            scroller.Offset = new Vector(0, 0);
 
-            Assert.Equal(new Vector(0, 0), ((ILogicalScrollable)target).Offset);
-            Assert.Equal(containers, target.Panel.Children);
+////            Assert.Equal(new Vector(0, 0), ((ILogicalScrollable)target).Offset);
+////            Assert.Equal(containers, target.Panel.Children);
 
-            for (var i = 0; i < target.Panel.Children.Count; ++i)
-            {
-                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
-            }
-        }
+////            for (var i = 0; i < target.Panel.Children.Count; ++i)
+////            {
+////                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
+////            }
+////        }
 
-        public class Vertical
-        {
-            [Fact]
-            public void GetControlInDirection_Down_Should_Return_Existing_Container_If_Materialized()
-            {
-                var target = CreateTarget();
-                var scroller = (TestScroller)target.Parent;
+////        public class Vertical
+////        {
+////            [Fact]
+////            public void GetControlInDirection_Down_Should_Return_Existing_Container_If_Materialized()
+////            {
+////                var target = CreateTarget();
+////                var scroller = (TestScroller)target.Parent;
 
-                scroller.Width = scroller.Height = 100;
-                scroller.LayoutManager.ExecuteInitialLayoutPass();
+////                scroller.Width = scroller.Height = 100;
+////                scroller.LayoutManager.ExecuteInitialLayoutPass();
 
-                var from = target.Panel.Children[5];
-                var result = ((ILogicalScrollable)target).GetControlInDirection(
-                    NavigationDirection.Down,
-                    from);
-
-                Assert.Same(target.Panel.Children[6], result);
-            }
-
-            [Fact]
-            public void GetControlInDirection_Down_Should_Scroll_If_Necessary()
-            {
-                var target = CreateTarget();
-                var scroller = (TestScroller)target.Parent;
-
-                scroller.Width = scroller.Height = 100;
-                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-                var from = target.Panel.Children[9];
-                var result = ((ILogicalScrollable)target).GetControlInDirection(
-                    NavigationDirection.Down,
-                    from);
-
-                Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-                Assert.Same(target.Panel.Children[9], result);
-            }
-
-            [Fact]
-            public void GetControlInDirection_Down_Should_Scroll_If_Partially_Visible()
-            {
-                var target = CreateTarget();
-                var scroller = (TestScroller)target.Parent;
-
-                scroller.Width = 100;
-                scroller.Height = 95;
-                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-                var from = target.Panel.Children[8];
-                var result = ((ILogicalScrollable)target).GetControlInDirection(
-                    NavigationDirection.Down,
-                    from);
-
-                Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-                Assert.Same(target.Panel.Children[8], result);
-            }
-
-            [Fact]
-            public void GetControlInDirection_Up_Should_Scroll_If_Partially_Visible_Item_Is_Currently_Shown()
-            {
-                var target = CreateTarget();
-                var scroller = (TestScroller)target.Parent;
-
-                scroller.Width = 100;
-                scroller.Height = 95;
-                scroller.LayoutManager.ExecuteInitialLayoutPass();
-                ((ILogicalScrollable)target).Offset = new Vector(0, 11);
-
-                var from = target.Panel.Children[1];
-                var result = ((ILogicalScrollable)target).GetControlInDirection(
-                    NavigationDirection.Up,
-                    from);
-
-                Assert.Equal(new Vector(0, 10), ((ILogicalScrollable)target).Offset);
-                Assert.Same(target.Panel.Children[0], result);
-            }
-
-            [Fact]
-            public void Should_Return_Horizontal_Extent_And_Viewport()
-            {
-                var target = CreateTarget();
-
-                target.ApplyTemplate();
-                target.Measure(new Size(5, 100));
-                target.Arrange(new Rect(0, 0, 5, 100));
-
-                Assert.Equal(new Size(10, 20), ((ILogicalScrollable)target).Extent);
-                Assert.Equal(new Size(5, 10), ((ILogicalScrollable)target).Viewport);
-            }
-
-            [Fact]
-            public void Horizontal_Scroll_Should_Update_Item_Position()
-            {
-                var target = CreateTarget();
-
-                target.ApplyTemplate();
-
-                target.Measure(new Size(5, 100));
-                target.Arrange(new Rect(0, 0, 5, 100));
-
-                ((ILogicalScrollable)target).Offset = new Vector(5, 0);
-
-                target.Measure(new Size(5, 100));
-                target.Arrange(new Rect(0, 0, 5, 100));
-
-                Assert.Equal(new Rect(-5, 0, 10, 10), target.Panel.Children[0].Bounds);
-            }
-        }
-
-        public class Horizontal
-        {
-            [Fact]
-            public void GetControlInDirection_Right_Should_Return_Existing_Container_If_Materialized()
-            {
-                var target = CreateTarget(orientation: Orientation.Horizontal);
-                var scroller = (TestScroller)target.Parent;
-
-                scroller.Width = scroller.Height = 100;
-                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-                var from = target.Panel.Children[5];
-                var result = ((ILogicalScrollable)target).GetControlInDirection(
-                    NavigationDirection.Right,
-                    from);
-
-                Assert.Same(target.Panel.Children[6], result);
-            }
-
-            [Fact]
-            public void GetControlInDirection_Right_Should_Scroll_If_Necessary()
-            {
-                var target = CreateTarget(orientation: Orientation.Horizontal);
-                var scroller = (TestScroller)target.Parent;
-
-                scroller.Width = scroller.Height = 100;
-                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-                var from = target.Panel.Children[9];
-                var result = ((ILogicalScrollable)target).GetControlInDirection(
-                    NavigationDirection.Right,
-                    from);
-
-                Assert.Equal(new Vector(1, 0), ((ILogicalScrollable)target).Offset);
-                Assert.Same(target.Panel.Children[9], result);
-            }
-
-            [Fact]
-            public void GetControlInDirection_Right_Should_Scroll_If_Partially_Visible()
-            {
-                var target = CreateTarget(orientation: Orientation.Horizontal);
-                var scroller = (TestScroller)target.Parent;
-
-                scroller.Width = 95;
-                scroller.Height = 100;
-                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-                var from = target.Panel.Children[8];
-                var result = ((ILogicalScrollable)target).GetControlInDirection(
-                    NavigationDirection.Right,
-                    from);
-
-                Assert.Equal(new Vector(1, 0), ((ILogicalScrollable)target).Offset);
-                Assert.Same(target.Panel.Children[8], result);
-            }
-
-            [Fact]
-            public void GetControlInDirection_Left_Should_Scroll_If_Partially_Visible_Item_Is_Currently_Shown()
-            {
-                var target = CreateTarget(orientation: Orientation.Horizontal);
-                var scroller = (TestScroller)target.Parent;
-
-                scroller.Width = 95;
-                scroller.Height = 100;
-                scroller.LayoutManager.ExecuteInitialLayoutPass();
-                ((ILogicalScrollable)target).Offset = new Vector(11, 0);
-
-                var from = target.Panel.Children[1];
-                var result = ((ILogicalScrollable)target).GetControlInDirection(
-                    NavigationDirection.Left,
-                    from);
-
-                Assert.Equal(new Vector(10, 0), ((ILogicalScrollable)target).Offset);
-                Assert.Same(target.Panel.Children[0], result);
-            }
-        }
-
-        private static ItemsPresenter CreateTarget(
-            Orientation orientation = Orientation.Vertical,
-            int itemCount = 20,
-            bool useAvaloniaList = false)
-        {
-            ItemsPresenter result;
-            var itemsSource = Enumerable.Range(0, itemCount).Select(x => $"Item {x}");
-            var items = useAvaloniaList ?
-                (IEnumerable)new AvaloniaList<string>(itemsSource) :
-                (IEnumerable)new ObservableCollection<string>(itemsSource);
-
-            var scroller = new TestScroller
-            {
-                CanHorizontallyScroll = true,
-                CanVerticallyScroll = true,
-                Content = result = new TestItemsPresenter
-                {
-                    Items = items,
-                    ItemsPanel = VirtualizingPanelTemplate(orientation),
-                    DataTemplates = { StringDataTemplate() },
-                    VirtualizationMode = ItemVirtualizationMode.Simple,
-                }
-            };
-
-            scroller.UpdateChild();
-            return result;
-        }
-
-        private static IDataTemplate StringDataTemplate()
-        {
-            return new FuncDataTemplate<string>((x, _) => new Canvas
-            {
-                Width = 10,
-                Height = 10,
-            });
-        }
-
-        private static ITemplate<Panel> VirtualizingPanelTemplate(
-            Orientation orientation = Orientation.Vertical)
-        {
-            return new FuncTemplate<Panel>(() => new VirtualizingStackPanel
-            {
-                Orientation = orientation,
-            });
-        }
-
-        private class TestScroller : ScrollContentPresenter, IRenderRoot, ILayoutRoot, ILogicalRoot
-        {
-            public TestScroller()
-            {
-                LayoutManager = new LayoutManager(this);
-            }
-
-            public IRenderer Renderer { get; }
-            public Size ClientSize { get; }
-            public double RenderScaling => 1;
-
-            public Size MaxClientSize => Size.Infinity;
-
-            public double LayoutScaling => 1;
-
-            public ILayoutManager LayoutManager { get; }
-
-            public IRenderTarget CreateRenderTarget() => throw new NotImplementedException();
-            public void Invalidate(Rect rect) => throw new NotImplementedException();
-            public Point PointToClient(PixelPoint p) => throw new NotImplementedException();
-            public PixelPoint PointToScreen(Point p) => throw new NotImplementedException();
-        }
-
-        private class TestItemsPresenter : ItemsPresenter
-        {
-            protected override IItemContainerGenerator CreateItemContainerGenerator()
-            {
-                return new ItemContainerGenerator<TestContainer>(
-                    this,
-                    TestContainer.ContentProperty,
-                    null);
-            }
-        }
-
-        private class TestContainer : ContentControl
-        {
-            public TestContainer()
-            {
-                Template = new FuncControlTemplate<TestContainer>((parent, scope) => new ContentPresenter
-                {
-                    Name = "PART_ContentPresenter",
-                    [~ContentPresenter.ContentProperty] = parent[~ContentControl.ContentProperty],
-                    [~ContentPresenter.ContentTemplateProperty] = parent[~ContentControl.ContentTemplateProperty],
-                }.RegisterInNameScope(scope));
-            }
-        }
-    }
-}
+////                var from = target.Panel.Children[5];
+////                var result = ((ILogicalScrollable)target).GetControlInDirection(
+////                    NavigationDirection.Down,
+////                    from);
+
+////                Assert.Same(target.Panel.Children[6], result);
+////            }
+
+////            [Fact]
+////            public void GetControlInDirection_Down_Should_Scroll_If_Necessary()
+////            {
+////                var target = CreateTarget();
+////                var scroller = (TestScroller)target.Parent;
+
+////                scroller.Width = scroller.Height = 100;
+////                scroller.LayoutManager.ExecuteInitialLayoutPass();
+
+////                var from = target.Panel.Children[9];
+////                var result = ((ILogicalScrollable)target).GetControlInDirection(
+////                    NavigationDirection.Down,
+////                    from);
+
+////                Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
+////                Assert.Same(target.Panel.Children[9], result);
+////            }
+
+////            [Fact]
+////            public void GetControlInDirection_Down_Should_Scroll_If_Partially_Visible()
+////            {
+////                var target = CreateTarget();
+////                var scroller = (TestScroller)target.Parent;
+
+////                scroller.Width = 100;
+////                scroller.Height = 95;
+////                scroller.LayoutManager.ExecuteInitialLayoutPass();
+
+////                var from = target.Panel.Children[8];
+////                var result = ((ILogicalScrollable)target).GetControlInDirection(
+////                    NavigationDirection.Down,
+////                    from);
+
+////                Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
+////                Assert.Same(target.Panel.Children[8], result);
+////            }
+
+////            [Fact]
+////            public void GetControlInDirection_Up_Should_Scroll_If_Partially_Visible_Item_Is_Currently_Shown()
+////            {
+////                var target = CreateTarget();
+////                var scroller = (TestScroller)target.Parent;
+
+////                scroller.Width = 100;
+////                scroller.Height = 95;
+////                scroller.LayoutManager.ExecuteInitialLayoutPass();
+////                ((ILogicalScrollable)target).Offset = new Vector(0, 11);
+
+////                var from = target.Panel.Children[1];
+////                var result = ((ILogicalScrollable)target).GetControlInDirection(
+////                    NavigationDirection.Up,
+////                    from);
+
+////                Assert.Equal(new Vector(0, 10), ((ILogicalScrollable)target).Offset);
+////                Assert.Same(target.Panel.Children[0], result);
+////            }
+
+////            [Fact]
+////            public void Should_Return_Horizontal_Extent_And_Viewport()
+////            {
+////                var target = CreateTarget();
+
+////                target.ApplyTemplate();
+////                target.Measure(new Size(5, 100));
+////                target.Arrange(new Rect(0, 0, 5, 100));
+
+////                Assert.Equal(new Size(10, 20), ((ILogicalScrollable)target).Extent);
+////                Assert.Equal(new Size(5, 10), ((ILogicalScrollable)target).Viewport);
+////            }
+
+////            [Fact]
+////            public void Horizontal_Scroll_Should_Update_Item_Position()
+////            {
+////                var target = CreateTarget();
+
+////                target.ApplyTemplate();
+
+////                target.Measure(new Size(5, 100));
+////                target.Arrange(new Rect(0, 0, 5, 100));
+
+////                ((ILogicalScrollable)target).Offset = new Vector(5, 0);
+
+////                target.Measure(new Size(5, 100));
+////                target.Arrange(new Rect(0, 0, 5, 100));
+
+////                Assert.Equal(new Rect(-5, 0, 10, 10), target.Panel.Children[0].Bounds);
+////            }
+////        }
+
+////        public class Horizontal
+////        {
+////            [Fact]
+////            public void GetControlInDirection_Right_Should_Return_Existing_Container_If_Materialized()
+////            {
+////                var target = CreateTarget(orientation: Orientation.Horizontal);
+////                var scroller = (TestScroller)target.Parent;
+
+////                scroller.Width = scroller.Height = 100;
+////                scroller.LayoutManager.ExecuteInitialLayoutPass();
+
+////                var from = target.Panel.Children[5];
+////                var result = ((ILogicalScrollable)target).GetControlInDirection(
+////                    NavigationDirection.Right,
+////                    from);
+
+////                Assert.Same(target.Panel.Children[6], result);
+////            }
+
+////            [Fact]
+////            public void GetControlInDirection_Right_Should_Scroll_If_Necessary()
+////            {
+////                var target = CreateTarget(orientation: Orientation.Horizontal);
+////                var scroller = (TestScroller)target.Parent;
+
+////                scroller.Width = scroller.Height = 100;
+////                scroller.LayoutManager.ExecuteInitialLayoutPass();
+
+////                var from = target.Panel.Children[9];
+////                var result = ((ILogicalScrollable)target).GetControlInDirection(
+////                    NavigationDirection.Right,
+////                    from);
+
+////                Assert.Equal(new Vector(1, 0), ((ILogicalScrollable)target).Offset);
+////                Assert.Same(target.Panel.Children[9], result);
+////            }
+
+////            [Fact]
+////            public void GetControlInDirection_Right_Should_Scroll_If_Partially_Visible()
+////            {
+////                var target = CreateTarget(orientation: Orientation.Horizontal);
+////                var scroller = (TestScroller)target.Parent;
+
+////                scroller.Width = 95;
+////                scroller.Height = 100;
+////                scroller.LayoutManager.ExecuteInitialLayoutPass();
+
+////                var from = target.Panel.Children[8];
+////                var result = ((ILogicalScrollable)target).GetControlInDirection(
+////                    NavigationDirection.Right,
+////                    from);
+
+////                Assert.Equal(new Vector(1, 0), ((ILogicalScrollable)target).Offset);
+////                Assert.Same(target.Panel.Children[8], result);
+////            }
+
+////            [Fact]
+////            public void GetControlInDirection_Left_Should_Scroll_If_Partially_Visible_Item_Is_Currently_Shown()
+////            {
+////                var target = CreateTarget(orientation: Orientation.Horizontal);
+////                var scroller = (TestScroller)target.Parent;
+
+////                scroller.Width = 95;
+////                scroller.Height = 100;
+////                scroller.LayoutManager.ExecuteInitialLayoutPass();
+////                ((ILogicalScrollable)target).Offset = new Vector(11, 0);
+
+////                var from = target.Panel.Children[1];
+////                var result = ((ILogicalScrollable)target).GetControlInDirection(
+////                    NavigationDirection.Left,
+////                    from);
+
+////                Assert.Equal(new Vector(10, 0), ((ILogicalScrollable)target).Offset);
+////                Assert.Same(target.Panel.Children[0], result);
+////            }
+////        }
+
+////        private static ItemsPresenter CreateTarget(
+////            Orientation orientation = Orientation.Vertical,
+////            int itemCount = 20,
+////            bool useAvaloniaList = false)
+////        {
+////            ItemsPresenter result;
+////            var itemsSource = Enumerable.Range(0, itemCount).Select(x => $"Item {x}");
+////            var items = useAvaloniaList ?
+////                (IEnumerable)new AvaloniaList<string>(itemsSource) :
+////                (IEnumerable)new ObservableCollection<string>(itemsSource);
+
+////            var scroller = new TestScroller
+////            {
+////                CanHorizontallyScroll = true,
+////                CanVerticallyScroll = true,
+////                Content = result = new TestItemsPresenter
+////                {
+////                    Items = items,
+////                    ItemsPanel = VirtualizingPanelTemplate(orientation),
+////                    DataTemplates = { StringDataTemplate() },
+////                    VirtualizationMode = ItemVirtualizationMode.Simple,
+////                }
+////            };
+
+////            scroller.UpdateChild();
+////            return result;
+////        }
+
+////        private static IDataTemplate StringDataTemplate()
+////        {
+////            return new FuncDataTemplate<string>((x, _) => new Canvas
+////            {
+////                Width = 10,
+////                Height = 10,
+////            });
+////        }
+
+////        private static ITemplate<Panel> VirtualizingPanelTemplate(
+////            Orientation orientation = Orientation.Vertical)
+////        {
+////            return new FuncTemplate<Panel>(() => new VirtualizingStackPanel
+////            {
+////                Orientation = orientation,
+////            });
+////        }
+
+////        private class TestScroller : ScrollContentPresenter, IRenderRoot, ILayoutRoot, ILogicalRoot
+////        {
+////            public TestScroller()
+////            {
+////                LayoutManager = new LayoutManager(this);
+////            }
+
+////            public IRenderer Renderer { get; }
+////            public Size ClientSize { get; }
+////            public double RenderScaling => 1;
+
+////            public Size MaxClientSize => Size.Infinity;
+
+////            public double LayoutScaling => 1;
+
+////            public ILayoutManager LayoutManager { get; }
+
+////            public IRenderTarget CreateRenderTarget() => throw new NotImplementedException();
+////            public void Invalidate(Rect rect) => throw new NotImplementedException();
+////            public Point PointToClient(PixelPoint p) => throw new NotImplementedException();
+////            public PixelPoint PointToScreen(Point p) => throw new NotImplementedException();
+////        }
+
+////        private class TestItemsPresenter : ItemsPresenter
+////        {
+////            protected override IItemContainerGenerator CreateItemContainerGenerator()
+////            {
+////                return new ItemContainerGenerator<TestContainer>(
+////                    this,
+////                    TestContainer.ContentProperty,
+////                    null);
+////            }
+////        }
+
+////        private class TestContainer : ContentControl
+////        {
+////            public TestContainer()
+////            {
+////                Template = new FuncControlTemplate<TestContainer>((parent, scope) => new ContentPresenter
+////                {
+////                    Name = "PART_ContentPresenter",
+////                    [~ContentPresenter.ContentProperty] = parent[~ContentControl.ContentProperty],
+////                    [~ContentPresenter.ContentTemplateProperty] = parent[~ContentControl.ContentTemplateProperty],
+////                }.RegisterInNameScope(scope));
+////            }
+////        }
+////    }
+////}
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs
index d4193d33ee4..a9e1c65c50e 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs
@@ -1115,10 +1115,7 @@ private static Control PopupItemsControlTemplate(PopupItemsControl control, INam
             {
                 Name = "popup",
                 PlacementTarget = control,
-                Child = new ItemsPresenter
-                {
-                    [~ItemsPresenter.ItemsProperty] = control[~ItemsControl.ItemsProperty],
-                }
+                Child = new ItemsPresenter(),
             }.RegisterInNameScope(scope);
         }
 
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
index e20c03f67f9..2c57c20b6c0 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
@@ -2090,9 +2090,7 @@ private static FuncControlTemplate Template()
                 new ItemsPresenter
                 {
                     Name = "itemsPresenter",
-                    [~ItemsPresenter.ItemsProperty] = control[~ItemsControl.ItemsProperty],
                     [~ItemsPresenter.ItemsPanelProperty] = control[~ItemsControl.ItemsPanelProperty],
-                    [~ItemsPresenter.VirtualizationModeProperty] = control[~ListBox.VirtualizationModeProperty],
                 }.RegisterInNameScope(scope));
         }
 
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_AutoSelect.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_AutoSelect.cs
index d2537a06350..c3e37666f71 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_AutoSelect.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_AutoSelect.cs
@@ -125,7 +125,6 @@ private static FuncControlTemplate Template()
                 new ItemsPresenter
                 {
                     Name = "itemsPresenter",
-                    [~ItemsPresenter.ItemsProperty] = control[~ItemsControl.ItemsProperty],
                     [~ItemsPresenter.ItemsPanelProperty] = control[~ItemsControl.ItemsPanelProperty],
                 }.RegisterInNameScope(scope));
         }
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
index bc6147d64cc..efce0a715c8 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
@@ -1536,7 +1536,6 @@ private static FuncControlTemplate Template()
                 new ItemsPresenter
                 {
                     Name = "PART_ItemsPresenter",
-                    [~ItemsPresenter.ItemsProperty] = control[~ItemsControl.ItemsProperty],
                     [~ItemsPresenter.ItemsPanelProperty] = control[~ItemsControl.ItemsPanelProperty],
                 }.RegisterInNameScope(scope));
         }
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/TabStripTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/TabStripTests.cs
index b1e18dc5878..05183fe7875 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/TabStripTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/TabStripTests.cs
@@ -106,7 +106,6 @@ private Control CreateTabStripTemplate(TabStrip parent, INameScope scope)
             return new ItemsPresenter
             {
                 Name = "itemsPresenter",
-                [!ItemsPresenter.ItemsProperty] = parent[!ItemsControl.ItemsProperty],
             }.RegisterInNameScope(scope);
         }
     }
diff --git a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
index 4f0446d4067..8be1e112e79 100644
--- a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
@@ -1303,7 +1303,6 @@ private IControlTemplate CreateTreeViewTemplate()
             return new FuncControlTemplate<TreeView>((parent, scope) => new ItemsPresenter
             {
                 Name = "PART_ItemsPresenter",
-                [~ItemsPresenter.ItemsProperty] = parent[~ItemsControl.ItemsProperty],
             }.RegisterInNameScope(scope));
         }
 
@@ -1321,7 +1320,6 @@ private IControlTemplate CreateTreeViewItemTemplate()
                     new ItemsPresenter
                     {
                         Name = "PART_ItemsPresenter",
-                        [~ItemsPresenter.ItemsProperty] = parent[~ItemsControl.ItemsProperty],
                     }.RegisterInNameScope(scope)
                 }
             });
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
index b80df2c5d30..6270d698e7b 100644
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
@@ -1,261 +1,261 @@
-using System;
-using System.Collections.Generic;
-using Avalonia.Controls.Primitives;
-using Avalonia.Input;
-using Avalonia.LogicalTree;
-using Moq;
-using Xunit;
-
-namespace Avalonia.Controls.UnitTests
-{
-    public class VirtualizingStackPanelTests
-    {
-        public class Vertical
-        {
-            [Fact]
-            public void Measure_Invokes_Controller_UpdateControls()
-            {
-                var target = new VirtualizingStackPanel();
-                var controller = new Mock<IVirtualizingController>();
-
-                ((IVirtualizingPanel)target).Controller = controller.Object;
-                target.Measure(new Size(100, 100));
-
-                controller.Verify(x => x.UpdateControls(), Times.Once());
-            }
-
-            [Fact]
-            public void Measure_Invokes_Controller_UpdateControls_If_AvailableSize_Changes()
-            {
-                var target = new VirtualizingStackPanel();
-                var controller = new Mock<IVirtualizingController>();
-
-                ((IVirtualizingPanel)target).Controller = controller.Object;
-                target.Measure(new Size(100, 100));
-                target.InvalidateMeasure();
-                target.Measure(new Size(100, 100));
-                target.InvalidateMeasure();
-                target.Measure(new Size(100, 101));
-
-                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
-            }
-
-            [Fact]
-            public void Measure_Does_Not_Invoke_Controller_UpdateControls_If_AvailableSize_Is_The_Same()
-            {
-                var target = new VirtualizingStackPanel();
-                var controller = new Mock<IVirtualizingController>();
-
-                ((IVirtualizingPanel)target).Controller = controller.Object;
-                target.Measure(new Size(100, 100));
-                target.InvalidateMeasure();
-                target.Measure(new Size(100, 100));
-
-                controller.Verify(x => x.UpdateControls(), Times.Once());
-            }
-
-            [Fact]
-            public void Measure_Invokes_Controller_UpdateControls_If_AvailableSize_Is_The_Same_After_ForceInvalidateMeasure()
-            {
-                var target = new VirtualizingStackPanel();
-                var controller = new Mock<IVirtualizingController>();
-
-                ((IVirtualizingPanel)target).Controller = controller.Object;
-                target.Measure(new Size(100, 100));
-                ((IVirtualizingPanel)target).ForceInvalidateMeasure();
-                target.Measure(new Size(100, 100));
-
-                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
-            }
-
-            [Fact]
-            public void Arrange_Invokes_Controller_UpdateControls()
-            {
-                var target = new VirtualizingStackPanel();
-                var controller = new Mock<IVirtualizingController>();
-
-                ((IVirtualizingPanel)target).Controller = controller.Object;
-                target.Measure(new Size(100, 100));
-                target.Arrange(new Rect(0, 0, 110, 110));
-
-                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
-            }
-
-            [Fact]
-            public void Reports_IsFull_False_Until_Measure_Height_Is_Reached()
-            {
-                var target = new VirtualizingStackPanel();
-                var vp = (IVirtualizingPanel)target;
-
-                target.Measure(new Size(100, 100));
-
-                Assert.Equal(new Size(0, 0), target.DesiredSize);
-                Assert.Equal(new Size(0, 0), target.Bounds.Size);
-
-                Assert.False(vp.IsFull);
-                Assert.Equal(0, vp.OverflowCount);
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                Assert.False(vp.IsFull);
-                Assert.Equal(0, vp.OverflowCount);
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                Assert.True(vp.IsFull);
-                Assert.Equal(0, vp.OverflowCount);
-            }
-
-            [Fact]
-            public void Reports_Overflow_After_Arrange()
-            {
-                var target = new VirtualizingStackPanel();
-                var vp = (IVirtualizingPanel)target;
-
-                target.Measure(new Size(100, 100));
-                target.Arrange(new Rect(target.DesiredSize));
-
-                Assert.Equal(new Size(0, 0), target.Bounds.Size);
-
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                Assert.Equal(0, vp.OverflowCount);
-
-                target.Measure(new Size(100, 100));
-                target.Arrange(new Rect(target.DesiredSize));
-
-                Assert.Equal(2, vp.OverflowCount);
-            }
-
-            [Fact]
-            public void Reports_Correct_Overflow_During_Arrange()
-            {
-                var target = new VirtualizingStackPanel();
-                var vp = (IVirtualizingPanel)target;
-                var controller = new Mock<IVirtualizingController>();
-                var called = false;
-
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-                target.Measure(new Size(100, 100));
-
-                controller.Setup(x => x.UpdateControls()).Callback(() =>
-                {
-                    Assert.Equal(2, vp.PixelOverflow);
-                    Assert.Equal(0, vp.OverflowCount);
-                    called = true;
-                });
-
-                vp.Controller = controller.Object;
-                target.Arrange(new Rect(target.DesiredSize));
-
-                Assert.True(called);
-            }
-
-            [Fact]
-            public void Reports_PixelOverflow_After_Arrange()
-            {
-                var target = new VirtualizingStackPanel();
-
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-
-                target.Measure(new Size(100, 100));
-                target.Arrange(new Rect(target.DesiredSize));
-
-                Assert.Equal(2, ((IVirtualizingPanel)target).PixelOverflow);
-            }
-
-            [Fact]
-            public void Reports_PixelOverflow_After_Arrange_Smaller_Than_Measure()
-            {
-                var target = new VirtualizingStackPanel();
-
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-
-                target.Measure(new Size(100, 100));
-                target.Arrange(new Rect(0, 0, 50, 50));
-
-                Assert.Equal(52, ((IVirtualizingPanel)target).PixelOverflow);
-            }
-
-            [Fact]
-            public void Reports_PixelOverflow_With_PixelOffset()
-            {
-                var target = new VirtualizingStackPanel();
-                var vp = (IVirtualizingPanel)target;
-
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-                vp.PixelOffset = 2;
-
-                target.Measure(new Size(100, 100));
-                target.Arrange(new Rect(target.DesiredSize));
-
-                Assert.Equal(2, vp.PixelOverflow);
-            }
-
-            [Fact]
-            public void PixelOffset_Can_Be_More_Than_Child_Without_Affecting_IsFull()
-            {
-                var target = new VirtualizingStackPanel();
-                var vp = (IVirtualizingPanel)target;
-
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-                vp.PixelOffset = 55;
-
-                target.Measure(new Size(100, 100));
-                target.Arrange(new Rect(target.DesiredSize));
-
-                Assert.Equal(55, vp.PixelOffset);
-                Assert.Equal(2, vp.PixelOverflow);
-                Assert.True(vp.IsFull);
-            }
-
-            [Fact]
-            public void Passes_Navigation_Request_To_ILogicalScrollable_Parent()
-            {
-                var target = new VirtualizingStackPanel();
-                var presenter = new TestPresenter { Child = target };
-                var from = new Canvas();
-
-                ((INavigableContainer)target).GetControl(NavigationDirection.Next, from, false);
-
-                Assert.Equal(1, presenter.NavigationRequests.Count);
-                Assert.Equal((NavigationDirection.Next, from), presenter.NavigationRequests[0]);
-            }
-
-            private class TestPresenter : Decorator, ILogicalScrollable
-            {
-                public bool CanHorizontallyScroll { get; set; }
-                public bool CanVerticallyScroll { get; set; }
-                public bool IsLogicalScrollEnabled => true;
-                public Size ScrollSize { get; }
-                public Size PageScrollSize { get; }
-                public Size Extent { get; }
-                public Vector Offset { get; set; }
-                public Size Viewport { get; }
-
-                public event EventHandler ScrollInvalidated;
-
-                public List<(NavigationDirection, Control)> NavigationRequests { get; } = new();
-
-                public bool BringIntoView(Control target, Rect targetRect)
-                {
-                    throw new NotImplementedException();
-                }
-
-                public Control GetControlInDirection(NavigationDirection direction, Control from)
-                {
-                    NavigationRequests.Add((direction, from));
-                    return null;
-                }
-
-                public void RaiseScrollInvalidated(EventArgs e)
-                {
-                    throw new NotImplementedException();
-                }
-            }
-        }
-    }
-}
+////using System;
+////using System.Collections.Generic;
+////using Avalonia.Controls.Primitives;
+////using Avalonia.Input;
+////using Avalonia.LogicalTree;
+////using Moq;
+////using Xunit;
+
+////namespace Avalonia.Controls.UnitTests
+////{
+////    public class VirtualizingStackPanelTests
+////    {
+////        public class Vertical
+////        {
+////            [Fact]
+////            public void Measure_Invokes_Controller_UpdateControls()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var controller = new Mock<IVirtualizingController>();
+
+////                ((IVirtualizingPanel)target).Controller = controller.Object;
+////                target.Measure(new Size(100, 100));
+
+////                controller.Verify(x => x.UpdateControls(), Times.Once());
+////            }
+
+////            [Fact]
+////            public void Measure_Invokes_Controller_UpdateControls_If_AvailableSize_Changes()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var controller = new Mock<IVirtualizingController>();
+
+////                ((IVirtualizingPanel)target).Controller = controller.Object;
+////                target.Measure(new Size(100, 100));
+////                target.InvalidateMeasure();
+////                target.Measure(new Size(100, 100));
+////                target.InvalidateMeasure();
+////                target.Measure(new Size(100, 101));
+
+////                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
+////            }
+
+////            [Fact]
+////            public void Measure_Does_Not_Invoke_Controller_UpdateControls_If_AvailableSize_Is_The_Same()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var controller = new Mock<IVirtualizingController>();
+
+////                ((IVirtualizingPanel)target).Controller = controller.Object;
+////                target.Measure(new Size(100, 100));
+////                target.InvalidateMeasure();
+////                target.Measure(new Size(100, 100));
+
+////                controller.Verify(x => x.UpdateControls(), Times.Once());
+////            }
+
+////            [Fact]
+////            public void Measure_Invokes_Controller_UpdateControls_If_AvailableSize_Is_The_Same_After_ForceInvalidateMeasure()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var controller = new Mock<IVirtualizingController>();
+
+////                ((IVirtualizingPanel)target).Controller = controller.Object;
+////                target.Measure(new Size(100, 100));
+////                ((IVirtualizingPanel)target).ForceInvalidateMeasure();
+////                target.Measure(new Size(100, 100));
+
+////                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
+////            }
+
+////            [Fact]
+////            public void Arrange_Invokes_Controller_UpdateControls()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var controller = new Mock<IVirtualizingController>();
+
+////                ((IVirtualizingPanel)target).Controller = controller.Object;
+////                target.Measure(new Size(100, 100));
+////                target.Arrange(new Rect(0, 0, 110, 110));
+
+////                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
+////            }
+
+////            [Fact]
+////            public void Reports_IsFull_False_Until_Measure_Height_Is_Reached()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var vp = (IVirtualizingPanel)target;
+
+////                target.Measure(new Size(100, 100));
+
+////                Assert.Equal(new Size(0, 0), target.DesiredSize);
+////                Assert.Equal(new Size(0, 0), target.Bounds.Size);
+
+////                Assert.False(vp.IsFull);
+////                Assert.Equal(0, vp.OverflowCount);
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                Assert.False(vp.IsFull);
+////                Assert.Equal(0, vp.OverflowCount);
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                Assert.True(vp.IsFull);
+////                Assert.Equal(0, vp.OverflowCount);
+////            }
+
+////            [Fact]
+////            public void Reports_Overflow_After_Arrange()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var vp = (IVirtualizingPanel)target;
+
+////                target.Measure(new Size(100, 100));
+////                target.Arrange(new Rect(target.DesiredSize));
+
+////                Assert.Equal(new Size(0, 0), target.Bounds.Size);
+
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                Assert.Equal(0, vp.OverflowCount);
+
+////                target.Measure(new Size(100, 100));
+////                target.Arrange(new Rect(target.DesiredSize));
+
+////                Assert.Equal(2, vp.OverflowCount);
+////            }
+
+////            [Fact]
+////            public void Reports_Correct_Overflow_During_Arrange()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var vp = (IVirtualizingPanel)target;
+////                var controller = new Mock<IVirtualizingController>();
+////                var called = false;
+
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
+////                target.Measure(new Size(100, 100));
+
+////                controller.Setup(x => x.UpdateControls()).Callback(() =>
+////                {
+////                    Assert.Equal(2, vp.PixelOverflow);
+////                    Assert.Equal(0, vp.OverflowCount);
+////                    called = true;
+////                });
+
+////                vp.Controller = controller.Object;
+////                target.Arrange(new Rect(target.DesiredSize));
+
+////                Assert.True(called);
+////            }
+
+////            [Fact]
+////            public void Reports_PixelOverflow_After_Arrange()
+////            {
+////                var target = new VirtualizingStackPanel();
+
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
+
+////                target.Measure(new Size(100, 100));
+////                target.Arrange(new Rect(target.DesiredSize));
+
+////                Assert.Equal(2, ((IVirtualizingPanel)target).PixelOverflow);
+////            }
+
+////            [Fact]
+////            public void Reports_PixelOverflow_After_Arrange_Smaller_Than_Measure()
+////            {
+////                var target = new VirtualizingStackPanel();
+
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
+
+////                target.Measure(new Size(100, 100));
+////                target.Arrange(new Rect(0, 0, 50, 50));
+
+////                Assert.Equal(52, ((IVirtualizingPanel)target).PixelOverflow);
+////            }
+
+////            [Fact]
+////            public void Reports_PixelOverflow_With_PixelOffset()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var vp = (IVirtualizingPanel)target;
+
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
+////                vp.PixelOffset = 2;
+
+////                target.Measure(new Size(100, 100));
+////                target.Arrange(new Rect(target.DesiredSize));
+
+////                Assert.Equal(2, vp.PixelOverflow);
+////            }
+
+////            [Fact]
+////            public void PixelOffset_Can_Be_More_Than_Child_Without_Affecting_IsFull()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var vp = (IVirtualizingPanel)target;
+
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
+////                vp.PixelOffset = 55;
+
+////                target.Measure(new Size(100, 100));
+////                target.Arrange(new Rect(target.DesiredSize));
+
+////                Assert.Equal(55, vp.PixelOffset);
+////                Assert.Equal(2, vp.PixelOverflow);
+////                Assert.True(vp.IsFull);
+////            }
+
+////            [Fact]
+////            public void Passes_Navigation_Request_To_ILogicalScrollable_Parent()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var presenter = new TestPresenter { Child = target };
+////                var from = new Canvas();
+
+////                ((INavigableContainer)target).GetControl(NavigationDirection.Next, from, false);
+
+////                Assert.Equal(1, presenter.NavigationRequests.Count);
+////                Assert.Equal((NavigationDirection.Next, from), presenter.NavigationRequests[0]);
+////            }
+
+////            private class TestPresenter : Decorator, ILogicalScrollable
+////            {
+////                public bool CanHorizontallyScroll { get; set; }
+////                public bool CanVerticallyScroll { get; set; }
+////                public bool IsLogicalScrollEnabled => true;
+////                public Size ScrollSize { get; }
+////                public Size PageScrollSize { get; }
+////                public Size Extent { get; }
+////                public Vector Offset { get; set; }
+////                public Size Viewport { get; }
+
+////                public event EventHandler ScrollInvalidated;
+
+////                public List<(NavigationDirection, Control)> NavigationRequests { get; } = new();
+
+////                public bool BringIntoView(Control target, Rect targetRect)
+////                {
+////                    throw new NotImplementedException();
+////                }
+
+////                public Control GetControlInDirection(NavigationDirection direction, Control from)
+////                {
+////                    NavigationRequests.Add((direction, from));
+////                    return null;
+////                }
+
+////                public void RaiseScrollInvalidated(EventArgs e)
+////                {
+////                    throw new NotImplementedException();
+////                }
+////            }
+////        }
+////    }
+////}
diff --git a/tests/Avalonia.ReactiveUI.UnitTests/AutoDataTemplateBindingHookTest.cs b/tests/Avalonia.ReactiveUI.UnitTests/AutoDataTemplateBindingHookTest.cs
index 53bdff5dff7..c00303f4f88 100644
--- a/tests/Avalonia.ReactiveUI.UnitTests/AutoDataTemplateBindingHookTest.cs
+++ b/tests/Avalonia.ReactiveUI.UnitTests/AutoDataTemplateBindingHookTest.cs
@@ -139,7 +139,6 @@ private static FuncControlTemplate GetTemplate()
                 Child = new ItemsPresenter
                 {
                     Name = "PART_ItemsPresenter",
-                    [~ItemsPresenter.ItemsProperty] = parent[~ItemsControl.ItemsProperty],
                 }.RegisterInNameScope(scope)
             });
         }
diff --git a/tests/Avalonia.UnitTests/TestExtensions.cs b/tests/Avalonia.UnitTests/TestExtensions.cs
index 1bbf84e88d9..21a67a88007 100644
--- a/tests/Avalonia.UnitTests/TestExtensions.cs
+++ b/tests/Avalonia.UnitTests/TestExtensions.cs
@@ -9,6 +9,5 @@ namespace Avalonia.UnitTests
     public static class TestExtensions
     {
         public static void ApplyTemplate(this IContentPresenter presenter) => ((Layoutable)presenter).ApplyTemplate();
-        public static void ApplyTemplate(this IItemsPresenter presenter) => ((Layoutable)presenter).ApplyTemplate();
     }
 }

From c20e3c29e6965f6f6a6cf52aa08fc38f5de37ae0 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 25 Nov 2022 12:28:35 +0100
Subject: [PATCH 02/64] Initial (re)impl of VirtualizingStackPanel.

Currently only supports smooth scrolling.
---
 .../IVirtualizingController.cs                |  19 -
 src/Avalonia.Controls/IVirtualizingPanel.cs   |  11 -
 .../ItemVirtualizationMode.cs                 |   5 +
 src/Avalonia.Controls/ListBox.cs              |   2 +-
 .../Presenters/ItemsPresenter.cs              |  43 +-
 .../ItemsPresenterContainerGenerator.cs       |  10 +-
 .../Primitives/SelectingItemsControl.cs       |   2 +-
 .../Utils/CollectionUtils.cs                  |  49 ++
 src/Avalonia.Controls/VirtualizingPanel.cs    |  95 +++
 .../VirtualizingStackPanel.Smooth.cs          | 662 ++++++++++++++++++
 .../VirtualizingStackPanel.cs                 | 125 +++-
 .../VirtualizingStackPanelTests.cs            | 261 -------
 .../VirtualizingStackPanelTests_Smooth.cs     | 197 ++++++
 13 files changed, 1161 insertions(+), 320 deletions(-)
 delete mode 100644 src/Avalonia.Controls/IVirtualizingController.cs
 delete mode 100644 src/Avalonia.Controls/IVirtualizingPanel.cs
 create mode 100644 src/Avalonia.Controls/Utils/CollectionUtils.cs
 create mode 100644 src/Avalonia.Controls/VirtualizingPanel.cs
 create mode 100644 src/Avalonia.Controls/VirtualizingStackPanel.Smooth.cs
 delete mode 100644 tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
 create mode 100644 tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs

diff --git a/src/Avalonia.Controls/IVirtualizingController.cs b/src/Avalonia.Controls/IVirtualizingController.cs
deleted file mode 100644
index 7c87f8abbcb..00000000000
--- a/src/Avalonia.Controls/IVirtualizingController.cs
+++ /dev/null
@@ -1,19 +0,0 @@
-namespace Avalonia.Controls
-{
-    /// <summary>
-    /// Interface implemented by controls that act as controllers for an
-    /// <see cref="IVirtualizingPanel"/>.
-    /// </summary>
-    public interface IVirtualizingController
-    {
-        /// <summary>
-        /// Called when the <see cref="IVirtualizingPanel"/>'s controls should be updated.
-        /// </summary>
-        /// <remarks>
-        /// The controller should respond to this method being called by either adding
-        /// children up until <see cref="IVirtualizingPanel.IsFull"/> becomes true or
-        /// removing <see cref="IVirtualizingPanel.OverflowCount"/> controls.
-        /// </remarks>
-        void UpdateControls();
-    }
-}
diff --git a/src/Avalonia.Controls/IVirtualizingPanel.cs b/src/Avalonia.Controls/IVirtualizingPanel.cs
deleted file mode 100644
index eff469f37af..00000000000
--- a/src/Avalonia.Controls/IVirtualizingPanel.cs
+++ /dev/null
@@ -1,11 +0,0 @@
-using Avalonia.Layout;
-
-namespace Avalonia.Controls
-{
-    /// <summary>
-    /// A panel that can be used to virtualize items.
-    /// </summary>
-    public interface IVirtualizingPanel
-    {
-    }
-}
diff --git a/src/Avalonia.Controls/ItemVirtualizationMode.cs b/src/Avalonia.Controls/ItemVirtualizationMode.cs
index 1950bb7f204..66dd32d28cc 100644
--- a/src/Avalonia.Controls/ItemVirtualizationMode.cs
+++ b/src/Avalonia.Controls/ItemVirtualizationMode.cs
@@ -14,5 +14,10 @@ public enum ItemVirtualizationMode
         /// Virtualize items without smooth scrolling.
         /// </summary>
         Simple,
+
+        /// <summary>
+        /// Virtualize items with smooth scrolling.
+        /// </summary>
+        Smooth,
     }
 }
diff --git a/src/Avalonia.Controls/ListBox.cs b/src/Avalonia.Controls/ListBox.cs
index 0adc8a61ba9..cb9f2f42ef9 100644
--- a/src/Avalonia.Controls/ListBox.cs
+++ b/src/Avalonia.Controls/ListBox.cs
@@ -61,7 +61,7 @@ public class ListBox : SelectingItemsControl
         static ListBox()
         {
             ItemsPanelProperty.OverrideDefaultValue<ListBox>(DefaultPanel);
-            VirtualizationModeProperty.OverrideDefaultValue<ListBox>(ItemVirtualizationMode.Simple);
+            VirtualizationModeProperty.OverrideDefaultValue<ListBox>(ItemVirtualizationMode.Smooth);
         }
 
         /// <summary>
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
index 2a52e00d670..b731f48d9c7 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
@@ -1,6 +1,3 @@
-using System;
-using System.Collections;
-using System.Collections.Specialized;
 using System.Diagnostics;
 
 namespace Avalonia.Controls.Presenters
@@ -39,46 +36,62 @@ public ITemplate<Panel> ItemsPanel
 
         public override sealed void ApplyTemplate()
         {
-            if (Panel is null)
+            if (Panel is null && ItemsControl is not null)
             {
                 Panel = ItemsPanel.Build();
                 Panel.SetValue(TemplatedParentProperty, TemplatedParent);
                 LogicalChildren.Add(Panel);
                 VisualChildren.Add(Panel);
-                CreateGeneratorIfSimplePanel();
+
+                if (Panel is VirtualizingPanel v)
+                    v.Attach(ItemsControl);
+                else
+                    CreateSimplePanelGenerator();
             }
         }
 
+        internal void ScrollIntoView(int index)
+        {
+
+        }
+
         protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
         {
             base.OnPropertyChanged(change);
 
             if (change.Property == TemplatedParentProperty)
             {
-                _generator?.Dispose();
-                _generator = null;
+                ResetState();
+                ItemsControl = null;
 
                 if (change.NewValue is ItemsControl itemsControl)
                 {
                     ItemsControl = itemsControl;
                     ((IItemsPresenterHost)itemsControl)?.RegisterItemsPresenter(this);
-                    CreateGeneratorIfSimplePanel();
                 }
             }
             else if (change.Property == ItemsPanelProperty)
             {
-                _generator?.Dispose();
-                _generator = null;
-                LogicalChildren.Clear();
-                VisualChildren.Clear();
-                Panel = null;
+                ResetState();
                 InvalidateMeasure();
             }
         }
 
-        private void CreateGeneratorIfSimplePanel()
+        private void ResetState()
         {
-            if (ItemsControl is null || Panel is null || Panel is IVirtualizingPanel)
+            _generator?.Dispose();
+            _generator = null;
+            LogicalChildren.Clear();
+            VisualChildren.Clear();
+            (Panel as VirtualizingPanel)?.Detach();
+            Panel = null;
+        }
+
+        private void CreateSimplePanelGenerator()
+        {
+            Debug.Assert(Panel is not VirtualizingPanel);
+
+            if (ItemsControl is null || Panel is null)
                 return;
 
             _generator?.Dispose();
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs b/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs
index 4c2bd35f5a7..233635a414e 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs
@@ -2,6 +2,7 @@
 using System.Collections;
 using System.Collections.Specialized;
 using System.Diagnostics;
+using Avalonia.Controls.Utils;
 
 namespace Avalonia.Controls.Presenters
 {
@@ -10,13 +11,12 @@ namespace Avalonia.Controls.Presenters
     /// </summary>
     internal class ItemsPresenterContainerGenerator : IDisposable
     {
-        private static NotifyCollectionChangedEventArgs s_Reset = new(NotifyCollectionChangedAction.Reset);
-        private ItemsPresenter _presenter;
+        private readonly ItemsPresenter _presenter;
 
         public ItemsPresenterContainerGenerator(ItemsPresenter presenter)
         {
             Debug.Assert(presenter.ItemsControl is not null);
-            Debug.Assert(presenter.Panel is not null or IVirtualizingPanel);
+            Debug.Assert(presenter.Panel is not null or VirtualizingPanel);
             
             _presenter = presenter;
             _presenter.ItemsControl.PropertyChanged += OnItemsControlPropertyChanged;
@@ -24,7 +24,7 @@ public ItemsPresenterContainerGenerator(ItemsPresenter presenter)
             if (_presenter.ItemsControl.Items is INotifyCollectionChanged incc)
                 incc.CollectionChanged += OnItemsChanged;
 
-            OnItemsChanged(null, s_Reset);
+            OnItemsChanged(null, CollectionUtils.ResetEventArgs);
         }
 
         public void Dispose()
@@ -43,7 +43,7 @@ private void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChang
             {
                 if (e.OldValue is INotifyCollectionChanged inccOld)
                     inccOld.CollectionChanged -= OnItemsChanged;
-                OnItemsChanged(null, s_Reset);
+                OnItemsChanged(null, CollectionUtils.ResetEventArgs);
                 if (e.NewValue is INotifyCollectionChanged inccNew)
                     inccNew.CollectionChanged += OnItemsChanged;
             }
diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index 7f8d8f098ab..44fa78ac211 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -373,7 +373,7 @@ public override void EndInit()
         /// Scrolls the specified item into view.
         /// </summary>
         /// <param name="index">The index of the item.</param>
-        public void ScrollIntoView(int index) => throw new NotImplementedException(); ////Presenter?.ScrollIntoView(index);
+        public void ScrollIntoView(int index) => Presenter?.ScrollIntoView(index);
 
         /// <summary>
         /// Scrolls the specified item into view.
diff --git a/src/Avalonia.Controls/Utils/CollectionUtils.cs b/src/Avalonia.Controls/Utils/CollectionUtils.cs
new file mode 100644
index 00000000000..8db5564557d
--- /dev/null
+++ b/src/Avalonia.Controls/Utils/CollectionUtils.cs
@@ -0,0 +1,49 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Specialized;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Avalonia.Controls.Utils
+{
+    internal static class CollectionUtils
+    {
+        public static NotifyCollectionChangedEventArgs ResetEventArgs { get; } = new(NotifyCollectionChangedAction.Reset);
+
+        public static void InsertMany<T>(this List<T> list, int index, T item, int count)
+        {
+            var repeat = FastRepeat<T>.Instance;
+            repeat.Count = count;
+            repeat.Item = item;
+            list.InsertRange(index, FastRepeat<T>.Instance);
+            repeat.Item = default;
+        }
+
+        private class FastRepeat<T> : ICollection<T>
+        {
+            public static readonly FastRepeat<T> Instance = new();
+            public int Count { get; set; }
+            public bool IsReadOnly => true;
+            [AllowNull] public T Item { get; set; }
+            public void Add(T item) => throw new NotImplementedException();
+            public void Clear() => throw new NotImplementedException();
+            public bool Contains(T item) => throw new NotImplementedException();
+            public bool Remove(T item) => throw new NotImplementedException();
+            IEnumerator IEnumerable.GetEnumerator() => throw new NotImplementedException();
+            public IEnumerator<T> GetEnumerator() => throw new NotImplementedException();
+
+            public void CopyTo(T[] array, int arrayIndex)
+            {
+                var end = arrayIndex + Count;
+
+                for (var i = arrayIndex; i < end; ++i)
+                {
+                    array[i] = Item;
+                }
+            }
+        }
+    }
+}
diff --git a/src/Avalonia.Controls/VirtualizingPanel.cs b/src/Avalonia.Controls/VirtualizingPanel.cs
new file mode 100644
index 00000000000..19b1c4002cd
--- /dev/null
+++ b/src/Avalonia.Controls/VirtualizingPanel.cs
@@ -0,0 +1,95 @@
+using System.Collections;
+using System.Collections.Specialized;
+using Avalonia.Controls.Utils;
+
+namespace Avalonia.Controls
+{
+    /// <summary>
+    /// Base class for panels that can be used to virtualize items.
+    /// </summary>
+    public abstract class VirtualizingPanel : Panel
+    {
+        private ItemsControl? _itemsControl;
+
+        protected ItemsControl? ItemsControl 
+        {
+            get => _itemsControl;
+            private set
+            {
+                if (_itemsControl != value)
+                {
+                    var oldValue = _itemsControl;
+                    _itemsControl= value;
+                    OnItemsControlChanged(oldValue);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Called when the <see cref="ItemsControl"/> that owns the panel changes.
+        /// </summary>
+        /// <param name="oldValue">
+        /// The old value of the <see cref="ItemsControl"/> property.
+        /// </param>
+        protected virtual void OnItemsControlChanged(ItemsControl? oldValue)
+        {
+        }
+
+        /// <summary>
+        /// Called when the <see cref="ItemsControl.Items"/> collection of the owner
+        /// <see cref="ItemsControl"/> changes.
+        /// </summary>
+        /// <param name="items">The items.</param>
+        /// <param name="e">The event args.</param>
+        /// <remarks>
+        /// This method is called a <see cref="INotifyCollectionChanged"/> event is raised by
+        /// the items, or when the <see cref="ItemsControl.Items"/> property is assigned a
+        /// new collection, in which case the <see cref="NotifyCollectionChangedAction"/> will
+        /// be <see cref="NotifyCollectionChangedAction.Reset"/>.
+        /// </remarks>
+        protected virtual void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
+        {
+        }
+
+        internal void Attach(ItemsControl itemsControl)
+        {
+            ItemsControl = itemsControl;
+            ItemsControl.PropertyChanged += OnItemsControlPropertyChanged;
+
+            if (ItemsControl.Items is INotifyCollectionChanged incc)
+                incc.CollectionChanged += OnItemsControlItemsChanged;
+        }
+
+        internal void Detach()
+        {
+            if (ItemsControl is null)
+                return;
+
+            ItemsControl.PropertyChanged -= OnItemsControlPropertyChanged;
+
+            if (ItemsControl.Items is INotifyCollectionChanged incc)
+                incc.CollectionChanged -= OnItemsControlItemsChanged;
+
+            ItemsControl = null;
+            Children.Clear();
+        }
+
+        private protected virtual void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+        {
+            if (e.Property == ItemsControl.ItemsProperty)
+            {
+                if (e.OldValue is INotifyCollectionChanged inccOld)
+                    inccOld.CollectionChanged -= OnItemsControlItemsChanged;
+                OnItemsControlItemsChanged(null, CollectionUtils.ResetEventArgs);
+                if (e.NewValue is INotifyCollectionChanged inccNew)
+                    inccNew.CollectionChanged += OnItemsControlItemsChanged;
+            }
+        }
+
+        private void OnItemsControlItemsChanged(object? sender, NotifyCollectionChangedEventArgs e)
+        {
+            if (_itemsControl?.Items is IList items)
+                OnItemsChanged(items, e);
+        }
+    }
+}
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.Smooth.cs b/src/Avalonia.Controls/VirtualizingStackPanel.Smooth.cs
new file mode 100644
index 00000000000..1f6d8319fb3
--- /dev/null
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.Smooth.cs
@@ -0,0 +1,662 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Specialized;
+using System.Diagnostics;
+using Avalonia.Controls.Utils;
+using Avalonia.Layout;
+using Avalonia.Utilities;
+using Avalonia.VisualTree;
+
+namespace Avalonia.Controls
+{
+    public partial class VirtualizingStackPanel : VirtualizingPanel
+    {
+        private static readonly Rect s_invalidViewport = new(double.PositiveInfinity, double.PositiveInfinity, 0, 0);
+        private readonly Action<Control> _recycleElement;
+        private readonly Action<Control, int> _updateElementIndex;
+        private int _anchorIndex = -1;
+        private Control? _anchorElement;
+        private bool _isWaitingForViewportUpdate;
+        private double _lastEstimatedElementSizeU = 25;
+        private RealizedElementList? _measureElements;
+        private RealizedElementList? _realizedElements;
+        private Rect _viewport = s_invalidViewport;
+
+        private Size MeasureOverrideSmooth(Size availableSize)
+        {
+            if (!IsEffectivelyVisible)
+                return default;
+
+            var items = ItemsControl?.Items as IList;
+
+            if (items is null || items.Count == 0)
+            {
+                Children.Clear();
+                return default;
+            }
+
+            var orientation = Orientation;
+
+            _realizedElements ??= new();
+            _measureElements ??= new();
+
+            // If we're bringing an item into view, ignore any layout passes until we receive a new
+            // effective viewport.
+            if (_isWaitingForViewportUpdate)
+            {
+                var sizeV = orientation == Orientation.Horizontal ? DesiredSize.Height : DesiredSize.Width;
+                return CalculateDesiredSize(orientation, items, sizeV);
+            }
+
+            // We handle horizontal and vertical layouts here so X and Y are abstracted to:
+            // - Horizontal layouts: U = horizontal, V = vertical
+            // - Vertical layouts: U = vertical, V = horizontal
+            var viewport = CalculateMeasureViewport(items);
+
+            // Recycle elements outside of the expected range.
+            _realizedElements.RecycleElementsBefore(viewport.firstIndex, _recycleElement);
+            _realizedElements.RecycleElementsAfter(viewport.estimatedLastIndex, _recycleElement);
+
+            // Do the measure, creating/recycling elements as necessary to fill the viewport. Don't
+            // write to _realizedElements yet, only _measureElements.
+            GenerateElements(availableSize, ref viewport);
+
+            // Now we know what definitely fits, recycle anything left over.
+            _realizedElements.RecycleElementsAfter(_measureElements.LastModelIndex, _recycleElement);
+
+            // And swap the measureElements and realizedElements collection.
+            (_measureElements, _realizedElements) = (_realizedElements, _measureElements);
+            _measureElements.ResetForReuse();
+
+            return CalculateDesiredSize(orientation, items, viewport.measuredV);
+        }
+
+        private Size ArrangeOverrideSmooth(Size finalSize)
+        {
+            Debug.Assert(_realizedElements is not null);
+
+            var orientation = Orientation;
+            var u = _realizedElements!.StartU;
+
+            for (var i = 0; i < _realizedElements.Count; ++i)
+            {
+                var e = _realizedElements.Elements[i];
+
+                if (e is object)
+                {
+                    var sizeU = _realizedElements.SizeU[i];
+                    var rect = orientation == Orientation.Horizontal ?
+                        new Rect(u, 0, sizeU, finalSize.Height) :
+                        new Rect(0, u, finalSize.Width, sizeU);
+                    e.Arrange(rect);
+                    u += orientation == Orientation.Horizontal ? rect.Width : rect.Height;
+                }
+            }
+
+            return finalSize;
+        }
+
+        private MeasureViewport CalculateMeasureViewport(IList items)
+        {
+            Debug.Assert(_realizedElements is not null);
+
+            // If the control has not yet been laid out then the effective viewport won't have been set.
+            // Try to work it out from an ancestor control.
+            var viewport = _viewport != s_invalidViewport ? _viewport : EstimateViewport();
+
+            // Get the viewport in the orientation direction.
+            var viewportStart = Orientation == Orientation.Horizontal ? viewport.X : viewport.Y;
+            var viewportEnd = Orientation == Orientation.Horizontal ? viewport.Right : viewport.Bottom;
+
+            var (firstIndex, firstIndexU) = _realizedElements!.GetElementAt(viewportStart);
+            var (lastIndex, _) = _realizedElements.GetElementAt(viewportEnd);
+            var estimatedElementSize = -1.0;
+            var itemCount = items?.Count ?? 0;
+
+            if (firstIndex == -1)
+            {
+                estimatedElementSize = EstimateElementSizeU();
+                firstIndex = (int)(viewportStart / estimatedElementSize);
+                firstIndexU = firstIndex * estimatedElementSize;
+            }
+
+            if (lastIndex == -1)
+            {
+                if (estimatedElementSize == -1)
+                    estimatedElementSize = EstimateElementSizeU();
+                lastIndex = (int)(viewportEnd / estimatedElementSize);
+            }
+
+            return new MeasureViewport
+            {
+                firstIndex = MathUtilities.Clamp(firstIndex, 0, itemCount - 1),
+                estimatedLastIndex = MathUtilities.Clamp(lastIndex, 0, itemCount - 1),
+                viewportUStart = viewportStart,
+                viewportUEnd = viewportEnd,
+                startU = firstIndexU,
+            };
+        }
+
+        private Size CalculateDesiredSize(Orientation orientation, IList items, double sizeV)
+        {
+            var sizeU = EstimateElementSizeU() * items.Count;
+
+            if (double.IsInfinity(sizeU) || double.IsNaN(sizeU))
+                throw new InvalidOperationException("Invalid calculated size.");
+
+            return orientation == Orientation.Horizontal ?
+                new Size(sizeU, sizeV) :
+                new Size(sizeV, sizeU);
+        }
+
+        private double EstimateElementSizeU()
+        {
+            var count = _realizedElements!.Count;
+            var divisor = 0.0;
+            var total = 0.0;
+
+            for (var i = 0; i < count; ++i)
+            {
+                if (_realizedElements.Elements[i] is object)
+                {
+                    total += _realizedElements.SizeU[i];
+                    ++divisor;
+                }
+            }
+
+            if (divisor == 0 || total == 0)
+                return _lastEstimatedElementSizeU;
+
+            _lastEstimatedElementSizeU = total / divisor;
+            return _lastEstimatedElementSizeU;
+        }
+
+        private Rect EstimateViewport()
+        {
+            var c = this.GetVisualParent();
+            var viewport = new Rect();
+
+            if (c is null)
+            {
+                return viewport;
+            }
+
+            while (c is not null)
+            {
+                if (!c.Bounds.IsEmpty && c.TransformToVisual(this) is Matrix transform)
+                {
+                    viewport = new Rect(0, 0, c.Bounds.Width, c.Bounds.Height)
+                        .TransformToAABB(transform);
+                    break;
+                }
+
+                c = c?.GetVisualParent();
+            }
+
+
+            return viewport;
+        }
+
+        private void GenerateElements(Size availableSize, ref MeasureViewport viewport)
+        {
+            Debug.Assert(ItemsControl?.Items is IList);
+            Debug.Assert(_measureElements is not null);
+
+            var items = (IList)ItemsControl!.Items;
+            var horizontal = Orientation == Orientation.Horizontal;
+            var index = viewport.firstIndex;
+            var u = viewport.startU;
+
+            do
+            {
+                var e = GetOrCreateElement(items, index);
+                e.Measure(availableSize);
+
+                var sizeU = horizontal ? e.DesiredSize.Width : e.DesiredSize.Height;
+                var sizeV = horizontal ? e.DesiredSize.Height : e.DesiredSize.Width;
+
+                _measureElements!.Add(index, e, u, sizeU);
+                viewport.measuredV = Math.Max(viewport.measuredV, sizeV);
+
+                u += sizeU;
+                ++index;
+            } while (u < viewport.viewportUEnd && index < items.Count);
+        }
+
+        private Control GetOrCreateElement(IList items, int index)
+        {
+            var e = GetRealizedElement(index) ?? GetRecycledOrCreateElement(items, index);
+            InvalidateHack(e);
+            return e;
+        }
+
+        private Control? GetRealizedElement(int index)
+        {
+            Debug.Assert(_realizedElements is not null);
+
+            if (_anchorIndex == index)
+                return _anchorElement;
+            return _realizedElements!.GetElement(index);
+        }
+
+        private Control GetRecycledOrCreateElement(IList items, int index)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            var c = ItemsControl!.ItemContainerGenerator.Materialize(index, items[index]!).ContainerControl;
+            Children.Add(c);
+            return c;
+        }
+
+        private void RecycleElement(Control element)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            var index = ItemsControl.ItemContainerGenerator!.IndexFromContainer(element);
+            ItemsControl!.ItemContainerGenerator.Dematerialize(index, 1);
+            Children.Remove(element);
+        }
+
+        private void UpdateElementIndex(Control element, int index)
+        {
+            // TODO: Implement this after we refactor ItemContainerGenerator.
+        }
+
+        private void OnEffectiveViewportChanged(object? sender, EffectiveViewportChangedEventArgs e)
+        {
+            _viewport = e.EffectiveViewport;
+            _isWaitingForViewportUpdate = false;
+            InvalidateMeasure();
+        }
+
+        private void OnItemsChangedSmooth(NotifyCollectionChangedEventArgs e)
+        {
+            if (_realizedElements is null)
+                return;
+
+            switch (e.Action)
+            {
+                case NotifyCollectionChangedAction.Add:
+                    _realizedElements.ItemsInserted(e.NewStartingIndex, e.NewItems!.Count, _updateElementIndex);
+                    ItemsControl!.ItemContainerGenerator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
+                    break;
+                case NotifyCollectionChangedAction.Remove:
+                    _realizedElements.ItemsRemoved(e.OldStartingIndex, e.OldItems!.Count, _updateElementIndex, _recycleElement);
+                    ItemsControl!.ItemContainerGenerator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
+                    break;
+                case NotifyCollectionChangedAction.Reset:
+                    ////RecycleAllElements();
+                    break;
+            }
+
+            InvalidateMeasure();
+        }
+
+        private static void InvalidateHack(Control c)
+        {
+            bool HasInvalidations(Control c)
+            {
+                if (!c.IsMeasureValid)
+                    return true;
+
+                for (var i = 0; i < c.VisualChildren.Count; ++i)
+                {
+                    if (c.VisualChildren[i] is Control child)
+                    {
+                        if (!child.IsMeasureValid || HasInvalidations(child))
+                            return true;
+                    }
+                }
+
+                return false;
+            }
+
+            void Invalidate(Control c)
+            {
+                c.InvalidateMeasure();
+                for (var i = 0; i < c.VisualChildren.Count; ++i)
+                {
+                    if (c.VisualChildren[i] is Control child)
+                        Invalidate(child);
+                }
+            }
+
+            if (HasInvalidations(c))
+                Invalidate(c);
+        }
+
+        /// <summary>
+        /// Stores the realized element state for a <see cref="VirtualizingStackPanel"/> in smooth mode.
+        /// </summary>
+        internal class RealizedElementList
+        {
+            private int _firstIndex;
+            private List<Control?>? _elements;
+            private List<double>? _sizes;
+            private double _startU;
+
+            /// <summary>
+            /// Gets the number of realized elements.
+            /// </summary>
+            public int Count => _elements?.Count ?? 0;
+
+            /// <summary>
+            /// Gets the model index of the first realized element, or -1 if no elements are realized.
+            /// </summary>
+            public int FirstModelIndex => _elements?.Count > 0 ? _firstIndex : -1;
+
+            /// <summary>
+            /// Gets the model index of the last realized element, or -1 if no elements are realized.
+            /// </summary>
+            public int LastModelIndex => _elements?.Count > 0 ? _firstIndex + _elements.Count - 1 : -1;
+
+            /// <summary>
+            /// Gets the elements.
+            /// </summary>
+            public IReadOnlyList<Control?> Elements => _elements ??= new List<Control?>();
+
+            /// <summary>
+            /// Gets the sizes of the elements on the primary axis.
+            /// </summary>
+            public IReadOnlyList<double> SizeU => _sizes ??= new List<double>();
+
+            /// <summary>
+            /// Gets the position of the first element on the primary axis.
+            /// </summary>
+            public double StartU => _startU;
+
+            /// <summary>
+            /// Adds a newly realized element to the collection.
+            /// </summary>
+            /// <param name="modelIndex">The model index of the element.</param>
+            /// <param name="element">The element.</param>
+            /// <param name="u">The position of the elemnt on the primary axis.</param>
+            /// <param name="sizeU">The size of the element on the primary axis.</param>
+            public void Add(int modelIndex, Control element, double u, double sizeU)
+            {
+                if (modelIndex < 0)
+                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+
+                _elements ??= new List<Control?>();
+                _sizes ??= new List<double>();
+
+                if (Count == 0)
+                {
+                    _elements.Add(element);
+                    _sizes.Add(sizeU);
+                    _startU = u;
+                    _firstIndex = modelIndex;
+                }
+                else if (modelIndex == LastModelIndex + 1)
+                {
+                    _elements.Add(element);
+                    _sizes.Add(sizeU);
+                }
+                else if (modelIndex == FirstModelIndex - 1)
+                {
+                    --_firstIndex;
+                    _elements.Insert(0, element);
+                    _sizes.Insert(0, sizeU);
+                    _startU = u;
+                }
+                else
+                {
+                    throw new NotSupportedException("Can only add items to the beginning or end of realized elements.");
+                }
+            }
+
+            /// <summary>
+            /// Gets the element at the specified model index, if realized.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of the element to get.</param>
+            /// <returns>The element if realized; otherwise null.</returns>
+            public Control? GetElement(int modelIndex)
+            {
+                var index = modelIndex - FirstModelIndex;
+                if (index >= 0 && index < _elements?.Count)
+                    return _elements[index];
+                return null;
+            }
+
+            /// <summary>
+            /// Gets the element at the specified position on the primary axis, if realized.
+            /// </summary>
+            /// <param name="position">The position.</param>
+            /// <returns>
+            /// A tuple containing the index of the element (or -1 if not found) and the position of the element on the
+            /// primary axis.
+            /// </returns>
+            public (int index, double position) GetElementAt(double position)
+            {
+                if (_sizes is null || position < StartU)
+                    return (-1, 0);
+
+                var u = StartU;
+                var i = FirstModelIndex;
+
+                foreach (var size in _sizes)
+                {
+                    var endU = u + size;
+                    if (position < endU)
+                        return (i, u);
+                    u += size;
+                    ++i;
+                }
+
+                return (-1, 0);
+            }
+
+            /// <summary>
+            /// Updates the elements in response to items being inserted into the source collection.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of the insert.</param>
+            /// <param name="count">The number of items inserted.</param>
+            /// <param name="updateElementIndex">A method used to update the element indexes.</param>
+            public void ItemsInserted(int modelIndex, int count, Action<Control, int> updateElementIndex)
+            {
+                if (modelIndex < 0)
+                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+                if (_elements is null || _elements.Count == 0)
+                    return;
+
+                // Get the index within the realized _elements collection.
+                var first = FirstModelIndex;
+                var index = modelIndex - first;
+
+                if (index < Count)
+                {
+                    // The insertion point affects the realized elements. Update the index of the
+                    // elements after the insertion point.
+                    var elementCount = _elements.Count;
+                    var start = Math.Max(index, 0);
+
+                    for (var i = start; i < elementCount; ++i)
+                    {
+                        if (_elements[i] is Control element)
+                            updateElementIndex(element, first + i + count);
+                    }
+
+                    if (index <= 0)
+                    {
+                        // The insertion point was before the first element, update the first index.
+                        _firstIndex += count;
+                    }
+                    else
+                    {
+                        // The insertion point was within the realized elements, insert an empty space
+                        // in _elements and _sizes.
+                        _elements!.InsertMany(index, null, count);
+                        _sizes!.InsertMany(index, 0.0, count);
+                    }
+                }
+            }
+
+            /// <summary>
+            /// Updates the elements in response to items being removed from the source collection.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of the remove.</param>
+            /// <param name="count">The number of items removed.</param>
+            /// <param name="updateElementIndex">A method used to update the element indexes.</param>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void ItemsRemoved(
+                int modelIndex,
+                int count,
+                Action<Control, int> updateElementIndex,
+                Action<Control> recycleElement)
+            {
+                if (modelIndex < 0)
+                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+                if (_elements is null || _elements.Count == 0)
+                    return;
+
+                // Get the removal start and end index within the realized _elements collection.
+                var first = FirstModelIndex;
+                var last = LastModelIndex;
+                var startIndex = modelIndex - first;
+                var endIndex = (modelIndex + count) - first;
+
+                if (endIndex < 0)
+                {
+                    // The removed range was before the realized elements. Update the first index and
+                    // the indexes of the realized elements.
+                    _firstIndex -= count;
+
+                    for (var i = 0; i < _elements.Count; ++i)
+                    {
+                        if (_elements[i] is Control element)
+                            updateElementIndex(element, _firstIndex + i);
+                    }
+                }
+                else if (startIndex < _elements.Count)
+                {
+                    // Recycle and remove the affected elements.
+                    var start = Math.Max(startIndex, 0);
+                    var end = Math.Min(endIndex, _elements.Count);
+
+                    for (var i = start; i < end; ++i)
+                    {
+                        if (_elements[i] is Control element)
+                            recycleElement(element);
+                    }
+
+                    _elements.RemoveRange(start, end - start);
+                    _sizes!.RemoveRange(start, end - start);
+
+                    // If the remove started before and ended within our realized elements, then our new
+                    // first index will be the index where the remove started.
+                    if (startIndex <= 0 && end < last)
+                        _firstIndex = first = modelIndex;
+
+                    // Update the indexes of the elements after the removed range.
+                    end = _elements.Count;
+                    for (var i = start; i < end; ++i)
+                    {
+                        if (_elements[i] is Control element)
+                            updateElementIndex(element, first + i);
+                    }
+                }
+            }
+
+            /// <summary>
+            /// Recycles elements before a specific index.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of new first element.</param>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void RecycleElementsBefore(int modelIndex, Action<Control> recycleElement)
+            {
+                if (modelIndex <= FirstModelIndex || _elements is null || _elements.Count == 0)
+                    return;
+
+                if (modelIndex > LastModelIndex)
+                {
+                    RecycleAllElements(recycleElement);
+                }
+                else
+                {
+                    var endIndex = modelIndex - FirstModelIndex;
+
+                    for (var i = 0; i < endIndex; ++i)
+                    {
+                        if (_elements[i] is Control e)
+                            recycleElement(e);
+                    }
+
+                    _elements.RemoveRange(0, endIndex);
+                    _sizes!.RemoveRange(0, endIndex);
+                    _firstIndex = modelIndex;
+                }
+            }
+
+            /// <summary>
+            /// Recycles elements after a specific index.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of new last element.</param>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void RecycleElementsAfter(int modelIndex, Action<Control> recycleElement)
+            {
+                if (modelIndex >= LastModelIndex || _elements is null || _elements.Count == 0)
+                    return;
+
+                if (modelIndex < FirstModelIndex)
+                {
+                    RecycleAllElements(recycleElement);
+                }
+                else
+                {
+                    var startIndex = (modelIndex + 1) - FirstModelIndex;
+                    var count = _elements.Count;
+
+                    for (var i = startIndex; i < count; ++i)
+                    {
+                        if (_elements[i] is Control e)
+                            recycleElement(e);
+                    }
+
+                    _elements.RemoveRange(startIndex, _elements.Count - startIndex);
+                    _sizes!.RemoveRange(startIndex, _sizes.Count - startIndex);
+                }
+            }
+
+            /// <summary>
+            /// Recycles all realized elements.
+            /// </summary>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void RecycleAllElements(Action<Control> recycleElement)
+            {
+                if (_elements is null || _elements.Count == 0)
+                    return;
+
+                foreach (var e in _elements)
+                {
+                    if (e is object)
+                        recycleElement(e);
+                }
+
+                _startU = _firstIndex = 0;
+                _elements?.Clear();
+                _sizes?.Clear();
+            }
+
+            /// <summary>
+            /// Resets the element list and prepares it for reuse.
+            /// </summary>
+            public void ResetForReuse()
+            {
+                _startU = _firstIndex = 0;
+                _elements?.Clear();
+                _sizes?.Clear();
+            }
+        }
+
+        private struct MeasureViewport
+        {
+            public int firstIndex;
+            public int estimatedLastIndex;
+            public double viewportUStart;
+            public double viewportUEnd;
+            public double measuredV;
+            public double startU;
+        }
+    }
+}
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index ea94440bf16..78839c44b87 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -1,20 +1,131 @@
 using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Specialized;
+using Avalonia.Layout;
 
 namespace Avalonia.Controls
 {
-    public class VirtualizingStackPanel : StackPanel
+    public partial class VirtualizingStackPanel : VirtualizingPanel
     {
         /// <summary>
-        /// Defines the <see cref="VirtualizationMode"/> property.
+        /// Defines the <see cref="Orientation"/> property.
         /// </summary>
-        public static readonly StyledProperty<ItemVirtualizationMode> VirtualizationModeProperty =
-            AvaloniaProperty.Register<VirtualizingStackPanel, ItemVirtualizationMode>(
-                nameof(VirtualizationMode));
+        public static readonly StyledProperty<Orientation> OrientationProperty =
+            StackLayout.OrientationProperty.AddOwner<VirtualizingStackPanel>();
 
+        /// <summary>
+        /// Defines the VirtualizationMode attached property.
+        /// </summary>
+        public static readonly AttachedProperty<ItemVirtualizationMode> VirtualizationModeProperty =
+            AvaloniaProperty.RegisterAttached<VirtualizingStackPanel, Control, ItemVirtualizationMode>(
+                "VirtualizationMode", ItemVirtualizationMode.None);
+
+        private ItemVirtualizationMode _virtualizationMode;
+
+        public VirtualizingStackPanel()
+        {
+            _recycleElement = RecycleElement;
+            _updateElementIndex = UpdateElementIndex;
+        }
+
+        /// <summary>
+        /// Gets or sets the axis along which items are laid out.
+        /// </summary>
+        /// <value>
+        /// One of the enumeration values that specifies the axis along which items are laid out.
+        /// The default is Vertical.
+        /// </value>
+        public Orientation Orientation
+        {
+            get => GetValue(OrientationProperty);
+            set => SetValue(OrientationProperty, value);
+        }
+
+        /// <summary>
+        /// Gets the current <see cref="ItemVirtualizationMode"/> in use for the panel.
+        /// </summary>
         public ItemVirtualizationMode VirtualizationMode
         {
-            get => GetValue(VirtualizationModeProperty);
-            set => SetValue(VirtualizationModeProperty, value);
+            get => _virtualizationMode;
+            set
+            {
+                if (_virtualizationMode != value)
+                {
+                    if (_virtualizationMode == ItemVirtualizationMode.Smooth)
+                        EffectiveViewportChanged -= OnEffectiveViewportChanged;
+
+                    _virtualizationMode = value;
+
+                    if (_virtualizationMode == ItemVirtualizationMode.Smooth)
+                        EffectiveViewportChanged += OnEffectiveViewportChanged;
+
+                    Children.Clear();
+                }
+            }
+        }
+
+        public static ItemVirtualizationMode GetVirtualizationMode(Control c)
+        {
+            return c.GetValue(VirtualizationModeProperty);
+        }
+
+        public static void SetVirtualizationMode(Control c, ItemVirtualizationMode value)
+        {
+            c.SetValue(VirtualizationModeProperty, value);
+        }
+
+        protected override Size MeasureOverride(Size availableSize)
+        {
+            return VirtualizationMode switch
+            {
+                ItemVirtualizationMode.Smooth => MeasureOverrideSmooth(availableSize),
+                _ => throw new NotImplementedException()
+            };
+        }
+
+        protected override Size ArrangeOverride(Size finalSize)
+        {
+            return VirtualizationMode switch
+            {
+                ItemVirtualizationMode.Smooth => ArrangeOverrideSmooth(finalSize),
+                _ => throw new NotImplementedException()
+            };
+        }
+
+        protected override void OnItemsControlChanged(ItemsControl? oldValue)
+        {
+            base.OnItemsControlChanged(oldValue);
+            VirtualizationMode = ItemsControl is null ? ItemVirtualizationMode.None : GetVirtualizationMode(ItemsControl);
+        }
+
+        protected override void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
+        {
+            switch (VirtualizationMode)
+            {
+                case ItemVirtualizationMode.Smooth:
+                    OnItemsChangedSmooth(e);
+                    break;
+            }
+        }
+
+        internal IReadOnlyList<Control?> GetRealizedElements()
+        {
+            return VirtualizationMode switch
+            {
+                ItemVirtualizationMode.Smooth => _realizedElements?.Elements ?? Array.Empty<Control>(),
+                _ => Children,
+            };
+        }
+
+        private protected override void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+        {
+            base.OnItemsControlPropertyChanged(sender, e);
+
+            if (e.Property == VirtualizationModeProperty)
+            {
+                VirtualizationMode = e.GetNewValue<ItemVirtualizationMode>();
+            }
         }
     }
 }
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
deleted file mode 100644
index 6270d698e7b..00000000000
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
+++ /dev/null
@@ -1,261 +0,0 @@
-////using System;
-////using System.Collections.Generic;
-////using Avalonia.Controls.Primitives;
-////using Avalonia.Input;
-////using Avalonia.LogicalTree;
-////using Moq;
-////using Xunit;
-
-////namespace Avalonia.Controls.UnitTests
-////{
-////    public class VirtualizingStackPanelTests
-////    {
-////        public class Vertical
-////        {
-////            [Fact]
-////            public void Measure_Invokes_Controller_UpdateControls()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var controller = new Mock<IVirtualizingController>();
-
-////                ((IVirtualizingPanel)target).Controller = controller.Object;
-////                target.Measure(new Size(100, 100));
-
-////                controller.Verify(x => x.UpdateControls(), Times.Once());
-////            }
-
-////            [Fact]
-////            public void Measure_Invokes_Controller_UpdateControls_If_AvailableSize_Changes()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var controller = new Mock<IVirtualizingController>();
-
-////                ((IVirtualizingPanel)target).Controller = controller.Object;
-////                target.Measure(new Size(100, 100));
-////                target.InvalidateMeasure();
-////                target.Measure(new Size(100, 100));
-////                target.InvalidateMeasure();
-////                target.Measure(new Size(100, 101));
-
-////                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
-////            }
-
-////            [Fact]
-////            public void Measure_Does_Not_Invoke_Controller_UpdateControls_If_AvailableSize_Is_The_Same()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var controller = new Mock<IVirtualizingController>();
-
-////                ((IVirtualizingPanel)target).Controller = controller.Object;
-////                target.Measure(new Size(100, 100));
-////                target.InvalidateMeasure();
-////                target.Measure(new Size(100, 100));
-
-////                controller.Verify(x => x.UpdateControls(), Times.Once());
-////            }
-
-////            [Fact]
-////            public void Measure_Invokes_Controller_UpdateControls_If_AvailableSize_Is_The_Same_After_ForceInvalidateMeasure()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var controller = new Mock<IVirtualizingController>();
-
-////                ((IVirtualizingPanel)target).Controller = controller.Object;
-////                target.Measure(new Size(100, 100));
-////                ((IVirtualizingPanel)target).ForceInvalidateMeasure();
-////                target.Measure(new Size(100, 100));
-
-////                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
-////            }
-
-////            [Fact]
-////            public void Arrange_Invokes_Controller_UpdateControls()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var controller = new Mock<IVirtualizingController>();
-
-////                ((IVirtualizingPanel)target).Controller = controller.Object;
-////                target.Measure(new Size(100, 100));
-////                target.Arrange(new Rect(0, 0, 110, 110));
-
-////                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
-////            }
-
-////            [Fact]
-////            public void Reports_IsFull_False_Until_Measure_Height_Is_Reached()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var vp = (IVirtualizingPanel)target;
-
-////                target.Measure(new Size(100, 100));
-
-////                Assert.Equal(new Size(0, 0), target.DesiredSize);
-////                Assert.Equal(new Size(0, 0), target.Bounds.Size);
-
-////                Assert.False(vp.IsFull);
-////                Assert.Equal(0, vp.OverflowCount);
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                Assert.False(vp.IsFull);
-////                Assert.Equal(0, vp.OverflowCount);
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                Assert.True(vp.IsFull);
-////                Assert.Equal(0, vp.OverflowCount);
-////            }
-
-////            [Fact]
-////            public void Reports_Overflow_After_Arrange()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var vp = (IVirtualizingPanel)target;
-
-////                target.Measure(new Size(100, 100));
-////                target.Arrange(new Rect(target.DesiredSize));
-
-////                Assert.Equal(new Size(0, 0), target.Bounds.Size);
-
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                Assert.Equal(0, vp.OverflowCount);
-
-////                target.Measure(new Size(100, 100));
-////                target.Arrange(new Rect(target.DesiredSize));
-
-////                Assert.Equal(2, vp.OverflowCount);
-////            }
-
-////            [Fact]
-////            public void Reports_Correct_Overflow_During_Arrange()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var vp = (IVirtualizingPanel)target;
-////                var controller = new Mock<IVirtualizingController>();
-////                var called = false;
-
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-////                target.Measure(new Size(100, 100));
-
-////                controller.Setup(x => x.UpdateControls()).Callback(() =>
-////                {
-////                    Assert.Equal(2, vp.PixelOverflow);
-////                    Assert.Equal(0, vp.OverflowCount);
-////                    called = true;
-////                });
-
-////                vp.Controller = controller.Object;
-////                target.Arrange(new Rect(target.DesiredSize));
-
-////                Assert.True(called);
-////            }
-
-////            [Fact]
-////            public void Reports_PixelOverflow_After_Arrange()
-////            {
-////                var target = new VirtualizingStackPanel();
-
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-
-////                target.Measure(new Size(100, 100));
-////                target.Arrange(new Rect(target.DesiredSize));
-
-////                Assert.Equal(2, ((IVirtualizingPanel)target).PixelOverflow);
-////            }
-
-////            [Fact]
-////            public void Reports_PixelOverflow_After_Arrange_Smaller_Than_Measure()
-////            {
-////                var target = new VirtualizingStackPanel();
-
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-
-////                target.Measure(new Size(100, 100));
-////                target.Arrange(new Rect(0, 0, 50, 50));
-
-////                Assert.Equal(52, ((IVirtualizingPanel)target).PixelOverflow);
-////            }
-
-////            [Fact]
-////            public void Reports_PixelOverflow_With_PixelOffset()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var vp = (IVirtualizingPanel)target;
-
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-////                vp.PixelOffset = 2;
-
-////                target.Measure(new Size(100, 100));
-////                target.Arrange(new Rect(target.DesiredSize));
-
-////                Assert.Equal(2, vp.PixelOverflow);
-////            }
-
-////            [Fact]
-////            public void PixelOffset_Can_Be_More_Than_Child_Without_Affecting_IsFull()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var vp = (IVirtualizingPanel)target;
-
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-////                vp.PixelOffset = 55;
-
-////                target.Measure(new Size(100, 100));
-////                target.Arrange(new Rect(target.DesiredSize));
-
-////                Assert.Equal(55, vp.PixelOffset);
-////                Assert.Equal(2, vp.PixelOverflow);
-////                Assert.True(vp.IsFull);
-////            }
-
-////            [Fact]
-////            public void Passes_Navigation_Request_To_ILogicalScrollable_Parent()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var presenter = new TestPresenter { Child = target };
-////                var from = new Canvas();
-
-////                ((INavigableContainer)target).GetControl(NavigationDirection.Next, from, false);
-
-////                Assert.Equal(1, presenter.NavigationRequests.Count);
-////                Assert.Equal((NavigationDirection.Next, from), presenter.NavigationRequests[0]);
-////            }
-
-////            private class TestPresenter : Decorator, ILogicalScrollable
-////            {
-////                public bool CanHorizontallyScroll { get; set; }
-////                public bool CanVerticallyScroll { get; set; }
-////                public bool IsLogicalScrollEnabled => true;
-////                public Size ScrollSize { get; }
-////                public Size PageScrollSize { get; }
-////                public Size Extent { get; }
-////                public Vector Offset { get; set; }
-////                public Size Viewport { get; }
-
-////                public event EventHandler ScrollInvalidated;
-
-////                public List<(NavigationDirection, Control)> NavigationRequests { get; } = new();
-
-////                public bool BringIntoView(Control target, Rect targetRect)
-////                {
-////                    throw new NotImplementedException();
-////                }
-
-////                public Control GetControlInDirection(NavigationDirection direction, Control from)
-////                {
-////                    NavigationRequests.Add((direction, from));
-////                    return null;
-////                }
-
-////                public void RaiseScrollInvalidated(EventArgs e)
-////                {
-////                    throw new NotImplementedException();
-////                }
-////            }
-////        }
-////    }
-////}
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs
new file mode 100644
index 00000000000..7f7a956f2cc
--- /dev/null
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs
@@ -0,0 +1,197 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Linq;
+using Avalonia.Controls.Presenters;
+using Avalonia.Controls.Templates;
+using Avalonia.Data;
+using Avalonia.Layout;
+using Avalonia.LogicalTree;
+using Avalonia.UnitTests;
+using Avalonia.VisualTree;
+using Xunit;
+
+namespace Avalonia.Controls.UnitTests
+{
+    public class VirtualizingStackPanelTests_Smooth
+    {
+        [Fact]
+        public void Creates_Initial_Items()
+        {
+            using var app = App();
+
+            var (target, scroll, itemsControl) = CreateTarget();
+
+            Assert.Equal(1000, scroll.Extent.Height);
+
+            AssertRealizedItems(target, itemsControl, 0, 10);
+        }
+
+        [Fact]
+        public void Scrolls_Down_One_Item()
+        {
+            using var app = App();
+
+            var (target, scroll, itemsControl) = CreateTarget();
+
+            scroll.Offset = new Vector(0, 10);
+            Layout(target);
+
+            AssertRealizedItems(target, itemsControl, 1, 10);
+        }
+
+        [Fact]
+        public void Scrolls_Down_More_Than_A_Page()
+        {
+            using var app = App();
+
+            var (target, scroll, itemsControl) = CreateTarget();
+
+            scroll.Offset = new Vector(0, 200);
+            Layout(target);
+
+            AssertRealizedItems(target, itemsControl, 20, 10);
+        }
+
+        [Fact]
+        public void Creates_Elements_For_Inserted_Item()
+        {
+            using var app = App();
+
+            var (target, _, itemsControl) = CreateTarget();
+            var items = (IList)itemsControl.Items;
+
+            Assert.Equal(10, target.GetRealizedElements().Count);
+
+            items.Insert(2, "new");
+
+            Assert.Equal(11, target.GetRealizedElements().Count);
+
+            var indexes = GetRealizedIndexes(target, itemsControl);
+
+            // Blank space inserted in realized elements and subsequent row indexes updated.
+            Assert.Equal(new[] { 0, 1, -1, 3, 4, 5, 6, 7, 8, 9, 10 }, indexes);
+
+            var elements = target.GetRealizedElements().ToList();
+            Layout(target);
+
+            indexes = GetRealizedIndexes(target, itemsControl);
+
+            // After layout an element for the new row is created.
+            Assert.Equal(Enumerable.Range(0, 10), indexes);
+
+            // But apart from the new row and the removed last row, all existing elements should be the same.
+            elements[2] = target.GetRealizedElements().ElementAt(2);
+            elements.RemoveAt(elements.Count - 1);
+            Assert.Equal(elements, target.GetRealizedElements());
+        }
+
+        [Fact]
+        public void Updates_Elements_On_Removed_Row()
+        {
+            using var app = App();
+
+            var (target, _, itemsControl) = CreateTarget();
+            var items = (IList)itemsControl.Items;
+
+            Assert.Equal(10, target.GetRealizedElements().Count);
+
+            var toRecycle = target.GetRealizedElements().ElementAt(2);
+            items.RemoveAt(2);
+
+            var indexes = GetRealizedIndexes(target, itemsControl);
+
+            // Item removed from realized elements and subsequent row indexes updated.
+            Assert.Equal(Enumerable.Range(0, 9), indexes);
+
+            var elements = target.GetRealizedElements().ToList();
+            Layout(target);
+
+            indexes = GetRealizedIndexes(target, itemsControl);
+
+            // After layout an element for the newly visible last row is created and indexes updated.
+            Assert.Equal(Enumerable.Range(0, 10), indexes);
+
+            // And the removed row should now have been recycled as the last row.
+            elements.Add(toRecycle);
+            Assert.Equal(elements, target.GetRealizedElements());
+        }
+
+        private static IReadOnlyList<int> GetRealizedIndexes(VirtualizingStackPanel target, ItemsControl itemsControl)
+        {
+            return target.GetRealizedElements()
+                .Select(x => x is null ? -1 : itemsControl.ItemContainerGenerator.IndexFromContainer((Control)x))
+                .ToList();
+        }
+
+        private static void AssertRealizedItems(
+            VirtualizingStackPanel target,
+            ItemsControl itemsControl,
+            int firstIndex,
+            int count)
+        {
+            var childIndexes = target.GetLogicalChildren()
+                .Select(x => itemsControl.ItemContainerGenerator.IndexFromContainer((Control)x))
+                .Where(x => x >= 0)
+                .OrderBy(x => x)
+                .ToList();
+            Assert.Equal(Enumerable.Range(firstIndex, count), childIndexes);
+        }
+
+        private static (VirtualizingStackPanel, ScrollViewer, ItemsControl) CreateTarget(int itemCount = 100)
+        {
+            var items = new ObservableCollection<string>(Enumerable.Range(0, itemCount).Select(x => $"Item {x}"));
+            var target = new VirtualizingStackPanel();
+            
+            var presenter = new ItemsPresenter
+            {
+                [~ItemsPresenter.ItemsPanelProperty] = new TemplateBinding(ItemsPresenter.ItemsPanelProperty),
+            };
+
+            var scroll = new ScrollViewer 
+            { 
+                Content = presenter,
+                Template = ScrollViewerTemplate(),
+            };
+
+            var itemsControl = new ItemsControl
+            {
+                Items = items,
+                Template = new FuncControlTemplate<ItemsControl>((_, _) => scroll),
+                ItemsPanel = new FuncTemplate<Panel>(() => target),
+                ItemTemplate = new FuncDataTemplate<string>((x, _) => new Canvas { Width = 100, Height = 10 }),
+                [VirtualizingStackPanel.VirtualizationModeProperty] = ItemVirtualizationMode.Smooth,
+            };
+
+            var root = new TestRoot(true, itemsControl);
+            root.ClientSize = new(100, 100);
+            root.LayoutManager.ExecuteInitialLayoutPass();
+
+            return (target, scroll, itemsControl);
+        }
+
+        private static void Layout(Control target)
+        {
+            var root = (ILayoutRoot?)target.GetVisualRoot();
+            root?.LayoutManager.ExecuteLayoutPass();
+        }
+
+        private static IControlTemplate ScrollViewerTemplate()
+        {
+            return new FuncControlTemplate<ScrollViewer>((x, ns) =>
+                new ScrollContentPresenter
+                {
+                    Name = "PART_ContentPresenter",
+                    [~ContentPresenter.ContentProperty] = x[~ContentControl.ContentProperty],
+                    [~~ScrollContentPresenter.ExtentProperty] = x[~~ScrollViewer.ExtentProperty],
+                    [~~ScrollContentPresenter.OffsetProperty] = x[~~ScrollViewer.OffsetProperty],
+                    [~~ScrollContentPresenter.ViewportProperty] = x[~~ScrollViewer.ViewportProperty],
+                    [~ScrollContentPresenter.CanHorizontallyScrollProperty] = x[~ScrollViewer.CanHorizontallyScrollProperty],
+                    [~ScrollContentPresenter.CanVerticallyScrollProperty] = x[~ScrollViewer.CanVerticallyScrollProperty],
+                }.RegisterInNameScope(ns));
+        }
+
+        private static IDisposable App() => UnitTestApplication.Start();
+    }
+}

From 5d1f9f4a0f387589b2aecd585e49a43b45b859d3 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 25 Nov 2022 20:39:27 +0100
Subject: [PATCH 03/64] Removed VirtualizationMode.

If you want a different virtualization mode, use a different panel.
---
 src/Avalonia.Controls/ComboBox.cs             |  15 -
 .../ItemVirtualizationMode.cs                 |  23 -
 src/Avalonia.Controls/ListBox.cs              |  16 -
 .../VirtualizingStackPanel.Smooth.cs          | 662 -----------------
 .../VirtualizingStackPanel.cs                 | 668 ++++++++++++++++--
 .../Diagnostics/Views/ConsoleView.xaml        |   3 +-
 .../Controls/ManagedFileChooser.xaml          |   1 -
 .../Controls/ManagedFileChooser.xaml          |   3 +-
 .../ComboBoxTests.cs                          |   1 -
 .../ListBoxTests.cs                           |   6 -
 .../Primitives/SelectingItemsControlTests.cs  |   1 -
 .../VirtualizingStackPanelTests_Smooth.cs     |   1 -
 tests/Avalonia.LeakTests/ControlTests.cs      |   1 -
 .../Xaml/StyleTests.cs                        |   1 -
 14 files changed, 617 insertions(+), 785 deletions(-)
 delete mode 100644 src/Avalonia.Controls/ItemVirtualizationMode.cs
 delete mode 100644 src/Avalonia.Controls/VirtualizingStackPanel.Smooth.cs

diff --git a/src/Avalonia.Controls/ComboBox.cs b/src/Avalonia.Controls/ComboBox.cs
index f8b0ebbbce1..41c17bd3e19 100644
--- a/src/Avalonia.Controls/ComboBox.cs
+++ b/src/Avalonia.Controls/ComboBox.cs
@@ -53,12 +53,6 @@ public class ComboBox : SelectingItemsControl
         public static readonly DirectProperty<ComboBox, object?> SelectionBoxItemProperty =
             AvaloniaProperty.RegisterDirect<ComboBox, object?>(nameof(SelectionBoxItem), o => o.SelectionBoxItem);
 
-        /// <summary>
-        /// Defines the <see cref="VirtualizationMode"/> property.
-        /// </summary>
-        public static readonly StyledProperty<ItemVirtualizationMode> VirtualizationModeProperty =
-            VirtualizingStackPanel.VirtualizationModeProperty.AddOwner<ComboBox>();
-
         /// <summary>
         /// Defines the <see cref="PlaceholderText"/> property.
         /// </summary>
@@ -146,15 +140,6 @@ public IBrush? PlaceholderForeground
             set { SetValue(PlaceholderForegroundProperty, value); }
         }
 
-        /// <summary>
-        /// Gets or sets the virtualization mode for the items.
-        /// </summary>
-        public ItemVirtualizationMode VirtualizationMode
-        {
-            get { return GetValue(VirtualizationModeProperty); }
-            set { SetValue(VirtualizationModeProperty, value); }
-        }
-
         /// <summary>
         /// Gets or sets the horizontal alignment of the content within the control.
         /// </summary>
diff --git a/src/Avalonia.Controls/ItemVirtualizationMode.cs b/src/Avalonia.Controls/ItemVirtualizationMode.cs
deleted file mode 100644
index 66dd32d28cc..00000000000
--- a/src/Avalonia.Controls/ItemVirtualizationMode.cs
+++ /dev/null
@@ -1,23 +0,0 @@
-namespace Avalonia.Controls
-{
-    /// <summary>
-    /// Describes the item virtualization method to use for a list.
-    /// </summary>
-    public enum ItemVirtualizationMode
-    {
-        /// <summary>
-        /// Do not virtualize items.
-        /// </summary>
-        None,
-
-        /// <summary>
-        /// Virtualize items without smooth scrolling.
-        /// </summary>
-        Simple,
-
-        /// <summary>
-        /// Virtualize items with smooth scrolling.
-        /// </summary>
-        Smooth,
-    }
-}
diff --git a/src/Avalonia.Controls/ListBox.cs b/src/Avalonia.Controls/ListBox.cs
index cb9f2f42ef9..a8a926691a8 100644
--- a/src/Avalonia.Controls/ListBox.cs
+++ b/src/Avalonia.Controls/ListBox.cs
@@ -47,12 +47,6 @@ public class ListBox : SelectingItemsControl
         public static readonly new StyledProperty<SelectionMode> SelectionModeProperty = 
             SelectingItemsControl.SelectionModeProperty;
 
-        /// <summary>
-        /// Defines the <see cref="VirtualizationMode"/> property.
-        /// </summary>
-        public static readonly StyledProperty<ItemVirtualizationMode> VirtualizationModeProperty =
-            VirtualizingStackPanel.VirtualizationModeProperty.AddOwner<ListBox>();
-
         private IScrollable? _scroll;
 
         /// <summary>
@@ -61,7 +55,6 @@ public class ListBox : SelectingItemsControl
         static ListBox()
         {
             ItemsPanelProperty.OverrideDefaultValue<ListBox>(DefaultPanel);
-            VirtualizationModeProperty.OverrideDefaultValue<ListBox>(ItemVirtualizationMode.Smooth);
         }
 
         /// <summary>
@@ -100,15 +93,6 @@ public IScrollable? Scroll
             set { base.SelectionMode = value; }
         }
 
-        /// <summary>
-        /// Gets or sets the virtualization mode for the items.
-        /// </summary>
-        public ItemVirtualizationMode VirtualizationMode
-        {
-            get { return GetValue(VirtualizationModeProperty); }
-            set { SetValue(VirtualizationModeProperty, value); }
-        }
-
         /// <summary>
         /// Selects all items in the <see cref="ListBox"/>.
         /// </summary>
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.Smooth.cs b/src/Avalonia.Controls/VirtualizingStackPanel.Smooth.cs
deleted file mode 100644
index 1f6d8319fb3..00000000000
--- a/src/Avalonia.Controls/VirtualizingStackPanel.Smooth.cs
+++ /dev/null
@@ -1,662 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Collections.Specialized;
-using System.Diagnostics;
-using Avalonia.Controls.Utils;
-using Avalonia.Layout;
-using Avalonia.Utilities;
-using Avalonia.VisualTree;
-
-namespace Avalonia.Controls
-{
-    public partial class VirtualizingStackPanel : VirtualizingPanel
-    {
-        private static readonly Rect s_invalidViewport = new(double.PositiveInfinity, double.PositiveInfinity, 0, 0);
-        private readonly Action<Control> _recycleElement;
-        private readonly Action<Control, int> _updateElementIndex;
-        private int _anchorIndex = -1;
-        private Control? _anchorElement;
-        private bool _isWaitingForViewportUpdate;
-        private double _lastEstimatedElementSizeU = 25;
-        private RealizedElementList? _measureElements;
-        private RealizedElementList? _realizedElements;
-        private Rect _viewport = s_invalidViewport;
-
-        private Size MeasureOverrideSmooth(Size availableSize)
-        {
-            if (!IsEffectivelyVisible)
-                return default;
-
-            var items = ItemsControl?.Items as IList;
-
-            if (items is null || items.Count == 0)
-            {
-                Children.Clear();
-                return default;
-            }
-
-            var orientation = Orientation;
-
-            _realizedElements ??= new();
-            _measureElements ??= new();
-
-            // If we're bringing an item into view, ignore any layout passes until we receive a new
-            // effective viewport.
-            if (_isWaitingForViewportUpdate)
-            {
-                var sizeV = orientation == Orientation.Horizontal ? DesiredSize.Height : DesiredSize.Width;
-                return CalculateDesiredSize(orientation, items, sizeV);
-            }
-
-            // We handle horizontal and vertical layouts here so X and Y are abstracted to:
-            // - Horizontal layouts: U = horizontal, V = vertical
-            // - Vertical layouts: U = vertical, V = horizontal
-            var viewport = CalculateMeasureViewport(items);
-
-            // Recycle elements outside of the expected range.
-            _realizedElements.RecycleElementsBefore(viewport.firstIndex, _recycleElement);
-            _realizedElements.RecycleElementsAfter(viewport.estimatedLastIndex, _recycleElement);
-
-            // Do the measure, creating/recycling elements as necessary to fill the viewport. Don't
-            // write to _realizedElements yet, only _measureElements.
-            GenerateElements(availableSize, ref viewport);
-
-            // Now we know what definitely fits, recycle anything left over.
-            _realizedElements.RecycleElementsAfter(_measureElements.LastModelIndex, _recycleElement);
-
-            // And swap the measureElements and realizedElements collection.
-            (_measureElements, _realizedElements) = (_realizedElements, _measureElements);
-            _measureElements.ResetForReuse();
-
-            return CalculateDesiredSize(orientation, items, viewport.measuredV);
-        }
-
-        private Size ArrangeOverrideSmooth(Size finalSize)
-        {
-            Debug.Assert(_realizedElements is not null);
-
-            var orientation = Orientation;
-            var u = _realizedElements!.StartU;
-
-            for (var i = 0; i < _realizedElements.Count; ++i)
-            {
-                var e = _realizedElements.Elements[i];
-
-                if (e is object)
-                {
-                    var sizeU = _realizedElements.SizeU[i];
-                    var rect = orientation == Orientation.Horizontal ?
-                        new Rect(u, 0, sizeU, finalSize.Height) :
-                        new Rect(0, u, finalSize.Width, sizeU);
-                    e.Arrange(rect);
-                    u += orientation == Orientation.Horizontal ? rect.Width : rect.Height;
-                }
-            }
-
-            return finalSize;
-        }
-
-        private MeasureViewport CalculateMeasureViewport(IList items)
-        {
-            Debug.Assert(_realizedElements is not null);
-
-            // If the control has not yet been laid out then the effective viewport won't have been set.
-            // Try to work it out from an ancestor control.
-            var viewport = _viewport != s_invalidViewport ? _viewport : EstimateViewport();
-
-            // Get the viewport in the orientation direction.
-            var viewportStart = Orientation == Orientation.Horizontal ? viewport.X : viewport.Y;
-            var viewportEnd = Orientation == Orientation.Horizontal ? viewport.Right : viewport.Bottom;
-
-            var (firstIndex, firstIndexU) = _realizedElements!.GetElementAt(viewportStart);
-            var (lastIndex, _) = _realizedElements.GetElementAt(viewportEnd);
-            var estimatedElementSize = -1.0;
-            var itemCount = items?.Count ?? 0;
-
-            if (firstIndex == -1)
-            {
-                estimatedElementSize = EstimateElementSizeU();
-                firstIndex = (int)(viewportStart / estimatedElementSize);
-                firstIndexU = firstIndex * estimatedElementSize;
-            }
-
-            if (lastIndex == -1)
-            {
-                if (estimatedElementSize == -1)
-                    estimatedElementSize = EstimateElementSizeU();
-                lastIndex = (int)(viewportEnd / estimatedElementSize);
-            }
-
-            return new MeasureViewport
-            {
-                firstIndex = MathUtilities.Clamp(firstIndex, 0, itemCount - 1),
-                estimatedLastIndex = MathUtilities.Clamp(lastIndex, 0, itemCount - 1),
-                viewportUStart = viewportStart,
-                viewportUEnd = viewportEnd,
-                startU = firstIndexU,
-            };
-        }
-
-        private Size CalculateDesiredSize(Orientation orientation, IList items, double sizeV)
-        {
-            var sizeU = EstimateElementSizeU() * items.Count;
-
-            if (double.IsInfinity(sizeU) || double.IsNaN(sizeU))
-                throw new InvalidOperationException("Invalid calculated size.");
-
-            return orientation == Orientation.Horizontal ?
-                new Size(sizeU, sizeV) :
-                new Size(sizeV, sizeU);
-        }
-
-        private double EstimateElementSizeU()
-        {
-            var count = _realizedElements!.Count;
-            var divisor = 0.0;
-            var total = 0.0;
-
-            for (var i = 0; i < count; ++i)
-            {
-                if (_realizedElements.Elements[i] is object)
-                {
-                    total += _realizedElements.SizeU[i];
-                    ++divisor;
-                }
-            }
-
-            if (divisor == 0 || total == 0)
-                return _lastEstimatedElementSizeU;
-
-            _lastEstimatedElementSizeU = total / divisor;
-            return _lastEstimatedElementSizeU;
-        }
-
-        private Rect EstimateViewport()
-        {
-            var c = this.GetVisualParent();
-            var viewport = new Rect();
-
-            if (c is null)
-            {
-                return viewport;
-            }
-
-            while (c is not null)
-            {
-                if (!c.Bounds.IsEmpty && c.TransformToVisual(this) is Matrix transform)
-                {
-                    viewport = new Rect(0, 0, c.Bounds.Width, c.Bounds.Height)
-                        .TransformToAABB(transform);
-                    break;
-                }
-
-                c = c?.GetVisualParent();
-            }
-
-
-            return viewport;
-        }
-
-        private void GenerateElements(Size availableSize, ref MeasureViewport viewport)
-        {
-            Debug.Assert(ItemsControl?.Items is IList);
-            Debug.Assert(_measureElements is not null);
-
-            var items = (IList)ItemsControl!.Items;
-            var horizontal = Orientation == Orientation.Horizontal;
-            var index = viewport.firstIndex;
-            var u = viewport.startU;
-
-            do
-            {
-                var e = GetOrCreateElement(items, index);
-                e.Measure(availableSize);
-
-                var sizeU = horizontal ? e.DesiredSize.Width : e.DesiredSize.Height;
-                var sizeV = horizontal ? e.DesiredSize.Height : e.DesiredSize.Width;
-
-                _measureElements!.Add(index, e, u, sizeU);
-                viewport.measuredV = Math.Max(viewport.measuredV, sizeV);
-
-                u += sizeU;
-                ++index;
-            } while (u < viewport.viewportUEnd && index < items.Count);
-        }
-
-        private Control GetOrCreateElement(IList items, int index)
-        {
-            var e = GetRealizedElement(index) ?? GetRecycledOrCreateElement(items, index);
-            InvalidateHack(e);
-            return e;
-        }
-
-        private Control? GetRealizedElement(int index)
-        {
-            Debug.Assert(_realizedElements is not null);
-
-            if (_anchorIndex == index)
-                return _anchorElement;
-            return _realizedElements!.GetElement(index);
-        }
-
-        private Control GetRecycledOrCreateElement(IList items, int index)
-        {
-            Debug.Assert(ItemsControl is not null);
-
-            var c = ItemsControl!.ItemContainerGenerator.Materialize(index, items[index]!).ContainerControl;
-            Children.Add(c);
-            return c;
-        }
-
-        private void RecycleElement(Control element)
-        {
-            Debug.Assert(ItemsControl is not null);
-
-            var index = ItemsControl.ItemContainerGenerator!.IndexFromContainer(element);
-            ItemsControl!.ItemContainerGenerator.Dematerialize(index, 1);
-            Children.Remove(element);
-        }
-
-        private void UpdateElementIndex(Control element, int index)
-        {
-            // TODO: Implement this after we refactor ItemContainerGenerator.
-        }
-
-        private void OnEffectiveViewportChanged(object? sender, EffectiveViewportChangedEventArgs e)
-        {
-            _viewport = e.EffectiveViewport;
-            _isWaitingForViewportUpdate = false;
-            InvalidateMeasure();
-        }
-
-        private void OnItemsChangedSmooth(NotifyCollectionChangedEventArgs e)
-        {
-            if (_realizedElements is null)
-                return;
-
-            switch (e.Action)
-            {
-                case NotifyCollectionChangedAction.Add:
-                    _realizedElements.ItemsInserted(e.NewStartingIndex, e.NewItems!.Count, _updateElementIndex);
-                    ItemsControl!.ItemContainerGenerator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
-                    break;
-                case NotifyCollectionChangedAction.Remove:
-                    _realizedElements.ItemsRemoved(e.OldStartingIndex, e.OldItems!.Count, _updateElementIndex, _recycleElement);
-                    ItemsControl!.ItemContainerGenerator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
-                    break;
-                case NotifyCollectionChangedAction.Reset:
-                    ////RecycleAllElements();
-                    break;
-            }
-
-            InvalidateMeasure();
-        }
-
-        private static void InvalidateHack(Control c)
-        {
-            bool HasInvalidations(Control c)
-            {
-                if (!c.IsMeasureValid)
-                    return true;
-
-                for (var i = 0; i < c.VisualChildren.Count; ++i)
-                {
-                    if (c.VisualChildren[i] is Control child)
-                    {
-                        if (!child.IsMeasureValid || HasInvalidations(child))
-                            return true;
-                    }
-                }
-
-                return false;
-            }
-
-            void Invalidate(Control c)
-            {
-                c.InvalidateMeasure();
-                for (var i = 0; i < c.VisualChildren.Count; ++i)
-                {
-                    if (c.VisualChildren[i] is Control child)
-                        Invalidate(child);
-                }
-            }
-
-            if (HasInvalidations(c))
-                Invalidate(c);
-        }
-
-        /// <summary>
-        /// Stores the realized element state for a <see cref="VirtualizingStackPanel"/> in smooth mode.
-        /// </summary>
-        internal class RealizedElementList
-        {
-            private int _firstIndex;
-            private List<Control?>? _elements;
-            private List<double>? _sizes;
-            private double _startU;
-
-            /// <summary>
-            /// Gets the number of realized elements.
-            /// </summary>
-            public int Count => _elements?.Count ?? 0;
-
-            /// <summary>
-            /// Gets the model index of the first realized element, or -1 if no elements are realized.
-            /// </summary>
-            public int FirstModelIndex => _elements?.Count > 0 ? _firstIndex : -1;
-
-            /// <summary>
-            /// Gets the model index of the last realized element, or -1 if no elements are realized.
-            /// </summary>
-            public int LastModelIndex => _elements?.Count > 0 ? _firstIndex + _elements.Count - 1 : -1;
-
-            /// <summary>
-            /// Gets the elements.
-            /// </summary>
-            public IReadOnlyList<Control?> Elements => _elements ??= new List<Control?>();
-
-            /// <summary>
-            /// Gets the sizes of the elements on the primary axis.
-            /// </summary>
-            public IReadOnlyList<double> SizeU => _sizes ??= new List<double>();
-
-            /// <summary>
-            /// Gets the position of the first element on the primary axis.
-            /// </summary>
-            public double StartU => _startU;
-
-            /// <summary>
-            /// Adds a newly realized element to the collection.
-            /// </summary>
-            /// <param name="modelIndex">The model index of the element.</param>
-            /// <param name="element">The element.</param>
-            /// <param name="u">The position of the elemnt on the primary axis.</param>
-            /// <param name="sizeU">The size of the element on the primary axis.</param>
-            public void Add(int modelIndex, Control element, double u, double sizeU)
-            {
-                if (modelIndex < 0)
-                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
-
-                _elements ??= new List<Control?>();
-                _sizes ??= new List<double>();
-
-                if (Count == 0)
-                {
-                    _elements.Add(element);
-                    _sizes.Add(sizeU);
-                    _startU = u;
-                    _firstIndex = modelIndex;
-                }
-                else if (modelIndex == LastModelIndex + 1)
-                {
-                    _elements.Add(element);
-                    _sizes.Add(sizeU);
-                }
-                else if (modelIndex == FirstModelIndex - 1)
-                {
-                    --_firstIndex;
-                    _elements.Insert(0, element);
-                    _sizes.Insert(0, sizeU);
-                    _startU = u;
-                }
-                else
-                {
-                    throw new NotSupportedException("Can only add items to the beginning or end of realized elements.");
-                }
-            }
-
-            /// <summary>
-            /// Gets the element at the specified model index, if realized.
-            /// </summary>
-            /// <param name="modelIndex">The index in the source collection of the element to get.</param>
-            /// <returns>The element if realized; otherwise null.</returns>
-            public Control? GetElement(int modelIndex)
-            {
-                var index = modelIndex - FirstModelIndex;
-                if (index >= 0 && index < _elements?.Count)
-                    return _elements[index];
-                return null;
-            }
-
-            /// <summary>
-            /// Gets the element at the specified position on the primary axis, if realized.
-            /// </summary>
-            /// <param name="position">The position.</param>
-            /// <returns>
-            /// A tuple containing the index of the element (or -1 if not found) and the position of the element on the
-            /// primary axis.
-            /// </returns>
-            public (int index, double position) GetElementAt(double position)
-            {
-                if (_sizes is null || position < StartU)
-                    return (-1, 0);
-
-                var u = StartU;
-                var i = FirstModelIndex;
-
-                foreach (var size in _sizes)
-                {
-                    var endU = u + size;
-                    if (position < endU)
-                        return (i, u);
-                    u += size;
-                    ++i;
-                }
-
-                return (-1, 0);
-            }
-
-            /// <summary>
-            /// Updates the elements in response to items being inserted into the source collection.
-            /// </summary>
-            /// <param name="modelIndex">The index in the source collection of the insert.</param>
-            /// <param name="count">The number of items inserted.</param>
-            /// <param name="updateElementIndex">A method used to update the element indexes.</param>
-            public void ItemsInserted(int modelIndex, int count, Action<Control, int> updateElementIndex)
-            {
-                if (modelIndex < 0)
-                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
-                if (_elements is null || _elements.Count == 0)
-                    return;
-
-                // Get the index within the realized _elements collection.
-                var first = FirstModelIndex;
-                var index = modelIndex - first;
-
-                if (index < Count)
-                {
-                    // The insertion point affects the realized elements. Update the index of the
-                    // elements after the insertion point.
-                    var elementCount = _elements.Count;
-                    var start = Math.Max(index, 0);
-
-                    for (var i = start; i < elementCount; ++i)
-                    {
-                        if (_elements[i] is Control element)
-                            updateElementIndex(element, first + i + count);
-                    }
-
-                    if (index <= 0)
-                    {
-                        // The insertion point was before the first element, update the first index.
-                        _firstIndex += count;
-                    }
-                    else
-                    {
-                        // The insertion point was within the realized elements, insert an empty space
-                        // in _elements and _sizes.
-                        _elements!.InsertMany(index, null, count);
-                        _sizes!.InsertMany(index, 0.0, count);
-                    }
-                }
-            }
-
-            /// <summary>
-            /// Updates the elements in response to items being removed from the source collection.
-            /// </summary>
-            /// <param name="modelIndex">The index in the source collection of the remove.</param>
-            /// <param name="count">The number of items removed.</param>
-            /// <param name="updateElementIndex">A method used to update the element indexes.</param>
-            /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void ItemsRemoved(
-                int modelIndex,
-                int count,
-                Action<Control, int> updateElementIndex,
-                Action<Control> recycleElement)
-            {
-                if (modelIndex < 0)
-                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
-                if (_elements is null || _elements.Count == 0)
-                    return;
-
-                // Get the removal start and end index within the realized _elements collection.
-                var first = FirstModelIndex;
-                var last = LastModelIndex;
-                var startIndex = modelIndex - first;
-                var endIndex = (modelIndex + count) - first;
-
-                if (endIndex < 0)
-                {
-                    // The removed range was before the realized elements. Update the first index and
-                    // the indexes of the realized elements.
-                    _firstIndex -= count;
-
-                    for (var i = 0; i < _elements.Count; ++i)
-                    {
-                        if (_elements[i] is Control element)
-                            updateElementIndex(element, _firstIndex + i);
-                    }
-                }
-                else if (startIndex < _elements.Count)
-                {
-                    // Recycle and remove the affected elements.
-                    var start = Math.Max(startIndex, 0);
-                    var end = Math.Min(endIndex, _elements.Count);
-
-                    for (var i = start; i < end; ++i)
-                    {
-                        if (_elements[i] is Control element)
-                            recycleElement(element);
-                    }
-
-                    _elements.RemoveRange(start, end - start);
-                    _sizes!.RemoveRange(start, end - start);
-
-                    // If the remove started before and ended within our realized elements, then our new
-                    // first index will be the index where the remove started.
-                    if (startIndex <= 0 && end < last)
-                        _firstIndex = first = modelIndex;
-
-                    // Update the indexes of the elements after the removed range.
-                    end = _elements.Count;
-                    for (var i = start; i < end; ++i)
-                    {
-                        if (_elements[i] is Control element)
-                            updateElementIndex(element, first + i);
-                    }
-                }
-            }
-
-            /// <summary>
-            /// Recycles elements before a specific index.
-            /// </summary>
-            /// <param name="modelIndex">The index in the source collection of new first element.</param>
-            /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void RecycleElementsBefore(int modelIndex, Action<Control> recycleElement)
-            {
-                if (modelIndex <= FirstModelIndex || _elements is null || _elements.Count == 0)
-                    return;
-
-                if (modelIndex > LastModelIndex)
-                {
-                    RecycleAllElements(recycleElement);
-                }
-                else
-                {
-                    var endIndex = modelIndex - FirstModelIndex;
-
-                    for (var i = 0; i < endIndex; ++i)
-                    {
-                        if (_elements[i] is Control e)
-                            recycleElement(e);
-                    }
-
-                    _elements.RemoveRange(0, endIndex);
-                    _sizes!.RemoveRange(0, endIndex);
-                    _firstIndex = modelIndex;
-                }
-            }
-
-            /// <summary>
-            /// Recycles elements after a specific index.
-            /// </summary>
-            /// <param name="modelIndex">The index in the source collection of new last element.</param>
-            /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void RecycleElementsAfter(int modelIndex, Action<Control> recycleElement)
-            {
-                if (modelIndex >= LastModelIndex || _elements is null || _elements.Count == 0)
-                    return;
-
-                if (modelIndex < FirstModelIndex)
-                {
-                    RecycleAllElements(recycleElement);
-                }
-                else
-                {
-                    var startIndex = (modelIndex + 1) - FirstModelIndex;
-                    var count = _elements.Count;
-
-                    for (var i = startIndex; i < count; ++i)
-                    {
-                        if (_elements[i] is Control e)
-                            recycleElement(e);
-                    }
-
-                    _elements.RemoveRange(startIndex, _elements.Count - startIndex);
-                    _sizes!.RemoveRange(startIndex, _sizes.Count - startIndex);
-                }
-            }
-
-            /// <summary>
-            /// Recycles all realized elements.
-            /// </summary>
-            /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void RecycleAllElements(Action<Control> recycleElement)
-            {
-                if (_elements is null || _elements.Count == 0)
-                    return;
-
-                foreach (var e in _elements)
-                {
-                    if (e is object)
-                        recycleElement(e);
-                }
-
-                _startU = _firstIndex = 0;
-                _elements?.Clear();
-                _sizes?.Clear();
-            }
-
-            /// <summary>
-            /// Resets the element list and prepares it for reuse.
-            /// </summary>
-            public void ResetForReuse()
-            {
-                _startU = _firstIndex = 0;
-                _elements?.Clear();
-                _sizes?.Clear();
-            }
-        }
-
-        private struct MeasureViewport
-        {
-            public int firstIndex;
-            public int estimatedLastIndex;
-            public double viewportUStart;
-            public double viewportUEnd;
-            public double measuredV;
-            public double startU;
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 78839c44b87..5d9b3b56b16 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -2,11 +2,15 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
+using System.Diagnostics;
+using Avalonia.Controls.Utils;
 using Avalonia.Layout;
+using Avalonia.Utilities;
+using Avalonia.VisualTree;
 
 namespace Avalonia.Controls
 {
-    public partial class VirtualizingStackPanel : VirtualizingPanel
+    public class VirtualizingStackPanel : VirtualizingPanel
     {
         /// <summary>
         /// Defines the <see cref="Orientation"/> property.
@@ -14,19 +18,22 @@ public partial class VirtualizingStackPanel : VirtualizingPanel
         public static readonly StyledProperty<Orientation> OrientationProperty =
             StackLayout.OrientationProperty.AddOwner<VirtualizingStackPanel>();
 
-        /// <summary>
-        /// Defines the VirtualizationMode attached property.
-        /// </summary>
-        public static readonly AttachedProperty<ItemVirtualizationMode> VirtualizationModeProperty =
-            AvaloniaProperty.RegisterAttached<VirtualizingStackPanel, Control, ItemVirtualizationMode>(
-                "VirtualizationMode", ItemVirtualizationMode.None);
-
-        private ItemVirtualizationMode _virtualizationMode;
+        private static readonly Rect s_invalidViewport = new(double.PositiveInfinity, double.PositiveInfinity, 0, 0);
+        private readonly Action<Control> _recycleElement;
+        private readonly Action<Control, int> _updateElementIndex;
+        private int _anchorIndex = -1;
+        private Control? _anchorElement;
+        private bool _isWaitingForViewportUpdate;
+        private double _lastEstimatedElementSizeU = 25;
+        private RealizedElementList? _measureElements;
+        private RealizedElementList? _realizedElements;
+        private Rect _viewport = s_invalidViewport;
 
         public VirtualizingStackPanel()
         {
             _recycleElement = RecycleElement;
             _updateElementIndex = UpdateElementIndex;
+            EffectiveViewportChanged += OnEffectiveViewportChanged;
         }
 
         /// <summary>
@@ -42,90 +49,645 @@ public Orientation Orientation
             set => SetValue(OrientationProperty, value);
         }
 
-        /// <summary>
-        /// Gets the current <see cref="ItemVirtualizationMode"/> in use for the panel.
-        /// </summary>
-        public ItemVirtualizationMode VirtualizationMode
+        protected override Size MeasureOverride(Size availableSize)
         {
-            get => _virtualizationMode;
-            set
+            if (!IsEffectivelyVisible)
+                return default;
+
+            var items = ItemsControl?.Items as IList;
+
+            if (items is null || items.Count == 0)
             {
-                if (_virtualizationMode != value)
-                {
-                    if (_virtualizationMode == ItemVirtualizationMode.Smooth)
-                        EffectiveViewportChanged -= OnEffectiveViewportChanged;
+                Children.Clear();
+                return default;
+            }
+
+            var orientation = Orientation;
+
+            _realizedElements ??= new();
+            _measureElements ??= new();
+
+            // If we're bringing an item into view, ignore any layout passes until we receive a new
+            // effective viewport.
+            if (_isWaitingForViewportUpdate)
+            {
+                var sizeV = orientation == Orientation.Horizontal ? DesiredSize.Height : DesiredSize.Width;
+                return CalculateDesiredSize(orientation, items, sizeV);
+            }
+
+            // We handle horizontal and vertical layouts here so X and Y are abstracted to:
+            // - Horizontal layouts: U = horizontal, V = vertical
+            // - Vertical layouts: U = vertical, V = horizontal
+            var viewport = CalculateMeasureViewport(items);
+
+            // Recycle elements outside of the expected range.
+            _realizedElements.RecycleElementsBefore(viewport.firstIndex, _recycleElement);
+            _realizedElements.RecycleElementsAfter(viewport.estimatedLastIndex, _recycleElement);
+
+            // Do the measure, creating/recycling elements as necessary to fill the viewport. Don't
+            // write to _realizedElements yet, only _measureElements.
+            GenerateElements(availableSize, ref viewport);
+
+            // Now we know what definitely fits, recycle anything left over.
+            _realizedElements.RecycleElementsAfter(_measureElements.LastModelIndex, _recycleElement);
+
+            // And swap the measureElements and realizedElements collection.
+            (_measureElements, _realizedElements) = (_realizedElements, _measureElements);
+            _measureElements.ResetForReuse();
+
+            return CalculateDesiredSize(orientation, items, viewport.measuredV);
+        }
+
+        protected override Size ArrangeOverride(Size finalSize)
+        {
+            Debug.Assert(_realizedElements is not null);
 
-                    _virtualizationMode = value;
+            var orientation = Orientation;
+            var u = _realizedElements!.StartU;
 
-                    if (_virtualizationMode == ItemVirtualizationMode.Smooth)
-                        EffectiveViewportChanged += OnEffectiveViewportChanged;
+            for (var i = 0; i < _realizedElements.Count; ++i)
+            {
+                var e = _realizedElements.Elements[i];
 
-                    Children.Clear();
+                if (e is object)
+                {
+                    var sizeU = _realizedElements.SizeU[i];
+                    var rect = orientation == Orientation.Horizontal ?
+                        new Rect(u, 0, sizeU, finalSize.Height) :
+                        new Rect(0, u, finalSize.Width, sizeU);
+                    e.Arrange(rect);
+                    u += orientation == Orientation.Horizontal ? rect.Width : rect.Height;
                 }
             }
+
+            return finalSize;
         }
 
-        public static ItemVirtualizationMode GetVirtualizationMode(Control c)
+        protected override void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
         {
-            return c.GetValue(VirtualizationModeProperty);
+            if (_realizedElements is null)
+                return;
+
+            switch (e.Action)
+            {
+                case NotifyCollectionChangedAction.Add:
+                    _realizedElements.ItemsInserted(e.NewStartingIndex, e.NewItems!.Count, _updateElementIndex);
+                    ItemsControl!.ItemContainerGenerator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
+                    break;
+                case NotifyCollectionChangedAction.Remove:
+                    _realizedElements.ItemsRemoved(e.OldStartingIndex, e.OldItems!.Count, _updateElementIndex, _recycleElement);
+                    ItemsControl!.ItemContainerGenerator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
+                    break;
+                case NotifyCollectionChangedAction.Reset:
+                    ////RecycleAllElements();
+                    break;
+            }
+
+            InvalidateMeasure();
         }
 
-        public static void SetVirtualizationMode(Control c, ItemVirtualizationMode value)
+        internal IReadOnlyList<Control?> GetRealizedElements()
         {
-            c.SetValue(VirtualizationModeProperty, value);
+            return _realizedElements?.Elements ?? Array.Empty<Control>();
         }
 
-        protected override Size MeasureOverride(Size availableSize)
+        private MeasureViewport CalculateMeasureViewport(IList items)
         {
-            return VirtualizationMode switch
+            Debug.Assert(_realizedElements is not null);
+
+            // If the control has not yet been laid out then the effective viewport won't have been set.
+            // Try to work it out from an ancestor control.
+            var viewport = _viewport != s_invalidViewport ? _viewport : EstimateViewport();
+
+            // Get the viewport in the orientation direction.
+            var viewportStart = Orientation == Orientation.Horizontal ? viewport.X : viewport.Y;
+            var viewportEnd = Orientation == Orientation.Horizontal ? viewport.Right : viewport.Bottom;
+
+            var (firstIndex, firstIndexU) = _realizedElements!.GetElementAt(viewportStart);
+            var (lastIndex, _) = _realizedElements.GetElementAt(viewportEnd);
+            var estimatedElementSize = -1.0;
+            var itemCount = items?.Count ?? 0;
+
+            if (firstIndex == -1)
+            {
+                estimatedElementSize = EstimateElementSizeU();
+                firstIndex = (int)(viewportStart / estimatedElementSize);
+                firstIndexU = firstIndex * estimatedElementSize;
+            }
+
+            if (lastIndex == -1)
+            {
+                if (estimatedElementSize == -1)
+                    estimatedElementSize = EstimateElementSizeU();
+                lastIndex = (int)(viewportEnd / estimatedElementSize);
+            }
+
+            return new MeasureViewport
             {
-                ItemVirtualizationMode.Smooth => MeasureOverrideSmooth(availableSize),
-                _ => throw new NotImplementedException()
+                firstIndex = MathUtilities.Clamp(firstIndex, 0, itemCount - 1),
+                estimatedLastIndex = MathUtilities.Clamp(lastIndex, 0, itemCount - 1),
+                viewportUStart = viewportStart,
+                viewportUEnd = viewportEnd,
+                startU = firstIndexU,
             };
         }
 
-        protected override Size ArrangeOverride(Size finalSize)
+        private Size CalculateDesiredSize(Orientation orientation, IList items, double sizeV)
         {
-            return VirtualizationMode switch
-            {
-                ItemVirtualizationMode.Smooth => ArrangeOverrideSmooth(finalSize),
-                _ => throw new NotImplementedException()
-            };
+            var sizeU = EstimateElementSizeU() * items.Count;
+
+            if (double.IsInfinity(sizeU) || double.IsNaN(sizeU))
+                throw new InvalidOperationException("Invalid calculated size.");
+
+            return orientation == Orientation.Horizontal ?
+                new Size(sizeU, sizeV) :
+                new Size(sizeV, sizeU);
         }
 
-        protected override void OnItemsControlChanged(ItemsControl? oldValue)
+        private double EstimateElementSizeU()
         {
-            base.OnItemsControlChanged(oldValue);
-            VirtualizationMode = ItemsControl is null ? ItemVirtualizationMode.None : GetVirtualizationMode(ItemsControl);
+            var count = _realizedElements!.Count;
+            var divisor = 0.0;
+            var total = 0.0;
+
+            for (var i = 0; i < count; ++i)
+            {
+                if (_realizedElements.Elements[i] is object)
+                {
+                    total += _realizedElements.SizeU[i];
+                    ++divisor;
+                }
+            }
+
+            if (divisor == 0 || total == 0)
+                return _lastEstimatedElementSizeU;
+
+            _lastEstimatedElementSizeU = total / divisor;
+            return _lastEstimatedElementSizeU;
         }
 
-        protected override void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
+        private Rect EstimateViewport()
         {
-            switch (VirtualizationMode)
+            var c = this.GetVisualParent();
+            var viewport = new Rect();
+
+            if (c is null)
             {
-                case ItemVirtualizationMode.Smooth:
-                    OnItemsChangedSmooth(e);
+                return viewport;
+            }
+
+            while (c is not null)
+            {
+                if (!c.Bounds.IsEmpty && c.TransformToVisual(this) is Matrix transform)
+                {
+                    viewport = new Rect(0, 0, c.Bounds.Width, c.Bounds.Height)
+                        .TransformToAABB(transform);
                     break;
+                }
+
+                c = c?.GetVisualParent();
             }
+
+
+            return viewport;
         }
 
-        internal IReadOnlyList<Control?> GetRealizedElements()
+        private void GenerateElements(Size availableSize, ref MeasureViewport viewport)
         {
-            return VirtualizationMode switch
+            Debug.Assert(ItemsControl?.Items is IList);
+            Debug.Assert(_measureElements is not null);
+
+            var items = (IList)ItemsControl!.Items;
+            var horizontal = Orientation == Orientation.Horizontal;
+            var index = viewport.firstIndex;
+            var u = viewport.startU;
+
+            do
             {
-                ItemVirtualizationMode.Smooth => _realizedElements?.Elements ?? Array.Empty<Control>(),
-                _ => Children,
-            };
+                var e = GetOrCreateElement(items, index);
+                e.Measure(availableSize);
+
+                var sizeU = horizontal ? e.DesiredSize.Width : e.DesiredSize.Height;
+                var sizeV = horizontal ? e.DesiredSize.Height : e.DesiredSize.Width;
+
+                _measureElements!.Add(index, e, u, sizeU);
+                viewport.measuredV = Math.Max(viewport.measuredV, sizeV);
+
+                u += sizeU;
+                ++index;
+            } while (u < viewport.viewportUEnd && index < items.Count);
+        }
+
+        private Control GetOrCreateElement(IList items, int index)
+        {
+            var e = GetRealizedElement(index) ?? GetRecycledOrCreateElement(items, index);
+            InvalidateHack(e);
+            return e;
+        }
+
+        private Control? GetRealizedElement(int index)
+        {
+            Debug.Assert(_realizedElements is not null);
+
+            if (_anchorIndex == index)
+                return _anchorElement;
+            return _realizedElements!.GetElement(index);
+        }
+
+        private Control GetRecycledOrCreateElement(IList items, int index)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            var c = ItemsControl!.ItemContainerGenerator.Materialize(index, items[index]!).ContainerControl;
+            Children.Add(c);
+            return c;
+        }
+
+        private void RecycleElement(Control element)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            var index = ItemsControl.ItemContainerGenerator!.IndexFromContainer(element);
+            ItemsControl!.ItemContainerGenerator.Dematerialize(index, 1);
+            Children.Remove(element);
+        }
+
+        private void UpdateElementIndex(Control element, int index)
+        {
+            // TODO: Implement this after we refactor ItemContainerGenerator.
+        }
+
+        private void OnEffectiveViewportChanged(object? sender, EffectiveViewportChangedEventArgs e)
+        {
+            _viewport = e.EffectiveViewport;
+            _isWaitingForViewportUpdate = false;
+            InvalidateMeasure();
+        }
+
+        private static void InvalidateHack(Control c)
+        {
+            bool HasInvalidations(Control c)
+            {
+                if (!c.IsMeasureValid)
+                    return true;
+
+                for (var i = 0; i < c.VisualChildren.Count; ++i)
+                {
+                    if (c.VisualChildren[i] is Control child)
+                    {
+                        if (!child.IsMeasureValid || HasInvalidations(child))
+                            return true;
+                    }
+                }
+
+                return false;
+            }
+
+            void Invalidate(Control c)
+            {
+                c.InvalidateMeasure();
+                for (var i = 0; i < c.VisualChildren.Count; ++i)
+                {
+                    if (c.VisualChildren[i] is Control child)
+                        Invalidate(child);
+                }
+            }
+
+            if (HasInvalidations(c))
+                Invalidate(c);
         }
 
-        private protected override void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+        /// <summary>
+        /// Stores the realized element state for a <see cref="VirtualizingStackPanel"/> in smooth mode.
+        /// </summary>
+        internal class RealizedElementList
         {
-            base.OnItemsControlPropertyChanged(sender, e);
+            private int _firstIndex;
+            private List<Control?>? _elements;
+            private List<double>? _sizes;
+            private double _startU;
+
+            /// <summary>
+            /// Gets the number of realized elements.
+            /// </summary>
+            public int Count => _elements?.Count ?? 0;
+
+            /// <summary>
+            /// Gets the model index of the first realized element, or -1 if no elements are realized.
+            /// </summary>
+            public int FirstModelIndex => _elements?.Count > 0 ? _firstIndex : -1;
+
+            /// <summary>
+            /// Gets the model index of the last realized element, or -1 if no elements are realized.
+            /// </summary>
+            public int LastModelIndex => _elements?.Count > 0 ? _firstIndex + _elements.Count - 1 : -1;
+
+            /// <summary>
+            /// Gets the elements.
+            /// </summary>
+            public IReadOnlyList<Control?> Elements => _elements ??= new List<Control?>();
+
+            /// <summary>
+            /// Gets the sizes of the elements on the primary axis.
+            /// </summary>
+            public IReadOnlyList<double> SizeU => _sizes ??= new List<double>();
+
+            /// <summary>
+            /// Gets the position of the first element on the primary axis.
+            /// </summary>
+            public double StartU => _startU;
+
+            /// <summary>
+            /// Adds a newly realized element to the collection.
+            /// </summary>
+            /// <param name="modelIndex">The model index of the element.</param>
+            /// <param name="element">The element.</param>
+            /// <param name="u">The position of the elemnt on the primary axis.</param>
+            /// <param name="sizeU">The size of the element on the primary axis.</param>
+            public void Add(int modelIndex, Control element, double u, double sizeU)
+            {
+                if (modelIndex < 0)
+                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+
+                _elements ??= new List<Control?>();
+                _sizes ??= new List<double>();
 
-            if (e.Property == VirtualizationModeProperty)
+                if (Count == 0)
+                {
+                    _elements.Add(element);
+                    _sizes.Add(sizeU);
+                    _startU = u;
+                    _firstIndex = modelIndex;
+                }
+                else if (modelIndex == LastModelIndex + 1)
+                {
+                    _elements.Add(element);
+                    _sizes.Add(sizeU);
+                }
+                else if (modelIndex == FirstModelIndex - 1)
+                {
+                    --_firstIndex;
+                    _elements.Insert(0, element);
+                    _sizes.Insert(0, sizeU);
+                    _startU = u;
+                }
+                else
+                {
+                    throw new NotSupportedException("Can only add items to the beginning or end of realized elements.");
+                }
+            }
+
+            /// <summary>
+            /// Gets the element at the specified model index, if realized.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of the element to get.</param>
+            /// <returns>The element if realized; otherwise null.</returns>
+            public Control? GetElement(int modelIndex)
             {
-                VirtualizationMode = e.GetNewValue<ItemVirtualizationMode>();
+                var index = modelIndex - FirstModelIndex;
+                if (index >= 0 && index < _elements?.Count)
+                    return _elements[index];
+                return null;
             }
+
+            /// <summary>
+            /// Gets the element at the specified position on the primary axis, if realized.
+            /// </summary>
+            /// <param name="position">The position.</param>
+            /// <returns>
+            /// A tuple containing the index of the element (or -1 if not found) and the position of the element on the
+            /// primary axis.
+            /// </returns>
+            public (int index, double position) GetElementAt(double position)
+            {
+                if (_sizes is null || position < StartU)
+                    return (-1, 0);
+
+                var u = StartU;
+                var i = FirstModelIndex;
+
+                foreach (var size in _sizes)
+                {
+                    var endU = u + size;
+                    if (position < endU)
+                        return (i, u);
+                    u += size;
+                    ++i;
+                }
+
+                return (-1, 0);
+            }
+
+            /// <summary>
+            /// Updates the elements in response to items being inserted into the source collection.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of the insert.</param>
+            /// <param name="count">The number of items inserted.</param>
+            /// <param name="updateElementIndex">A method used to update the element indexes.</param>
+            public void ItemsInserted(int modelIndex, int count, Action<Control, int> updateElementIndex)
+            {
+                if (modelIndex < 0)
+                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+                if (_elements is null || _elements.Count == 0)
+                    return;
+
+                // Get the index within the realized _elements collection.
+                var first = FirstModelIndex;
+                var index = modelIndex - first;
+
+                if (index < Count)
+                {
+                    // The insertion point affects the realized elements. Update the index of the
+                    // elements after the insertion point.
+                    var elementCount = _elements.Count;
+                    var start = Math.Max(index, 0);
+
+                    for (var i = start; i < elementCount; ++i)
+                    {
+                        if (_elements[i] is Control element)
+                            updateElementIndex(element, first + i + count);
+                    }
+
+                    if (index <= 0)
+                    {
+                        // The insertion point was before the first element, update the first index.
+                        _firstIndex += count;
+                    }
+                    else
+                    {
+                        // The insertion point was within the realized elements, insert an empty space
+                        // in _elements and _sizes.
+                        _elements!.InsertMany(index, null, count);
+                        _sizes!.InsertMany(index, 0.0, count);
+                    }
+                }
+            }
+
+            /// <summary>
+            /// Updates the elements in response to items being removed from the source collection.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of the remove.</param>
+            /// <param name="count">The number of items removed.</param>
+            /// <param name="updateElementIndex">A method used to update the element indexes.</param>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void ItemsRemoved(
+                int modelIndex,
+                int count,
+                Action<Control, int> updateElementIndex,
+                Action<Control> recycleElement)
+            {
+                if (modelIndex < 0)
+                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+                if (_elements is null || _elements.Count == 0)
+                    return;
+
+                // Get the removal start and end index within the realized _elements collection.
+                var first = FirstModelIndex;
+                var last = LastModelIndex;
+                var startIndex = modelIndex - first;
+                var endIndex = (modelIndex + count) - first;
+
+                if (endIndex < 0)
+                {
+                    // The removed range was before the realized elements. Update the first index and
+                    // the indexes of the realized elements.
+                    _firstIndex -= count;
+
+                    for (var i = 0; i < _elements.Count; ++i)
+                    {
+                        if (_elements[i] is Control element)
+                            updateElementIndex(element, _firstIndex + i);
+                    }
+                }
+                else if (startIndex < _elements.Count)
+                {
+                    // Recycle and remove the affected elements.
+                    var start = Math.Max(startIndex, 0);
+                    var end = Math.Min(endIndex, _elements.Count);
+
+                    for (var i = start; i < end; ++i)
+                    {
+                        if (_elements[i] is Control element)
+                            recycleElement(element);
+                    }
+
+                    _elements.RemoveRange(start, end - start);
+                    _sizes!.RemoveRange(start, end - start);
+
+                    // If the remove started before and ended within our realized elements, then our new
+                    // first index will be the index where the remove started.
+                    if (startIndex <= 0 && end < last)
+                        _firstIndex = first = modelIndex;
+
+                    // Update the indexes of the elements after the removed range.
+                    end = _elements.Count;
+                    for (var i = start; i < end; ++i)
+                    {
+                        if (_elements[i] is Control element)
+                            updateElementIndex(element, first + i);
+                    }
+                }
+            }
+
+            /// <summary>
+            /// Recycles elements before a specific index.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of new first element.</param>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void RecycleElementsBefore(int modelIndex, Action<Control> recycleElement)
+            {
+                if (modelIndex <= FirstModelIndex || _elements is null || _elements.Count == 0)
+                    return;
+
+                if (modelIndex > LastModelIndex)
+                {
+                    RecycleAllElements(recycleElement);
+                }
+                else
+                {
+                    var endIndex = modelIndex - FirstModelIndex;
+
+                    for (var i = 0; i < endIndex; ++i)
+                    {
+                        if (_elements[i] is Control e)
+                            recycleElement(e);
+                    }
+
+                    _elements.RemoveRange(0, endIndex);
+                    _sizes!.RemoveRange(0, endIndex);
+                    _firstIndex = modelIndex;
+                }
+            }
+
+            /// <summary>
+            /// Recycles elements after a specific index.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of new last element.</param>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void RecycleElementsAfter(int modelIndex, Action<Control> recycleElement)
+            {
+                if (modelIndex >= LastModelIndex || _elements is null || _elements.Count == 0)
+                    return;
+
+                if (modelIndex < FirstModelIndex)
+                {
+                    RecycleAllElements(recycleElement);
+                }
+                else
+                {
+                    var startIndex = (modelIndex + 1) - FirstModelIndex;
+                    var count = _elements.Count;
+
+                    for (var i = startIndex; i < count; ++i)
+                    {
+                        if (_elements[i] is Control e)
+                            recycleElement(e);
+                    }
+
+                    _elements.RemoveRange(startIndex, _elements.Count - startIndex);
+                    _sizes!.RemoveRange(startIndex, _sizes.Count - startIndex);
+                }
+            }
+
+            /// <summary>
+            /// Recycles all realized elements.
+            /// </summary>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void RecycleAllElements(Action<Control> recycleElement)
+            {
+                if (_elements is null || _elements.Count == 0)
+                    return;
+
+                foreach (var e in _elements)
+                {
+                    if (e is object)
+                        recycleElement(e);
+                }
+
+                _startU = _firstIndex = 0;
+                _elements?.Clear();
+                _sizes?.Clear();
+            }
+
+            /// <summary>
+            /// Resets the element list and prepares it for reuse.
+            /// </summary>
+            public void ResetForReuse()
+            {
+                _startU = _firstIndex = 0;
+                _elements?.Clear();
+                _sizes?.Clear();
+            }
+        }
+
+        private struct MeasureViewport
+        {
+            public int firstIndex;
+            public int estimatedLastIndex;
+            public double viewportUStart;
+            public double viewportUEnd;
+            public double measuredV;
+            public double startU;
         }
     }
 }
diff --git a/src/Avalonia.Diagnostics/Diagnostics/Views/ConsoleView.xaml b/src/Avalonia.Diagnostics/Diagnostics/Views/ConsoleView.xaml
index c0ba508179d..3bef23a1605 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/Views/ConsoleView.xaml
+++ b/src/Avalonia.Diagnostics/Diagnostics/Views/ConsoleView.xaml
@@ -40,8 +40,7 @@
              BorderBrush="{DynamicResource ThemeControlMidBrush}"
              BorderThickness="0,0,0,1"
              FontFamily="/Assets/Fonts/SourceSansPro-Regular.ttf"
-             Items="{Binding History}"
-             VirtualizationMode="None">
+             Items="{Binding History}">
       <ListBox.ItemTemplate>
         <DataTemplate>
           <StackPanel Orientation="Vertical">
diff --git a/src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml b/src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml
index cdfca65ff6d..9a8f41ac8a0 100644
--- a/src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml
@@ -216,7 +216,6 @@
               <TextBlock Grid.Column="8" Text="Size" />
             </Grid>
             <ListBox x:Name="PART_Files"
-                VirtualizationMode="Simple"
                 Items="{Binding Items}"
                 Margin="0 5"
                 SelectionMode="{Binding SelectionMode}"
diff --git a/src/Avalonia.Themes.Simple/Controls/ManagedFileChooser.xaml b/src/Avalonia.Themes.Simple/Controls/ManagedFileChooser.xaml
index 61dae9b4456..5514aa45932 100644
--- a/src/Avalonia.Themes.Simple/Controls/ManagedFileChooser.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/ManagedFileChooser.xaml
@@ -149,8 +149,7 @@
                      Items="{Binding Items}"
                      ScrollViewer.HorizontalScrollBarVisibility="Disabled"
                      SelectedItems="{Binding SelectedItems}"
-                     SelectionMode="{Binding SelectionMode}"
-                     VirtualizationMode="Simple">
+                     SelectionMode="{Binding SelectionMode}">
               <ListBox.ItemTemplate>
                 <DataTemplate>
                   <Grid Background="Transparent">
diff --git a/tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs b/tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs
index 6eaef4c8490..e206d809d3d 100644
--- a/tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs
@@ -285,7 +285,6 @@ public void SelectedItem_Validation()
                 var target = new ComboBox
                 {
                     Template = GetTemplate(),
-                    VirtualizationMode =  ItemVirtualizationMode.None
                 };
 
                 target.ApplyTemplate();
diff --git a/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs b/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
index b6375278b10..280f140a794 100644
--- a/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
@@ -369,7 +369,6 @@ public void ListBox_After_Scroll_IndexOutOfRangeException_Shouldnt_Be_Thrown()
         [Fact]
         public void LayoutManager_Should_Measure_Arrange_All()
         {
-            var virtualizationMode = ItemVirtualizationMode.Simple;
             using (UnitTestApplication.Start(TestServices.StyledWindow))
             {
                 var items = new AvaloniaList<string>(Enumerable.Range(1, 7).Select(v => v.ToString()));
@@ -387,7 +386,6 @@ public void LayoutManager_Should_Measure_Arrange_All()
                 target.Height = 110;
                 target.Width = 50;
                 target.DataContext = items;
-                target.VirtualizationMode = virtualizationMode;
 
                 target.ItemTemplate = new FuncDataTemplate<object>((c, _) =>
                 {
@@ -448,7 +446,6 @@ public void ListBox_Should_Be_Valid_After_Remove_Of_Item_In_NonVisibleArea()
                     AutoScrollToSelectedItem = true,
                     Height = 100,
                     Width = 50,
-                    VirtualizationMode = ItemVirtualizationMode.Simple,
                     ItemTemplate = new FuncDataTemplate<object>((c, _) => new Border() { Height = 10 }),
                     Items = items,
                 };
@@ -488,7 +485,6 @@ public void Clicking_Item_Should_Raise_BringIntoView_For_Correct_Control()
                     Items = items,
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 10 }),
                     SelectionMode = SelectionMode.AlwaysSelected,
-                    VirtualizationMode = ItemVirtualizationMode.None,
                 };
 
                 Prepare(target);
@@ -532,7 +528,6 @@ public void Adding_And_Selecting_Item_With_AutoScrollToSelectedItem_Should_NotHi
                     VerticalAlignment = Layout.VerticalAlignment.Top,
                     AutoScrollToSelectedItem = true,
                     Width = 50,
-                    VirtualizationMode = ItemVirtualizationMode.Simple,
                     ItemTemplate = new FuncDataTemplate<object>((c, _) => new Border() { Height = 10 }),
                     Items = items,
                 };
@@ -705,7 +700,6 @@ public void SelectedItem_Validation()
                 Items = new[] { "Foo" },
                 ItemTemplate = new FuncDataTemplate<string>((_, __) => new Canvas()),
                 SelectionMode = SelectionMode.AlwaysSelected,
-                VirtualizationMode = ItemVirtualizationMode.None
             };
 
             Prepare(target);
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
index 2c57c20b6c0..d89e88b2ba8 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
@@ -1475,7 +1475,6 @@ public void AutoScrollToSelectedItem_On_Reset_Works()
                             Height = 10
                         }),
                     AutoScrollToSelectedItem = true,
-                    VirtualizationMode = ItemVirtualizationMode.Simple,
                 };
 
                 var root = new TestRoot(true, target);
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs
index 7f7a956f2cc..54b76b1931f 100644
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs
@@ -161,7 +161,6 @@ private static (VirtualizingStackPanel, ScrollViewer, ItemsControl) CreateTarget
                 Template = new FuncControlTemplate<ItemsControl>((_, _) => scroll),
                 ItemsPanel = new FuncTemplate<Panel>(() => target),
                 ItemTemplate = new FuncDataTemplate<string>((x, _) => new Canvas { Width = 100, Height = 10 }),
-                [VirtualizingStackPanel.VirtualizationModeProperty] = ItemVirtualizationMode.Smooth,
             };
 
             var root = new TestRoot(true, itemsControl);
diff --git a/tests/Avalonia.LeakTests/ControlTests.cs b/tests/Avalonia.LeakTests/ControlTests.cs
index ae8df6168dd..9170c68e115 100644
--- a/tests/Avalonia.LeakTests/ControlTests.cs
+++ b/tests/Avalonia.LeakTests/ControlTests.cs
@@ -836,7 +836,6 @@ public void HotKeyManager_Should_Release_Reference_When_Control_In_Item_Template
                     {
                         Width = 100,
                         Height = 100,
-                        VirtualizationMode = ItemVirtualizationMode.None,
                         // Create a button with binding to the KeyGesture in the template and add it to references list
                         ItemTemplate = new FuncDataTemplate(typeof(KeyGesture), (o, scope) =>
                         {
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
index 70a5295008c..6361dcdbead 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
@@ -372,7 +372,6 @@ public void Style_Can_Use_NthChild_Selector_With_ListBox()
                 };
 
                 var list = window.FindControl<ListBox>("list");
-                list.VirtualizationMode = ItemVirtualizationMode.Simple;
                 list.Items = collection;
 
                 window.Show();

From 1101f28dd7a6460764873b6cc2e9ce4da293eb61 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 28 Nov 2022 18:53:03 +0100
Subject: [PATCH 04/64] Refactored ItemContainerGenerator.

A bunch of tests still failing, and some code commented out, but outlines the new API shape.
---
 src/Avalonia.Controls/ComboBox.cs             |   26 +-
 src/Avalonia.Controls/ContextMenu.cs          |    5 -
 .../Flyouts/MenuFlyoutPresenter.cs            |    5 -
 .../Generators/IItemContainerGenerator.cs     |  114 -
 .../Generators/ITreeItemContainerGenerator.cs |   18 -
 .../Generators/ItemContainerEventArgs.cs      |   49 -
 .../Generators/ItemContainerGenerator.cs      |  284 +-
 .../Generators/ItemContainerGenerator`1.cs    |  102 -
 .../Generators/ItemContainerInfo.cs           |   42 -
 .../Generators/MenuItemContainerGenerator.cs  |   21 -
 .../Generators/TabItemContainerGenerator.cs   |  105 -
 .../Generators/TreeContainerIndex.cs          |  166 -
 .../Generators/TreeItemContainerGenerator.cs  |  164 -
 src/Avalonia.Controls/ItemsControl.cs         |  205 +-
 src/Avalonia.Controls/ListBox.cs              |    9 +-
 src/Avalonia.Controls/MenuBase.cs             |   13 +-
 src/Avalonia.Controls/MenuItem.cs             |   13 +-
 .../Presenters/ItemsPresenter.cs              |   23 +-
 ...enerator.cs => PanelContainerGenerator.cs} |   57 +-
 .../Primitives/SelectingItemsControl.cs       |  138 +-
 src/Avalonia.Controls/Primitives/TabStrip.cs  |    8 -
 src/Avalonia.Controls/TabControl.cs           |   13 +-
 src/Avalonia.Controls/TreeView.cs             |  440 ++-
 src/Avalonia.Controls/TreeViewItem.cs         |   35 -
 src/Avalonia.Controls/VirtualizingPanel.cs    |  101 +-
 .../VirtualizingStackPanel.cs                 |  290 +-
 .../Diagnostics/Views/TreePageView.xaml.cs    |   12 +-
 .../CarouselTests.cs                          |  658 ++--
 .../Generators/ItemContainerGeneratorTests.cs |  173 -
 .../ItemContainerGeneratorTypedTests.cs       |   42 -
 .../ItemsControlTests.cs                      |   65 +-
 .../ListBoxTests.cs                           |  119 +-
 .../TreeViewTests.cs                          | 2900 ++++++++---------
 tests/Avalonia.LeakTests/ControlTests.cs      |   27 +-
 34 files changed, 2670 insertions(+), 3772 deletions(-)
 delete mode 100644 src/Avalonia.Controls/Generators/IItemContainerGenerator.cs
 delete mode 100644 src/Avalonia.Controls/Generators/ITreeItemContainerGenerator.cs
 delete mode 100644 src/Avalonia.Controls/Generators/ItemContainerEventArgs.cs
 delete mode 100644 src/Avalonia.Controls/Generators/ItemContainerGenerator`1.cs
 delete mode 100644 src/Avalonia.Controls/Generators/ItemContainerInfo.cs
 delete mode 100644 src/Avalonia.Controls/Generators/MenuItemContainerGenerator.cs
 delete mode 100644 src/Avalonia.Controls/Generators/TabItemContainerGenerator.cs
 delete mode 100644 src/Avalonia.Controls/Generators/TreeContainerIndex.cs
 delete mode 100644 src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs
 rename src/Avalonia.Controls/Presenters/{ItemsPresenterContainerGenerator.cs => PanelContainerGenerator.cs} (66%)
 delete mode 100644 tests/Avalonia.Controls.UnitTests/Generators/ItemContainerGeneratorTests.cs
 delete mode 100644 tests/Avalonia.Controls.UnitTests/Generators/ItemContainerGeneratorTypedTests.cs

diff --git a/src/Avalonia.Controls/ComboBox.cs b/src/Avalonia.Controls/ComboBox.cs
index 41c17bd3e19..e6af255c298 100644
--- a/src/Avalonia.Controls/ComboBox.cs
+++ b/src/Avalonia.Controls/ComboBox.cs
@@ -158,15 +158,6 @@ public VerticalAlignment VerticalContentAlignment
             set { SetValue(VerticalContentAlignmentProperty, value); }
         }
 
-        /// <inheritdoc/>
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new ItemContainerGenerator<ComboBoxItem>(
-                this,
-                ComboBoxItem.ContentProperty,
-                ComboBoxItem.ContentTemplateProperty);
-        }
-
         protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
         {
             base.OnAttachedToVisualTree(e);
@@ -449,14 +440,15 @@ private void UpdateFlowDirection()
 
         private void SelectFocusedItem()
         {
-            foreach (ItemContainerInfo dropdownItem in ItemContainerGenerator.Containers)
-            {
-                if (dropdownItem.ContainerControl.IsFocused)
-                {
-                    SelectedIndex = dropdownItem.Index;
-                    break;
-                }
-            }
+            throw new NotImplementedException();
+            ////foreach (ItemContainerInfo dropdownItem in ItemContainerGenerator.Containers)
+            ////{
+            ////    if (dropdownItem.ContainerControl.IsFocused)
+            ////    {
+            ////        SelectedIndex = dropdownItem.Index;
+            ////        break;
+            ////    }
+            ////}
         }
 
         private void SelectNext()
diff --git a/src/Avalonia.Controls/ContextMenu.cs b/src/Avalonia.Controls/ContextMenu.cs
index 020a6de5390..c0b1297b6d2 100644
--- a/src/Avalonia.Controls/ContextMenu.cs
+++ b/src/Avalonia.Controls/ContextMenu.cs
@@ -315,11 +315,6 @@ event Action<IPopupHost?>? IPopupHostProvider.PopupHostChanged
             remove => _popupHostChangedHandler -= value;
         }
 
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new MenuItemContainerGenerator(this);
-        }
-
         private void Open(Control control, Control placementTarget, bool requestedByPointer)
         {
             if (IsOpen)
diff --git a/src/Avalonia.Controls/Flyouts/MenuFlyoutPresenter.cs b/src/Avalonia.Controls/Flyouts/MenuFlyoutPresenter.cs
index 278e498a675..7aca21b42e1 100644
--- a/src/Avalonia.Controls/Flyouts/MenuFlyoutPresenter.cs
+++ b/src/Avalonia.Controls/Flyouts/MenuFlyoutPresenter.cs
@@ -35,11 +35,6 @@ public override void Open()
             throw new NotSupportedException("Use MenuFlyout.ShowAt(Control) instead");
         }
 
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new MenuItemContainerGenerator(this);
-        }
-
         protected override void OnDetachedFromVisualTree(VisualTreeAttachmentEventArgs e)
         {
             base.OnDetachedFromVisualTree(e);
diff --git a/src/Avalonia.Controls/Generators/IItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/IItemContainerGenerator.cs
deleted file mode 100644
index 8f0e3c88c1f..00000000000
--- a/src/Avalonia.Controls/Generators/IItemContainerGenerator.cs
+++ /dev/null
@@ -1,114 +0,0 @@
-using System;
-using System.Collections.Generic;
-using Avalonia.Controls.Templates;
-using Avalonia.Data;
-using Avalonia.Styling;
-
-namespace Avalonia.Controls.Generators
-{
-    /// <summary>
-    /// Creates containers for items and maintains a list of created containers.
-    /// </summary>
-    public interface IItemContainerGenerator
-    {
-        /// <summary>
-        /// Gets the currently realized containers.
-        /// </summary>
-        IEnumerable<ItemContainerInfo> Containers { get; }
-
-        /// <summary>
-        /// Gets or sets the theme to be applied to the items in the control.
-        /// </summary>
-        ControlTheme? ItemContainerTheme { get; set; }
-
-        /// <summary>
-        /// Gets or sets the data template used to display the items in the control.
-        /// </summary>
-        IDataTemplate? ItemTemplate { get; set; }
-        
-        /// <summary>
-        /// Gets or sets the binding to use to bind to the member of an item used for displaying
-        /// </summary>
-        IBinding? DisplayMemberBinding { get; set; }
-
-        /// <summary>
-        /// Gets the ContainerType, or null if its an untyped ContainerGenerator.
-        /// </summary>
-        Type? ContainerType { get; }
-
-        /// <summary>
-        /// Signaled whenever new containers are materialized.
-        /// </summary>
-        event EventHandler<ItemContainerEventArgs>? Materialized;
-
-        /// <summary>
-        /// Event raised whenever containers are dematerialized.
-        /// </summary>
-        event EventHandler<ItemContainerEventArgs>? Dematerialized;
-
-        /// <summary>
-        /// Event raised whenever containers are recycled.
-        /// </summary>
-        event EventHandler<ItemContainerEventArgs>? Recycled;
-
-        /// <summary>
-        /// Creates a container control for an item.
-        /// </summary>
-        /// <param name="index">
-        /// The index of the item of data in the control's items.
-        /// </param>
-        /// <param name="item">The item.</param>
-        /// <returns>The created controls.</returns>
-        ItemContainerInfo Materialize(int index, object item);
-
-        /// <summary>
-        /// Removes a set of created containers.
-        /// </summary>
-        /// <param name="startingIndex">
-        /// The index of the first item in the control's items.
-        /// </param>
-        /// <param name="count">The the number of items to remove.</param>
-        /// <returns>The removed containers.</returns>
-        IEnumerable<ItemContainerInfo> Dematerialize(int startingIndex, int count);
-
-        /// <summary>
-        /// Inserts space for newly inserted containers in the index.
-        /// </summary>
-        /// <param name="index">The index at which space should be inserted.</param>
-        /// <param name="count">The number of blank spaces to create.</param>
-        void InsertSpace(int index, int count);
-
-        /// <summary>
-        /// Removes a set of created containers and updates the index of later containers to fill
-        /// the gap.
-        /// </summary>
-        /// <param name="startingIndex">
-        /// The index of the first item in the control's items.
-        /// </param>
-        /// <param name="count">The the number of items to remove.</param>
-        /// <returns>The removed containers.</returns>
-        IEnumerable<ItemContainerInfo> RemoveRange(int startingIndex, int count);
-
-        bool TryRecycle(int oldIndex, int newIndex, object item);
-
-        /// <summary>
-        /// Clears all created containers and returns the removed controls.
-        /// </summary>
-        /// <returns>The removed controls.</returns>
-        IEnumerable<ItemContainerInfo> Clear();
-
-        /// <summary>
-        /// Gets the container control representing the item with the specified index.
-        /// </summary>
-        /// <param name="index">The index.</param>
-        /// <returns>The container, or null if no container created.</returns>
-        Control? ContainerFromIndex(int index);
-
-        /// <summary>
-        /// Gets the index of the specified container control.
-        /// </summary>
-        /// <param name="container">The container.</param>
-        /// <returns>The index of the container, or -1 if not found.</returns>
-        int IndexFromContainer(Control? container);
-    }
-}
diff --git a/src/Avalonia.Controls/Generators/ITreeItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/ITreeItemContainerGenerator.cs
deleted file mode 100644
index f15987fe794..00000000000
--- a/src/Avalonia.Controls/Generators/ITreeItemContainerGenerator.cs
+++ /dev/null
@@ -1,18 +0,0 @@
-namespace Avalonia.Controls.Generators
-{
-    /// <summary>
-    /// Creates containers for tree items and maintains a list of created containers.
-    /// </summary>
-    public interface ITreeItemContainerGenerator : IItemContainerGenerator
-    {
-        /// <summary>
-        /// Gets the container index for the tree.
-        /// </summary>
-        TreeContainerIndex? Index { get; }
-
-        /// <summary>
-        /// Updates the index based on the parent <see cref="TreeView"/>.
-        /// </summary>
-        void UpdateIndex();
-    }
-}
diff --git a/src/Avalonia.Controls/Generators/ItemContainerEventArgs.cs b/src/Avalonia.Controls/Generators/ItemContainerEventArgs.cs
deleted file mode 100644
index f65018531e0..00000000000
--- a/src/Avalonia.Controls/Generators/ItemContainerEventArgs.cs
+++ /dev/null
@@ -1,49 +0,0 @@
-using System;
-using System.Collections.Generic;
-
-namespace Avalonia.Controls.Generators
-{
-    /// <summary>
-    /// Provides details for the <see cref="IItemContainerGenerator.Materialized"/>
-    /// and <see cref="IItemContainerGenerator.Dematerialized"/> events.
-    /// </summary>
-    public class ItemContainerEventArgs : EventArgs
-    {
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ItemContainerEventArgs"/> class.
-        /// </summary>
-        /// <param name="container">The container.</param>
-        public ItemContainerEventArgs(ItemContainerInfo container)
-        {
-            StartingIndex = container.Index;
-            Containers = new[] { container };
-        }
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ItemContainerEventArgs"/> class.
-        /// </summary>
-        /// <param name="startingIndex">The index of the first container in the source items.</param>
-        /// <param name="containers">The containers.</param>
-        /// <remarks>
-        /// TODO: Do we really need to pass in StartingIndex here? The ItemContainerInfo objects
-        /// have an index, and what happens if the contains passed in aren't sequential?
-        /// </remarks>
-        public ItemContainerEventArgs(
-            int startingIndex, 
-            IList<ItemContainerInfo> containers)
-        {
-            StartingIndex = startingIndex;
-            Containers = containers;
-        }
-
-        /// <summary>
-        /// Gets the containers.
-        /// </summary>
-        public IList<ItemContainerInfo> Containers { get; }
-
-        /// <summary>
-        /// Gets the index of the first container in the source items.
-        /// </summary>
-        public int StartingIndex { get; }
-    }
-}
diff --git a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
index d87422e57ea..0598bb1a63b 100644
--- a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
+++ b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
@@ -1,262 +1,68 @@
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using Avalonia.Controls.Presenters;
-using Avalonia.Controls.Templates;
-using Avalonia.Data;
-using Avalonia.Styling;
 
 namespace Avalonia.Controls.Generators
 {
     /// <summary>
-    /// Creates containers for items and maintains a list of created containers.
+    /// Generates containers for an <see cref="ItemsControl"/>.
     /// </summary>
-    public class ItemContainerGenerator : IItemContainerGenerator
+    /// <remarks>
+    /// Although this class is similar to that found in WPF/UWP, in Avalonia this class only
+    /// concerns itself with generating and clearing item containers; it does not maintain a
+    /// record of the currently realized containers, that responsibility is delegated to the
+    /// items panel.
+    /// </remarks>
+    public class ItemContainerGenerator
     {
-        private SortedDictionary<int, ItemContainerInfo> _containers = new SortedDictionary<int, ItemContainerInfo>();
+        private ItemsControl _owner;
 
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ItemContainerGenerator"/> class.
-        /// </summary>
-        /// <param name="owner">The owner control.</param>
-        public ItemContainerGenerator(Control owner)
-        {
-            Owner = owner ?? throw new ArgumentNullException(nameof(owner));
-        }
-
-        /// <inheritdoc/>
-        public IEnumerable<ItemContainerInfo> Containers => _containers.Values;
-
-        /// <inheritdoc/>
-        public event EventHandler<ItemContainerEventArgs>? Materialized;
-
-        /// <inheritdoc/>
-        public event EventHandler<ItemContainerEventArgs>? Dematerialized;
-
-        /// <inheritdoc/>
-        public event EventHandler<ItemContainerEventArgs>? Recycled;
+        internal ItemContainerGenerator(ItemsControl owner) => _owner = owner;
 
         /// <summary>
-        /// Gets or sets the theme to be applied to the items in the control.
+        /// Creates a new container control.
         /// </summary>
-        public ControlTheme? ItemContainerTheme { get; set; }
+        /// <returns>The newly created container control.</returns>
+        /// <remarks>
+        /// Before calling this method, <see cref="IsItemItsOwnContainer(Control)"/> should be
+        /// called to determine whether the item itself should be used as a container. After
+        /// calling this method, <see cref="PrepareItemContainer(Control, object, int)"/> should
+        /// be called to prepare the container to display the specified item.
+        /// </remarks>
+        public Control CreateContainer() => _owner.CreateContainerOverride();
 
         /// <summary>
-        /// Gets or sets the data template used to display the items in the control.
+        /// Determines whether the specified item is (or is eligible to be) its own container.
         /// </summary>
-        public IDataTemplate? ItemTemplate { get; set; }
-        
-        /// <inheritdoc />
-        public IBinding? DisplayMemberBinding { get; set; }
+        /// <param name="container">The item.</param>
+        /// <returns>true if the item is its own container, otherwise false.</returns>
+        /// <remarks>
+        /// Whereas in WPF/UWP, non-control items can be their own container, in Avalonia only
+        /// control items may be; the caller is responsible for checking if each item is a control
+        /// and calling this method before creating a new container.
+        /// </remarks>
+        public bool IsItemItsOwnContainer(Control container) => _owner.IsItemItsOwnContainerOverride(container);
 
         /// <summary>
-        /// Gets the owner control.
+        /// Prepares the specified element as the container for the corresponding item.
         /// </summary>
-        public Control Owner { get; }
-
-        /// <inheritdoc/>
-        public virtual Type? ContainerType => null;
-
-        /// <inheritdoc/>
-        public ItemContainerInfo Materialize(int index, object item)
-        {
-            var container = new ItemContainerInfo(CreateContainer(item)!, item, index);
-
-            _containers.Add(container.Index, container);
-            Materialized?.Invoke(this, new ItemContainerEventArgs(container));
-
-            return container;
-        }
-
-        /// <inheritdoc/>
-        public virtual IEnumerable<ItemContainerInfo> Dematerialize(int startingIndex, int count)
-        {
-            var result = new List<ItemContainerInfo>();
-
-            for (int i = startingIndex; i < startingIndex + count; ++i)
-            {
-                result.Add(_containers[i]);
-                _containers.Remove(i);
-            }
-
-            Dematerialized?.Invoke(this, new ItemContainerEventArgs(startingIndex, result));
-
-            return result;
-        }
-
-        /// <inheritdoc/>
-        public virtual void InsertSpace(int index, int count)
-        {
-            if (count > 0)
-            {
-                var toMove = _containers.Where(x => x.Key >= index)
-                    .OrderByDescending(x => x.Key)
-                    .ToArray();
-
-                foreach (var i in toMove)
-                {
-                    _containers.Remove(i.Key);
-                    i.Value.Index += count;
-                    _containers.Add(i.Value.Index, i.Value);
-                }
-            }
-        }
-
-        /// <inheritdoc/>
-        public virtual IEnumerable<ItemContainerInfo> RemoveRange(int startingIndex, int count)
-        {
-            var result = new List<ItemContainerInfo>();
-
-            if (count > 0)
-            {
-                for (var i = startingIndex; i < startingIndex + count; ++i)
-                {
-                    if (_containers.TryGetValue(i, out var found))
-                    {
-                        result.Add(found);
-                    }
-
-                    _containers.Remove(i);
-                }
-
-                var toMove = _containers.Where(x => x.Key >= startingIndex)
-                                        .OrderBy(x => x.Key).ToArray();
-
-                foreach (var i in toMove)
-                {
-                    _containers.Remove(i.Key);
-                    i.Value.Index -= count;
-                    _containers.Add(i.Value.Index, i.Value);
-                }
-
-                Dematerialized?.Invoke(this, new ItemContainerEventArgs(startingIndex, result));
-
-                if (toMove.Length > 0)
-                {
-                    var containers = toMove.Select(x => x.Value).ToArray();
-                    Recycled?.Invoke(this, new ItemContainerEventArgs(containers[0].Index, containers));
-                }
-            }
-
-            return result;
-        }
-
-        /// <inheritdoc/>
-        public virtual bool TryRecycle(int oldIndex, int newIndex, object item) => false;
-
-        /// <inheritdoc/>
-        public virtual IEnumerable<ItemContainerInfo> Clear()
-        {
-            var result = Containers.ToArray();
-            _containers.Clear();
-
-            if (result.Length > 0)
-            {
-                Dematerialized?.Invoke(this, new ItemContainerEventArgs(0, result));
-            }
-
-            return result;
-        }
-
-        /// <inheritdoc/>
-        public Control? ContainerFromIndex(int index)
-        {
-            ItemContainerInfo? result;
-            _containers.TryGetValue(index, out result);
-            return result?.ContainerControl;
-        }
-
-        /// <inheritdoc/>
-        public int IndexFromContainer(Control? container)
-        {
-            foreach (var i in _containers)
-            {
-                if (i.Value.ContainerControl == container)
-                {
-                    return i.Key;
-                }
-            }
-
-            return -1;
-        }
+        /// <param name="container">The element that's used to display the specified item.</param>
+        /// <param name="item">The item to display.</param>
+        /// <param name="index">The index of the item to display.</param>
+        /// <remarks>
+        /// If <see cref="IsItemItsOwnContainer(Control)"/> is true for an item, then this method
+        /// only needs to be called a single time, otherwise this method should be called after the
+        /// container is created, and each subsequent time the container is recycled to display a
+        /// new item.
+        /// </remarks>
+        public void PrepareItemContainer(Control container, object? item, int index) => 
+            _owner.PrepareItemContainer(container, item, index);
 
         /// <summary>
-        /// Creates the container for an item.
+        /// Undoes the effects of the <see cref="PrepareItemContainer(Control, object, int)"/> method.
         /// </summary>
-        /// <param name="item">The item.</param>
-        /// <returns>The created container control.</returns>
-        protected virtual Control? CreateContainer(object item)
-        {
-            var result = item as Control;
-
-            if (result == null)
-            {
-                result = new ContentPresenter();
-                if (DisplayMemberBinding is not null)
-                {
-                    result.SetValue(StyledElement.DataContextProperty, item, BindingPriority.Style);
-                    result.Bind(ContentPresenter.ContentProperty, DisplayMemberBinding, BindingPriority.Style);
-                }
-                else
-                {
-                    result.SetValue(ContentPresenter.ContentProperty, item, BindingPriority.Style);
-                }
-
-                if (ItemTemplate != null)
-                {
-                    result.SetValue(
-                        ContentPresenter.ContentTemplateProperty,
-                        ItemTemplate,
-                        BindingPriority.Style);
-                }
-            }
+        /// <param name="container">The element that's used to display the specified item.</param>
+        public void ClearItemContainer(Control container) => _owner.ClearContainerForItemOverride(container);
 
-            if (ItemContainerTheme != null)
-            {
-                result.SetValue(
-                    StyledElement.ThemeProperty,
-                    ItemContainerTheme,
-                    BindingPriority.Template);
-            }
-
-            return result;
-        }
-
-        /// <summary>
-        /// Moves a container.
-        /// </summary>
-        /// <param name="oldIndex">The old index.</param>
-        /// <param name="newIndex">The new index.</param>
-        /// <param name="item">The new item.</param>
-        /// <returns>The container info.</returns>
-        protected ItemContainerInfo MoveContainer(int oldIndex, int newIndex, object item)
-        {
-            var container = _containers[oldIndex];
-            container.Index = newIndex;
-            container.Item = item;
-            _containers.Remove(oldIndex);
-            _containers.Add(newIndex, container);
-            return container;
-        }
-
-        /// <summary>
-        /// Gets all containers with an index that fall within a range.
-        /// </summary>
-        /// <param name="index">The first index.</param>
-        /// <param name="count">The number of elements in the range.</param>
-        /// <returns>The containers.</returns>
-        protected IEnumerable<ItemContainerInfo> GetContainerRange(int index, int count)
-        {
-            return _containers.Where(x => x.Key >= index && x.Key < index + count).Select(x => x.Value);
-        }
-
-        /// <summary>
-        /// Raises the <see cref="Recycled"/> event.
-        /// </summary>
-        /// <param name="e">The event args.</param>
-        protected void RaiseRecycled(ItemContainerEventArgs e)
-        {
-            Recycled?.Invoke(this, e);
-        }
+        public Control? ContainerFromIndex(int index) => _owner.ContainerFromIndex(index);
+        public int IndexFromContainer(Control container) => _owner.IndexFromContainer(container);
     }
 }
diff --git a/src/Avalonia.Controls/Generators/ItemContainerGenerator`1.cs b/src/Avalonia.Controls/Generators/ItemContainerGenerator`1.cs
deleted file mode 100644
index ad5bf0219ca..00000000000
--- a/src/Avalonia.Controls/Generators/ItemContainerGenerator`1.cs
+++ /dev/null
@@ -1,102 +0,0 @@
-using System;
-using Avalonia.Data;
-
-namespace Avalonia.Controls.Generators
-{
-    /// <summary>
-    /// Creates containers for items and maintains a list of created containers.
-    /// </summary>
-    /// <typeparam name="T">The type of the container.</typeparam>
-    public class ItemContainerGenerator<T> : ItemContainerGenerator where T : Control, new()
-    {
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ItemContainerGenerator{T}"/> class.
-        /// </summary>
-        /// <param name="owner">The owner control.</param>
-        /// <param name="contentProperty">The container's Content property.</param>
-        /// <param name="contentTemplateProperty">The container's ContentTemplate property.</param>
-        public ItemContainerGenerator(
-            Control owner,
-            AvaloniaProperty contentProperty,
-            AvaloniaProperty? contentTemplateProperty)
-            : base(owner)
-        {
-            ContentProperty = contentProperty ?? throw new ArgumentNullException(nameof(contentProperty));
-            ContentTemplateProperty = contentTemplateProperty;
-        }
-
-        /// <inheritdoc/>
-        public override Type ContainerType => typeof(T);
-
-        /// <summary>
-        /// Gets the container's Content property.
-        /// </summary>
-        protected AvaloniaProperty ContentProperty { get; }
-
-        /// <summary>
-        /// Gets the container's ContentTemplate property.
-        /// </summary>
-        protected AvaloniaProperty? ContentTemplateProperty { get; }
-
-        /// <inheritdoc/>
-        protected override Control? CreateContainer(object item)
-        {
-            var container = item as T;
-
-            if (container is null)
-            {
-                container = new T();
-
-                if (ContentTemplateProperty != null)
-                {
-                    container.SetValue(ContentTemplateProperty, ItemTemplate, BindingPriority.Style);
-                }
-
-                if (DisplayMemberBinding is not null)
-                {
-                    container.SetValue(StyledElement.DataContextProperty, item, BindingPriority.Style);
-                    container.Bind(ContentProperty, DisplayMemberBinding, BindingPriority.Style);
-                }
-                else
-                {
-                    container.SetValue(ContentProperty, item, BindingPriority.Style);
-                }
-                
-                if (!(item is Control))
-                {
-                    container.DataContext = item;
-                }
-            }
-
-            if (ItemContainerTheme != null)
-            {
-                container.SetValue(StyledElement.ThemeProperty, ItemContainerTheme, BindingPriority.Style);
-            }
-
-            return container;
-        }
-
-        /// <inheritdoc/>
-        public override bool TryRecycle(int oldIndex, int newIndex, object item)
-        {
-            var container = ContainerFromIndex(oldIndex);
-
-            if (container == null)
-            {
-                throw new IndexOutOfRangeException("Could not recycle container: not materialized.");
-            }
-
-            container.SetValue(ContentProperty, item);
-
-            if (!(item is Control))
-            {
-                container.DataContext = item;
-            }
-
-            var info = MoveContainer(oldIndex, newIndex, item);
-            RaiseRecycled(new ItemContainerEventArgs(info));
-
-            return true;
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Generators/ItemContainerInfo.cs b/src/Avalonia.Controls/Generators/ItemContainerInfo.cs
deleted file mode 100644
index 047e457e7c3..00000000000
--- a/src/Avalonia.Controls/Generators/ItemContainerInfo.cs
+++ /dev/null
@@ -1,42 +0,0 @@
-namespace Avalonia.Controls.Generators
-{
-    /// <summary>
-    /// Holds information about an item container generated by an 
-    /// <see cref="IItemContainerGenerator"/>.
-    /// </summary>
-    public class ItemContainerInfo
-    {
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ItemContainerInfo"/> class.
-        /// </summary>
-        /// <param name="container">The container control.</param>
-        /// <param name="item">The item that the container represents.</param>
-        /// <param name="index">
-        /// The index of the item in the <see cref="ItemsControl.Items"/> collection.
-        /// </param>
-        public ItemContainerInfo(Control container, object item, int index)
-        {
-            ContainerControl = container;
-            Item = item;
-            Index = index;
-        }
-
-        /// <summary>
-        /// Gets the container control.
-        /// </summary>
-        /// <remarks>
-        /// This will be null if <see cref="Item"/> is null.
-        /// </remarks>
-        public Control ContainerControl { get; }
-
-        /// <summary>
-        /// Gets the item that the container represents.
-        /// </summary>
-        public object Item { get; internal set; }
-
-        /// <summary>
-        /// Gets the index of the item in the <see cref="ItemsControl.Items"/> collection.
-        /// </summary>
-        public int Index { get; set; }
-    }
-}
diff --git a/src/Avalonia.Controls/Generators/MenuItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/MenuItemContainerGenerator.cs
deleted file mode 100644
index 0dcb6c05e16..00000000000
--- a/src/Avalonia.Controls/Generators/MenuItemContainerGenerator.cs
+++ /dev/null
@@ -1,21 +0,0 @@
-namespace Avalonia.Controls.Generators
-{
-    public class MenuItemContainerGenerator : ItemContainerGenerator<MenuItem>
-    {
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ItemContainerGenerator{T}"/> class.
-        /// </summary>
-        /// <param name="owner">The owner control.</param>
-        public MenuItemContainerGenerator(Control owner)
-            : base(owner, MenuItem.HeaderProperty, null)
-        {
-        }
-
-        /// <inheritdoc/>
-        protected override Control? CreateContainer(object item)
-        {
-            var separator = item as Separator;
-            return separator != null ? separator : base.CreateContainer(item);
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Generators/TabItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/TabItemContainerGenerator.cs
deleted file mode 100644
index b26b113fbbc..00000000000
--- a/src/Avalonia.Controls/Generators/TabItemContainerGenerator.cs
+++ /dev/null
@@ -1,105 +0,0 @@
-using System;
-using System.Collections.Generic;
-using Avalonia.Controls.Primitives;
-using Avalonia.Controls.Templates;
-using Avalonia.Data;
-using Avalonia.LogicalTree;
-using Avalonia.Reactive;
-using Avalonia.VisualTree;
-
-namespace Avalonia.Controls.Generators
-{    
-    public class TabItemContainerGenerator : ItemContainerGenerator<TabItem>
-    {
-        public TabItemContainerGenerator(TabControl owner)
-            : base(owner, ContentControl.ContentProperty, ContentControl.ContentTemplateProperty)
-        {
-            Owner = owner;
-        }
-
-        public new TabControl Owner { get; }
-
-        protected override Control CreateContainer(object item)
-        {
-            var tabItem = (TabItem)base.CreateContainer(item)!;
-
-            tabItem.Bind(TabItem.TabStripPlacementProperty, new OwnerBinding<Dock>(
-                tabItem,
-                TabControl.TabStripPlacementProperty));
-
-            if (tabItem.HeaderTemplate == null)
-            {
-                tabItem.Bind(TabItem.HeaderTemplateProperty, new OwnerBinding<IDataTemplate?>(
-                    tabItem,
-                    TabControl.ItemTemplateProperty));
-            }
-
-            if (Owner.HeaderDisplayMemberBinding is not null)
-            {
-                tabItem.Bind(HeaderedContentControl.HeaderProperty, Owner.HeaderDisplayMemberBinding,
-                    BindingPriority.Style);
-            }
-
-            if (tabItem.Header == null)
-            {
-                if (item is IHeadered headered)
-                {
-                    tabItem.Header = headered.Header;
-                }
-                else
-                {
-                    if (!(tabItem.DataContext is Control))
-                    {
-                        tabItem.Header = tabItem.DataContext;
-                    }
-                }
-            }
-
-            if (!(tabItem.Content is Control))
-            {
-                tabItem.Bind(TabItem.ContentTemplateProperty, new OwnerBinding<IDataTemplate?>(
-                    tabItem,
-                    TabControl.ContentTemplateProperty));
-            }
-
-            return tabItem;
-        }
-
-        private class OwnerBinding<T> : SingleSubscriberObservableBase<T>
-        {
-            private readonly TabItem _item;
-            private readonly StyledProperty<T> _ownerProperty;
-            private IDisposable? _ownerSubscription;
-            private IDisposable? _propertySubscription;
-
-            public OwnerBinding(TabItem item, StyledProperty<T> ownerProperty)
-            {
-                _item = item;
-                _ownerProperty = ownerProperty;
-            }
-
-            protected override void Subscribed()
-            {
-                _ownerSubscription = ControlLocator.Track(_item, 0, typeof(TabControl)).Subscribe(OwnerChanged);
-            }
-
-            protected override void Unsubscribed()
-            {
-                _ownerSubscription?.Dispose();
-                _ownerSubscription = null;
-            }
-
-            private void OwnerChanged(ILogical? c)
-            {
-                _propertySubscription?.Dispose();
-                _propertySubscription = null;
-
-                if (c is TabControl tabControl)
-                {
-                    _propertySubscription = tabControl.GetObservable(_ownerProperty)
-                        .Subscribe(x => PublishNext(x));
-                }
-            }
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Generators/TreeContainerIndex.cs b/src/Avalonia.Controls/Generators/TreeContainerIndex.cs
deleted file mode 100644
index 02b8e7003e2..00000000000
--- a/src/Avalonia.Controls/Generators/TreeContainerIndex.cs
+++ /dev/null
@@ -1,166 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-
-namespace Avalonia.Controls.Generators
-{
-    /// <summary>
-    /// Maintains an index of all item containers currently materialized by a <see cref="TreeView"/>.
-    /// </summary>
-    /// <remarks>
-    /// Each <see cref="TreeViewItem"/> has its own <see cref="TreeItemContainerGenerator{T}"/> 
-    /// that maintains the list of its direct children, but they also share an instance of this
-    /// class in their <see cref="TreeItemContainerGenerator{T}.Index"/> property which tracks 
-    /// the containers materialized for the entire tree.
-    /// </remarks>
-    public class TreeContainerIndex
-    {
-        private readonly Dictionary<object, HashSet<Control>> _itemToContainerSet = new Dictionary<object, HashSet<Control>>();
-        private readonly Dictionary<object, Control> _itemToContainer = new Dictionary<object, Control>();
-        private readonly Dictionary<Control, object> _containerToItem = new Dictionary<Control, object>();
-
-        /// <summary>
-        /// Signaled whenever new containers are materialized.
-        /// </summary>
-        public event EventHandler<ItemContainerEventArgs>? Materialized;
-
-        /// <summary>
-        /// Event raised whenever containers are dematerialized.
-        /// </summary>
-        public event EventHandler<ItemContainerEventArgs>? Dematerialized;
-
-        /// <summary>
-        /// Gets the currently materialized containers.
-        /// </summary>
-        public IEnumerable<Control> Containers => _containerToItem.Keys;
-
-        /// <summary>
-        /// Gets the items of currently materialized containers.
-        /// </summary>
-        public IEnumerable<object> Items => _containerToItem.Values;
-
-        /// <summary>
-        /// Adds an entry to the index.
-        /// </summary>
-        /// <param name="item">The item.</param>
-        /// <param name="container">The item container.</param>
-        public void Add(object item, Control container)
-        {
-            _itemToContainer[item] = container;
-            if (_itemToContainerSet.TryGetValue(item, out var set))
-            {
-                set.Add(container);
-            }
-            else
-            {
-                _itemToContainerSet.Add(item, new HashSet<Control> { container });
-            }
-
-            _containerToItem.Add(container, item);
-
-            Materialized?.Invoke(
-                this,
-                new ItemContainerEventArgs(new ItemContainerInfo(container, item, 0)));
-        }
-
-        /// <summary>
-        /// Removes a container from private collections.
-        /// </summary>
-        /// <param name="container">The item container.</param>
-        /// <param name="item">The DataContext object</param>
-        private void RemoveContainer(Control container, object item)
-        {
-            if (_itemToContainerSet.TryGetValue(item, out var set))
-            {
-                set.Remove(container);
-                if (set.Count == 0)
-                {
-                    _itemToContainerSet.Remove(item);
-                    _itemToContainer.Remove(item);
-                }
-                else
-                {
-                    _itemToContainer[item] = set.First();
-                }
-            }
-        }
-        
-        /// <summary>
-        /// Removes a container from the index.
-        /// </summary>
-        /// <param name="container">The item container.</param>
-        public void Remove(Control container)
-        {
-            var item = _containerToItem[container];
-            _containerToItem.Remove(container);
-            RemoveContainer(container, item);
-
-            Dematerialized?.Invoke(
-                this,
-                new ItemContainerEventArgs(new ItemContainerInfo(container, item, 0)));
-        }
-
-        /// <summary>
-        /// Removes a set of containers from the index.
-        /// </summary>
-        /// <param name="startingIndex">The index of the first item.</param>
-        /// <param name="containers">The item containers.</param>
-        public void Remove(int startingIndex, IEnumerable<ItemContainerInfo> containers)
-        {
-            foreach (var container in containers)
-            {
-                var item = _containerToItem[container.ContainerControl];
-                _containerToItem.Remove(container.ContainerControl);
-                RemoveContainer(container.ContainerControl, item);
-            }
-
-            Dematerialized?.Invoke(
-                this,
-                new ItemContainerEventArgs(startingIndex, containers.ToList()));
-        }
-
-        /// <summary>
-        /// Gets the container for an item.
-        /// </summary>
-        /// <param name="item">The item.</param>
-        /// <returns>The container, or null of not found.</returns>
-        public Control? ContainerFromItem(object item)
-        {
-            if (item != null)
-            {
-                _itemToContainer.TryGetValue(item, out var result);
-                if (result == null)
-                {
-                    _itemToContainerSet.TryGetValue(item, out var set);
-                    if (set?.Count > 0)
-                    {
-                        return set.FirstOrDefault();
-                    }
-                }
-                return result;
-            }
-
-            return null;
-        }
-
-        /// <summary>
-        /// Gets the item for a container.
-        /// </summary>
-        /// <param name="container">The container.</param>
-        /// <returns>The item, or null of not found.</returns>
-        public object? ItemFromContainer(Control? container)
-        {
-            if (container != null)
-            {
-                _containerToItem.TryGetValue(container, out var result);
-                if (result != null)
-                {
-                    _itemToContainer[result] = container;
-                }
-                return result;
-            }
-
-            return null;
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs
deleted file mode 100644
index b7111c0ef23..00000000000
--- a/src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs
+++ /dev/null
@@ -1,164 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using Avalonia.Controls.Templates;
-using Avalonia.Data;
-using Avalonia.LogicalTree;
-
-namespace Avalonia.Controls.Generators
-{
-    /// <summary>
-    /// Creates containers for tree items and maintains a list of created containers.
-    /// </summary>
-    /// <typeparam name="T">The type of the container.</typeparam>
-    public class TreeItemContainerGenerator<T> : ItemContainerGenerator<T>, ITreeItemContainerGenerator
-        where T : Control, new()
-    {
-        private TreeView? _treeView;
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="TreeItemContainerGenerator{T}"/> class.
-        /// </summary>
-        /// <param name="owner">The owner control.</param>
-        /// <param name="contentProperty">The container's Content property.</param>
-        /// <param name="contentTemplateProperty">The container's ContentTemplate property.</param>
-        /// <param name="itemsProperty">The container's Items property.</param>
-        /// <param name="isExpandedProperty">The container's IsExpanded property.</param>
-        public TreeItemContainerGenerator(
-            Control owner,
-            AvaloniaProperty contentProperty,
-            AvaloniaProperty contentTemplateProperty,
-            AvaloniaProperty itemsProperty,
-            AvaloniaProperty isExpandedProperty)
-            : base(owner, contentProperty, contentTemplateProperty)
-        {
-            ItemsProperty = itemsProperty ?? throw new ArgumentNullException(nameof(itemsProperty));
-            IsExpandedProperty = isExpandedProperty ?? throw new ArgumentNullException(nameof(isExpandedProperty));
-            UpdateIndex();
-        }
-
-        /// <summary>
-        /// Gets the container index for the tree.
-        /// </summary>
-        public TreeContainerIndex? Index { get; private set; }
-
-        /// <summary>
-        /// Gets the item container's Items property.
-        /// </summary>
-        protected AvaloniaProperty ItemsProperty { get; }
-
-        /// <summary>
-        /// Gets the item container's IsExpanded property.
-        /// </summary>
-        protected AvaloniaProperty IsExpandedProperty { get; }
-
-        /// <inheritdoc/>
-        protected override Control? CreateContainer(object? item)
-        {
-            var container = item as T;
-
-            if (item == null)
-            {
-                return null;
-            }
-            else if (container != null)
-            {
-                Index?.Add(item, container);
-                return container;
-            }
-            else
-            {
-                var template = GetTreeDataTemplate(item, ItemTemplate);
-                var result = new T();
-
-                if (ItemContainerTheme != null)
-                {
-                    result.SetValue(Control.ThemeProperty, ItemContainerTheme, BindingPriority.Style);
-                }
-
-                if (DisplayMemberBinding is not null)
-                {
-                    result.SetValue(StyledElement.DataContextProperty, item, BindingPriority.Style);
-                    result.Bind(ContentProperty, DisplayMemberBinding, BindingPriority.Style);
-                }
-                else
-                {
-                    result.SetValue(ContentProperty, template.Build(item), BindingPriority.Style);
-                }
-
-                var itemsSelector = template.ItemsSelector(item);
-
-                if (itemsSelector != null)
-                {
-                    BindingOperations.Apply(result, ItemsProperty, itemsSelector, null);
-                }
-
-                if (!(item is Control))
-                {
-                    result.DataContext = item;
-                }
-
-                Index?.Add(item, result);
-
-                return result;
-            }
-        }
-
-        public override IEnumerable<ItemContainerInfo> Clear()
-        {
-            var items = base.Clear();
-            Index?.Remove(0, items);
-            return items;
-        }
-
-        public override IEnumerable<ItemContainerInfo> Dematerialize(int startingIndex, int count)
-        {
-            Index?.Remove(startingIndex, GetContainerRange(startingIndex, count));
-            return base.Dematerialize(startingIndex, count);
-        }
-
-        public override IEnumerable<ItemContainerInfo> RemoveRange(int startingIndex, int count)
-        {
-            Index?.Remove(startingIndex, GetContainerRange(startingIndex, count));
-            return base.RemoveRange(startingIndex, count);
-        }
-
-        public override bool TryRecycle(int oldIndex, int newIndex, object item) => false;
-
-        public void UpdateIndex()
-        {
-            if (Owner is TreeView treeViewOwner && Index == null)
-            {
-                Index = new TreeContainerIndex();
-                _treeView = treeViewOwner;
-            }
-            else
-            {
-                var treeView = Owner.GetSelfAndLogicalAncestors().OfType<TreeView>().FirstOrDefault();
-                
-                if (treeView != _treeView)
-                {
-                    Clear();
-                    Index = treeView?.ItemContainerGenerator?.Index;
-                    _treeView = treeView;
-                }
-            }
-        }
-
-        class WrapperTreeDataTemplate : ITreeDataTemplate
-        {
-            private readonly IDataTemplate _inner;
-            public WrapperTreeDataTemplate(IDataTemplate inner) => _inner = inner;
-            public Control? Build(object? param) => _inner.Build(param);
-            public bool Match(object? data) => _inner.Match(data);
-            public InstancedBinding? ItemsSelector(object item) => null;
-        }
-
-        private ITreeDataTemplate GetTreeDataTemplate(object item, IDataTemplate? primary)
-        {
-            var template = Owner.FindDataTemplate(item, primary) ?? FuncDataTemplate.Default;
-            var treeTemplate = template as ITreeDataTemplate ?? new WrapperTreeDataTemplate(template);
-            return treeTemplate;
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index e51296cdecf..c4356e29675 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -3,8 +3,8 @@
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Linq;
-using Avalonia.Collections;
 using Avalonia.Automation.Peers;
+using Avalonia.Collections;
 using Avalonia.Controls.Generators;
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Presenters;
@@ -15,7 +15,6 @@
 using Avalonia.Input;
 using Avalonia.LogicalTree;
 using Avalonia.Metadata;
-using Avalonia.VisualTree;
 using Avalonia.Styling;
 
 namespace Avalonia.Controls
@@ -81,7 +80,7 @@ public IBinding? DisplayMemberBinding
         
         private IEnumerable? _items = new AvaloniaList<object>();
         private int _itemCount;
-        private IItemContainerGenerator? _itemContainerGenerator;
+        private ItemContainerGenerator? _itemContainerGenerator;
         private EventHandler<ChildIndexChangedEventArgs>? _childIndexChanged;
 
         /// <summary>
@@ -103,27 +102,9 @@ public ItemsControl()
         }
 
         /// <summary>
-        /// Gets the <see cref="IItemContainerGenerator"/> for the control.
+        /// Gets the <see cref="ItemContainerGenerator"/> for the control.
         /// </summary>
-        public IItemContainerGenerator ItemContainerGenerator
-        {
-            get
-            {
-                if (_itemContainerGenerator == null)
-                {
-                    _itemContainerGenerator = CreateItemContainerGenerator();
-
-                    _itemContainerGenerator.ItemContainerTheme = ItemContainerTheme;
-                    _itemContainerGenerator.ItemTemplate = ItemTemplate;
-                    _itemContainerGenerator.DisplayMemberBinding = DisplayMemberBinding;
-                    _itemContainerGenerator.Materialized += (_, e) => OnContainersMaterialized(e);
-                    _itemContainerGenerator.Dematerialized += (_, e) => OnContainersDematerialized(e);
-                    _itemContainerGenerator.Recycled += (_, e) => OnContainersRecycled(e);
-                }
-
-                return _itemContainerGenerator;
-            }
-        }
+        public ItemContainerGenerator ItemContainerGenerator => _itemContainerGenerator ??= new(this);
 
         /// <summary>
         /// Gets or sets the items to display.
@@ -174,11 +155,7 @@ public IDataTemplate? ItemTemplate
         /// <summary>
         /// Gets the items presenter control.
         /// </summary>
-        public ItemsPresenter? Presenter
-        {
-            get;
-            protected set;
-        }
+        public ItemsPresenter? Presenter { get; private set; }
 
         private protected bool WrapFocus { get; set; }
 
@@ -188,6 +165,52 @@ event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexCh
             remove => _childIndexChanged -= value;
         }
 
+        /// <summary>
+        /// Returns the container for the item at the specified index.
+        /// </summary>
+        /// <param name="index">The index of the item to retrieve.</param>
+        /// <returns>
+        /// The container for the item at the specified index within the item collection, if the
+        /// item has a container; otherwise, null.
+        /// </returns>
+        public Control? ContainerFromIndex(int index) => Presenter?.ContainerFromIndex(index);
+
+        /// <summary>
+        /// Returns the container corresponding to the specified item.
+        /// </summary>
+        /// <param name="item">The item to retrieve the container for.</param>
+        /// <returns>
+        /// A container that corresponds to the specified item, if the item has a container and
+        /// exists in the collection; otherwise, null.
+        /// </returns>
+        public Control? ContainerFromItem(object item)
+        {
+            throw new NotImplementedException();
+        }
+
+        /// <summary>
+        /// Returns the index to the item that has the specified, generated container.
+        /// </summary>
+        /// <param name="container">The generated container to retrieve the item index for.</param>
+        /// <returns>
+        /// The index to the item that corresponds to the specified generated container, or -1 if 
+        /// <paramref name="container"/> is not found.
+        /// </returns>
+        public int IndexFromContainer(Control container) => Presenter?.IndexFromContainer(container) ?? -1;
+
+        /// <summary>
+        /// Returns the item that corresponds to the specified, generated container.
+        /// </summary>
+        /// <param name="container">The control that corresponds to the item to be returned.</param>
+        /// <returns>
+        /// The contained item, or the container if it does not contain an item.
+        /// </returns>
+        public object? ItemFromContainer(Control container)
+        {
+            // TODO: Should this throw or return null of container isn't a container?
+            throw new NotImplementedException();
+        }
+
         /// <inheritdoc/>
         void IItemsPresenterHost.RegisterItemsPresenter(ItemsPresenter presenter)
         {
@@ -197,7 +220,7 @@ void IItemsPresenterHost.RegisterItemsPresenter(ItemsPresenter presenter)
             }
 
             Presenter = presenter;
-            ItemContainerGenerator?.Clear();
+            ////ItemContainerGenerator?.Clear();
 
             if (Presenter is IChildIndexProvider innerProvider)
             {
@@ -237,6 +260,47 @@ void ICollectionChangedListener.PostChanged(INotifyCollectionChanged sender, Not
             }
         }
 
+        /// <summary>
+        /// Creates or a container that can be used to display an item.
+        /// </summary>
+        protected internal virtual Control CreateContainerOverride() => new ContentPresenter();
+
+        /// <summary>
+        /// Prepares the specified element to display the specified item.
+        /// </summary>
+        /// <param name="container">The element that's used to display the specified item.</param>
+        /// <param name="item">The item to display.</param>
+        /// <param name="index">The index of the item to display.</param>
+        protected internal virtual void PrepareContainerForItemOverride(Control container, object? item, int index)
+        {
+            if (container == item)
+                return;
+
+            if (container is ContentControl cc)
+            {
+                cc.SetValue(ContentControl.ContentProperty, item, BindingPriority.Template);
+                if (ItemTemplate is { } it)
+                    cc.SetValue(ContentControl.ContentTemplateProperty, it, BindingPriority.Template);
+            }
+            else if (container is ContentPresenter p)
+            {
+                p.SetValue(ContentPresenter.ContentProperty, item, BindingPriority.Template);
+                if (ItemTemplate is { } it)
+                    p.SetValue(ContentPresenter.ContentTemplateProperty, it, BindingPriority.Template);
+            }
+
+            if (ItemContainerTheme is not null)
+                container.SetValue(ThemeProperty, ItemContainerTheme, BindingPriority.Template);
+        }
+
+        /// <summary>
+        /// Undoes the effects of the <see cref="PrepareContainerForItemOverride(Control, object?, int)"/> method.
+        /// </summary>
+        /// <param name="container">The container element.</param>
+        protected internal virtual void ClearContainerForItemOverride(Control container)
+        {
+        }
+
         /// <summary>
         /// Gets the index of an item in a collection.
         /// </summary>
@@ -273,60 +337,11 @@ protected static int IndexOf(IEnumerable? items, object item)
         }
 
         /// <summary>
-        /// Creates the <see cref="ItemContainerGenerator"/> for the control.
+        /// Determines whether the specified item is (or is eligible to be) its own container.
         /// </summary>
-        /// <returns>
-        /// An <see cref="IItemContainerGenerator"/>.
-        /// </returns>
-        protected virtual IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new ItemContainerGenerator(this);
-        }
-
-        /// <summary>
-        /// Called when new containers are materialized for the <see cref="ItemsControl"/> by its
-        /// <see cref="ItemContainerGenerator"/>.
-        /// </summary>
-        /// <param name="e">The details of the containers.</param>
-        protected virtual void OnContainersMaterialized(ItemContainerEventArgs e)
-        {
-            foreach (var container in e.Containers)
-            {
-                // If the item is its own container, then it will be added to the logical tree when
-                // it was added to the Items collection.
-                if (container.ContainerControl != null && container.ContainerControl != container.Item)
-                {
-                    LogicalChildren.Add(container.ContainerControl);
-                }
-            }
-        }
-
-        /// <summary>
-        /// Called when containers are dematerialized for the <see cref="ItemsControl"/> by its
-        /// <see cref="ItemContainerGenerator"/>.
-        /// </summary>
-        /// <param name="e">The details of the containers.</param>
-        protected virtual void OnContainersDematerialized(ItemContainerEventArgs e)
-        {
-            foreach (var container in e.Containers)
-            {
-                // If the item is its own container, then it will be removed from the logical tree
-                // when it is removed from the Items collection.
-                if (container.ContainerControl != container.Item)
-                {
-                    LogicalChildren.Remove(container.ContainerControl);
-                }
-            }
-        }
-
-        /// <summary>
-        /// Called when containers are recycled for the <see cref="ItemsControl"/> by its
-        /// <see cref="ItemContainerGenerator"/>.
-        /// </summary>
-        /// <param name="e">The details of the containers.</param>
-        protected virtual void OnContainersRecycled(ItemContainerEventArgs e)
-        {
-        }
+        /// <param name="item">The item to check.</param>
+        /// <returns>true if the item is (or is eligible to be) its own container; otherwise, false.</returns>
+        protected internal virtual bool IsItemItsOwnContainerOverride(Control item) => true;
 
         /// <summary>
         /// Handles directional navigation within the <see cref="ItemsControl"/>.
@@ -387,7 +402,8 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
             }
             else if (change.Property == ItemContainerThemeProperty && _itemContainerGenerator is not null)
             {
-                _itemContainerGenerator.ItemContainerTheme = change.GetNewValue<ControlTheme?>();
+                throw new NotImplementedException();
+                ////_itemContainerGenerator.ItemContainerTheme = change.GetNewValue<ControlTheme?>();
             }
         }
 
@@ -433,6 +449,27 @@ protected virtual void ItemsCollectionChanged(object sender, NotifyCollectionCha
             }
         }
 
+        internal void AddLogicalChild(Control c) => LogicalChildren.Add(c);
+        internal void RemoveLogicalChild(Control c) => LogicalChildren.Remove(c);
+        internal void ClearLogicalChildren() => LogicalChildren.Clear();
+
+        internal void PrepareItemContainer(Control container, object? item, int index)
+        {
+            var itemContainerTheme = ItemContainerTheme;
+
+            if (itemContainerTheme is not null && 
+                !container.IsSet(ThemeProperty) &&
+                ((IStyleable)container).StyleKey == itemContainerTheme.TargetType)
+            {
+                container.Theme = itemContainerTheme;
+            }
+
+            if (item is not Control)
+                container.DataContext = item;
+
+            PrepareContainerForItemOverride(container, item, index);
+        }
+
         /// <summary>
         /// Given a collection of items, adds those that are controls to the logical children.
         /// </summary>
@@ -501,7 +538,7 @@ private void ItemTemplateChanged(AvaloniaPropertyChangedEventArgs e)
         {
             if (_itemContainerGenerator != null)
             {
-                _itemContainerGenerator.ItemTemplate = (IDataTemplate?)e.NewValue;
+                ////_itemContainerGenerator.ItemTemplate = (IDataTemplate?)e.NewValue;
                 // TODO: Rebuild the item containers.
             }
         }
diff --git a/src/Avalonia.Controls/ListBox.cs b/src/Avalonia.Controls/ListBox.cs
index a8a926691a8..78a2d5d9906 100644
--- a/src/Avalonia.Controls/ListBox.cs
+++ b/src/Avalonia.Controls/ListBox.cs
@@ -103,14 +103,7 @@ public IScrollable? Scroll
         /// </summary>
         public void UnselectAll() => Selection.Clear();
 
-        /// <inheritdoc/>
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new ItemContainerGenerator<ListBoxItem>(
-                this, 
-                ListBoxItem.ContentProperty,
-                ListBoxItem.ContentTemplateProperty);
-        }
+        protected internal override Control CreateContainerOverride() => new ListBoxItem();
 
         /// <inheritdoc/>
         protected override void OnGotFocus(GotFocusEventArgs e)
diff --git a/src/Avalonia.Controls/MenuBase.cs b/src/Avalonia.Controls/MenuBase.cs
index bd7a2749c51..3b211d4cc73 100644
--- a/src/Avalonia.Controls/MenuBase.cs
+++ b/src/Avalonia.Controls/MenuBase.cs
@@ -99,9 +99,10 @@ IEnumerable<IMenuItem> IMenuElement.SubItems
         {
             get
             {
-                return ItemContainerGenerator.Containers
-                    .Select(x => x.ContainerControl)
-                    .OfType<IMenuItem>();
+                throw new NotImplementedException();
+                ////return ItemContainerGenerator.Containers
+                ////    .Select(x => x.ContainerControl)
+                ////    .OfType<IMenuItem>();
             }
         }
 
@@ -141,12 +142,6 @@ public event EventHandler<RoutedEventArgs>? MenuClosed
         /// <inheritdoc/>
         bool IMenuElement.MoveSelection(NavigationDirection direction, bool wrap) => MoveSelection(direction, wrap);
 
-        /// <inheritdoc/>
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new ItemContainerGenerator<MenuItem>(this, MenuItem.HeaderProperty, null);
-        }
-
         /// <inheritdoc/>
         protected override void OnKeyDown(KeyEventArgs e)
         {
diff --git a/src/Avalonia.Controls/MenuItem.cs b/src/Avalonia.Controls/MenuItem.cs
index 3e00cea4306..d134704b26a 100644
--- a/src/Avalonia.Controls/MenuItem.cs
+++ b/src/Avalonia.Controls/MenuItem.cs
@@ -332,9 +332,10 @@ IEnumerable<IMenuItem> IMenuElement.SubItems
         {
             get
             {
-                return ItemContainerGenerator.Containers
-                    .Select(x => x.ContainerControl)
-                    .OfType<IMenuItem>();
+                throw new NotImplementedException();
+                ////return ItemContainerGenerator.Containers
+                ////    .Select(x => x.ContainerControl)
+                ////    .OfType<IMenuItem>();
             }
         }
 
@@ -357,12 +358,6 @@ IEnumerable<IMenuItem> IMenuElement.SubItems
         /// <inheritdoc/>
         void IMenuItem.RaiseClick() => RaiseEvent(new RoutedEventArgs(ClickEvent));
 
-        /// <inheritdoc/>
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new MenuItemContainerGenerator(this);
-        }
-
         protected override void OnPointerReleased(PointerReleasedEventArgs e)
         {
             base.OnPointerReleased(e);
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
index b731f48d9c7..5f90c264d7f 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
@@ -1,3 +1,4 @@
+using System;
 using System.Diagnostics;
 
 namespace Avalonia.Controls.Presenters
@@ -13,7 +14,7 @@ public class ItemsPresenter : Control
         public static readonly StyledProperty<ITemplate<Panel>> ItemsPanelProperty =
             ItemsControl.ItemsPanelProperty.AddOwner<ItemsPresenter>();
 
-        private ItemsPresenterContainerGenerator? _generator;
+        private PanelContainerGenerator? _generator;
 
         /// <summary>
         /// Gets or sets a template which creates the <see cref="Panel"/> used to display the items.
@@ -52,7 +53,10 @@ public override sealed void ApplyTemplate()
 
         internal void ScrollIntoView(int index)
         {
-
+            if (Panel is VirtualizingPanel v)
+                v.ScrollIntoView(index);
+            else if (index >= 0 && index < Panel?.Children.Count)
+                Panel.Children[index].BringIntoView();
         }
 
         protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
@@ -97,5 +101,20 @@ private void CreateSimplePanelGenerator()
             _generator?.Dispose();
             _generator = new(this);
         }
+
+        internal Control? ContainerFromIndex(int index)
+        {
+            if (Panel is VirtualizingPanel v)
+                return v.ContainerFromIndex(index);
+            return index >= 0 && index < Panel?.Children.Count ? Panel.Children[index] : null;
+        }
+
+        internal int IndexFromContainer(Control container)
+        {
+            if (Panel is VirtualizingPanel v)
+                return v.IndexFromContainer(container);
+            return Panel?.Children.IndexOf(container) ?? -1;
+        }
+
     }
 }
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
similarity index 66%
rename from src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs
rename to src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index 233635a414e..f1765ba9862 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -9,11 +9,11 @@ namespace Avalonia.Controls.Presenters
     /// <summary>
     /// Generates containers for <see cref="ItemsPresenter"/>s that have non-virtualizing panels.
     /// </summary>
-    internal class ItemsPresenterContainerGenerator : IDisposable
+    internal class PanelContainerGenerator : IDisposable
     {
         private readonly ItemsPresenter _presenter;
 
-        public ItemsPresenterContainerGenerator(ItemsPresenter presenter)
+        public PanelContainerGenerator(ItemsPresenter presenter)
         {
             Debug.Assert(presenter.ItemsControl is not null);
             Debug.Assert(presenter.Panel is not null or VirtualizingPanel);
@@ -29,12 +29,17 @@ public ItemsPresenterContainerGenerator(ItemsPresenter presenter)
 
         public void Dispose()
         {
-            _presenter.ItemsControl!.PropertyChanged -= OnItemsControlPropertyChanged;
+            if (_presenter.ItemsControl is { } itemsControl)
+            {
+                itemsControl.PropertyChanged -= OnItemsControlPropertyChanged;
 
-            if (_presenter.ItemsControl.Items is INotifyCollectionChanged incc)
-                incc.CollectionChanged -= OnItemsChanged;
+                if (itemsControl.Items is INotifyCollectionChanged incc)
+                    incc.CollectionChanged -= OnItemsChanged;
 
-            _presenter.Panel!.Children.Clear();
+                itemsControl.ClearLogicalChildren();
+            }
+
+            _presenter.Panel?.Children.Clear();
         }
 
         private void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
@@ -51,58 +56,68 @@ private void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChang
 
         private void OnItemsChanged(object? sender, NotifyCollectionChangedEventArgs e)
         {
-            if (_presenter.ItemsControl?.Items is null || _presenter.Panel is null)
+            if (_presenter.Panel is null || _presenter.ItemsControl is null)
                 return;
 
-            var generator = _presenter.ItemsControl.ItemContainerGenerator;
+            var itemsControl = _presenter.ItemsControl;
             var panel = _presenter.Panel;
 
             void Add(int index, IEnumerable items)
             {
                 var i = index;
-
                 foreach (var item in items)
-                {
-                    var c = generator.Materialize(i, item);
-                    panel.Children.Insert(i++, c.ContainerControl);
-                }
+                    panel.Children.Insert(i++, CreateContainer(itemsControl, item, i));
             }
             
             void Remove(int index, int count)
             {
                 for (var i = 0; i < count; ++i)
+                {
+                    itemsControl.RemoveLogicalChild(panel.Children[i + index]);
                     panel.Children.RemoveAt(i + index);
+                }
             }
 
             switch (e.Action)
             {
                 case NotifyCollectionChangedAction.Add:
-                    generator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
                     Add(e.NewStartingIndex, e.NewItems!);
                     break;
                 case NotifyCollectionChangedAction.Remove:
-                    generator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
                     Remove(e.OldStartingIndex, e.OldItems!.Count);
                     break;
                 case NotifyCollectionChangedAction.Replace:
-                    generator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
                     Remove(e.OldStartingIndex, e.OldItems!.Count);
-                    generator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
                     Add(e.NewStartingIndex, e.NewItems!);
                     break;
                 case NotifyCollectionChangedAction.Move:
-                    generator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
                     Remove(e.OldStartingIndex, e.OldItems!.Count);
-                    generator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
                     Add(e.NewStartingIndex, e.NewItems!);
                     break;
                 case NotifyCollectionChangedAction.Reset:
-                    generator.Clear();
+                    itemsControl.ClearLogicalChildren();
                     panel.Children.Clear();
-                    if (_presenter.ItemsControl.Items is { } items)
+                    if (_presenter.ItemsControl?.Items is { } items)
                         Add(0, items);
                     break;
             }
         }
+
+        private static Control CreateContainer(ItemsControl itemsControl, object? item, int index)
+        {
+            var generator = itemsControl.ItemContainerGenerator;
+
+            if (item is Control c && generator.IsItemItsOwnContainer(c))
+            {
+                return c;
+            }
+            else
+            {
+                c = generator.CreateContainer();
+                itemsControl.AddLogicalChild(c);
+                generator.PrepareItemContainer(c, item, index);
+                return c;
+            }
+        }
     }
 }
diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index 44fa78ac211..1503da1322e 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -4,6 +4,7 @@
 using System.Collections.Specialized;
 using System.ComponentModel;
 using System.Linq;
+using System.Xml.Linq;
 using Avalonia.Controls.Generators;
 using Avalonia.Controls.Selection;
 using Avalonia.Data;
@@ -391,7 +392,7 @@ public override void EndInit()
             for (var current = eventSource as Visual; current != null; current = current.VisualParent)
             {
                 if (current is Control control && control.Parent == this &&
-                    ItemContainerGenerator?.IndexFromContainer(control) != -1)
+                    IndexFromContainer(control) != -1)
                 {
                     return control;
                 }
@@ -432,54 +433,34 @@ void ExecuteScrollWhenLayoutUpdated(object? sender, EventArgs e)
             }
         }
 
-        /// <inheritdoc/>
-        protected override void OnContainersMaterialized(ItemContainerEventArgs e)
+        protected internal override void PrepareContainerForItemOverride(Control element, object? item, int index)
         {
-            base.OnContainersMaterialized(e);
+            base.PrepareContainerForItemOverride(element, item, index);
 
-            foreach (var container in e.Containers)
+            if ((element as ISelectable)?.IsSelected == true)
             {
-                if ((container.ContainerControl as ISelectable)?.IsSelected == true)
-                {
-                    Selection.Select(container.Index);
-                    MarkContainerSelected(container.ContainerControl, true);
-                }
-                else
-                {
-                    var selected = Selection.IsSelected(container.Index);
-                    MarkContainerSelected(container.ContainerControl, selected);
-                }
+                Selection.Select(index);
+                MarkContainerSelected(element, true);
             }
-        }
-
-        /// <inheritdoc/>
-        protected override void OnContainersDematerialized(ItemContainerEventArgs e)
-        {
-            base.OnContainersDematerialized(e);
-
-            if (Presenter?.Panel is InputElement panel)
+            else
             {
-                foreach (var container in e.Containers)
-                {
-                    if (KeyboardNavigation.GetTabOnceActiveElement(panel) == container.ContainerControl)
-                    {
-                        KeyboardNavigation.SetTabOnceActiveElement(panel, null);
-                        break;
-                    }
-                }
+                var selected = Selection.IsSelected(index);
+                MarkContainerSelected(element, selected);
             }
         }
 
-        protected override void OnContainersRecycled(ItemContainerEventArgs e)
+        protected internal override void ClearContainerForItemOverride(Control element)
         {
-            foreach (var i in e.Containers)
+            base.ClearContainerForItemOverride(element);
+
+            if (Presenter?.Panel is InputElement panel && 
+                KeyboardNavigation.GetTabOnceActiveElement(panel) == element)
             {
-                if (i.ContainerControl != null && i.Item != null)
-                {
-                    bool selected = Selection.IsSelected(i.Index);
-                    MarkContainerSelected(i.ContainerControl, selected);
-                }
+                KeyboardNavigation.SetTabOnceActiveElement(panel, null);
             }
+
+            if (element is ISelectable selectable)
+                MarkContainerSelected(element, false);
         }
 
         /// <inheritdoc/>
@@ -526,44 +507,45 @@ protected override void OnInitialized()
 
         protected override void OnTextInput(TextInputEventArgs e)
         {
-            if (!e.Handled)
-            {
-                if (!IsTextSearchEnabled)
-                    return;
-
-                StopTextSearchTimer();
-
-                _textSearchTerm += e.Text;
-
-                bool Match(ItemContainerInfo info)
-                {
-                    if (info.ContainerControl is AvaloniaObject ao && ao.IsSet(TextSearch.TextProperty))
-                    {
-                        var searchText = ao.GetValue(TextSearch.TextProperty);
-
-                        if (searchText?.StartsWith(_textSearchTerm, StringComparison.OrdinalIgnoreCase) == true)
-                        {
-                            return true;
-                        }
-                    }
-
-                    return info.ContainerControl is IContentControl control &&
-                           control.Content?.ToString()?.StartsWith(_textSearchTerm, StringComparison.OrdinalIgnoreCase) == true;
-                }
+            throw new NotImplementedException();
+            ////if (!e.Handled)
+            ////{
+            ////    if (!IsTextSearchEnabled)
+            ////        return;
+
+            ////    StopTextSearchTimer();
+
+            ////    _textSearchTerm += e.Text;
+
+            ////    bool Match(ItemContainerInfo info)
+            ////    {
+            ////        if (info.ContainerControl is AvaloniaObject ao && ao.IsSet(TextSearch.TextProperty))
+            ////        {
+            ////            var searchText = ao.GetValue(TextSearch.TextProperty);
+
+            ////            if (searchText?.StartsWith(_textSearchTerm, StringComparison.OrdinalIgnoreCase) == true)
+            ////            {
+            ////                return true;
+            ////            }
+            ////        }
+
+            ////        return info.ContainerControl is IContentControl control &&
+            ////               control.Content?.ToString()?.StartsWith(_textSearchTerm, StringComparison.OrdinalIgnoreCase) == true;
+            ////    }
                 
-                var info = ItemContainerGenerator?.Containers.FirstOrDefault(Match);
+            ////    var info = ItemContainerGenerator?.Containers.FirstOrDefault(Match);
 
-                if (info != null)
-                {
-                    SelectedIndex = info.Index;
-                }
+            ////    if (info != null)
+            ////    {
+            ////        SelectedIndex = info.Index;
+            ////    }
 
-                StartTextSearchTimer();
+            ////    StartTextSearchTimer();
 
-                e.Handled = true;
-            }
+            ////    e.Handled = true;
+            ////}
 
-            base.OnTextInput(e);
+            ////base.OnTextInput(e);
         }
 
         protected override void OnKeyDown(KeyEventArgs e)
@@ -634,7 +616,7 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
         /// <returns>True if the selection was moved; otherwise false.</returns>
         protected bool MoveSelection(NavigationDirection direction, bool wrap)
         {
-            var from = SelectedIndex != -1 ? ItemContainerGenerator?.ContainerFromIndex(SelectedIndex) : null;
+            var from = SelectedIndex != -1 ? ContainerFromIndex(SelectedIndex) : null;
             return MoveSelection(from, direction, wrap);
         }
 
@@ -650,7 +632,7 @@ protected bool MoveSelection(Control? from, NavigationDirection direction, bool
             if (Presenter?.Panel is INavigableContainer container &&
                 GetNextControl(container, direction, from, wrap) is Control next)
             {
-                var index = ItemContainerGenerator?.IndexFromContainer(next) ?? -1;
+                var index = IndexFromContainer(next);
 
                 if (index != -1)
                 {
@@ -733,7 +715,7 @@ protected void UpdateSelection(
 
             if (Presenter?.Panel != null)
             {
-                var container = ItemContainerGenerator?.ContainerFromIndex(index);
+                var container = ContainerFromIndex(index);
                 KeyboardNavigation.SetTabOnceActiveElement(
                     (InputElement)Presenter.Panel,
                     container);
@@ -757,7 +739,7 @@ protected void UpdateSelection(
             bool rightButton = false,
             bool fromFocus = false)
         {
-            var index = ItemContainerGenerator?.IndexFromContainer(container) ?? -1;
+            var index = IndexFromContainer(container);
 
             if (index != -1)
             {
@@ -842,7 +824,7 @@ private void OnSelectionModelSelectionChanged(object? sender, SelectionModelSele
         {
             void Mark(int index, bool selected)
             {
-                var container = ItemContainerGenerator?.ContainerFromIndex(index);
+                var container = ContainerFromIndex(index);
 
                 if (container != null)
                 {
@@ -909,7 +891,7 @@ private void ContainerSelectionChanged(RoutedEventArgs e)
                 e.Source is Control control &&
                 e.Source is ISelectable selectable &&
                 control.Parent == this &&
-                ItemContainerGenerator?.IndexFromContainer(control) != -1)
+                IndexFromContainer(control) != -1)
             {
                 UpdateSelection(control, selectable.IsSelected);
             }
@@ -961,7 +943,7 @@ private void UpdateContainerSelection()
                 {
                     MarkContainerSelected(
                         container,
-                        Selection.IsSelected(ItemContainerGenerator.IndexFromContainer(container)));
+                        Selection.IsSelected(IndexFromContainer(container)));
                 }
             }
         }
diff --git a/src/Avalonia.Controls/Primitives/TabStrip.cs b/src/Avalonia.Controls/Primitives/TabStrip.cs
index d27b1faaed7..a6a6f4cec81 100644
--- a/src/Avalonia.Controls/Primitives/TabStrip.cs
+++ b/src/Avalonia.Controls/Primitives/TabStrip.cs
@@ -18,14 +18,6 @@ static TabStrip()
             ItemsPanelProperty.OverrideDefaultValue<TabStrip>(DefaultPanel);
         }
 
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new ItemContainerGenerator<TabStripItem>(
-                this,
-                ContentControl.ContentProperty,
-                ContentControl.ContentTemplateProperty);
-        }
-
         /// <inheritdoc/>
         protected override void OnGotFocus(GotFocusEventArgs e)
         {
diff --git a/src/Avalonia.Controls/TabControl.cs b/src/Avalonia.Controls/TabControl.cs
index 2e7059b8384..8ce1befde55 100644
--- a/src/Avalonia.Controls/TabControl.cs
+++ b/src/Avalonia.Controls/TabControl.cs
@@ -165,15 +165,15 @@ bool IContentPresenterHost.RegisterContentPresenter(IContentPresenter presenter)
             return RegisterContentPresenter(presenter);
         }
 
-        protected override void OnContainersMaterialized(ItemContainerEventArgs e)
+        protected internal override void PrepareContainerForItemOverride(Control element, object? item, int index)
         {
-            base.OnContainersMaterialized(e);
+            base.PrepareContainerForItemOverride(element, item, index);
             UpdateSelectedContent();
         }
 
-        protected override void OnContainersRecycled(ItemContainerEventArgs e)
+        protected internal override void ClearContainerForItemOverride(Control element)
         {
-            base.OnContainersRecycled(e);
+            base.ClearContainerForItemOverride(element);
             UpdateSelectedContent();
         }
 
@@ -207,11 +207,6 @@ protected virtual bool RegisterContentPresenter(IContentPresenter presenter)
             return false;
         }
 
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new TabItemContainerGenerator(this);
-        }
-
         protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
         {
             ItemsPresenterPart = e.NameScope.Get<ItemsPresenter>("PART_ItemsPresenter");
diff --git a/src/Avalonia.Controls/TreeView.cs b/src/Avalonia.Controls/TreeView.cs
index 2fa4a02fa21..6336219fb63 100644
--- a/src/Avalonia.Controls/TreeView.cs
+++ b/src/Avalonia.Controls/TreeView.cs
@@ -75,12 +75,6 @@ public event EventHandler<SelectionChangedEventArgs>? SelectionChanged
             remove => RemoveHandler(SelectingItemsControl.SelectionChangedEvent, value);
         }
 
-        /// <summary>
-        /// Gets the <see cref="ITreeItemContainerGenerator"/> for the tree view.
-        /// </summary>
-        public new ITreeItemContainerGenerator ItemContainerGenerator =>
-            (ITreeItemContainerGenerator)base.ItemContainerGenerator;
-
         /// <summary>
         /// Gets or sets a value indicating whether to automatically scroll to newly selected items.
         /// </summary>
@@ -188,7 +182,8 @@ public void ExpandSubTree(TreeViewItem item)
         /// </remarks>
         public void SelectAll()
         {
-            SynchronizeItems(SelectedItems, ItemContainerGenerator.Index!.Items);
+            throw new NotImplementedException();
+            ////SynchronizeItems(SelectedItems, ItemContainerGenerator.Index!.Items);
         }
 
         /// <summary>
@@ -242,7 +237,7 @@ private void SelectedItemsCollectionChanged(object? sender, NotifyCollectionChan
 
                     if (AutoScrollToSelectedItem)
                     {
-                        var container = ItemContainerGenerator.Index!.ContainerFromItem(e.NewItems![0]!);
+                        var container = ContainerFromItem(e.NewItems![0]!);
 
                         container?.BringIntoView();
                     }
@@ -282,9 +277,10 @@ private void SelectedItemsCollectionChanged(object? sender, NotifyCollectionChan
                     break;
                 case NotifyCollectionChangedAction.Reset:
 
-                    foreach (Control container in ItemContainerGenerator.Index!.Containers)
+                    foreach (var child in LogicalChildren)
                     {
-                        MarkContainerSelected(container, false);
+                        if (child is Control container && IndexFromContainer(container) != -1)
+                            MarkContainerSelected(container, false);
                     }
 
                     if (SelectedItems.Count > 0)
@@ -337,7 +333,7 @@ private void SelectedItemsCollectionChanged(object? sender, NotifyCollectionChan
 
         private void MarkItemSelected(object item, bool selected)
         {
-            var container = ItemContainerGenerator.Index!.ContainerFromItem(item)!;
+            var container = ContainerFromItem(item)!;
 
             MarkContainerSelected(container, selected);
         }
@@ -378,8 +374,8 @@ private void UnsubscribeFromSelectedItems()
                 if (!this.IsVisualAncestorOf((Visual)element))
                 {
                     var result = _selectedItem != null ?
-                        ItemContainerGenerator.Index!.ContainerFromItem(_selectedItem) :
-                        ItemContainerGenerator.ContainerFromIndex(0);
+                        ContainerFromItem(_selectedItem) :
+                        ContainerFromIndex(0);
                     
                     return (result != null, result); // SelectedItem may not be in the treeview.
                 }
@@ -390,27 +386,6 @@ private void UnsubscribeFromSelectedItems()
             return (false, null);
         }
 
-        /// <inheritdoc/>
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            var result = CreateTreeItemContainerGenerator();
-            result.Index!.Materialized += ContainerMaterialized;
-            return result;
-        }
-
-        protected virtual ITreeItemContainerGenerator CreateTreeItemContainerGenerator() =>
-            CreateTreeItemContainerGenerator<TreeViewItem>();
-
-        protected ITreeItemContainerGenerator CreateTreeItemContainerGenerator<TVItem>() where TVItem: TreeViewItem, new()
-        {
-            return new TreeItemContainerGenerator<TVItem>(
-                this,
-                TreeViewItem.HeaderProperty,
-                TreeViewItem.ItemTemplateProperty,
-                TreeViewItem.ItemsProperty,
-                TreeViewItem.IsExpandedProperty);
-        }
-
         /// <inheritdoc/>
         protected override void OnGotFocus(GotFocusEventArgs e)
         {
@@ -466,53 +441,54 @@ protected override void OnKeyDown(KeyEventArgs e)
             NavigationDirection direction,
             bool intoChildren)
         {
-            IItemContainerGenerator? parentGenerator = GetParentContainerGenerator(from);
-
-            if (parentGenerator == null)
-            {
-                return null;
-            }
-
-            var index = from is not null ? parentGenerator.IndexFromContainer(from) : -1;
-            var parent = from?.Parent as ItemsControl;
-            TreeViewItem? result = null;
-
-            switch (direction)
-            {
-                case NavigationDirection.Up:
-                    if (index > 0)
-                    {
-                        var previous = (TreeViewItem)parentGenerator.ContainerFromIndex(index - 1)!;
-                        result = previous.IsExpanded && previous.ItemCount > 0 ?
-                            (TreeViewItem)previous.ItemContainerGenerator.ContainerFromIndex(previous.ItemCount - 1)! :
-                            previous;
-                    }
-                    else
-                    {
-                        result = from?.Parent as TreeViewItem;
-                    }
-
-                    break;
-
-                case NavigationDirection.Down:
-                case NavigationDirection.Right:
-                    if (from?.IsExpanded == true && intoChildren && from.ItemCount > 0)
-                    {
-                        result = (TreeViewItem)from.ItemContainerGenerator.ContainerFromIndex(0)!;
-                    }
-                    else if (index < parent?.ItemCount - 1)
-                    {
-                        result = (TreeViewItem)parentGenerator.ContainerFromIndex(index + 1)!;
-                    }
-                    else if (parent is TreeViewItem parentItem)
-                    {
-                        return GetContainerInDirection(parentItem, direction, false);
-                    }
-
-                    break;
-            }
-
-            return result;
+            throw new NotImplementedException();
+            ////IItemContainerGenerator? parentGenerator = GetParentContainerGenerator(from);
+
+            ////if (parentGenerator == null)
+            ////{
+            ////    return null;
+            ////}
+
+            ////var index = from is not null ? parentGenerator.IndexFromContainer(from) : -1;
+            ////var parent = from?.Parent as ItemsControl;
+            ////TreeViewItem? result = null;
+
+            ////switch (direction)
+            ////{
+            ////    case NavigationDirection.Up:
+            ////        if (index > 0)
+            ////        {
+            ////            var previous = (TreeViewItem)parentGenerator.ContainerFromIndex(index - 1)!;
+            ////            result = previous.IsExpanded && previous.ItemCount > 0 ?
+            ////                (TreeViewItem)previous.ItemContainerGenerator.ContainerFromIndex(previous.ItemCount - 1)! :
+            ////                previous;
+            ////        }
+            ////        else
+            ////        {
+            ////            result = from?.Parent as TreeViewItem;
+            ////        }
+
+            ////        break;
+
+            ////    case NavigationDirection.Down:
+            ////    case NavigationDirection.Right:
+            ////        if (from?.IsExpanded == true && intoChildren && from.ItemCount > 0)
+            ////        {
+            ////            result = (TreeViewItem)from.ItemContainerGenerator.ContainerFromIndex(0)!;
+            ////        }
+            ////        else if (index < parent?.ItemCount - 1)
+            ////        {
+            ////            result = (TreeViewItem)parentGenerator.ContainerFromIndex(index + 1)!;
+            ////        }
+            ////        else if (parent is TreeViewItem parentItem)
+            ////        {
+            ////            return GetContainerInDirection(parentItem, direction, false);
+            ////        }
+
+            ////        break;
+            ////}
+
+            ////return result;
         }
 
         /// <inheritdoc/>
@@ -551,80 +527,63 @@ protected void UpdateSelectionFromContainer(
             bool toggleModifier = false,
             bool rightButton = false)
         {
-            var item = ItemContainerGenerator.Index!.ItemFromContainer(container);
-
-            if (item == null)
-            {
-                return;
-            }
-
-            Control? selectedContainer = null;
-
-            if (SelectedItem != null)
-            {
-                selectedContainer = ItemContainerGenerator.Index!.ContainerFromItem(SelectedItem);
-            }
-
-            var mode = SelectionMode;
-            var toggle = toggleModifier || mode.HasAllFlags(SelectionMode.Toggle);
-            var multi = mode.HasAllFlags(SelectionMode.Multiple);
-            var range = multi && rangeModifier && selectedContainer != null;
-
-            if (rightButton)
-            {
-                if (!SelectedItems.Contains(item))
-                {
-                    SelectSingleItem(item);
-                }
-            }
-            else if (!toggle && !range)
-            {
-                SelectSingleItem(item);
-            }
-            else if (multi && range)
-            {
-                SynchronizeItems(
-                    SelectedItems,
-                    GetItemsInRange(selectedContainer as TreeViewItem, container as TreeViewItem));
-            }
-            else
-            {
-                var i = SelectedItems.IndexOf(item);
-
-                if (i != -1)
-                {
-                    SelectedItems.Remove(item);
-                }
-                else
-                {
-                    if (multi)
-                    {
-                        SelectedItems.Add(item);
-                    }
-                    else
-                    {
-                        SelectedItem = item;
-                    }
-                }
-            }
-        }
-
-        private static IItemContainerGenerator? GetParentContainerGenerator(TreeViewItem? item)
-        {
-            if (item == null)
-            {
-                return null;
-            }
-
-            switch (item.Parent)
-            {
-                case TreeView treeView:
-                    return treeView.ItemContainerGenerator;
-                case TreeViewItem treeViewItem:
-                    return treeViewItem.ItemContainerGenerator;
-                default:
-                    return null;
-            }
+            throw new NotImplementedException();
+            ////var item = ItemContainerGenerator.Index!.ItemFromContainer(container);
+
+            ////if (item == null)
+            ////{
+            ////    return;
+            ////}
+
+            ////Control? selectedContainer = null;
+
+            ////if (SelectedItem != null)
+            ////{
+            ////    selectedContainer = ItemContainerGenerator.Index!.ContainerFromItem(SelectedItem);
+            ////}
+
+            ////var mode = SelectionMode;
+            ////var toggle = toggleModifier || mode.HasAllFlags(SelectionMode.Toggle);
+            ////var multi = mode.HasAllFlags(SelectionMode.Multiple);
+            ////var range = multi && rangeModifier && selectedContainer != null;
+
+            ////if (rightButton)
+            ////{
+            ////    if (!SelectedItems.Contains(item))
+            ////    {
+            ////        SelectSingleItem(item);
+            ////    }
+            ////}
+            ////else if (!toggle && !range)
+            ////{
+            ////    SelectSingleItem(item);
+            ////}
+            ////else if (multi && range)
+            ////{
+            ////    SynchronizeItems(
+            ////        SelectedItems,
+            ////        GetItemsInRange(selectedContainer as TreeViewItem, container as TreeViewItem));
+            ////}
+            ////else
+            ////{
+            ////    var i = SelectedItems.IndexOf(item);
+
+            ////    if (i != -1)
+            ////    {
+            ////        SelectedItems.Remove(item);
+            ////    }
+            ////    else
+            ////    {
+            ////        if (multi)
+            ////        {
+            ////            SelectedItems.Add(item);
+            ////        }
+            ////        else
+            ////        {
+            ////            SelectedItem = item;
+            ////        }
+            ////    }
+            ////}
         }
 
         /// <summary>
@@ -639,23 +598,24 @@ protected void UpdateSelectionFromContainer(
             return FindInContainers(treeView.ItemContainerGenerator, nodeA, nodeB);
         }
 
-        private static TreeViewItem? FindInContainers(ITreeItemContainerGenerator containerGenerator,
+        private static TreeViewItem? FindInContainers(ItemContainerGenerator containerGenerator,
             TreeViewItem nodeA,
             TreeViewItem nodeB)
         {
-            IEnumerable<ItemContainerInfo> containers = containerGenerator.Containers;
+            throw new NotImplementedException();
+            ////IEnumerable<ItemContainerInfo> containers = containerGenerator.Containers;
 
-            foreach (ItemContainerInfo container in containers)
-            {
-                TreeViewItem? node = FindFirstNode(container.ContainerControl as TreeViewItem, nodeA, nodeB);
+            ////foreach (ItemContainerInfo container in containers)
+            ////{
+            ////    TreeViewItem? node = FindFirstNode(container.ContainerControl as TreeViewItem, nodeA, nodeB);
 
-                if (node != null)
-                {
-                    return node;
-                }
-            }
+            ////    if (node != null)
+            ////    {
+            ////        return node;
+            ////    }
+            ////}
 
-            return null;
+            ////return null;
         }
 
         private static TreeViewItem? FindFirstNode(TreeViewItem? node, TreeViewItem nodeA, TreeViewItem nodeB)
@@ -683,59 +643,60 @@ protected void UpdateSelectionFromContainer(
         /// <param name="to">To container.</param>
         private List<object> GetItemsInRange(TreeViewItem? from, TreeViewItem? to)
         {
-            var items = new List<object>();
+            throw new NotImplementedException();
+            ////var items = new List<object>();
 
-            if (from == null || to == null)
-            {
-                return items;
-            }
+            ////if (from == null || to == null)
+            ////{
+            ////    return items;
+            ////}
 
-            TreeViewItem? firstItem = FindFirstNode(this, from, to);
+            ////TreeViewItem? firstItem = FindFirstNode(this, from, to);
 
-            if (firstItem == null)
-            {
-                return items;
-            }
+            ////if (firstItem == null)
+            ////{
+            ////    return items;
+            ////}
 
-            bool wasReversed = false;
+            ////bool wasReversed = false;
 
-            if (firstItem == to)
-            {
-                var temp = from;
+            ////if (firstItem == to)
+            ////{
+            ////    var temp = from;
 
-                from = to;
-                to = temp;
+            ////    from = to;
+            ////    to = temp;
 
-                wasReversed = true;
-            }
+            ////    wasReversed = true;
+            ////}
 
-            TreeViewItem? node = from;
+            ////TreeViewItem? node = from;
 
-            while (node != to)
-            {
-                var item = ItemContainerGenerator.Index!.ItemFromContainer(node);
+            ////while (node != to)
+            ////{
+            ////    var item = ItemContainerGenerator.Index!.ItemFromContainer(node);
 
-                if (item != null)
-                {
-                    items.Add(item);
-                }
+            ////    if (item != null)
+            ////    {
+            ////        items.Add(item);
+            ////    }
 
-                node = GetContainerInDirection(node, NavigationDirection.Down, true);
-            }
+            ////    node = GetContainerInDirection(node, NavigationDirection.Down, true);
+            ////}
 
-            var toItem = ItemContainerGenerator.Index!.ItemFromContainer(to);
+            ////var toItem = ItemContainerGenerator.Index!.ItemFromContainer(to);
 
-            if (toItem != null)
-            {
-                items.Add(toItem);
-            }
+            ////if (toItem != null)
+            ////{
+            ////    items.Add(toItem);
+            ////}
 
-            if (wasReversed)
-            {
-                items.Reverse();
-            }
+            ////if (wasReversed)
+            ////{
+            ////    items.Reverse();
+            ////}
 
-            return items;
+            ////return items;
         }
 
         /// <summary>
@@ -776,19 +737,20 @@ protected bool UpdateSelectionFromEventSource(
         /// <returns>The container or null if the event did not originate in a container.</returns>
         protected TreeViewItem? GetContainerFromEventSource(object eventSource)
         {
-            var item = ((Visual)eventSource).GetSelfAndVisualAncestors()
-                .OfType<TreeViewItem>()
-                .FirstOrDefault();
+            throw new NotImplementedException();
+            ////var item = ((Visual)eventSource).GetSelfAndVisualAncestors()
+            ////    .OfType<TreeViewItem>()
+            ////    .FirstOrDefault();
 
-            if (item != null)
-            {
-                if (item.ItemContainerGenerator.Index == ItemContainerGenerator.Index)
-                {
-                    return item;
-                }
-            }
+            ////if (item != null)
+            ////{
+            ////    if (item.ItemContainerGenerator.Index == ItemContainerGenerator.Index)
+            ////    {
+            ////        return item;
+            ////    }
+            ////}
 
-            return null;
+            ////return null;
         }
 
         /// <summary>
@@ -796,30 +758,30 @@ protected bool UpdateSelectionFromEventSource(
         /// </summary>
         /// <param name="sender">The event sender.</param>
         /// <param name="e">The event args.</param>
-        private void ContainerMaterialized(object? sender, ItemContainerEventArgs e)
-        {
-            var selectedItem = SelectedItem;
-
-            if (selectedItem == null)
-            {
-                return;
-            }
-
-            foreach (var container in e.Containers)
-            {
-                if (container.Item == selectedItem)
-                {
-                    ((TreeViewItem)container.ContainerControl).IsSelected = true;
-
-                    if (AutoScrollToSelectedItem)
-                    {
-                        Dispatcher.UIThread.Post(container.ContainerControl.BringIntoView);
-                    }
-
-                    break;
-                }
-            }
-        }
+        ////private void ContainerMaterialized(object? sender, ItemContainerEventArgs e)
+        ////{
+        ////    var selectedItem = SelectedItem;
+
+        ////    if (selectedItem == null)
+        ////    {
+        ////        return;
+        ////    }
+
+        ////    foreach (var container in e.Containers)
+        ////    {
+        ////        if (container.Item == selectedItem)
+        ////        {
+        ////            ((TreeViewItem)container.ContainerControl).IsSelected = true;
+
+        ////            if (AutoScrollToSelectedItem)
+        ////            {
+        ////                Dispatcher.UIThread.Post(container.ContainerControl.BringIntoView);
+        ////            }
+
+        ////            break;
+        ////        }
+        ////    }
+        ////}
 
         /// <summary>
         /// Sets a container's 'selected' class or <see cref="ISelectable.IsSelected"/>.
diff --git a/src/Avalonia.Controls/TreeViewItem.cs b/src/Avalonia.Controls/TreeViewItem.cs
index 9bfcf5adfab..097fe54f420 100644
--- a/src/Avalonia.Controls/TreeViewItem.cs
+++ b/src/Avalonia.Controls/TreeViewItem.cs
@@ -58,7 +58,6 @@ static TreeViewItem()
             PressedMixin.Attach<TreeViewItem>();
             FocusableProperty.OverrideDefaultValue<TreeViewItem>(true);
             ItemsPanelProperty.OverrideDefaultValue<TreeViewItem>(DefaultPanel);
-            ParentProperty.Changed.AddClassHandler<TreeViewItem>((o, e) => o.OnParentChanged(e));
             RequestBringIntoViewEvent.AddClassHandler<TreeViewItem>((x, e) => x.OnRequestBringIntoView(e));
         }
 
@@ -89,27 +88,6 @@ public int Level
             private set { SetAndRaise(LevelProperty, ref _level, value); }
         }
 
-        /// <summary>
-        /// Gets the <see cref="ITreeItemContainerGenerator"/> for the tree view.
-        /// </summary>
-        public new ITreeItemContainerGenerator ItemContainerGenerator =>
-            (ITreeItemContainerGenerator)base.ItemContainerGenerator;
-
-        /// <inheritdoc/>
-        protected override IItemContainerGenerator CreateItemContainerGenerator() => CreateTreeItemContainerGenerator<TreeViewItem>();
-
-        /// <inheritdoc/>
-        protected ITreeItemContainerGenerator CreateTreeItemContainerGenerator<TVItem>()
-            where TVItem: TreeViewItem, new()
-        {
-            return new TreeItemContainerGenerator<TVItem>(
-                this,
-                TreeViewItem.HeaderProperty,
-                TreeViewItem.ItemTemplateProperty,
-                TreeViewItem.ItemsProperty,
-                TreeViewItem.IsExpandedProperty);
-        }
-
         /// <inheritdoc/>
         protected override void OnAttachedToLogicalTree(LogicalTreeAttachmentEventArgs e)
         {
@@ -118,7 +96,6 @@ protected override void OnAttachedToLogicalTree(LogicalTreeAttachmentEventArgs e
             _treeView = this.GetLogicalAncestors().OfType<TreeView>().FirstOrDefault();
             
             Level = CalculateDistanceFromLogicalParent<TreeView>(this) - 1;
-            ItemContainerGenerator.UpdateIndex();
 
             if (ItemTemplate == null && _treeView?.ItemTemplate != null)
             {
@@ -134,7 +111,6 @@ protected override void OnAttachedToLogicalTree(LogicalTreeAttachmentEventArgs e
         protected override void OnDetachedFromLogicalTree(LogicalTreeAttachmentEventArgs e)
         {
             base.OnDetachedFromLogicalTree(e);
-            ItemContainerGenerator.UpdateIndex();
         }
 
         protected virtual void OnRequestBringIntoView(RequestBringIntoViewEventArgs e)
@@ -219,16 +195,5 @@ private static int CalculateDistanceFromLogicalParent<T>(ILogical? logical, int
 
             return logical != null ? result : @default;
         }
-
-        private void OnParentChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            if (!((ILogical)this).IsAttachedToLogicalTree && e.NewValue is null)
-            {
-                // If we're not attached to the logical tree, then OnDetachedFromLogicalTree isn't going to be
-                // called when the item is removed. This results in the item not being removed from the index,
-                // causing #3551. In this case, update the index when Parent is changed to null.
-                ItemContainerGenerator.UpdateIndex();
-            }
-        }
     }
 }
diff --git a/src/Avalonia.Controls/VirtualizingPanel.cs b/src/Avalonia.Controls/VirtualizingPanel.cs
index 19b1c4002cd..dd40f868d5d 100644
--- a/src/Avalonia.Controls/VirtualizingPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingPanel.cs
@@ -1,5 +1,7 @@
-using System.Collections;
+using System;
+using System.Collections;
 using System.Collections.Specialized;
+using System.Diagnostics.CodeAnalysis;
 using Avalonia.Controls.Utils;
 
 namespace Avalonia.Controls
@@ -25,6 +27,32 @@ private set
             }
         }
 
+        /// <summary>
+        /// Scrolls the specified item into view.
+        /// </summary>
+        /// <param name="index">The index of the item.</param>
+        protected internal abstract void ScrollIntoView(int index);
+
+        /// <summary>
+        /// Returns the container for the item at the specified index.
+        /// </summary>
+        /// <param name="index">The index of the item to retrieve.</param>
+        /// <returns>
+        /// The container for the item at the specified index within the item collection, if the
+        /// item is realized; otherwise, null.
+        /// </returns>
+        protected internal abstract Control? ContainerFromIndex(int index);
+
+        /// <summary>
+        /// Returns the index to the item that has the specified realized container.
+        /// </summary>
+        /// <param name="container">The generated container to retrieve the item index for.</param>
+        /// <returns>
+        /// The index to the item that corresponds to the specified realized container, or -1 if 
+        /// <paramref name="container"/> is not found.
+        /// </returns>
+        protected internal abstract int IndexFromContainer(Control container);
+
         /// <summary>
         /// Called when the <see cref="ItemsControl"/> that owns the panel changes.
         /// </summary>
@@ -51,8 +79,59 @@ protected virtual void OnItemsChanged(IList items, NotifyCollectionChangedEventA
         {
         }
 
+        /// <summary>
+        /// Adds the specified <see cref="Control"/> to the <see cref="Panel.Children"/> collection
+        /// of a <see cref="VirtualizingPanel"/> element.
+        /// </summary>
+        /// <param name="control">The control to add to the collection.</param>
+        protected void AddInternalChild(Control control)
+        {
+            var itemsControl = EnsureItemsControl();
+            itemsControl.AddLogicalChild(control);
+            Children.Add(control);
+        }
+
+        /// <summary>
+        /// Adds the specified <see cref="Control"/> to the <see cref="Panel.Children"/> collection
+        /// of a <see cref="VirtualizingPanel"/> element at the specified index position.
+        /// </summary>
+        /// <param name="index">
+        /// The index position within the collection at which the child element is inserted.
+        /// </param>
+        /// <param name="control">The control to add to the collection.</param>
+        protected void InsertInternalChild(int index, Control control)
+        {
+            var itemsControl = EnsureItemsControl();
+            itemsControl.AddLogicalChild(control);
+            Children.Insert(index, control);
+        }
+
+        /// <summary>
+        /// Removes child elements from the <see cref="Panel.Children"/> collection.
+        /// </summary>
+        /// <param name="index">
+        /// The beginning index position within the collection at which the first child element is
+        /// removed.
+        /// </param>
+        /// <param name="count">The number of child elements to remove.</param>
+        protected void RemoveInternalChildRange(int index, int count)
+        {
+            var itemsControl = EnsureItemsControl();
+            
+            for (var i = 0; i < count; ++i)
+            {
+                var c = Children[i];
+                itemsControl.RemoveLogicalChild(c);
+            }
+
+            Children.RemoveRange(index, count);
+        }
+
         internal void Attach(ItemsControl itemsControl)
         {
+            if (ItemsControl is not null)
+                throw new InvalidOperationException("The VirtualizingPanel is already attached to an ItemsControl");
+
             ItemsControl = itemsControl;
             ItemsControl.PropertyChanged += OnItemsControlPropertyChanged;
 
@@ -62,18 +141,24 @@ internal void Attach(ItemsControl itemsControl)
 
         internal void Detach()
         {
-            if (ItemsControl is null)
-                return;
+            var itemsControl = EnsureItemsControl();
 
-            ItemsControl.PropertyChanged -= OnItemsControlPropertyChanged;
+            itemsControl.PropertyChanged -= OnItemsControlPropertyChanged;
 
-            if (ItemsControl.Items is INotifyCollectionChanged incc)
+            if (itemsControl.Items is INotifyCollectionChanged incc)
                 incc.CollectionChanged -= OnItemsControlItemsChanged;
 
             ItemsControl = null;
             Children.Clear();
         }
 
+        private ItemsControl EnsureItemsControl()
+        {
+            if (ItemsControl is null)
+                ThrowNotAttached();
+            return ItemsControl;
+        }
+
         private protected virtual void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
         {
             if (e.Property == ItemsControl.ItemsProperty)
@@ -91,5 +176,11 @@ private void OnItemsControlItemsChanged(object? sender, NotifyCollectionChangedE
             if (_itemsControl?.Items is IList items)
                 OnItemsChanged(items, e);
         }
+
+        [DoesNotReturn]
+        private static void ThrowNotAttached()
+        {
+            throw new InvalidOperationException("The VirtualizingPanel does not belong to an ItemsControl.");
+        }
     }
 }
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 5d9b3b56b16..a4e287dc087 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -3,6 +3,7 @@
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Diagnostics;
+using System.Xml.Linq;
 using Avalonia.Controls.Utils;
 using Avalonia.Layout;
 using Avalonia.Utilities;
@@ -18,16 +19,21 @@ public class VirtualizingStackPanel : VirtualizingPanel
         public static readonly StyledProperty<Orientation> OrientationProperty =
             StackLayout.OrientationProperty.AddOwner<VirtualizingStackPanel>();
 
+        private static readonly AttachedProperty<bool> ItemIsOwnContainerProperty =
+            AvaloniaProperty.RegisterAttached<VirtualizingStackPanel, Control, bool>("ItemIsOwnContainer");
+
         private static readonly Rect s_invalidViewport = new(double.PositiveInfinity, double.PositiveInfinity, 0, 0);
         private readonly Action<Control> _recycleElement;
         private readonly Action<Control, int> _updateElementIndex;
         private int _anchorIndex = -1;
         private Control? _anchorElement;
+        private bool _isInLayout;
         private bool _isWaitingForViewportUpdate;
         private double _lastEstimatedElementSizeU = 25;
         private RealizedElementList? _measureElements;
         private RealizedElementList? _realizedElements;
         private Rect _viewport = s_invalidViewport;
+        private Stack<Control>? _recyclePool;
 
         public VirtualizingStackPanel()
         {
@@ -54,73 +60,92 @@ protected override Size MeasureOverride(Size availableSize)
             if (!IsEffectivelyVisible)
                 return default;
 
-            var items = ItemsControl?.Items as IList;
+            _isInLayout = true;
 
-            if (items is null || items.Count == 0)
+            try
             {
-                Children.Clear();
-                return default;
-            }
+                var items = ItemsControl?.Items as IList;
+
+                if (items is null || items.Count == 0)
+                {
+                    RemoveInternalChildRange(0, Children.Count);
+                    return default;
+                }
 
-            var orientation = Orientation;
+                var orientation = Orientation;
 
-            _realizedElements ??= new();
-            _measureElements ??= new();
+                _realizedElements ??= new();
+                _measureElements ??= new();
 
-            // If we're bringing an item into view, ignore any layout passes until we receive a new
-            // effective viewport.
-            if (_isWaitingForViewportUpdate)
-            {
-                var sizeV = orientation == Orientation.Horizontal ? DesiredSize.Height : DesiredSize.Width;
-                return CalculateDesiredSize(orientation, items, sizeV);
-            }
+                // If we're bringing an item into view, ignore any layout passes until we receive a new
+                // effective viewport.
+                if (_isWaitingForViewportUpdate)
+                {
+                    var sizeV = orientation == Orientation.Horizontal ? DesiredSize.Height : DesiredSize.Width;
+                    return CalculateDesiredSize(orientation, items, sizeV);
+                }
 
-            // We handle horizontal and vertical layouts here so X and Y are abstracted to:
-            // - Horizontal layouts: U = horizontal, V = vertical
-            // - Vertical layouts: U = vertical, V = horizontal
-            var viewport = CalculateMeasureViewport(items);
+                // We handle horizontal and vertical layouts here so X and Y are abstracted to:
+                // - Horizontal layouts: U = horizontal, V = vertical
+                // - Vertical layouts: U = vertical, V = horizontal
+                var viewport = CalculateMeasureViewport(items);
 
-            // Recycle elements outside of the expected range.
-            _realizedElements.RecycleElementsBefore(viewport.firstIndex, _recycleElement);
-            _realizedElements.RecycleElementsAfter(viewport.estimatedLastIndex, _recycleElement);
+                // Recycle elements outside of the expected range.
+                _realizedElements.RecycleElementsBefore(viewport.firstIndex, _recycleElement);
+                _realizedElements.RecycleElementsAfter(viewport.estimatedLastIndex, _recycleElement);
 
-            // Do the measure, creating/recycling elements as necessary to fill the viewport. Don't
-            // write to _realizedElements yet, only _measureElements.
-            GenerateElements(availableSize, ref viewport);
+                // Do the measure, creating/recycling elements as necessary to fill the viewport. Don't
+                // write to _realizedElements yet, only _measureElements.
+                GenerateElements(availableSize, ref viewport);
 
-            // Now we know what definitely fits, recycle anything left over.
-            _realizedElements.RecycleElementsAfter(_measureElements.LastModelIndex, _recycleElement);
+                // Now we know what definitely fits, recycle anything left over.
+                _realizedElements.RecycleElementsAfter(_measureElements.LastModelIndex, _recycleElement);
 
-            // And swap the measureElements and realizedElements collection.
-            (_measureElements, _realizedElements) = (_realizedElements, _measureElements);
-            _measureElements.ResetForReuse();
+                // And swap the measureElements and realizedElements collection.
+                (_measureElements, _realizedElements) = (_realizedElements, _measureElements);
+                _measureElements.ResetForReuse();
 
-            return CalculateDesiredSize(orientation, items, viewport.measuredV);
+                return CalculateDesiredSize(orientation, items, viewport.measuredV);
+            }
+            finally
+            {
+                _isInLayout = false;
+            }
         }
 
         protected override Size ArrangeOverride(Size finalSize)
         {
-            Debug.Assert(_realizedElements is not null);
+            if (_realizedElements is null)
+                return default;
 
-            var orientation = Orientation;
-            var u = _realizedElements!.StartU;
+            _isInLayout = true;
 
-            for (var i = 0; i < _realizedElements.Count; ++i)
+            try
             {
-                var e = _realizedElements.Elements[i];
+                var orientation = Orientation;
+                var u = _realizedElements!.StartU;
 
-                if (e is object)
+                for (var i = 0; i < _realizedElements.Count; ++i)
                 {
-                    var sizeU = _realizedElements.SizeU[i];
-                    var rect = orientation == Orientation.Horizontal ?
-                        new Rect(u, 0, sizeU, finalSize.Height) :
-                        new Rect(0, u, finalSize.Width, sizeU);
-                    e.Arrange(rect);
-                    u += orientation == Orientation.Horizontal ? rect.Width : rect.Height;
+                    var e = _realizedElements.Elements[i];
+
+                    if (e is object)
+                    {
+                        var sizeU = _realizedElements.SizeU[i];
+                        var rect = orientation == Orientation.Horizontal ?
+                            new Rect(u, 0, sizeU, finalSize.Height) :
+                            new Rect(0, u, finalSize.Width, sizeU);
+                        e.Arrange(rect);
+                        u += orientation == Orientation.Horizontal ? rect.Width : rect.Height;
+                    }
                 }
-            }
 
-            return finalSize;
+                return finalSize;
+            }
+            finally
+            {
+                _isInLayout = false;
+            }
         }
 
         protected override void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
@@ -132,20 +157,70 @@ protected override void OnItemsChanged(IList items, NotifyCollectionChangedEvent
             {
                 case NotifyCollectionChangedAction.Add:
                     _realizedElements.ItemsInserted(e.NewStartingIndex, e.NewItems!.Count, _updateElementIndex);
-                    ItemsControl!.ItemContainerGenerator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
                     break;
                 case NotifyCollectionChangedAction.Remove:
                     _realizedElements.ItemsRemoved(e.OldStartingIndex, e.OldItems!.Count, _updateElementIndex, _recycleElement);
-                    ItemsControl!.ItemContainerGenerator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
                     break;
                 case NotifyCollectionChangedAction.Reset:
-                    ////RecycleAllElements();
+                    _realizedElements.RecycleAllElements(_recycleElement);
                     break;
             }
 
             InvalidateMeasure();
         }
 
+        protected internal override Control? ContainerFromIndex(int index) => _realizedElements?.GetElement(index);
+        protected internal override int IndexFromContainer(Control container) => _realizedElements?.GetIndex(container) ?? -1;
+
+        protected internal override void ScrollIntoView(int index)
+        {
+            var items = ItemsControl?.Items as IList;
+
+            if (_isInLayout || items is null || index < 0 || index >= items.Count)
+                return;
+
+            if (GetRealizedElement(index) is Control element)
+            {
+                element.BringIntoView();
+            }
+            else if (this.GetVisualRoot() is ILayoutRoot root)
+            {
+                // Create and measure the element to be brought into view. Store it in a field so that
+                // it can be re-used in the layout pass.
+                _anchorElement = GetOrCreateElement(items, index);
+                _anchorElement.Measure(Size.Infinity);
+                _anchorIndex = index;
+
+                // Get the expected position of the elment and put it in place.
+                var anchorU = GetOrEstimateElementPosition(index);
+                var rect = Orientation == Orientation.Horizontal ?
+                    new Rect(anchorU, 0, _anchorElement.DesiredSize.Width, _anchorElement.DesiredSize.Height) :
+                    new Rect(0, anchorU, _anchorElement.DesiredSize.Width, _anchorElement.DesiredSize.Height);
+                _anchorElement.Arrange(rect);
+
+                // If the item being brought into view was added since the last layout pass then
+                // our bounds won't be updated, so any containing scroll viewers will not have an
+                // updated extent. Do a layout pass to ensure that the containing scroll viewers
+                // will be able to scroll the new item into view.
+                if (!Bounds.Contains(rect) && !_viewport.Contains(rect))
+                {
+                    _isWaitingForViewportUpdate = true;
+                    root.LayoutManager.ExecuteLayoutPass();
+                    _isWaitingForViewportUpdate = false;
+                }
+
+                // Try to bring the item into view and do a layout pass.
+                _anchorElement.BringIntoView();
+
+                _isWaitingForViewportUpdate = !_viewport.Contains(rect);
+                root.LayoutManager.ExecuteLayoutPass();
+                _isWaitingForViewportUpdate = false;
+
+                _anchorElement = null;
+                _anchorIndex = -1;
+            }
+        }
+
         internal IReadOnlyList<Control?> GetRealizedElements()
         {
             return _realizedElements?.Elements ?? Array.Empty<Control>();
@@ -206,7 +281,10 @@ private Size CalculateDesiredSize(Orientation orientation, IList items, double s
 
         private double EstimateElementSizeU()
         {
-            var count = _realizedElements!.Count;
+            if (_realizedElements is null)
+                return _lastEstimatedElementSizeU;
+
+            var count = _realizedElements.Count;
             var divisor = 0.0;
             var total = 0.0;
 
@@ -280,36 +358,89 @@ private void GenerateElements(Size availableSize, ref MeasureViewport viewport)
 
         private Control GetOrCreateElement(IList items, int index)
         {
-            var e = GetRealizedElement(index) ?? GetRecycledOrCreateElement(items, index);
+            var e = GetRealizedElement(index) ?? 
+                GetRecycledElement(items, index) ??
+                CreateElement(items, index);
             InvalidateHack(e);
             return e;
         }
 
         private Control? GetRealizedElement(int index)
         {
-            Debug.Assert(_realizedElements is not null);
-
             if (_anchorIndex == index)
                 return _anchorElement;
-            return _realizedElements!.GetElement(index);
+            return _realizedElements?.GetElement(index);
         }
 
-        private Control GetRecycledOrCreateElement(IList items, int index)
+        private Control? GetRecycledElement(IList items, int index)
         {
             Debug.Assert(ItemsControl is not null);
 
-            var c = ItemsControl!.ItemContainerGenerator.Materialize(index, items[index]!).ContainerControl;
-            Children.Add(c);
-            return c;
+            var generator = ItemsControl!.ItemContainerGenerator;
+            var item = items[index];
+
+            if (item is Control controlItem)
+            {
+                if (controlItem.IsSet(ItemIsOwnContainerProperty))
+                {
+                    controlItem.IsVisible = true;
+                    return controlItem;
+                }
+                else if (generator.IsItemItsOwnContainer(controlItem))
+                {
+                    generator.PrepareItemContainer(controlItem, item, index);
+                    controlItem.SetValue(ItemIsOwnContainerProperty, true);
+                    AddInternalChild(controlItem);
+                    return controlItem;
+                }
+            }
+
+            if (_recyclePool?.Count > 0)
+            {
+                var recycled = _recyclePool.Pop();
+                recycled.IsVisible = true;
+                generator.PrepareItemContainer(recycled, item, index);
+                return recycled;
+            }
+
+            return null;
         }
 
-        private void RecycleElement(Control element)
+        private Control CreateElement(IList items, int index)
         {
             Debug.Assert(ItemsControl is not null);
 
-            var index = ItemsControl.ItemContainerGenerator!.IndexFromContainer(element);
-            ItemsControl!.ItemContainerGenerator.Dematerialize(index, 1);
-            Children.Remove(element);
+            var generator = ItemsControl!.ItemContainerGenerator;
+            var item = items[index];
+            var container = generator.CreateContainer();
+
+            AddInternalChild(container);
+            generator.PrepareItemContainer(container, item, index);
+
+            return container;
+        }
+
+        private double GetOrEstimateElementPosition(int index)
+        {
+            var estimatedElementSize = EstimateElementSizeU();
+            return index * estimatedElementSize;
+        }
+
+        private void RecycleElement(Control element)
+        {
+            Debug.Assert(ItemsControl is not null);
+            
+            if (element.IsSet(ItemIsOwnContainerProperty))
+            {
+                element.IsVisible = false;
+            }
+            else
+            {
+                ItemsControl!.ItemContainerGenerator.ClearItemContainer(element);
+                _recyclePool ??= new();
+                _recyclePool.Push(element);
+                element.IsVisible = false;
+            }
         }
 
         private void UpdateElementIndex(Control element, int index)
@@ -478,6 +609,43 @@ public void Add(int modelIndex, Control element, double u, double sizeU)
                 return (-1, 0);
             }
 
+            /// <summary>
+            /// Gets the position of an element on the primary axis, if realized.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of the element.</param>
+            /// <param name="position">
+            /// When the method exits, contains the element's position on the primary axis, if 
+            /// the element is realized.
+            /// </param>
+            /// <returns>
+            /// True if the requested element was found, otherwise false.
+            /// </returns>
+            public bool TryGetElementU(int modelIndex, out double position)
+            {
+                if (_sizes is null || modelIndex < FirstModelIndex || modelIndex > LastModelIndex)
+                {
+                    position = double.NaN;
+                    return false;
+                }
+
+                var index = modelIndex - FirstModelIndex;
+                position = StartU;
+
+                for (var i = 0; i < index; ++i)
+                {
+                    position += _sizes[i];
+                }
+
+                return true;
+            }
+
+            /// <summary>
+            /// Gets the model index of the specified element.
+            /// </summary>
+            /// <param name="element">The element.</param>
+            /// <returns>The model index or -1 if the element is not present in the collection.</returns>
+            public int GetIndex(Control element) => _elements?.IndexOf(element) is int index && index >= 0 ? index : -1;
+
             /// <summary>
             /// Updates the elements in response to items being inserted into the source collection.
             /// </summary>
diff --git a/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs b/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs
index 587898ac6e9..d8feb579f05 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs
@@ -21,7 +21,7 @@ public TreePageView()
         {
             InitializeComponent();
             _tree = this.GetControl<TreeView>("tree");
-            _tree.ItemContainerGenerator.Index!.Materialized += TreeViewItemMaterialized;
+            ////_tree.ItemContainerGenerator.Index!.Materialized += TreeViewItemMaterialized;
 
             _adorner = new Panel
             {
@@ -103,11 +103,11 @@ private void InitializeComponent()
             AvaloniaXamlLoader.Load(this);
         }
 
-        private void TreeViewItemMaterialized(object? sender, ItemContainerEventArgs e)
-        {
-            var item = (TreeViewItem)e.Containers[0].ContainerControl;
-            item.TemplateApplied += TreeViewItemTemplateApplied;
-        }
+        ////private void TreeViewItemMaterialized(object? sender, ItemContainerEventArgs e)
+        ////{
+        ////    var item = (TreeViewItem)e.Containers[0].ContainerControl;
+        ////    item.TemplateApplied += TreeViewItemTemplateApplied;
+        ////}
 
         private void TreeViewItemTemplateApplied(object? sender, TemplateAppliedEventArgs e)
         {
diff --git a/tests/Avalonia.Controls.UnitTests/CarouselTests.cs b/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
index 1d9e5df74ac..ddf471e5134 100644
--- a/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
@@ -1,341 +1,341 @@
-using System.Collections.ObjectModel;
-using System.Linq;
-using System.Reactive.Subjects;
-using Avalonia.Controls.Presenters;
-using Avalonia.Controls.Templates;
-using Avalonia.Data;
-using Avalonia.LogicalTree;
-using Avalonia.UnitTests;
-using Avalonia.VisualTree;
-using Xunit;
-
-namespace Avalonia.Controls.UnitTests
-{
-    public class CarouselTests
-    {
-        [Fact]
-        public void First_Item_Should_Be_Selected_By_Default()
-        {
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = new[]
-                {
-                    "Foo",
-                    "Bar"
-                }
-            };
-
-            target.ApplyTemplate();
-
-            Assert.Equal(0, target.SelectedIndex);
-            Assert.Equal("Foo", target.SelectedItem);
-        }
-
-        [Fact]
-        public void LogicalChild_Should_Be_Selected_Item()
-        {
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = new[]
-                {
-                    "Foo",
-                    "Bar"
-                }
-            };
-
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
-
-            Assert.Single(target.GetLogicalChildren());
-
-            var child = GetContainerTextBlock(target.GetLogicalChildren().Single());
-
-            Assert.Equal("Foo", child.Text);
-        }
-
-        [Fact]
-        public void Should_Remove_NonCurrent_Page_When_IsVirtualized_True()
-        {
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = new[] { "foo", "bar" },
-                IsVirtualized = true,
-                SelectedIndex = 0,
-            };
-
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
-
-            Assert.Single(target.ItemContainerGenerator.Containers);
-            target.SelectedIndex = 1;
-            Assert.Single(target.ItemContainerGenerator.Containers);
-        }
-
-        [Fact]
-        public void Selected_Item_Changes_To_First_Item_When_Items_Property_Changes()
-        {
-            var items = new ObservableCollection<string>
-            {
-                "Foo",
-                "Bar",
-                "FooBar"
-            };
-
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = items,
-                IsVirtualized = false
-            };
-
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
-
-            Assert.Equal(3, target.GetLogicalChildren().Count());
-
-            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-            Assert.Equal("Foo", child.Text);
-
-            var newItems = items.ToList();
-            newItems.RemoveAt(0);
-
-            target.Items = newItems;
-
-            child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-            Assert.Equal("Bar", child.Text);
-        }
-
-        [Fact]
-        public void Selected_Item_Changes_To_First_Item_When_Items_Property_Changes_And_Virtualized()
-        {
-            var items = new ObservableCollection<string>
-            {
-                "Foo",
-                "Bar",
-                "FooBar"
-            };
-
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = items,
-                IsVirtualized = true,
-            };
-
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
-
-            Assert.Single(target.GetLogicalChildren());
-
-            var child = GetContainerTextBlock(target.GetLogicalChildren().Single());
-
-            Assert.Equal("Foo", child.Text);
-
-            var newItems = items.ToList();
-            newItems.RemoveAt(0);
-
-            target.Items = newItems;
-
-            child = GetContainerTextBlock(target.GetLogicalChildren().Single());
-
-            Assert.Equal("Bar", child.Text);
-        }
-
-        [Fact]
-        public void Selected_Item_Changes_To_First_Item_When_Item_Added()
-        {
-            var items = new ObservableCollection<string>();
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = items,
-                IsVirtualized = false
-            };
-
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
+////using System.Collections.ObjectModel;
+////using System.Linq;
+////using System.Reactive.Subjects;
+////using Avalonia.Controls.Presenters;
+////using Avalonia.Controls.Templates;
+////using Avalonia.Data;
+////using Avalonia.LogicalTree;
+////using Avalonia.UnitTests;
+////using Avalonia.VisualTree;
+////using Xunit;
+
+////namespace Avalonia.Controls.UnitTests
+////{
+////    public class CarouselTests
+////    {
+////        [Fact]
+////        public void First_Item_Should_Be_Selected_By_Default()
+////        {
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = new[]
+////                {
+////                    "Foo",
+////                    "Bar"
+////                }
+////            };
+
+////            target.ApplyTemplate();
+
+////            Assert.Equal(0, target.SelectedIndex);
+////            Assert.Equal("Foo", target.SelectedItem);
+////        }
+
+////        [Fact]
+////        public void LogicalChild_Should_Be_Selected_Item()
+////        {
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = new[]
+////                {
+////                    "Foo",
+////                    "Bar"
+////                }
+////            };
+
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
+
+////            Assert.Single(target.GetLogicalChildren());
+
+////            var child = GetContainerTextBlock(target.GetLogicalChildren().Single());
+
+////            Assert.Equal("Foo", child.Text);
+////        }
+
+////        [Fact]
+////        public void Should_Remove_NonCurrent_Page_When_IsVirtualized_True()
+////        {
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = new[] { "foo", "bar" },
+////                IsVirtualized = true,
+////                SelectedIndex = 0,
+////            };
+
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
+
+////            Assert.Single(target.ItemContainerGenerator.Containers);
+////            target.SelectedIndex = 1;
+////            Assert.Single(target.ItemContainerGenerator.Containers);
+////        }
+
+////        [Fact]
+////        public void Selected_Item_Changes_To_First_Item_When_Items_Property_Changes()
+////        {
+////            var items = new ObservableCollection<string>
+////            {
+////                "Foo",
+////                "Bar",
+////                "FooBar"
+////            };
+
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = items,
+////                IsVirtualized = false
+////            };
+
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
+
+////            Assert.Equal(3, target.GetLogicalChildren().Count());
+
+////            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
+
+////            Assert.Equal("Foo", child.Text);
+
+////            var newItems = items.ToList();
+////            newItems.RemoveAt(0);
+
+////            target.Items = newItems;
+
+////            child = GetContainerTextBlock(target.GetLogicalChildren().First());
+
+////            Assert.Equal("Bar", child.Text);
+////        }
+
+////        [Fact]
+////        public void Selected_Item_Changes_To_First_Item_When_Items_Property_Changes_And_Virtualized()
+////        {
+////            var items = new ObservableCollection<string>
+////            {
+////                "Foo",
+////                "Bar",
+////                "FooBar"
+////            };
+
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = items,
+////                IsVirtualized = true,
+////            };
+
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
+
+////            Assert.Single(target.GetLogicalChildren());
+
+////            var child = GetContainerTextBlock(target.GetLogicalChildren().Single());
+
+////            Assert.Equal("Foo", child.Text);
+
+////            var newItems = items.ToList();
+////            newItems.RemoveAt(0);
+
+////            target.Items = newItems;
+
+////            child = GetContainerTextBlock(target.GetLogicalChildren().Single());
+
+////            Assert.Equal("Bar", child.Text);
+////        }
+
+////        [Fact]
+////        public void Selected_Item_Changes_To_First_Item_When_Item_Added()
+////        {
+////            var items = new ObservableCollection<string>();
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = items,
+////                IsVirtualized = false
+////            };
+
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
 
-            Assert.Equal(-1, target.SelectedIndex);
-            Assert.Empty(target.GetLogicalChildren());
+////            Assert.Equal(-1, target.SelectedIndex);
+////            Assert.Empty(target.GetLogicalChildren());
 
-            items.Add("Foo");
+////            items.Add("Foo");
 
-            Assert.Equal(0, target.SelectedIndex);
-            Assert.Single(target.GetLogicalChildren());
-        }
+////            Assert.Equal(0, target.SelectedIndex);
+////            Assert.Single(target.GetLogicalChildren());
+////        }
 
-        [Fact]
-        public void Selected_Index_Changes_To_None_When_Items_Assigned_Null()
-        {
-            var items = new ObservableCollection<string>
-            {
-                "Foo",
-                "Bar",
-                "FooBar"
-            };
+////        [Fact]
+////        public void Selected_Index_Changes_To_None_When_Items_Assigned_Null()
+////        {
+////            var items = new ObservableCollection<string>
+////            {
+////                "Foo",
+////                "Bar",
+////                "FooBar"
+////            };
 
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = items,
-                IsVirtualized = false
-            };
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = items,
+////                IsVirtualized = false
+////            };
 
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
 
-            Assert.Equal(3, target.GetLogicalChildren().Count());
+////            Assert.Equal(3, target.GetLogicalChildren().Count());
 
-            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
+////            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
 
-            Assert.Equal("Foo", child.Text);
+////            Assert.Equal("Foo", child.Text);
 
-            target.Items = null;
+////            target.Items = null;
 
-            var numChildren = target.GetLogicalChildren().Count();
+////            var numChildren = target.GetLogicalChildren().Count();
 
-            Assert.Equal(0, numChildren);
-            Assert.Equal(-1, target.SelectedIndex);
-        }
-
-        [Fact]
-        public void Selected_Index_Is_Maintained_Carousel_Created_With_Non_Zero_SelectedIndex()
-        {
-            var items = new ObservableCollection<string>
-            {
-                "Foo",
-                "Bar",
-                "FooBar"
-            };
-
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = items,
-                IsVirtualized = false,
-                SelectedIndex = 2
-            };
-
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
-
-            Assert.Equal("FooBar", target.SelectedItem);
-
-            var child = GetContainerTextBlock(target.GetVisualDescendants().LastOrDefault());
-
-            Assert.IsType<TextBlock>(child);
-            Assert.Equal("FooBar", ((TextBlock)child).Text);
-        }
-
-        [Fact]
-        public void Selected_Item_Changes_To_Next_First_Item_When_Item_Removed_From_Beggining_Of_List()
-        {
-            var items = new ObservableCollection<string>
-            {
-                "Foo",
-                "Bar",
-                "FooBar"
-            };
-
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = items,
-                IsVirtualized = false
-            };
-
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
-
-            Assert.Equal(3, target.GetLogicalChildren().Count());
-
-            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-            Assert.Equal("Foo", child.Text);
-
-            items.RemoveAt(0);
-
-            child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-            Assert.IsType<TextBlock>(child);
-            Assert.Equal("Bar", ((TextBlock)child).Text);
-        }
-
-        [Fact]
-        public void Selected_Item_Changes_To_First_Item_If_SelectedItem_Is_Removed_From_Middle()
-        {
-            var items = new ObservableCollection<string>
-            {
-                "Foo",
-                "Bar",
-                "FooBar"
-            };
-
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = items,
-                IsVirtualized = false
-            };
-
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
-
-            target.SelectedIndex = 1;
-
-            items.RemoveAt(1);
-
-            Assert.Equal(0, target.SelectedIndex);
-            Assert.Equal("Foo", target.SelectedItem);
-        }
-
-        private Control CreateTemplate(Carousel control, INameScope scope)
-        {
-            return new CarouselPresenter
-            {
-                Name = "PART_ItemsPresenter",
-                [~CarouselPresenter.IsVirtualizedProperty] = control[~Carousel.IsVirtualizedProperty],
-                [~CarouselPresenter.ItemsPanelProperty] = control[~Carousel.ItemsPanelProperty],
-                [~CarouselPresenter.SelectedIndexProperty] = control[~Carousel.SelectedIndexProperty],
-                [~CarouselPresenter.PageTransitionProperty] = control[~Carousel.PageTransitionProperty],
-            }.RegisterInNameScope(scope);
-        }
-
-        private static TextBlock GetContainerTextBlock(object control)
-        {
-            var contentPresenter = Assert.IsType<ContentPresenter>(control);
-            contentPresenter.UpdateChild();
-            return Assert.IsType<TextBlock>(contentPresenter.Child);
-        }
-
-        [Fact]
-        public void SelectedItem_Validation()
-        {
-            using (UnitTestApplication.Start(TestServices.MockThreadingInterface))
-            {
-                var target = new Carousel
-                {
-                    Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                    IsVirtualized = false
-                };
-
-                target.ApplyTemplate();
-                ((Control)target.Presenter).ApplyTemplate();
-
-                var exception = new System.InvalidCastException("failed validation");
-                var textObservable =
-                    new BehaviorSubject<BindingNotification>(new BindingNotification(exception,
-                        BindingErrorType.DataValidationError));
-                target.Bind(ComboBox.SelectedItemProperty, textObservable);
-
-                Assert.True(DataValidationErrors.GetHasErrors(target));
-                Assert.True(DataValidationErrors.GetErrors(target).SequenceEqual(new[] { exception }));
-            }
-        }
-    }
-}
+////            Assert.Equal(0, numChildren);
+////            Assert.Equal(-1, target.SelectedIndex);
+////        }
+
+////        [Fact]
+////        public void Selected_Index_Is_Maintained_Carousel_Created_With_Non_Zero_SelectedIndex()
+////        {
+////            var items = new ObservableCollection<string>
+////            {
+////                "Foo",
+////                "Bar",
+////                "FooBar"
+////            };
+
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = items,
+////                IsVirtualized = false,
+////                SelectedIndex = 2
+////            };
+
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
+
+////            Assert.Equal("FooBar", target.SelectedItem);
+
+////            var child = GetContainerTextBlock(target.GetVisualDescendants().LastOrDefault());
+
+////            Assert.IsType<TextBlock>(child);
+////            Assert.Equal("FooBar", ((TextBlock)child).Text);
+////        }
+
+////        [Fact]
+////        public void Selected_Item_Changes_To_Next_First_Item_When_Item_Removed_From_Beggining_Of_List()
+////        {
+////            var items = new ObservableCollection<string>
+////            {
+////                "Foo",
+////                "Bar",
+////                "FooBar"
+////            };
+
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = items,
+////                IsVirtualized = false
+////            };
+
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
+
+////            Assert.Equal(3, target.GetLogicalChildren().Count());
+
+////            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
+
+////            Assert.Equal("Foo", child.Text);
+
+////            items.RemoveAt(0);
+
+////            child = GetContainerTextBlock(target.GetLogicalChildren().First());
+
+////            Assert.IsType<TextBlock>(child);
+////            Assert.Equal("Bar", ((TextBlock)child).Text);
+////        }
+
+////        [Fact]
+////        public void Selected_Item_Changes_To_First_Item_If_SelectedItem_Is_Removed_From_Middle()
+////        {
+////            var items = new ObservableCollection<string>
+////            {
+////                "Foo",
+////                "Bar",
+////                "FooBar"
+////            };
+
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = items,
+////                IsVirtualized = false
+////            };
+
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
+
+////            target.SelectedIndex = 1;
+
+////            items.RemoveAt(1);
+
+////            Assert.Equal(0, target.SelectedIndex);
+////            Assert.Equal("Foo", target.SelectedItem);
+////        }
+
+////        private Control CreateTemplate(Carousel control, INameScope scope)
+////        {
+////            return new CarouselPresenter
+////            {
+////                Name = "PART_ItemsPresenter",
+////                [~CarouselPresenter.IsVirtualizedProperty] = control[~Carousel.IsVirtualizedProperty],
+////                [~CarouselPresenter.ItemsPanelProperty] = control[~Carousel.ItemsPanelProperty],
+////                [~CarouselPresenter.SelectedIndexProperty] = control[~Carousel.SelectedIndexProperty],
+////                [~CarouselPresenter.PageTransitionProperty] = control[~Carousel.PageTransitionProperty],
+////            }.RegisterInNameScope(scope);
+////        }
+
+////        private static TextBlock GetContainerTextBlock(object control)
+////        {
+////            var contentPresenter = Assert.IsType<ContentPresenter>(control);
+////            contentPresenter.UpdateChild();
+////            return Assert.IsType<TextBlock>(contentPresenter.Child);
+////        }
+
+////        [Fact]
+////        public void SelectedItem_Validation()
+////        {
+////            using (UnitTestApplication.Start(TestServices.MockThreadingInterface))
+////            {
+////                var target = new Carousel
+////                {
+////                    Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                    IsVirtualized = false
+////                };
+
+////                target.ApplyTemplate();
+////                ((Control)target.Presenter).ApplyTemplate();
+
+////                var exception = new System.InvalidCastException("failed validation");
+////                var textObservable =
+////                    new BehaviorSubject<BindingNotification>(new BindingNotification(exception,
+////                        BindingErrorType.DataValidationError));
+////                target.Bind(ComboBox.SelectedItemProperty, textObservable);
+
+////                Assert.True(DataValidationErrors.GetHasErrors(target));
+////                Assert.True(DataValidationErrors.GetErrors(target).SequenceEqual(new[] { exception }));
+////            }
+////        }
+////    }
+////}
diff --git a/tests/Avalonia.Controls.UnitTests/Generators/ItemContainerGeneratorTests.cs b/tests/Avalonia.Controls.UnitTests/Generators/ItemContainerGeneratorTests.cs
deleted file mode 100644
index 8a053c2a913..00000000000
--- a/tests/Avalonia.Controls.UnitTests/Generators/ItemContainerGeneratorTests.cs
+++ /dev/null
@@ -1,173 +0,0 @@
-using System.Collections.Generic;
-using System.Linq;
-using System.Reactive.Linq;
-using Avalonia.Controls.Generators;
-using Avalonia.Controls.Presenters;
-using Avalonia.Data;
-using Xunit;
-
-namespace Avalonia.Controls.UnitTests.Generators
-{
-    public class ItemContainerGeneratorTests
-    {
-        [Fact]
-        public void Materialize_Should_Create_Containers()
-        {
-            var items = new[] { "foo", "bar", "baz" };
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator(owner);
-            var containers = Materialize(target, 0, items);
-            var result = containers
-                .Select(x => x.ContainerControl)
-                .OfType<ContentPresenter>()
-                .Select(x => x.Content)
-                .ToList();
-
-            Assert.Equal(items, result);
-        }
-
-        [Fact]
-        public void ContainerFromIndex_Should_Return_Materialized_Containers()
-        {
-            var items = new[] { "foo", "bar", "baz" };
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator(owner);
-            var containers = Materialize(target, 0, items);
-
-            Assert.Equal(containers[0].ContainerControl, target.ContainerFromIndex(0));
-            Assert.Equal(containers[1].ContainerControl, target.ContainerFromIndex(1));
-            Assert.Equal(containers[2].ContainerControl, target.ContainerFromIndex(2));
-        }
-
-        [Fact]
-        public void IndexFromContainer_Should_Return_Index()
-        {
-            var items = new[] { "foo", "bar", "baz" };
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator(owner);
-            var containers = Materialize(target, 0, items);
-
-            Assert.Equal(0, target.IndexFromContainer(containers[0].ContainerControl));
-            Assert.Equal(1, target.IndexFromContainer(containers[1].ContainerControl));
-            Assert.Equal(2, target.IndexFromContainer(containers[2].ContainerControl));
-        }
-
-        [Fact]
-        public void Dematerialize_Should_Remove_Container()
-        {
-            var items = new[] { "foo", "bar", "baz" };
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator(owner);
-            var containers = Materialize(target, 0, items);
-
-            target.Dematerialize(1, 1);
-
-            Assert.Equal(containers[0].ContainerControl, target.ContainerFromIndex(0));
-            Assert.Null(target.ContainerFromIndex(1));
-            Assert.Equal(containers[2].ContainerControl, target.ContainerFromIndex(2));
-        }
-
-        [Fact]
-        public void Dematerialize_Should_Return_Removed_Containers()
-        {
-            var items = new[] { "foo", "bar", "baz" };
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator(owner);
-            var containers = Materialize(target, 0, items);
-            var expected = target.Containers.Take(2).ToList();
-            var result = target.Dematerialize(0, 2);
-
-            Assert.Equal(expected, result);
-        }
-
-        [Fact]
-        public void InsertSpace_Should_Alter_Successive_Container_Indexes()
-        {
-            var items = new[] { "foo", "bar", "baz" };
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator(owner);
-            var containers = Materialize(target, 0, items);
-
-            target.InsertSpace(1, 3);
-
-            Assert.Equal(3, target.Containers.Count());
-            Assert.Equal(new[] { 0, 4, 5 }, target.Containers.Select(x => x.Index));
-        }
-
-        [Fact]
-        public void RemoveRange_Should_Alter_Successive_Container_Indexes()
-        {
-            var items = new[] { "foo", "bar", "baz" };
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator(owner);
-            var containers = Materialize(target, 0, items);
-
-            var removed = target.RemoveRange(1, 1).Single();
-
-            Assert.Equal(containers[0].ContainerControl, target.ContainerFromIndex(0));
-            Assert.Equal(containers[2].ContainerControl, target.ContainerFromIndex(1));
-            Assert.Equal(containers[1], removed);
-            Assert.Equal(new[] { 0, 1 }, target.Containers.Select(x => x.Index));
-        }
-
-        [Fact]
-        public void Style_Binding_Should_Be_Able_To_Override_Content()
-        {
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator(owner);
-            var container = (ContentPresenter)target.Materialize(0, "foo").ContainerControl;
-
-            Assert.Equal("foo", container.Content);
-
-            container.Bind(
-                ContentPresenter.ContentProperty,
-                Observable.Never<object>().StartWith("bar"),
-                BindingPriority.Style);
-
-            Assert.Equal("bar", container.Content);
-        }
-
-        [Fact]
-        public void Style_Binding_Should_Be_Able_To_Override_Content_Typed()
-        {
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator<ListBoxItem>(owner, ListBoxItem.ContentProperty, null);
-            var container = (ListBoxItem)target.Materialize(0, "foo").ContainerControl;
-
-            Assert.Equal("foo", container.Content);
-
-            container.Bind(
-                ContentPresenter.ContentProperty,
-                Observable.Never<object>().StartWith("bar"),
-                BindingPriority.Style);
-
-            Assert.Equal("bar", container.Content);
-        }
-
-        [Fact]
-        public void Materialize_Should_Create_Containers_When_Item_Is_Null()
-        {
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator<ListBoxItem>(owner, ListBoxItem.ContentProperty, null);
-            var container = (ListBoxItem)target.Materialize(0, null).ContainerControl;
-
-            Assert.True(container != null, "The containers is not materialized.");
-        }
-
-        private static IList<ItemContainerInfo> Materialize(
-            IItemContainerGenerator generator,
-            int index,
-            string[] items)
-        {
-            var result = new List<ItemContainerInfo>();
-
-            foreach (var item in items)
-            {
-                var container = generator.Materialize(index++, item);
-                result.Add(container);
-            }
-
-            return result;
-        }
-    }
-}
diff --git a/tests/Avalonia.Controls.UnitTests/Generators/ItemContainerGeneratorTypedTests.cs b/tests/Avalonia.Controls.UnitTests/Generators/ItemContainerGeneratorTypedTests.cs
deleted file mode 100644
index f63a764a21e..00000000000
--- a/tests/Avalonia.Controls.UnitTests/Generators/ItemContainerGeneratorTypedTests.cs
+++ /dev/null
@@ -1,42 +0,0 @@
-using System.Collections.Generic;
-using System.Linq;
-using Avalonia.Controls.Generators;
-using Xunit;
-
-namespace Avalonia.Controls.UnitTests.Generators
-{
-    public class ItemContainerGeneratorTypedTests
-    {
-        [Fact]
-        public void Materialize_Should_Create_Containers()
-        {
-            var items = new[] { "foo", "bar", "baz" };
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator<ListBoxItem>(owner, ListBoxItem.ContentProperty, null);
-            var containers = Materialize(target, 0, items);
-            var result = containers
-                .Select(x => x.ContainerControl)
-                .OfType<ListBoxItem>()
-                .Select(x => x.Content)
-                .ToList();
-
-            Assert.Equal(items, result);
-        }
-
-        private static IList<ItemContainerInfo> Materialize(
-            IItemContainerGenerator generator,
-            int index,
-            string[] items)
-        {
-            var result = new List<ItemContainerInfo>();
-
-            foreach (var item in items)
-            {
-                var container = generator.Materialize(index++, item);
-                result.Add(container);
-            }
-
-            return result;
-        }
-    }
-}
diff --git a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
index ada5e10a7f4..25d93746d58 100644
--- a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
@@ -1,3 +1,4 @@
+using System;
 using System.Collections.ObjectModel;
 using System.Collections.Specialized;
 using System.Linq;
@@ -367,12 +368,13 @@ public void Should_Clear_Containers_When_ItemsPresenter_Changes()
             target.ApplyTemplate();
             target.Presenter.ApplyTemplate();
 
-            Assert.Equal(2, target.ItemContainerGenerator.Containers.Count());
+            var panel = target.Presenter.Panel;
+            Assert.Equal(2, panel.Children.Count());
 
             target.Template = GetTemplate();
             target.ApplyTemplate();
 
-            Assert.Empty(target.ItemContainerGenerator.Containers);
+            Assert.Empty(panel.Children);
         }
 
         [Fact]
@@ -535,26 +537,6 @@ public void Single_Item_Class_Should_Not_Be_Set_When_Items_Collection_Count_Incr
             Assert.DoesNotContain(":singleitem", target.Classes);
         }
 
-        [Fact]
-        public void Setting_Presenter_Explicitly_Should_Set_Item_Parent()
-        {
-            var target = new TestItemsControl();
-            var child = new Control();
-
-            var presenter = new ItemsPresenter
-            {
-                [StyledElement.TemplatedParentProperty] = target,
-            };
-
-            presenter.ApplyTemplate();
-            target.Presenter = presenter;
-            target.Items = new[] { child };
-            target.ApplyTemplate();
-
-            Assert.Equal(target, child.Parent);
-            Assert.Equal(target, ((ILogical)child).LogicalParent);
-        }
-
         [Fact]
         public void DataContexts_Should_Be_Correctly_Set()
         {
@@ -683,36 +665,6 @@ public void Does_Not_Focus_Non_Focusable_Item_On_Key_Down()
             }
         }
 
-        [Fact]
-        public void Presenter_Items_Should_Be_In_Sync()
-        {
-            var target = new ItemsControl
-            {
-                Template = GetTemplate(),
-                Items = new object[]
-                {
-                    new Button(),
-                    new Button(),
-                },
-            };
-
-            var root = new TestRoot { Child = target };
-            var otherPanel = new StackPanel();
-
-            target.ApplyTemplate();
-            target.Presenter.ApplyTemplate();
-            
-            target.ItemContainerGenerator.Materialized += (s, e) =>
-            {
-                Assert.IsType<Canvas>(e.Containers[0].Item);
-            };
-
-            target.Items = new[]
-            {
-                new Canvas()
-            };
-        }
-
         [Fact]
         public void Detaching_Then_Reattaching_To_Logical_Tree_Twice_Does_Not_Throw()
         {
@@ -780,14 +732,5 @@ private static FuncControlTemplate GetTemplate()
                 };
             });
         }
-
-        private class TestItemsControl : ItemsControl
-        {
-            public new ItemsPresenter Presenter
-            {
-                get { return base.Presenter; }
-                set { base.Presenter = value; }
-            }
-        }
     }
 }
diff --git a/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs b/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
index 280f140a794..cc824876ac5 100644
--- a/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
@@ -8,6 +8,7 @@
 using Avalonia.Controls.Templates;
 using Avalonia.Data;
 using Avalonia.Input;
+using Avalonia.Layout;
 using Avalonia.LogicalTree;
 using Avalonia.Styling;
 using Avalonia.UnitTests;
@@ -218,6 +219,7 @@ public void Selection_Should_Be_Cleared_On_Recycled_Items()
 
                 // Scroll down a page.
                 target.Scroll.Offset = new Vector(0, 10);
+                Layout(target);
 
                 // Make sure recycled item isn't now selected.
                 Assert.False(((ListBoxItem)target.Presenter.Panel.Children[0]).IsSelected);
@@ -239,8 +241,8 @@ public void ScrollViewer_Should_Have_Correct_Extent_And_Viewport()
 
                 Prepare(target);
 
-                Assert.Equal(new Size(20, 20), target.Scroll.Extent);
-                Assert.Equal(new Size(100, 10), target.Scroll.Viewport);
+                Assert.Equal(new Size(100, 200), target.Scroll.Extent);
+                Assert.Equal(new Size(100, 100), target.Scroll.Viewport);
             }
         }
 
@@ -263,11 +265,13 @@ public void Containers_Correct_After_Clear_Add_Remove()
 
                 items.Clear();
                 items.AddRange(Enumerable.Range(0, 11).Select(x => $"Item {x}"));
+                Layout(target);
+
                 items.Remove("Item 2");
+                Layout(target);
 
-                Assert.Equal(
-                    items,
-                    target.Presenter.Panel.Children.Cast<ListBoxItem>().Select(x => (string)x.Content));
+                var actual = target.Presenter.Panel.Children.Cast<ListBoxItem>().Select(x => (string)x.Content).ToList();
+                Assert.Equal(items.OrderBy(x => x), actual.OrderBy(x => x));
             }
         }
 
@@ -328,44 +332,6 @@ private void RaisePressedEvent(ListBox listBox, ListBoxItem item, MouseButton mo
             _mouse.Click(listBox, item, mouseButton);
         }
 
-        [Fact]
-        public void ListBox_After_Scroll_IndexOutOfRangeException_Shouldnt_Be_Thrown()
-        {
-            throw new NotImplementedException();
-            ////using (UnitTestApplication.Start(TestServices.StyledWindow))
-            ////{
-            ////    var items = Enumerable.Range(0, 11).Select(x => $"{x}").ToArray();
-
-            ////    var target = new ListBox
-            ////    {
-            ////        Template = ListBoxTemplate(),
-            ////        Items = items,
-            ////        ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 11 })
-            ////    };
-
-            ////    Prepare(target);
-
-            ////    var panel = target.Presenter.Panel as IVirtualizingPanel;
-
-            ////    var listBoxItems = panel.Children.OfType<ListBoxItem>();
-
-            ////    //virtualization should have created exactly 10 items
-            ////    Assert.Equal(10, listBoxItems.Count());
-            ////    Assert.Equal("0", listBoxItems.First().DataContext);
-            ////    Assert.Equal("9", listBoxItems.Last().DataContext);
-
-            ////    //instead pixeloffset > 0 there could be pretty complex sequence for repro
-            ////    //it involves add/remove/scroll to end multiple actions
-            ////    //which i can't find so far :(, but this is the simplest way to add it to unit test
-            ////    panel.PixelOffset = 1;
-
-            ////    //here scroll to end -> IndexOutOfRangeException is thrown
-            ////    target.Scroll.Offset = new Vector(0, 2);
-
-            ////    Assert.True(true);
-            ////}
-        }
-
         [Fact]
         public void LayoutManager_Should_Measure_Arrange_All()
         {
@@ -464,11 +430,11 @@ public void ListBox_Should_Be_Valid_After_Remove_Of_Item_In_NonVisibleArea()
                 items.Remove("1");
                 lm.ExecuteLayoutPass();
 
-                Assert.Equal("30", target.ItemContainerGenerator.ContainerFromIndex(items.Count - 1).DataContext);
-                Assert.Equal("29", target.ItemContainerGenerator.ContainerFromIndex(items.Count - 2).DataContext);
-                Assert.Equal("28", target.ItemContainerGenerator.ContainerFromIndex(items.Count - 3).DataContext);
-                Assert.Equal("27", target.ItemContainerGenerator.ContainerFromIndex(items.Count - 4).DataContext);
-                Assert.Equal("26", target.ItemContainerGenerator.ContainerFromIndex(items.Count - 5).DataContext);
+                Assert.Equal("30", target.ContainerFromIndex(items.Count - 1).DataContext);
+                Assert.Equal("29", target.ContainerFromIndex(items.Count - 2).DataContext);
+                Assert.Equal("28", target.ContainerFromIndex(items.Count - 3).DataContext);
+                Assert.Equal("27", target.ContainerFromIndex(items.Count - 4).DataContext);
+                Assert.Equal("26", target.ContainerFromIndex(items.Count - 5).DataContext);
             }
         }
 
@@ -525,7 +491,7 @@ public void Adding_And_Selecting_Item_With_AutoScrollToSelectedItem_Should_NotHi
 
                 var target = new ListBox()
                 {
-                    VerticalAlignment = Layout.VerticalAlignment.Top,
+                    VerticalAlignment = VerticalAlignment.Top,
                     AutoScrollToSelectedItem = true,
                     Width = 50,
                     ItemTemplate = new FuncDataTemplate<object>((c, _) => new Border() { Height = 10 }),
@@ -627,6 +593,8 @@ private static FuncControlTemplate ScrollViewerTemplate()
                             [~~ScrollContentPresenter.ExtentProperty] = parent[~~ScrollViewer.ExtentProperty],
                             [~~ScrollContentPresenter.OffsetProperty] = parent[~~ScrollViewer.OffsetProperty],
                             [~~ScrollContentPresenter.ViewportProperty] = parent[~~ScrollViewer.ViewportProperty],
+                            [~ScrollContentPresenter.CanHorizontallyScrollProperty] = parent[~ScrollViewer.CanHorizontallyScrollProperty],
+                            [~ScrollContentPresenter.CanVerticallyScrollProperty] = parent[~ScrollViewer.CanVerticallyScrollProperty],
                         }.RegisterInNameScope(scope),
                         new ScrollBar
                         {
@@ -640,45 +608,28 @@ private static FuncControlTemplate ScrollViewerTemplate()
 
         private static void Prepare(ListBox target)
         {
-            // The ListBox needs to be part of a rooted visual tree.
-            var root = new TestRoot();
-            root.Child = target;
-
-            // Apply the template to the ListBox itself.
-            target.ApplyTemplate();
+            target.Width = target.Height = 100;
 
-            // Then to its inner ScrollViewer.
-            var scrollViewer = (ScrollViewer)target.GetVisualChildren().Single();
-            scrollViewer.ApplyTemplate();
-
-            // Then make the ScrollViewer create its child.
-            ((ContentPresenter)scrollViewer.Presenter).UpdateChild();
-
-            // Now the ItemsPresenter should be reigstered, so apply its template.
-            target.Presenter.ApplyTemplate();
-
-            // Because ListBox items are virtualized we need to do a layout to make them appear.
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            // Now set and apply the item templates.
-            foreach (ListBoxItem item in target.Presenter.Panel.Children)
+            var root = new TestRoot(target)
             {
-                item.Template = ListBoxItemTemplate();
-                item.ApplyTemplate();
-                item.Presenter.ApplyTemplate();
-                ((ContentPresenter)item.Presenter).UpdateChild();
-            }
+                Resources =
+                {
+                    { 
+                        typeof(ListBoxItem),
+                        new ControlTheme(typeof(ListBoxItem))
+                        {
+                            Setters = { new Setter(ListBoxItem.TemplateProperty, ListBoxItemTemplate()) }
+                        }
+                    }
+                }
+            };
 
-            // The items were created before the template was applied, so now we need to go back
-            // and re-arrange everything.
-            foreach (Control i in target.GetSelfAndVisualDescendants())
-            {
-                i.InvalidateMeasure();
-            }
+            root.LayoutManager.ExecuteInitialLayoutPass();
+        }
 
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+        private static void Layout(Control c)
+        {
+            ((ILayoutRoot)c.GetVisualRoot()).LayoutManager.ExecuteLayoutPass();
         }
 
         private class Item
diff --git a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
index 8be1e112e79..8ded57956ba 100644
--- a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
@@ -1,1475 +1,1475 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Collections.ObjectModel;
-using System.ComponentModel;
-using System.Linq;
-using System.Runtime.CompilerServices;
-using Avalonia.Collections;
-using Avalonia.Controls.Generators;
-using Avalonia.Controls.Presenters;
-using Avalonia.Controls.Templates;
-using Avalonia.Data;
-using Avalonia.Data.Core;
-using Avalonia.Input;
-using Avalonia.Input.Platform;
-using Avalonia.Interactivity;
-using Avalonia.LogicalTree;
-using Avalonia.Styling;
-using Avalonia.UnitTests;
-using JetBrains.Annotations;
-using Moq;
-using Xunit;
-
-namespace Avalonia.Controls.UnitTests
-{
-    public class TreeViewTests
-    {
-        MouseTestHelper _mouse = new MouseTestHelper();
-
-        [Fact]
-        public void Items_Should_Be_Created()
-        {
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = CreateTestTreeData(),
-            };
-
-            var root = new TestRoot(target);
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-
-            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
-            Assert.Equal(new[] { "Child1", "Child2", "Child3" }, ExtractItemHeader(target, 1));
-            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
-        }
-
-        [Fact]
-        public void Items_Should_Be_Created_Using_ItemTemplate_If_Present()
-        {
-            TreeView target;
-
-            var root = new TestRoot
-            {
-                Child = target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = CreateTestTreeData(),
-                    ItemTemplate = new FuncTreeDataTemplate<Node>(
-                        (_, __) => new Canvas(),
-                        x => x.Children),
-                }
-            };
-
-            ApplyTemplates(target);
-
-            var items = target.ItemContainerGenerator.Index.Containers
-                .OfType<TreeViewItem>()
-                .ToList();
-
-            Assert.Equal(5, items.Count);
-            Assert.All(items, x => Assert.IsType<Canvas>(x.HeaderPresenter.Child));
-        }
-
-        [Fact]
-        public void Items_Should_Be_Created_Using_ItemConatinerTheme_If_Present()
-        {
-            TreeView target;
-            var theme = new ControlTheme(typeof(TreeViewItem));
-
-            var root = new TestRoot
-            {
-                Child = target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = CreateTestTreeData(),
-                    ItemContainerTheme = theme,
-                    ItemTemplate = new FuncTreeDataTemplate<Node>(
-                        (_, __) => new Canvas(),
-                        x => x.Children),
-                }
-            };
-
-            ApplyTemplates(target);
-
-            var items = target.ItemContainerGenerator.Index.Containers
-                .OfType<TreeViewItem>()
-                .ToList();
-
-            Assert.Equal(5, items.Count);
-            Assert.All(items, x => Assert.Same(theme, x.ItemContainerTheme));
-        }
-
-        [Fact]
-        public void Root_ItemContainerGenerator_Containers_Should_Be_Root_Containers()
-        {
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = CreateTestTreeData(),
-            };
-
-            var root = new TestRoot(target);
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-
-            var container = (TreeViewItem)target.ItemContainerGenerator.Containers.Single().ContainerControl;
-            var header = (TextBlock)container.Header;
-            Assert.Equal("Root", header.Text);
-        }
-
-        [Fact]
-        public void Root_TreeContainerFromItem_Should_Return_Descendant_Item()
-        {
-            var tree = CreateTestTreeData();
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = tree,
-            };
-
-            // For TreeViewItem to find its parent TreeView, OnAttachedToLogicalTree needs
-            // to be called, which requires an IStyleRoot.
-            var root = new TestRoot();
-            root.Child = target;
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-
-            var container = target.ItemContainerGenerator.Index.ContainerFromItem(
-                tree[0].Children[1].Children[0]);
-
-            Assert.NotNull(container);
-
-            var header = ((TreeViewItem)container).Header;
-            var headerContent = ((TextBlock)header).Text;
-
-            Assert.Equal("Grandchild2a", headerContent);
-        }
-
-        [Fact]
-        public void Clicking_Item_Should_Select_It()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var item = tree[0].Children[1].Children[0];
-                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
-
-                Assert.NotNull(container);
-
-                _mouse.Click(container);
-
-                Assert.Equal(item, target.SelectedItem);
-                Assert.True(container.IsSelected);
-            }
-        }
-
-        [Fact]
-        public void Clicking_WithControlModifier_Selected_Item_Should_Deselect_It()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var item = tree[0].Children[1].Children[0];
-                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
-
-                Assert.NotNull(container);
-
-                target.SelectedItem = item;
-
-                Assert.True(container.IsSelected);
-
-                _mouse.Click(container, modifiers: KeyModifiers.Control);
-
-                Assert.Null(target.SelectedItem);
-                Assert.False(container.IsSelected);
-            }
-        }
-
-        [Fact]
-        public void Clicking_WithControlModifier_Not_Selected_Item_Should_Select_It()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree
-                };
+////using System;
+////using System.Collections;
+////using System.Collections.Generic;
+////using System.Collections.ObjectModel;
+////using System.ComponentModel;
+////using System.Linq;
+////using System.Runtime.CompilerServices;
+////using Avalonia.Collections;
+////using Avalonia.Controls.Generators;
+////using Avalonia.Controls.Presenters;
+////using Avalonia.Controls.Templates;
+////using Avalonia.Data;
+////using Avalonia.Data.Core;
+////using Avalonia.Input;
+////using Avalonia.Input.Platform;
+////using Avalonia.Interactivity;
+////using Avalonia.LogicalTree;
+////using Avalonia.Styling;
+////using Avalonia.UnitTests;
+////using JetBrains.Annotations;
+////using Moq;
+////using Xunit;
+
+////namespace Avalonia.Controls.UnitTests
+////{
+////    public class TreeViewTests
+////    {
+////        MouseTestHelper _mouse = new MouseTestHelper();
+
+////        [Fact]
+////        public void Items_Should_Be_Created()
+////        {
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = CreateTestTreeData(),
+////            };
+
+////            var root = new TestRoot(target);
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+
+////            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
+////            Assert.Equal(new[] { "Child1", "Child2", "Child3" }, ExtractItemHeader(target, 1));
+////            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
+////        }
+
+////        [Fact]
+////        public void Items_Should_Be_Created_Using_ItemTemplate_If_Present()
+////        {
+////            TreeView target;
+
+////            var root = new TestRoot
+////            {
+////                Child = target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = CreateTestTreeData(),
+////                    ItemTemplate = new FuncTreeDataTemplate<Node>(
+////                        (_, __) => new Canvas(),
+////                        x => x.Children),
+////                }
+////            };
+
+////            ApplyTemplates(target);
+
+////            var items = target.ItemContainerGenerator.Index.Containers
+////                .OfType<TreeViewItem>()
+////                .ToList();
+
+////            Assert.Equal(5, items.Count);
+////            Assert.All(items, x => Assert.IsType<Canvas>(x.HeaderPresenter.Child));
+////        }
+
+////        [Fact]
+////        public void Items_Should_Be_Created_Using_ItemConatinerTheme_If_Present()
+////        {
+////            TreeView target;
+////            var theme = new ControlTheme(typeof(TreeViewItem));
+
+////            var root = new TestRoot
+////            {
+////                Child = target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = CreateTestTreeData(),
+////                    ItemContainerTheme = theme,
+////                    ItemTemplate = new FuncTreeDataTemplate<Node>(
+////                        (_, __) => new Canvas(),
+////                        x => x.Children),
+////                }
+////            };
+
+////            ApplyTemplates(target);
+
+////            var items = target.ItemContainerGenerator.Index.Containers
+////                .OfType<TreeViewItem>()
+////                .ToList();
+
+////            Assert.Equal(5, items.Count);
+////            Assert.All(items, x => Assert.Same(theme, x.ItemContainerTheme));
+////        }
+
+////        [Fact]
+////        public void Root_ItemContainerGenerator_Containers_Should_Be_Root_Containers()
+////        {
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = CreateTestTreeData(),
+////            };
+
+////            var root = new TestRoot(target);
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+
+////            var container = (TreeViewItem)target.ItemContainerGenerator.Containers.Single().ContainerControl;
+////            var header = (TextBlock)container.Header;
+////            Assert.Equal("Root", header.Text);
+////        }
+
+////        [Fact]
+////        public void Root_TreeContainerFromItem_Should_Return_Descendant_Item()
+////        {
+////            var tree = CreateTestTreeData();
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = tree,
+////            };
+
+////            // For TreeViewItem to find its parent TreeView, OnAttachedToLogicalTree needs
+////            // to be called, which requires an IStyleRoot.
+////            var root = new TestRoot();
+////            root.Child = target;
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+
+////            var container = target.ItemContainerGenerator.Index.ContainerFromItem(
+////                tree[0].Children[1].Children[0]);
+
+////            Assert.NotNull(container);
+
+////            var header = ((TreeViewItem)container).Header;
+////            var headerContent = ((TextBlock)header).Text;
+
+////            Assert.Equal("Grandchild2a", headerContent);
+////        }
+
+////        [Fact]
+////        public void Clicking_Item_Should_Select_It()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var item = tree[0].Children[1].Children[0];
+////                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
+
+////                Assert.NotNull(container);
+
+////                _mouse.Click(container);
+
+////                Assert.Equal(item, target.SelectedItem);
+////                Assert.True(container.IsSelected);
+////            }
+////        }
+
+////        [Fact]
+////        public void Clicking_WithControlModifier_Selected_Item_Should_Deselect_It()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var item = tree[0].Children[1].Children[0];
+////                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
+
+////                Assert.NotNull(container);
+
+////                target.SelectedItem = item;
+
+////                Assert.True(container.IsSelected);
+
+////                _mouse.Click(container, modifiers: KeyModifiers.Control);
+
+////                Assert.Null(target.SelectedItem);
+////                Assert.False(container.IsSelected);
+////            }
+////        }
+
+////        [Fact]
+////        public void Clicking_WithControlModifier_Not_Selected_Item_Should_Select_It()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree
+////                };
 
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
 
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
 
-                var item1 = tree[0].Children[1].Children[0];
-                var container1 = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item1);
+////                var item1 = tree[0].Children[1].Children[0];
+////                var container1 = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item1);
 
-                var item2 = tree[0].Children[1];
-                var container2 = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item2);
+////                var item2 = tree[0].Children[1];
+////                var container2 = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item2);
 
-                Assert.NotNull(container1);
-                Assert.NotNull(container2);
-
-                target.SelectedItem = item1;
-
-                Assert.True(container1.IsSelected);
-
-                _mouse.Click(container2, modifiers: KeyModifiers.Control);
-
-                Assert.Equal(item2, target.SelectedItem);
-                Assert.False(container1.IsSelected);
-                Assert.True(container2.IsSelected);
-            }
-        }
-
-        [Fact]
-        public void Clicking_WithControlModifier_Selected_Item_Should_Deselect_And_Remove_From_SelectedItems()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple
-                };
+////                Assert.NotNull(container1);
+////                Assert.NotNull(container2);
+
+////                target.SelectedItem = item1;
+
+////                Assert.True(container1.IsSelected);
+
+////                _mouse.Click(container2, modifiers: KeyModifiers.Control);
+
+////                Assert.Equal(item2, target.SelectedItem);
+////                Assert.False(container1.IsSelected);
+////                Assert.True(container2.IsSelected);
+////            }
+////        }
+
+////        [Fact]
+////        public void Clicking_WithControlModifier_Selected_Item_Should_Deselect_And_Remove_From_SelectedItems()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple
+////                };
 
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
 
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
 
-                var rootNode = tree[0];
-
-                var item1 = rootNode.Children[0];
-                var item2 = rootNode.Children.Last();
-
-                var item1Container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item1);
-                var item2Container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item2);
-
-                ClickContainer(item1Container, KeyModifiers.Control);
-                Assert.True(item1Container.IsSelected);
-
-                ClickContainer(item2Container, KeyModifiers.Control);
-                Assert.True(item2Container.IsSelected);
+////                var rootNode = tree[0];
+
+////                var item1 = rootNode.Children[0];
+////                var item2 = rootNode.Children.Last();
+
+////                var item1Container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item1);
+////                var item2Container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item2);
+
+////                ClickContainer(item1Container, KeyModifiers.Control);
+////                Assert.True(item1Container.IsSelected);
+
+////                ClickContainer(item2Container, KeyModifiers.Control);
+////                Assert.True(item2Container.IsSelected);
 
-                Assert.Equal(new[] { item1, item2 }, target.SelectedItems.OfType<Node>());
+////                Assert.Equal(new[] { item1, item2 }, target.SelectedItems.OfType<Node>());
 
-                ClickContainer(item1Container, KeyModifiers.Control);
-                Assert.False(item1Container.IsSelected);
+////                ClickContainer(item1Container, KeyModifiers.Control);
+////                Assert.False(item1Container.IsSelected);
 
-                Assert.DoesNotContain(item1, target.SelectedItems.OfType<Node>());
-            }
-        }
+////                Assert.DoesNotContain(item1, target.SelectedItems.OfType<Node>());
+////            }
+////        }
 
-        [Fact]
-        public void Clicking_WithShiftModifier_DownDirection_Should_Select_Range_Of_Items()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple
-                };
+////        [Fact]
+////        public void Clicking_WithShiftModifier_DownDirection_Should_Select_Range_Of_Items()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple
+////                };
 
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
 
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
 
-                var rootNode = tree[0];
+////                var rootNode = tree[0];
 
-                var from = rootNode.Children[0];
-                var to = rootNode.Children.Last();
+////                var from = rootNode.Children[0];
+////                var to = rootNode.Children.Last();
 
-                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
+////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
 
-                ClickContainer(fromContainer, KeyModifiers.None);
+////                ClickContainer(fromContainer, KeyModifiers.None);
 
-                Assert.True(fromContainer.IsSelected);
+////                Assert.True(fromContainer.IsSelected);
 
-                ClickContainer(toContainer, KeyModifiers.Shift);
-                AssertChildrenSelected(target, rootNode);
-            }
-        }
+////                ClickContainer(toContainer, KeyModifiers.Shift);
+////                AssertChildrenSelected(target, rootNode);
+////            }
+////        }
 
-        [Fact]
-        public void Clicking_WithShiftModifier_UpDirection_Should_Select_Range_Of_Items()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
+////        [Fact]
+////        public void Clicking_WithShiftModifier_UpDirection_Should_Select_Range_Of_Items()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
 
-                var rootNode = tree[0];
-
-                var from = rootNode.Children.Last();
-                var to = rootNode.Children[0];
-
-                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-                ClickContainer(fromContainer, KeyModifiers.None);
+////                var rootNode = tree[0];
+
+////                var from = rootNode.Children.Last();
+////                var to = rootNode.Children[0];
+
+////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
+////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+
+////                ClickContainer(fromContainer, KeyModifiers.None);
 
-                Assert.True(fromContainer.IsSelected);
+////                Assert.True(fromContainer.IsSelected);
 
-                ClickContainer(toContainer, KeyModifiers.Shift);
-                AssertChildrenSelected(target, rootNode);
-            }
-        }
+////                ClickContainer(toContainer, KeyModifiers.Shift);
+////                AssertChildrenSelected(target, rootNode);
+////            }
+////        }
 
-        [Fact]
-        public void Clicking_First_Item_Of_SelectedItems_Should_Select_Only_It()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var rootNode = tree[0];
-
-                var from = rootNode.Children.Last();
-                var to = rootNode.Children[0];
-
-                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-                ClickContainer(fromContainer, KeyModifiers.None);
-
-                ClickContainer(toContainer, KeyModifiers.Shift);
-                AssertChildrenSelected(target, rootNode);
-
-                ClickContainer(fromContainer, KeyModifiers.None);
-
-                Assert.True(fromContainer.IsSelected);
-
-                foreach (var child in rootNode.Children)
-                {
-                    if (child == from)
-                    {
-                        continue;
-                    }
-
-                    var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(child);
-
-                    Assert.False(container.IsSelected);
-                }
-            }
-        }
-
-        [Fact]
-        public void Setting_SelectedItem_Should_Set_Container_Selected()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var item = tree[0].Children[1].Children[0];
-                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
-
-                Assert.NotNull(container);
-
-                target.SelectedItem = item;
-
-                Assert.True(container.IsSelected);
-            }
-        }
-
-        [Fact]
-        public void Setting_SelectedItem_Should_Raise_SelectedItemChanged_Event()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var item = tree[0].Children[1].Children[0];
-
-                var called = false;
-                target.SelectionChanged += (s, e) =>
-                {
-                    Assert.Empty(e.RemovedItems);
-                    Assert.Equal(1, e.AddedItems.Count);
-                    Assert.Same(item, e.AddedItems[0]);
-                    called = true;
-                };
-
-                target.SelectedItem = item;
-                Assert.True(called);
-            }
-        }
-
-        [Fact]
-        public void Bound_SelectedItem_Should_Not_Be_Cleared_when_Changing_Selection()
-        {
-            using (Application())
-            {
-                var dataContext = new TestDataContext();
-
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    DataContext = dataContext
-                };
-
-                target.Bind(TreeView.ItemsProperty, new Binding("Items"));
-                target.Bind(TreeView.SelectedItemProperty, new Binding("SelectedItem"));
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-
-                var selectedValues = new List<object>();
-
-                dataContext.PropertyChanged += (_, e) =>
-                {
-                    if (e.PropertyName == nameof(TestDataContext.SelectedItem))
-                        selectedValues.Add(dataContext.SelectedItem);
-                };
-                selectedValues.Add(dataContext.SelectedItem);
-
-                _mouse.Click((Interactive)target.Presenter.Panel.Children[0], MouseButton.Left);
-                _mouse.Click((Interactive)target.Presenter.Panel.Children[2], MouseButton.Left);
-
-                Assert.Equal(3, selectedValues.Count);
-                Assert.Equal(new[] { null, "Item 0", "Item 2" }, selectedValues.ToArray());
-            }
-        }
-
-        [Fact]
-        public void LogicalChildren_Should_Be_Set()
-        {
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = new[] { "Foo", "Bar", "Baz " },
-            };
-
-            ApplyTemplates(target);
-
-            var result = target.GetLogicalChildren()
-                .OfType<TreeViewItem>()
-                .Select(x => x.Header)
-                .OfType<TextBlock>()
-                .Select(x => x.Text)
-                .ToList();
-
-            Assert.Equal(new[] { "Foo", "Bar", "Baz " }, result);
-        }
-
-        [Fact]
-        public void Removing_Item_Should_Remove_Itself_And_Children_From_Index()
-        {
-            var tree = CreateTestTreeData();
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = tree,
-            };
-
-            var root = new TestRoot();
-            root.Child = target;
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-
-            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
-
-            tree[0].Children.RemoveAt(1);
-
-            Assert.Equal(3, target.ItemContainerGenerator.Index.Containers.Count());
-        }
-
-        [Fact]
-        public void DataContexts_Should_Be_Correctly_Set()
-        {
-            var items = new object[]
-            {
-                "Foo",
-                new Node { Value = "Bar" },
-                new TextBlock { Text = "Baz" },
-                new TreeViewItem { Header = "Qux" },
-            };
-
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                DataContext = "Base",
-                DataTemplates =
-                {
-                    new FuncDataTemplate<Node>((x, _) => new Button { Content = x })
-                },
-                Items = items,
-            };
-
-            ApplyTemplates(target);
-
-            var dataContexts = target.Presenter.Panel.Children
-                .Cast<Control>()
-                .Select(x => x.DataContext)
-                .ToList();
-
-            Assert.Equal(
-                new object[] { items[0], items[1], "Base", "Base" },
-                dataContexts);
-        }
-
-        [Fact]
-        public void Control_Item_Should_Not_Be_NameScope()
-        {
-            var items = new object[]
-            {
-                new TreeViewItem(),
-            };
-
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = items,
-            };
-
-            target.ApplyTemplate();
-            target.Presenter.ApplyTemplate();
-
-            var item = target.Presenter.Panel.LogicalChildren[0];
-            Assert.Null(NameScope.GetNameScope((TreeViewItem)item));
-        }
-
-        [Fact]
-        public void Should_React_To_Children_Changing()
-        {
-            var data = CreateTestTreeData();
-
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = data,
-            };
-
-            var root = new TestRoot(target);
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-
-            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
-            Assert.Equal(new[] { "Child1", "Child2", "Child3" }, ExtractItemHeader(target, 1));
-            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
-
-            // Make sure that the binding to Node.Children does not get collected.
-            GC.Collect();
-
-            data[0].Children = new AvaloniaList<Node>
-            {
-                new Node
-                {
-                    Value = "NewChild1",
-                }
-            };
-
-            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
-            Assert.Equal(new[] { "NewChild1" }, ExtractItemHeader(target, 1));
-        }
-
-        [Fact]
-        public void Keyboard_Navigation_Should_Move_To_Last_Selected_Node()
-        {
-            using (Application())
-            {
-                var focus = FocusManager.Instance;
-                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
-                var data = CreateTestTreeData();
-
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = data,
-                };
-
-                var button = new Button();
-
-                var root = new TestRoot
-                {
-                    Child = new StackPanel
-                    {
-                        Children = { target, button },
-                    }
-                };
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var item = data[0].Children[0];
-                var node = target.ItemContainerGenerator.Index.ContainerFromItem(item);
-                Assert.NotNull(node);
-
-                target.SelectedItem = item;
-                node.Focus();
-                Assert.Same(node, focus.Current);
-
-                navigation.Move(focus.Current, NavigationDirection.Next);
-                Assert.Same(button, focus.Current);
-
-                navigation.Move(focus.Current, NavigationDirection.Next);
-                Assert.Same(node, focus.Current);
-            }
-        }
-
-        [Fact]
-        public void Keyboard_Navigation_Should_Not_Crash_If_Selected_Item_Is_not_In_Tree()
-        {
-            using (Application())
-            {
-                var focus = FocusManager.Instance;
-                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
-                var data = CreateTestTreeData();
-
-                var selectedNode = new Node { Value = "Out of Tree Selected Item" };
-
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = data,
-                    SelectedItem = selectedNode
-                };
-
-                var button = new Button();
-
-                var root = new TestRoot
-                {
-                    Child = new StackPanel
-                    {
-                        Children = { target, button },
-                    }
-                };
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var item = data[0].Children[0];
-                var node = target.ItemContainerGenerator.Index.ContainerFromItem(item);
-                Assert.NotNull(node);
-
-                target.SelectedItem = selectedNode;
-                node.Focus();
-                Assert.Same(node, focus.Current);
-
-                var next = KeyboardNavigationHandler.GetNext(node, NavigationDirection.Previous);
-            }
-        }
-
-        [Fact]
-        public void Pressing_SelectAll_Gesture_Should_Select_All_Nodes()
-        {
-            using (UnitTestApplication.Start())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var rootNode = tree[0];
-
-                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
-                var selectAllGesture = keymap.SelectAll.First();
-
-                var keyEvent = new KeyEventArgs
-                {
-                    RoutedEvent = InputElement.KeyDownEvent,
-                    Key = selectAllGesture.Key,
-                    KeyModifiers = selectAllGesture.KeyModifiers
-                };
-
-                target.RaiseEvent(keyEvent);
-
-                AssertChildrenSelected(target, rootNode);
-            }
-        }
-
-        [Fact]
-        public void Pressing_SelectAll_Gesture_With_Downward_Range_Selected_Should_Select_All_Nodes()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var rootNode = tree[0];
-
-                var from = rootNode.Children[0];
-                var to = rootNode.Children.Last();
-
-                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-                ClickContainer(fromContainer, KeyModifiers.None);
-                ClickContainer(toContainer, KeyModifiers.Shift);
-
-                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
-                var selectAllGesture = keymap.SelectAll.First();
-
-                var keyEvent = new KeyEventArgs
-                {
-                    RoutedEvent = InputElement.KeyDownEvent,
-                    Key = selectAllGesture.Key,
-                    KeyModifiers = selectAllGesture.KeyModifiers
-                };
-
-                target.RaiseEvent(keyEvent);
-
-                AssertChildrenSelected(target, rootNode);
-            }
-        }
-
-        [Fact]
-        public void Pressing_SelectAll_Gesture_With_Upward_Range_Selected_Should_Select_All_Nodes()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var rootNode = tree[0];
-
-                var from = rootNode.Children.Last();
-                var to = rootNode.Children[0];
-
-                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-                ClickContainer(fromContainer, KeyModifiers.None);
-                ClickContainer(toContainer, KeyModifiers.Shift);
-
-                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
-                var selectAllGesture = keymap.SelectAll.First();
-
-                var keyEvent = new KeyEventArgs
-                {
-                    RoutedEvent = InputElement.KeyDownEvent,
-                    Key = selectAllGesture.Key,
-                    KeyModifiers = selectAllGesture.KeyModifiers
-                };
-
-                target.RaiseEvent(keyEvent);
-
-                AssertChildrenSelected(target, rootNode);
-            }
-        }
-
-        [Fact]
-        public void Right_Click_On_SelectedItem_Should_Not_Clear_Existing_Selection()
-        {
-            using (UnitTestApplication.Start())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple,
-                };
-                AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
-                target.SelectAll();
-
-                AssertChildrenSelected(target, tree[0]);
-                Assert.Equal(5, target.SelectedItems.Count);
-
-                _mouse.Click((Interactive)target.Presenter.Panel.Children[0], MouseButton.Right);
-
-                Assert.Equal(5, target.SelectedItems.Count);
-            }
-        }
-
-        [Fact]
-        public void Right_Click_On_UnselectedItem_Should_Clear_Existing_Selection()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple,
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
-
-                var rootNode = tree[0];
-                var to = rootNode.Children[0];
-                var then = rootNode.Children[1];
-
-                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(rootNode);
-                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-                var thenContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(then);
-
-                ClickContainer(fromContainer, KeyModifiers.None);
-                ClickContainer(toContainer, KeyModifiers.Shift);
-
-                Assert.Equal(2, target.SelectedItems.Count);
-
-                _mouse.Click(thenContainer, MouseButton.Right);
-
-                Assert.Equal(1, target.SelectedItems.Count);
-            }
-        }
-
-        [Fact]
-        public void Shift_Right_Click_Should_Not_Select_Multiple()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple,
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
-
-                var rootNode = tree[0];
-                var from = rootNode.Children[0];
-                var to = rootNode.Children[1];
-                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-                _mouse.Click(fromContainer);
-                _mouse.Click(toContainer, MouseButton.Right, modifiers: KeyModifiers.Shift);
-
-                Assert.Equal(1, target.SelectedItems.Count);
-            }
-        }
-
-        [Fact]
-        public void Ctrl_Right_Click_Should_Not_Select_Multiple()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple,
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
-
-                var rootNode = tree[0];
-                var from = rootNode.Children[0];
-                var to = rootNode.Children[1];
-                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-                _mouse.Click(fromContainer);
-                _mouse.Click(toContainer, MouseButton.Right, modifiers: KeyModifiers.Control);
-
-                Assert.Equal(1, target.SelectedItems.Count);
-            }
-        }
-
-        [Fact]
-        public void TreeViewItems_Level_Should_Be_Set()
-        {
-            var tree = CreateTestTreeData();
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = tree,
-            };
-
-            var visualRoot = new TestRoot();
-            visualRoot.Child = target;
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-            ExpandAll(target);
-
-            Assert.Equal(0, GetItem(target, 0).Level);
-            Assert.Equal(1, GetItem(target, 0, 0).Level);
-            Assert.Equal(1, GetItem(target, 0, 1).Level);
-            Assert.Equal(1, GetItem(target, 0, 2).Level);
-            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
-        }
-
-        [Fact]
-        public void TreeViewItems_Level_Should_Be_Set_For_Derived_TreeView()
-        {
-            var tree = CreateTestTreeData();
-            var target = new DerivedTreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = tree,
-            };
-
-            var visualRoot = new TestRoot();
-            visualRoot.Child = target;
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-            ExpandAll(target);
-
-            Assert.Equal(0, GetItem(target, 0).Level);
-            Assert.Equal(1, GetItem(target, 0, 0).Level);
-            Assert.Equal(1, GetItem(target, 0, 1).Level);
-            Assert.Equal(1, GetItem(target, 0, 2).Level);
-            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
-        }
-
-        [Fact]
-        public void Adding_Node_To_Removed_And_ReAdded_Parent_Should_Not_Crash()
-        {
-            // Issue #2985
-            var tree = CreateTestTreeData();
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = tree,
-            };
-
-            var visualRoot = new TestRoot();
-            visualRoot.Child = target;
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-            ExpandAll(target);
-
-            var parent = tree[0];
-            var node = parent.Children[1];
-
-            parent.Children.Remove(node);
-            parent.Children.Add(node);
-
-            var item = target.ItemContainerGenerator.Index.ContainerFromItem(node);
-            ApplyTemplates(new[] { item });
-
-            // #2985 causes ArgumentException here.
-            node.Children.Add(new Node());
-        }
-
-        [Fact]
-        public void Auto_Expanding_In_Style_Should_Not_Break_Range_Selection()
-        {
-            // Issue #2980.
-            using (Application())
-            {
-                var target = new DerivedTreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    SelectionMode = SelectionMode.Multiple,
-                    Items = new List<Node>
-                {
-                    new Node { Value = "Root1", },
-                    new Node { Value = "Root2", },
-                },
-                };
-
-                var visualRoot = new TestRoot
-                {
-                    Styles =
-                    {
-                        new Style(x => x.OfType<TreeViewItem>())
-                        {
-                            Setters =
-                            {
-                                new Setter(TreeViewItem.IsExpandedProperty, true),
-                            },
-                        },
-                    },
-                    Child = target,
-                };
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-
-                _mouse.Click(GetItem(target, 0));
-                _mouse.Click(GetItem(target, 1), modifiers: KeyModifiers.Shift);
-            }
-        }
-
-        [Fact]
-        public void Removing_TreeView_From_Root_Should_Preserve_TreeViewItems()
-        {
-            // Issue #3328
-            var tree = CreateTestTreeData();
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = tree,
-            };
-
-            var root = new TestRoot();
-            root.Child = target;
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-            ExpandAll(target);
-
-            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
-
-            root.Child = null;
-
-            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
-            Assert.Equal(1, target.Presenter.Panel.Children.Count);
-
-            var rootNode = Assert.IsType<TreeViewItem>(target.Presenter.Panel.Children[0]);
-            Assert.Equal(3, rootNode.ItemContainerGenerator.Containers.Count());
-            Assert.Equal(3, rootNode.Presenter.Panel.Children.Count);
-
-            var child2Node = Assert.IsType<TreeViewItem>(rootNode.Presenter.Panel.Children[1]);
-            Assert.Equal(1, child2Node.ItemContainerGenerator.Containers.Count());
-            Assert.Equal(1, child2Node.Presenter.Panel.Children.Count);
-        }
-
-        [Fact]
-        public void Clearing_TreeView_Items_Clears_Index()
-        {
-            // Issue #3551
-            var tree = CreateTestTreeData();
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = tree,
-            };
-
-            var root = new TestRoot();
-            root.Child = target;
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-
-            var rootNode = tree[0];
-            var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(rootNode);
-
-            Assert.NotNull(container);
-
-            root.Child = null;
-
-            tree.Clear();
-
-            Assert.Empty(target.ItemContainerGenerator.Index.Containers);
-        }
-
-        [Fact]
-        public void Can_Use_Derived_TreeViewItem()
-        {
-            var tree = CreateTestTreeData();
-            var target = new DerivedTreeViewWithDerivedTreeViewItems
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = tree,
-            };
-
-            ApplyTemplates(target);
-
-            // Verify that all items are DerivedTreeViewItem
-            VerifyItemType(target.ItemContainerGenerator);
-
-            void VerifyItemType(ITreeItemContainerGenerator containerGenerator)
-            {
-                foreach (var container in containerGenerator.Index.Containers)
-                {
-                    var item = Assert.IsType<DerivedTreeViewItem>(container);
-                    if (item.ItemCount > 0)
-                    {
-                        VerifyItemType(item.ItemContainerGenerator);
-                    }
-                }
-            }
-        }
-
-        private void ApplyTemplates(TreeView tree)
-        {
-            tree.ApplyTemplate();
-            tree.Presenter.ApplyTemplate();
-            ApplyTemplates(tree.Presenter.Panel.Children);
-        }
-
-        private void ApplyTemplates(IEnumerable<Control> controls)
-        {
-            foreach (TreeViewItem control in controls)
-            {
-                control.Template = CreateTreeViewItemTemplate();
-                control.ApplyTemplate();
-                control.Presenter.ApplyTemplate();
-                control.HeaderPresenter.ApplyTemplate();
-                ApplyTemplates(control.Presenter.Panel.Children);
-            }
-        }
-
-        private TreeViewItem GetItem(TreeView target, params int[] indexes)
-        {
-            var c = (ItemsControl)target;
-
-            foreach (var index in indexes)
-            {
-                var item = ((IList)c.Items)[index];
-                c = (ItemsControl)target.ItemContainerGenerator.Index.ContainerFromItem(item);
-            }
-
-            return (TreeViewItem)c;
-        }
-
-        private IList<Node> CreateTestTreeData()
-        {
-            return new AvaloniaList<Node>
-            {
-                new Node
-                {
-                    Value = "Root",
-                    Children = new AvaloniaList<Node>
-                    {
-                        new Node
-                        {
-                            Value = "Child1",
-                        },
-                        new Node
-                        {
-                            Value = "Child2",
-                            Children = new AvaloniaList<Node>
-                            {
-                                new Node
-                                {
-                                    Value = "Grandchild2a",
-                                },
-                            },
-                        },
-                        new Node
-                        {
-                            Value = "Child3",
-                        }
-                    }
-                }
-            };
-        }
-
-        private void CreateNodeDataTemplate(Control control)
-        {
-            control.DataTemplates.Add(new TestTreeDataTemplate());
-        }
-
-        private IControlTemplate CreateTreeViewTemplate()
-        {
-            return new FuncControlTemplate<TreeView>((parent, scope) => new ItemsPresenter
-            {
-                Name = "PART_ItemsPresenter",
-            }.RegisterInNameScope(scope));
-        }
-
-        private IControlTemplate CreateTreeViewItemTemplate()
-        {
-            return new FuncControlTemplate<TreeViewItem>((parent, scope) => new Panel
-            {
-                Children =
-                {
-                    new ContentPresenter
-                    {
-                        Name = "PART_HeaderPresenter",
-                        [~ContentPresenter.ContentProperty] = parent[~TreeViewItem.HeaderProperty],
-                    }.RegisterInNameScope(scope),
-                    new ItemsPresenter
-                    {
-                        Name = "PART_ItemsPresenter",
-                    }.RegisterInNameScope(scope)
-                }
-            });
-        }
-
-        private void ExpandAll(TreeView tree)
-        {
-            foreach (var i in tree.ItemContainerGenerator.Containers)
-            {
-                tree.ExpandSubTree((TreeViewItem)i.ContainerControl);
-            }
-        }
-
-        private List<string> ExtractItemHeader(TreeView tree, int level)
-        {
-            return ExtractItemContent(tree.Presenter.Panel, 0, level)
-                .Select(x => x.Header)
-                .OfType<TextBlock>()
-                .Select(x => x.Text)
-                .ToList();
-        }
-
-        private IEnumerable<TreeViewItem> ExtractItemContent(Panel panel, int currentLevel, int level)
-        {
-            foreach (TreeViewItem container in panel.Children)
-            {
-                if (container.Template == null)
-                {
-                    container.Template = CreateTreeViewItemTemplate();
-                    container.ApplyTemplate();
-                }
-
-                if (currentLevel == level)
-                {
-                    yield return container;
-                }
-                else
-                {
-                    foreach (var child in ExtractItemContent(container.Presenter.Panel, currentLevel + 1, level))
-                    {
-                        yield return child;
-                    }
-                }
-            }
-        }
-
-        private void ClickContainer(Control container, KeyModifiers modifiers)
-        {
-            _mouse.Click(container, modifiers: modifiers);
-        }
-
-        private void AssertChildrenSelected(TreeView treeView, Node rootNode)
-        {
-            foreach (var child in rootNode.Children)
-            {
-                var container = (TreeViewItem)treeView.ItemContainerGenerator.Index.ContainerFromItem(child);
-
-                Assert.True(container.IsSelected);
-            }
-        }
-
-        private IDisposable Application()
-        {
-            return UnitTestApplication.Start(
-                TestServices.MockThreadingInterface.With(
-                    focusManager: new FocusManager(),
-                    keyboardDevice: () => new KeyboardDevice(),
-                    keyboardNavigation: new KeyboardNavigationHandler(),
-                    inputManager: new InputManager()));
-        }
-
-        private class Node : NotifyingBase
-        {
-            private IAvaloniaList<Node> _children;
-
-            public string Value { get; set; }
-
-            public IAvaloniaList<Node> Children
-            {
-                get
-                {
-                    return _children;
-                }
-
-                set
-                {
-                    _children = value;
-                    RaisePropertyChanged(nameof(Children));
-                }
-            }
-        }
-
-        private class TestTreeDataTemplate : ITreeDataTemplate
-        {
-            public Control Build(object param)
-            {
-                var node = (Node)param;
-                return new TextBlock { Text = node.Value };
-            }
-
-            public InstancedBinding ItemsSelector(object item)
-            {
-                var obs = ExpressionObserver.Create(item, o => (o as Node).Children);
-                return InstancedBinding.OneWay(obs);
-            }
-
-            public bool Match(object data)
-            {
-                return data is Node;
-            }
-        }
-
-        private class DerivedTreeView : TreeView
-        {
-        }
-
-        private class DerivedTreeViewWithDerivedTreeViewItems : TreeView
-        {
-            protected override ITreeItemContainerGenerator CreateTreeItemContainerGenerator() =>
-                CreateTreeItemContainerGenerator<DerivedTreeViewItem>();
-        }
-
-        private class DerivedTreeViewItem : TreeViewItem
-        {
-            protected override IItemContainerGenerator CreateItemContainerGenerator() => CreateTreeItemContainerGenerator<DerivedTreeViewItem>();
-        }
-
-        private class TestDataContext : INotifyPropertyChanged
-        {
-            private string _selectedItem;
-
-            public TestDataContext()
-            {
-                Items = new ObservableCollection<string>(Enumerable.Range(0, 5).Select(i => $"Item {i}"));
-            }
-
-            public ObservableCollection<string> Items { get; }
-
-            public string SelectedItem
-            {
-                get { return _selectedItem; }
-                set
-                {
-                    _selectedItem = value;
-                    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SelectedItem)));
-                }
-            }
-
-            public event PropertyChangedEventHandler PropertyChanged;
-
-        }
-    }
-}
+////        [Fact]
+////        public void Clicking_First_Item_Of_SelectedItems_Should_Select_Only_It()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var rootNode = tree[0];
+
+////                var from = rootNode.Children.Last();
+////                var to = rootNode.Children[0];
+
+////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
+////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+
+////                ClickContainer(fromContainer, KeyModifiers.None);
+
+////                ClickContainer(toContainer, KeyModifiers.Shift);
+////                AssertChildrenSelected(target, rootNode);
+
+////                ClickContainer(fromContainer, KeyModifiers.None);
+
+////                Assert.True(fromContainer.IsSelected);
+
+////                foreach (var child in rootNode.Children)
+////                {
+////                    if (child == from)
+////                    {
+////                        continue;
+////                    }
+
+////                    var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(child);
+
+////                    Assert.False(container.IsSelected);
+////                }
+////            }
+////        }
+
+////        [Fact]
+////        public void Setting_SelectedItem_Should_Set_Container_Selected()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var item = tree[0].Children[1].Children[0];
+////                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
+
+////                Assert.NotNull(container);
+
+////                target.SelectedItem = item;
+
+////                Assert.True(container.IsSelected);
+////            }
+////        }
+
+////        [Fact]
+////        public void Setting_SelectedItem_Should_Raise_SelectedItemChanged_Event()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var item = tree[0].Children[1].Children[0];
+
+////                var called = false;
+////                target.SelectionChanged += (s, e) =>
+////                {
+////                    Assert.Empty(e.RemovedItems);
+////                    Assert.Equal(1, e.AddedItems.Count);
+////                    Assert.Same(item, e.AddedItems[0]);
+////                    called = true;
+////                };
+
+////                target.SelectedItem = item;
+////                Assert.True(called);
+////            }
+////        }
+
+////        [Fact]
+////        public void Bound_SelectedItem_Should_Not_Be_Cleared_when_Changing_Selection()
+////        {
+////            using (Application())
+////            {
+////                var dataContext = new TestDataContext();
+
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    DataContext = dataContext
+////                };
+
+////                target.Bind(TreeView.ItemsProperty, new Binding("Items"));
+////                target.Bind(TreeView.SelectedItemProperty, new Binding("SelectedItem"));
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+
+////                var selectedValues = new List<object>();
+
+////                dataContext.PropertyChanged += (_, e) =>
+////                {
+////                    if (e.PropertyName == nameof(TestDataContext.SelectedItem))
+////                        selectedValues.Add(dataContext.SelectedItem);
+////                };
+////                selectedValues.Add(dataContext.SelectedItem);
+
+////                _mouse.Click((Interactive)target.Presenter.Panel.Children[0], MouseButton.Left);
+////                _mouse.Click((Interactive)target.Presenter.Panel.Children[2], MouseButton.Left);
+
+////                Assert.Equal(3, selectedValues.Count);
+////                Assert.Equal(new[] { null, "Item 0", "Item 2" }, selectedValues.ToArray());
+////            }
+////        }
+
+////        [Fact]
+////        public void LogicalChildren_Should_Be_Set()
+////        {
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = new[] { "Foo", "Bar", "Baz " },
+////            };
+
+////            ApplyTemplates(target);
+
+////            var result = target.GetLogicalChildren()
+////                .OfType<TreeViewItem>()
+////                .Select(x => x.Header)
+////                .OfType<TextBlock>()
+////                .Select(x => x.Text)
+////                .ToList();
+
+////            Assert.Equal(new[] { "Foo", "Bar", "Baz " }, result);
+////        }
+
+////        [Fact]
+////        public void Removing_Item_Should_Remove_Itself_And_Children_From_Index()
+////        {
+////            var tree = CreateTestTreeData();
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = tree,
+////            };
+
+////            var root = new TestRoot();
+////            root.Child = target;
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+
+////            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
+
+////            tree[0].Children.RemoveAt(1);
+
+////            Assert.Equal(3, target.ItemContainerGenerator.Index.Containers.Count());
+////        }
+
+////        [Fact]
+////        public void DataContexts_Should_Be_Correctly_Set()
+////        {
+////            var items = new object[]
+////            {
+////                "Foo",
+////                new Node { Value = "Bar" },
+////                new TextBlock { Text = "Baz" },
+////                new TreeViewItem { Header = "Qux" },
+////            };
+
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                DataContext = "Base",
+////                DataTemplates =
+////                {
+////                    new FuncDataTemplate<Node>((x, _) => new Button { Content = x })
+////                },
+////                Items = items,
+////            };
+
+////            ApplyTemplates(target);
+
+////            var dataContexts = target.Presenter.Panel.Children
+////                .Cast<Control>()
+////                .Select(x => x.DataContext)
+////                .ToList();
+
+////            Assert.Equal(
+////                new object[] { items[0], items[1], "Base", "Base" },
+////                dataContexts);
+////        }
+
+////        [Fact]
+////        public void Control_Item_Should_Not_Be_NameScope()
+////        {
+////            var items = new object[]
+////            {
+////                new TreeViewItem(),
+////            };
+
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = items,
+////            };
+
+////            target.ApplyTemplate();
+////            target.Presenter.ApplyTemplate();
+
+////            var item = target.Presenter.Panel.LogicalChildren[0];
+////            Assert.Null(NameScope.GetNameScope((TreeViewItem)item));
+////        }
+
+////        [Fact]
+////        public void Should_React_To_Children_Changing()
+////        {
+////            var data = CreateTestTreeData();
+
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = data,
+////            };
+
+////            var root = new TestRoot(target);
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+
+////            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
+////            Assert.Equal(new[] { "Child1", "Child2", "Child3" }, ExtractItemHeader(target, 1));
+////            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
+
+////            // Make sure that the binding to Node.Children does not get collected.
+////            GC.Collect();
+
+////            data[0].Children = new AvaloniaList<Node>
+////            {
+////                new Node
+////                {
+////                    Value = "NewChild1",
+////                }
+////            };
+
+////            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
+////            Assert.Equal(new[] { "NewChild1" }, ExtractItemHeader(target, 1));
+////        }
+
+////        [Fact]
+////        public void Keyboard_Navigation_Should_Move_To_Last_Selected_Node()
+////        {
+////            using (Application())
+////            {
+////                var focus = FocusManager.Instance;
+////                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
+////                var data = CreateTestTreeData();
+
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = data,
+////                };
+
+////                var button = new Button();
+
+////                var root = new TestRoot
+////                {
+////                    Child = new StackPanel
+////                    {
+////                        Children = { target, button },
+////                    }
+////                };
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var item = data[0].Children[0];
+////                var node = target.ItemContainerGenerator.Index.ContainerFromItem(item);
+////                Assert.NotNull(node);
+
+////                target.SelectedItem = item;
+////                node.Focus();
+////                Assert.Same(node, focus.Current);
+
+////                navigation.Move(focus.Current, NavigationDirection.Next);
+////                Assert.Same(button, focus.Current);
+
+////                navigation.Move(focus.Current, NavigationDirection.Next);
+////                Assert.Same(node, focus.Current);
+////            }
+////        }
+
+////        [Fact]
+////        public void Keyboard_Navigation_Should_Not_Crash_If_Selected_Item_Is_not_In_Tree()
+////        {
+////            using (Application())
+////            {
+////                var focus = FocusManager.Instance;
+////                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
+////                var data = CreateTestTreeData();
+
+////                var selectedNode = new Node { Value = "Out of Tree Selected Item" };
+
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = data,
+////                    SelectedItem = selectedNode
+////                };
+
+////                var button = new Button();
+
+////                var root = new TestRoot
+////                {
+////                    Child = new StackPanel
+////                    {
+////                        Children = { target, button },
+////                    }
+////                };
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var item = data[0].Children[0];
+////                var node = target.ItemContainerGenerator.Index.ContainerFromItem(item);
+////                Assert.NotNull(node);
+
+////                target.SelectedItem = selectedNode;
+////                node.Focus();
+////                Assert.Same(node, focus.Current);
+
+////                var next = KeyboardNavigationHandler.GetNext(node, NavigationDirection.Previous);
+////            }
+////        }
+
+////        [Fact]
+////        public void Pressing_SelectAll_Gesture_Should_Select_All_Nodes()
+////        {
+////            using (UnitTestApplication.Start())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var rootNode = tree[0];
+
+////                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
+////                var selectAllGesture = keymap.SelectAll.First();
+
+////                var keyEvent = new KeyEventArgs
+////                {
+////                    RoutedEvent = InputElement.KeyDownEvent,
+////                    Key = selectAllGesture.Key,
+////                    KeyModifiers = selectAllGesture.KeyModifiers
+////                };
+
+////                target.RaiseEvent(keyEvent);
+
+////                AssertChildrenSelected(target, rootNode);
+////            }
+////        }
+
+////        [Fact]
+////        public void Pressing_SelectAll_Gesture_With_Downward_Range_Selected_Should_Select_All_Nodes()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var rootNode = tree[0];
+
+////                var from = rootNode.Children[0];
+////                var to = rootNode.Children.Last();
+
+////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
+////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+
+////                ClickContainer(fromContainer, KeyModifiers.None);
+////                ClickContainer(toContainer, KeyModifiers.Shift);
+
+////                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
+////                var selectAllGesture = keymap.SelectAll.First();
+
+////                var keyEvent = new KeyEventArgs
+////                {
+////                    RoutedEvent = InputElement.KeyDownEvent,
+////                    Key = selectAllGesture.Key,
+////                    KeyModifiers = selectAllGesture.KeyModifiers
+////                };
+
+////                target.RaiseEvent(keyEvent);
+
+////                AssertChildrenSelected(target, rootNode);
+////            }
+////        }
+
+////        [Fact]
+////        public void Pressing_SelectAll_Gesture_With_Upward_Range_Selected_Should_Select_All_Nodes()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var rootNode = tree[0];
+
+////                var from = rootNode.Children.Last();
+////                var to = rootNode.Children[0];
+
+////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
+////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+
+////                ClickContainer(fromContainer, KeyModifiers.None);
+////                ClickContainer(toContainer, KeyModifiers.Shift);
+
+////                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
+////                var selectAllGesture = keymap.SelectAll.First();
+
+////                var keyEvent = new KeyEventArgs
+////                {
+////                    RoutedEvent = InputElement.KeyDownEvent,
+////                    Key = selectAllGesture.Key,
+////                    KeyModifiers = selectAllGesture.KeyModifiers
+////                };
+
+////                target.RaiseEvent(keyEvent);
+
+////                AssertChildrenSelected(target, rootNode);
+////            }
+////        }
+
+////        [Fact]
+////        public void Right_Click_On_SelectedItem_Should_Not_Clear_Existing_Selection()
+////        {
+////            using (UnitTestApplication.Start())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple,
+////                };
+////                AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
+////                target.SelectAll();
+
+////                AssertChildrenSelected(target, tree[0]);
+////                Assert.Equal(5, target.SelectedItems.Count);
+
+////                _mouse.Click((Interactive)target.Presenter.Panel.Children[0], MouseButton.Right);
+
+////                Assert.Equal(5, target.SelectedItems.Count);
+////            }
+////        }
+
+////        [Fact]
+////        public void Right_Click_On_UnselectedItem_Should_Clear_Existing_Selection()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple,
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
+
+////                var rootNode = tree[0];
+////                var to = rootNode.Children[0];
+////                var then = rootNode.Children[1];
+
+////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(rootNode);
+////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+////                var thenContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(then);
+
+////                ClickContainer(fromContainer, KeyModifiers.None);
+////                ClickContainer(toContainer, KeyModifiers.Shift);
+
+////                Assert.Equal(2, target.SelectedItems.Count);
+
+////                _mouse.Click(thenContainer, MouseButton.Right);
+
+////                Assert.Equal(1, target.SelectedItems.Count);
+////            }
+////        }
+
+////        [Fact]
+////        public void Shift_Right_Click_Should_Not_Select_Multiple()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple,
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
+
+////                var rootNode = tree[0];
+////                var from = rootNode.Children[0];
+////                var to = rootNode.Children[1];
+////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
+////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+
+////                _mouse.Click(fromContainer);
+////                _mouse.Click(toContainer, MouseButton.Right, modifiers: KeyModifiers.Shift);
+
+////                Assert.Equal(1, target.SelectedItems.Count);
+////            }
+////        }
+
+////        [Fact]
+////        public void Ctrl_Right_Click_Should_Not_Select_Multiple()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple,
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
+
+////                var rootNode = tree[0];
+////                var from = rootNode.Children[0];
+////                var to = rootNode.Children[1];
+////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
+////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+
+////                _mouse.Click(fromContainer);
+////                _mouse.Click(toContainer, MouseButton.Right, modifiers: KeyModifiers.Control);
+
+////                Assert.Equal(1, target.SelectedItems.Count);
+////            }
+////        }
+
+////        [Fact]
+////        public void TreeViewItems_Level_Should_Be_Set()
+////        {
+////            var tree = CreateTestTreeData();
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = tree,
+////            };
+
+////            var visualRoot = new TestRoot();
+////            visualRoot.Child = target;
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+////            ExpandAll(target);
+
+////            Assert.Equal(0, GetItem(target, 0).Level);
+////            Assert.Equal(1, GetItem(target, 0, 0).Level);
+////            Assert.Equal(1, GetItem(target, 0, 1).Level);
+////            Assert.Equal(1, GetItem(target, 0, 2).Level);
+////            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
+////        }
+
+////        [Fact]
+////        public void TreeViewItems_Level_Should_Be_Set_For_Derived_TreeView()
+////        {
+////            var tree = CreateTestTreeData();
+////            var target = new DerivedTreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = tree,
+////            };
+
+////            var visualRoot = new TestRoot();
+////            visualRoot.Child = target;
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+////            ExpandAll(target);
+
+////            Assert.Equal(0, GetItem(target, 0).Level);
+////            Assert.Equal(1, GetItem(target, 0, 0).Level);
+////            Assert.Equal(1, GetItem(target, 0, 1).Level);
+////            Assert.Equal(1, GetItem(target, 0, 2).Level);
+////            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
+////        }
+
+////        [Fact]
+////        public void Adding_Node_To_Removed_And_ReAdded_Parent_Should_Not_Crash()
+////        {
+////            // Issue #2985
+////            var tree = CreateTestTreeData();
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = tree,
+////            };
+
+////            var visualRoot = new TestRoot();
+////            visualRoot.Child = target;
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+////            ExpandAll(target);
+
+////            var parent = tree[0];
+////            var node = parent.Children[1];
+
+////            parent.Children.Remove(node);
+////            parent.Children.Add(node);
+
+////            var item = target.ItemContainerGenerator.Index.ContainerFromItem(node);
+////            ApplyTemplates(new[] { item });
+
+////            // #2985 causes ArgumentException here.
+////            node.Children.Add(new Node());
+////        }
+
+////        [Fact]
+////        public void Auto_Expanding_In_Style_Should_Not_Break_Range_Selection()
+////        {
+////            // Issue #2980.
+////            using (Application())
+////            {
+////                var target = new DerivedTreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    SelectionMode = SelectionMode.Multiple,
+////                    Items = new List<Node>
+////                {
+////                    new Node { Value = "Root1", },
+////                    new Node { Value = "Root2", },
+////                },
+////                };
+
+////                var visualRoot = new TestRoot
+////                {
+////                    Styles =
+////                    {
+////                        new Style(x => x.OfType<TreeViewItem>())
+////                        {
+////                            Setters =
+////                            {
+////                                new Setter(TreeViewItem.IsExpandedProperty, true),
+////                            },
+////                        },
+////                    },
+////                    Child = target,
+////                };
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+
+////                _mouse.Click(GetItem(target, 0));
+////                _mouse.Click(GetItem(target, 1), modifiers: KeyModifiers.Shift);
+////            }
+////        }
+
+////        [Fact]
+////        public void Removing_TreeView_From_Root_Should_Preserve_TreeViewItems()
+////        {
+////            // Issue #3328
+////            var tree = CreateTestTreeData();
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = tree,
+////            };
+
+////            var root = new TestRoot();
+////            root.Child = target;
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+////            ExpandAll(target);
+
+////            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
+
+////            root.Child = null;
+
+////            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
+////            Assert.Equal(1, target.Presenter.Panel.Children.Count);
+
+////            var rootNode = Assert.IsType<TreeViewItem>(target.Presenter.Panel.Children[0]);
+////            Assert.Equal(3, rootNode.ItemContainerGenerator.Containers.Count());
+////            Assert.Equal(3, rootNode.Presenter.Panel.Children.Count);
+
+////            var child2Node = Assert.IsType<TreeViewItem>(rootNode.Presenter.Panel.Children[1]);
+////            Assert.Equal(1, child2Node.ItemContainerGenerator.Containers.Count());
+////            Assert.Equal(1, child2Node.Presenter.Panel.Children.Count);
+////        }
+
+////        [Fact]
+////        public void Clearing_TreeView_Items_Clears_Index()
+////        {
+////            // Issue #3551
+////            var tree = CreateTestTreeData();
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = tree,
+////            };
+
+////            var root = new TestRoot();
+////            root.Child = target;
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+
+////            var rootNode = tree[0];
+////            var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(rootNode);
+
+////            Assert.NotNull(container);
+
+////            root.Child = null;
+
+////            tree.Clear();
+
+////            Assert.Empty(target.ItemContainerGenerator.Index.Containers);
+////        }
+
+////        [Fact]
+////        public void Can_Use_Derived_TreeViewItem()
+////        {
+////            var tree = CreateTestTreeData();
+////            var target = new DerivedTreeViewWithDerivedTreeViewItems
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = tree,
+////            };
+
+////            ApplyTemplates(target);
+
+////            // Verify that all items are DerivedTreeViewItem
+////            VerifyItemType(target.ItemContainerGenerator);
+
+////            void VerifyItemType(ITreeItemContainerGenerator containerGenerator)
+////            {
+////                foreach (var container in containerGenerator.Index.Containers)
+////                {
+////                    var item = Assert.IsType<DerivedTreeViewItem>(container);
+////                    if (item.ItemCount > 0)
+////                    {
+////                        VerifyItemType(item.ItemContainerGenerator);
+////                    }
+////                }
+////            }
+////        }
+
+////        private void ApplyTemplates(TreeView tree)
+////        {
+////            tree.ApplyTemplate();
+////            tree.Presenter.ApplyTemplate();
+////            ApplyTemplates(tree.Presenter.Panel.Children);
+////        }
+
+////        private void ApplyTemplates(IEnumerable<Control> controls)
+////        {
+////            foreach (TreeViewItem control in controls)
+////            {
+////                control.Template = CreateTreeViewItemTemplate();
+////                control.ApplyTemplate();
+////                control.Presenter.ApplyTemplate();
+////                control.HeaderPresenter.ApplyTemplate();
+////                ApplyTemplates(control.Presenter.Panel.Children);
+////            }
+////        }
+
+////        private TreeViewItem GetItem(TreeView target, params int[] indexes)
+////        {
+////            var c = (ItemsControl)target;
+
+////            foreach (var index in indexes)
+////            {
+////                var item = ((IList)c.Items)[index];
+////                c = (ItemsControl)target.ItemContainerGenerator.Index.ContainerFromItem(item);
+////            }
+
+////            return (TreeViewItem)c;
+////        }
+
+////        private IList<Node> CreateTestTreeData()
+////        {
+////            return new AvaloniaList<Node>
+////            {
+////                new Node
+////                {
+////                    Value = "Root",
+////                    Children = new AvaloniaList<Node>
+////                    {
+////                        new Node
+////                        {
+////                            Value = "Child1",
+////                        },
+////                        new Node
+////                        {
+////                            Value = "Child2",
+////                            Children = new AvaloniaList<Node>
+////                            {
+////                                new Node
+////                                {
+////                                    Value = "Grandchild2a",
+////                                },
+////                            },
+////                        },
+////                        new Node
+////                        {
+////                            Value = "Child3",
+////                        }
+////                    }
+////                }
+////            };
+////        }
+
+////        private void CreateNodeDataTemplate(Control control)
+////        {
+////            control.DataTemplates.Add(new TestTreeDataTemplate());
+////        }
+
+////        private IControlTemplate CreateTreeViewTemplate()
+////        {
+////            return new FuncControlTemplate<TreeView>((parent, scope) => new ItemsPresenter
+////            {
+////                Name = "PART_ItemsPresenter",
+////            }.RegisterInNameScope(scope));
+////        }
+
+////        private IControlTemplate CreateTreeViewItemTemplate()
+////        {
+////            return new FuncControlTemplate<TreeViewItem>((parent, scope) => new Panel
+////            {
+////                Children =
+////                {
+////                    new ContentPresenter
+////                    {
+////                        Name = "PART_HeaderPresenter",
+////                        [~ContentPresenter.ContentProperty] = parent[~TreeViewItem.HeaderProperty],
+////                    }.RegisterInNameScope(scope),
+////                    new ItemsPresenter
+////                    {
+////                        Name = "PART_ItemsPresenter",
+////                    }.RegisterInNameScope(scope)
+////                }
+////            });
+////        }
+
+////        private void ExpandAll(TreeView tree)
+////        {
+////            foreach (var i in tree.ItemContainerGenerator.Containers)
+////            {
+////                tree.ExpandSubTree((TreeViewItem)i.ContainerControl);
+////            }
+////        }
+
+////        private List<string> ExtractItemHeader(TreeView tree, int level)
+////        {
+////            return ExtractItemContent(tree.Presenter.Panel, 0, level)
+////                .Select(x => x.Header)
+////                .OfType<TextBlock>()
+////                .Select(x => x.Text)
+////                .ToList();
+////        }
+
+////        private IEnumerable<TreeViewItem> ExtractItemContent(Panel panel, int currentLevel, int level)
+////        {
+////            foreach (TreeViewItem container in panel.Children)
+////            {
+////                if (container.Template == null)
+////                {
+////                    container.Template = CreateTreeViewItemTemplate();
+////                    container.ApplyTemplate();
+////                }
+
+////                if (currentLevel == level)
+////                {
+////                    yield return container;
+////                }
+////                else
+////                {
+////                    foreach (var child in ExtractItemContent(container.Presenter.Panel, currentLevel + 1, level))
+////                    {
+////                        yield return child;
+////                    }
+////                }
+////            }
+////        }
+
+////        private void ClickContainer(Control container, KeyModifiers modifiers)
+////        {
+////            _mouse.Click(container, modifiers: modifiers);
+////        }
+
+////        private void AssertChildrenSelected(TreeView treeView, Node rootNode)
+////        {
+////            foreach (var child in rootNode.Children)
+////            {
+////                var container = (TreeViewItem)treeView.ItemContainerGenerator.Index.ContainerFromItem(child);
+
+////                Assert.True(container.IsSelected);
+////            }
+////        }
+
+////        private IDisposable Application()
+////        {
+////            return UnitTestApplication.Start(
+////                TestServices.MockThreadingInterface.With(
+////                    focusManager: new FocusManager(),
+////                    keyboardDevice: () => new KeyboardDevice(),
+////                    keyboardNavigation: new KeyboardNavigationHandler(),
+////                    inputManager: new InputManager()));
+////        }
+
+////        private class Node : NotifyingBase
+////        {
+////            private IAvaloniaList<Node> _children;
+
+////            public string Value { get; set; }
+
+////            public IAvaloniaList<Node> Children
+////            {
+////                get
+////                {
+////                    return _children;
+////                }
+
+////                set
+////                {
+////                    _children = value;
+////                    RaisePropertyChanged(nameof(Children));
+////                }
+////            }
+////        }
+
+////        private class TestTreeDataTemplate : ITreeDataTemplate
+////        {
+////            public Control Build(object param)
+////            {
+////                var node = (Node)param;
+////                return new TextBlock { Text = node.Value };
+////            }
+
+////            public InstancedBinding ItemsSelector(object item)
+////            {
+////                var obs = ExpressionObserver.Create(item, o => (o as Node).Children);
+////                return InstancedBinding.OneWay(obs);
+////            }
+
+////            public bool Match(object data)
+////            {
+////                return data is Node;
+////            }
+////        }
+
+////        private class DerivedTreeView : TreeView
+////        {
+////        }
+
+////        private class DerivedTreeViewWithDerivedTreeViewItems : TreeView
+////        {
+////            protected override ITreeItemContainerGenerator CreateTreeItemContainerGenerator() =>
+////                CreateTreeItemContainerGenerator<DerivedTreeViewItem>();
+////        }
+
+////        private class DerivedTreeViewItem : TreeViewItem
+////        {
+////            protected override IItemContainerGenerator CreateItemContainerGenerator() => CreateTreeItemContainerGenerator<DerivedTreeViewItem>();
+////        }
+
+////        private class TestDataContext : INotifyPropertyChanged
+////        {
+////            private string _selectedItem;
+
+////            public TestDataContext()
+////            {
+////                Items = new ObservableCollection<string>(Enumerable.Range(0, 5).Select(i => $"Item {i}"));
+////            }
+
+////            public ObservableCollection<string> Items { get; }
+
+////            public string SelectedItem
+////            {
+////                get { return _selectedItem; }
+////                set
+////                {
+////                    _selectedItem = value;
+////                    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SelectedItem)));
+////                }
+////            }
+
+////            public event PropertyChangedEventHandler PropertyChanged;
+
+////        }
+////    }
+////}
diff --git a/tests/Avalonia.LeakTests/ControlTests.cs b/tests/Avalonia.LeakTests/ControlTests.cs
index 9170c68e115..f46ad446842 100644
--- a/tests/Avalonia.LeakTests/ControlTests.cs
+++ b/tests/Avalonia.LeakTests/ControlTests.cs
@@ -361,7 +361,8 @@ public void TreeView_Is_Freed()
 
                     // Do a layout and make sure that TreeViewItems get realized.
                     window.LayoutManager.ExecuteInitialLayoutPass();
-                    Assert.Single(target.ItemContainerGenerator.Containers);
+                    throw new NotImplementedException();
+                    ////Assert.Single(target.ItemContainerGenerator.Containers);
 
                     // Clear the content and ensure the TreeView is removed.
                     window.Content = null;
@@ -756,20 +757,22 @@ public void ElementName_Binding_In_DataTemplate_Is_Freed()
                 window.Show();
                 window.LayoutManager.ExecuteInitialLayoutPass();
 
-                void AssertInitialItemState()
-                {
-                    var item0 = (ListBoxItem)lb.ItemContainerGenerator.Containers.First().ContainerControl;
-                    var canvas0 = (Canvas)item0.Presenter.Child;
-                    Assert.Equal("foo", canvas0.Tag);
-                }
+                throw new NotImplementedException();
+
+                ////void AssertInitialItemState()
+                ////{
+                ////    var item0 = (ListBoxItem)lb.ItemContainerGenerator.Containers.First().ContainerControl;
+                ////    var canvas0 = (Canvas)item0.Presenter.Child;
+                ////    Assert.Equal("foo", canvas0.Tag);
+                ////}
                
-                Assert.Equal(10, lb.ItemContainerGenerator.Containers.Count());
-                AssertInitialItemState();
+                ////Assert.Equal(10, lb.ItemContainerGenerator.Containers.Count());
+                ////AssertInitialItemState();
 
-                items.Clear();
-                window.LayoutManager.ExecuteLayoutPass();
+                ////items.Clear();
+                ////window.LayoutManager.ExecuteLayoutPass();
 
-                Assert.Empty(lb.ItemContainerGenerator.Containers);
+                ////Assert.Empty(lb.ItemContainerGenerator.Containers);
 
                 // Process all Loaded events to free control reference(s)
                 Dispatcher.UIThread.RunJobs(DispatcherPriority.Loaded);

From 57b1ba965cb40bcfd7b724fba51fec2614d61cc2 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 28 Nov 2022 23:17:11 +0100
Subject: [PATCH 05/64] Implement INavigableContainer.

---
 src/Avalonia.Controls/VirtualizingPanel.cs    | 22 +++++-
 .../VirtualizingStackPanel.cs                 | 70 ++++++++++++++++++-
 2 files changed, 87 insertions(+), 5 deletions(-)

diff --git a/src/Avalonia.Controls/VirtualizingPanel.cs b/src/Avalonia.Controls/VirtualizingPanel.cs
index dd40f868d5d..87c630658f6 100644
--- a/src/Avalonia.Controls/VirtualizingPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingPanel.cs
@@ -3,13 +3,14 @@
 using System.Collections.Specialized;
 using System.Diagnostics.CodeAnalysis;
 using Avalonia.Controls.Utils;
+using Avalonia.Input;
 
 namespace Avalonia.Controls
 {
     /// <summary>
     /// Base class for panels that can be used to virtualize items.
     /// </summary>
-    public abstract class VirtualizingPanel : Panel
+    public abstract class VirtualizingPanel : Panel, INavigableContainer
     {
         private ItemsControl? _itemsControl;
 
@@ -27,11 +28,19 @@ private set
             }
         }
 
+        IInputElement? INavigableContainer.GetControl(NavigationDirection direction, IInputElement? from, bool wrap)
+        {
+            return GetControl(direction, from, wrap);
+        }
+
         /// <summary>
         /// Scrolls the specified item into view.
         /// </summary>
         /// <param name="index">The index of the item.</param>
-        protected internal abstract void ScrollIntoView(int index);
+        /// <returns>
+        /// The element with the specified index, or null if the element could not be brought into view.
+        /// </returns>
+        protected internal abstract Control? ScrollIntoView(int index);
 
         /// <summary>
         /// Returns the container for the item at the specified index.
@@ -53,6 +62,15 @@ private set
         /// </returns>
         protected internal abstract int IndexFromContainer(Control container);
 
+        /// <summary>
+        /// Gets the next control in the specified direction.
+        /// </summary>
+        /// <param name="direction">The movement direction.</param>
+        /// <param name="from">The control from which movement begins.</param>
+        /// <param name="wrap">Whether to wrap around when the first or last item is reached.</param>
+        /// <returns>The control.</returns>
+        protected abstract IInputElement? GetControl(NavigationDirection direction, IInputElement? from, bool wrap);
+
         /// <summary>
         /// Called when the <see cref="ItemsControl"/> that owns the panel changes.
         /// </summary>
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index a4e287dc087..2e80edd6bb4 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -3,8 +3,8 @@
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Diagnostics;
-using System.Xml.Linq;
 using Avalonia.Controls.Utils;
+using Avalonia.Input;
 using Avalonia.Layout;
 using Avalonia.Utilities;
 using Avalonia.VisualTree;
@@ -169,19 +169,79 @@ protected override void OnItemsChanged(IList items, NotifyCollectionChangedEvent
             InvalidateMeasure();
         }
 
+        protected override IInputElement? GetControl(NavigationDirection direction, IInputElement? from, bool wrap)
+        {
+            var count = (ItemsControl?.Items as IList)?.Count ?? 0;
+
+            if (count == 0)
+                return null;
+
+            var horiz = Orientation == Orientation.Horizontal;
+            var fromIndex = from != null ? Children.IndexOf(from) : -1;
+            var toIndex = fromIndex;
+
+            switch (direction)
+            {
+                case NavigationDirection.First:
+                    toIndex = 0;
+                    break;
+                case NavigationDirection.Last:
+                    toIndex = count - 1;
+                    break;
+                case NavigationDirection.Next:
+                    ++toIndex;
+                    break;
+                case NavigationDirection.Previous:
+                    --toIndex;
+                    break;
+                case NavigationDirection.Left:
+                    if (horiz)
+                        --toIndex;
+                    break;
+                case NavigationDirection.Right:
+                    if (horiz)
+                        ++toIndex;
+                    break;
+                case NavigationDirection.Up:
+                    if (!horiz)
+                        --toIndex;
+                    break;
+                case NavigationDirection.Down:
+                    if (!horiz)
+                        ++toIndex;
+                    break;
+                default:
+                    return null;
+            }
+
+            if (fromIndex == toIndex)
+                return from;
+
+            if (wrap)
+            {
+                if (toIndex < 0)
+                    toIndex = count - 1;
+                else if (toIndex >= count - 1)
+                    toIndex = 0;
+            }
+
+            return ScrollIntoView(toIndex);
+        }
+
         protected internal override Control? ContainerFromIndex(int index) => _realizedElements?.GetElement(index);
         protected internal override int IndexFromContainer(Control container) => _realizedElements?.GetIndex(container) ?? -1;
 
-        protected internal override void ScrollIntoView(int index)
+        protected internal override Control? ScrollIntoView(int index)
         {
             var items = ItemsControl?.Items as IList;
 
             if (_isInLayout || items is null || index < 0 || index >= items.Count)
-                return;
+                return null;
 
             if (GetRealizedElement(index) is Control element)
             {
                 element.BringIntoView();
+                return element;
             }
             else if (this.GetVisualRoot() is ILayoutRoot root)
             {
@@ -216,9 +276,13 @@ protected internal override void ScrollIntoView(int index)
                 root.LayoutManager.ExecuteLayoutPass();
                 _isWaitingForViewportUpdate = false;
 
+                var result = _anchorElement;
                 _anchorElement = null;
                 _anchorIndex = -1;
+                return result;
             }
+
+            return null;
         }
 
         internal IReadOnlyList<Control?> GetRealizedElements()

From e07e5cead56c41ee3c14ca3f874eeb1a88d59ead Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 30 Nov 2022 00:16:55 +0100
Subject: [PATCH 06/64] Fix container generation logic.

---
 .../Presenters/PanelContainerGenerator.cs     | 21 ++++++++-----------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index f1765ba9862..ea6276feb45 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -66,7 +66,10 @@ void Add(int index, IEnumerable items)
             {
                 var i = index;
                 foreach (var item in items)
-                    panel.Children.Insert(i++, CreateContainer(itemsControl, item, i));
+                {
+                    panel.Children.Insert(i, CreateContainer(itemsControl, item, i));
+                    ++i;
+                }
             }
             
             void Remove(int index, int count)
@@ -106,18 +109,12 @@ void Remove(int index, int count)
         private static Control CreateContainer(ItemsControl itemsControl, object? item, int index)
         {
             var generator = itemsControl.ItemContainerGenerator;
+            var container = item is Control c && generator.IsItemItsOwnContainer(c) ?
+                c : generator.CreateContainer();
 
-            if (item is Control c && generator.IsItemItsOwnContainer(c))
-            {
-                return c;
-            }
-            else
-            {
-                c = generator.CreateContainer();
-                itemsControl.AddLogicalChild(c);
-                generator.PrepareItemContainer(c, item, index);
-                return c;
-            }
+            itemsControl.AddLogicalChild(container);
+            generator.PrepareItemContainer(container, item, index);
+            return container;
         }
     }
 }

From a1d809b49dbceb8aa07b3205387a64d436db212f Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 30 Nov 2022 00:17:29 +0100
Subject: [PATCH 07/64] Fix VirtualizingStackPanel navigation logic.

---
 src/Avalonia.Controls/VirtualizingStackPanel.cs | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 2e80edd6bb4..1016a0af59a 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -173,11 +173,11 @@ protected override void OnItemsChanged(IList items, NotifyCollectionChangedEvent
         {
             var count = (ItemsControl?.Items as IList)?.Count ?? 0;
 
-            if (count == 0)
+            if (count == 0 || from is not Control fromControl)
                 return null;
 
             var horiz = Orientation == Orientation.Horizontal;
-            var fromIndex = from != null ? Children.IndexOf(from) : -1;
+            var fromIndex = from != null ? IndexFromContainer(fromControl) : -1;
             var toIndex = fromIndex;
 
             switch (direction)
@@ -708,7 +708,10 @@ public bool TryGetElementU(int modelIndex, out double position)
             /// </summary>
             /// <param name="element">The element.</param>
             /// <returns>The model index or -1 if the element is not present in the collection.</returns>
-            public int GetIndex(Control element) => _elements?.IndexOf(element) is int index && index >= 0 ? index : -1;
+            public int GetIndex(Control element)
+            {
+                return _elements?.IndexOf(element) is int index && index >= 0 ? index + FirstModelIndex : -1;
+            }
 
             /// <summary>
             /// Updates the elements in response to items being inserted into the source collection.

From b3982f18281a01d820564dada9fde55ba624d96c Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 30 Nov 2022 00:17:59 +0100
Subject: [PATCH 08/64] Create correct TabControl containers.

---
 src/Avalonia.Controls/TabControl.cs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/Avalonia.Controls/TabControl.cs b/src/Avalonia.Controls/TabControl.cs
index 8ce1befde55..970d7de727a 100644
--- a/src/Avalonia.Controls/TabControl.cs
+++ b/src/Avalonia.Controls/TabControl.cs
@@ -165,6 +165,9 @@ bool IContentPresenterHost.RegisterContentPresenter(IContentPresenter presenter)
             return RegisterContentPresenter(presenter);
         }
 
+        protected internal override Control CreateContainerOverride() => new TabItem();
+        protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is TabItem;
+
         protected internal override void PrepareContainerForItemOverride(Control element, object? item, int index)
         {
             base.PrepareContainerForItemOverride(element, item, index);

From fab8f15213b3c120ec4e9e029f4212f5a7205909 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 30 Nov 2022 00:18:07 +0100
Subject: [PATCH 09/64] Make a few more tests pass.

---
 .../Primitives/SelectingItemsControlTests.cs           | 10 +++++++++-
 tests/Avalonia.Controls.UnitTests/TabControlTests.cs   |  2 --
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
index d89e88b2ba8..dbea9f79b80 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
@@ -16,11 +16,13 @@
 using Avalonia.Input;
 using Avalonia.Input.Platform;
 using Avalonia.Interactivity;
+using Avalonia.Layout;
 using Avalonia.Markup.Data;
 using Avalonia.Platform;
 using Avalonia.Styling;
 using Avalonia.Threading;
 using Avalonia.UnitTests;
+using Avalonia.VisualTree;
 using Moq;
 using Xunit;
 
@@ -1488,9 +1490,10 @@ public void AutoScrollToSelectedItem_On_Reset_Works()
 
                 // #3148 triggered here.
                 items.Reset(new[] { "Item99" });
+                Layout(target);
 
                 Assert.Equal(0, target.SelectedIndex);
-                Assert.Equal(1, target.Presenter.Panel.Children.Count);
+                Assert.Equal(1, target.Presenter.Panel.Children.Where(x => x.IsVisible).Count());
             }
         }
 
@@ -2083,6 +2086,11 @@ private static void Prepare(SelectingItemsControl target)
             root.LayoutManager.ExecuteInitialLayoutPass();
         }
 
+        private static void Layout(Control c)
+        {
+            ((ILayoutRoot)c.GetVisualRoot()).LayoutManager.ExecuteLayoutPass();
+        }
+
         private static FuncControlTemplate Template()
         {
             return new FuncControlTemplate<SelectingItemsControl>((control, scope) =>
diff --git a/tests/Avalonia.Controls.UnitTests/TabControlTests.cs b/tests/Avalonia.Controls.UnitTests/TabControlTests.cs
index 3dcbb6caca6..4c5397db601 100644
--- a/tests/Avalonia.Controls.UnitTests/TabControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TabControlTests.cs
@@ -431,8 +431,6 @@ private static IControlTemplate TabControlTemplate()
                         new ItemsPresenter
                         {
                             Name = "PART_ItemsPresenter",
-                            [!TabStrip.ItemsProperty] = parent[!TabControl.ItemsProperty],
-                            [!TabStrip.ItemTemplateProperty] = parent[!TabControl.ItemTemplateProperty],
                         }.RegisterInNameScope(scope),
                         new ContentPresenter
                         {

From 14d429ec4eca994998c995753bcf2a45f5ed914b Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 30 Nov 2022 00:18:48 +0100
Subject: [PATCH 10/64] Added ItemsControl.GetRealizedContainers().

---
 src/Avalonia.Controls/ItemsControl.cs         |  5 ++
 src/Avalonia.Controls/MenuItem.cs             | 11 +---
 .../Presenters/ItemsPresenter.cs              | 10 ++++
 .../Primitives/SelectingItemsControl.cs       | 59 +++++++++----------
 src/Avalonia.Controls/VirtualizingPanel.cs    |  6 ++
 .../VirtualizingStackPanel.cs                 |  6 ++
 tests/Avalonia.LeakTests/ControlTests.cs      | 27 ++++-----
 7 files changed, 69 insertions(+), 55 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index c4356e29675..e56cad15b89 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -211,6 +211,11 @@ event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexCh
             throw new NotImplementedException();
         }
 
+        /// <summary>
+        /// Gets the currently realized containers.
+        /// </summary>
+        public IEnumerable<Control> GetRealizedContainers() => Presenter?.GetRealizedContainers() ?? Array.Empty<Control>();
+
         /// <inheritdoc/>
         void IItemsPresenterHost.RegisterItemsPresenter(ItemsPresenter presenter)
         {
diff --git a/src/Avalonia.Controls/MenuItem.cs b/src/Avalonia.Controls/MenuItem.cs
index d134704b26a..dd336974ca2 100644
--- a/src/Avalonia.Controls/MenuItem.cs
+++ b/src/Avalonia.Controls/MenuItem.cs
@@ -328,16 +328,7 @@ public bool StaysOpenOnClick
         }
 
         /// <inheritdoc/>
-        IEnumerable<IMenuItem> IMenuElement.SubItems
-        {
-            get
-            {
-                throw new NotImplementedException();
-                ////return ItemContainerGenerator.Containers
-                ////    .Select(x => x.ContainerControl)
-                ////    .OfType<IMenuItem>();
-            }
-        }
+        IEnumerable<IMenuItem> IMenuElement.SubItems => GetRealizedContainers().OfType<IMenuItem>();
 
         /// <summary>
         /// Opens the submenu.
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
index 5f90c264d7f..6f27349cc14 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
@@ -1,5 +1,8 @@
 using System;
+using System.Collections;
+using System.Collections.Generic;
 using System.Diagnostics;
+using System.Reflection;
 
 namespace Avalonia.Controls.Presenters
 {
@@ -109,6 +112,13 @@ private void CreateSimplePanelGenerator()
             return index >= 0 && index < Panel?.Children.Count ? Panel.Children[index] : null;
         }
 
+        internal IEnumerable<Control>? GetRealizedContainers()
+        {
+            if (Panel is VirtualizingPanel v)
+                return v.GetRealizedContainers();
+            return Panel?.Children;
+        }
+
         internal int IndexFromContainer(Control container)
         {
             if (Panel is VirtualizingPanel v)
diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index 1503da1322e..a49705d7542 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -507,45 +507,44 @@ protected override void OnInitialized()
 
         protected override void OnTextInput(TextInputEventArgs e)
         {
-            throw new NotImplementedException();
-            ////if (!e.Handled)
-            ////{
-            ////    if (!IsTextSearchEnabled)
-            ////        return;
+            if (!e.Handled)
+            {
+                if (!IsTextSearchEnabled)
+                    return;
 
-            ////    StopTextSearchTimer();
+                StopTextSearchTimer();
 
-            ////    _textSearchTerm += e.Text;
+                _textSearchTerm += e.Text;
 
-            ////    bool Match(ItemContainerInfo info)
-            ////    {
-            ////        if (info.ContainerControl is AvaloniaObject ao && ao.IsSet(TextSearch.TextProperty))
-            ////        {
-            ////            var searchText = ao.GetValue(TextSearch.TextProperty);
+                bool Match(Control container)
+                {
+                    if (container is AvaloniaObject ao && ao.IsSet(TextSearch.TextProperty))
+                    {
+                        var searchText = ao.GetValue(TextSearch.TextProperty);
 
-            ////            if (searchText?.StartsWith(_textSearchTerm, StringComparison.OrdinalIgnoreCase) == true)
-            ////            {
-            ////                return true;
-            ////            }
-            ////        }
+                        if (searchText?.StartsWith(_textSearchTerm, StringComparison.OrdinalIgnoreCase) == true)
+                        {
+                            return true;
+                        }
+                    }
 
-            ////        return info.ContainerControl is IContentControl control &&
-            ////               control.Content?.ToString()?.StartsWith(_textSearchTerm, StringComparison.OrdinalIgnoreCase) == true;
-            ////    }
-                
-            ////    var info = ItemContainerGenerator?.Containers.FirstOrDefault(Match);
+                    return container is IContentControl control &&
+                           control.Content?.ToString()?.StartsWith(_textSearchTerm, StringComparison.OrdinalIgnoreCase) == true;
+                }
 
-            ////    if (info != null)
-            ////    {
-            ////        SelectedIndex = info.Index;
-            ////    }
+                var container = GetRealizedContainers().FirstOrDefault(Match);
 
-            ////    StartTextSearchTimer();
+                if (container != null)
+                {
+                    SelectedIndex = IndexFromContainer(container);
+                }
 
-            ////    e.Handled = true;
-            ////}
+                StartTextSearchTimer();
+
+                e.Handled = true;
+            }
 
-            ////base.OnTextInput(e);
+            base.OnTextInput(e);
         }
 
         protected override void OnKeyDown(KeyEventArgs e)
diff --git a/src/Avalonia.Controls/VirtualizingPanel.cs b/src/Avalonia.Controls/VirtualizingPanel.cs
index 87c630658f6..0b7a183728d 100644
--- a/src/Avalonia.Controls/VirtualizingPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingPanel.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections;
+using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Diagnostics.CodeAnalysis;
 using Avalonia.Controls.Utils;
@@ -62,6 +63,11 @@ private set
         /// </returns>
         protected internal abstract int IndexFromContainer(Control container);
 
+        /// <summary>
+        /// Gets the currently realized containers.
+        /// </summary>
+        protected internal abstract IEnumerable<Control>? GetRealizedContainers();
+
         /// <summary>
         /// Gets the next control in the specified direction.
         /// </summary>
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 1016a0af59a..76cbf94f09f 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -3,6 +3,7 @@
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Diagnostics;
+using System.Linq;
 using Avalonia.Controls.Utils;
 using Avalonia.Input;
 using Avalonia.Layout;
@@ -228,6 +229,11 @@ protected override void OnItemsChanged(IList items, NotifyCollectionChangedEvent
             return ScrollIntoView(toIndex);
         }
 
+        protected internal override IEnumerable<Control>? GetRealizedContainers()
+        {
+            return _realizedElements?.Elements.Where(x => x is not null)!;
+        }
+
         protected internal override Control? ContainerFromIndex(int index) => _realizedElements?.GetElement(index);
         protected internal override int IndexFromContainer(Control container) => _realizedElements?.GetIndex(container) ?? -1;
 
diff --git a/tests/Avalonia.LeakTests/ControlTests.cs b/tests/Avalonia.LeakTests/ControlTests.cs
index f46ad446842..4433e25c5a6 100644
--- a/tests/Avalonia.LeakTests/ControlTests.cs
+++ b/tests/Avalonia.LeakTests/ControlTests.cs
@@ -361,8 +361,7 @@ public void TreeView_Is_Freed()
 
                     // Do a layout and make sure that TreeViewItems get realized.
                     window.LayoutManager.ExecuteInitialLayoutPass();
-                    throw new NotImplementedException();
-                    ////Assert.Single(target.ItemContainerGenerator.Containers);
+                    Assert.Single(target.GetRealizedContainers());
 
                     // Clear the content and ensure the TreeView is removed.
                     window.Content = null;
@@ -757,22 +756,20 @@ public void ElementName_Binding_In_DataTemplate_Is_Freed()
                 window.Show();
                 window.LayoutManager.ExecuteInitialLayoutPass();
 
-                throw new NotImplementedException();
+                void AssertInitialItemState()
+                {
+                    var item0 = (ListBoxItem)lb.GetRealizedContainers().First();
+                    var canvas0 = (Canvas)item0.Presenter.Child;
+                    Assert.Equal("foo", canvas0.Tag);
+                }
 
-                ////void AssertInitialItemState()
-                ////{
-                ////    var item0 = (ListBoxItem)lb.ItemContainerGenerator.Containers.First().ContainerControl;
-                ////    var canvas0 = (Canvas)item0.Presenter.Child;
-                ////    Assert.Equal("foo", canvas0.Tag);
-                ////}
-               
-                ////Assert.Equal(10, lb.ItemContainerGenerator.Containers.Count());
-                ////AssertInitialItemState();
+                Assert.Equal(10, lb.GetRealizedContainers().Count());
+                AssertInitialItemState();
 
-                ////items.Clear();
-                ////window.LayoutManager.ExecuteLayoutPass();
+                items.Clear();
+                window.LayoutManager.ExecuteLayoutPass();
 
-                ////Assert.Empty(lb.ItemContainerGenerator.Containers);
+                Assert.Empty(lb.GetRealizedContainers());
 
                 // Process all Loaded events to free control reference(s)
                 Dispatcher.UIThread.RunJobs(DispatcherPriority.Loaded);

From bbd3d2a500a977983680cdacbfed84577f12075b Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 30 Nov 2022 17:43:25 +0100
Subject: [PATCH 11/64] Only remove generated logical children.

---
 src/Avalonia.Controls/ItemsControl.cs         |  1 -
 .../Presenters/PanelContainerGenerator.cs     | 35 ++++++++++++++++---
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index e56cad15b89..b7a63811c43 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -456,7 +456,6 @@ protected virtual void ItemsCollectionChanged(object sender, NotifyCollectionCha
 
         internal void AddLogicalChild(Control c) => LogicalChildren.Add(c);
         internal void RemoveLogicalChild(Control c) => LogicalChildren.Remove(c);
-        internal void ClearLogicalChildren() => LogicalChildren.Clear();
 
         internal void PrepareItemContainer(Control container, object? item, int index)
         {
diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index ea6276feb45..56e1901117f 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -11,6 +11,9 @@ namespace Avalonia.Controls.Presenters
     /// </summary>
     internal class PanelContainerGenerator : IDisposable
     {
+        private static readonly AttachedProperty<bool> ItemIsOwnContainerProperty =
+            AvaloniaProperty.RegisterAttached<PanelContainerGenerator, Control, bool>("ItemIsOwnContainer");
+
         private readonly ItemsPresenter _presenter;
 
         public PanelContainerGenerator(ItemsPresenter presenter)
@@ -36,7 +39,7 @@ public void Dispose()
                 if (itemsControl.Items is INotifyCollectionChanged incc)
                     incc.CollectionChanged -= OnItemsChanged;
 
-                itemsControl.ClearLogicalChildren();
+                ClearItemsControlLogicalChildren();
             }
 
             _presenter.Panel?.Children.Clear();
@@ -98,7 +101,7 @@ void Remove(int index, int count)
                     Add(e.NewStartingIndex, e.NewItems!);
                     break;
                 case NotifyCollectionChangedAction.Reset:
-                    itemsControl.ClearLogicalChildren();
+                    ClearItemsControlLogicalChildren();
                     panel.Children.Clear();
                     if (_presenter.ItemsControl?.Items is { } items)
                         Add(0, items);
@@ -109,12 +112,36 @@ void Remove(int index, int count)
         private static Control CreateContainer(ItemsControl itemsControl, object? item, int index)
         {
             var generator = itemsControl.ItemContainerGenerator;
-            var container = item is Control c && generator.IsItemItsOwnContainer(c) ?
-                c : generator.CreateContainer();
+            Control container;
+            
+            if (item is Control c && generator.IsItemItsOwnContainer(c))
+            {
+                container = c;
+                container.SetValue(ItemIsOwnContainerProperty, true);
+            }
+            else
+            {
+                container = generator.CreateContainer();
+            }
 
             itemsControl.AddLogicalChild(container);
             generator.PrepareItemContainer(container, item, index);
             return container;
         }
+
+        private void ClearItemsControlLogicalChildren()
+        {
+            if (_presenter.Panel is null || _presenter.ItemsControl is null)
+                return;
+
+            var itemsControl = _presenter.ItemsControl;
+            var panel = _presenter.Panel;
+
+            foreach (var c in panel.Children)
+            {
+                if (!c.IsSet(ItemIsOwnContainerProperty))
+                    itemsControl.RemoveLogicalChild(c);
+            }
+        }
     }
 }

From a9ca85230002e7c88299da447209f1d1ee531475 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 30 Nov 2022 23:29:06 +0100
Subject: [PATCH 12/64] Notify ItemsControl when container index changes.

---
 .../Generators/ItemContainerGenerator.cs      | 10 +++++++
 src/Avalonia.Controls/ItemsControl.cs         | 16 +++++++++++
 .../Presenters/PanelContainerGenerator.cs     | 27 ++++++++++++++-----
 .../Primitives/SelectingItemsControl.cs       |  6 +++++
 .../VirtualizingStackPanel.cs                 | 22 +++++++++------
 5 files changed, 67 insertions(+), 14 deletions(-)

diff --git a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
index 0598bb1a63b..1cf40d335fa 100644
--- a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
+++ b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
@@ -56,6 +56,16 @@ public class ItemContainerGenerator
         public void PrepareItemContainer(Control container, object? item, int index) => 
             _owner.PrepareItemContainer(container, item, index);
 
+        /// <summary>
+        /// Called when the index for a container changes due to an insertion or removal in the
+        /// items collection.
+        /// </summary>
+        /// <param name="container">The container whose index changed.</param>
+        /// <param name="oldIndex">The old index.</param>
+        /// <param name="newIndex">The new index.</param>
+        public void ItemContainerIndexChanged(Control container, int oldIndex, int newIndex) =>
+            _owner.ItemContainerIndexChanged(container, oldIndex, newIndex);
+
         /// <summary>
         /// Undoes the effects of the <see cref="PrepareItemContainer(Control, object, int)"/> method.
         /// </summary>
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index b7a63811c43..7c24717a06c 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -298,6 +298,17 @@ protected internal virtual void PrepareContainerForItemOverride(Control containe
                 container.SetValue(ThemeProperty, ItemContainerTheme, BindingPriority.Template);
         }
 
+        /// <summary>
+        /// Called when the index for a container changes due to an insertion or removal in the
+        /// items collection.
+        /// </summary>
+        /// <param name="container">The container whose index changed.</param>
+        /// <param name="oldIndex">The old index.</param>
+        /// <param name="newIndex">The new index.</param>
+        protected virtual void ContainerIndexChangedOverride(Control container, int oldIndex, int newIndex)
+        {
+        }
+
         /// <summary>
         /// Undoes the effects of the <see cref="PrepareContainerForItemOverride(Control, object?, int)"/> method.
         /// </summary>
@@ -474,6 +485,11 @@ internal void PrepareItemContainer(Control container, object? item, int index)
             PrepareContainerForItemOverride(container, item, index);
         }
 
+        internal void ItemContainerIndexChanged(Control container, int oldIndex, int newIndex)
+        {
+            ContainerIndexChangedOverride(container, oldIndex, newIndex);
+        }
+
         /// <summary>
         /// Given a collection of items, adds those that are controls to the logical children.
         /// </summary>
diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index 56e1901117f..4a31017fbdc 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -63,25 +63,40 @@ private void OnItemsChanged(object? sender, NotifyCollectionChangedEventArgs e)
                 return;
 
             var itemsControl = _presenter.ItemsControl;
-            var panel = _presenter.Panel;
+            var generator = itemsControl.ItemContainerGenerator;
+            var children = _presenter.Panel.Children;
 
             void Add(int index, IEnumerable items)
             {
                 var i = index;
                 foreach (var item in items)
                 {
-                    panel.Children.Insert(i, CreateContainer(itemsControl, item, i));
+                    children.Insert(i, CreateContainer(itemsControl, item, i));
                     ++i;
                 }
+
+                var childCount = children.Count;
+                var delta = i - index;
+
+                for (; i < childCount; ++i)
+                    generator.ItemContainerIndexChanged(children[i], i - delta, i);
             }
-            
+
             void Remove(int index, int count)
             {
                 for (var i = 0; i < count; ++i)
                 {
-                    itemsControl.RemoveLogicalChild(panel.Children[i + index]);
-                    panel.Children.RemoveAt(i + index);
+                    var c = children[i];
+                    if (!c.IsSet(ItemIsOwnContainerProperty))
+                        itemsControl.RemoveLogicalChild(children[i + index]);
                 }
+
+                children.RemoveRange(index, count);
+
+                var childCount = children.Count;
+
+                for (var i = index; i < childCount; ++i)
+                    generator.ItemContainerIndexChanged(children[i], i - count, i);
             }
 
             switch (e.Action)
@@ -102,7 +117,7 @@ void Remove(int index, int count)
                     break;
                 case NotifyCollectionChangedAction.Reset:
                     ClearItemsControlLogicalChildren();
-                    panel.Children.Clear();
+                    children.Clear();
                     if (_presenter.ItemsControl?.Items is { } items)
                         Add(0, items);
                     break;
diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index a49705d7542..253726c5aaa 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -449,6 +449,12 @@ protected internal override void PrepareContainerForItemOverride(Control element
             }
         }
 
+        protected override void ContainerIndexChangedOverride(Control container, int oldIndex, int newIndex)
+        {
+            base.ContainerIndexChangedOverride(container, oldIndex, newIndex);
+            MarkContainerSelected(container, Selection.IsSelected(newIndex));
+        }
+
         protected internal override void ClearContainerForItemOverride(Control element)
         {
             base.ClearContainerForItemOverride(element);
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 76cbf94f09f..6373d5f3bd4 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -25,7 +25,7 @@ public class VirtualizingStackPanel : VirtualizingPanel
 
         private static readonly Rect s_invalidViewport = new(double.PositiveInfinity, double.PositiveInfinity, 0, 0);
         private readonly Action<Control> _recycleElement;
-        private readonly Action<Control, int> _updateElementIndex;
+        private readonly Action<Control, int, int> _updateElementIndex;
         private int _anchorIndex = -1;
         private Control? _anchorElement;
         private bool _isInLayout;
@@ -513,9 +513,9 @@ private void RecycleElement(Control element)
             }
         }
 
-        private void UpdateElementIndex(Control element, int index)
+        private void UpdateElementIndex(Control element, int oldIndex, int newIndex)
         {
-            // TODO: Implement this after we refactor ItemContainerGenerator.
+            ItemsControl!.ItemContainerGenerator.ItemContainerIndexChanged(element, oldIndex, newIndex);
         }
 
         private void OnEffectiveViewportChanged(object? sender, EffectiveViewportChangedEventArgs e)
@@ -725,7 +725,7 @@ public int GetIndex(Control element)
             /// <param name="modelIndex">The index in the source collection of the insert.</param>
             /// <param name="count">The number of items inserted.</param>
             /// <param name="updateElementIndex">A method used to update the element indexes.</param>
-            public void ItemsInserted(int modelIndex, int count, Action<Control, int> updateElementIndex)
+            public void ItemsInserted(int modelIndex, int count, Action<Control, int, int> updateElementIndex)
             {
                 if (modelIndex < 0)
                     throw new ArgumentOutOfRangeException(nameof(modelIndex));
@@ -742,11 +742,13 @@ public void ItemsInserted(int modelIndex, int count, Action<Control, int> update
                     // elements after the insertion point.
                     var elementCount = _elements.Count;
                     var start = Math.Max(index, 0);
+                    var newIndex = first + count;
 
                     for (var i = start; i < elementCount; ++i)
                     {
                         if (_elements[i] is Control element)
-                            updateElementIndex(element, first + i + count);
+                            updateElementIndex(element, newIndex - count, newIndex);
+                        ++newIndex;
                     }
 
                     if (index <= 0)
@@ -774,7 +776,7 @@ public void ItemsInserted(int modelIndex, int count, Action<Control, int> update
             public void ItemsRemoved(
                 int modelIndex,
                 int count,
-                Action<Control, int> updateElementIndex,
+                Action<Control, int, int> updateElementIndex,
                 Action<Control> recycleElement)
             {
                 if (modelIndex < 0)
@@ -794,10 +796,12 @@ public void ItemsRemoved(
                     // the indexes of the realized elements.
                     _firstIndex -= count;
 
+                    var newIndex = _firstIndex;
                     for (var i = 0; i < _elements.Count; ++i)
                     {
                         if (_elements[i] is Control element)
-                            updateElementIndex(element, _firstIndex + i);
+                            updateElementIndex(element, newIndex - count, newIndex);
+                        ++newIndex;
                     }
                 }
                 else if (startIndex < _elements.Count)
@@ -822,10 +826,12 @@ public void ItemsRemoved(
 
                     // Update the indexes of the elements after the removed range.
                     end = _elements.Count;
+                    var newIndex = first;
                     for (var i = start; i < end; ++i)
                     {
                         if (_elements[i] is Control element)
-                            updateElementIndex(element, first + i);
+                            updateElementIndex(element, newIndex - count, newIndex);
+                        ++newIndex;
                     }
                 }
             }

From c1ee26c05a0b6c70749775dd69918cd8ddc52d75 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 00:20:22 +0100
Subject: [PATCH 13/64] Fixed SelectingItemsControlTests.

`ListBox` now needs a root as it uses a `VirtualizingStackPanel`.
---
 .../SelectingItemsControlTests_Multiple.cs    | 136 ++++++++++++------
 1 file changed, 96 insertions(+), 40 deletions(-)

diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
index efce0a715c8..0b72baf3369 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
@@ -710,14 +710,16 @@ public void Shift_Selecting_From_No_Selection_Selects_From_Start()
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
                 _helper.Click((Interactive)target.Presenter.Panel.Children[2], modifiers: KeyModifiers.Shift);
 
-                var panel = target.Presenter.Panel;
-
                 Assert.Equal(new[] { "Foo", "Bar", "Baz" }, target.SelectedItems);
                 Assert.Equal(new[] { 0, 1, 2 }, SelectedContainers(target));
             }
@@ -733,10 +735,14 @@ public void Ctrl_Selecting_Raises_SelectionChanged_Events()
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz", "Qux" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
 
                 SelectionChangedEventArgs receivedArgs = null;
 
@@ -787,10 +793,14 @@ public void Ctrl_Selecting_SelectedItem_With_Multiple_Selection_Active_Sets_Sele
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz", "Qux" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
                 _helper.Click((Interactive)target.Presenter.Panel.Children[1]);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[2], modifiers: KeyModifiers.Control);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[3], modifiers: KeyModifiers.Control);
@@ -817,11 +827,14 @@ public void Ctrl_Selecting_Non_SelectedItem_With_Multiple_Selection_Active_Leave
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
-                AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
 
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
+                AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[1]);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[2], modifiers: KeyModifiers.Control);
 
@@ -845,10 +858,14 @@ public void Should_Ctrl_Select_Correct_Item_When_Duplicate_Items_Are_Present()
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
                 _helper.Click((Interactive)target.Presenter.Panel.Children[3]);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[4], modifiers: KeyModifiers.Control);
 
@@ -869,10 +886,14 @@ public void Should_Shift_Select_Correct_Item_When_Duplicates_Are_Present()
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
                 _helper.Click((Interactive)target.Presenter.Panel.Children[3]);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[5], modifiers: KeyModifiers.Shift);
 
@@ -893,10 +914,14 @@ public void Can_Shift_Select_All_Items_When_Duplicates_Are_Present()
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
                 _helper.Click((Interactive)target.Presenter.Panel.Children[0]);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[5], modifiers: KeyModifiers.Shift);
 
@@ -917,10 +942,13 @@ public void Shift_Selecting_Raises_SelectionChanged_Events()
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz", "Qux" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
 
                 SelectionChangedEventArgs receivedArgs = null;
 
@@ -966,11 +994,14 @@ public void Duplicate_Items_Are_Added_To_SelectedItems_In_Order()
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
 
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
                 _helper.Click((Interactive)target.Presenter.Panel.Children[0]);
 
                 Assert.Equal(new[] { "Foo" }, target.SelectedItems);
@@ -1084,13 +1115,16 @@ public void Adding_Item_Before_SelectedItems_Should_Update_Selection()
                 Template = Template(),
                 Items = items,
                 SelectionMode = SelectionMode.Multiple,
+                Width = 100,
+                Height = 100,
             };
 
-            target.ApplyTemplate();
-            target.Presenter.ApplyTemplate();
+            var root = new TestRoot(target);
+            root.LayoutManager.ExecuteInitialLayoutPass();
 
             target.SelectAll();
             items.Insert(0, "Qux");
+            root.LayoutManager.ExecuteLayoutPass();
 
             Assert.Equal(1, target.SelectedIndex);
             Assert.Equal("Foo", target.SelectedItem);
@@ -1146,10 +1180,12 @@ public void Removing_SelectedItem_With_Multiple_Selection_Active_Should_Update_S
                 Template = Template(),
                 Items = items,
                 SelectionMode = SelectionMode.Multiple,
+                Width = 100,
+                Height = 100,
             };
 
-            target.ApplyTemplate();
-            target.Presenter.ApplyTemplate();
+            var root = new TestRoot(target);
+            root.LayoutManager.ExecuteInitialLayoutPass();
 
             target.SelectAll();
             items.RemoveAt(0);
@@ -1175,10 +1211,12 @@ public void Replacing_Selected_Item_Should_Update_SelectedItems()
                 Template = Template(),
                 Items = items,
                 SelectionMode = SelectionMode.Multiple,
+                Width = 100,
+                Height = 100,
             };
 
-            target.ApplyTemplate();
-            target.Presenter.ApplyTemplate();
+            var root = new TestRoot(target);
+            root.LayoutManager.ExecuteInitialLayoutPass();
 
             target.SelectAll();
             items[1] = "Qux";
@@ -1197,10 +1235,13 @@ public void Left_Click_On_SelectedItem_Should_Clear_Existing_Selection()
                     Items = new[] { "Foo", "Bar", "Baz" },
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
-                AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 target.SelectAll();
 
                 Assert.Equal(3, target.SelectedItems.Count);
@@ -1224,10 +1265,13 @@ public void Right_Click_On_SelectedItem_Should_Not_Clear_Existing_Selection()
                     Items = new[] { "Foo", "Bar", "Baz" },
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
-                AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 target.SelectAll();
 
                 Assert.Equal(3, target.SelectedItems.Count);
@@ -1249,10 +1293,14 @@ public void Right_Click_On_UnselectedItem_Should_Clear_Existing_Selection()
                     Items = new[] { "Foo", "Bar", "Baz" },
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
                 _helper.Click((Interactive)target.Presenter.Panel.Children[0]);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[1], modifiers: KeyModifiers.Shift);
 
@@ -1301,10 +1349,14 @@ public void Shift_Right_Click_Should_Not_Select_Multiple()
                     Items = new[] { "Foo", "Bar", "Baz" },
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
 
                 _helper.Click((Interactive)target.Presenter.Panel.Children[0]);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[2], MouseButton.Right, modifiers: KeyModifiers.Shift);
@@ -1324,10 +1376,14 @@ public void Ctrl_Right_Click_Should_Not_Select_Multiple()
                     Items = new[] { "Foo", "Bar", "Baz" },
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
 
                 _helper.Click((Interactive)target.Presenter.Panel.Children[0]);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[2], MouseButton.Right, modifiers: KeyModifiers.Control);
@@ -1526,7 +1582,7 @@ public void Assigning_Selection_Should_Raise_SelectionChanged()
         private static IEnumerable<int> SelectedContainers(SelectingItemsControl target)
         {
             return target.Presenter.Panel.Children
-                .Select((x, i) => x.Classes.Contains(":selected") ? i : -1)
+                .Select(x => x.Classes.Contains(":selected") ? target.IndexFromContainer(x) : -1)
                 .Where(x => x != -1);
         }
 

From 6626a2e2182ae09d33c2c495f8b07019b96468d5 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 10:33:44 +0100
Subject: [PATCH 14/64] Update TabControl on container index change.

---
 .../Presenters/PanelContainerGenerator.cs              |  2 +-
 src/Avalonia.Controls/TabControl.cs                    | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index 4a31017fbdc..b080a9044f0 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -96,7 +96,7 @@ void Remove(int index, int count)
                 var childCount = children.Count;
 
                 for (var i = index; i < childCount; ++i)
-                    generator.ItemContainerIndexChanged(children[i], i - count, i);
+                    generator.ItemContainerIndexChanged(children[i], i + count, i);
             }
 
             switch (e.Action)
diff --git a/src/Avalonia.Controls/TabControl.cs b/src/Avalonia.Controls/TabControl.cs
index 970d7de727a..d08e0a61da4 100644
--- a/src/Avalonia.Controls/TabControl.cs
+++ b/src/Avalonia.Controls/TabControl.cs
@@ -174,6 +174,16 @@ protected internal override void PrepareContainerForItemOverride(Control element
             UpdateSelectedContent();
         }
 
+        protected override void ContainerIndexChangedOverride(Control container, int oldIndex, int newIndex)
+        {
+            base.ContainerIndexChangedOverride(container, oldIndex, newIndex);
+
+            var selectedIndex = SelectedIndex;
+            
+            if (selectedIndex == oldIndex || selectedIndex == newIndex)
+                UpdateSelectedContent();
+        }
+
         protected internal override void ClearContainerForItemOverride(Control element)
         {
             base.ClearContainerForItemOverride(element);

From 8bb1349785fa3f68a920ccfc63936e378c4b0a93 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 11:31:01 +0100
Subject: [PATCH 15/64] Setup TabItems.

---
 src/Avalonia.Controls/ItemsControl.cs | 25 +++++++++++++++++--------
 src/Avalonia.Controls/TabControl.cs   | 10 +++++++++-
 2 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 7c24717a06c..3de40171904 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -281,21 +281,30 @@ protected internal virtual void PrepareContainerForItemOverride(Control containe
             if (container == item)
                 return;
 
-            if (container is ContentControl cc)
+            if (container is HeaderedContentControl hcc)
             {
-                cc.SetValue(ContentControl.ContentProperty, item, BindingPriority.Template);
+                hcc.Content = item;
+
+                if (item is IHeadered headered)
+                    hcc.Header = headered.Header;
+                else if (item is not Visual)
+                    hcc.Header = item;
+
+                if (ItemTemplate is { } it)
+                    hcc.HeaderTemplate = it;
+            }
+            else if (container is ContentControl cc)
+            {
+                cc.Content = item;
                 if (ItemTemplate is { } it)
-                    cc.SetValue(ContentControl.ContentTemplateProperty, it, BindingPriority.Template);
+                    cc.ContentTemplate = it;
             }
             else if (container is ContentPresenter p)
             {
-                p.SetValue(ContentPresenter.ContentProperty, item, BindingPriority.Template);
+                p.Content = item;
                 if (ItemTemplate is { } it)
-                    p.SetValue(ContentPresenter.ContentTemplateProperty, it, BindingPriority.Template);
+                    p.ContentTemplate = it;
             }
-
-            if (ItemContainerTheme is not null)
-                container.SetValue(ThemeProperty, ItemContainerTheme, BindingPriority.Template);
         }
 
         /// <summary>
diff --git a/src/Avalonia.Controls/TabControl.cs b/src/Avalonia.Controls/TabControl.cs
index d08e0a61da4..952a9e448ce 100644
--- a/src/Avalonia.Controls/TabControl.cs
+++ b/src/Avalonia.Controls/TabControl.cs
@@ -171,7 +171,15 @@ bool IContentPresenterHost.RegisterContentPresenter(IContentPresenter presenter)
         protected internal override void PrepareContainerForItemOverride(Control element, object? item, int index)
         {
             base.PrepareContainerForItemOverride(element, item, index);
-            UpdateSelectedContent();
+            
+            if (element is HeaderedContentControl hcc && ContentTemplate is { } ct)
+                hcc.ContentTemplate = ct;
+
+            if (index == SelectedIndex && element is ContentControl container)
+            {
+                SelectedContentTemplate = container.ContentTemplate;
+                SelectedContent = container.Content;
+            }
         }
 
         protected override void ContainerIndexChangedOverride(Control container, int oldIndex, int newIndex)

From 2c4572a98eb1288b7e17bfb5c041dc0ea65a2f3b Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 11:54:44 +0100
Subject: [PATCH 16/64] Attach to panel before preparing container.

---
 src/Avalonia.Controls/ItemsControl.cs               |  9 +++++++++
 .../Presenters/PanelContainerGenerator.cs           | 13 +++++++------
 src/Avalonia.Controls/VirtualizingStackPanel.cs     |  2 +-
 3 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 3de40171904..e9c959df6ae 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -16,6 +16,7 @@
 using Avalonia.LogicalTree;
 using Avalonia.Metadata;
 using Avalonia.Styling;
+using Avalonia.VisualTree;
 
 namespace Avalonia.Controls
 {
@@ -479,6 +480,14 @@ protected virtual void ItemsCollectionChanged(object sender, NotifyCollectionCha
 
         internal void PrepareItemContainer(Control container, object? item, int index)
         {
+            // Putting this precondition in place in case we want to raise an event when a
+            // container is realized. If we want to do that, then the event subscriber will expect
+            // the container to be attached to the tree. Not using IsAttachedToVisualTree here
+            // because a bunch of tests don't have a rooted visual tree.
+            if (container.GetVisualParent() is null)
+                throw new InvalidOperationException(
+                    "Container must be attached to parent before PrepareItemContainer is called.");
+
             var itemContainerTheme = ItemContainerTheme;
 
             if (itemContainerTheme is not null && 
diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index b080a9044f0..f71a6c8c1b6 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -70,10 +70,7 @@ void Add(int index, IEnumerable items)
             {
                 var i = index;
                 foreach (var item in items)
-                {
-                    children.Insert(i, CreateContainer(itemsControl, item, i));
-                    ++i;
-                }
+                    InsertContainer(itemsControl, children, item, i++);
 
                 var childCount = children.Count;
                 var delta = i - index;
@@ -124,7 +121,11 @@ void Remove(int index, int count)
             }
         }
 
-        private static Control CreateContainer(ItemsControl itemsControl, object? item, int index)
+        private static void InsertContainer(
+            ItemsControl itemsControl,
+            Controls children,
+            object? item, 
+            int index)
         {
             var generator = itemsControl.ItemContainerGenerator;
             Control container;
@@ -140,8 +141,8 @@ private static Control CreateContainer(ItemsControl itemsControl, object? item,
             }
 
             itemsControl.AddLogicalChild(container);
+            children.Insert(index, container);
             generator.PrepareItemContainer(container, item, index);
-            return container;
         }
 
         private void ClearItemsControlLogicalChildren()
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 6373d5f3bd4..115aff64c8f 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -458,9 +458,9 @@ private Control GetOrCreateElement(IList items, int index)
                 }
                 else if (generator.IsItemItsOwnContainer(controlItem))
                 {
+                    AddInternalChild(controlItem);
                     generator.PrepareItemContainer(controlItem, item, index);
                     controlItem.SetValue(ItemIsOwnContainerProperty, true);
-                    AddInternalChild(controlItem);
                     return controlItem;
                 }
             }

From 7e1068f4414dac497d54a888d6bded43f85e500d Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 11:55:57 +0100
Subject: [PATCH 17/64] Fix test.

---
 tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
index 25d93746d58..1eb13439a51 100644
--- a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
@@ -66,7 +66,7 @@ public void Container_Should_Have_TemplatedParent_Set_To_Null()
         [Fact]
         public void Container_Should_Have_Theme_Set_To_ItemContainerTheme()
         {
-            var theme = new ControlTheme();
+            var theme = new ControlTheme { TargetType = typeof(ContentPresenter) };
             var target = new ItemsControl
             {
                 ItemContainerTheme = theme,

From 004103a925ebbcf4025d40ba2086ef48d25882d2 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 12:26:11 +0100
Subject: [PATCH 18/64] Reimplement DisplayMemberBinding.

Use a slightly different approach to the one that was previously there: create an item template that contains `DisplayMemberBinding`. This is the approach that WPF broadly uses too.
---
 src/Avalonia.Controls/ItemsControl.cs         | 35 +++++++++++++++++--
 .../ItemsControlTests.cs                      | 25 +++++++++++++
 2 files changed, 57 insertions(+), 3 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index e9c959df6ae..a2fb21330c3 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -83,6 +83,7 @@ public IBinding? DisplayMemberBinding
         private int _itemCount;
         private ItemContainerGenerator? _itemContainerGenerator;
         private EventHandler<ChildIndexChangedEventArgs>? _childIndexChanged;
+        private IDataTemplate? _displayMemberItemTemplate;
 
         /// <summary>
         /// Initializes static members of the <see cref="ItemsControl"/> class.
@@ -291,19 +292,19 @@ protected internal virtual void PrepareContainerForItemOverride(Control containe
                 else if (item is not Visual)
                     hcc.Header = item;
 
-                if (ItemTemplate is { } it)
+                if (GetEffectiveItemTemplate() is { } it)
                     hcc.HeaderTemplate = it;
             }
             else if (container is ContentControl cc)
             {
                 cc.Content = item;
-                if (ItemTemplate is { } it)
+                if (GetEffectiveItemTemplate() is { } it)
                     cc.ContentTemplate = it;
             }
             else if (container is ContentPresenter p)
             {
                 p.Content = item;
-                if (ItemTemplate is { } it)
+                if (GetEffectiveItemTemplate() is { } it)
                     p.ContentTemplate = it;
             }
         }
@@ -431,6 +432,17 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
                 throw new NotImplementedException();
                 ////_itemContainerGenerator.ItemContainerTheme = change.GetNewValue<ControlTheme?>();
             }
+            else if (change.Property == ItemTemplateProperty)
+            {
+                if (change.NewValue is not null && DisplayMemberBinding is not null)
+                    throw new InvalidOperationException("Cannot set both DisplayMemberBinding and ItemTemplate.");
+            }
+            else if (change.Property == DisplayMemberBindingProperty)
+            {
+                if (change.NewValue is not null && ItemTemplate is not null)
+                    throw new InvalidOperationException("Cannot set both DisplayMemberBinding and ItemTemplate.");
+                _displayMemberItemTemplate = null;
+            }
         }
 
         /// <summary>
@@ -568,6 +580,23 @@ private void SubscribeToItems(IEnumerable? items)
             }
         }
 
+        private IDataTemplate? GetEffectiveItemTemplate()
+        {
+            if (ItemTemplate is { } itemTemplate)
+                return itemTemplate;
+
+            if (_displayMemberItemTemplate is null && DisplayMemberBinding is { } binding)
+            {
+                _displayMemberItemTemplate = new FuncDataTemplate<object?>((_, _) =>
+                    new TextBlock
+                    {
+                        [!TextBlock.TextProperty] = binding,
+                    });
+            }
+
+            return _displayMemberItemTemplate;
+        }
+
         /// <summary>
         /// Called when the <see cref="ItemTemplate"/> changes.
         /// </summary>
diff --git a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
index 1eb13439a51..eeaef3c3217 100644
--- a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
@@ -708,6 +708,31 @@ public void Should_Use_DisplayMemberBinding()
             Assert.Equal(container.Child!.GetValue(TextBlock.TextProperty), "3");
         }
 
+        [Fact]
+        public void Cannot_Set_Both_DisplayMemberBinding_And_ItemTemplate_1()
+        {
+            var target = new ItemsControl
+            {
+                Template = GetTemplate(),
+                DisplayMemberBinding = new Binding("Length")
+            };
+
+            Assert.Throws<InvalidOperationException>(() => 
+                target.ItemTemplate = new FuncDataTemplate<string>((_, _) => new TextBlock()));
+        }
+
+        [Fact]
+        public void Cannot_Set_Both_DisplayMemberBinding_And_ItemTemplate_2()
+        {
+            var target = new ItemsControl
+            {
+                Template = GetTemplate(),
+                ItemTemplate = new FuncDataTemplate<string>((_, _) => new TextBlock()),
+            };
+
+            Assert.Throws<InvalidOperationException>(() => target.DisplayMemberBinding = new Binding("Length"));
+        }
+
         private class Item
         {
             public Item(string value)

From a6423b258d2948d6b4074da91ebf4d883b786045 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 12:37:53 +0100
Subject: [PATCH 19/64] Fix failing test.

---
 tests/Avalonia.LeakTests/ControlTests.cs | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/tests/Avalonia.LeakTests/ControlTests.cs b/tests/Avalonia.LeakTests/ControlTests.cs
index 4433e25c5a6..59cc0235098 100644
--- a/tests/Avalonia.LeakTests/ControlTests.cs
+++ b/tests/Avalonia.LeakTests/ControlTests.cs
@@ -713,6 +713,10 @@ public void ElementName_Binding_In_DataTemplate_Is_Freed()
         {
             using (Start())
             {
+                // Height of ListBoxItem content + padding.
+                const double ListBoxItemHeight = 12;
+                const double TextBoxHeight = 25;
+
                 var items = new ObservableCollection<int>(Enumerable.Range(0, 10));
                 NameScope ns;
                 TextBox tb;
@@ -721,8 +725,8 @@ public void ElementName_Binding_In_DataTemplate_Is_Freed()
                 {
                     [NameScope.NameScopeProperty] = ns = new NameScope(),
                     Width = 100,
-                    Height = 100,
-                    Content = new StackPanel
+                    Height = (items.Count * ListBoxItemHeight) + TextBoxHeight,
+                    Content = new DockPanel
                     {
                         Children =
                         {
@@ -730,6 +734,8 @@ public void ElementName_Binding_In_DataTemplate_Is_Freed()
                             {
                                 Name = "tb",
                                 Text = "foo",
+                                Height = TextBoxHeight,
+                                [DockPanel.DockProperty] = Dock.Top,
                             }),
                             (lb = new ListBox
                             {
@@ -745,7 +751,8 @@ public void ElementName_Binding_In_DataTemplate_Is_Freed()
                                             Path = "Text",
                                             NameScope = new WeakReference<INameScope>(ns),
                                         }
-                                    })
+                                    }),
+                                Padding = new Thickness(0),
                             }),
                         }
                     }

From 2ae5c9c0fe1cceab04d4296334d16ae48fa8559d Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 15:55:03 +0100
Subject: [PATCH 20/64] Reimplement IChildIndexProvider.

---
 src/Avalonia.Controls/ItemsControl.cs         | 39 ++++++-------------
 .../VirtualizingStackPanel.cs                 |  2 +-
 .../Xaml/StyleTests.cs                        |  5 ++-
 3 files changed, 16 insertions(+), 30 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index a2fb21330c3..b6d74da06e6 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -84,6 +84,7 @@ public IBinding? DisplayMemberBinding
         private ItemContainerGenerator? _itemContainerGenerator;
         private EventHandler<ChildIndexChangedEventArgs>? _childIndexChanged;
         private IDataTemplate? _displayMemberItemTemplate;
+        private Tuple<int, Control>? _containerBeingPrepared;
 
         /// <summary>
         /// Initializes static members of the <see cref="ItemsControl"/> class.
@@ -221,19 +222,8 @@ event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexCh
         /// <inheritdoc/>
         void IItemsPresenterHost.RegisterItemsPresenter(ItemsPresenter presenter)
         {
-            if (Presenter is IChildIndexProvider oldInnerProvider)
-            {
-                oldInnerProvider.ChildIndexChanged -= PresenterChildIndexChanged;
-            }
-
             Presenter = presenter;
-            ////ItemContainerGenerator?.Clear();
-
-            if (Presenter is IChildIndexProvider innerProvider)
-            {
-                innerProvider.ChildIndexChanged += PresenterChildIndexChanged;
-                _childIndexChanged?.Invoke(this, ChildIndexChangedEventArgs.Empty);
-            }
+            _childIndexChanged?.Invoke(this, ChildIndexChangedEventArgs.Empty);
         }
 
         void ICollectionChangedListener.PreChanged(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
@@ -513,11 +503,16 @@ internal void PrepareItemContainer(Control container, object? item, int index)
                 container.DataContext = item;
 
             PrepareContainerForItemOverride(container, item, index);
+
+            _containerBeingPrepared = new(index, container);
+            _childIndexChanged?.Invoke(this, new ChildIndexChangedEventArgs(container));
+            _containerBeingPrepared = null;
         }
 
         internal void ItemContainerIndexChanged(Control container, int oldIndex, int newIndex)
         {
             ContainerIndexChangedOverride(container, oldIndex, newIndex);
+            _childIndexChanged?.Invoke(this, new ChildIndexChangedEventArgs(container));
         }
 
         /// <summary>
@@ -681,27 +676,17 @@ private void UpdatePseudoClasses(int itemCount)
             }
         }
 
-        private void PresenterChildIndexChanged(object? sender, ChildIndexChangedEventArgs e)
-        {
-            _childIndexChanged?.Invoke(this, e);
-        }
-
         int IChildIndexProvider.GetChildIndex(ILogical child)
         {
-            return Presenter is IChildIndexProvider innerProvider
-                ? innerProvider.GetChildIndex(child) : -1;
+            if (_containerBeingPrepared?.Item2 == child)
+                return _containerBeingPrepared.Item1;
+
+            return child is Control container ? IndexFromContainer(container) : -1;
         }
 
         bool IChildIndexProvider.TryGetTotalCount(out int count)
         {
-            if (Presenter is IChildIndexProvider presenter
-                && presenter.TryGetTotalCount(out count))
-            {
-                return true;
-            }
-
-            count = ItemCount;
-            return true;
+            return Items.TryGetCountFast(out count);
         }
     }
 }
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 115aff64c8f..f211ec2edbc 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -830,7 +830,7 @@ public void ItemsRemoved(
                     for (var i = start; i < end; ++i)
                     {
                         if (_elements[i] is Control element)
-                            updateElementIndex(element, newIndex - count, newIndex);
+                            updateElementIndex(element, newIndex + count, newIndex);
                         ++newIndex;
                     }
                 }
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
index 6361dcdbead..70cf3c82766 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
@@ -349,7 +349,6 @@ public void Style_Can_Use_NthLastChild_Selector_After_Reoder()
             }
         }
 
-
         [Fact]
         public void Style_Can_Use_NthChild_Selector_With_ListBox()
         {
@@ -376,16 +375,18 @@ public void Style_Can_Use_NthChild_Selector_With_ListBox()
 
                 window.Show();
 
-                IEnumerable<IBrush> GetColors() => list.Presenter.Panel.Children.Cast<ListBoxItem>().Select(t => t.Background);
+                IEnumerable<IBrush> GetColors() => list.GetRealizedContainers().Cast<ListBoxItem>().Select(t => t.Background);
 
                 Assert.Equal(new[] { Brushes.Transparent, Brushes.Green, Brushes.Transparent }, GetColors());
 
                 collection.Remove(Brushes.Green);
+                window.LayoutManager.ExecuteLayoutPass();
 
                 Assert.Equal(new[] { Brushes.Transparent, Brushes.Blue }, GetColors());
 
                 collection.Add(Brushes.Violet);
                 collection.Add(Brushes.Black);
+                window.LayoutManager.ExecuteLayoutPass();
 
                 Assert.Equal(new[] { Brushes.Transparent, Brushes.Blue, Brushes.Transparent, Brushes.Black }, GetColors());
             }

From 000f393be74a6e9e498a5f86c9f5004e9639879c Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 22:10:48 +0100
Subject: [PATCH 21/64] Refresh containers when relevant property changes.

When `ItemsControl.DisplayMemberBinding` or `ItemTemplate` changes, refresh the containers.
---
 src/Avalonia.Controls/ItemsControl.cs         | 10 ++++
 .../Presenters/ItemsPresenter.cs              |  8 +++
 .../Presenters/PanelContainerGenerator.cs     |  2 +
 src/Avalonia.Controls/VirtualizingPanel.cs    |  4 +-
 .../ItemsControlTests.cs                      | 58 +++++++++++++++++++
 5 files changed, 81 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index b6d74da06e6..31f8f318752 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -426,12 +426,14 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
             {
                 if (change.NewValue is not null && DisplayMemberBinding is not null)
                     throw new InvalidOperationException("Cannot set both DisplayMemberBinding and ItemTemplate.");
+                RefreshContainers();
             }
             else if (change.Property == DisplayMemberBindingProperty)
             {
                 if (change.NewValue is not null && ItemTemplate is not null)
                     throw new InvalidOperationException("Cannot set both DisplayMemberBinding and ItemTemplate.");
                 _displayMemberItemTemplate = null;
+                RefreshContainers();
             }
         }
 
@@ -455,6 +457,14 @@ protected virtual void ItemsChanged(AvaloniaPropertyChangedEventArgs e)
             SubscribeToItems(newValue);
         }
 
+        /// <summary>
+        /// Refreshes the containers displayed by the control.
+        /// </summary>
+        /// <remarks>
+        /// Causes all containers to be unrealized and re-realized.
+        /// </remarks>
+        protected void RefreshContainers() => Presenter?.Refresh();
+
         /// <summary>
         /// Called when the <see cref="INotifyCollectionChanged.CollectionChanged"/> event is
         /// raised on <see cref="Items"/>.
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
index 6f27349cc14..f11d803fc55 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
@@ -84,6 +84,14 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
             }
         }
 
+        internal void Refresh()
+        {
+            if (Panel is VirtualizingPanel v)
+                v.Refresh();
+            else
+                _generator?.Refresh();
+        }
+
         private void ResetState()
         {
             _generator?.Dispose();
diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index f71a6c8c1b6..8d1e7f0b96a 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -45,6 +45,8 @@ public void Dispose()
             _presenter.Panel?.Children.Clear();
         }
 
+        internal void Refresh() => OnItemsChanged(null, CollectionUtils.ResetEventArgs);
+
         private void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
         {
             if (e.Property == ItemsControl.ItemsProperty)
diff --git a/src/Avalonia.Controls/VirtualizingPanel.cs b/src/Avalonia.Controls/VirtualizingPanel.cs
index 0b7a183728d..0d0abe148da 100644
--- a/src/Avalonia.Controls/VirtualizingPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingPanel.cs
@@ -176,6 +176,8 @@ internal void Detach()
             Children.Clear();
         }
 
+        internal void Refresh() => OnItemsControlItemsChanged(null, CollectionUtils.ResetEventArgs);
+
         private ItemsControl EnsureItemsControl()
         {
             if (ItemsControl is null)
@@ -189,7 +191,7 @@ private protected virtual void OnItemsControlPropertyChanged(object? sender, Ava
             {
                 if (e.OldValue is INotifyCollectionChanged inccOld)
                     inccOld.CollectionChanged -= OnItemsControlItemsChanged;
-                OnItemsControlItemsChanged(null, CollectionUtils.ResetEventArgs);
+                Refresh();
                 if (e.NewValue is INotifyCollectionChanged inccNew)
                     inccNew.CollectionChanged += OnItemsControlItemsChanged;
             }
diff --git a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
index eeaef3c3217..28e88d1e715 100644
--- a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
@@ -35,6 +35,31 @@ public void Should_Use_ItemTemplate_To_Create_Control()
             Assert.IsType<Canvas>(container.Child);
         }
 
+        [Fact]
+        public void ItemTemplate_Can_Be_Changed()
+        {
+            var target = new ItemsControl
+            {
+                Template = GetTemplate(),
+                ItemTemplate = new FuncDataTemplate<string>((_, __) => new Canvas()),
+            };
+
+            target.Items = new[] { "Foo" };
+            target.ApplyTemplate();
+            target.Presenter.ApplyTemplate();
+
+            var container = (ContentPresenter)target.Presenter.Panel.Children[0];
+            container.UpdateChild();
+
+            Assert.IsType<Canvas>(container.Child);
+
+            target.ItemTemplate = new FuncDataTemplate<string>((_, __) => new Border());
+            container = (ContentPresenter)target.Presenter.Panel.Children[0];
+            container.UpdateChild();
+
+            Assert.IsType<Border>(container.Child);
+        }
+
         [Fact]
         public void Panel_Should_Have_TemplatedParent_Set_To_ItemsControl()
         {
@@ -708,6 +733,32 @@ public void Should_Use_DisplayMemberBinding()
             Assert.Equal(container.Child!.GetValue(TextBlock.TextProperty), "3");
         }
 
+        [Fact]
+        public void DisplayMemberBinding_Can_Be_Changed()
+        {
+            var target = new ItemsControl
+            {
+                Template = GetTemplate(),
+                DisplayMemberBinding = new Binding("Value")
+            };
+
+            target.Items = new[] { new Item("Foo", "Bar") };
+            target.ApplyTemplate();
+            target.Presenter.ApplyTemplate();
+
+            var container = (ContentPresenter)target.Presenter.Panel.Children[0];
+            container.UpdateChild();
+
+            Assert.Equal(container.Child!.GetValue(TextBlock.TextProperty), "Bar");
+
+            target.DisplayMemberBinding = new Binding("Caption");
+            
+            container = (ContentPresenter)target.Presenter.Panel.Children[0];
+            container.UpdateChild();
+
+            Assert.Equal(container.Child!.GetValue(TextBlock.TextProperty), "Foo");
+        }
+
         [Fact]
         public void Cannot_Set_Both_DisplayMemberBinding_And_ItemTemplate_1()
         {
@@ -740,6 +791,13 @@ public Item(string value)
                 Value = value;
             }
 
+            public Item(string caption, string value)
+            {
+                Caption = caption;
+                Value = value;
+            }
+
+            public string Caption { get; }
             public string Value { get; }
         }
 

From 1950e4b0a3f4c200bc944fd6c07fcbc11351b524 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 22:12:12 +0100
Subject: [PATCH 22/64] Remove TabControl.HeaderDisplayMemberBinding.

As `DisplayMemberBinding` should select the member for the header (in WPF it's `DisplayMemberPath`). Also set `TabItem.TabStripPlacement`.
---
 .../ControlCatalog/Pages/TabControlPage.xaml  |  2 +-
 src/Avalonia.Controls/TabControl.cs           | 32 ++++++++-----------
 2 files changed, 15 insertions(+), 19 deletions(-)

diff --git a/samples/ControlCatalog/Pages/TabControlPage.xaml b/samples/ControlCatalog/Pages/TabControlPage.xaml
index e289de90f98..a775056ebe9 100644
--- a/samples/ControlCatalog/Pages/TabControlPage.xaml
+++ b/samples/ControlCatalog/Pages/TabControlPage.xaml
@@ -53,7 +53,7 @@
                 <TabControl
                     Items="{Binding Tabs}"
                     Margin="0 16"
-                    HeaderDisplayMemberBinding="{Binding Header, x:DataType=viewModels:TabControlPageViewModelItem}"
+                    DisplayMemberBinding="{Binding Header, x:DataType=viewModels:TabControlPageViewModelItem}"
                     TabStripPlacement="{Binding TabPlacement}">
                     <TabControl.ContentTemplate>
                         <DataTemplate x:DataType="viewModels:TabControlPageViewModelItem">
diff --git a/src/Avalonia.Controls/TabControl.cs b/src/Avalonia.Controls/TabControl.cs
index 952a9e448ce..a6085e53cd6 100644
--- a/src/Avalonia.Controls/TabControl.cs
+++ b/src/Avalonia.Controls/TabControl.cs
@@ -57,12 +57,6 @@ public class TabControl : SelectingItemsControl, IContentPresenterHost
         /// </summary>
         public static readonly StyledProperty<IDataTemplate?> SelectedContentTemplateProperty =
             AvaloniaProperty.Register<TabControl, IDataTemplate?>(nameof(SelectedContentTemplate));
-
-        /// <summary>
-        /// Defines the <see cref="HeaderDisplayMemberBinding" /> property
-        /// </summary>
-        public static readonly StyledProperty<IBinding?> HeaderDisplayMemberBindingProperty =
-            AvaloniaProperty.Register<HeaderedItemsControl, IBinding?>(nameof(HeaderDisplayMemberBinding));
         
         /// <summary>
         /// The default value for the <see cref="ItemsControl.ItemsPanel"/> property.
@@ -141,16 +135,6 @@ public IDataTemplate? SelectedContentTemplate
             get { return GetValue(SelectedContentTemplateProperty); }
             internal set { SetValue(SelectedContentTemplateProperty, value); }
         }
-        
-        /// <summary>
-        /// Gets or sets the <see cref="IBinding"/> to use for binding to the display member of each tab-items header.
-        /// </summary>
-        [AssignBinding]
-        public IBinding? HeaderDisplayMemberBinding
-        {
-            get { return GetValue(HeaderDisplayMemberBindingProperty); }
-            set { SetValue(HeaderDisplayMemberBindingProperty, value); }
-        }
 
         internal ItemsPresenter? ItemsPresenterPart { get; private set; }
 
@@ -172,8 +156,12 @@ protected internal override void PrepareContainerForItemOverride(Control element
         {
             base.PrepareContainerForItemOverride(element, item, index);
             
-            if (element is HeaderedContentControl hcc && ContentTemplate is { } ct)
-                hcc.ContentTemplate = ct;
+            if (element is TabItem tabItem)
+            {
+                if (ContentTemplate is { } ct)
+                    tabItem.ContentTemplate = ct;
+                tabItem.SetValue(TabStripPlacementProperty, TabStripPlacement);
+            }
 
             if (index == SelectedIndex && element is ContentControl container)
             {
@@ -268,5 +256,13 @@ protected override void OnPointerReleased(PointerReleasedEventArgs e)
                 }
             }
         }
+
+        protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
+        {
+            base.OnPropertyChanged(change);
+
+            if (change.Property == TabStripPlacementProperty)
+                RefreshContainers();
+        }
     }
 }

From 306c0454935d400465c397debf024f4c5b82ed5c Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 22:38:19 +0100
Subject: [PATCH 23/64] Reinstate some commented-out code.

---
 src/Avalonia.Controls/ComboBox.cs     | 17 ++++++++---------
 src/Avalonia.Controls/ItemsControl.cs |  3 +--
 src/Avalonia.Controls/MenuBase.cs     | 11 +----------
 3 files changed, 10 insertions(+), 21 deletions(-)

diff --git a/src/Avalonia.Controls/ComboBox.cs b/src/Avalonia.Controls/ComboBox.cs
index e6af255c298..a573a9d8872 100644
--- a/src/Avalonia.Controls/ComboBox.cs
+++ b/src/Avalonia.Controls/ComboBox.cs
@@ -440,15 +440,14 @@ private void UpdateFlowDirection()
 
         private void SelectFocusedItem()
         {
-            throw new NotImplementedException();
-            ////foreach (ItemContainerInfo dropdownItem in ItemContainerGenerator.Containers)
-            ////{
-            ////    if (dropdownItem.ContainerControl.IsFocused)
-            ////    {
-            ////        SelectedIndex = dropdownItem.Index;
-            ////        break;
-            ////    }
-            ////}
+            foreach (var dropdownItem in GetRealizedContainers())
+            {
+                if (dropdownItem.IsFocused)
+                {
+                    SelectedIndex = IndexFromContainer(dropdownItem);
+                    break;
+                }
+            }
         }
 
         private void SelectNext()
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 31f8f318752..e07eea57ef9 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -419,8 +419,7 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
             }
             else if (change.Property == ItemContainerThemeProperty && _itemContainerGenerator is not null)
             {
-                throw new NotImplementedException();
-                ////_itemContainerGenerator.ItemContainerTheme = change.GetNewValue<ControlTheme?>();
+                RefreshContainers();
             }
             else if (change.Property == ItemTemplateProperty)
             {
diff --git a/src/Avalonia.Controls/MenuBase.cs b/src/Avalonia.Controls/MenuBase.cs
index 3b211d4cc73..3bbd5b7de49 100644
--- a/src/Avalonia.Controls/MenuBase.cs
+++ b/src/Avalonia.Controls/MenuBase.cs
@@ -95,16 +95,7 @@ public bool IsOpen
         }
 
         /// <inheritdoc/>
-        IEnumerable<IMenuItem> IMenuElement.SubItems
-        {
-            get
-            {
-                throw new NotImplementedException();
-                ////return ItemContainerGenerator.Containers
-                ////    .Select(x => x.ContainerControl)
-                ////    .OfType<IMenuItem>();
-            }
-        }
+        IEnumerable<IMenuItem> IMenuElement.SubItems => GetRealizedContainers().OfType<IMenuItem>();
 
         /// <summary>
         /// Gets the interaction handler for the menu.

From a7a71034b03e6720e80926b4c3a11a1b997eef5a Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 22:38:49 +0100
Subject: [PATCH 24/64] Remove unneeded tests.

---
 .../ItemsPresenterTests_Virtualization.cs     |  374 ------
 ...emsPresenterTests_Virtualization_Simple.cs | 1110 -----------------
 2 files changed, 1484 deletions(-)
 delete mode 100644 tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization.cs
 delete mode 100644 tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs

diff --git a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization.cs b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization.cs
deleted file mode 100644
index d0798d469f5..00000000000
--- a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization.cs
+++ /dev/null
@@ -1,374 +0,0 @@
-////using System;
-////using System.Collections.Generic;
-////using System.Linq;
-////using Avalonia.Controls.Generators;
-////using Avalonia.Controls.Presenters;
-////using Avalonia.Controls.Primitives;
-////using Avalonia.Controls.Templates;
-////using Avalonia.Layout;
-////using Avalonia.Platform;
-////using Avalonia.Rendering;
-////using Avalonia.UnitTests;
-////using Avalonia.VisualTree;
-////using Xunit;
-
-////namespace Avalonia.Controls.UnitTests.Presenters
-////{
-////    public class ItemsPresenterTests_Virtualization
-////    {
-////        [Fact]
-////        public void Should_Not_Create_Items_Before_Added_To_Visual_Tree()
-////        {
-////            var items = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-////            var target = new TestItemsPresenter(true)
-////            {
-////                Items = items,
-////                ItemsPanel = VirtualizingPanelTemplate(Orientation.Vertical),
-////                ItemTemplate = ItemTemplate(),
-////                VirtualizationMode = ItemVirtualizationMode.Simple,
-////            };
-
-////            var scroller = new ScrollContentPresenter
-////            {
-////                Content = target,
-////            };
-
-////            scroller.UpdateChild();
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Empty(target.Panel.Children);
-
-////            var root = new TestRoot
-////            {
-////                Child = scroller,
-////            };
-
-////            target.InvalidateMeasure();
-////            target.Panel.InvalidateMeasure();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(10, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Should_Return_IsLogicalScrollEnabled_False_When_Has_No_Virtualizing_Panel()
-////        {
-////            var target = CreateTarget();
-////            target.ClearValue(ItemsPresenter.ItemsPanelProperty);
-
-////            target.ApplyTemplate();
-
-////            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
-////        }
-
-////        [Fact]
-////        public void Should_Return_IsLogicalScrollEnabled_False_When_VirtualizationMode_None()
-////        {
-////            var target = CreateTarget(ItemVirtualizationMode.None);
-
-////            target.ApplyTemplate();
-
-////            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
-////        }
-
-////        [Fact]
-////        public void Should_Return_IsLogicalScrollEnabled_False_When_Doesnt_Have_ScrollPresenter_Parent()
-////        {
-////            var target = new ItemsPresenter
-////            {
-////                ItemsPanel = VirtualizingPanelTemplate(),
-////                ItemTemplate = ItemTemplate(),
-////                VirtualizationMode = ItemVirtualizationMode.Simple,
-////            };
-
-////            target.ApplyTemplate();
-
-////            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
-////        }
-
-////        [Fact]
-////        public void Should_Return_IsLogicalScrollEnabled_True()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-
-////            Assert.True(((ILogicalScrollable)target).IsLogicalScrollEnabled);
-////        }
-
-////        [Fact]
-////        public void Parent_ScrollContentPresenter_Properties_Should_Be_Set()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var scroll = (ScrollContentPresenter)target.Parent;
-////            Assert.Equal(new Size(10, 20), scroll.Extent);
-////            Assert.Equal(new Size(100, 10), scroll.Viewport);
-////        }
-
-////        [Fact]
-////        public void Should_Fill_Panel_With_Containers()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-
-////            target.Measure(new Size(100, 100));
-////            Assert.Equal(10, target.Panel.Children.Count);
-
-////            target.Arrange(new Rect(0, 0, 100, 100));
-////            Assert.Equal(10, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Should_Only_Create_Enough_Containers_To_Display_All_Items()
-////        {
-////            var target = CreateTarget(itemCount: 2);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(2, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Should_Expand_To_Fit_Containers_When_Flexible_Size()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(Size.Infinity);
-////            target.Arrange(new Rect(target.DesiredSize));
-
-////            Assert.Equal(new Size(10, 200), target.DesiredSize);
-////            Assert.Equal(new Size(10, 200), target.Bounds.Size);
-////            Assert.Equal(20, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Initial_Item_DataContexts_Should_Be_Correct()
-////        {
-////            var target = CreateTarget();
-////            var items = (IList<string>)target.Items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            for (var i = 0; i < target.Panel.Children.Count; ++i)
-////            {
-////                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
-////            }
-////        }
-
-////        [Fact]
-////        public void Should_Add_New_Items_When_Control_Is_Enlarged()
-////        {
-////            var target = CreateTarget();
-////            var items = (IList<string>)target.Items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(10, target.Panel.Children.Count);
-
-////            target.Measure(new Size(120, 120));
-////            target.Arrange(new Rect(0, 0, 100, 120));
-
-////            Assert.Equal(12, target.Panel.Children.Count);
-
-////            for (var i = 0; i < target.Panel.Children.Count; ++i)
-////            {
-////                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
-////            }
-////        }
-
-////        [Fact]
-////        public void Should_Not_Create_Virtualizer_Before_Panel()
-////        {
-////            var target = CreateTarget();
-
-////            Assert.Null(target.Panel);
-////            Assert.Null(target.Virtualizer);
-////        }
-
-////        [Fact]
-////        public void Changing_VirtualizationMode_None_To_Simple_Should_Update_Control()
-////        {
-////            var target = CreateTarget(mode: ItemVirtualizationMode.None);
-////            var scroll = (ScrollContentPresenter)target.Parent;
-
-////            scroll.Measure(new Size(100, 100));
-////            scroll.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(20, target.Panel.Children.Count);
-////            Assert.Equal(new Size(100, 200), scroll.Extent);
-////            Assert.Equal(new Size(100, 100), scroll.Viewport);
-
-////            target.VirtualizationMode = ItemVirtualizationMode.Simple;
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(10, target.Panel.Children.Count);
-////            Assert.Equal(new Size(10, 20), scroll.Extent);
-////            Assert.Equal(new Size(100, 10), scroll.Viewport);
-////        }
-
-////        [Fact]
-////        public void Changing_VirtualizationMode_None_To_Simple_Should_Add_Correct_Number_Of_Controls()
-////        {
-////            using (UnitTestApplication.Start(new TestServices()))
-////            {
-////                var target = CreateTarget(mode: ItemVirtualizationMode.None);
-////                var scroll = (TestScroller)target.Parent;
-
-////                scroll.Width = scroll.Height = 100;
-////                scroll.LayoutManager.ExecuteInitialLayoutPass();
-
-////                // Ensure than an intermediate measure pass doesn't add more controls than it
-////                // should. This can happen if target gets measured with Size.Infinity which
-////                // is what the available size should be when VirtualizationMode == None but not
-////                // what it should after VirtualizationMode is changed to Simple.
-////                target.Panel.Children.CollectionChanged += (s, e) =>
-////                {
-////                    Assert.InRange(target.Panel.Children.Count, 0, 10);
-////                };
-
-////                target.VirtualizationMode = ItemVirtualizationMode.Simple;
-////                ((ILayoutRoot)scroll.GetVisualRoot()).LayoutManager.ExecuteLayoutPass();
-
-////                Assert.Equal(10, target.Panel.Children.Count);
-////            }
-////        }
-
-////        [Fact]
-////        public void Changing_VirtualizationMode_Simple_To_None_Should_Update_Control()
-////        {
-////            var target = CreateTarget();
-////            var scroll = (ScrollContentPresenter)target.Parent;
-
-////            scroll.Measure(new Size(100, 100));
-////            scroll.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(10, target.Panel.Children.Count);
-////            Assert.Equal(new Size(10, 20), scroll.Extent);
-////            Assert.Equal(new Size(100, 10), scroll.Viewport);
-
-////            target.VirtualizationMode = ItemVirtualizationMode.None;
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            // Here - unlike changing the other way - we need to do a layout pass on the scroll
-////            // content presenter as non-logical scroll values are only updated on arrange.
-////            scroll.Measure(new Size(100, 100));
-////            scroll.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(20, target.Panel.Children.Count);
-////            Assert.Equal(new Size(100, 200), scroll.Extent);
-////            Assert.Equal(new Size(100, 100), scroll.Viewport);
-////        }
-
-////        private static ItemsPresenter CreateTarget(
-////            ItemVirtualizationMode mode = ItemVirtualizationMode.Simple,
-////            Orientation orientation = Orientation.Vertical,
-////            bool useContainers = true,
-////            int itemCount = 20)
-////        {
-////            ItemsPresenter result;
-////            var items = Enumerable.Range(0, itemCount).Select(x => $"Item {x}").ToList();
-
-////            var scroller = new TestScroller
-////            {
-////                CanHorizontallyScroll = false,
-////                CanVerticallyScroll = true,
-////                Content = result = new TestItemsPresenter(useContainers)
-////                {
-////                    Items = items,
-////                    ItemsPanel = VirtualizingPanelTemplate(orientation),
-////                    ItemTemplate = ItemTemplate(),
-////                    VirtualizationMode = mode,
-////                }
-////            };
-
-////            scroller.UpdateChild();
-
-////            return result;
-////        }
-
-////        private static IDataTemplate ItemTemplate()
-////        {
-////            return new FuncDataTemplate<string>((x, _) => new Canvas
-////            {
-////                Width = 10,
-////                Height = 10,
-////            });
-////        }
-
-////        private static ITemplate<Panel> VirtualizingPanelTemplate(
-////            Orientation orientation = Orientation.Vertical)
-////        {
-////            return new FuncTemplate<Panel>(() => new VirtualizingStackPanel
-////            {
-////                Orientation = orientation,
-////            });
-////        }
-
-////        private class TestScroller : ScrollContentPresenter, IRenderRoot, ILayoutRoot
-////        {
-////            public TestScroller()
-////            {
-////                LayoutManager = new LayoutManager(this);
-////            }
-
-////            public IRenderer Renderer { get; }
-////            public Size ClientSize { get; }
-////            public double RenderScaling => 1;
-
-////            public Size MaxClientSize => Size.Infinity;
-
-////            public double LayoutScaling => 1;
-
-////            public ILayoutManager LayoutManager { get; }
-
-////            public IRenderTarget CreateRenderTarget() => throw new NotImplementedException();
-////            public void Invalidate(Rect rect) => throw new NotImplementedException();
-////            public Point PointToClient(PixelPoint p) => throw new NotImplementedException();
-////            public PixelPoint PointToScreen(Point p) => throw new NotImplementedException();
-////        }
-
-////        private class TestItemsPresenter : ItemsPresenter
-////        {
-////            private bool _useContainers;
-
-////            public TestItemsPresenter(bool useContainers)
-////            {
-////                _useContainers = useContainers;
-////            }
-
-////            protected override IItemContainerGenerator CreateItemContainerGenerator()
-////            {
-////                return _useContainers ?
-////                    new ItemContainerGenerator<TestContainer>(this, TestContainer.ContentProperty, null) :
-////                    new ItemContainerGenerator(this);
-////            }
-////        }
-
-////        private class TestContainer : ContentControl
-////        {
-////            public TestContainer()
-////            {
-////                Width = 10;
-////                Height = 10;
-////            }
-////        }
-////    }
-////}
diff --git a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs
deleted file mode 100644
index 131b86e4b16..00000000000
--- a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs
+++ /dev/null
@@ -1,1110 +0,0 @@
-////using System;
-////using System.Collections;
-////using System.Collections.Generic;
-////using System.Collections.ObjectModel;
-////using System.Linq;
-////using Avalonia.Collections;
-////using Avalonia.Controls.Generators;
-////using Avalonia.Controls.Presenters;
-////using Avalonia.Controls.Primitives;
-////using Avalonia.Controls.Templates;
-////using Avalonia.Input;
-////using Avalonia.Layout;
-////using Avalonia.LogicalTree;
-////using Avalonia.Platform;
-////using Avalonia.Rendering;
-////using Avalonia.Styling;
-////using Avalonia.UnitTests;
-////using Xunit;
-
-////namespace Avalonia.Controls.UnitTests.Presenters
-////{
-////    public class ItemsPresenterTests_Virtualization_Simple
-////    {
-////        [Fact]
-////        public void Should_Return_Items_Count_For_Extent_Vertical()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-
-////            Assert.Equal(new Size(0, 20), ((ILogicalScrollable)target).Extent);
-////        }
-
-////        [Fact]
-////        public void Should_Return_Items_Count_For_Extent_Horizontal()
-////        {
-////            var target = CreateTarget(orientation: Orientation.Horizontal);
-
-////            target.ApplyTemplate();
-
-////            Assert.Equal(new Size(20, 0), ((ILogicalScrollable)target).Extent);
-////        }
-
-////        [Fact]
-////        public void Should_Have_Number_Of_Visible_Items_As_Viewport_Vertical()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(new Size(100, 10), ((ILogicalScrollable)target).Viewport);
-////        }
-
-////        [Fact]
-////        public void Should_Have_Number_Of_Visible_Items_As_Viewport_Horizontal()
-////        {
-////            var target = CreateTarget(orientation: Orientation.Horizontal);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(new Size(10, 100), ((ILogicalScrollable)target).Viewport);
-////        }
-
-////        [Fact]
-////        public void Should_Add_Containers_When_Panel_Is_Not_Full()
-////        {
-////            var target = CreateTarget(itemCount: 5);
-////            var items = (IList<string>)target.Items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(5, target.Panel.Children.Count);
-
-////            items.Add("New Item");
-
-////            Assert.Equal(6, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Should_Remove_Items_When_Control_Is_Shrank()
-////        {
-////            var target = CreateTarget();
-////            var items = (IList<string>)target.Items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(10, target.Panel.Children.Count);
-
-////            target.Measure(new Size(100, 80));
-////            target.Arrange(new Rect(0, 0, 100, 80));
-
-////            Assert.Equal(8, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Should_Add_New_Containers_At_Top_When_Control_Is_Scrolled_To_Bottom_And_Enlarged()
-////        {
-////            var target = CreateTarget();
-////            var items = (IList<string>)target.Items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(10, target.Panel.Children.Count);
-
-////            ((IScrollable)target).Offset = new Vector(0, 10);
-////            target.Measure(new Size(120, 120));
-////            target.Arrange(new Rect(0, 0, 100, 120));
-
-////            Assert.Equal(12, target.Panel.Children.Count);
-
-////            for (var i = 0; i < target.Panel.Children.Count; ++i)
-////            {
-////                Assert.Equal(items[i + 8], target.Panel.Children[i].DataContext);
-////            }
-////        }
-
-////        [Fact]
-////        public void Should_Update_Containers_When_Items_Changes()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            target.Items = new[] { "foo", "bar", "baz" };
-
-////            Assert.Equal(3, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Should_Decrease_The_Viewport_Size_By_One_If_There_Is_A_Partial_Item()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 95));
-////            target.Arrange(new Rect(0, 0, 100, 95));
-
-////            Assert.Equal(new Size(100, 9), ((ILogicalScrollable)target).Viewport);
-////        }
-
-////        [Fact]
-////        public void Moving_To_And_From_The_End_With_Partial_Item_Should_Set_Panel_PixelOffset()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 95));
-////            target.Arrange(new Rect(0, 0, 100, 95));
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 11);
-
-////            var minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
-////            Assert.Equal(new Vector(0, 11), ((ILogicalScrollable)target).Offset);
-////            Assert.Equal(10, minIndex);
-////            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
-
-////            minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
-////            Assert.Equal(new Vector(0, 10), ((ILogicalScrollable)target).Offset);
-////            Assert.Equal(10, minIndex);
-////            Assert.Equal(0, ((IVirtualizingPanel)target.Panel).PixelOffset);
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 11);
-
-////            minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
-////            Assert.Equal(new Vector(0, 11), ((ILogicalScrollable)target).Offset);
-////            Assert.Equal(10, minIndex);
-////            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
-////        }
-
-////        [Fact]
-////        public void Inserting_Items_Should_Update_Containers()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
-
-////            var expected = Enumerable.Range(5, 10).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            items.Insert(6, "Inserted");
-////            expected.Insert(1, "Inserted");
-////            expected.RemoveAt(expected.Count - 1);
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Inserting_Items_Before_Visibile_Containers_Should_Update_Containers()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
-
-////            var expected = Enumerable.Range(5, 10).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            items.Insert(0, "Inserted");
-
-////            expected = Enumerable.Range(4, 10).Select(x => $"Item {x}").ToList();
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Removing_First_Materialized_Item_Should_Update_Containers()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            items.RemoveAt(0);
-////            expected = Enumerable.Range(1, 10).Select(x => $"Item {x}").ToList();
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Removing_Items_From_Middle_Should_Update_Containers_When_All_Items_Visible()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 200));
-////            target.Arrange(new Rect(0, 0, 100, 200));
-
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(items, actual);
-
-////            items.RemoveAt(2);
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(items, actual);
-
-////            items.RemoveAt(items.Count - 2);
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(items, actual);
-////        }
-
-////        [Fact]
-////        public void Removing_Last_Item_Should_Update_Containers_When_All_Items_Visible()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 200));
-////            target.Arrange(new Rect(0, 0, 100, 200));
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
-
-////            var expected = Enumerable.Range(0, 20).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            items.Remove(items.Last());
-////            expected.Remove(expected.Last());
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Removing_Items_When_Scrolled_To_End_Should_Recyle_Containers_At_Top()
-////        {
-////            var target = CreateTarget(useAvaloniaList: true);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
-
-////            var expected = Enumerable.Range(10, 10).Select(x => $"Item {x}").ToList();
-////            var items = (AvaloniaList<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            items.RemoveRange(18, 2);
-////            expected = Enumerable.Range(8, 10).Select(x => $"Item {x}").ToList();
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Removing_Items_When_Scrolled_To_Near_End_Should_Recycle_Containers_At_Bottom_And_Top()
-////        {
-////            var target = CreateTarget(useAvaloniaList: true);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 9);
-
-////            var expected = Enumerable.Range(9, 10).Select(x => $"Item {x}").ToList();
-////            var items = (AvaloniaList<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            items.RemoveRange(15, 3);
-////            expected = Enumerable.Range(7, 8).Select(x => $"Item {x}")
-////                .Concat(Enumerable.Range(18, 2).Select(x => $"Item {x}"))
-////                .ToList();
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Measuring_To_Infinity_When_Scrolled_To_End_Should_Not_Throw()
-////        {
-////            var target = CreateTarget(useAvaloniaList: true);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
-
-////            // Check for issue #589: this should not throw.
-////            target.Measure(Size.Infinity);
-
-////            var expected = Enumerable.Range(0, 20).Select(x => $"Item {x}").ToList();
-////            var items = (AvaloniaList<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Replacing_Items_Should_Update_Containers()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            items[4] = expected[4] = "Replaced";
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Moving_Items_Should_Update_Containers()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            items.Move(4, 8);
-////            var i = expected[4];
-////            expected.RemoveAt(4);
-////            expected.Insert(8, i);
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Setting_Items_To_Null_Should_Remove_Containers()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            target.Items = null;
-
-////            Assert.Empty(target.Panel.Children);
-////        }
-
-////        [Fact]
-////        public void Reassigning_Items_Should_Create_Containers()
-////        {
-////            var target = CreateTarget(itemCount: 5);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
-////            target.Items = expected;
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Inserting_Then_Removing_Should_Add_Remove_Containers()
-////        {
-////            var items = new AvaloniaList<string>(Enumerable.Range(0, 5).Select(x => $"Item {x}"));
-////            var toAdd = Enumerable.Range(0, 3).Select(x => $"Added Item {x}").ToArray();
-////            var target = new ItemsPresenter
-////            {
-////                VirtualizationMode = ItemVirtualizationMode.None,
-////                Items = items,
-////                ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 10 }),
-////            };
-
-////            target.ApplyTemplate();
-
-////            Assert.Equal(items.Count, target.Panel.Children.Count);
-
-////            int addIndex = 1;
-////            foreach (var item in toAdd)
-////            {
-////                items.Insert(addIndex++, item);
-////            }
-
-////            Assert.Equal(items.Count, target.Panel.Children.Count);
-
-////            foreach (var item in toAdd)
-////            {
-////                items.Remove(item);
-////            }
-
-////            Assert.Equal(items.Count, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Reassigning_Items_Should_Remove_Containers()
-////        {
-////            var target = CreateTarget(itemCount: 6);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
-////            target.Items = expected;
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Clearing_Items_And_ReAdding_Should_Remove_Containers()
-////        {
-////            var target = CreateTarget(itemCount: 6);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
-////            target.Items = null;
-////            target.Items = expected;
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Scrolling_To_Partial_Last_Item_Then_Adding_Item_Updates_Containers()
-////        {
-////            var target = CreateTarget(itemCount: 10);
-////            var items = (IList<string>)target.Items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 95));
-////            target.Arrange(new Rect(0, 0, 100, 95));
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 1);
-////            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-
-////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
-
-////            items.Add("Item 10");
-
-////            expected = Enumerable.Range(1, 10).Select(x => $"Item {x}").ToList();
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////            Assert.Equal(0, ((IVirtualizingPanel)target.Panel).PixelOffset);
-////        }
-
-////        [Fact]
-////        public void Scrolling_To_Item_In_Zero_Sized_Presenter_Doesnt_Throw()
-////        {
-////            using (UnitTestApplication.Start(new TestServices()))
-////            {
-////                var target = CreateTarget(itemCount: 10);
-////                var items = (IList<string>)target.Items;
-////                target.ApplyTemplate();
-////                target.Measure(Size.Empty);
-////                target.Arrange(Rect.Empty);
-
-////                // Check for issue #591: this should not throw.
-////                target.ScrollIntoView(0);
-////            }
-////        }
-
-////        [Fact]
-////        public void InsertRange_Items_Should_Update_Containers()
-////        {
-////            var target = CreateTarget(useAvaloniaList: true);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-////            var items = (AvaloniaList<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            var toAdd = Enumerable.Range(0, 3).Select(x => $"New Item {x}").ToList();
-
-////            int index = 1;
-
-////            items.InsertRange(index, toAdd);
-////            expected.InsertRange(index, toAdd);
-////            expected.RemoveRange(10, toAdd.Count);
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void InsertRange_Items_Before_Last_Should_Update_Containers()
-////        {
-////            var target = CreateTarget(useAvaloniaList: true);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-////            var items = (AvaloniaList<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            var toAdd = Enumerable.Range(0, 3).Select(x => $"New Item {x}").ToList();
-
-////            int index = 8;
-
-////            items.InsertRange(index, toAdd);
-////            expected.InsertRange(index, toAdd);
-////            expected.RemoveRange(10, toAdd.Count);
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void RemoveRange_Items_Should_Update_Containers()
-////        {
-////            var target = CreateTarget(useAvaloniaList: true);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 13).Select(x => $"Item {x}").ToList();
-////            var items = (AvaloniaList<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected.Take(10), actual);
-
-////            int index = 5;
-////            int count = 3;
-
-////            items.RemoveRange(index, count);
-////            expected.RemoveRange(index, count);
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void RemoveRange_Items_Before_Last_Should_Update_Containers()
-////        {
-////            var target = CreateTarget(useAvaloniaList: true);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 13).Select(x => $"Item {x}").ToList();
-////            var items = (AvaloniaList<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected.Take(10), actual);
-
-////            int index = 8;
-////            int count = 3;
-
-////            items.RemoveRange(index, count);
-////            expected.RemoveRange(index, count);
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Should_Add_Containers_For_Items_After_Clear()
-////        {
-////            var target = CreateTarget(itemCount: 10);
-////            var defaultItems = (IList<string>)target.Items;
-////            var items = new AvaloniaList<string>(defaultItems);
-////            target.Items = items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(target.DesiredSize));
-
-////            Assert.Equal(10, target.Panel.Children.Count);
-
-////            items.Clear();
-
-////            target.Panel.Measure(new Size(100, 100));
-////            target.Panel.Arrange(new Rect(target.Panel.DesiredSize));
-
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(target.DesiredSize));
-
-////            Assert.Empty(target.Panel.Children);
-
-////            items.AddRange(defaultItems.Select(s => s + " new"));
-
-////            target.Panel.Measure(new Size(100, 100));
-////            target.Panel.Arrange(new Rect(target.Panel.DesiredSize));
-
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(target.DesiredSize));
-
-////            Assert.Equal(10, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Scroll_To_Last_Should_Work()
-////        {
-////            var target = CreateTarget(itemCount: 11);
-////            var scroller = (TestScroller)target.Parent;
-
-////            scroller.Width = scroller.Height = 100;
-////            scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-////            var last = (target.Items as IList)[10];
-
-////            target.ScrollIntoView(10);
-
-////            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-////            Assert.Same(target.Panel.Children[9].DataContext, last);
-////        }
-
-////        [Fact]
-////        public void Second_Scroll_To_Last_Should_Work()
-////        {
-////            var target = CreateTarget(itemCount: 11);
-////            var scroller = (TestScroller)target.Parent;
-
-////            scroller.Width = scroller.Height = 100;
-////            scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-////            var last = (target.Items as IList)[10];
-
-////            target.ScrollIntoView(10);
-
-////            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-////            Assert.Same(target.Panel.Children[9].DataContext, last);
-
-////            target.ScrollIntoView(10);
-
-////            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-////            Assert.Same(target.Panel.Children[9].DataContext, last);
-////        }
-
-////        [Fact]
-////        public void Scrolling_Less_Than_A_Page_Should_Move_Recycled_Items()
-////        {
-////            var target = CreateTarget();
-////            var items = (IList<string>)target.Items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var containers = target.Panel.Children.ToList();
-////            var scroller = (ScrollContentPresenter)target.Parent;
-
-////            scroller.Offset = new Vector(0, 5);
-
-////            var scrolledContainers = containers
-////                .Skip(5)
-////                .Take(5)
-////                .Concat(containers.Take(5)).ToList();
-
-////            Assert.Equal(new Vector(0, 5), ((ILogicalScrollable)target).Offset);
-////            Assert.Equal(scrolledContainers, target.Panel.Children);
-
-////            for (var i = 0; i < target.Panel.Children.Count; ++i)
-////            {
-////                Assert.Equal(items[i + 5], target.Panel.Children[i].DataContext);
-////            }
-
-////            scroller.Offset = new Vector(0, 0);
-////            Assert.Equal(new Vector(0, 0), ((ILogicalScrollable)target).Offset);
-////            Assert.Equal(containers, target.Panel.Children);
-
-////            var dcs = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            for (var i = 0; i < target.Panel.Children.Count; ++i)
-////            {
-////                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
-////            }
-////        }
-
-////        [Fact]
-////        public void Scrolling_More_Than_A_Page_Should_Recycle_Items()
-////        {
-////            var target = CreateTarget(itemCount: 50);
-////            var items = (IList<string>)target.Items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var containers = target.Panel.Children.ToList();
-////            var scroller = (ScrollContentPresenter)target.Parent;
-
-////            scroller.Offset = new Vector(0, 20);
-
-////            Assert.Equal(new Vector(0, 20), ((ILogicalScrollable)target).Offset);
-////            Assert.Equal(containers, target.Panel.Children);
-
-////            for (var i = 0; i < target.Panel.Children.Count; ++i)
-////            {
-////                Assert.Equal(items[i + 20], target.Panel.Children[i].DataContext);
-////            }
-
-////            scroller.Offset = new Vector(0, 0);
-
-////            Assert.Equal(new Vector(0, 0), ((ILogicalScrollable)target).Offset);
-////            Assert.Equal(containers, target.Panel.Children);
-
-////            for (var i = 0; i < target.Panel.Children.Count; ++i)
-////            {
-////                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
-////            }
-////        }
-
-////        public class Vertical
-////        {
-////            [Fact]
-////            public void GetControlInDirection_Down_Should_Return_Existing_Container_If_Materialized()
-////            {
-////                var target = CreateTarget();
-////                var scroller = (TestScroller)target.Parent;
-
-////                scroller.Width = scroller.Height = 100;
-////                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-////                var from = target.Panel.Children[5];
-////                var result = ((ILogicalScrollable)target).GetControlInDirection(
-////                    NavigationDirection.Down,
-////                    from);
-
-////                Assert.Same(target.Panel.Children[6], result);
-////            }
-
-////            [Fact]
-////            public void GetControlInDirection_Down_Should_Scroll_If_Necessary()
-////            {
-////                var target = CreateTarget();
-////                var scroller = (TestScroller)target.Parent;
-
-////                scroller.Width = scroller.Height = 100;
-////                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-////                var from = target.Panel.Children[9];
-////                var result = ((ILogicalScrollable)target).GetControlInDirection(
-////                    NavigationDirection.Down,
-////                    from);
-
-////                Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-////                Assert.Same(target.Panel.Children[9], result);
-////            }
-
-////            [Fact]
-////            public void GetControlInDirection_Down_Should_Scroll_If_Partially_Visible()
-////            {
-////                var target = CreateTarget();
-////                var scroller = (TestScroller)target.Parent;
-
-////                scroller.Width = 100;
-////                scroller.Height = 95;
-////                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-////                var from = target.Panel.Children[8];
-////                var result = ((ILogicalScrollable)target).GetControlInDirection(
-////                    NavigationDirection.Down,
-////                    from);
-
-////                Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-////                Assert.Same(target.Panel.Children[8], result);
-////            }
-
-////            [Fact]
-////            public void GetControlInDirection_Up_Should_Scroll_If_Partially_Visible_Item_Is_Currently_Shown()
-////            {
-////                var target = CreateTarget();
-////                var scroller = (TestScroller)target.Parent;
-
-////                scroller.Width = 100;
-////                scroller.Height = 95;
-////                scroller.LayoutManager.ExecuteInitialLayoutPass();
-////                ((ILogicalScrollable)target).Offset = new Vector(0, 11);
-
-////                var from = target.Panel.Children[1];
-////                var result = ((ILogicalScrollable)target).GetControlInDirection(
-////                    NavigationDirection.Up,
-////                    from);
-
-////                Assert.Equal(new Vector(0, 10), ((ILogicalScrollable)target).Offset);
-////                Assert.Same(target.Panel.Children[0], result);
-////            }
-
-////            [Fact]
-////            public void Should_Return_Horizontal_Extent_And_Viewport()
-////            {
-////                var target = CreateTarget();
-
-////                target.ApplyTemplate();
-////                target.Measure(new Size(5, 100));
-////                target.Arrange(new Rect(0, 0, 5, 100));
-
-////                Assert.Equal(new Size(10, 20), ((ILogicalScrollable)target).Extent);
-////                Assert.Equal(new Size(5, 10), ((ILogicalScrollable)target).Viewport);
-////            }
-
-////            [Fact]
-////            public void Horizontal_Scroll_Should_Update_Item_Position()
-////            {
-////                var target = CreateTarget();
-
-////                target.ApplyTemplate();
-
-////                target.Measure(new Size(5, 100));
-////                target.Arrange(new Rect(0, 0, 5, 100));
-
-////                ((ILogicalScrollable)target).Offset = new Vector(5, 0);
-
-////                target.Measure(new Size(5, 100));
-////                target.Arrange(new Rect(0, 0, 5, 100));
-
-////                Assert.Equal(new Rect(-5, 0, 10, 10), target.Panel.Children[0].Bounds);
-////            }
-////        }
-
-////        public class Horizontal
-////        {
-////            [Fact]
-////            public void GetControlInDirection_Right_Should_Return_Existing_Container_If_Materialized()
-////            {
-////                var target = CreateTarget(orientation: Orientation.Horizontal);
-////                var scroller = (TestScroller)target.Parent;
-
-////                scroller.Width = scroller.Height = 100;
-////                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-////                var from = target.Panel.Children[5];
-////                var result = ((ILogicalScrollable)target).GetControlInDirection(
-////                    NavigationDirection.Right,
-////                    from);
-
-////                Assert.Same(target.Panel.Children[6], result);
-////            }
-
-////            [Fact]
-////            public void GetControlInDirection_Right_Should_Scroll_If_Necessary()
-////            {
-////                var target = CreateTarget(orientation: Orientation.Horizontal);
-////                var scroller = (TestScroller)target.Parent;
-
-////                scroller.Width = scroller.Height = 100;
-////                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-////                var from = target.Panel.Children[9];
-////                var result = ((ILogicalScrollable)target).GetControlInDirection(
-////                    NavigationDirection.Right,
-////                    from);
-
-////                Assert.Equal(new Vector(1, 0), ((ILogicalScrollable)target).Offset);
-////                Assert.Same(target.Panel.Children[9], result);
-////            }
-
-////            [Fact]
-////            public void GetControlInDirection_Right_Should_Scroll_If_Partially_Visible()
-////            {
-////                var target = CreateTarget(orientation: Orientation.Horizontal);
-////                var scroller = (TestScroller)target.Parent;
-
-////                scroller.Width = 95;
-////                scroller.Height = 100;
-////                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-////                var from = target.Panel.Children[8];
-////                var result = ((ILogicalScrollable)target).GetControlInDirection(
-////                    NavigationDirection.Right,
-////                    from);
-
-////                Assert.Equal(new Vector(1, 0), ((ILogicalScrollable)target).Offset);
-////                Assert.Same(target.Panel.Children[8], result);
-////            }
-
-////            [Fact]
-////            public void GetControlInDirection_Left_Should_Scroll_If_Partially_Visible_Item_Is_Currently_Shown()
-////            {
-////                var target = CreateTarget(orientation: Orientation.Horizontal);
-////                var scroller = (TestScroller)target.Parent;
-
-////                scroller.Width = 95;
-////                scroller.Height = 100;
-////                scroller.LayoutManager.ExecuteInitialLayoutPass();
-////                ((ILogicalScrollable)target).Offset = new Vector(11, 0);
-
-////                var from = target.Panel.Children[1];
-////                var result = ((ILogicalScrollable)target).GetControlInDirection(
-////                    NavigationDirection.Left,
-////                    from);
-
-////                Assert.Equal(new Vector(10, 0), ((ILogicalScrollable)target).Offset);
-////                Assert.Same(target.Panel.Children[0], result);
-////            }
-////        }
-
-////        private static ItemsPresenter CreateTarget(
-////            Orientation orientation = Orientation.Vertical,
-////            int itemCount = 20,
-////            bool useAvaloniaList = false)
-////        {
-////            ItemsPresenter result;
-////            var itemsSource = Enumerable.Range(0, itemCount).Select(x => $"Item {x}");
-////            var items = useAvaloniaList ?
-////                (IEnumerable)new AvaloniaList<string>(itemsSource) :
-////                (IEnumerable)new ObservableCollection<string>(itemsSource);
-
-////            var scroller = new TestScroller
-////            {
-////                CanHorizontallyScroll = true,
-////                CanVerticallyScroll = true,
-////                Content = result = new TestItemsPresenter
-////                {
-////                    Items = items,
-////                    ItemsPanel = VirtualizingPanelTemplate(orientation),
-////                    DataTemplates = { StringDataTemplate() },
-////                    VirtualizationMode = ItemVirtualizationMode.Simple,
-////                }
-////            };
-
-////            scroller.UpdateChild();
-////            return result;
-////        }
-
-////        private static IDataTemplate StringDataTemplate()
-////        {
-////            return new FuncDataTemplate<string>((x, _) => new Canvas
-////            {
-////                Width = 10,
-////                Height = 10,
-////            });
-////        }
-
-////        private static ITemplate<Panel> VirtualizingPanelTemplate(
-////            Orientation orientation = Orientation.Vertical)
-////        {
-////            return new FuncTemplate<Panel>(() => new VirtualizingStackPanel
-////            {
-////                Orientation = orientation,
-////            });
-////        }
-
-////        private class TestScroller : ScrollContentPresenter, IRenderRoot, ILayoutRoot, ILogicalRoot
-////        {
-////            public TestScroller()
-////            {
-////                LayoutManager = new LayoutManager(this);
-////            }
-
-////            public IRenderer Renderer { get; }
-////            public Size ClientSize { get; }
-////            public double RenderScaling => 1;
-
-////            public Size MaxClientSize => Size.Infinity;
-
-////            public double LayoutScaling => 1;
-
-////            public ILayoutManager LayoutManager { get; }
-
-////            public IRenderTarget CreateRenderTarget() => throw new NotImplementedException();
-////            public void Invalidate(Rect rect) => throw new NotImplementedException();
-////            public Point PointToClient(PixelPoint p) => throw new NotImplementedException();
-////            public PixelPoint PointToScreen(Point p) => throw new NotImplementedException();
-////        }
-
-////        private class TestItemsPresenter : ItemsPresenter
-////        {
-////            protected override IItemContainerGenerator CreateItemContainerGenerator()
-////            {
-////                return new ItemContainerGenerator<TestContainer>(
-////                    this,
-////                    TestContainer.ContentProperty,
-////                    null);
-////            }
-////        }
-
-////        private class TestContainer : ContentControl
-////        {
-////            public TestContainer()
-////            {
-////                Template = new FuncControlTemplate<TestContainer>((parent, scope) => new ContentPresenter
-////                {
-////                    Name = "PART_ContentPresenter",
-////                    [~ContentPresenter.ContentProperty] = parent[~ContentControl.ContentProperty],
-////                    [~ContentPresenter.ContentTemplateProperty] = parent[~ContentControl.ContentTemplateProperty],
-////                }.RegisterInNameScope(scope));
-////            }
-////        }
-////    }
-////}

From 6f04196b84ca58f5dfa09676dc2c371c1a5dadb9 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 2 Dec 2022 23:26:36 +0100
Subject: [PATCH 25/64] Made TreeView work again and tests pass.

---
 .../Generators/TreeItemContainerGenerator.cs  |   32 +
 src/Avalonia.Controls/ItemsControl.cs         |   66 +-
 .../Presenters/ItemsPresenter.cs              |    8 +
 .../Primitives/HeaderedItemsControl.cs        |   16 +
 src/Avalonia.Controls/TreeView.cs             |  438 +--
 src/Avalonia.Controls/TreeViewItem.cs         |    5 +
 .../Controls/TreeViewItem.xaml                |    1 +
 .../Controls/TreeViewItem.xaml                |    1 +
 .../TreeViewTests.cs                          | 2866 ++++++++---------
 9 files changed, 1793 insertions(+), 1640 deletions(-)
 create mode 100644 src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs

diff --git a/src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs
new file mode 100644
index 00000000000..c1cae862a94
--- /dev/null
+++ b/src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs
@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+
+namespace Avalonia.Controls.Generators
+{
+    public class TreeItemContainerGenerator : ItemContainerGenerator
+    {
+        internal TreeItemContainerGenerator(TreeView owner)
+            : base(owner)
+        {
+            Index = new TreeContainerIndex(owner);
+        }
+
+        public TreeContainerIndex Index { get; }
+    }
+
+    public class TreeContainerIndex
+    {
+        private readonly TreeView _owner;
+
+        internal TreeContainerIndex(TreeView owner) => _owner = owner;
+
+        [Obsolete("Use TreeView.GetRealizedTreeContainers")]
+        public IEnumerable<Control> Containers => _owner.GetRealizedTreeContainers();
+
+        [Obsolete("Use TreeView.TreeContainerFromItem")]
+        public Control? ContainerFromItem(object item) => _owner.TreeContainerFromItem(item);
+
+        [Obsolete("Use TreeView.TreeItemFromContainer")]
+        public object? ItemFromContainer(Control container) => _owner.TreeItemFromContainer(container);
+    }
+}
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index e07eea57ef9..645abf50b30 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -107,7 +107,12 @@ public ItemsControl()
         /// <summary>
         /// Gets the <see cref="ItemContainerGenerator"/> for the control.
         /// </summary>
-        public ItemContainerGenerator ItemContainerGenerator => _itemContainerGenerator ??= new(this);
+        public ItemContainerGenerator ItemContainerGenerator
+        {
+#pragma warning disable CS0612 // Type or member is obsolete
+            get => _itemContainerGenerator ??= CreateItemContainerGenerator();
+#pragma warning restore CS0612 // Type or member is obsolete
+        }
 
         /// <summary>
         /// Gets or sets the items to display.
@@ -188,7 +193,8 @@ event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexCh
         /// </returns>
         public Control? ContainerFromItem(object item)
         {
-            throw new NotImplementedException();
+            var index = Items?.IndexOf(item) ?? -1;
+            return index >= 0 ? ContainerFromIndex(index) : null;
         }
 
         /// <summary>
@@ -210,8 +216,8 @@ event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexCh
         /// </returns>
         public object? ItemFromContainer(Control container)
         {
-            // TODO: Should this throw or return null of container isn't a container?
-            throw new NotImplementedException();
+            var index = IndexFromContainer(container);
+            return index >= 0 && index < ItemCount ? Items!.ElementAt(index) : null;
         }
 
         /// <summary>
@@ -273,6 +279,8 @@ protected internal virtual void PrepareContainerForItemOverride(Control containe
             if (container == item)
                 return;
 
+            var itemTemplate = GetEffectiveItemTemplate();
+
             if (container is HeaderedContentControl hcc)
             {
                 hcc.Content = item;
@@ -282,20 +290,43 @@ protected internal virtual void PrepareContainerForItemOverride(Control containe
                 else if (item is not Visual)
                     hcc.Header = item;
 
-                if (GetEffectiveItemTemplate() is { } it)
-                    hcc.HeaderTemplate = it;
+                if (itemTemplate is not null)
+                    hcc.HeaderTemplate = itemTemplate;
             }
             else if (container is ContentControl cc)
             {
                 cc.Content = item;
-                if (GetEffectiveItemTemplate() is { } it)
-                    cc.ContentTemplate = it;
+                if (itemTemplate is not null)
+                    cc.ContentTemplate = itemTemplate;
             }
             else if (container is ContentPresenter p)
             {
                 p.Content = item;
-                if (GetEffectiveItemTemplate() is { } it)
-                    p.ContentTemplate = it;
+                if (itemTemplate is not null)
+                    p.ContentTemplate = itemTemplate;
+            }
+            else if (container is ItemsControl ic)
+            {
+                if (itemTemplate is not null)
+                    ic.ItemTemplate = itemTemplate;
+                if (ItemContainerTheme is { } ict)
+                    ic.ItemContainerTheme = ict;
+            }
+
+            // This condition is separate because HeaderedItemsControl needs to also run the
+            // ItemsControl preparation.
+            if (container is HeaderedItemsControl hic)
+            {
+                hic.Header = item;
+                hic.HeaderTemplate = itemTemplate;
+
+                var treeTemplate = (itemTemplate ?? hic.FindDataTemplate(item)) as ITreeDataTemplate;
+
+                if (treeTemplate is not null)
+                {
+                    if (item is not null && treeTemplate.ItemsSelector(item) is { } itemsBinding)
+                        BindingOperations.Apply(hic, ItemsProperty, itemsBinding, null);
+                }
             }
         }
 
@@ -316,6 +347,7 @@ protected virtual void ContainerIndexChangedOverride(Control container, int oldI
         /// <param name="container">The container element.</param>
         protected internal virtual void ClearContainerForItemOverride(Control container)
         {
+            // TODO: Remove HeaderedItemsControl.Items binding.
         }
 
         /// <summary>
@@ -486,6 +518,20 @@ protected virtual void ItemsCollectionChanged(object sender, NotifyCollectionCha
             }
         }
 
+        /// <summary>
+        /// Creates the <see cref="ItemContainerGenerator"/>
+        /// </summary>
+        /// <remarks>
+        /// This method is only present for backwards compatibility with 0.10.x in order for
+        /// TreeView to be able to create a <see cref="TreeItemContainerGenerator"/>. Can be
+        /// removed in 12.0.
+        /// </remarks>
+        [Obsolete]
+        private protected virtual ItemContainerGenerator CreateItemContainerGenerator()
+        {
+            return new ItemContainerGenerator(this);
+        }
+
         internal void AddLogicalChild(Control c) => LogicalChildren.Add(c);
         internal void RemoveLogicalChild(Control c) => LogicalChildren.Remove(c);
 
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
index f11d803fc55..0091bbd48d0 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
@@ -3,6 +3,7 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Reflection;
+using Avalonia.Input;
 
 namespace Avalonia.Controls.Presenters
 {
@@ -19,6 +20,13 @@ public class ItemsPresenter : Control
 
         private PanelContainerGenerator? _generator;
 
+        static ItemsPresenter()
+        {
+            KeyboardNavigation.TabNavigationProperty.OverrideDefaultValue(
+                typeof(ItemsPresenter),
+                KeyboardNavigationMode.Once);
+        }
+
         /// <summary>
         /// Gets or sets a template which creates the <see cref="Panel"/> used to display the items.
         /// </summary>
diff --git a/src/Avalonia.Controls/Primitives/HeaderedItemsControl.cs b/src/Avalonia.Controls/Primitives/HeaderedItemsControl.cs
index 2f051c4fda4..71ae7a5bf6d 100644
--- a/src/Avalonia.Controls/Primitives/HeaderedItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/HeaderedItemsControl.cs
@@ -1,5 +1,6 @@
 using Avalonia.Collections;
 using Avalonia.Controls.Presenters;
+using Avalonia.Controls.Templates;
 using Avalonia.LogicalTree;
 
 namespace Avalonia.Controls.Primitives
@@ -15,6 +16,12 @@ public class HeaderedItemsControl : ItemsControl, IContentPresenterHost
         public static readonly StyledProperty<object?> HeaderProperty =
             HeaderedContentControl.HeaderProperty.AddOwner<HeaderedItemsControl>();
 
+        /// <summary>
+        /// Defines the <see cref="HeaderTemplate"/> property.
+        /// </summary>
+        public static readonly StyledProperty<IDataTemplate?> HeaderTemplateProperty =
+            AvaloniaProperty.Register<HeaderedItemsControl, IDataTemplate?>(nameof(HeaderTemplate));
+
         /// <summary>
         /// Initializes static members of the <see cref="ContentControl"/> class.
         /// </summary>
@@ -32,6 +39,15 @@ public object? Header
             set { SetValue(HeaderProperty, value); }
         }
 
+        /// <summary>
+        /// Gets or sets the data template used to display the header content of the control.
+        /// </summary>
+        public IDataTemplate? HeaderTemplate
+        {
+            get => GetValue(HeaderTemplateProperty);
+            set => SetValue(HeaderTemplateProperty, value);
+        }
+
         /// <summary>
         /// Gets the header presenter from the control's template.
         /// </summary>
diff --git a/src/Avalonia.Controls/TreeView.cs b/src/Avalonia.Controls/TreeView.cs
index 6336219fb63..c3e891149a9 100644
--- a/src/Avalonia.Controls/TreeView.cs
+++ b/src/Avalonia.Controls/TreeView.cs
@@ -75,6 +75,12 @@ public event EventHandler<SelectionChangedEventArgs>? SelectionChanged
             remove => RemoveHandler(SelectingItemsControl.SelectionChangedEvent, value);
         }
 
+        /// <summary>
+        /// Gets the <see cref="TreeItemContainerGenerator"/> for the tree view.
+        /// </summary>
+        public new TreeItemContainerGenerator ItemContainerGenerator =>
+            (TreeItemContainerGenerator)base.ItemContainerGenerator;
+
         /// <summary>
         /// Gets or sets a value indicating whether to automatically scroll to newly selected items.
         /// </summary>
@@ -182,8 +188,25 @@ public void ExpandSubTree(TreeViewItem item)
         /// </remarks>
         public void SelectAll()
         {
-            throw new NotImplementedException();
-            ////SynchronizeItems(SelectedItems, ItemContainerGenerator.Index!.Items);
+            var allItems = new List<object>();
+
+            void AddItems(ItemsControl itemsControl)
+            {
+                if (itemsControl.Items is { } items)
+                {
+                    foreach (var item in items)
+                        allItems.Add(item);
+                }
+
+                foreach (var child in itemsControl.GetRealizedContainers())
+                {
+                    if (child is ItemsControl childItemsControl)
+                        AddItems(childItemsControl);
+                }
+            }
+
+            AddItems(this);
+            SynchronizeItems(SelectedItems, allItems);
         }
 
         /// <summary>
@@ -194,6 +217,62 @@ public void UnselectAll()
             SelectedItems.Clear();
         }
 
+        public IEnumerable<Control> GetRealizedTreeContainers()
+        {
+            static IEnumerable<Control> GetRealizedContainers(ItemsControl itemsControl)
+            {
+                foreach (var container in itemsControl.GetRealizedContainers())
+                {
+                    yield return container;
+                    if (container is ItemsControl itemsControlContainer)
+                        foreach (var child in GetRealizedContainers(itemsControlContainer))
+                            yield return child;
+                }
+            }
+
+            return GetRealizedContainers(this);
+        }
+
+        public Control? TreeContainerFromItem(object item)
+        {
+            static Control? TreeContainerFromItem(ItemsControl itemsControl, object item)
+            {
+                if (itemsControl.ContainerFromItem(item) is { } container)
+                    return container;
+
+                foreach (var child in itemsControl.GetRealizedContainers())
+                {
+                    if (child is ItemsControl childItemsControl &&
+                        TreeContainerFromItem(childItemsControl, item) is { } childContainer)
+                        return childContainer;
+                }
+
+                return null;
+            }
+
+            return TreeContainerFromItem(this, item);
+        }
+
+        public object? TreeItemFromContainer(Control container)
+        {
+            static object? TreeItemFromContainer(ItemsControl itemsControl, Control container)
+            {
+                if (itemsControl.ItemFromContainer(container) is { } item)
+                    return item;
+
+                foreach (var child in itemsControl.GetRealizedContainers())
+                {
+                    if (child is ItemsControl childItemsControl &&
+                        TreeItemFromContainer(childItemsControl, container) is { } childContainer)
+                        return childContainer;
+                }
+
+                return null;
+            }
+
+            return TreeItemFromContainer(this, container);
+        }
+
         /// <summary>
         /// Subscribes to the <see cref="SelectedItems"/> CollectionChanged event, if any.
         /// </summary>
@@ -277,10 +356,9 @@ private void SelectedItemsCollectionChanged(object? sender, NotifyCollectionChan
                     break;
                 case NotifyCollectionChangedAction.Reset:
 
-                    foreach (var child in LogicalChildren)
+                    foreach (var container in GetRealizedTreeContainers())
                     {
-                        if (child is Control container && IndexFromContainer(container) != -1)
-                            MarkContainerSelected(container, false);
+                        MarkContainerSelected(container, false);
                     }
 
                     if (SelectedItems.Count > 0)
@@ -333,7 +411,7 @@ private void SelectedItemsCollectionChanged(object? sender, NotifyCollectionChan
 
         private void MarkItemSelected(object item, bool selected)
         {
-            var container = ContainerFromItem(item)!;
+            var container = TreeContainerFromItem(item)!;
 
             MarkContainerSelected(container, selected);
         }
@@ -366,6 +444,7 @@ private void UnsubscribeFromSelectedItems()
                 incc.CollectionChanged -= SelectedItemsCollectionChanged;
             }
         }
+        
         (bool handled, IInputElement? next) ICustomKeyboardNavigation.GetNext(IInputElement element,
             NavigationDirection direction)
         {
@@ -374,7 +453,7 @@ private void UnsubscribeFromSelectedItems()
                 if (!this.IsVisualAncestorOf((Visual)element))
                 {
                     var result = _selectedItem != null ?
-                        ContainerFromItem(_selectedItem) :
+                        TreeContainerFromItem(_selectedItem) :
                         ContainerFromIndex(0);
                     
                     return (result != null, result); // SelectedItem may not be in the treeview.
@@ -386,6 +465,9 @@ private void UnsubscribeFromSelectedItems()
             return (false, null);
         }
 
+        protected internal override Control CreateContainerOverride() => new TreeViewItem();
+        protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is TreeViewItem;
+
         /// <inheritdoc/>
         protected override void OnGotFocus(GotFocusEventArgs e)
         {
@@ -441,54 +523,58 @@ protected override void OnKeyDown(KeyEventArgs e)
             NavigationDirection direction,
             bool intoChildren)
         {
-            throw new NotImplementedException();
-            ////IItemContainerGenerator? parentGenerator = GetParentContainerGenerator(from);
-
-            ////if (parentGenerator == null)
-            ////{
-            ////    return null;
-            ////}
-
-            ////var index = from is not null ? parentGenerator.IndexFromContainer(from) : -1;
-            ////var parent = from?.Parent as ItemsControl;
-            ////TreeViewItem? result = null;
-
-            ////switch (direction)
-            ////{
-            ////    case NavigationDirection.Up:
-            ////        if (index > 0)
-            ////        {
-            ////            var previous = (TreeViewItem)parentGenerator.ContainerFromIndex(index - 1)!;
-            ////            result = previous.IsExpanded && previous.ItemCount > 0 ?
-            ////                (TreeViewItem)previous.ItemContainerGenerator.ContainerFromIndex(previous.ItemCount - 1)! :
-            ////                previous;
-            ////        }
-            ////        else
-            ////        {
-            ////            result = from?.Parent as TreeViewItem;
-            ////        }
-
-            ////        break;
-
-            ////    case NavigationDirection.Down:
-            ////    case NavigationDirection.Right:
-            ////        if (from?.IsExpanded == true && intoChildren && from.ItemCount > 0)
-            ////        {
-            ////            result = (TreeViewItem)from.ItemContainerGenerator.ContainerFromIndex(0)!;
-            ////        }
-            ////        else if (index < parent?.ItemCount - 1)
-            ////        {
-            ////            result = (TreeViewItem)parentGenerator.ContainerFromIndex(index + 1)!;
-            ////        }
-            ////        else if (parent is TreeViewItem parentItem)
-            ////        {
-            ////            return GetContainerInDirection(parentItem, direction, false);
-            ////        }
-
-            ////        break;
-            ////}
-
-            ////return result;
+            var parentItemsControl = from?.Parent switch
+            {
+                TreeView tv => (ItemsControl)tv,
+                TreeViewItem i => i,
+                _ => null
+            };
+
+            if (parentItemsControl == null)
+            {
+                return null;
+            }
+
+            var index = from is not null ? parentItemsControl.IndexFromContainer(from) : -1;
+            var parent = from?.Parent as ItemsControl;
+            TreeViewItem? result = null;
+
+            switch (direction)
+            {
+                case NavigationDirection.Up:
+                    if (index > 0)
+                    {
+                        var previous = (TreeViewItem)parentItemsControl.ContainerFromIndex(index - 1)!;
+                        result = previous.IsExpanded && previous.ItemCount > 0 ?
+                            (TreeViewItem)previous.ItemContainerGenerator.ContainerFromIndex(previous.ItemCount - 1)! :
+                            previous;
+                    }
+                    else
+                    {
+                        result = from?.Parent as TreeViewItem;
+                    }
+
+                    break;
+
+                case NavigationDirection.Down:
+                case NavigationDirection.Right:
+                    if (from?.IsExpanded == true && intoChildren && from.ItemCount > 0)
+                    {
+                        result = (TreeViewItem)from.ItemContainerGenerator.ContainerFromIndex(0)!;
+                    }
+                    else if (index < parent?.ItemCount - 1)
+                    {
+                        result = (TreeViewItem)parentItemsControl.ContainerFromIndex(index + 1)!;
+                    }
+                    else if (parent is TreeViewItem parentItem)
+                    {
+                        return GetContainerInDirection(parentItem, direction, false);
+                    }
+
+                    break;
+            }
+
+            return result;
         }
 
         /// <inheritdoc/>
@@ -527,63 +613,68 @@ protected void UpdateSelectionFromContainer(
             bool toggleModifier = false,
             bool rightButton = false)
         {
-            throw new NotImplementedException();
-            ////var item = ItemContainerGenerator.Index!.ItemFromContainer(container);
-
-            ////if (item == null)
-            ////{
-            ////    return;
-            ////}
-
-            ////Control? selectedContainer = null;
-
-            ////if (SelectedItem != null)
-            ////{
-            ////    selectedContainer = ItemContainerGenerator.Index!.ContainerFromItem(SelectedItem);
-            ////}
-
-            ////var mode = SelectionMode;
-            ////var toggle = toggleModifier || mode.HasAllFlags(SelectionMode.Toggle);
-            ////var multi = mode.HasAllFlags(SelectionMode.Multiple);
-            ////var range = multi && rangeModifier && selectedContainer != null;
-
-            ////if (rightButton)
-            ////{
-            ////    if (!SelectedItems.Contains(item))
-            ////    {
-            ////        SelectSingleItem(item);
-            ////    }
-            ////}
-            ////else if (!toggle && !range)
-            ////{
-            ////    SelectSingleItem(item);
-            ////}
-            ////else if (multi && range)
-            ////{
-            ////    SynchronizeItems(
-            ////        SelectedItems,
-            ////        GetItemsInRange(selectedContainer as TreeViewItem, container as TreeViewItem));
-            ////}
-            ////else
-            ////{
-            ////    var i = SelectedItems.IndexOf(item);
-
-            ////    if (i != -1)
-            ////    {
-            ////        SelectedItems.Remove(item);
-            ////    }
-            ////    else
-            ////    {
-            ////        if (multi)
-            ////        {
-            ////            SelectedItems.Add(item);
-            ////        }
-            ////        else
-            ////        {
-            ////            SelectedItem = item;
-            ////        }
-            ////    }
-            ////}
+            var item = TreeItemFromContainer(container);
+
+            if (item == null)
+            {
+                return;
+            }
+
+            Control? selectedContainer = null;
+
+            if (SelectedItem != null)
+            {
+                selectedContainer = TreeContainerFromItem(SelectedItem);
+            }
+
+            var mode = SelectionMode;
+            var toggle = toggleModifier || mode.HasAllFlags(SelectionMode.Toggle);
+            var multi = mode.HasAllFlags(SelectionMode.Multiple);
+            var range = multi && rangeModifier && selectedContainer != null;
+
+            if (rightButton)
+            {
+                if (!SelectedItems.Contains(item))
+                {
+                    SelectSingleItem(item);
+                }
+            }
+            else if (!toggle && !range)
+            {
+                SelectSingleItem(item);
+            }
+            else if (multi && range)
+            {
+                SynchronizeItems(
+                    SelectedItems,
+                    GetItemsInRange(selectedContainer as TreeViewItem, container as TreeViewItem));
+            }
+            else
+            {
+                var i = SelectedItems.IndexOf(item);
+
+                if (i != -1)
+                {
+                    SelectedItems.Remove(item);
+                }
+                else
+                {
+                    if (multi)
+                    {
+                        SelectedItems.Add(item);
+                    }
+                    else
+                    {
+                        SelectedItem = item;
+                    }
+                }
+            }
+        }
+
+        [Obsolete]
+        private protected override ItemContainerGenerator CreateItemContainerGenerator()
+        {
+            return new TreeItemContainerGenerator(this);
         }
 
         /// <summary>
@@ -595,27 +686,24 @@ protected void UpdateSelectionFromContainer(
         /// <returns>Found first node.</returns>
         private static TreeViewItem? FindFirstNode(TreeView treeView, TreeViewItem nodeA, TreeViewItem nodeB)
         {
-            return FindInContainers(treeView.ItemContainerGenerator, nodeA, nodeB);
+            return FindInContainers(treeView, nodeA, nodeB);
         }
 
-        private static TreeViewItem? FindInContainers(ItemContainerGenerator containerGenerator,
+        private static TreeViewItem? FindInContainers(ItemsControl itemsControl,
             TreeViewItem nodeA,
             TreeViewItem nodeB)
         {
-            throw new NotImplementedException();
-            ////IEnumerable<ItemContainerInfo> containers = containerGenerator.Containers;
-
-            ////foreach (ItemContainerInfo container in containers)
-            ////{
-            ////    TreeViewItem? node = FindFirstNode(container.ContainerControl as TreeViewItem, nodeA, nodeB);
+            foreach (var container in itemsControl.GetRealizedContainers())
+            {
+                TreeViewItem? node = FindFirstNode(container as TreeViewItem, nodeA, nodeB);
 
-            ////    if (node != null)
-            ////    {
-            ////        return node;
-            ////    }
-            ////}
+                if (node != null)
+                {
+                    return node;
+                }
+            }
 
-            ////return null;
+            return null;
         }
 
         private static TreeViewItem? FindFirstNode(TreeViewItem? node, TreeViewItem nodeA, TreeViewItem nodeB)
@@ -632,7 +720,7 @@ protected void UpdateSelectionFromContainer(
                 return match;
             }
 
-            return FindInContainers(node.ItemContainerGenerator, nodeA, nodeB);
+            return FindInContainers(node, nodeA, nodeB);
         }
 
         /// <summary>
@@ -643,60 +731,59 @@ protected void UpdateSelectionFromContainer(
         /// <param name="to">To container.</param>
         private List<object> GetItemsInRange(TreeViewItem? from, TreeViewItem? to)
         {
-            throw new NotImplementedException();
-            ////var items = new List<object>();
+            var items = new List<object>();
 
-            ////if (from == null || to == null)
-            ////{
-            ////    return items;
-            ////}
+            if (from == null || to == null)
+            {
+                return items;
+            }
 
-            ////TreeViewItem? firstItem = FindFirstNode(this, from, to);
+            TreeViewItem? firstItem = FindFirstNode(this, from, to);
 
-            ////if (firstItem == null)
-            ////{
-            ////    return items;
-            ////}
+            if (firstItem == null)
+            {
+                return items;
+            }
 
-            ////bool wasReversed = false;
+            bool wasReversed = false;
 
-            ////if (firstItem == to)
-            ////{
-            ////    var temp = from;
+            if (firstItem == to)
+            {
+                var temp = from;
 
-            ////    from = to;
-            ////    to = temp;
+                from = to;
+                to = temp;
 
-            ////    wasReversed = true;
-            ////}
+                wasReversed = true;
+            }
 
-            ////TreeViewItem? node = from;
+            TreeViewItem? node = from;
 
-            ////while (node != to)
-            ////{
-            ////    var item = ItemContainerGenerator.Index!.ItemFromContainer(node);
+            while (node is not null && node != to)
+            {
+                var item = TreeItemFromContainer(node);
 
-            ////    if (item != null)
-            ////    {
-            ////        items.Add(item);
-            ////    }
+                if (item != null)
+                {
+                    items.Add(item);
+                }
 
-            ////    node = GetContainerInDirection(node, NavigationDirection.Down, true);
-            ////}
+                node = GetContainerInDirection(node, NavigationDirection.Down, true);
+            }
 
-            ////var toItem = ItemContainerGenerator.Index!.ItemFromContainer(to);
+            var toItem = TreeItemFromContainer(to);
 
-            ////if (toItem != null)
-            ////{
-            ////    items.Add(toItem);
-            ////}
+            if (toItem != null)
+            {
+                items.Add(toItem);
+            }
 
-            ////if (wasReversed)
-            ////{
-            ////    items.Reverse();
-            ////}
+            if (wasReversed)
+            {
+                items.Reverse();
+            }
 
-            ////return items;
+            return items;
         }
 
         /// <summary>
@@ -737,20 +824,11 @@ protected bool UpdateSelectionFromEventSource(
         /// <returns>The container or null if the event did not originate in a container.</returns>
         protected TreeViewItem? GetContainerFromEventSource(object eventSource)
         {
-            throw new NotImplementedException();
-            ////var item = ((Visual)eventSource).GetSelfAndVisualAncestors()
-            ////    .OfType<TreeViewItem>()
-            ////    .FirstOrDefault();
-
-            ////if (item != null)
-            ////{
-            ////    if (item.ItemContainerGenerator.Index == ItemContainerGenerator.Index)
-            ////    {
-            ////        return item;
-            ////    }
-            ////}
+            var item = ((Visual)eventSource).GetSelfAndVisualAncestors()
+                .OfType<TreeViewItem>()
+                .FirstOrDefault();
 
-            ////return null;
+            return item?.TreeViewOwner == this ? item : null;
         }
 
         /// <summary>
@@ -801,7 +879,7 @@ private void MarkContainerSelected(Control container, bool selected)
             }
             else
             {
-                container.Classes.Set(":selected", selected);
+                ((IPseudoClasses)container.Classes).Set(":selected", selected);
             }
         }
 
diff --git a/src/Avalonia.Controls/TreeViewItem.cs b/src/Avalonia.Controls/TreeViewItem.cs
index 097fe54f420..3ff34a14b1f 100644
--- a/src/Avalonia.Controls/TreeViewItem.cs
+++ b/src/Avalonia.Controls/TreeViewItem.cs
@@ -88,6 +88,11 @@ public int Level
             private set { SetAndRaise(LevelProperty, ref _level, value); }
         }
 
+        internal TreeView? TreeViewOwner => _treeView;
+
+        protected internal override Control CreateContainerOverride() => new TreeViewItem();
+        protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is TreeViewItem;
+
         /// <inheritdoc/>
         protected override void OnAttachedToLogicalTree(LogicalTreeAttachmentEventArgs e)
         {
diff --git a/src/Avalonia.Themes.Fluent/Controls/TreeViewItem.xaml b/src/Avalonia.Themes.Fluent/Controls/TreeViewItem.xaml
index 834c2245a8e..b2dc8615a9c 100644
--- a/src/Avalonia.Themes.Fluent/Controls/TreeViewItem.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/TreeViewItem.xaml
@@ -88,6 +88,7 @@
                                 Grid.Column="1"
                                 Focusable="False"
                                 Content="{TemplateBinding Header}"
+                                ContentTemplate="{TemplateBinding HeaderTemplate}"
                                 HorizontalAlignment="{TemplateBinding HorizontalAlignment}"
                                 VerticalAlignment="{TemplateBinding VerticalAlignment}"
                                 Margin="{TemplateBinding Padding}" />
diff --git a/src/Avalonia.Themes.Simple/Controls/TreeViewItem.xaml b/src/Avalonia.Themes.Simple/Controls/TreeViewItem.xaml
index c36bf4c6737..b75da2dd7b7 100644
--- a/src/Avalonia.Themes.Simple/Controls/TreeViewItem.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/TreeViewItem.xaml
@@ -58,6 +58,7 @@
                                 Padding="{TemplateBinding Padding}"
                                 HorizontalContentAlignment="{TemplateBinding HorizontalAlignment}"
                                 Content="{TemplateBinding Header}"
+                                ContentTemplate="{TemplateBinding HeaderTemplate}"
                                 Focusable="False" />
             </Grid>
           </Border>
diff --git a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
index 8ded57956ba..b9a6566116c 100644
--- a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
@@ -1,1475 +1,1441 @@
-////using System;
-////using System.Collections;
-////using System.Collections.Generic;
-////using System.Collections.ObjectModel;
-////using System.ComponentModel;
-////using System.Linq;
-////using System.Runtime.CompilerServices;
-////using Avalonia.Collections;
-////using Avalonia.Controls.Generators;
-////using Avalonia.Controls.Presenters;
-////using Avalonia.Controls.Templates;
-////using Avalonia.Data;
-////using Avalonia.Data.Core;
-////using Avalonia.Input;
-////using Avalonia.Input.Platform;
-////using Avalonia.Interactivity;
-////using Avalonia.LogicalTree;
-////using Avalonia.Styling;
-////using Avalonia.UnitTests;
-////using JetBrains.Annotations;
-////using Moq;
-////using Xunit;
-
-////namespace Avalonia.Controls.UnitTests
-////{
-////    public class TreeViewTests
-////    {
-////        MouseTestHelper _mouse = new MouseTestHelper();
-
-////        [Fact]
-////        public void Items_Should_Be_Created()
-////        {
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = CreateTestTreeData(),
-////            };
-
-////            var root = new TestRoot(target);
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-
-////            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
-////            Assert.Equal(new[] { "Child1", "Child2", "Child3" }, ExtractItemHeader(target, 1));
-////            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
-////        }
-
-////        [Fact]
-////        public void Items_Should_Be_Created_Using_ItemTemplate_If_Present()
-////        {
-////            TreeView target;
-
-////            var root = new TestRoot
-////            {
-////                Child = target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = CreateTestTreeData(),
-////                    ItemTemplate = new FuncTreeDataTemplate<Node>(
-////                        (_, __) => new Canvas(),
-////                        x => x.Children),
-////                }
-////            };
-
-////            ApplyTemplates(target);
-
-////            var items = target.ItemContainerGenerator.Index.Containers
-////                .OfType<TreeViewItem>()
-////                .ToList();
-
-////            Assert.Equal(5, items.Count);
-////            Assert.All(items, x => Assert.IsType<Canvas>(x.HeaderPresenter.Child));
-////        }
-
-////        [Fact]
-////        public void Items_Should_Be_Created_Using_ItemConatinerTheme_If_Present()
-////        {
-////            TreeView target;
-////            var theme = new ControlTheme(typeof(TreeViewItem));
-
-////            var root = new TestRoot
-////            {
-////                Child = target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = CreateTestTreeData(),
-////                    ItemContainerTheme = theme,
-////                    ItemTemplate = new FuncTreeDataTemplate<Node>(
-////                        (_, __) => new Canvas(),
-////                        x => x.Children),
-////                }
-////            };
-
-////            ApplyTemplates(target);
-
-////            var items = target.ItemContainerGenerator.Index.Containers
-////                .OfType<TreeViewItem>()
-////                .ToList();
-
-////            Assert.Equal(5, items.Count);
-////            Assert.All(items, x => Assert.Same(theme, x.ItemContainerTheme));
-////        }
-
-////        [Fact]
-////        public void Root_ItemContainerGenerator_Containers_Should_Be_Root_Containers()
-////        {
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = CreateTestTreeData(),
-////            };
-
-////            var root = new TestRoot(target);
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-
-////            var container = (TreeViewItem)target.ItemContainerGenerator.Containers.Single().ContainerControl;
-////            var header = (TextBlock)container.Header;
-////            Assert.Equal("Root", header.Text);
-////        }
-
-////        [Fact]
-////        public void Root_TreeContainerFromItem_Should_Return_Descendant_Item()
-////        {
-////            var tree = CreateTestTreeData();
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = tree,
-////            };
-
-////            // For TreeViewItem to find its parent TreeView, OnAttachedToLogicalTree needs
-////            // to be called, which requires an IStyleRoot.
-////            var root = new TestRoot();
-////            root.Child = target;
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-
-////            var container = target.ItemContainerGenerator.Index.ContainerFromItem(
-////                tree[0].Children[1].Children[0]);
-
-////            Assert.NotNull(container);
-
-////            var header = ((TreeViewItem)container).Header;
-////            var headerContent = ((TextBlock)header).Text;
-
-////            Assert.Equal("Grandchild2a", headerContent);
-////        }
-
-////        [Fact]
-////        public void Clicking_Item_Should_Select_It()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var item = tree[0].Children[1].Children[0];
-////                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
-
-////                Assert.NotNull(container);
-
-////                _mouse.Click(container);
-
-////                Assert.Equal(item, target.SelectedItem);
-////                Assert.True(container.IsSelected);
-////            }
-////        }
-
-////        [Fact]
-////        public void Clicking_WithControlModifier_Selected_Item_Should_Deselect_It()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var item = tree[0].Children[1].Children[0];
-////                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
-
-////                Assert.NotNull(container);
-
-////                target.SelectedItem = item;
-
-////                Assert.True(container.IsSelected);
-
-////                _mouse.Click(container, modifiers: KeyModifiers.Control);
-
-////                Assert.Null(target.SelectedItem);
-////                Assert.False(container.IsSelected);
-////            }
-////        }
-
-////        [Fact]
-////        public void Clicking_WithControlModifier_Not_Selected_Item_Should_Select_It()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree
-////                };
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+using System.Linq;
+using Avalonia.Collections;
+using Avalonia.Controls.Generators;
+using Avalonia.Controls.Presenters;
+using Avalonia.Controls.Templates;
+using Avalonia.Data;
+using Avalonia.Data.Core;
+using Avalonia.Input;
+using Avalonia.Input.Platform;
+using Avalonia.Interactivity;
+using Avalonia.LogicalTree;
+using Avalonia.Styling;
+using Avalonia.UnitTests;
+using Moq;
+using Xunit;
+
+namespace Avalonia.Controls.UnitTests
+{
+    public class TreeViewTests
+    {
+        MouseTestHelper _mouse = new MouseTestHelper();
+
+        [Fact]
+        public void Items_Should_Be_Created()
+        {
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = CreateTestTreeData(),
+            };
+
+            var root = new TestRoot(target);
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+
+            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
+            Assert.Equal(new[] { "Child1", "Child2", "Child3" }, ExtractItemHeader(target, 1));
+            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
+        }
+
+        [Fact]
+        public void Items_Should_Be_Created_Using_ItemTemplate_If_Present()
+        {
+            TreeView target;
+
+            var root = new TestRoot
+            {
+                Child = target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = CreateTestTreeData(),
+                    ItemTemplate = new FuncTreeDataTemplate<Node>(
+                        (_, __) => new Canvas(),
+                        x => x.Children),
+                }
+            };
+
+            ApplyTemplates(target);
+
+            var items = target.GetRealizedTreeContainers()
+                .OfType<TreeViewItem>()
+                .ToList();
+
+            Assert.Equal(5, items.Count);
+            Assert.All(items, x => Assert.IsType<Canvas>(x.HeaderPresenter.Child));
+        }
+
+        [Fact]
+        public void Items_Should_Be_Created_Using_ItemConatinerTheme_If_Present()
+        {
+            TreeView target;
+            var theme = new ControlTheme(typeof(TreeViewItem));
+
+            var root = new TestRoot
+            {
+                Child = target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = CreateTestTreeData(),
+                    ItemContainerTheme = theme,
+                    ItemTemplate = new FuncTreeDataTemplate<Node>(
+                        (_, __) => new Canvas(),
+                        x => x.Children),
+                }
+            };
+
+            ApplyTemplates(target);
+
+            var items = target.GetRealizedTreeContainers()
+                .OfType<TreeViewItem>()
+                .ToList();
+
+            Assert.Equal(5, items.Count);
+            Assert.All(items, x => Assert.Same(theme, x.ItemContainerTheme));
+        }
+
+        [Fact]
+        public void Root_ItemContainerGenerator_Containers_Should_Be_Root_Containers()
+        {
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = CreateTestTreeData(),
+            };
+
+            var root = new TestRoot(target);
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+
+            var container = (TreeViewItem)target.GetRealizedContainers().Single();
+            var header = (TextBlock)container.HeaderPresenter.Child;
+            Assert.Equal("Root", header.Text);
+        }
+
+        [Fact]
+        public void Root_TreeContainerFromItem_Should_Return_Descendant_Item()
+        {
+            var tree = CreateTestTreeData();
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = tree,
+            };
+
+            // For TreeViewItem to find its parent TreeView, OnAttachedToLogicalTree needs
+            // to be called, which requires an IStyleRoot.
+            var root = new TestRoot();
+            root.Child = target;
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+
+            var container = target.TreeContainerFromItem(tree[0].Children[1].Children[0]);
+
+            Assert.NotNull(container);
+
+            var header = ((TreeViewItem)container).HeaderPresenter;
+            var headerContent = ((TextBlock)header.Child).Text;
+
+            Assert.Equal("Grandchild2a", headerContent);
+        }
+
+        [Fact]
+        public void Clicking_Item_Should_Select_It()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var item = tree[0].Children[1].Children[0];
+                var container = (TreeViewItem)target.TreeContainerFromItem(item);
+
+                Assert.NotNull(container);
+
+                _mouse.Click(container);
+
+                Assert.Equal(item, target.SelectedItem);
+                Assert.True(container.IsSelected);
+            }
+        }
+
+        [Fact]
+        public void Clicking_WithControlModifier_Selected_Item_Should_Deselect_It()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree
+                };
 
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var item = tree[0].Children[1].Children[0];
+                var container = (TreeViewItem)target.TreeContainerFromItem(item);
+
+                Assert.NotNull(container);
+
+                target.SelectedItem = item;
+
+                Assert.True(container.IsSelected);
+
+                _mouse.Click(container, modifiers: KeyModifiers.Control);
+
+                Assert.Null(target.SelectedItem);
+                Assert.False(container.IsSelected);
+            }
+        }
+
+        [Fact]
+        public void Clicking_WithControlModifier_Not_Selected_Item_Should_Select_It()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree
+                };
 
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
 
-////                var item1 = tree[0].Children[1].Children[0];
-////                var container1 = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item1);
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
 
-////                var item2 = tree[0].Children[1];
-////                var container2 = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item2);
+                var item1 = tree[0].Children[1].Children[0];
+                var container1 = (TreeViewItem)target.TreeContainerFromItem(item1);
 
-////                Assert.NotNull(container1);
-////                Assert.NotNull(container2);
-
-////                target.SelectedItem = item1;
-
-////                Assert.True(container1.IsSelected);
-
-////                _mouse.Click(container2, modifiers: KeyModifiers.Control);
-
-////                Assert.Equal(item2, target.SelectedItem);
-////                Assert.False(container1.IsSelected);
-////                Assert.True(container2.IsSelected);
-////            }
-////        }
-
-////        [Fact]
-////        public void Clicking_WithControlModifier_Selected_Item_Should_Deselect_And_Remove_From_SelectedItems()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple
-////                };
+                var item2 = tree[0].Children[1];
+                var container2 = (TreeViewItem)target.TreeContainerFromItem(item2);
 
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
+                Assert.NotNull(container1);
+                Assert.NotNull(container2);
+
+                target.SelectedItem = item1;
+
+                Assert.True(container1.IsSelected);
+
+                _mouse.Click(container2, modifiers: KeyModifiers.Control);
+
+                Assert.Equal(item2, target.SelectedItem);
+                Assert.False(container1.IsSelected);
+                Assert.True(container2.IsSelected);
+            }
+        }
+
+        [Fact]
+        public void Clicking_WithControlModifier_Selected_Item_Should_Deselect_And_Remove_From_SelectedItems()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple
+                };
 
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
 
-////                var rootNode = tree[0];
-
-////                var item1 = rootNode.Children[0];
-////                var item2 = rootNode.Children.Last();
-
-////                var item1Container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item1);
-////                var item2Container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item2);
-
-////                ClickContainer(item1Container, KeyModifiers.Control);
-////                Assert.True(item1Container.IsSelected);
-
-////                ClickContainer(item2Container, KeyModifiers.Control);
-////                Assert.True(item2Container.IsSelected);
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
 
-////                Assert.Equal(new[] { item1, item2 }, target.SelectedItems.OfType<Node>());
+                var rootNode = tree[0];
+
+                var item1 = rootNode.Children[0];
+                var item2 = rootNode.Children.Last();
+
+                var item1Container = (TreeViewItem)target.TreeContainerFromItem(item1);
+                var item2Container = (TreeViewItem)target.TreeContainerFromItem(item2);
+
+                ClickContainer(item1Container, KeyModifiers.Control);
+                Assert.True(item1Container.IsSelected);
+
+                ClickContainer(item2Container, KeyModifiers.Control);
+                Assert.True(item2Container.IsSelected);
 
-////                ClickContainer(item1Container, KeyModifiers.Control);
-////                Assert.False(item1Container.IsSelected);
+                Assert.Equal(new[] { item1, item2 }, target.SelectedItems.OfType<Node>());
 
-////                Assert.DoesNotContain(item1, target.SelectedItems.OfType<Node>());
-////            }
-////        }
+                ClickContainer(item1Container, KeyModifiers.Control);
+                Assert.False(item1Container.IsSelected);
 
-////        [Fact]
-////        public void Clicking_WithShiftModifier_DownDirection_Should_Select_Range_Of_Items()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple
-////                };
+                Assert.DoesNotContain(item1, target.SelectedItems.OfType<Node>());
+            }
+        }
 
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
+        [Fact]
+        public void Clicking_WithShiftModifier_DownDirection_Should_Select_Range_Of_Items()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple
+                };
 
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
 
-////                var rootNode = tree[0];
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
 
-////                var from = rootNode.Children[0];
-////                var to = rootNode.Children.Last();
+                var rootNode = tree[0];
 
-////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+                var from = rootNode.Children[0];
+                var to = rootNode.Children.Last();
 
-////                ClickContainer(fromContainer, KeyModifiers.None);
+                var fromContainer = (TreeViewItem)target.TreeContainerFromItem(from);
+                var toContainer = (TreeViewItem)target.TreeContainerFromItem(to);
 
-////                Assert.True(fromContainer.IsSelected);
+                ClickContainer(fromContainer, KeyModifiers.None);
 
-////                ClickContainer(toContainer, KeyModifiers.Shift);
-////                AssertChildrenSelected(target, rootNode);
-////            }
-////        }
+                Assert.True(fromContainer.IsSelected);
 
-////        [Fact]
-////        public void Clicking_WithShiftModifier_UpDirection_Should_Select_Range_Of_Items()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
+                ClickContainer(toContainer, KeyModifiers.Shift);
+                AssertChildrenSelected(target, rootNode);
+            }
+        }
 
-////                var rootNode = tree[0];
-
-////                var from = rootNode.Children.Last();
-////                var to = rootNode.Children[0];
-
-////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-////                ClickContainer(fromContainer, KeyModifiers.None);
+        [Fact]
+        public void Clicking_WithShiftModifier_UpDirection_Should_Select_Range_Of_Items()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
 
-////                Assert.True(fromContainer.IsSelected);
+                var rootNode = tree[0];
+
+                var from = rootNode.Children.Last();
+                var to = rootNode.Children[0];
+
+                var fromContainer = (TreeViewItem)target.TreeContainerFromItem(from);
+                var toContainer = (TreeViewItem)target.TreeContainerFromItem(to);
+
+                ClickContainer(fromContainer, KeyModifiers.None);
 
-////                ClickContainer(toContainer, KeyModifiers.Shift);
-////                AssertChildrenSelected(target, rootNode);
-////            }
-////        }
+                Assert.True(fromContainer.IsSelected);
 
-////        [Fact]
-////        public void Clicking_First_Item_Of_SelectedItems_Should_Select_Only_It()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var rootNode = tree[0];
-
-////                var from = rootNode.Children.Last();
-////                var to = rootNode.Children[0];
-
-////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-////                ClickContainer(fromContainer, KeyModifiers.None);
-
-////                ClickContainer(toContainer, KeyModifiers.Shift);
-////                AssertChildrenSelected(target, rootNode);
-
-////                ClickContainer(fromContainer, KeyModifiers.None);
-
-////                Assert.True(fromContainer.IsSelected);
-
-////                foreach (var child in rootNode.Children)
-////                {
-////                    if (child == from)
-////                    {
-////                        continue;
-////                    }
-
-////                    var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(child);
-
-////                    Assert.False(container.IsSelected);
-////                }
-////            }
-////        }
-
-////        [Fact]
-////        public void Setting_SelectedItem_Should_Set_Container_Selected()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var item = tree[0].Children[1].Children[0];
-////                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
-
-////                Assert.NotNull(container);
-
-////                target.SelectedItem = item;
-
-////                Assert.True(container.IsSelected);
-////            }
-////        }
-
-////        [Fact]
-////        public void Setting_SelectedItem_Should_Raise_SelectedItemChanged_Event()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var item = tree[0].Children[1].Children[0];
-
-////                var called = false;
-////                target.SelectionChanged += (s, e) =>
-////                {
-////                    Assert.Empty(e.RemovedItems);
-////                    Assert.Equal(1, e.AddedItems.Count);
-////                    Assert.Same(item, e.AddedItems[0]);
-////                    called = true;
-////                };
-
-////                target.SelectedItem = item;
-////                Assert.True(called);
-////            }
-////        }
-
-////        [Fact]
-////        public void Bound_SelectedItem_Should_Not_Be_Cleared_when_Changing_Selection()
-////        {
-////            using (Application())
-////            {
-////                var dataContext = new TestDataContext();
-
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    DataContext = dataContext
-////                };
-
-////                target.Bind(TreeView.ItemsProperty, new Binding("Items"));
-////                target.Bind(TreeView.SelectedItemProperty, new Binding("SelectedItem"));
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-
-////                var selectedValues = new List<object>();
-
-////                dataContext.PropertyChanged += (_, e) =>
-////                {
-////                    if (e.PropertyName == nameof(TestDataContext.SelectedItem))
-////                        selectedValues.Add(dataContext.SelectedItem);
-////                };
-////                selectedValues.Add(dataContext.SelectedItem);
-
-////                _mouse.Click((Interactive)target.Presenter.Panel.Children[0], MouseButton.Left);
-////                _mouse.Click((Interactive)target.Presenter.Panel.Children[2], MouseButton.Left);
-
-////                Assert.Equal(3, selectedValues.Count);
-////                Assert.Equal(new[] { null, "Item 0", "Item 2" }, selectedValues.ToArray());
-////            }
-////        }
-
-////        [Fact]
-////        public void LogicalChildren_Should_Be_Set()
-////        {
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = new[] { "Foo", "Bar", "Baz " },
-////            };
-
-////            ApplyTemplates(target);
-
-////            var result = target.GetLogicalChildren()
-////                .OfType<TreeViewItem>()
-////                .Select(x => x.Header)
-////                .OfType<TextBlock>()
-////                .Select(x => x.Text)
-////                .ToList();
-
-////            Assert.Equal(new[] { "Foo", "Bar", "Baz " }, result);
-////        }
-
-////        [Fact]
-////        public void Removing_Item_Should_Remove_Itself_And_Children_From_Index()
-////        {
-////            var tree = CreateTestTreeData();
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = tree,
-////            };
-
-////            var root = new TestRoot();
-////            root.Child = target;
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-
-////            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
-
-////            tree[0].Children.RemoveAt(1);
-
-////            Assert.Equal(3, target.ItemContainerGenerator.Index.Containers.Count());
-////        }
-
-////        [Fact]
-////        public void DataContexts_Should_Be_Correctly_Set()
-////        {
-////            var items = new object[]
-////            {
-////                "Foo",
-////                new Node { Value = "Bar" },
-////                new TextBlock { Text = "Baz" },
-////                new TreeViewItem { Header = "Qux" },
-////            };
-
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                DataContext = "Base",
-////                DataTemplates =
-////                {
-////                    new FuncDataTemplate<Node>((x, _) => new Button { Content = x })
-////                },
-////                Items = items,
-////            };
-
-////            ApplyTemplates(target);
-
-////            var dataContexts = target.Presenter.Panel.Children
-////                .Cast<Control>()
-////                .Select(x => x.DataContext)
-////                .ToList();
-
-////            Assert.Equal(
-////                new object[] { items[0], items[1], "Base", "Base" },
-////                dataContexts);
-////        }
-
-////        [Fact]
-////        public void Control_Item_Should_Not_Be_NameScope()
-////        {
-////            var items = new object[]
-////            {
-////                new TreeViewItem(),
-////            };
-
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = items,
-////            };
-
-////            target.ApplyTemplate();
-////            target.Presenter.ApplyTemplate();
-
-////            var item = target.Presenter.Panel.LogicalChildren[0];
-////            Assert.Null(NameScope.GetNameScope((TreeViewItem)item));
-////        }
-
-////        [Fact]
-////        public void Should_React_To_Children_Changing()
-////        {
-////            var data = CreateTestTreeData();
-
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = data,
-////            };
-
-////            var root = new TestRoot(target);
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-
-////            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
-////            Assert.Equal(new[] { "Child1", "Child2", "Child3" }, ExtractItemHeader(target, 1));
-////            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
-
-////            // Make sure that the binding to Node.Children does not get collected.
-////            GC.Collect();
-
-////            data[0].Children = new AvaloniaList<Node>
-////            {
-////                new Node
-////                {
-////                    Value = "NewChild1",
-////                }
-////            };
-
-////            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
-////            Assert.Equal(new[] { "NewChild1" }, ExtractItemHeader(target, 1));
-////        }
-
-////        [Fact]
-////        public void Keyboard_Navigation_Should_Move_To_Last_Selected_Node()
-////        {
-////            using (Application())
-////            {
-////                var focus = FocusManager.Instance;
-////                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
-////                var data = CreateTestTreeData();
-
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = data,
-////                };
-
-////                var button = new Button();
-
-////                var root = new TestRoot
-////                {
-////                    Child = new StackPanel
-////                    {
-////                        Children = { target, button },
-////                    }
-////                };
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var item = data[0].Children[0];
-////                var node = target.ItemContainerGenerator.Index.ContainerFromItem(item);
-////                Assert.NotNull(node);
-
-////                target.SelectedItem = item;
-////                node.Focus();
-////                Assert.Same(node, focus.Current);
-
-////                navigation.Move(focus.Current, NavigationDirection.Next);
-////                Assert.Same(button, focus.Current);
-
-////                navigation.Move(focus.Current, NavigationDirection.Next);
-////                Assert.Same(node, focus.Current);
-////            }
-////        }
-
-////        [Fact]
-////        public void Keyboard_Navigation_Should_Not_Crash_If_Selected_Item_Is_not_In_Tree()
-////        {
-////            using (Application())
-////            {
-////                var focus = FocusManager.Instance;
-////                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
-////                var data = CreateTestTreeData();
-
-////                var selectedNode = new Node { Value = "Out of Tree Selected Item" };
-
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = data,
-////                    SelectedItem = selectedNode
-////                };
-
-////                var button = new Button();
-
-////                var root = new TestRoot
-////                {
-////                    Child = new StackPanel
-////                    {
-////                        Children = { target, button },
-////                    }
-////                };
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var item = data[0].Children[0];
-////                var node = target.ItemContainerGenerator.Index.ContainerFromItem(item);
-////                Assert.NotNull(node);
-
-////                target.SelectedItem = selectedNode;
-////                node.Focus();
-////                Assert.Same(node, focus.Current);
-
-////                var next = KeyboardNavigationHandler.GetNext(node, NavigationDirection.Previous);
-////            }
-////        }
-
-////        [Fact]
-////        public void Pressing_SelectAll_Gesture_Should_Select_All_Nodes()
-////        {
-////            using (UnitTestApplication.Start())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var rootNode = tree[0];
-
-////                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
-////                var selectAllGesture = keymap.SelectAll.First();
-
-////                var keyEvent = new KeyEventArgs
-////                {
-////                    RoutedEvent = InputElement.KeyDownEvent,
-////                    Key = selectAllGesture.Key,
-////                    KeyModifiers = selectAllGesture.KeyModifiers
-////                };
-
-////                target.RaiseEvent(keyEvent);
-
-////                AssertChildrenSelected(target, rootNode);
-////            }
-////        }
-
-////        [Fact]
-////        public void Pressing_SelectAll_Gesture_With_Downward_Range_Selected_Should_Select_All_Nodes()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var rootNode = tree[0];
-
-////                var from = rootNode.Children[0];
-////                var to = rootNode.Children.Last();
-
-////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-////                ClickContainer(fromContainer, KeyModifiers.None);
-////                ClickContainer(toContainer, KeyModifiers.Shift);
-
-////                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
-////                var selectAllGesture = keymap.SelectAll.First();
-
-////                var keyEvent = new KeyEventArgs
-////                {
-////                    RoutedEvent = InputElement.KeyDownEvent,
-////                    Key = selectAllGesture.Key,
-////                    KeyModifiers = selectAllGesture.KeyModifiers
-////                };
-
-////                target.RaiseEvent(keyEvent);
-
-////                AssertChildrenSelected(target, rootNode);
-////            }
-////        }
-
-////        [Fact]
-////        public void Pressing_SelectAll_Gesture_With_Upward_Range_Selected_Should_Select_All_Nodes()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var rootNode = tree[0];
-
-////                var from = rootNode.Children.Last();
-////                var to = rootNode.Children[0];
-
-////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-////                ClickContainer(fromContainer, KeyModifiers.None);
-////                ClickContainer(toContainer, KeyModifiers.Shift);
-
-////                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
-////                var selectAllGesture = keymap.SelectAll.First();
-
-////                var keyEvent = new KeyEventArgs
-////                {
-////                    RoutedEvent = InputElement.KeyDownEvent,
-////                    Key = selectAllGesture.Key,
-////                    KeyModifiers = selectAllGesture.KeyModifiers
-////                };
-
-////                target.RaiseEvent(keyEvent);
-
-////                AssertChildrenSelected(target, rootNode);
-////            }
-////        }
-
-////        [Fact]
-////        public void Right_Click_On_SelectedItem_Should_Not_Clear_Existing_Selection()
-////        {
-////            using (UnitTestApplication.Start())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple,
-////                };
-////                AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
-////                target.SelectAll();
-
-////                AssertChildrenSelected(target, tree[0]);
-////                Assert.Equal(5, target.SelectedItems.Count);
-
-////                _mouse.Click((Interactive)target.Presenter.Panel.Children[0], MouseButton.Right);
-
-////                Assert.Equal(5, target.SelectedItems.Count);
-////            }
-////        }
-
-////        [Fact]
-////        public void Right_Click_On_UnselectedItem_Should_Clear_Existing_Selection()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple,
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
-
-////                var rootNode = tree[0];
-////                var to = rootNode.Children[0];
-////                var then = rootNode.Children[1];
-
-////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(rootNode);
-////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-////                var thenContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(then);
-
-////                ClickContainer(fromContainer, KeyModifiers.None);
-////                ClickContainer(toContainer, KeyModifiers.Shift);
-
-////                Assert.Equal(2, target.SelectedItems.Count);
-
-////                _mouse.Click(thenContainer, MouseButton.Right);
-
-////                Assert.Equal(1, target.SelectedItems.Count);
-////            }
-////        }
-
-////        [Fact]
-////        public void Shift_Right_Click_Should_Not_Select_Multiple()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple,
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
-
-////                var rootNode = tree[0];
-////                var from = rootNode.Children[0];
-////                var to = rootNode.Children[1];
-////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-////                _mouse.Click(fromContainer);
-////                _mouse.Click(toContainer, MouseButton.Right, modifiers: KeyModifiers.Shift);
-
-////                Assert.Equal(1, target.SelectedItems.Count);
-////            }
-////        }
-
-////        [Fact]
-////        public void Ctrl_Right_Click_Should_Not_Select_Multiple()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple,
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
-
-////                var rootNode = tree[0];
-////                var from = rootNode.Children[0];
-////                var to = rootNode.Children[1];
-////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-////                _mouse.Click(fromContainer);
-////                _mouse.Click(toContainer, MouseButton.Right, modifiers: KeyModifiers.Control);
-
-////                Assert.Equal(1, target.SelectedItems.Count);
-////            }
-////        }
-
-////        [Fact]
-////        public void TreeViewItems_Level_Should_Be_Set()
-////        {
-////            var tree = CreateTestTreeData();
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = tree,
-////            };
-
-////            var visualRoot = new TestRoot();
-////            visualRoot.Child = target;
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-////            ExpandAll(target);
-
-////            Assert.Equal(0, GetItem(target, 0).Level);
-////            Assert.Equal(1, GetItem(target, 0, 0).Level);
-////            Assert.Equal(1, GetItem(target, 0, 1).Level);
-////            Assert.Equal(1, GetItem(target, 0, 2).Level);
-////            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
-////        }
-
-////        [Fact]
-////        public void TreeViewItems_Level_Should_Be_Set_For_Derived_TreeView()
-////        {
-////            var tree = CreateTestTreeData();
-////            var target = new DerivedTreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = tree,
-////            };
-
-////            var visualRoot = new TestRoot();
-////            visualRoot.Child = target;
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-////            ExpandAll(target);
-
-////            Assert.Equal(0, GetItem(target, 0).Level);
-////            Assert.Equal(1, GetItem(target, 0, 0).Level);
-////            Assert.Equal(1, GetItem(target, 0, 1).Level);
-////            Assert.Equal(1, GetItem(target, 0, 2).Level);
-////            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
-////        }
-
-////        [Fact]
-////        public void Adding_Node_To_Removed_And_ReAdded_Parent_Should_Not_Crash()
-////        {
-////            // Issue #2985
-////            var tree = CreateTestTreeData();
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = tree,
-////            };
-
-////            var visualRoot = new TestRoot();
-////            visualRoot.Child = target;
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-////            ExpandAll(target);
-
-////            var parent = tree[0];
-////            var node = parent.Children[1];
-
-////            parent.Children.Remove(node);
-////            parent.Children.Add(node);
-
-////            var item = target.ItemContainerGenerator.Index.ContainerFromItem(node);
-////            ApplyTemplates(new[] { item });
-
-////            // #2985 causes ArgumentException here.
-////            node.Children.Add(new Node());
-////        }
-
-////        [Fact]
-////        public void Auto_Expanding_In_Style_Should_Not_Break_Range_Selection()
-////        {
-////            // Issue #2980.
-////            using (Application())
-////            {
-////                var target = new DerivedTreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    SelectionMode = SelectionMode.Multiple,
-////                    Items = new List<Node>
-////                {
-////                    new Node { Value = "Root1", },
-////                    new Node { Value = "Root2", },
-////                },
-////                };
-
-////                var visualRoot = new TestRoot
-////                {
-////                    Styles =
-////                    {
-////                        new Style(x => x.OfType<TreeViewItem>())
-////                        {
-////                            Setters =
-////                            {
-////                                new Setter(TreeViewItem.IsExpandedProperty, true),
-////                            },
-////                        },
-////                    },
-////                    Child = target,
-////                };
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-
-////                _mouse.Click(GetItem(target, 0));
-////                _mouse.Click(GetItem(target, 1), modifiers: KeyModifiers.Shift);
-////            }
-////        }
-
-////        [Fact]
-////        public void Removing_TreeView_From_Root_Should_Preserve_TreeViewItems()
-////        {
-////            // Issue #3328
-////            var tree = CreateTestTreeData();
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = tree,
-////            };
-
-////            var root = new TestRoot();
-////            root.Child = target;
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-////            ExpandAll(target);
-
-////            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
-
-////            root.Child = null;
-
-////            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
-////            Assert.Equal(1, target.Presenter.Panel.Children.Count);
-
-////            var rootNode = Assert.IsType<TreeViewItem>(target.Presenter.Panel.Children[0]);
-////            Assert.Equal(3, rootNode.ItemContainerGenerator.Containers.Count());
-////            Assert.Equal(3, rootNode.Presenter.Panel.Children.Count);
-
-////            var child2Node = Assert.IsType<TreeViewItem>(rootNode.Presenter.Panel.Children[1]);
-////            Assert.Equal(1, child2Node.ItemContainerGenerator.Containers.Count());
-////            Assert.Equal(1, child2Node.Presenter.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Clearing_TreeView_Items_Clears_Index()
-////        {
-////            // Issue #3551
-////            var tree = CreateTestTreeData();
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = tree,
-////            };
-
-////            var root = new TestRoot();
-////            root.Child = target;
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-
-////            var rootNode = tree[0];
-////            var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(rootNode);
-
-////            Assert.NotNull(container);
-
-////            root.Child = null;
-
-////            tree.Clear();
-
-////            Assert.Empty(target.ItemContainerGenerator.Index.Containers);
-////        }
-
-////        [Fact]
-////        public void Can_Use_Derived_TreeViewItem()
-////        {
-////            var tree = CreateTestTreeData();
-////            var target = new DerivedTreeViewWithDerivedTreeViewItems
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = tree,
-////            };
-
-////            ApplyTemplates(target);
-
-////            // Verify that all items are DerivedTreeViewItem
-////            VerifyItemType(target.ItemContainerGenerator);
-
-////            void VerifyItemType(ITreeItemContainerGenerator containerGenerator)
-////            {
-////                foreach (var container in containerGenerator.Index.Containers)
-////                {
-////                    var item = Assert.IsType<DerivedTreeViewItem>(container);
-////                    if (item.ItemCount > 0)
-////                    {
-////                        VerifyItemType(item.ItemContainerGenerator);
-////                    }
-////                }
-////            }
-////        }
-
-////        private void ApplyTemplates(TreeView tree)
-////        {
-////            tree.ApplyTemplate();
-////            tree.Presenter.ApplyTemplate();
-////            ApplyTemplates(tree.Presenter.Panel.Children);
-////        }
-
-////        private void ApplyTemplates(IEnumerable<Control> controls)
-////        {
-////            foreach (TreeViewItem control in controls)
-////            {
-////                control.Template = CreateTreeViewItemTemplate();
-////                control.ApplyTemplate();
-////                control.Presenter.ApplyTemplate();
-////                control.HeaderPresenter.ApplyTemplate();
-////                ApplyTemplates(control.Presenter.Panel.Children);
-////            }
-////        }
-
-////        private TreeViewItem GetItem(TreeView target, params int[] indexes)
-////        {
-////            var c = (ItemsControl)target;
-
-////            foreach (var index in indexes)
-////            {
-////                var item = ((IList)c.Items)[index];
-////                c = (ItemsControl)target.ItemContainerGenerator.Index.ContainerFromItem(item);
-////            }
-
-////            return (TreeViewItem)c;
-////        }
-
-////        private IList<Node> CreateTestTreeData()
-////        {
-////            return new AvaloniaList<Node>
-////            {
-////                new Node
-////                {
-////                    Value = "Root",
-////                    Children = new AvaloniaList<Node>
-////                    {
-////                        new Node
-////                        {
-////                            Value = "Child1",
-////                        },
-////                        new Node
-////                        {
-////                            Value = "Child2",
-////                            Children = new AvaloniaList<Node>
-////                            {
-////                                new Node
-////                                {
-////                                    Value = "Grandchild2a",
-////                                },
-////                            },
-////                        },
-////                        new Node
-////                        {
-////                            Value = "Child3",
-////                        }
-////                    }
-////                }
-////            };
-////        }
-
-////        private void CreateNodeDataTemplate(Control control)
-////        {
-////            control.DataTemplates.Add(new TestTreeDataTemplate());
-////        }
-
-////        private IControlTemplate CreateTreeViewTemplate()
-////        {
-////            return new FuncControlTemplate<TreeView>((parent, scope) => new ItemsPresenter
-////            {
-////                Name = "PART_ItemsPresenter",
-////            }.RegisterInNameScope(scope));
-////        }
-
-////        private IControlTemplate CreateTreeViewItemTemplate()
-////        {
-////            return new FuncControlTemplate<TreeViewItem>((parent, scope) => new Panel
-////            {
-////                Children =
-////                {
-////                    new ContentPresenter
-////                    {
-////                        Name = "PART_HeaderPresenter",
-////                        [~ContentPresenter.ContentProperty] = parent[~TreeViewItem.HeaderProperty],
-////                    }.RegisterInNameScope(scope),
-////                    new ItemsPresenter
-////                    {
-////                        Name = "PART_ItemsPresenter",
-////                    }.RegisterInNameScope(scope)
-////                }
-////            });
-////        }
-
-////        private void ExpandAll(TreeView tree)
-////        {
-////            foreach (var i in tree.ItemContainerGenerator.Containers)
-////            {
-////                tree.ExpandSubTree((TreeViewItem)i.ContainerControl);
-////            }
-////        }
-
-////        private List<string> ExtractItemHeader(TreeView tree, int level)
-////        {
-////            return ExtractItemContent(tree.Presenter.Panel, 0, level)
-////                .Select(x => x.Header)
-////                .OfType<TextBlock>()
-////                .Select(x => x.Text)
-////                .ToList();
-////        }
-
-////        private IEnumerable<TreeViewItem> ExtractItemContent(Panel panel, int currentLevel, int level)
-////        {
-////            foreach (TreeViewItem container in panel.Children)
-////            {
-////                if (container.Template == null)
-////                {
-////                    container.Template = CreateTreeViewItemTemplate();
-////                    container.ApplyTemplate();
-////                }
-
-////                if (currentLevel == level)
-////                {
-////                    yield return container;
-////                }
-////                else
-////                {
-////                    foreach (var child in ExtractItemContent(container.Presenter.Panel, currentLevel + 1, level))
-////                    {
-////                        yield return child;
-////                    }
-////                }
-////            }
-////        }
-
-////        private void ClickContainer(Control container, KeyModifiers modifiers)
-////        {
-////            _mouse.Click(container, modifiers: modifiers);
-////        }
-
-////        private void AssertChildrenSelected(TreeView treeView, Node rootNode)
-////        {
-////            foreach (var child in rootNode.Children)
-////            {
-////                var container = (TreeViewItem)treeView.ItemContainerGenerator.Index.ContainerFromItem(child);
-
-////                Assert.True(container.IsSelected);
-////            }
-////        }
-
-////        private IDisposable Application()
-////        {
-////            return UnitTestApplication.Start(
-////                TestServices.MockThreadingInterface.With(
-////                    focusManager: new FocusManager(),
-////                    keyboardDevice: () => new KeyboardDevice(),
-////                    keyboardNavigation: new KeyboardNavigationHandler(),
-////                    inputManager: new InputManager()));
-////        }
-
-////        private class Node : NotifyingBase
-////        {
-////            private IAvaloniaList<Node> _children;
-
-////            public string Value { get; set; }
-
-////            public IAvaloniaList<Node> Children
-////            {
-////                get
-////                {
-////                    return _children;
-////                }
-
-////                set
-////                {
-////                    _children = value;
-////                    RaisePropertyChanged(nameof(Children));
-////                }
-////            }
-////        }
-
-////        private class TestTreeDataTemplate : ITreeDataTemplate
-////        {
-////            public Control Build(object param)
-////            {
-////                var node = (Node)param;
-////                return new TextBlock { Text = node.Value };
-////            }
-
-////            public InstancedBinding ItemsSelector(object item)
-////            {
-////                var obs = ExpressionObserver.Create(item, o => (o as Node).Children);
-////                return InstancedBinding.OneWay(obs);
-////            }
-
-////            public bool Match(object data)
-////            {
-////                return data is Node;
-////            }
-////        }
-
-////        private class DerivedTreeView : TreeView
-////        {
-////        }
-
-////        private class DerivedTreeViewWithDerivedTreeViewItems : TreeView
-////        {
-////            protected override ITreeItemContainerGenerator CreateTreeItemContainerGenerator() =>
-////                CreateTreeItemContainerGenerator<DerivedTreeViewItem>();
-////        }
-
-////        private class DerivedTreeViewItem : TreeViewItem
-////        {
-////            protected override IItemContainerGenerator CreateItemContainerGenerator() => CreateTreeItemContainerGenerator<DerivedTreeViewItem>();
-////        }
-
-////        private class TestDataContext : INotifyPropertyChanged
-////        {
-////            private string _selectedItem;
-
-////            public TestDataContext()
-////            {
-////                Items = new ObservableCollection<string>(Enumerable.Range(0, 5).Select(i => $"Item {i}"));
-////            }
-
-////            public ObservableCollection<string> Items { get; }
-
-////            public string SelectedItem
-////            {
-////                get { return _selectedItem; }
-////                set
-////                {
-////                    _selectedItem = value;
-////                    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SelectedItem)));
-////                }
-////            }
-
-////            public event PropertyChangedEventHandler PropertyChanged;
-
-////        }
-////    }
-////}
+                ClickContainer(toContainer, KeyModifiers.Shift);
+                AssertChildrenSelected(target, rootNode);
+            }
+        }
+
+        [Fact]
+        public void Clicking_First_Item_Of_SelectedItems_Should_Select_Only_It()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var rootNode = tree[0];
+
+                var from = rootNode.Children.Last();
+                var to = rootNode.Children[0];
+
+                var fromContainer = (TreeViewItem)target.TreeContainerFromItem(from);
+                var toContainer = (TreeViewItem)target.TreeContainerFromItem(to);
+
+                ClickContainer(fromContainer, KeyModifiers.None);
+
+                ClickContainer(toContainer, KeyModifiers.Shift);
+                AssertChildrenSelected(target, rootNode);
+
+                ClickContainer(fromContainer, KeyModifiers.None);
+
+                Assert.True(fromContainer.IsSelected);
+
+                foreach (var child in rootNode.Children)
+                {
+                    if (child == from)
+                    {
+                        continue;
+                    }
+
+                    var container = (TreeViewItem)target.TreeContainerFromItem(child);
+
+                    Assert.False(container.IsSelected);
+                }
+            }
+        }
+
+        [Fact]
+        public void Setting_SelectedItem_Should_Set_Container_Selected()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var item = tree[0].Children[1].Children[0];
+                var container = (TreeViewItem)target.TreeContainerFromItem(item);
+
+                Assert.NotNull(container);
+
+                target.SelectedItem = item;
+
+                Assert.True(container.IsSelected);
+            }
+        }
+
+        [Fact]
+        public void Setting_SelectedItem_Should_Raise_SelectedItemChanged_Event()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var item = tree[0].Children[1].Children[0];
+
+                var called = false;
+                target.SelectionChanged += (s, e) =>
+                {
+                    Assert.Empty(e.RemovedItems);
+                    Assert.Equal(1, e.AddedItems.Count);
+                    Assert.Same(item, e.AddedItems[0]);
+                    called = true;
+                };
+
+                target.SelectedItem = item;
+                Assert.True(called);
+            }
+        }
+
+        [Fact]
+        public void Bound_SelectedItem_Should_Not_Be_Cleared_when_Changing_Selection()
+        {
+            using (Application())
+            {
+                var dataContext = new TestDataContext();
+
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    DataContext = dataContext
+                };
+
+                target.Bind(TreeView.ItemsProperty, new Binding("Items"));
+                target.Bind(TreeView.SelectedItemProperty, new Binding("SelectedItem"));
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+
+                var selectedValues = new List<object>();
+
+                dataContext.PropertyChanged += (_, e) =>
+                {
+                    if (e.PropertyName == nameof(TestDataContext.SelectedItem))
+                        selectedValues.Add(dataContext.SelectedItem);
+                };
+                selectedValues.Add(dataContext.SelectedItem);
+
+                _mouse.Click((Interactive)target.Presenter.Panel.Children[0], MouseButton.Left);
+                _mouse.Click((Interactive)target.Presenter.Panel.Children[2], MouseButton.Left);
+
+                Assert.Equal(3, selectedValues.Count);
+                Assert.Equal(new[] { null, "Item 0", "Item 2" }, selectedValues.ToArray());
+            }
+        }
+
+        [Fact]
+        public void LogicalChildren_Should_Be_Set()
+        {
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = new[] { "Foo", "Bar", "Baz " },
+            };
+
+            ApplyTemplates(target);
+
+            var result = target.GetLogicalChildren()
+                .OfType<TreeViewItem>()
+                .Select(x => x.HeaderPresenter.Child)
+                .OfType<TextBlock>()
+                .Select(x => x.Text)
+                .ToList();
+
+            Assert.Equal(new[] { "Foo", "Bar", "Baz " }, result);
+        }
+
+        [Fact]
+        public void DataContexts_Should_Be_Correctly_Set()
+        {
+            var items = new object[]
+            {
+                "Foo",
+                new Node { Value = "Bar" },
+                new TextBlock { Text = "Baz" },
+                new TreeViewItem { Header = "Qux" },
+            };
+
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                DataContext = "Base",
+                DataTemplates =
+                {
+                    new FuncDataTemplate<Node>((x, _) => new Button { Content = x })
+                },
+                Items = items,
+            };
+
+            ApplyTemplates(target);
+
+            var dataContexts = target.Presenter.Panel.Children
+                .Cast<Control>()
+                .Select(x => x.DataContext)
+                .ToList();
+
+            Assert.Equal(
+                new object[] { items[0], items[1], "Base", "Base" },
+                dataContexts);
+        }
+
+        [Fact]
+        public void Control_Item_Should_Not_Be_NameScope()
+        {
+            var items = new object[]
+            {
+                new TreeViewItem(),
+            };
+
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = items,
+            };
+
+            target.ApplyTemplate();
+            target.Presenter.ApplyTemplate();
+
+            var item = target.Presenter.Panel.LogicalChildren[0];
+            Assert.Null(NameScope.GetNameScope((TreeViewItem)item));
+        }
+
+        [Fact]
+        public void Should_React_To_Children_Changing()
+        {
+            var data = CreateTestTreeData();
+
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = data,
+            };
+
+            var root = new TestRoot(target);
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+
+            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
+            Assert.Equal(new[] { "Child1", "Child2", "Child3" }, ExtractItemHeader(target, 1));
+            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
+
+            // Make sure that the binding to Node.Children does not get collected.
+            GC.Collect();
+
+            data[0].Children = new AvaloniaList<Node>
+            {
+                new Node
+                {
+                    Value = "NewChild1",
+                }
+            };
+
+            ApplyTemplates(target);
+
+            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
+            Assert.Equal(new[] { "NewChild1" }, ExtractItemHeader(target, 1));
+        }
+
+        [Fact]
+        public void Keyboard_Navigation_Should_Move_To_Last_Selected_Node()
+        {
+            using (Application())
+            {
+                var focus = FocusManager.Instance;
+                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
+                var data = CreateTestTreeData();
+
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = data,
+                };
+
+                var button = new Button();
+
+                var root = new TestRoot
+                {
+                    Child = new StackPanel
+                    {
+                        Children = { target, button },
+                    }
+                };
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var item = data[0].Children[0];
+                var node = target.TreeContainerFromItem(item);
+                Assert.NotNull(node);
+
+                target.SelectedItem = item;
+                node.Focus();
+                Assert.Same(node, focus.Current);
+
+                navigation.Move(focus.Current, NavigationDirection.Next);
+                Assert.Same(button, focus.Current);
+
+                navigation.Move(focus.Current, NavigationDirection.Next);
+                Assert.Same(node, focus.Current);
+            }
+        }
+
+        [Fact]
+        public void Keyboard_Navigation_Should_Not_Crash_If_Selected_Item_Is_not_In_Tree()
+        {
+            using (Application())
+            {
+                var focus = FocusManager.Instance;
+                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
+                var data = CreateTestTreeData();
+
+                var selectedNode = new Node { Value = "Out of Tree Selected Item" };
+
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = data,
+                    SelectedItem = selectedNode
+                };
+
+                var button = new Button();
+
+                var root = new TestRoot
+                {
+                    Child = new StackPanel
+                    {
+                        Children = { target, button },
+                    }
+                };
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var item = data[0].Children[0];
+                var node = target.TreeContainerFromItem(item);
+                Assert.NotNull(node);
+
+                target.SelectedItem = selectedNode;
+                node.Focus();
+                Assert.Same(node, focus.Current);
+
+                var next = KeyboardNavigationHandler.GetNext(node, NavigationDirection.Previous);
+            }
+        }
+
+        [Fact]
+        public void Pressing_SelectAll_Gesture_Should_Select_All_Nodes()
+        {
+            using (UnitTestApplication.Start())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var rootNode = tree[0];
+
+                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
+                var selectAllGesture = keymap.SelectAll.First();
+
+                var keyEvent = new KeyEventArgs
+                {
+                    RoutedEvent = InputElement.KeyDownEvent,
+                    Key = selectAllGesture.Key,
+                    KeyModifiers = selectAllGesture.KeyModifiers
+                };
+
+                target.RaiseEvent(keyEvent);
+
+                AssertChildrenSelected(target, rootNode);
+            }
+        }
+
+        [Fact]
+        public void Pressing_SelectAll_Gesture_With_Downward_Range_Selected_Should_Select_All_Nodes()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var rootNode = tree[0];
+
+                var from = rootNode.Children[0];
+                var to = rootNode.Children.Last();
+
+                var fromContainer = (TreeViewItem)target.TreeContainerFromItem(from);
+                var toContainer = (TreeViewItem)target.TreeContainerFromItem(to);
+
+                ClickContainer(fromContainer, KeyModifiers.None);
+                ClickContainer(toContainer, KeyModifiers.Shift);
+
+                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
+                var selectAllGesture = keymap.SelectAll.First();
+
+                var keyEvent = new KeyEventArgs
+                {
+                    RoutedEvent = InputElement.KeyDownEvent,
+                    Key = selectAllGesture.Key,
+                    KeyModifiers = selectAllGesture.KeyModifiers
+                };
+
+                target.RaiseEvent(keyEvent);
+
+                AssertChildrenSelected(target, rootNode);
+            }
+        }
+
+        [Fact]
+        public void Pressing_SelectAll_Gesture_With_Upward_Range_Selected_Should_Select_All_Nodes()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var rootNode = tree[0];
+
+                var from = rootNode.Children.Last();
+                var to = rootNode.Children[0];
+
+                var fromContainer = (TreeViewItem)target.TreeContainerFromItem(from);
+                var toContainer = (TreeViewItem)target.TreeContainerFromItem(to);
+
+                ClickContainer(fromContainer, KeyModifiers.None);
+                ClickContainer(toContainer, KeyModifiers.Shift);
+
+                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
+                var selectAllGesture = keymap.SelectAll.First();
+
+                var keyEvent = new KeyEventArgs
+                {
+                    RoutedEvent = InputElement.KeyDownEvent,
+                    Key = selectAllGesture.Key,
+                    KeyModifiers = selectAllGesture.KeyModifiers
+                };
+
+                target.RaiseEvent(keyEvent);
+
+                AssertChildrenSelected(target, rootNode);
+            }
+        }
+
+        [Fact]
+        public void Right_Click_On_SelectedItem_Should_Not_Clear_Existing_Selection()
+        {
+            using (UnitTestApplication.Start())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple,
+                };
+                AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
+                target.SelectAll();
+
+                AssertChildrenSelected(target, tree[0]);
+                Assert.Equal(5, target.SelectedItems.Count);
+
+                _mouse.Click((Interactive)target.Presenter.Panel.Children[0], MouseButton.Right);
+
+                Assert.Equal(5, target.SelectedItems.Count);
+            }
+        }
+
+        [Fact]
+        public void Right_Click_On_UnselectedItem_Should_Clear_Existing_Selection()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple,
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
+
+                var rootNode = tree[0];
+                var to = rootNode.Children[0];
+                var then = rootNode.Children[1];
+
+                var fromContainer = (TreeViewItem)target.TreeContainerFromItem(rootNode);
+                var toContainer = (TreeViewItem)target.TreeContainerFromItem(to);
+                var thenContainer = (TreeViewItem)target.TreeContainerFromItem(then);
+
+                ClickContainer(fromContainer, KeyModifiers.None);
+                ClickContainer(toContainer, KeyModifiers.Shift);
+
+                Assert.Equal(2, target.SelectedItems.Count);
+
+                _mouse.Click(thenContainer, MouseButton.Right);
+
+                Assert.Equal(1, target.SelectedItems.Count);
+            }
+        }
+
+        [Fact]
+        public void Shift_Right_Click_Should_Not_Select_Multiple()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple,
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
+
+                var rootNode = tree[0];
+                var from = rootNode.Children[0];
+                var to = rootNode.Children[1];
+                var fromContainer = (TreeViewItem)target.TreeContainerFromItem(from);
+                var toContainer = (TreeViewItem)target.TreeContainerFromItem(to);
+
+                _mouse.Click(fromContainer);
+                _mouse.Click(toContainer, MouseButton.Right, modifiers: KeyModifiers.Shift);
+
+                Assert.Equal(1, target.SelectedItems.Count);
+            }
+        }
+
+        [Fact]
+        public void Ctrl_Right_Click_Should_Not_Select_Multiple()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple,
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
+
+                var rootNode = tree[0];
+                var from = rootNode.Children[0];
+                var to = rootNode.Children[1];
+                var fromContainer = (TreeViewItem)target.TreeContainerFromItem(from);
+                var toContainer = (TreeViewItem)target.TreeContainerFromItem(to);
+
+                _mouse.Click(fromContainer);
+                _mouse.Click(toContainer, MouseButton.Right, modifiers: KeyModifiers.Control);
+
+                Assert.Equal(1, target.SelectedItems.Count);
+            }
+        }
+
+        [Fact]
+        public void TreeViewItems_Level_Should_Be_Set()
+        {
+            var tree = CreateTestTreeData();
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = tree,
+            };
+
+            var visualRoot = new TestRoot();
+            visualRoot.Child = target;
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+            ExpandAll(target);
+
+            Assert.Equal(0, GetItem(target, 0).Level);
+            Assert.Equal(1, GetItem(target, 0, 0).Level);
+            Assert.Equal(1, GetItem(target, 0, 1).Level);
+            Assert.Equal(1, GetItem(target, 0, 2).Level);
+            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
+        }
+
+        [Fact]
+        public void TreeViewItems_Level_Should_Be_Set_For_Derived_TreeView()
+        {
+            var tree = CreateTestTreeData();
+            var target = new DerivedTreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = tree,
+            };
+
+            var visualRoot = new TestRoot();
+            visualRoot.Child = target;
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+            ExpandAll(target);
+
+            Assert.Equal(0, GetItem(target, 0).Level);
+            Assert.Equal(1, GetItem(target, 0, 0).Level);
+            Assert.Equal(1, GetItem(target, 0, 1).Level);
+            Assert.Equal(1, GetItem(target, 0, 2).Level);
+            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
+        }
+
+        [Fact]
+        public void Adding_Node_To_Removed_And_ReAdded_Parent_Should_Not_Crash()
+        {
+            // Issue #2985
+            var tree = CreateTestTreeData();
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = tree,
+            };
+
+            var visualRoot = new TestRoot();
+            visualRoot.Child = target;
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+            ExpandAll(target);
+
+            var parent = tree[0];
+            var node = parent.Children[1];
+
+            parent.Children.Remove(node);
+            parent.Children.Add(node);
+
+            var item = target.TreeContainerFromItem(node);
+            ApplyTemplates(new[] { item });
+
+            // #2985 causes ArgumentException here.
+            node.Children.Add(new Node());
+        }
+
+        [Fact]
+        public void Auto_Expanding_In_Style_Should_Not_Break_Range_Selection()
+        {
+            // Issue #2980.
+            using (Application())
+            {
+                var target = new DerivedTreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    SelectionMode = SelectionMode.Multiple,
+                    Items = new List<Node>
+                {
+                    new Node { Value = "Root1", },
+                    new Node { Value = "Root2", },
+                },
+                };
+
+                var visualRoot = new TestRoot
+                {
+                    Styles =
+                    {
+                        new Style(x => x.OfType<TreeViewItem>())
+                        {
+                            Setters =
+                            {
+                                new Setter(TreeViewItem.IsExpandedProperty, true),
+                            },
+                        },
+                    },
+                    Child = target,
+                };
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+
+                _mouse.Click(GetItem(target, 0));
+                _mouse.Click(GetItem(target, 1), modifiers: KeyModifiers.Shift);
+            }
+        }
+
+        [Fact]
+        public void Removing_TreeView_From_Root_Should_Preserve_TreeViewItems()
+        {
+            // Issue #3328
+            var tree = CreateTestTreeData();
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = tree,
+            };
+
+            var root = new TestRoot();
+            root.Child = target;
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+            ExpandAll(target);
+
+            Assert.Equal(5, target.GetRealizedTreeContainers().Count());
+
+            root.Child = null;
+
+            Assert.Equal(5, target.GetRealizedTreeContainers().Count());
+            Assert.Equal(1, target.Presenter.Panel.Children.Count);
+
+            var rootNode = Assert.IsType<TreeViewItem>(target.Presenter.Panel.Children[0]);
+            Assert.Equal(3, rootNode.GetRealizedContainers().Count());
+            Assert.Equal(3, rootNode.Presenter.Panel.Children.Count);
+
+            var child2Node = Assert.IsType<TreeViewItem>(rootNode.Presenter.Panel.Children[1]);
+            Assert.Equal(1, child2Node.GetRealizedContainers().Count());
+            Assert.Equal(1, child2Node.Presenter.Panel.Children.Count);
+        }
+
+        [Fact]
+        public void Clearing_TreeView_Items_Clears_Index()
+        {
+            // Issue #3551
+            var tree = CreateTestTreeData();
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = tree,
+            };
+
+            var root = new TestRoot();
+            root.Child = target;
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+
+            var rootNode = tree[0];
+            var container = (TreeViewItem)target.TreeContainerFromItem(rootNode);
+
+            Assert.NotNull(container);
+
+            root.Child = null;
+
+            tree.Clear();
+
+            Assert.Empty(target.GetRealizedContainers());
+        }
+
+        [Fact]
+        public void Can_Use_Derived_TreeViewItem()
+        {
+            var tree = CreateTestTreeData();
+            var target = new DerivedTreeViewWithDerivedTreeViewItems
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = tree,
+            };
+
+            ApplyTemplates(target);
+
+            // Verify that all items are DerivedTreeViewItem
+            foreach (var container in target.GetRealizedTreeContainers())
+            {
+                Assert.IsType<DerivedTreeViewItem>(container);
+            }
+        }
+
+        private void ApplyTemplates(TreeView tree)
+        {
+            tree.ApplyTemplate();
+            tree.Presenter.ApplyTemplate();
+            ApplyTemplates(tree.Presenter.Panel.Children);
+        }
+
+        private void ApplyTemplates(IEnumerable<Control> controls)
+        {
+            foreach (TreeViewItem control in controls)
+            {
+                control.Template = CreateTreeViewItemTemplate();
+                control.ApplyTemplate();
+                control.Presenter.ApplyTemplate();
+                ((ContentPresenter)control.HeaderPresenter).UpdateChild();
+                ApplyTemplates(control.Presenter.Panel.Children);
+            }
+        }
+
+        private TreeViewItem GetItem(TreeView target, params int[] indexes)
+        {
+            var c = (ItemsControl)target;
+
+            foreach (var index in indexes)
+            {
+                var item = ((IList)c.Items)[index];
+                c = (ItemsControl)target.TreeContainerFromItem(item);
+            }
+
+            return (TreeViewItem)c;
+        }
+
+        private IList<Node> CreateTestTreeData()
+        {
+            return new AvaloniaList<Node>
+            {
+                new Node
+                {
+                    Value = "Root",
+                    Children = new AvaloniaList<Node>
+                    {
+                        new Node
+                        {
+                            Value = "Child1",
+                        },
+                        new Node
+                        {
+                            Value = "Child2",
+                            Children = new AvaloniaList<Node>
+                            {
+                                new Node
+                                {
+                                    Value = "Grandchild2a",
+                                },
+                            },
+                        },
+                        new Node
+                        {
+                            Value = "Child3",
+                        }
+                    }
+                }
+            };
+        }
+
+        private void CreateNodeDataTemplate(Control control)
+        {
+            control.DataTemplates.Add(new TestTreeDataTemplate());
+        }
+
+        private IControlTemplate CreateTreeViewTemplate()
+        {
+            return new FuncControlTemplate<TreeView>((parent, scope) => new ItemsPresenter
+            {
+                Name = "PART_ItemsPresenter",
+            }.RegisterInNameScope(scope));
+        }
+
+        private IControlTemplate CreateTreeViewItemTemplate()
+        {
+            return new FuncControlTemplate<TreeViewItem>((parent, scope) => new Panel
+            {
+                Children =
+                {
+                    new ContentPresenter
+                    {
+                        Name = "PART_HeaderPresenter",
+                        [~ContentPresenter.ContentProperty] = parent[~TreeViewItem.HeaderProperty],
+                        [~ContentPresenter.ContentTemplateProperty] = parent[~TreeViewItem.HeaderTemplateProperty],
+                    }.RegisterInNameScope(scope),
+                    new ItemsPresenter
+                    {
+                        Name = "PART_ItemsPresenter",
+                    }.RegisterInNameScope(scope)
+                }
+            });
+        }
+
+        private void ExpandAll(TreeView tree)
+        {
+            foreach (var i in tree.GetRealizedContainers())
+            {
+                tree.ExpandSubTree((TreeViewItem)i);
+            }
+        }
+
+        private List<string> ExtractItemHeader(TreeView tree, int level)
+        {
+            return ExtractItemContent(tree.Presenter.Panel, 0, level)
+                .Select(x => x.HeaderPresenter.Child)
+                .OfType<TextBlock>()
+                .Select(x => x.Text)
+                .ToList();
+        }
+
+        private IEnumerable<TreeViewItem> ExtractItemContent(Panel panel, int currentLevel, int level)
+        {
+            foreach (TreeViewItem container in panel.Children)
+            {
+                if (container.Template == null)
+                {
+                    container.Template = CreateTreeViewItemTemplate();
+                    container.ApplyTemplate();
+                }
+
+                if (currentLevel == level)
+                {
+                    yield return container;
+                }
+                else
+                {
+                    foreach (var child in ExtractItemContent(container.Presenter.Panel, currentLevel + 1, level))
+                    {
+                        yield return child;
+                    }
+                }
+            }
+        }
+
+        private void ClickContainer(Control container, KeyModifiers modifiers)
+        {
+            _mouse.Click(container, modifiers: modifiers);
+        }
+
+        private void AssertChildrenSelected(TreeView treeView, Node rootNode)
+        {
+            foreach (var child in rootNode.Children)
+            {
+                var container = (TreeViewItem)treeView.TreeContainerFromItem(child);
+
+                Assert.True(container.IsSelected);
+            }
+        }
+
+        private IDisposable Application()
+        {
+            return UnitTestApplication.Start(
+                TestServices.MockThreadingInterface.With(
+                    focusManager: new FocusManager(),
+                    keyboardDevice: () => new KeyboardDevice(),
+                    keyboardNavigation: new KeyboardNavigationHandler(),
+                    inputManager: new InputManager()));
+        }
+
+        private class Node : NotifyingBase
+        {
+            private IAvaloniaList<Node> _children;
+
+            public string Value { get; set; }
+
+            public IAvaloniaList<Node> Children
+            {
+                get
+                {
+                    return _children;
+                }
+
+                set
+                {
+                    _children = value;
+                    RaisePropertyChanged(nameof(Children));
+                }
+            }
+        }
+
+        private class TestTreeDataTemplate : ITreeDataTemplate
+        {
+            public Control Build(object param)
+            {
+                var node = (Node)param;
+                return new TextBlock { Text = node.Value };
+            }
+
+            public InstancedBinding ItemsSelector(object item)
+            {
+                var obs = ExpressionObserver.Create(item, o => (o as Node).Children);
+                return InstancedBinding.OneWay(obs);
+            }
+
+            public bool Match(object data)
+            {
+                return data is Node;
+            }
+        }
+
+        private class DerivedTreeView : TreeView
+        {
+        }
+
+        private class DerivedTreeViewWithDerivedTreeViewItems : TreeView
+        {
+            protected internal override Control CreateContainerOverride() => new DerivedTreeViewItem();
+        }
+
+        private class DerivedTreeViewItem : TreeViewItem
+        {
+        }
+
+        private class TestDataContext : INotifyPropertyChanged
+        {
+            private string _selectedItem;
+
+            public TestDataContext()
+            {
+                Items = new ObservableCollection<string>(Enumerable.Range(0, 5).Select(i => $"Item {i}"));
+            }
+
+            public ObservableCollection<string> Items { get; }
+
+            public string SelectedItem
+            {
+                get { return _selectedItem; }
+                set
+                {
+                    _selectedItem = value;
+                    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SelectedItem)));
+                }
+            }
+
+            public event PropertyChangedEventHandler PropertyChanged;
+
+        }
+    }
+}

From 4a92fadd3404aed55abd4c92aaaa7a7f0025c33c Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sun, 4 Dec 2022 12:15:13 +0100
Subject: [PATCH 26/64] Fix StyleIncludeTests.

Wasn't finding `RelativeSource` type at times.
---
 src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github        | 2 +-
 .../Xaml/StyleIncludeTests.cs                               | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github b/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github
index 5e498f8bcca..491de981dd4 160000
--- a/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github
+++ b/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github
@@ -1 +1 @@
-Subproject commit 5e498f8bcca403a34aff5efc825cbb4e12b7fa8e
+Subproject commit 491de981dd4433ee58bc9540e2cd4a5d168f8168
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleIncludeTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleIncludeTests.cs
index d76e51f4198..929529e97a6 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleIncludeTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleIncludeTests.cs
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using Avalonia.Controls;
+using Avalonia.Data;
 using Avalonia.Markup.Xaml.Styling;
 using Avalonia.Markup.Xaml.XamlIl.Runtime;
 using Avalonia.Media;
@@ -15,6 +16,11 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml;
 
 public class StyleIncludeTests
 {
+    public StyleIncludeTests()
+    {
+        System.Runtime.CompilerServices.RuntimeHelpers.RunClassConstructor(typeof(RelativeSource).TypeHandle);
+    }
+
     [Fact]
     public void StyleInclude_Is_Built()
     {

From 84abb69b61208161336af2a54b523f3f64cf9c53 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sun, 4 Dec 2022 12:23:36 +0100
Subject: [PATCH 27/64] Reinstated DialogsPage.

---
 samples/ControlCatalog/Pages/DialogsPage.xaml |   2 +-
 .../ControlCatalog/Pages/DialogsPage.xaml.cs  | 590 +++++++++---------
 2 files changed, 296 insertions(+), 296 deletions(-)

diff --git a/samples/ControlCatalog/Pages/DialogsPage.xaml b/samples/ControlCatalog/Pages/DialogsPage.xaml
index cc23ef796ab..5325534909b 100644
--- a/samples/ControlCatalog/Pages/DialogsPage.xaml
+++ b/samples/ControlCatalog/Pages/DialogsPage.xaml
@@ -46,7 +46,7 @@
                Classes="h2"
                IsVisible="False"
                Text="Last picker results:" />
-    <ItemsPresenter x:Name="PickerLastResults" />
+    <ItemsControl x:Name="PickerLastResults" />
 
     <TextBox Name="BookmarkContainer" Watermark="Bookmark" />
     <TextBox Name="OpenedFileContent"
diff --git a/samples/ControlCatalog/Pages/DialogsPage.xaml.cs b/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
index 41a5b86ebda..3f1264fd326 100644
--- a/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
+++ b/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
@@ -24,301 +24,301 @@ public DialogsPage()
         {
             this.InitializeComponent();
 
-////            var results = this.Get<ItemsPresenter>("PickerLastResults");
-////            var resultsVisible = this.Get<TextBlock>("PickerLastResultsVisible");
-////            var bookmarkContainer = this.Get<TextBox>("BookmarkContainer");
-////            var openedFileContent = this.Get<TextBox>("OpenedFileContent");
-////            var openMultiple = this.Get<CheckBox>("OpenMultiple");
-
-////            IStorageFolder? lastSelectedDirectory = null;
-
-////            List<FileDialogFilter> GetFilters()
-////            {
-////                if (this.Get<CheckBox>("UseFilters").IsChecked != true)
-////                    return new List<FileDialogFilter>();
-////                return  new List<FileDialogFilter>
-////                {
-////                    new FileDialogFilter
-////                    {
-////                        Name = "Text files (.txt)", Extensions = new List<string> {"txt"}
-////                    },
-////                    new FileDialogFilter
-////                    {
-////                        Name = "All files",
-////                        Extensions = new List<string> {"*"}
-////                    }
-////                };
-////            }
-
-////            List<FilePickerFileType>? GetFileTypes()
-////            {
-////                if (this.Get<CheckBox>("UseFilters").IsChecked != true)
-////                    return null;
-////                return new List<FilePickerFileType>
-////                {
-////                    FilePickerFileTypes.All,
-////                    FilePickerFileTypes.TextPlain
-////                };
-////            }
-
-////            this.Get<Button>("OpenFile").Click += async delegate
-////            {
-////                // Almost guaranteed to exist
-////                var uri = Assembly.GetEntryAssembly()?.GetModules().FirstOrDefault()?.FullyQualifiedName;
-////                var initialFileName = uri == null ? null : System.IO.Path.GetFileName(uri);
-////                var initialDirectory = uri == null ? null : System.IO.Path.GetDirectoryName(uri);
-
-////                var result = await new OpenFileDialog()
-////                {
-////                    Title = "Open file",
-////                    Filters = GetFilters(),
-////                    Directory = initialDirectory,
-////                    InitialFileName = initialFileName
-////                }.ShowAsync(GetWindow());
-////                results.Items = result;
-////                resultsVisible.IsVisible = result?.Any() == true;
-////            };
-////            this.Get<Button>("OpenMultipleFiles").Click += async delegate
-////            {
-////                var result = await new OpenFileDialog()
-////                {
-////                    Title = "Open multiple files",
-////                    Filters = GetFilters(),
-////                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
-////                    AllowMultiple = true
-////                }.ShowAsync(GetWindow());
-////                results.Items = result;
-////                resultsVisible.IsVisible = result?.Any() == true;
-////            };
-////            this.Get<Button>("SaveFile").Click += async delegate
-////            {
-////                var filters = GetFilters();
-////                var result = await new SaveFileDialog()
-////                {
-////                    Title = "Save file",
-////                    Filters = filters,
-////                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
-////                    DefaultExtension = filters?.Any() == true ? "txt" : null,
-////                    InitialFileName = "test.txt"
-////                }.ShowAsync(GetWindow());
-////                results.Items = new[] { result };
-////                resultsVisible.IsVisible = result != null;
-////            };
-////            this.Get<Button>("SelectFolder").Click += async delegate
-////            {
-////                var result = await new OpenFolderDialog()
-////                {
-////                    Title = "Select folder",
-////                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null
-////                }.ShowAsync(GetWindow());
-////                if (string.IsNullOrEmpty(result))
-////                {
-////                    resultsVisible.IsVisible = false;
-////                }
-////                else
-////                {
-////                    lastSelectedDirectory = new BclStorageFolder(new System.IO.DirectoryInfo(result));
-////                    results.Items = new[] { result };
-////                    resultsVisible.IsVisible = true;
-////                }
-////            };
-////            this.Get<Button>("OpenBoth").Click += async delegate
-////            {
-////                var result = await new OpenFileDialog()
-////                {
-////                    Title = "Select both",
-////                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
-////                    AllowMultiple = true
-////                }.ShowManagedAsync(GetWindow(), new ManagedFileDialogOptions
-////                {
-////                    AllowDirectorySelection = true
-////                });
-////                results.Items = result;
-////                resultsVisible.IsVisible = result?.Any() == true;
-////            };
-////            this.Get<Button>("DecoratedWindow").Click += delegate
-////            {
-////                new DecoratedWindow().Show();
-////            };
-////            this.Get<Button>("DecoratedWindowDialog").Click += delegate
-////            {
-////                _ = new DecoratedWindow().ShowDialog(GetWindow());
-////            };
-////            this.Get<Button>("Dialog").Click += delegate
-////            {
-////                var window = CreateSampleWindow();
-////                window.Height = 200;
-////                _ = window.ShowDialog(GetWindow());
-////            };
-////            this.Get<Button>("DialogNoTaskbar").Click += delegate
-////            {
-////                var window = CreateSampleWindow();
-////                window.Height = 200;
-////                window.ShowInTaskbar = false;
-////                _ = window.ShowDialog(GetWindow());
-////            };
-////            this.Get<Button>("OwnedWindow").Click += delegate
-////            {
-////                var window = CreateSampleWindow();
-
-////                window.Show(GetWindow());
-////            };
-
-////            this.Get<Button>("OwnedWindowNoTaskbar").Click += delegate
-////            {
-////                var window = CreateSampleWindow();
-
-////                window.ShowInTaskbar = false;
-
-////                window.Show(GetWindow());
-////            };
-
-////            this.Get<Button>("OpenFilePicker").Click += async delegate
-////            {
-////                var result = await GetStorageProvider().OpenFilePickerAsync(new FilePickerOpenOptions()
-////                {
-////                    Title = "Open file",
-////                    FileTypeFilter = GetFileTypes(),
-////                    SuggestedStartLocation = lastSelectedDirectory,
-////                    AllowMultiple = openMultiple.IsChecked == true
-////                });
-
-////                await SetPickerResult(result);
-////            };
-////            this.Get<Button>("SaveFilePicker").Click += async delegate
-////            {
-////                var fileTypes = GetFileTypes();
-////                var file = await GetStorageProvider().SaveFilePickerAsync(new FilePickerSaveOptions()
-////                {
-////                    Title = "Save file",
-////                    FileTypeChoices = fileTypes,
-////                    SuggestedStartLocation = lastSelectedDirectory,
-////                    SuggestedFileName = "FileName",
-////                    DefaultExtension = fileTypes?.Any() == true ? "txt" : null,
-////                    ShowOverwritePrompt = false
-////                });
-
-////                if (file is not null && file.CanOpenWrite)
-////                {
-////                    // Sync disposal of StreamWriter is not supported on WASM
-////#if NET6_0_OR_GREATER
-////                    await using var stream = await file.OpenWriteAsync();
-////                    await using var reader = new System.IO.StreamWriter(stream);
-////#else
-////                    using var stream = await file.OpenWriteAsync();
-////                    using var reader = new System.IO.StreamWriter(stream);
-////#endif
-////                    await reader.WriteLineAsync(openedFileContent.Text);
-
-////                    lastSelectedDirectory = await file.GetParentAsync();
-////                }
-
-////                await SetPickerResult(file is null ? null : new [] {file});
-////            };
-////            this.Get<Button>("OpenFolderPicker").Click += async delegate
-////            {
-////                var folders = await GetStorageProvider().OpenFolderPickerAsync(new FolderPickerOpenOptions()
-////                {
-////                    Title = "Folder file",
-////                    SuggestedStartLocation = lastSelectedDirectory,
-////                    AllowMultiple = openMultiple.IsChecked == true
-////                });
-
-////                await SetPickerResult(folders);
-
-////                lastSelectedDirectory = folders.FirstOrDefault();
-////            };
-////            this.Get<Button>("OpenFileFromBookmark").Click += async delegate
-////            {
-////                var file = bookmarkContainer.Text is not null
-////                    ? await GetStorageProvider().OpenFileBookmarkAsync(bookmarkContainer.Text)
-////                    : null;
-
-////                await SetPickerResult(file is null ? null : new[] { file });
-////            };
-////            this.Get<Button>("OpenFolderFromBookmark").Click += async delegate
-////            {
-////                var folder = bookmarkContainer.Text is not null
-////                    ? await GetStorageProvider().OpenFolderBookmarkAsync(bookmarkContainer.Text)
-////                    : null;
-
-////                await SetPickerResult(folder is null ? null : new[] { folder });
-                
-////                lastSelectedDirectory = folder;
-////            };
-
-////            async Task SetPickerResult(IReadOnlyCollection<IStorageItem>? items)
-////            {
-////                items ??= Array.Empty<IStorageItem>();
-////                bookmarkContainer.Text = items.FirstOrDefault(f => f.CanBookmark) is { } f ? await f.SaveBookmarkAsync() : "Can't bookmark";
-////                var mappedResults = new List<string>();
-
-////                if (items.FirstOrDefault() is IStorageItem item)
-////                {
-////                    var resultText = item is IStorageFile ? "File:" : "Folder:";
-////                    resultText += Environment.NewLine;
-
-////                    var props = await item.GetBasicPropertiesAsync();
-////                    resultText += @$"Size: {props.Size}
-////DateCreated: {props.DateCreated}
-////DateModified: {props.DateModified}
-////CanBookmark: {item.CanBookmark}
-////";
-////                    if (item is IStorageFile file)
-////                    {
-////                        resultText += @$"
-////CanOpenRead: {file.CanOpenRead}
-////CanOpenWrite: {file.CanOpenWrite}
-////Content:
-////";
-////                        if (file.CanOpenRead)
-////                        {
-////#if NET6_0_OR_GREATER
-////                            await using var stream = await file.OpenReadAsync();
-////#else
-////                            using var stream = await file.OpenReadAsync();
-////#endif
-////                            using var reader = new System.IO.StreamReader(stream);
-
-////                            // 4GB file test, shouldn't load more than 10000 chars into a memory.
-////                            const int length = 10000;
-////                            var buffer = ArrayPool<char>.Shared.Rent(length);
-////                            try
-////                            {
-////                                var charsRead = await reader.ReadAsync(buffer, 0, length);
-////                                resultText += new string(buffer, 0, charsRead);
-////                            }
-////                            finally
-////                            {
-////                                ArrayPool<char>.Shared.Return(buffer);
-////                            }
-////                        }
-////                    }
-
-////                    openedFileContent.Text = resultText;
-
-////                    lastSelectedDirectory = await item.GetParentAsync();
-////                    if (lastSelectedDirectory is not null)
-////                    {
-////                        mappedResults.Add(FullPathOrName(lastSelectedDirectory));
-////                    }
-
-////                    foreach (var selectedItem in items)
-////                    {
-////                        mappedResults.Add("+> " + FullPathOrName(selectedItem));
-////                        if (selectedItem is IStorageFolder folder)
-////                        {
-////                            foreach (var innerItems in await folder.GetItemsAsync())
-////                            {
-////                                mappedResults.Add("++> " + FullPathOrName(innerItems));
-////                            }
-////                        }
-////                    }
-////                }
-
-////                results.Items = mappedResults;
-////                resultsVisible.IsVisible = mappedResults.Any();
-////            }
+            var results = this.Get<ItemsControl>("PickerLastResults");
+            var resultsVisible = this.Get<TextBlock>("PickerLastResultsVisible");
+            var bookmarkContainer = this.Get<TextBox>("BookmarkContainer");
+            var openedFileContent = this.Get<TextBox>("OpenedFileContent");
+            var openMultiple = this.Get<CheckBox>("OpenMultiple");
+
+            IStorageFolder? lastSelectedDirectory = null;
+
+            List<FileDialogFilter> GetFilters()
+            {
+                if (this.Get<CheckBox>("UseFilters").IsChecked != true)
+                    return new List<FileDialogFilter>();
+                return new List<FileDialogFilter>
+                            {
+                                new FileDialogFilter
+                                {
+                                    Name = "Text files (.txt)", Extensions = new List<string> {"txt"}
+                                },
+                                new FileDialogFilter
+                                {
+                                    Name = "All files",
+                                    Extensions = new List<string> {"*"}
+                                }
+                            };
+            }
+
+            List<FilePickerFileType>? GetFileTypes()
+            {
+                if (this.Get<CheckBox>("UseFilters").IsChecked != true)
+                    return null;
+                return new List<FilePickerFileType>
+                            {
+                                FilePickerFileTypes.All,
+                                FilePickerFileTypes.TextPlain
+                            };
+            }
+
+            this.Get<Button>("OpenFile").Click += async delegate
+            {
+                // Almost guaranteed to exist
+                var uri = Assembly.GetEntryAssembly()?.GetModules().FirstOrDefault()?.FullyQualifiedName;
+                var initialFileName = uri == null ? null : System.IO.Path.GetFileName(uri);
+                var initialDirectory = uri == null ? null : System.IO.Path.GetDirectoryName(uri);
+
+                var result = await new OpenFileDialog()
+                {
+                    Title = "Open file",
+                    Filters = GetFilters(),
+                    Directory = initialDirectory,
+                    InitialFileName = initialFileName
+                }.ShowAsync(GetWindow());
+                results.Items = result;
+                resultsVisible.IsVisible = result?.Any() == true;
+            };
+            this.Get<Button>("OpenMultipleFiles").Click += async delegate
+            {
+                var result = await new OpenFileDialog()
+                {
+                    Title = "Open multiple files",
+                    Filters = GetFilters(),
+                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
+                    AllowMultiple = true
+                }.ShowAsync(GetWindow());
+                results.Items = result;
+                resultsVisible.IsVisible = result?.Any() == true;
+            };
+            this.Get<Button>("SaveFile").Click += async delegate
+            {
+                var filters = GetFilters();
+                var result = await new SaveFileDialog()
+                {
+                    Title = "Save file",
+                    Filters = filters,
+                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
+                    DefaultExtension = filters?.Any() == true ? "txt" : null,
+                    InitialFileName = "test.txt"
+                }.ShowAsync(GetWindow());
+                results.Items = new[] { result };
+                resultsVisible.IsVisible = result != null;
+            };
+            this.Get<Button>("SelectFolder").Click += async delegate
+            {
+                var result = await new OpenFolderDialog()
+                {
+                    Title = "Select folder",
+                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null
+                }.ShowAsync(GetWindow());
+                if (string.IsNullOrEmpty(result))
+                {
+                    resultsVisible.IsVisible = false;
+                }
+                else
+                {
+                    lastSelectedDirectory = new BclStorageFolder(new System.IO.DirectoryInfo(result));
+                    results.Items = new[] { result };
+                    resultsVisible.IsVisible = true;
+                }
+            };
+            this.Get<Button>("OpenBoth").Click += async delegate
+            {
+                var result = await new OpenFileDialog()
+                {
+                    Title = "Select both",
+                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
+                    AllowMultiple = true
+                }.ShowManagedAsync(GetWindow(), new ManagedFileDialogOptions
+                {
+                    AllowDirectorySelection = true
+                });
+                results.Items = result;
+                resultsVisible.IsVisible = result?.Any() == true;
+            };
+            this.Get<Button>("DecoratedWindow").Click += delegate
+            {
+                new DecoratedWindow().Show();
+            };
+            this.Get<Button>("DecoratedWindowDialog").Click += delegate
+            {
+                _ = new DecoratedWindow().ShowDialog(GetWindow());
+            };
+            this.Get<Button>("Dialog").Click += delegate
+            {
+                var window = CreateSampleWindow();
+                window.Height = 200;
+                _ = window.ShowDialog(GetWindow());
+            };
+            this.Get<Button>("DialogNoTaskbar").Click += delegate
+            {
+                var window = CreateSampleWindow();
+                window.Height = 200;
+                window.ShowInTaskbar = false;
+                _ = window.ShowDialog(GetWindow());
+            };
+            this.Get<Button>("OwnedWindow").Click += delegate
+            {
+                var window = CreateSampleWindow();
+
+                window.Show(GetWindow());
+            };
+
+            this.Get<Button>("OwnedWindowNoTaskbar").Click += delegate
+            {
+                var window = CreateSampleWindow();
+
+                window.ShowInTaskbar = false;
+
+                window.Show(GetWindow());
+            };
+
+            this.Get<Button>("OpenFilePicker").Click += async delegate
+            {
+                var result = await GetStorageProvider().OpenFilePickerAsync(new FilePickerOpenOptions()
+                {
+                    Title = "Open file",
+                    FileTypeFilter = GetFileTypes(),
+                    SuggestedStartLocation = lastSelectedDirectory,
+                    AllowMultiple = openMultiple.IsChecked == true
+                });
+
+                await SetPickerResult(result);
+            };
+            this.Get<Button>("SaveFilePicker").Click += async delegate
+            {
+                var fileTypes = GetFileTypes();
+                var file = await GetStorageProvider().SaveFilePickerAsync(new FilePickerSaveOptions()
+                {
+                    Title = "Save file",
+                    FileTypeChoices = fileTypes,
+                    SuggestedStartLocation = lastSelectedDirectory,
+                    SuggestedFileName = "FileName",
+                    DefaultExtension = fileTypes?.Any() == true ? "txt" : null,
+                    ShowOverwritePrompt = false
+                });
+
+                if (file is not null && file.CanOpenWrite)
+                {
+                    // Sync disposal of StreamWriter is not supported on WASM
+#if NET6_0_OR_GREATER
+                    await using var stream = await file.OpenWriteAsync();
+                    await using var reader = new System.IO.StreamWriter(stream);
+#else
+                                using var stream = await file.OpenWriteAsync();
+                                using var reader = new System.IO.StreamWriter(stream);
+#endif
+                    await reader.WriteLineAsync(openedFileContent.Text);
+
+                    lastSelectedDirectory = await file.GetParentAsync();
+                }
+
+                await SetPickerResult(file is null ? null : new[] { file });
+            };
+            this.Get<Button>("OpenFolderPicker").Click += async delegate
+            {
+                var folders = await GetStorageProvider().OpenFolderPickerAsync(new FolderPickerOpenOptions()
+                {
+                    Title = "Folder file",
+                    SuggestedStartLocation = lastSelectedDirectory,
+                    AllowMultiple = openMultiple.IsChecked == true
+                });
+
+                await SetPickerResult(folders);
+
+                lastSelectedDirectory = folders.FirstOrDefault();
+            };
+            this.Get<Button>("OpenFileFromBookmark").Click += async delegate
+            {
+                var file = bookmarkContainer.Text is not null
+                    ? await GetStorageProvider().OpenFileBookmarkAsync(bookmarkContainer.Text)
+                    : null;
+
+                await SetPickerResult(file is null ? null : new[] { file });
+            };
+            this.Get<Button>("OpenFolderFromBookmark").Click += async delegate
+            {
+                var folder = bookmarkContainer.Text is not null
+                    ? await GetStorageProvider().OpenFolderBookmarkAsync(bookmarkContainer.Text)
+                    : null;
+
+                await SetPickerResult(folder is null ? null : new[] { folder });
+
+                lastSelectedDirectory = folder;
+            };
+
+            async Task SetPickerResult(IReadOnlyCollection<IStorageItem>? items)
+            {
+                items ??= Array.Empty<IStorageItem>();
+                bookmarkContainer.Text = items.FirstOrDefault(f => f.CanBookmark) is { } f ? await f.SaveBookmarkAsync() : "Can't bookmark";
+                var mappedResults = new List<string>();
+
+                if (items.FirstOrDefault() is IStorageItem item)
+                {
+                    var resultText = item is IStorageFile ? "File:" : "Folder:";
+                    resultText += Environment.NewLine;
+
+                    var props = await item.GetBasicPropertiesAsync();
+                    resultText += @$"Size: {props.Size}
+            DateCreated: {props.DateCreated}
+            DateModified: {props.DateModified}
+            CanBookmark: {item.CanBookmark}
+            ";
+                    if (item is IStorageFile file)
+                    {
+                        resultText += @$"
+            CanOpenRead: {file.CanOpenRead}
+            CanOpenWrite: {file.CanOpenWrite}
+            Content:
+            ";
+                        if (file.CanOpenRead)
+                        {
+#if NET6_0_OR_GREATER
+                            await using var stream = await file.OpenReadAsync();
+#else
+                                        using var stream = await file.OpenReadAsync();
+#endif
+                            using var reader = new System.IO.StreamReader(stream);
+
+                            // 4GB file test, shouldn't load more than 10000 chars into a memory.
+                            const int length = 10000;
+                            var buffer = ArrayPool<char>.Shared.Rent(length);
+                            try
+                            {
+                                var charsRead = await reader.ReadAsync(buffer, 0, length);
+                                resultText += new string(buffer, 0, charsRead);
+                            }
+                            finally
+                            {
+                                ArrayPool<char>.Shared.Return(buffer);
+                            }
+                        }
+                    }
+
+                    openedFileContent.Text = resultText;
+
+                    lastSelectedDirectory = await item.GetParentAsync();
+                    if (lastSelectedDirectory is not null)
+                    {
+                        mappedResults.Add(FullPathOrName(lastSelectedDirectory));
+                    }
+
+                    foreach (var selectedItem in items)
+                    {
+                        mappedResults.Add("+> " + FullPathOrName(selectedItem));
+                        if (selectedItem is IStorageFolder folder)
+                        {
+                            foreach (var innerItems in await folder.GetItemsAsync())
+                            {
+                                mappedResults.Add("++> " + FullPathOrName(innerItems));
+                            }
+                        }
+                    }
+                }
+
+                results.Items = mappedResults;
+                resultsVisible.IsVisible = mappedResults.Any();
+            }
         }
 
         protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)

From 56db1dbd61ea0af9624b2d30210c2204a82f8a6c Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sun, 4 Dec 2022 16:39:51 +0100
Subject: [PATCH 28/64] Remove unneeded change handler.

---
 src/Avalonia.Controls/ItemsControl.cs | 14 --------------
 1 file changed, 14 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 645abf50b30..6bbc6086442 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -92,7 +92,6 @@ public IBinding? DisplayMemberBinding
         static ItemsControl()
         {
             ItemsProperty.Changed.AddClassHandler<ItemsControl>((x, e) => x.ItemsChanged(e));
-            ItemTemplateProperty.Changed.AddClassHandler<ItemsControl>((x, e) => x.ItemTemplateChanged(e));
         }
 
         /// <summary>
@@ -647,19 +646,6 @@ private void SubscribeToItems(IEnumerable? items)
             return _displayMemberItemTemplate;
         }
 
-        /// <summary>
-        /// Called when the <see cref="ItemTemplate"/> changes.
-        /// </summary>
-        /// <param name="e">The event args.</param>
-        private void ItemTemplateChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            if (_itemContainerGenerator != null)
-            {
-                ////_itemContainerGenerator.ItemTemplate = (IDataTemplate?)e.NewValue;
-                // TODO: Rebuild the item containers.
-            }
-        }
-
         private void UpdateItemCount()
         {
             if (Items == null)

From c99307c6fa99f6930e55285f3ec20af947f9e961 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 7 Dec 2022 09:41:31 +0100
Subject: [PATCH 29/64] Use more consistent naming.

---
 src/Avalonia.Controls/Generators/ItemContainerGenerator.cs | 2 +-
 src/Avalonia.Controls/ItemsControl.cs                      | 2 +-
 src/Avalonia.Controls/ListBox.cs                           | 2 +-
 src/Avalonia.Controls/TabControl.cs                        | 2 +-
 src/Avalonia.Controls/TreeView.cs                          | 2 +-
 src/Avalonia.Controls/TreeViewItem.cs                      | 2 +-
 tests/Avalonia.Controls.UnitTests/TreeViewTests.cs         | 2 +-
 7 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
index 1cf40d335fa..fe8dda3b98d 100644
--- a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
+++ b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
@@ -27,7 +27,7 @@ public class ItemContainerGenerator
         /// calling this method, <see cref="PrepareItemContainer(Control, object, int)"/> should
         /// be called to prepare the container to display the specified item.
         /// </remarks>
-        public Control CreateContainer() => _owner.CreateContainerOverride();
+        public Control CreateContainer() => _owner.CreateContainerForItemOverride();
 
         /// <summary>
         /// Determines whether the specified item is (or is eligible to be) its own container.
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 6bbc6086442..b512d3583c4 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -265,7 +265,7 @@ void ICollectionChangedListener.PostChanged(INotifyCollectionChanged sender, Not
         /// <summary>
         /// Creates or a container that can be used to display an item.
         /// </summary>
-        protected internal virtual Control CreateContainerOverride() => new ContentPresenter();
+        protected internal virtual Control CreateContainerForItemOverride() => new ContentPresenter();
 
         /// <summary>
         /// Prepares the specified element to display the specified item.
diff --git a/src/Avalonia.Controls/ListBox.cs b/src/Avalonia.Controls/ListBox.cs
index 78a2d5d9906..8b1a3071821 100644
--- a/src/Avalonia.Controls/ListBox.cs
+++ b/src/Avalonia.Controls/ListBox.cs
@@ -103,7 +103,7 @@ public IScrollable? Scroll
         /// </summary>
         public void UnselectAll() => Selection.Clear();
 
-        protected internal override Control CreateContainerOverride() => new ListBoxItem();
+        protected internal override Control CreateContainerForItemOverride() => new ListBoxItem();
 
         /// <inheritdoc/>
         protected override void OnGotFocus(GotFocusEventArgs e)
diff --git a/src/Avalonia.Controls/TabControl.cs b/src/Avalonia.Controls/TabControl.cs
index a6085e53cd6..33089344e8a 100644
--- a/src/Avalonia.Controls/TabControl.cs
+++ b/src/Avalonia.Controls/TabControl.cs
@@ -149,7 +149,7 @@ bool IContentPresenterHost.RegisterContentPresenter(IContentPresenter presenter)
             return RegisterContentPresenter(presenter);
         }
 
-        protected internal override Control CreateContainerOverride() => new TabItem();
+        protected internal override Control CreateContainerForItemOverride() => new TabItem();
         protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is TabItem;
 
         protected internal override void PrepareContainerForItemOverride(Control element, object? item, int index)
diff --git a/src/Avalonia.Controls/TreeView.cs b/src/Avalonia.Controls/TreeView.cs
index c3e891149a9..a1cf3cdb533 100644
--- a/src/Avalonia.Controls/TreeView.cs
+++ b/src/Avalonia.Controls/TreeView.cs
@@ -465,7 +465,7 @@ private void UnsubscribeFromSelectedItems()
             return (false, null);
         }
 
-        protected internal override Control CreateContainerOverride() => new TreeViewItem();
+        protected internal override Control CreateContainerForItemOverride() => new TreeViewItem();
         protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is TreeViewItem;
 
         /// <inheritdoc/>
diff --git a/src/Avalonia.Controls/TreeViewItem.cs b/src/Avalonia.Controls/TreeViewItem.cs
index 3ff34a14b1f..6081fef4e65 100644
--- a/src/Avalonia.Controls/TreeViewItem.cs
+++ b/src/Avalonia.Controls/TreeViewItem.cs
@@ -90,7 +90,7 @@ public int Level
 
         internal TreeView? TreeViewOwner => _treeView;
 
-        protected internal override Control CreateContainerOverride() => new TreeViewItem();
+        protected internal override Control CreateContainerForItemOverride() => new TreeViewItem();
         protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is TreeViewItem;
 
         /// <inheritdoc/>
diff --git a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
index b9a6566116c..bcf719d2bb0 100644
--- a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
@@ -1406,7 +1406,7 @@ private class DerivedTreeView : TreeView
 
         private class DerivedTreeViewWithDerivedTreeViewItems : TreeView
         {
-            protected internal override Control CreateContainerOverride() => new DerivedTreeViewItem();
+            protected internal override Control CreateContainerForItemOverride() => new DerivedTreeViewItem();
         }
 
         private class DerivedTreeViewItem : TreeViewItem

From be2da5cc21e6d45322408376bc1897f5dcfd3e4b Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 7 Dec 2022 09:50:44 +0100
Subject: [PATCH 30/64] Reimplemented commented-out code.

---
 src/Avalonia.Controls/TreeView.cs | 42 +++++++++----------------------
 1 file changed, 12 insertions(+), 30 deletions(-)

diff --git a/src/Avalonia.Controls/TreeView.cs b/src/Avalonia.Controls/TreeView.cs
index a1cf3cdb533..0c0de9d544c 100644
--- a/src/Avalonia.Controls/TreeView.cs
+++ b/src/Avalonia.Controls/TreeView.cs
@@ -468,6 +468,18 @@ private void UnsubscribeFromSelectedItems()
         protected internal override Control CreateContainerForItemOverride() => new TreeViewItem();
         protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is TreeViewItem;
 
+        protected internal override void PrepareContainerForItemOverride(Control container, object? item, int index)
+        {
+            base.PrepareContainerForItemOverride(container, item, index);
+
+            if (item == SelectedItem)
+            {
+                MarkContainerSelected(container, true);
+                if (AutoScrollToSelectedItem)
+                    Dispatcher.UIThread.Post(container.BringIntoView);
+            }
+        }
+
         /// <inheritdoc/>
         protected override void OnGotFocus(GotFocusEventArgs e)
         {
@@ -831,36 +843,6 @@ protected bool UpdateSelectionFromEventSource(
             return item?.TreeViewOwner == this ? item : null;
         }
 
-        /// <summary>
-        /// Called when a new item container is materialized, to set its selected state.
-        /// </summary>
-        /// <param name="sender">The event sender.</param>
-        /// <param name="e">The event args.</param>
-        ////private void ContainerMaterialized(object? sender, ItemContainerEventArgs e)
-        ////{
-        ////    var selectedItem = SelectedItem;
-
-        ////    if (selectedItem == null)
-        ////    {
-        ////        return;
-        ////    }
-
-        ////    foreach (var container in e.Containers)
-        ////    {
-        ////        if (container.Item == selectedItem)
-        ////        {
-        ////            ((TreeViewItem)container.ContainerControl).IsSelected = true;
-
-        ////            if (AutoScrollToSelectedItem)
-        ////            {
-        ////                Dispatcher.UIThread.Post(container.ContainerControl.BringIntoView);
-        ////            }
-
-        ////            break;
-        ////        }
-        ////    }
-        ////}
-
         /// <summary>
         /// Sets a container's 'selected' class or <see cref="ISelectable.IsSelected"/>.
         /// </summary>

From e7f3b23725354a8f4c43b317976888e922fd93af Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 7 Dec 2022 11:13:22 +0100
Subject: [PATCH 31/64] Implement ILogicalScrollable on ItemsPresenter.

---
 .../Presenters/ItemsPresenter.cs              | 68 ++++++++++++++++++-
 1 file changed, 65 insertions(+), 3 deletions(-)

diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
index 0091bbd48d0..8297922664d 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
@@ -1,8 +1,7 @@
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Reflection;
+using Avalonia.Controls.Primitives;
 using Avalonia.Input;
 
 namespace Avalonia.Controls.Presenters
@@ -10,7 +9,7 @@ namespace Avalonia.Controls.Presenters
     /// <summary>
     /// Presents items inside an <see cref="Avalonia.Controls.ItemsControl"/>.
     /// </summary>
-    public class ItemsPresenter : Control
+    public class ItemsPresenter : Control, ILogicalScrollable
     {
         /// <summary>
         /// Defines the <see cref="ItemsPanel"/> property.
@@ -19,6 +18,8 @@ public class ItemsPresenter : Control
             ItemsControl.ItemsPanelProperty.AddOwner<ItemsPresenter>();
 
         private PanelContainerGenerator? _generator;
+        private ILogicalScrollable? _logicalScrollable;
+        private EventHandler? _scrollInvalidated;
 
         static ItemsPresenter()
         {
@@ -27,6 +28,12 @@ static ItemsPresenter()
                 KeyboardNavigationMode.Once);
         }
 
+        event EventHandler? ILogicalScrollable.ScrollInvalidated
+        {
+            add => _scrollInvalidated += value;
+            remove => _scrollInvalidated -= value;
+        }
+
         /// <summary>
         /// Gets or sets a template which creates the <see cref="Panel"/> used to display the items.
         /// </summary>
@@ -45,11 +52,52 @@ public ITemplate<Panel> ItemsPanel
         /// Gets the owner <see cref="ItemsControl"/>.
         /// </summary>
         internal ItemsControl? ItemsControl { get; private set; }
+        
+        bool ILogicalScrollable.CanHorizontallyScroll 
+        {
+            get => _logicalScrollable?.CanHorizontallyScroll ?? false;
+            set
+            {
+                if (_logicalScrollable is not null)
+                    _logicalScrollable.CanHorizontallyScroll = value;
+            }
+        }
+
+        bool ILogicalScrollable.CanVerticallyScroll 
+        {
+            get => _logicalScrollable?.CanVerticallyScroll ?? false;
+            set
+            {
+                if (_logicalScrollable is not null)
+                    _logicalScrollable.CanVerticallyScroll = value;
+            }
+        }
+
+        Vector IScrollable.Offset 
+        {
+            get => _logicalScrollable?.Offset ?? default;
+            set
+            {
+                if (_logicalScrollable is not null)
+                    _logicalScrollable.Offset = value;
+            }
+        }
+
+        bool ILogicalScrollable.IsLogicalScrollEnabled => _logicalScrollable?.IsLogicalScrollEnabled ?? false;
+        Size ILogicalScrollable.ScrollSize => _logicalScrollable?.ScrollSize ?? default;
+        Size ILogicalScrollable.PageScrollSize => _logicalScrollable?.PageScrollSize ?? default;
+        Size IScrollable.Extent => _logicalScrollable?.Extent ?? default;
+        Size IScrollable.Viewport => _logicalScrollable?.Viewport ?? default;
 
         public override sealed void ApplyTemplate()
         {
             if (Panel is null && ItemsControl is not null)
             {
+                if (_logicalScrollable is not null)
+                {
+                    _logicalScrollable.ScrollInvalidated -= OnLogicalScrollInvalidated;
+                }
+
                 Panel = ItemsPanel.Build();
                 Panel.SetValue(TemplatedParentProperty, TemplatedParent);
                 LogicalChildren.Add(Panel);
@@ -59,9 +107,22 @@ public override sealed void ApplyTemplate()
                     v.Attach(ItemsControl);
                 else
                     CreateSimplePanelGenerator();
+
+                _logicalScrollable = Panel as ILogicalScrollable;
+
+                if (_logicalScrollable is not null)
+                {
+                    _logicalScrollable.ScrollInvalidated += OnLogicalScrollInvalidated;
+                }
             }
         }
 
+        bool ILogicalScrollable.BringIntoView(Control target, Rect targetRect) =>
+            _logicalScrollable?.BringIntoView(target, targetRect) ?? false;
+        Control? ILogicalScrollable.GetControlInDirection(NavigationDirection direction, Control? from) =>
+            _logicalScrollable?.GetControlInDirection(direction, from);
+        void ILogicalScrollable.RaiseScrollInvalidated(EventArgs e) => _scrollInvalidated?.Invoke(this, e);
+
         internal void ScrollIntoView(int index)
         {
             if (Panel is VirtualizingPanel v)
@@ -142,5 +203,6 @@ internal int IndexFromContainer(Control container)
             return Panel?.Children.IndexOf(container) ?? -1;
         }
 
+        private void OnLogicalScrollInvalidated(object? sender, EventArgs e) => _scrollInvalidated?.Invoke(this, e);
     }
 }

From 08f90dcad6d1064030ebbc21182a2447f5bf8537 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 7 Dec 2022 12:39:44 +0100
Subject: [PATCH 32/64] Make logic a bit clearer.

---
 .../VirtualizingStackPanel.cs                 | 27 ++++++++++++-------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index f211ec2edbc..22526fa29c1 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -428,7 +428,8 @@ private void GenerateElements(Size availableSize, ref MeasureViewport viewport)
 
         private Control GetOrCreateElement(IList items, int index)
         {
-            var e = GetRealizedElement(index) ?? 
+            var e = GetRealizedElement(index) ??
+                GetItemIsOwnContainer(items, index) ??
                 GetRecycledElement(items, index) ??
                 CreateElement(items, index);
             InvalidateHack(e);
@@ -442,15 +443,12 @@ private Control GetOrCreateElement(IList items, int index)
             return _realizedElements?.GetElement(index);
         }
 
-        private Control? GetRecycledElement(IList items, int index)
+        private Control? GetItemIsOwnContainer(IList items, int index)
         {
-            Debug.Assert(ItemsControl is not null);
-
-            var generator = ItemsControl!.ItemContainerGenerator;
-            var item = items[index];
-
-            if (item is Control controlItem)
+            if (items[index] is Control controlItem)
             {
+                var generator = ItemsControl!.ItemContainerGenerator;
+
                 if (controlItem.IsSet(ItemIsOwnContainerProperty))
                 {
                     controlItem.IsVisible = true;
@@ -459,12 +457,23 @@ private Control GetOrCreateElement(IList items, int index)
                 else if (generator.IsItemItsOwnContainer(controlItem))
                 {
                     AddInternalChild(controlItem);
-                    generator.PrepareItemContainer(controlItem, item, index);
+                    generator.PrepareItemContainer(controlItem, controlItem, index);
                     controlItem.SetValue(ItemIsOwnContainerProperty, true);
                     return controlItem;
                 }
             }
 
+            return null;
+        }
+
+        private Control? GetRecycledElement(IList items, int index)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            var generator = ItemsControl!.ItemContainerGenerator;
+            var item = items[index];
+
+
             if (_recyclePool?.Count > 0)
             {
                 var recycled = _recyclePool.Pop();

From f0c89a614e1c79bb0e68026f20f931c2fd314091 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 09:49:57 +0100
Subject: [PATCH 33/64] Reimplemented Carousel.

Only `VirtualizingCarouselPanel` currently implemented.
---
 .../ControlCatalog/Pages/CarouselPage.xaml    |   4 +-
 src/Avalonia.Controls/Carousel.cs             |  50 +-
 .../Presenters/CarouselPresenter.cs           | 276 -------
 .../VirtualizingCarouselPanel.cs              | 351 +++++++++
 .../Controls/Carousel.xaml                    |  20 +-
 .../Controls/Carousel.xaml                    |  23 +-
 .../CarouselTests.cs                          | 652 ++++++++--------
 .../Presenters/CarouselPresenterTests.cs      | 732 ------------------
 .../VirtualizingCarouselPanelTests.cs         | 271 +++++++
 .../UnitTestSynchronizationContext.cs         |   5 +-
 10 files changed, 993 insertions(+), 1391 deletions(-)
 delete mode 100644 src/Avalonia.Controls/Presenters/CarouselPresenter.cs
 create mode 100644 src/Avalonia.Controls/VirtualizingCarouselPanel.cs
 delete mode 100644 tests/Avalonia.Controls.UnitTests/Presenters/CarouselPresenterTests.cs
 create mode 100644 tests/Avalonia.Controls.UnitTests/VirtualizingCarouselPanelTests.cs
 rename tests/{Avalonia.Base.UnitTests/Data => Avalonia.UnitTests}/UnitTestSynchronizationContext.cs (91%)

diff --git a/samples/ControlCatalog/Pages/CarouselPage.xaml b/samples/ControlCatalog/Pages/CarouselPage.xaml
index 1c2d7689669..352fa32e30e 100644
--- a/samples/ControlCatalog/Pages/CarouselPage.xaml
+++ b/samples/ControlCatalog/Pages/CarouselPage.xaml
@@ -12,7 +12,7 @@
       </Button>
       <Carousel Name="carousel" Grid.Column="1">
         <Carousel.PageTransition>
-          <PageSlide Duration="0.25" Orientation="Vertical" />
+          <PageSlide Duration="0.25" Orientation="Horizontal" />
         </Carousel.PageTransition>
         <Image Source="/Assets/delicate-arch-896885_640.jpg"/>
         <Image Source="/Assets/hirsch-899118_640.jpg"/>
@@ -35,7 +35,7 @@
 
     <StackPanel Orientation="Horizontal" Spacing="4">
       <TextBlock VerticalAlignment="Center">Orientation</TextBlock>
-      <ComboBox Name="orientation" SelectedIndex="1" VerticalAlignment="Center">
+      <ComboBox Name="orientation" SelectedIndex="0" VerticalAlignment="Center">
         <ComboBoxItem>Horizontal</ComboBoxItem>
         <ComboBoxItem>Vertical</ComboBoxItem>
       </ComboBox>
diff --git a/src/Avalonia.Controls/Carousel.cs b/src/Avalonia.Controls/Carousel.cs
index 572ec5a3d5a..a9ffb2119a4 100644
--- a/src/Avalonia.Controls/Carousel.cs
+++ b/src/Avalonia.Controls/Carousel.cs
@@ -2,7 +2,6 @@
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Templates;
 using Avalonia.Controls.Utils;
-using Avalonia.Input;
 
 namespace Avalonia.Controls
 {
@@ -11,12 +10,6 @@ namespace Avalonia.Controls
     /// </summary>
     public class Carousel : SelectingItemsControl
     {
-        /// <summary>
-        /// Defines the <see cref="IsVirtualized"/> property.
-        /// </summary>
-        public static readonly StyledProperty<bool> IsVirtualizedProperty =
-            AvaloniaProperty.Register<Carousel, bool>(nameof(IsVirtualized), true);
-
         /// <summary>
         /// Defines the <see cref="PageTransition"/> property.
         /// </summary>
@@ -28,7 +21,9 @@ public class Carousel : SelectingItemsControl
         /// <see cref="Carousel"/>.
         /// </summary>
         private static readonly ITemplate<Panel> PanelTemplate =
-            new FuncTemplate<Panel>(() => new Panel());
+            new FuncTemplate<Panel>(() => new VirtualizingCarouselPanel());
+
+        private IScrollable? _scroller;
 
         /// <summary>
         /// Initializes static members of the <see cref="Carousel"/> class.
@@ -38,18 +33,6 @@ static Carousel()
             SelectionModeProperty.OverrideDefaultValue<Carousel>(SelectionMode.AlwaysSelected);
             ItemsPanelProperty.OverrideDefaultValue<Carousel>(PanelTemplate);
         }
-        
-        /// <summary>
-        /// Gets or sets a value indicating whether the items in the carousel are virtualized.
-        /// </summary>
-        /// <remarks>
-        /// When the carousel is virtualized, only the active page is held in memory.
-        /// </remarks>
-        public bool IsVirtualized
-        {
-            get { return GetValue(IsVirtualizedProperty); }
-            set { SetValue(IsVirtualizedProperty, value); }
-        }
 
         /// <summary>
         /// Gets or sets the transition to use when moving between pages.
@@ -81,5 +64,32 @@ public void Previous()
                 --SelectedIndex;
             }
         }
+
+        protected override Size ArrangeOverride(Size finalSize)
+        {
+            var result = base.ArrangeOverride(finalSize);
+
+            if (_scroller is not null)
+                _scroller.Offset = new(SelectedIndex, 0);
+
+            return result;
+        }
+
+        protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
+        {
+            base.OnApplyTemplate(e);
+            _scroller = e.NameScope.Find<IScrollable>("PART_ScrollViewer");
+        }
+
+        protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
+        {
+            base.OnPropertyChanged(change);
+
+            if (change.Property == SelectedIndexProperty && _scroller is not null)
+            {
+                var value = change.GetNewValue<int>();
+                _scroller.Offset = new(value, 0);
+            }
+        }
     }
 }
diff --git a/src/Avalonia.Controls/Presenters/CarouselPresenter.cs b/src/Avalonia.Controls/Presenters/CarouselPresenter.cs
deleted file mode 100644
index d5b89a1bdc1..00000000000
--- a/src/Avalonia.Controls/Presenters/CarouselPresenter.cs
+++ /dev/null
@@ -1,276 +0,0 @@
-using System.Collections.Specialized;
-using System.Linq;
-using System.Reactive.Linq;
-using System.Threading.Tasks;
-using Avalonia.Animation;
-using Avalonia.Controls.Primitives;
-using Avalonia.Controls.Utils;
-using Avalonia.Data;
-
-namespace Avalonia.Controls.Presenters
-{
-    /// <summary>
-    /// Displays pages inside an <see cref="ItemsControl"/>.
-    /// </summary>
-    public class CarouselPresenter : ItemsPresenter
-    {
-        /// <summary>
-        /// Defines the <see cref="IsVirtualized"/> property.
-        /// </summary>
-        public static readonly StyledProperty<bool> IsVirtualizedProperty =
-            Carousel.IsVirtualizedProperty.AddOwner<CarouselPresenter>();
-
-        /// <summary>
-        /// Defines the <see cref="SelectedIndex"/> property.
-        /// </summary>
-        public static readonly DirectProperty<CarouselPresenter, int> SelectedIndexProperty =
-            SelectingItemsControl.SelectedIndexProperty.AddOwner<CarouselPresenter>(
-                o => o.SelectedIndex,
-                (o, v) => o.SelectedIndex = v);
-
-        /// <summary>
-        /// Defines the <see cref="PageTransition"/> property.
-        /// </summary>
-        public static readonly StyledProperty<IPageTransition?> PageTransitionProperty =
-            Carousel.PageTransitionProperty.AddOwner<CarouselPresenter>();
-
-        private int _selectedIndex = -1;
-        private Task? _currentTransition;
-        private int _queuedTransitionIndex = -1;
-
-        /// <summary>
-        /// Initializes static members of the <see cref="CarouselPresenter"/> class.
-        /// </summary>
-        static CarouselPresenter()
-        {
-            ////IsVirtualizedProperty.Changed.AddClassHandler<CarouselPresenter>((x, e) => x.IsVirtualizedChanged(e));
-            ////SelectedIndexProperty.Changed.AddClassHandler<CarouselPresenter>((x, e) => x.SelectedIndexChanged(e));
-        }
-
-        /// <summary>
-        /// Gets or sets a value indicating whether the items in the carousel are virtualized.
-        /// </summary>
-        /// <remarks>
-        /// When the carousel is virtualized, only the active page is held in memory.
-        /// </remarks>
-        public bool IsVirtualized
-        {
-            get { return GetValue(IsVirtualizedProperty); }
-            set { SetValue(IsVirtualizedProperty, value); }
-        }
-
-        /// <summary>
-        /// Gets or sets the index of the selected page.
-        /// </summary>
-        public int SelectedIndex
-        {
-            get
-            {
-                return _selectedIndex;
-            }
-
-            set
-            {
-                ////var old = SelectedIndex;
-                ////var effective = (value >= 0 && value < Items?.Cast<object>().Count()) ? value : -1;
-
-                ////if (old != effective)
-                ////{
-                ////    _selectedIndex = effective;
-                ////    RaisePropertyChanged(SelectedIndexProperty, old, effective, BindingPriority.LocalValue);
-                ////}
-            }
-        }
-
-        /// <summary>
-        /// Gets or sets a transition to use when switching pages.
-        /// </summary>
-        public IPageTransition? PageTransition
-        {
-            get { return GetValue(PageTransitionProperty); }
-            set { SetValue(PageTransitionProperty, value); }
-        }
-
-        /// <inheritdoc/>
-        ////protected override void ItemsChanged(NotifyCollectionChangedEventArgs e)
-        ////{
-        ////    if (!IsVirtualized)
-        ////    {
-        ////        base.ItemsChanged(e);
-
-        ////        if (Items == null || SelectedIndex >= Items.Count())
-        ////        {
-        ////            SelectedIndex = Items.Count() - 1;
-        ////        }
-
-        ////        foreach (var c in ItemContainerGenerator.Containers)
-        ////        {
-        ////            c.ContainerControl.IsVisible = c.Index == SelectedIndex;
-        ////        }
-        ////    }
-        ////    else if (SelectedIndex != -1 && Panel != null)
-        ////    {
-        ////        switch (e.Action)
-        ////        {
-        ////            case NotifyCollectionChangedAction.Add:
-        ////                if (e.NewStartingIndex > SelectedIndex)
-        ////                {
-        ////                    return;
-        ////                }
-        ////                break;
-        ////            case NotifyCollectionChangedAction.Remove:
-        ////                if (e.OldStartingIndex > SelectedIndex)
-        ////                {
-        ////                    return;
-        ////                }
-        ////                break;
-        ////            case NotifyCollectionChangedAction.Replace:
-        ////                if (e.OldStartingIndex > SelectedIndex ||
-        ////                    e.OldStartingIndex + e.OldItems!.Count - 1 < SelectedIndex)
-        ////                {
-        ////                    return;
-        ////                }
-        ////                break;
-        ////            case NotifyCollectionChangedAction.Move:
-        ////                if (e.OldStartingIndex > SelectedIndex &&
-        ////                    e.NewStartingIndex > SelectedIndex)
-        ////                {
-        ////                    return;
-        ////                }
-        ////                break;
-        ////        }
-
-        ////        if (Items == null || SelectedIndex >= Items.Count())
-        ////        {
-        ////            SelectedIndex = Items.Count() - 1;
-        ////        }
-
-        ////        Panel.Children.Clear();
-        ////        ItemContainerGenerator.Clear();
-
-        ////        if (SelectedIndex != -1)
-        ////        {
-        ////            GetOrCreateContainer(SelectedIndex);
-        ////        }
-        ////    }
-        ////}
-
-        ////protected override void PanelCreated(Panel panel)
-        ////{
-        ////    ItemsChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
-        ////}
-
-        /////// <summary>
-        /////// Moves to the selected page, animating if a <see cref="PageTransition"/> is set.
-        /////// </summary>
-        /////// <param name="fromIndex">The index of the old page.</param>
-        /////// <param name="toIndex">The index of the new page.</param>
-        /////// <returns>A task tracking the animation.</returns>
-        ////private async Task MoveToPage(int fromIndex, int toIndex)
-        ////{
-        ////    if (fromIndex != toIndex)
-        ////    {
-        ////        var generator = ItemContainerGenerator;
-        ////        Control? from = null;
-        ////        Control? to = null;
-
-        ////        if (fromIndex != -1)
-        ////        {
-        ////            from = generator.ContainerFromIndex(fromIndex);
-        ////        }
-
-        ////        if (toIndex != -1)
-        ////        {
-        ////            to = GetOrCreateContainer(toIndex);
-        ////        }
-
-        ////        if (PageTransition != null && (from != null || to != null))
-        ////        {
-        ////            await PageTransition.Start((Visual?)from, (Visual?)to, fromIndex < toIndex, default);
-        ////        }
-        ////        else if (to != null)
-        ////        {
-        ////            to.IsVisible = true;
-        ////        }
-
-        ////        if (from != null)
-        ////        {
-        ////            if (IsVirtualized)
-        ////            {
-        ////                Panel!.Children.Remove(from);
-        ////                generator.Dematerialize(fromIndex, 1);
-        ////            }
-        ////            else
-        ////            {
-        ////                from.IsVisible = false;
-        ////            }
-        ////        }
-        ////    }
-        ////}
-
-        ////private Control? GetOrCreateContainer(int index)
-        ////{
-        ////    var container = ItemContainerGenerator.ContainerFromIndex(index);
-
-        ////    if (container == null && IsVirtualized)
-        ////    {
-        ////        var item = Items!.Cast<object>().ElementAt(index);
-        ////        var materialized = ItemContainerGenerator.Materialize(index, item);
-        ////        Panel!.Children.Add(materialized.ContainerControl);
-        ////        container = materialized.ContainerControl;
-        ////    }
-
-        ////    return container;
-        ////}
-
-        /////// <summary>
-        /////// Called when the <see cref="IsVirtualized"/> property changes.
-        /////// </summary>
-        /////// <param name="e">The event args.</param>
-        ////private void IsVirtualizedChanged(AvaloniaPropertyChangedEventArgs e)
-        ////{
-        ////    if (Panel != null)
-        ////    {
-        ////        ItemsChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
-        ////    }
-        ////}
-
-        /////// <summary>
-        /////// Called when the <see cref="SelectedIndex"/> property changes.
-        /////// </summary>
-        /////// <param name="e">The event args.</param>
-        ////private async void SelectedIndexChanged(AvaloniaPropertyChangedEventArgs e)
-        ////{
-        ////    if (Panel != null)
-        ////    {
-        ////        if (_currentTransition == null)
-        ////        {
-        ////            int fromIndex = (int)e.OldValue!;
-        ////            int toIndex = (int)e.NewValue!;
-
-        ////            for (;;)
-        ////            {
-        ////                _currentTransition = MoveToPage(fromIndex, toIndex);
-        ////                await _currentTransition;
-
-        ////                if (_queuedTransitionIndex != -1)
-        ////                {
-        ////                    fromIndex = toIndex;
-        ////                    toIndex = _queuedTransitionIndex;
-        ////                    _queuedTransitionIndex = -1;
-        ////                }
-        ////                else
-        ////                {
-        ////                    _currentTransition = null;
-        ////                    break;
-        ////                }
-        ////            }
-        ////        }
-        ////        else
-        ////        {
-        ////            _queuedTransitionIndex = (int)e.NewValue!;
-        ////        }
-        ////    }
-        ////}
-    }
-}
diff --git a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
new file mode 100644
index 00000000000..7ea175fc184
--- /dev/null
+++ b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
@@ -0,0 +1,351 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Specialized;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+using Avalonia.Animation;
+using Avalonia.Controls.Primitives;
+using Avalonia.Input;
+
+namespace Avalonia.Controls
+{
+    /// <summary>
+    /// A panel used by <see cref="Carousel"/> to display the current item.
+    /// </summary>
+    public class VirtualizingCarouselPanel : VirtualizingPanel, ILogicalScrollable
+    {
+        private static readonly AttachedProperty<bool> ItemIsOwnContainerProperty =
+            AvaloniaProperty.RegisterAttached<VirtualizingCarouselPanel, Control, bool>("ItemIsOwnContainer");
+
+        private Size _extent;
+        private Vector _offset;
+        private Size _viewport;
+        private Stack<Control>? _recyclePool;
+        private Control? _realized;
+        private int _realizedIndex = -1;
+        private Control? _transitionFrom;
+        private int _transitionFromIndex = -1;
+        private CancellationTokenSource? _transition;
+        private EventHandler? _scrollInvalidated;
+
+        bool ILogicalScrollable.CanHorizontallyScroll { get; set; }
+        bool ILogicalScrollable.CanVerticallyScroll { get; set; }
+        bool ILogicalScrollable.IsLogicalScrollEnabled => true;
+        Size ILogicalScrollable.ScrollSize => new(1, 1);
+        Size ILogicalScrollable.PageScrollSize => new(1, 1);
+        Size IScrollable.Extent => Extent;
+        Size IScrollable.Viewport => Viewport;
+
+        Vector IScrollable.Offset 
+        {
+            get => _offset;
+            set
+            {
+                if ((int)_offset.X != value.X)
+                    InvalidateMeasure();
+                _offset = value;
+            }
+        }
+
+        private Size Extent
+        {
+            get => _extent;
+            set
+            {
+                if (_extent != value)
+                {
+                    _extent = value;
+                    _scrollInvalidated?.Invoke(this, EventArgs.Empty);
+                }
+            }
+        }
+
+        private Size Viewport
+        {
+            get => _viewport;
+            set
+            {
+                if (_viewport != value)
+                {
+                    _viewport = value;
+                    _scrollInvalidated?.Invoke(this, EventArgs.Empty);
+                }
+            }
+        }
+
+        event EventHandler? ILogicalScrollable.ScrollInvalidated
+        {
+            add => _scrollInvalidated += value;
+            remove => _scrollInvalidated -= value;
+        }
+
+        bool ILogicalScrollable.BringIntoView(Control target, Rect targetRect)
+        {
+            throw new NotImplementedException();
+        }
+
+        Control? ILogicalScrollable.GetControlInDirection(NavigationDirection direction, Control? from)
+        {
+            throw new NotImplementedException();
+        }
+
+        void ILogicalScrollable.RaiseScrollInvalidated(EventArgs e) => _scrollInvalidated?.Invoke(this, e);
+
+        protected override Size MeasureOverride(Size availableSize)
+        {
+            var items = ItemsControl?.Items as IList ?? Array.Empty<object?>();
+            var index = (int)_offset.X;
+
+            if (index != _realizedIndex)
+            {
+                if (_realized is not null)
+                {
+                    var cancelTransition = _transition is not null;
+
+                    // Cancel any already running transition, and recycle the element we're transitioning from.
+                    if (cancelTransition)
+                    {
+                        _transition!.Cancel();
+                        _transition = null;
+                        if (_transitionFrom is not null)
+                            RecycleElement(_transitionFrom);
+                        _transitionFrom = null;
+                        _transitionFromIndex = -1;
+                    }
+
+                    if (cancelTransition || GetTransition() is null)
+                    {
+                        // If don't have a transition or we've just canceled a transition then recycle the element
+                        // we're moving from.
+                        RecycleElement(_realized);
+                    }
+                    else
+                    {
+                        // We have a transition to do: record the current element as the element we're transitioning
+                        // from and we'll start the transition in the arrange pass.
+                        _transitionFrom = _realized;
+                        _transitionFromIndex = _realizedIndex;
+                    }
+
+                    _realized = null;
+                    _realizedIndex = -1;
+                }
+                
+                // Get or create an element for the new item.
+                if (index >= 0 && index < items.Count)
+                {
+                    _realized = GetOrCreateElement(items, index);
+                    _realizedIndex = index;
+                }
+            }
+
+            if (_realized is null)
+            {
+                Extent = Viewport = new(0, 0);
+                _transitionFrom = null;
+                _transitionFromIndex = -1;
+                return default;
+            }
+
+            _realized.Measure(availableSize);
+            Extent = new(items.Count, 1);
+            Viewport = new(1, 1);
+
+            return _realized.DesiredSize;
+        }
+
+        protected override Size ArrangeOverride(Size finalSize)
+        {
+            var result = base.ArrangeOverride(finalSize);
+
+            if (_transition is null &&
+                _transitionFrom is not null &&
+                _realized is { } to &&
+                GetTransition() is { } transition)
+            {
+                _transition = new CancellationTokenSource();
+                transition.Start(_transitionFrom, to, _realizedIndex > _transitionFromIndex, _transition.Token)
+                    .ContinueWith(TransitionFinished, TaskScheduler.FromCurrentSynchronizationContext());
+            }
+
+            return result;
+        }
+
+        protected override IInputElement? GetControl(NavigationDirection direction, IInputElement? from, bool wrap) => null;
+
+        protected internal override Control? ContainerFromIndex(int index)
+        {
+            return index == _realizedIndex ? _realized : null;
+        }
+
+        protected internal override IEnumerable<Control>? GetRealizedContainers()
+        {
+            return _realized is not null ? new[] { _realized } : null;
+        }
+
+        protected internal override int IndexFromContainer(Control container)
+        {
+            return container == _realized ? _realizedIndex : -1;
+        }
+
+        protected internal override Control? ScrollIntoView(int index)
+        {
+            return null;
+        }
+
+        protected override void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
+        {
+            base.OnItemsChanged(items, e);
+
+            void Add(int index, int count)
+            {
+                if (index <= _realizedIndex)
+                    _realizedIndex += count;
+            }
+
+            void Remove(int index, int count)
+            {
+                var end = index + (count - 1);
+
+                if (_realized is not null && index <= _realizedIndex && end >= _realizedIndex)
+                {
+                    RecycleElement(_realized);
+                    _realized = null;
+                    _realizedIndex = -1;
+                }
+                else if (index < _realizedIndex)
+                {
+                    _realizedIndex -= count;
+                }
+            }
+
+            switch (e.Action)
+            {
+                case NotifyCollectionChangedAction.Add:
+                    Add(e.NewStartingIndex, e.NewItems!.Count);
+                    break;
+                case NotifyCollectionChangedAction.Remove:
+                    Remove(e.OldStartingIndex, e.OldItems!.Count);
+                    break;
+                case NotifyCollectionChangedAction.Replace:
+                case NotifyCollectionChangedAction.Move:
+                    Remove(e.OldStartingIndex, e.OldItems!.Count);
+                    Add(e.NewStartingIndex, e.NewItems!.Count);
+                    break;
+                case NotifyCollectionChangedAction.Reset:
+                    if (_realized is not null)
+                    {
+                        RecycleElement(_realized);
+                        _realized = null;
+                        _realizedIndex = -1;
+                    }
+                    break;
+            }
+
+            InvalidateMeasure();
+        }
+
+        private Control GetOrCreateElement(IList items, int index)
+        {
+            return GetRealizedElement(index) ??
+                GetItemIsOwnContainer(items, index) ??
+                GetRecycledElement(items, index) ??
+                CreateElement(items, index);
+        }
+
+        private Control? GetRealizedElement(int index)
+        {
+            return _realizedIndex == index ? _realized : null;
+        }
+
+        private Control? GetItemIsOwnContainer(IList items, int index)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            if (items[index] is Control controlItem)
+            {
+                var generator = ItemsControl!.ItemContainerGenerator;
+
+                if (controlItem.IsSet(ItemIsOwnContainerProperty))
+                {
+                    controlItem.IsVisible = true;
+                    return controlItem;
+                }
+                else if (generator.IsItemItsOwnContainer(controlItem))
+                {
+                    AddInternalChild(controlItem);
+                    generator.PrepareItemContainer(controlItem, controlItem, index);
+                    controlItem.SetValue(ItemIsOwnContainerProperty, true);
+                    return controlItem;
+                }
+            }
+
+            return null;
+        }
+
+        private Control? GetRecycledElement(IList items, int index)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            var generator = ItemsControl!.ItemContainerGenerator;
+            var item = items[index];
+
+            if (_recyclePool?.Count > 0)
+            {
+                var recycled = _recyclePool.Pop();
+                recycled.IsVisible = true;
+                generator.PrepareItemContainer(recycled, item, index);
+                return recycled;
+            }
+
+            return null;
+        }
+
+        private Control CreateElement(IList items, int index)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            var generator = ItemsControl!.ItemContainerGenerator;
+            var item = items[index];
+            var container = generator.CreateContainer();
+
+            AddInternalChild(container);
+            generator.PrepareItemContainer(container, item, index);
+
+            return container;
+        }
+
+        private void RecycleElement(Control element)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            if (element.IsSet(ItemIsOwnContainerProperty))
+            {
+                element.IsVisible = false;
+            }
+            else
+            {
+                ItemsControl!.ItemContainerGenerator.ClearItemContainer(element);
+                _recyclePool ??= new();
+                _recyclePool.Push(element);
+                element.IsVisible = false;
+            }
+        }
+
+        private IPageTransition? GetTransition() => (ItemsControl as Carousel)?.PageTransition;
+
+        private void TransitionFinished(Task task)
+        {
+            if (task.IsCanceled)
+                return;
+
+            if (_transitionFrom is not null)
+                RecycleElement(_transitionFrom);
+            _transition = null;
+            _transitionFrom = null;
+            _transitionFromIndex = -1;
+        }
+    }
+}
diff --git a/src/Avalonia.Themes.Fluent/Controls/Carousel.xaml b/src/Avalonia.Themes.Fluent/Controls/Carousel.xaml
index 1dab50052d2..91e331693e6 100644
--- a/src/Avalonia.Themes.Fluent/Controls/Carousel.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/Carousel.xaml
@@ -3,16 +3,16 @@
   <ControlTheme x:Key="{x:Type Carousel}" TargetType="Carousel">
     <Setter Property="Template">
       <ControlTemplate>
-        <Border Background="{TemplateBinding Background}"
-                BorderBrush="{TemplateBinding BorderBrush}"
-                BorderThickness="{TemplateBinding BorderThickness}"
-                CornerRadius="{TemplateBinding CornerRadius}">
-          <CarouselPresenter IsVirtualized="{TemplateBinding IsVirtualized}"
-                             ItemsPanel="{TemplateBinding ItemsPanel}"
-                             Margin="{TemplateBinding Padding}"
-                             SelectedIndex="{TemplateBinding SelectedIndex}"
-                             PageTransition="{TemplateBinding PageTransition}"/>
-        </Border>
+        <ScrollViewer Name="PART_ScrollViewer"
+                      Background="{TemplateBinding Background}"
+                      BorderBrush="{TemplateBinding BorderBrush}"
+                      BorderThickness="{TemplateBinding BorderThickness}"
+                      HorizontalScrollBarVisibility="Hidden"
+                      VerticalScrollBarVisibility="Hidden">
+          <ItemsPresenter Name="PART_ItemsPresenter"
+                          ItemsPanel="{TemplateBinding ItemsPanel}"
+                          Margin="{TemplateBinding Padding}"/>
+        </ScrollViewer>
       </ControlTemplate>
     </Setter>
   </ControlTheme>
diff --git a/src/Avalonia.Themes.Simple/Controls/Carousel.xaml b/src/Avalonia.Themes.Simple/Controls/Carousel.xaml
index 66a4a1866a8..91e331693e6 100644
--- a/src/Avalonia.Themes.Simple/Controls/Carousel.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/Carousel.xaml
@@ -1,19 +1,18 @@
 <ResourceDictionary xmlns="https://github.com/avaloniaui"
                     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
-  <ControlTheme x:Key="{x:Type Carousel}"
-                TargetType="Carousel">
+  <ControlTheme x:Key="{x:Type Carousel}" TargetType="Carousel">
     <Setter Property="Template">
       <ControlTemplate>
-        <Border Background="{TemplateBinding Background}"
-                BorderBrush="{TemplateBinding BorderBrush}"
-                BorderThickness="{TemplateBinding BorderThickness}"
-                CornerRadius="{TemplateBinding CornerRadius}">
-          <CarouselPresenter Margin="{TemplateBinding Padding}"
-                             IsVirtualized="{TemplateBinding IsVirtualized}"
-                             ItemsPanel="{TemplateBinding ItemsPanel}"
-                             PageTransition="{TemplateBinding PageTransition}"
-                             SelectedIndex="{TemplateBinding SelectedIndex}" />
-        </Border>
+        <ScrollViewer Name="PART_ScrollViewer"
+                      Background="{TemplateBinding Background}"
+                      BorderBrush="{TemplateBinding BorderBrush}"
+                      BorderThickness="{TemplateBinding BorderThickness}"
+                      HorizontalScrollBarVisibility="Hidden"
+                      VerticalScrollBarVisibility="Hidden">
+          <ItemsPresenter Name="PART_ItemsPresenter"
+                          ItemsPanel="{TemplateBinding ItemsPanel}"
+                          Margin="{TemplateBinding Padding}"/>
+        </ScrollViewer>
       </ControlTemplate>
     </Setter>
   </ControlTheme>
diff --git a/tests/Avalonia.Controls.UnitTests/CarouselTests.cs b/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
index ddf471e5134..2b043e0e48b 100644
--- a/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
@@ -1,341 +1,321 @@
-////using System.Collections.ObjectModel;
-////using System.Linq;
-////using System.Reactive.Subjects;
-////using Avalonia.Controls.Presenters;
-////using Avalonia.Controls.Templates;
-////using Avalonia.Data;
-////using Avalonia.LogicalTree;
-////using Avalonia.UnitTests;
-////using Avalonia.VisualTree;
-////using Xunit;
-
-////namespace Avalonia.Controls.UnitTests
-////{
-////    public class CarouselTests
-////    {
-////        [Fact]
-////        public void First_Item_Should_Be_Selected_By_Default()
-////        {
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = new[]
-////                {
-////                    "Foo",
-////                    "Bar"
-////                }
-////            };
-
-////            target.ApplyTemplate();
-
-////            Assert.Equal(0, target.SelectedIndex);
-////            Assert.Equal("Foo", target.SelectedItem);
-////        }
-
-////        [Fact]
-////        public void LogicalChild_Should_Be_Selected_Item()
-////        {
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = new[]
-////                {
-////                    "Foo",
-////                    "Bar"
-////                }
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
-
-////            Assert.Single(target.GetLogicalChildren());
-
-////            var child = GetContainerTextBlock(target.GetLogicalChildren().Single());
-
-////            Assert.Equal("Foo", child.Text);
-////        }
-
-////        [Fact]
-////        public void Should_Remove_NonCurrent_Page_When_IsVirtualized_True()
-////        {
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = new[] { "foo", "bar" },
-////                IsVirtualized = true,
-////                SelectedIndex = 0,
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
-
-////            Assert.Single(target.ItemContainerGenerator.Containers);
-////            target.SelectedIndex = 1;
-////            Assert.Single(target.ItemContainerGenerator.Containers);
-////        }
-
-////        [Fact]
-////        public void Selected_Item_Changes_To_First_Item_When_Items_Property_Changes()
-////        {
-////            var items = new ObservableCollection<string>
-////            {
-////                "Foo",
-////                "Bar",
-////                "FooBar"
-////            };
-
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = items,
-////                IsVirtualized = false
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
-
-////            Assert.Equal(3, target.GetLogicalChildren().Count());
-
-////            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-////            Assert.Equal("Foo", child.Text);
-
-////            var newItems = items.ToList();
-////            newItems.RemoveAt(0);
-
-////            target.Items = newItems;
-
-////            child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-////            Assert.Equal("Bar", child.Text);
-////        }
-
-////        [Fact]
-////        public void Selected_Item_Changes_To_First_Item_When_Items_Property_Changes_And_Virtualized()
-////        {
-////            var items = new ObservableCollection<string>
-////            {
-////                "Foo",
-////                "Bar",
-////                "FooBar"
-////            };
-
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = items,
-////                IsVirtualized = true,
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
-
-////            Assert.Single(target.GetLogicalChildren());
-
-////            var child = GetContainerTextBlock(target.GetLogicalChildren().Single());
-
-////            Assert.Equal("Foo", child.Text);
-
-////            var newItems = items.ToList();
-////            newItems.RemoveAt(0);
-
-////            target.Items = newItems;
-
-////            child = GetContainerTextBlock(target.GetLogicalChildren().Single());
-
-////            Assert.Equal("Bar", child.Text);
-////        }
-
-////        [Fact]
-////        public void Selected_Item_Changes_To_First_Item_When_Item_Added()
-////        {
-////            var items = new ObservableCollection<string>();
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = items,
-////                IsVirtualized = false
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
+using System;
+using System.Collections.ObjectModel;
+using System.Linq;
+using System.Reactive.Subjects;
+using Avalonia.Controls.Presenters;
+using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Templates;
+using Avalonia.Data;
+using Avalonia.Layout;
+using Avalonia.LogicalTree;
+using Avalonia.UnitTests;
+using Avalonia.VisualTree;
+using Xunit;
+
+namespace Avalonia.Controls.UnitTests
+{
+    public class CarouselTests
+    {
+        [Fact]
+        public void First_Item_Should_Be_Selected_By_Default()
+        {
+            using var app = Start();
+            var target = new Carousel
+            {
+                Template = CarouselTemplate(),
+                Items = new[]
+                {
+                    "Foo",
+                    "Bar"
+                }
+            };
+
+            Prepare(target);
+
+            Assert.Equal(0, target.SelectedIndex);
+            Assert.Equal("Foo", target.SelectedItem);
+        }
+
+        [Fact]
+        public void LogicalChild_Should_Be_Selected_Item()
+        {
+            using var app = Start();
+            var target = new Carousel
+            {
+                Template = CarouselTemplate(),
+                Items = new[]
+                {
+                    "Foo",
+                    "Bar"
+                }
+            };
+
+            Prepare(target);
+
+            Assert.Single(target.GetRealizedContainers());
+
+            var child = GetContainerTextBlock(target.GetRealizedContainers().Single());
+
+            Assert.Equal("Foo", child.Text);
+        }
+
+        [Fact]
+        public void Selected_Item_Changes_To_First_Item_When_Items_Property_Changes()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string>
+            {
+                "Foo",
+                "Bar",
+                "FooBar"
+            };
+
+            var target = new Carousel
+            {
+                Template = CarouselTemplate(),
+                Items = items,
+            };
+
+            Prepare(target);
+
+            Assert.Single(target.GetRealizedContainers());
+
+            var child = GetContainerTextBlock(target.GetRealizedContainers().Single());
+
+            Assert.Equal("Foo", child.Text);
+
+            var newItems = items.ToList();
+            newItems.RemoveAt(0);
+            Layout(target);
+
+            target.Items = newItems;
+            Layout(target);
+
+            child = GetContainerTextBlock(target.GetRealizedContainers().Single());
+
+            Assert.Equal("Bar", child.Text);
+        }
+
+        [Fact]
+        public void Selected_Item_Changes_To_First_Item_When_Item_Added()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string>();
+            var target = new Carousel
+            {
+                Template = CarouselTemplate(),
+                Items = items,
+            };
+
+            Prepare(target);
+
+            Assert.Equal(-1, target.SelectedIndex);
+            Assert.Empty(target.GetRealizedContainers());
+
+            items.Add("Foo");
+            Layout(target);
+
+            Assert.Equal(0, target.SelectedIndex);
+            Assert.Single(target.GetRealizedContainers());
+        }
+
+        [Fact]
+        public void Selected_Index_Changes_To_None_When_Items_Assigned_Null()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string>
+            {
+                "Foo",
+                "Bar",
+                "FooBar"
+            };
+
+            var target = new Carousel
+            {
+                Template = CarouselTemplate(),
+                Items = items,
+            };
+
+            Prepare(target);
+
+            Assert.Equal(1, target.GetRealizedContainers().Count());
+
+            var child = GetContainerTextBlock(target.GetRealizedContainers().First());
+
+            Assert.Equal("Foo", child.Text);
+
+            target.Items = null;
+            Layout(target);
+
+            var numChildren = target.GetRealizedContainers().Count();
 
-////            Assert.Equal(-1, target.SelectedIndex);
-////            Assert.Empty(target.GetLogicalChildren());
+            Assert.Equal(-1, target.SelectedIndex);
+        }
 
-////            items.Add("Foo");
+        [Fact]
+        public void Selected_Index_Is_Maintained_Carousel_Created_With_Non_Zero_SelectedIndex()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string>
+            {
+                "Foo",
+                "Bar",
+                "FooBar"
+            };
+
+            var target = new Carousel
+            {
+                Template = CarouselTemplate(),
+                Items = items,
+                SelectedIndex = 2
+            };
 
-////            Assert.Equal(0, target.SelectedIndex);
-////            Assert.Single(target.GetLogicalChildren());
-////        }
+            Prepare(target);
+
+            Assert.Equal("FooBar", target.SelectedItem);
 
-////        [Fact]
-////        public void Selected_Index_Changes_To_None_When_Items_Assigned_Null()
-////        {
-////            var items = new ObservableCollection<string>
-////            {
-////                "Foo",
-////                "Bar",
-////                "FooBar"
-////            };
+            var child = GetContainerTextBlock(target.GetRealizedContainers().LastOrDefault());
 
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = items,
-////                IsVirtualized = false
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
-
-////            Assert.Equal(3, target.GetLogicalChildren().Count());
-
-////            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-////            Assert.Equal("Foo", child.Text);
-
-////            target.Items = null;
-
-////            var numChildren = target.GetLogicalChildren().Count();
-
-////            Assert.Equal(0, numChildren);
-////            Assert.Equal(-1, target.SelectedIndex);
-////        }
-
-////        [Fact]
-////        public void Selected_Index_Is_Maintained_Carousel_Created_With_Non_Zero_SelectedIndex()
-////        {
-////            var items = new ObservableCollection<string>
-////            {
-////                "Foo",
-////                "Bar",
-////                "FooBar"
-////            };
-
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = items,
-////                IsVirtualized = false,
-////                SelectedIndex = 2
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
-
-////            Assert.Equal("FooBar", target.SelectedItem);
-
-////            var child = GetContainerTextBlock(target.GetVisualDescendants().LastOrDefault());
-
-////            Assert.IsType<TextBlock>(child);
-////            Assert.Equal("FooBar", ((TextBlock)child).Text);
-////        }
-
-////        [Fact]
-////        public void Selected_Item_Changes_To_Next_First_Item_When_Item_Removed_From_Beggining_Of_List()
-////        {
-////            var items = new ObservableCollection<string>
-////            {
-////                "Foo",
-////                "Bar",
-////                "FooBar"
-////            };
-
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = items,
-////                IsVirtualized = false
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
-
-////            Assert.Equal(3, target.GetLogicalChildren().Count());
-
-////            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-////            Assert.Equal("Foo", child.Text);
-
-////            items.RemoveAt(0);
-
-////            child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-////            Assert.IsType<TextBlock>(child);
-////            Assert.Equal("Bar", ((TextBlock)child).Text);
-////        }
-
-////        [Fact]
-////        public void Selected_Item_Changes_To_First_Item_If_SelectedItem_Is_Removed_From_Middle()
-////        {
-////            var items = new ObservableCollection<string>
-////            {
-////                "Foo",
-////                "Bar",
-////                "FooBar"
-////            };
-
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = items,
-////                IsVirtualized = false
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
-
-////            target.SelectedIndex = 1;
-
-////            items.RemoveAt(1);
-
-////            Assert.Equal(0, target.SelectedIndex);
-////            Assert.Equal("Foo", target.SelectedItem);
-////        }
-
-////        private Control CreateTemplate(Carousel control, INameScope scope)
-////        {
-////            return new CarouselPresenter
-////            {
-////                Name = "PART_ItemsPresenter",
-////                [~CarouselPresenter.IsVirtualizedProperty] = control[~Carousel.IsVirtualizedProperty],
-////                [~CarouselPresenter.ItemsPanelProperty] = control[~Carousel.ItemsPanelProperty],
-////                [~CarouselPresenter.SelectedIndexProperty] = control[~Carousel.SelectedIndexProperty],
-////                [~CarouselPresenter.PageTransitionProperty] = control[~Carousel.PageTransitionProperty],
-////            }.RegisterInNameScope(scope);
-////        }
-
-////        private static TextBlock GetContainerTextBlock(object control)
-////        {
-////            var contentPresenter = Assert.IsType<ContentPresenter>(control);
-////            contentPresenter.UpdateChild();
-////            return Assert.IsType<TextBlock>(contentPresenter.Child);
-////        }
-
-////        [Fact]
-////        public void SelectedItem_Validation()
-////        {
-////            using (UnitTestApplication.Start(TestServices.MockThreadingInterface))
-////            {
-////                var target = new Carousel
-////                {
-////                    Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                    IsVirtualized = false
-////                };
-
-////                target.ApplyTemplate();
-////                ((Control)target.Presenter).ApplyTemplate();
-
-////                var exception = new System.InvalidCastException("failed validation");
-////                var textObservable =
-////                    new BehaviorSubject<BindingNotification>(new BindingNotification(exception,
-////                        BindingErrorType.DataValidationError));
-////                target.Bind(ComboBox.SelectedItemProperty, textObservable);
-
-////                Assert.True(DataValidationErrors.GetHasErrors(target));
-////                Assert.True(DataValidationErrors.GetErrors(target).SequenceEqual(new[] { exception }));
-////            }
-////        }
-////    }
-////}
+            Assert.Equal("FooBar", child.Text);
+        }
+
+        [Fact]
+        public void Selected_Item_Changes_To_Next_First_Item_When_Item_Removed_From_Beggining_Of_List()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string>
+            {
+                "Foo",
+                "Bar",
+                "FooBar"
+            };
+
+            var target = new Carousel
+            {
+                Template = CarouselTemplate(),
+                Items = items,
+            };
+
+            Prepare(target);
+
+            var child = GetContainerTextBlock(target.GetRealizedContainers().First());
+
+            Assert.Equal("Foo", child.Text);
+
+            items.RemoveAt(0);
+            Layout(target);
+
+            child = GetContainerTextBlock(target.GetRealizedContainers().First());
+
+            Assert.IsType<TextBlock>(child);
+            Assert.Equal("Bar", child.Text);
+        }
+
+        [Fact]
+        public void Selected_Item_Changes_To_First_Item_If_SelectedItem_Is_Removed_From_Middle()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string>
+            {
+                "Foo",
+                "Bar",
+                "FooBar"
+            };
+
+            var target = new Carousel
+            {
+                Template = CarouselTemplate(),
+                Items = items,
+            };
+
+            Prepare(target);
+
+            target.SelectedIndex = 1;
+
+            items.RemoveAt(1);
+
+            Assert.Equal(0, target.SelectedIndex);
+            Assert.Equal("Foo", target.SelectedItem);
+        }
+
+        [Fact]
+        public void SelectedItem_Validation()
+        {
+            using (UnitTestApplication.Start(TestServices.MockThreadingInterface))
+            {
+                var target = new Carousel
+                {
+                    Template = CarouselTemplate(),
+                };
+
+                Prepare(target);
+
+                var exception = new System.InvalidCastException("failed validation");
+                var textObservable =
+                    new BehaviorSubject<BindingNotification>(new BindingNotification(exception,
+                        BindingErrorType.DataValidationError));
+                target.Bind(ComboBox.SelectedItemProperty, textObservable);
+
+                Assert.True(DataValidationErrors.GetHasErrors(target));
+                Assert.True(DataValidationErrors.GetErrors(target).SequenceEqual(new[] { exception }));
+            }
+        }
+
+        private static IDisposable Start() => UnitTestApplication.Start(TestServices.MockPlatformRenderInterface);
+
+        private static void Prepare(Carousel target)
+        {
+            var root = new TestRoot(target);
+            root.LayoutManager.ExecuteInitialLayoutPass();
+        }
+
+        private static void Layout(Carousel target)
+        {
+            ((ILayoutRoot)target.GetVisualRoot()).LayoutManager.ExecuteLayoutPass();
+        }
+
+        private static IControlTemplate CarouselTemplate()
+        {
+            return new FuncControlTemplate((c, ns) =>
+                new ScrollViewer
+                {
+                    Name = "PART_ScrollViewer",
+                    Template = ScrollViewerTemplate(),
+                    HorizontalScrollBarVisibility = ScrollBarVisibility.Hidden,
+                    VerticalScrollBarVisibility = ScrollBarVisibility.Hidden,
+                    Content = new ItemsPresenter
+                    {
+                        Name = "PART_ItemsPresenter",
+                        [~ItemsPresenter.ItemsPanelProperty] = c[~ItemsControl.ItemsPanelProperty],
+                    }.RegisterInNameScope(ns)
+                }.RegisterInNameScope(ns));
+        }
+
+        private static FuncControlTemplate ScrollViewerTemplate()
+        {
+            return new FuncControlTemplate<ScrollViewer>((parent, scope) =>
+                new Panel
+                {
+                    Children =
+                    {
+                        new ScrollContentPresenter
+                        {
+                            Name = "PART_ContentPresenter",
+                            [~ScrollContentPresenter.ContentProperty] = parent.GetObservable(ScrollViewer.ContentProperty).ToBinding(),
+                            [~~ScrollContentPresenter.ExtentProperty] = parent[~~ScrollViewer.ExtentProperty],
+                            [~~ScrollContentPresenter.OffsetProperty] = parent[~~ScrollViewer.OffsetProperty],
+                            [~~ScrollContentPresenter.ViewportProperty] = parent[~~ScrollViewer.ViewportProperty],
+                            [~ScrollContentPresenter.CanHorizontallyScrollProperty] = parent[~ScrollViewer.CanHorizontallyScrollProperty],
+                            [~ScrollContentPresenter.CanVerticallyScrollProperty] = parent[~ScrollViewer.CanVerticallyScrollProperty],
+                        }.RegisterInNameScope(scope),
+                    }
+                });
+        }
+
+        private static TextBlock GetContainerTextBlock(object control)
+        {
+            var contentPresenter = Assert.IsType<ContentPresenter>(control);
+            return Assert.IsType<TextBlock>(contentPresenter.Child);
+        }
+    }
+}
diff --git a/tests/Avalonia.Controls.UnitTests/Presenters/CarouselPresenterTests.cs b/tests/Avalonia.Controls.UnitTests/Presenters/CarouselPresenterTests.cs
deleted file mode 100644
index f5094accb58..00000000000
--- a/tests/Avalonia.Controls.UnitTests/Presenters/CarouselPresenterTests.cs
+++ /dev/null
@@ -1,732 +0,0 @@
-////using System.Linq;
-////using Moq;
-////using Avalonia.Controls.Generators;
-////using Avalonia.Controls.Presenters;
-////using Avalonia.Controls.Templates;
-////using Xunit;
-////using System.Collections.ObjectModel;
-////using System.Collections;
-
-////namespace Avalonia.Controls.UnitTests.Presenters
-////{
-////    public class CarouselPresenterTests
-////    {
-////        [Fact]
-////        public void Should_Register_With_Host_When_TemplatedParent_Set()
-////        {
-////            var host = new Carousel();
-////            var target = new CarouselPresenter();
-
-////            Assert.Null(host.Presenter);
-
-////            target.SetValue(Control.TemplatedParentProperty, host);
-
-////            Assert.Same(target, host.Presenter);
-////        }
-
-////        [Fact]
-////        public void ApplyTemplate_Should_Create_Panel()
-////        {
-////            var target = new CarouselPresenter
-////            {
-////                ItemsPanel = new FuncTemplate<Panel>(() => new Panel()),
-////            };
-
-////            target.ApplyTemplate();
-
-////            Assert.IsType<Panel>(target.Panel);
-////        }
-
-////        [Fact]
-////        public void ItemContainerGenerator_Should_Be_Picked_Up_From_TemplatedControl()
-////        {
-////            var parent = new TestItemsControl();
-////            var target = new CarouselPresenter
-////            {
-////                [StyledElement.TemplatedParentProperty] = parent,
-////            };
-
-////            Assert.IsType<ItemContainerGenerator<TestItem>>(target.ItemContainerGenerator);
-////        }
-
-////        public class Virtualized
-////        {
-////            [Fact]
-////            public void Should_Initially_Materialize_Selected_Container()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    SelectedIndex = 0,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Should_Initially_Materialize_Nothing_If_No_Selected_Container()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                Assert.Empty(target.Panel.Children);
-////                Assert.Empty(target.ItemContainerGenerator.Containers);
-////            }
-
-////            [Fact]
-////            public void Switching_To_Virtualized_Should_Reset_Containers()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    SelectedIndex = 0,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-////                target.IsVirtualized = true;
-
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Changing_SelectedIndex_Should_Show_Page()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    SelectedIndex = 0,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-////                AssertSingle(target);
-
-////                target.SelectedIndex = 1;
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Should_Remove_NonCurrent_Page()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    IsVirtualized = true,
-////                    SelectedIndex = 0,
-////                };
-
-////                target.ApplyTemplate();
-////                AssertSingle(target);
-
-////                target.SelectedIndex = 1;
-////                AssertSingle(target);
-
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Inserting_Item_At_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.Insert(1, "item1a");
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Inserting_Item_Before_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 2,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.Insert(1, "item1a");
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Should_Do_Nothing_When_Inserting_Item_After_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-////                var child = AssertSingle(target);
-////                items.Insert(2, "after");
-////                Assert.Same(child, AssertSingle(target));
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_Item_At_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.RemoveAt(1);
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_Item_Before_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.RemoveAt(0);
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Should_Do_Nothing_When_Removing_Item_After_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-////                var child = AssertSingle(target);
-////                items.RemoveAt(2);
-////                Assert.Same(child, AssertSingle(target));
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_SelectedItem_When_Its_Last()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 2,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.RemoveAt(2);
-////                Assert.Equal(1, target.SelectedIndex);
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_Last_Item()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 0,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.RemoveAt(0);
-////                Assert.Empty(target.Panel.Children);
-////                Assert.Empty(target.ItemContainerGenerator.Containers);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Replacing_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items[1] = "replaced";
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Should_Do_Nothing_When_Replacing_Non_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-////                var child = AssertSingle(target);
-////                items[0] = "replaced";
-////                Assert.Same(child, AssertSingle(target));
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Moving_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.Move(1, 0);
-////                AssertSingle(target);
-////            }
-
-////            private static Control AssertSingle(CarouselPresenter target)
-////            {
-////                var items = (IList)target.Items;
-////                var index = target.SelectedIndex;
-////                var content = items[index];
-////                var child = Assert.Single(target.Panel.Children);
-////                var presenter = Assert.IsType<ContentPresenter>(child);
-////                var container = Assert.Single(target.ItemContainerGenerator.Containers);
-////                var visible = Assert.Single(target.Panel.Children.Where(x => x.IsVisible));
-
-////                Assert.Same(child, container.ContainerControl);
-////                Assert.Same(child, visible);
-////                Assert.Equal(content, presenter.Content);
-////                Assert.Equal(content, container.Item);
-////                Assert.Equal(index, container.Index);
-
-////                return child;
-////            }
-////        }
-
-////        public class NonVirtualized
-////        {
-////            [Fact]
-////            public void Should_Initially_Materialize_All_Containers()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Initially_Show_Selected_Item()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    SelectedIndex = 1,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Switching_To_Non_Virtualized_Should_Reset_Containers()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    SelectedIndex = 0,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-////                target.IsVirtualized = false;
-
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Changing_SelectedIndex_Should_Show_Page()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    SelectedIndex = 0,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-////                AssertAll(target);
-
-////                target.SelectedIndex = 1;
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Inserting_Item_At_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.Insert(1, "item1a");
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Inserting_Item_Before_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 2,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.Insert(1, "item1a");
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Do_Handle_Inserting_Item_After_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-////                items.Insert(2, "after");
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_Item_At_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.RemoveAt(1);
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_Item_Before_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.RemoveAt(0);
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_Item_After_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-////                items.RemoveAt(2);
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_SelectedItem_When_Its_Last()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 2,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.RemoveAt(2);
-////                Assert.Equal(1, target.SelectedIndex);
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_Last_Item()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 0,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.RemoveAt(0);
-////                Assert.Empty(target.Panel.Children);
-////                Assert.Empty(target.ItemContainerGenerator.Containers);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Replacing_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items[1] = "replaced";
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Moving_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.Move(1, 0);
-////                AssertAll(target);
-////            }
-
-////            private static void AssertAll(CarouselPresenter target)
-////            {
-////                var items = (IList)target.Items;
-
-////                Assert.Equal(items?.Count ?? 0, target.Panel.Children.Count);
-////                Assert.Equal(items?.Count ?? 0, target.ItemContainerGenerator.Containers.Count());
-
-////                for (var i = 0; i < items?.Count; ++i)
-////                {
-////                    var content = items[i];
-////                    var child = target.Panel.Children[i];
-////                    var presenter = Assert.IsType<ContentPresenter>(child);
-////                    var container = target.ItemContainerGenerator.ContainerFromIndex(i);
-
-////                    Assert.Same(child, container);
-////                    Assert.Equal(i == target.SelectedIndex, child.IsVisible);
-////                    Assert.Equal(content, presenter.Content);
-////                    Assert.Equal(i, target.ItemContainerGenerator.IndexFromContainer(container));
-////                }
-////            }
-////        }
-
-////        private class TestItem : ContentControl
-////        {
-////        }
-
-////        private class TestItemsControl : ItemsControl
-////        {
-////            protected override IItemContainerGenerator CreateItemContainerGenerator()
-////            {
-////                return new ItemContainerGenerator<TestItem>(this, TestItem.ContentProperty, null);
-////            }
-////        }
-////    }
-////}
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingCarouselPanelTests.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingCarouselPanelTests.cs
new file mode 100644
index 00000000000..ea6b9367cf7
--- /dev/null
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingCarouselPanelTests.cs
@@ -0,0 +1,271 @@
+using System;
+using System.Collections;
+using System.Collections.ObjectModel;
+using System.Threading;
+using System.Threading.Tasks;
+using Avalonia.Animation;
+using Avalonia.Controls.Presenters;
+using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Templates;
+using Avalonia.Layout;
+using Avalonia.UnitTests;
+using Avalonia.VisualTree;
+using Moq;
+using Xunit;
+
+#nullable enable
+
+namespace Avalonia.Controls.UnitTests
+{
+    public class VirtualizingCarouselPanelTests
+    {
+        [Fact]
+        public void Initial_Item_Is_Displayed()
+        {
+            using var app = Start();
+            var items = new[] { "foo", "bar" };
+            var (target, _) = CreateTarget(items);
+
+            Assert.Single(target.Children);
+            var container = Assert.IsType<ContentPresenter>(target.Children[0]);
+            Assert.Equal("foo", container.Content);
+        }
+
+        [Fact]
+        public void Displays_Next_Item()
+        {
+            using var app = Start();
+            var items = new[] { "foo", "bar" };
+            var (target, carousel) = CreateTarget(items);
+
+            carousel.SelectedIndex = 1;
+            Layout(target);
+
+            Assert.Single(target.Children);
+            var container = Assert.IsType<ContentPresenter>(target.Children[0]);
+            Assert.Equal("bar", container.Content);
+        }
+
+        [Fact]
+        public void Handles_Inserted_Item()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string> { "foo", "bar" };
+            var (target, carousel) = CreateTarget(items);
+            var container = Assert.IsType<ContentPresenter>(target.Children[0]);
+
+            items.Insert(0, "baz");
+            Layout(target);
+
+            Assert.Single(target.Children);
+            Assert.Same(container, target.Children[0]);
+            Assert.Equal("foo", container.Content);
+        }
+
+        [Fact]
+        public void Handles_Removed_Item()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string> { "foo", "bar" };
+            var (target, carousel) = CreateTarget(items);
+            var container = Assert.IsType<ContentPresenter>(target.Children[0]);
+
+            items.RemoveAt(0);
+            Layout(target);
+
+            Assert.Single(target.Children);
+            Assert.Same(container, target.Children[0]);
+            Assert.Equal("bar", container.Content);
+        }
+
+        [Fact]
+        public void Handles_Replaced_Item()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string> { "foo", "bar" };
+            var (target, carousel) = CreateTarget(items);
+            var container = Assert.IsType<ContentPresenter>(target.Children[0]);
+
+            items[0] = "baz";
+            Layout(target);
+
+            Assert.Single(target.Children);
+            Assert.Same(container, target.Children[0]);
+            Assert.Equal("baz", container.Content);
+        }
+
+        [Fact]
+        public void Handles_Moved_Item()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string> { "foo", "bar" };
+            var (target, carousel) = CreateTarget(items);
+            var container = Assert.IsType<ContentPresenter>(target.Children[0]);
+
+            items.Move(0, 1);
+            Layout(target);
+
+            Assert.Single(target.Children);
+            Assert.Same(container, target.Children[0]);
+            Assert.Equal("bar", container.Content);
+        }
+
+        public class Transitions
+        {
+            [Fact]
+            public void Initial_Item_Does_Not_Start_Transition()
+            {
+                using var app = Start();
+                var items = new Control[] { new Button(), new Canvas() };
+                var transition = new Mock<IPageTransition>();
+                var (target, _) = CreateTarget(items, transition.Object);
+
+                transition.Verify(x => x.Start(
+                        It.IsAny<Visual>(),
+                        It.IsAny<Visual>(),
+                        It.IsAny<bool>(),
+                        It.IsAny<CancellationToken>()),
+                    Times.Never);
+            }
+
+            [Fact]
+            public void Changing_SelectedIndex_Starts_Transition()
+            {
+                using var app = Start();
+                var items = new Control[] { new Button(), new Canvas() };
+                var transition = new Mock<IPageTransition>();
+                var (target, carousel) = CreateTarget(items, transition.Object);
+
+                carousel.SelectedIndex = 1;
+                Layout(target);
+
+                transition.Verify(x => x.Start(
+                        items[0],
+                        items[1],
+                        true,
+                        It.IsAny<CancellationToken>()),
+                    Times.Once);
+            }
+
+            [Fact]
+            public void TransitionFrom_Control_Is_Recycled_When_Transition_Completes()
+            {
+                using var app = Start();
+                using var sync = UnitTestSynchronizationContext.Begin();
+                var items = new Control[] { new Button(), new Canvas() };
+                var transition = new Mock<IPageTransition>();
+                var (target, carousel) = CreateTarget(items, transition.Object);
+                var transitionTask = new TaskCompletionSource();
+
+                transition.Setup(x => x.Start(
+                        items[0],
+                        items[1],
+                        true,
+                        It.IsAny<CancellationToken>()))
+                    .Returns(() => transitionTask.Task);
+                
+                carousel.SelectedIndex = 1;
+                Layout(target);
+
+                Assert.Equal(items, target.Children);
+                Assert.All(items, x => Assert.True(x.IsVisible));
+                
+                transitionTask.SetResult();
+                sync.ExecutePostedCallbacks();
+
+                Assert.Equal(items, target.Children);
+                Assert.False(items[0].IsVisible);
+                Assert.True(items[1].IsVisible);
+            }
+
+            [Fact]
+            public void Existing_Transition_Is_Canceled_If_Interrupted()
+            {
+                using var app = Start();
+                using var sync = UnitTestSynchronizationContext.Begin();
+                var items = new Control[] { new Button(), new Canvas() };
+                var transition = new Mock<IPageTransition>();
+                var (target, carousel) = CreateTarget(items, transition.Object);
+                var transitionTask = new TaskCompletionSource();
+                CancellationToken? cancelationToken = null;
+
+                transition.Setup(x => x.Start(
+                        items[0],
+                        items[1],
+                        true,
+                        It.IsAny<CancellationToken>()))
+                    .Callback<Visual, Visual, bool, CancellationToken>((_, _, _, c) => cancelationToken = c)
+                    .Returns(() => transitionTask.Task);
+
+                carousel.SelectedIndex = 1;
+                Layout(target);
+
+                Assert.NotNull(cancelationToken);
+                Assert.False(cancelationToken!.Value.IsCancellationRequested);
+
+                carousel.SelectedIndex = 0;
+                Layout(target);
+
+                Assert.True(cancelationToken!.Value.IsCancellationRequested);
+            }
+        }
+
+        private static IDisposable Start() => UnitTestApplication.Start(TestServices.MockPlatformRenderInterface);
+
+        private static (VirtualizingCarouselPanel, Carousel) CreateTarget(
+            IEnumerable items,
+            IPageTransition? transition = null)
+        {
+            var carousel = new Carousel
+            {
+                Items = items,
+                Template = CarouselTemplate(),
+                PageTransition = transition,
+            };
+
+            var root = new TestRoot(carousel);
+            root.LayoutManager.ExecuteInitialLayoutPass();
+            return ((VirtualizingCarouselPanel)carousel.Presenter!.Panel!, carousel);
+        }
+
+        private static IControlTemplate CarouselTemplate()
+        {
+            return new FuncControlTemplate((c, ns) =>
+                new ScrollViewer
+                {
+                    Name = "PART_ScrollViewer",
+                    Template = ScrollViewerTemplate(),
+                    HorizontalScrollBarVisibility = ScrollBarVisibility.Hidden,
+                    VerticalScrollBarVisibility = ScrollBarVisibility.Hidden,
+                    Content = new ItemsPresenter
+                    {
+                        Name = "PART_ItemsPresenter",
+                        [~ItemsPresenter.ItemsPanelProperty] = c[~ItemsControl.ItemsPanelProperty],
+                    }.RegisterInNameScope(ns)
+                }.RegisterInNameScope(ns));
+        }
+
+        private static FuncControlTemplate ScrollViewerTemplate()
+        {
+            return new FuncControlTemplate<ScrollViewer>((parent, scope) =>
+                new Panel
+                {
+                    Children =
+                    {
+                        new ScrollContentPresenter
+                        {
+                            Name = "PART_ContentPresenter",
+                            [~ScrollContentPresenter.ContentProperty] = parent.GetObservable(ScrollViewer.ContentProperty).ToBinding(),
+                            [~~ScrollContentPresenter.ExtentProperty] = parent[~~ScrollViewer.ExtentProperty],
+                            [~~ScrollContentPresenter.OffsetProperty] = parent[~~ScrollViewer.OffsetProperty],
+                            [~~ScrollContentPresenter.ViewportProperty] = parent[~~ScrollViewer.ViewportProperty],
+                            [~ScrollContentPresenter.CanHorizontallyScrollProperty] = parent[~ScrollViewer.CanHorizontallyScrollProperty],
+                            [~ScrollContentPresenter.CanVerticallyScrollProperty] = parent[~ScrollViewer.CanVerticallyScrollProperty],
+                        }.RegisterInNameScope(scope),
+                    }
+                });
+        }
+
+        private static void Layout(Control c) => ((ILayoutRoot)c.GetVisualRoot()!).LayoutManager.ExecuteLayoutPass();
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/UnitTestSynchronizationContext.cs b/tests/Avalonia.UnitTests/UnitTestSynchronizationContext.cs
similarity index 91%
rename from tests/Avalonia.Base.UnitTests/Data/UnitTestSynchronizationContext.cs
rename to tests/Avalonia.UnitTests/UnitTestSynchronizationContext.cs
index 71eed38a4c9..23cea7ad4f4 100644
--- a/tests/Avalonia.Base.UnitTests/Data/UnitTestSynchronizationContext.cs
+++ b/tests/Avalonia.UnitTests/UnitTestSynchronizationContext.cs
@@ -1,11 +1,10 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Disposables;
 using System.Threading;
 
-namespace Avalonia.Base.UnitTests.Data
+namespace Avalonia.UnitTests
 {
-    internal sealed class UnitTestSynchronizationContext : SynchronizationContext
+    public sealed class UnitTestSynchronizationContext : SynchronizationContext
     {
         readonly List<Tuple<SendOrPostCallback, object>> _postedCallbacks =
             new List<Tuple<SendOrPostCallback, object>>();

From c54e466db127478127b98983c8bc4037a77e6670 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 09:50:46 +0100
Subject: [PATCH 34/64] Remove `FillMode` on transitions.

Now that containers are being recycled, the state of the control following the animation needs to be the same as before the animation.
---
 src/Avalonia.Base/Animation/PageSlide.cs                      | 2 --
 src/Avalonia.Base/Animation/Transitions/Rotate3DTransition.cs | 2 --
 2 files changed, 4 deletions(-)

diff --git a/src/Avalonia.Base/Animation/PageSlide.cs b/src/Avalonia.Base/Animation/PageSlide.cs
index 609441ae8cf..f388de57944 100644
--- a/src/Avalonia.Base/Animation/PageSlide.cs
+++ b/src/Avalonia.Base/Animation/PageSlide.cs
@@ -79,7 +79,6 @@ public virtual async Task Start(Visual? from, Visual? to, bool forward, Cancella
                 var animation = new Animation
                 {
                     Easing = SlideOutEasing,
-                    FillMode = FillMode.Forward,
                     Children =
                     {
                         new KeyFrame
@@ -110,7 +109,6 @@ public virtual async Task Start(Visual? from, Visual? to, bool forward, Cancella
                 to.IsVisible = true;
                 var animation = new Animation
                 {
-                    FillMode = FillMode.Forward,
                     Easing = SlideInEasing,
                     Children =
                     {
diff --git a/src/Avalonia.Base/Animation/Transitions/Rotate3DTransition.cs b/src/Avalonia.Base/Animation/Transitions/Rotate3DTransition.cs
index 239f3aea082..b4a1f02f090 100644
--- a/src/Avalonia.Base/Animation/Transitions/Rotate3DTransition.cs
+++ b/src/Avalonia.Base/Animation/Transitions/Rotate3DTransition.cs
@@ -71,7 +71,6 @@ KeyFrame CreateKeyFrame(double cue, double rotation, int zIndex, bool isVisible
             {
                 Easing = SlideOutEasing,
                 Duration = Duration,
-                FillMode = FillMode.Forward,
                 Children =
                 {
                     CreateKeyFrame(0d, 0d, 2),
@@ -90,7 +89,6 @@ KeyFrame CreateKeyFrame(double cue, double rotation, int zIndex, bool isVisible
             {
                 Easing = SlideInEasing,
                 Duration = Duration,
-                FillMode = FillMode.Forward,
                 Children =
                 {
                     CreateKeyFrame(0d, 90d * (forward ? 1 : -1), 1),

From 06de4bb8ab9e7862befba4cb053def32d30e4332 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 10:10:30 +0100
Subject: [PATCH 35/64] Update comment.

---
 src/Avalonia.Controls/ItemsControl.cs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index b512d3583c4..3d70c4975c5 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -346,7 +346,8 @@ protected virtual void ContainerIndexChangedOverride(Control container, int oldI
         /// <param name="container">The container element.</param>
         protected internal virtual void ClearContainerForItemOverride(Control container)
         {
-            // TODO: Remove HeaderedItemsControl.Items binding.
+            // Feels like we should be clearing the HeaderedItemsControl.Items binding here, but looking at
+            // the WPF source it seems that this isn't done there.
         }
 
         /// <summary>

From 627d9c5d058206d2a11d4fb1aad3eed9b8fb34e6 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 11:11:19 +0100
Subject: [PATCH 36/64] Make VirtualizationDemo compile again.

---
 samples/VirtualizationDemo/MainWindow.xaml             |  3 ---
 .../ViewModels/MainWindowViewModel.cs                  | 10 ----------
 2 files changed, 13 deletions(-)

diff --git a/samples/VirtualizationDemo/MainWindow.xaml b/samples/VirtualizationDemo/MainWindow.xaml
index 4e8a5c386b5..7748ebcc03e 100644
--- a/samples/VirtualizationDemo/MainWindow.xaml
+++ b/samples/VirtualizationDemo/MainWindow.xaml
@@ -11,8 +11,6 @@
                     Margin="16 0 0 0" 
                     MinWidth="150"
                     Spacing="4">
-            <ComboBox Items="{Binding VirtualizationModes}"
-                      SelectedItem="{Binding VirtualizationMode}"/>
             <ComboBox Items="{Binding Orientations}"
                       SelectedItem="{Binding Orientation}"/>
             <TextBox Watermark="Item Count"
@@ -49,7 +47,6 @@
                  Items="{Binding Items}" 
                  Selection="{Binding Selection}"
                  SelectionMode="Multiple"
-                 VirtualizationMode="{Binding VirtualizationMode}"
                  ScrollViewer.HorizontalScrollBarVisibility="{Binding HorizontalScrollBarVisibility, Mode=TwoWay}"
                  ScrollViewer.VerticalScrollBarVisibility="{Binding VerticalScrollBarVisibility, Mode=TwoWay}">
             <ListBox.ItemsPanel>
diff --git a/samples/VirtualizationDemo/ViewModels/MainWindowViewModel.cs b/samples/VirtualizationDemo/ViewModels/MainWindowViewModel.cs
index 514df691aed..96dbbc1a839 100644
--- a/samples/VirtualizationDemo/ViewModels/MainWindowViewModel.cs
+++ b/samples/VirtualizationDemo/ViewModels/MainWindowViewModel.cs
@@ -21,7 +21,6 @@ internal class MainWindowViewModel : ViewModelBase
         private ScrollBarVisibility _horizontalScrollBarVisibility = ScrollBarVisibility.Auto;
         private ScrollBarVisibility _verticalScrollBarVisibility = ScrollBarVisibility.Auto;
         private Orientation _orientation = Orientation.Vertical;
-        private ItemVirtualizationMode _virtualizationMode = ItemVirtualizationMode.Simple;
 
         public MainWindowViewModel()
         {
@@ -81,15 +80,6 @@ public ScrollBarVisibility VerticalScrollBarVisibility
         public IEnumerable<ScrollBarVisibility> ScrollBarVisibilities =>
             Enum.GetValues(typeof(ScrollBarVisibility)).Cast<ScrollBarVisibility>();
 
-        public ItemVirtualizationMode VirtualizationMode
-        {
-            get { return _virtualizationMode; }
-            set { this.RaiseAndSetIfChanged(ref _virtualizationMode, value); }
-        }
-
-        public IEnumerable<ItemVirtualizationMode> VirtualizationModes => 
-            Enum.GetValues(typeof(ItemVirtualizationMode)).Cast<ItemVirtualizationMode>();
-
         public MiniCommand AddItemCommand { get; private set; }
         public MiniCommand RecreateCommand { get; private set; }
         public MiniCommand RemoveItemCommand { get; private set; }

From 3195df0910a7c1b44a770624b5eb5e461485f205 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 13:55:21 +0100
Subject: [PATCH 37/64] Use ItemsSourceView in ItemsControl.

Fixes #54.
---
 src/Avalonia.Controls/Carousel.cs             |   2 +-
 src/Avalonia.Controls/ItemsControl.cs         | 221 +++++-----------
 src/Avalonia.Controls/ItemsSourceView.cs      | 240 ++++++++++--------
 src/Avalonia.Controls/MenuItem.cs             |   2 +-
 .../Presenters/PanelContainerGenerator.cs     |  11 +-
 .../Primitives/SelectingItemsControl.cs       |   2 +-
 .../Repeater/ItemsRepeater.cs                 |   1 -
 .../Selection/SelectionNodeBase.cs            |   6 +-
 src/Avalonia.Controls/TreeView.cs             |   9 +-
 src/Avalonia.Controls/TreeViewItem.cs         |   4 +-
 .../VirtualizingCarouselPanel.cs              |  12 +-
 src/Avalonia.Controls/VirtualizingPanel.cs    |  22 +-
 .../VirtualizingStackPanel.cs                 |  25 +-
 13 files changed, 244 insertions(+), 313 deletions(-)

diff --git a/src/Avalonia.Controls/Carousel.cs b/src/Avalonia.Controls/Carousel.cs
index a9ffb2119a4..84601e86908 100644
--- a/src/Avalonia.Controls/Carousel.cs
+++ b/src/Avalonia.Controls/Carousel.cs
@@ -48,7 +48,7 @@ public IPageTransition? PageTransition
         /// </summary>
         public void Next()
         {
-            if (SelectedIndex < Items.Count() - 1)
+            if (SelectedIndex < ItemCount - 1)
             {
                 ++SelectedIndex;
             }
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 3d70c4975c5..b797ae82951 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -2,7 +2,7 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
-using System.Linq;
+using System.Diagnostics.CodeAnalysis;
 using Avalonia.Automation.Peers;
 using Avalonia.Collections;
 using Avalonia.Controls.Generators;
@@ -10,7 +10,6 @@
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Templates;
-using Avalonia.Controls.Utils;
 using Avalonia.Data;
 using Avalonia.Input;
 using Avalonia.LogicalTree;
@@ -24,7 +23,7 @@ namespace Avalonia.Controls
     /// Displays a collection of items.
     /// </summary>
     [PseudoClasses(":empty", ":singleitem")]
-    public class ItemsControl : TemplatedControl, IItemsPresenterHost, ICollectionChangedListener, IChildIndexProvider
+    public class ItemsControl : TemplatedControl, IItemsPresenterHost, IChildIndexProvider
     {
         /// <summary>
         /// The default value for the <see cref="ItemsPanel"/> property.
@@ -62,6 +61,11 @@ public class ItemsControl : TemplatedControl, IItemsPresenterHost, ICollectionCh
         public static readonly StyledProperty<IDataTemplate?> ItemTemplateProperty =
             AvaloniaProperty.Register<ItemsControl, IDataTemplate?>(nameof(ItemTemplate));
 
+        /// <summary>
+        /// Defines the <see cref="ItemsView"/> property.
+        /// </summary>
+        public static readonly DirectProperty<ItemsControl, ItemsSourceView> ItemsViewProperty =
+            AvaloniaProperty.RegisterDirect<ItemsControl, ItemsSourceView>(nameof(Items), o => o.ItemsView);
 
         /// <summary>
         /// Defines the <see cref="DisplayMemberBinding" /> property
@@ -80,27 +84,21 @@ public IBinding? DisplayMemberBinding
         }
         
         private IEnumerable? _items = new AvaloniaList<object>();
+        private ItemsSourceView _itemsView;
         private int _itemCount;
         private ItemContainerGenerator? _itemContainerGenerator;
         private EventHandler<ChildIndexChangedEventArgs>? _childIndexChanged;
         private IDataTemplate? _displayMemberItemTemplate;
         private Tuple<int, Control>? _containerBeingPrepared;
 
-        /// <summary>
-        /// Initializes static members of the <see cref="ItemsControl"/> class.
-        /// </summary>
-        static ItemsControl()
-        {
-            ItemsProperty.Changed.AddClassHandler<ItemsControl>((x, e) => x.ItemsChanged(e));
-        }
-
         /// <summary>
         /// Initializes a new instance of the <see cref="ItemsControl"/> class.
         /// </summary>
         public ItemsControl()
         {
+            _itemsView = new(_items);
+            _itemsView.PostCollectionChanged += ItemsCollectionChanged;
             UpdatePseudoClasses(0);
-            SubscribeToItems(_items);
         }
 
         /// <summary>
@@ -164,6 +162,33 @@ public IDataTemplate? ItemTemplate
         /// </summary>
         public ItemsPresenter? Presenter { get; private set; }
 
+        /// <summary>
+        /// Gets a standardized view over <see cref="Items"/>.
+        /// </summary>
+        /// <remarks>
+        /// The <see cref="Items"/> property may be an enumerable which does not implement
+        /// <see cref="IList"/> or may be null. This view can be used to provide a standardized
+        /// view of the current items regardless of the type of the concrete collection, and
+        /// without having to deal with null values.
+        /// </remarks>
+        public ItemsSourceView ItemsView 
+        {
+            get => _itemsView;
+            private set
+            {
+                if (ReferenceEquals(_itemsView, value))
+                    return;
+
+                var oldValue = _itemsView;
+                RemoveControlItemsFromLogicalChildren(_itemsView);
+                _itemsView.PostCollectionChanged -= ItemsCollectionChanged;
+                _itemsView = value;
+                _itemsView.PostCollectionChanged += ItemsCollectionChanged;
+                AddControlItemsToLogicalChildren(_itemsView);
+                RaisePropertyChanged(ItemsViewProperty, oldValue, _itemsView);
+            }
+        }
+
         private protected bool WrapFocus { get; set; }
 
         event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexChanged
@@ -192,7 +217,7 @@ event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexCh
         /// </returns>
         public Control? ContainerFromItem(object item)
         {
-            var index = Items?.IndexOf(item) ?? -1;
+            var index = ItemsView.IndexOf(item);
             return index >= 0 ? ContainerFromIndex(index) : null;
         }
 
@@ -216,7 +241,7 @@ event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexCh
         public object? ItemFromContainer(Control container)
         {
             var index = IndexFromContainer(container);
-            return index >= 0 && index < ItemCount ? Items!.ElementAt(index) : null;
+            return index >= 0 && index < ItemsView.Count ? ItemsView[index] : null;
         }
 
         /// <summary>
@@ -231,37 +256,6 @@ void IItemsPresenterHost.RegisterItemsPresenter(ItemsPresenter presenter)
             _childIndexChanged?.Invoke(this, ChildIndexChangedEventArgs.Empty);
         }
 
-        void ICollectionChangedListener.PreChanged(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
-        {
-        }
-
-        void ICollectionChangedListener.Changed(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
-        {
-        }
-
-        void ICollectionChangedListener.PostChanged(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
-        {
-            ItemsCollectionChanged(sender, e);
-        }
-
-        /// <summary>
-        /// Gets the item at the specified index in a collection.
-        /// </summary>
-        /// <param name="items">The collection.</param>
-        /// <param name="index">The index.</param>
-        /// <returns>The item at the given index or null if the index is out of bounds.</returns>
-        protected static object? ElementAt(IEnumerable? items, int index)
-        {
-            if (index != -1 && index < items.Count())
-            {
-                return items!.ElementAt(index) ?? null;
-            }
-            else
-            {
-                return null;
-            }
-        }
-
         /// <summary>
         /// Creates or a container that can be used to display an item.
         /// </summary>
@@ -350,41 +344,6 @@ protected internal virtual void ClearContainerForItemOverride(Control container)
             // the WPF source it seems that this isn't done there.
         }
 
-        /// <summary>
-        /// Gets the index of an item in a collection.
-        /// </summary>
-        /// <param name="items">The collection.</param>
-        /// <param name="item">The item.</param>
-        /// <returns>The index of the item or -1 if the item was not found.</returns>
-        protected static int IndexOf(IEnumerable? items, object item)
-        {
-            if (items != null && item != null)
-            {
-                var list = items as IList;
-
-                if (list != null)
-                {
-                    return list.IndexOf(item);
-                }
-                else
-                {
-                    int index = 0;
-
-                    foreach (var i in items)
-                    {
-                        if (Equals(i, item))
-                        {
-                            return index;
-                        }
-
-                        ++index;
-                    }
-                }
-            }
-
-            return -1;
-        }
-
         /// <summary>
         /// Determines whether the specified item is (or is eligible to be) its own container.
         /// </summary>
@@ -445,7 +404,12 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
         {
             base.OnPropertyChanged(change);
 
-            if (change.Property == ItemCountProperty)
+            if (change.Property == ItemsProperty)
+            {
+                ItemsView = ItemsSourceView.GetOrCreate(change.GetNewValue<IEnumerable?>());
+                ItemCount = ItemsView.Count;
+            }
+            else if (change.Property == ItemCountProperty)
             {
                 UpdatePseudoClasses(change.GetNewValue<int>());
             }
@@ -468,26 +432,6 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
             }
         }
 
-        /// <summary>
-        /// Called when the <see cref="Items"/> property changes.
-        /// </summary>
-        /// <param name="e">The event args.</param>
-        protected virtual void ItemsChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            var oldValue = e.OldValue as IEnumerable;
-            var newValue = e.NewValue as IEnumerable;
-
-            if (oldValue is INotifyCollectionChanged incc)
-            {
-                CollectionChangedEventManager.Instance.RemoveListener(incc, this);
-            }
-
-            UpdateItemCount();
-            RemoveControlItemsFromLogicalChildren(oldValue);
-            AddControlItemsToLogicalChildren(newValue);
-            SubscribeToItems(newValue);
-        }
-
         /// <summary>
         /// Refreshes the containers displayed by the control.
         /// </summary>
@@ -502,9 +446,9 @@ protected virtual void ItemsChanged(AvaloniaPropertyChangedEventArgs e)
         /// </summary>
         /// <param name="sender">The event sender.</param>
         /// <param name="e">The event args.</param>
-        protected virtual void ItemsCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+        protected virtual void ItemsCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
         {
-            UpdateItemCount();
+            ItemCount = _itemsView.Count;
 
             switch (e.Action)
             {
@@ -576,22 +520,22 @@ internal void ItemContainerIndexChanged(Control container, int oldIndex, int new
         /// <param name="items">The items.</param>
         private void AddControlItemsToLogicalChildren(IEnumerable? items)
         {
-            var toAdd = new List<ILogical>();
+            if (items is null)
+                return;
 
-            if (items != null)
+            List<ILogical>? toAdd = null;
+
+            foreach (var i in items)
             {
-                foreach (var i in items)
+                if (i is Control control && !LogicalChildren.Contains(control))
                 {
-                    var control = i as Control;
-
-                    if (control != null && !LogicalChildren.Contains(control))
-                    {
-                        toAdd.Add(control);
-                    }
+                    toAdd ??= new();
+                    toAdd.Add(control);
                 }
             }
 
-            LogicalChildren.AddRange(toAdd);
+            if (toAdd is not null)
+                LogicalChildren.AddRange(toAdd);
         }
 
         /// <summary>
@@ -600,34 +544,22 @@ private void AddControlItemsToLogicalChildren(IEnumerable? items)
         /// <param name="items">The items.</param>
         private void RemoveControlItemsFromLogicalChildren(IEnumerable? items)
         {
-            var toRemove = new List<ILogical>();
+            if (items is null)
+                return;
 
-            if (items != null)
+            List<ILogical>? toRemove = null;
+
+            foreach (var i in items)
             {
-                foreach (var i in items)
+                if (i is Control control)
                 {
-                    var control = i as Control;
-
-                    if (control != null)
-                    {
-                        toRemove.Add(control);
-                    }
+                    toRemove ??= new();
+                    toRemove.Add(control);
                 }
             }
 
-            LogicalChildren.RemoveAll(toRemove);
-        }
-
-        /// <summary>
-        /// Subscribes to an <see cref="Items"/> collection.
-        /// </summary>
-        /// <param name="items">The items collection.</param>
-        private void SubscribeToItems(IEnumerable? items)
-        {
-            if (items is INotifyCollectionChanged incc)
-            {
-                CollectionChangedEventManager.Instance.AddListener(incc, this);
-            }
+            if (toRemove is not null)
+                LogicalChildren.RemoveAll(toRemove);
         }
 
         private IDataTemplate? GetEffectiveItemTemplate()
@@ -647,22 +579,6 @@ private void SubscribeToItems(IEnumerable? items)
             return _displayMemberItemTemplate;
         }
 
-        private void UpdateItemCount()
-        {
-            if (Items == null)
-            {
-                ItemCount = 0;
-            }
-            else if (Items is IList list)
-            {
-                ItemCount = list.Count;
-            }
-            else
-            {
-                ItemCount = Items.Count();
-            }
-        }
-
         private void UpdatePseudoClasses(int itemCount)
         {
             PseudoClasses.Set(":empty", itemCount == 0);
@@ -728,7 +644,8 @@ int IChildIndexProvider.GetChildIndex(ILogical child)
 
         bool IChildIndexProvider.TryGetTotalCount(out int count)
         {
-            return Items.TryGetCountFast(out count);
+            count = ItemsView.Count;
+            return true;
         }
     }
 }
diff --git a/src/Avalonia.Controls/ItemsSourceView.cs b/src/Avalonia.Controls/ItemsSourceView.cs
index 945035ab5e8..27fa7cbe48f 100644
--- a/src/Avalonia.Controls/ItemsSourceView.cs
+++ b/src/Avalonia.Controls/ItemsSourceView.cs
@@ -13,24 +13,22 @@
 namespace Avalonia.Controls
 {
     /// <summary>
-    /// Represents a standardized view of the supported interactions between a given ItemsSource
-    /// object and an <see cref="ItemsRepeater"/> control.
+    /// Represents a standardized view of the supported interactions between an items collection
+    /// and an items control.
     /// </summary>
-    /// <remarks>
-    /// Components written to work with ItemsRepeater should consume the
-    /// <see cref="ItemsRepeater.Items"/> via ItemsSourceView since this provides a normalized
-    /// view of the Items. That way, each component does not need to know if the source is an
-    /// IEnumerable, an IList, or something else.
-    /// </remarks>
-    public class ItemsSourceView : INotifyCollectionChanged, IDisposable
+    public class ItemsSourceView : IReadOnlyList<object?>,
+        INotifyCollectionChanged,
+        ICollectionChangedListener
     {
         /// <summary>
         ///  Gets an empty <see cref="ItemsSourceView"/>
         /// </summary>
         public static ItemsSourceView Empty { get; } = new ItemsSourceView(Array.Empty<object>());
 
-        private IList? _inner;
+        private readonly IList _inner;
         private NotifyCollectionChangedEventHandler? _collectionChanged;
+        private NotifyCollectionChangedEventHandler? _postCollectionChanged;
+        private bool _listening;
 
         /// <summary>
         /// Initializes a new instance of the ItemsSourceView class for the specified data source.
@@ -38,15 +36,15 @@ public class ItemsSourceView : INotifyCollectionChanged, IDisposable
         /// <param name="source">The data source.</param>
         public ItemsSourceView(IEnumerable source)
         {
-            source = source ?? throw new ArgumentNullException(nameof(source));
             _inner = source switch
             {
-                ItemsSourceView _ => throw new ArgumentException("Cannot wrap an existing ItemsSourceView.", nameof(source)),
+                ItemsSourceView => throw new ArgumentException("Cannot wrap an existing ItemsSourceView.", nameof(source)),
                 IList list => list,
-                INotifyCollectionChanged _ => throw new ArgumentException(
-                    "Collection implements INotifyCollectionChanged by not IList.",
+                INotifyCollectionChanged => throw new ArgumentException(
+                    "Collection implements INotifyCollectionChanged but not IList.",
                     nameof(source)),
                 IEnumerable<object> iObj => new List<object>(iObj),
+                null => throw new ArgumentNullException(nameof(source)),
                 _ => new List<object>(source.Cast<object>())
             };
         }
@@ -56,26 +54,10 @@ public ItemsSourceView(IEnumerable source)
         /// </summary>
         public int Count => Inner.Count;
 
-        /// <summary>
-        /// Gets a value that indicates whether the items source can provide a unique key for each item.
-        /// </summary>
-        /// <remarks>
-        /// TODO: Not yet implemented in Avalonia.
-        /// </remarks>
-        public bool HasKeyIndexMapping => false;
-
         /// <summary>
         /// Gets the inner collection.
         /// </summary>
-        public IList Inner
-        {
-            get
-            {
-                if (_inner is null)
-                    ThrowDisposed();
-                return _inner!;
-            }
-        }
+        public IList Inner => _inner;
 
         /// <summary>
         /// Retrieves the item at the specified index.
@@ -84,6 +66,14 @@ public IList Inner
         /// <returns>The item.</returns>
         public object? this[int index] => GetAt(index);
 
+        /// <summary>
+        /// Gets a value that indicates whether the items source can provide a unique key for each item.
+        /// </summary>
+        /// <remarks>
+        /// TODO: Not yet implemented in Avalonia.
+        /// </remarks>
+        internal bool HasKeyIndexMapping => false;
+
         /// <summary>
         /// Occurs when the collection has changed to indicate the reason for the change and which items changed.
         /// </summary>
@@ -91,114 +81,133 @@ public event NotifyCollectionChangedEventHandler? CollectionChanged
         {
             add
             {
-                if (_collectionChanged is null && Inner is INotifyCollectionChanged incc)
-                {
-                    incc.CollectionChanged += OnCollectionChanged;
-                }
-
+                AddListenerIfNecessary();
                 _collectionChanged += value;
             }
 
             remove
             {
                 _collectionChanged -= value;
-
-                if (_collectionChanged is null && Inner is INotifyCollectionChanged incc)
-                {
-                    incc.CollectionChanged -= OnCollectionChanged;
-                }
+                RemoveListenerIfNecessary();
             }
         }
 
-        /// <inheritdoc/>
-        public void Dispose()
+        /// <summary>
+        /// Occurs when a collection has finished changing and all <see cref="CollectionChanged"/>
+        /// event handlers have been notified.
+        /// </summary>
+        internal event NotifyCollectionChangedEventHandler? PostCollectionChanged
         {
-            if (_inner is INotifyCollectionChanged incc)
+            add
             {
-                incc.CollectionChanged -= OnCollectionChanged;
+                AddListenerIfNecessary();
+                _postCollectionChanged += value;
             }
 
-            _inner = null;
+            remove
+            {
+                _postCollectionChanged -= value;
+                RemoveListenerIfNecessary();
+            }
         }
 
-        /// <summary>
-        /// Retrieves the item at the specified index.
-        /// </summary>
-        /// <param name="index">The index.</param>
-        /// <returns>The item.</returns>
-        public object? GetAt(int index) => Inner[index];
-
-        public int IndexOf(object? item) => Inner.IndexOf(item);
-
-        public static ItemsSourceView GetOrCreate(IEnumerable? items)
+        private void AddListenerIfNecessary()
         {
-            if (items is ItemsSourceView isv)
+            if (!_listening)
             {
-                return isv;
+                if (_inner is INotifyCollectionChanged incc)
+                    CollectionChangedEventManager.Instance.AddListener(incc, this);
+                _listening = true;
             }
-            else if (items is null)
-            {
-                return Empty;
-            }
-            else
+        }
+
+        private void RemoveListenerIfNecessary()
+        {
+            if (_listening && _collectionChanged is null && _postCollectionChanged is null)
             {
-                return new ItemsSourceView(items);
+                if (_inner is INotifyCollectionChanged incc)
+                    CollectionChangedEventManager.Instance.RemoveListener(incc, this);
+                _listening = false;
             }
         }
 
         /// <summary>
-        /// Retrieves the index of the item that has the specified unique identifier (key).
+        /// Retrieves the item at the specified index.
         /// </summary>
         /// <param name="index">The index.</param>
-        /// <returns>The key</returns>
-        /// <remarks>
-        /// TODO: Not yet implemented in Avalonia.
-        /// </remarks>
-        public string KeyFromIndex(int index)
-        {
-            throw new NotImplementedException();
-        }
+        /// <returns>The item.</returns>
+        public object? GetAt(int index) => Inner[index];
+
+        /// <summary>
+        /// Determines the index of a specific item in the collection.
+        /// </summary>
+        /// <param name="item">The object to locate in the collection.</param>
+        /// <returns>The index of value if found in the list; otherwise, -1.</returns>
+        public int IndexOf(object? item) => Inner.IndexOf(item);
 
         /// <summary>
-        /// Retrieves the unique identifier (key) for the item at the specified index.
+        /// Gets or creates an <see cref="ItemsSourceView"/> for the specified enumerable.
         /// </summary>
-        /// <param name="key">The key.</param>
-        /// <returns>The index.</returns>
+        /// <param name="items">The enumerable.</param>
         /// <remarks>
-        /// TODO: Not yet implemented in Avalonia.
+        /// This method handles the following three cases:
+        /// - If <paramref name="items"/> is null, returns <see cref="Empty"/>
+        /// - If <paramref name="items"/> is an <see cref="ItemsSourceView"/> returns the existing
+        ///   <see cref="ItemsSourceView"/>
+        /// - Otherwise creates a new <see cref="ItemsSourceView"/>
         /// </remarks>
-        public int IndexFromKey(string key)
+        public static ItemsSourceView GetOrCreate(IEnumerable? items)
         {
-            throw new NotImplementedException();
+            return items switch
+            {
+                ItemsSourceView isv => isv,
+                null => Empty,
+                _ => new ItemsSourceView(items)
+            };
         }
 
-        internal void AddListener(ICollectionChangedListener listener)
+        public IEnumerator<object?> GetEnumerator()
         {
-            if (Inner is INotifyCollectionChanged incc)
+            static IEnumerator<object> EnumerateItems(IList list)
             {
-                CollectionChangedEventManager.Instance.AddListener(incc, listener);
+                foreach (var o in list)
+                    yield return o;
             }
+
+            var inner = Inner;
+
+            return inner switch
+            {
+                IEnumerable<object> e => e.GetEnumerator(),
+                _ => EnumerateItems(inner),
+            };
         }
 
-        internal void RemoveListener(ICollectionChangedListener listener)
+        IEnumerator IEnumerable.GetEnumerator() => Inner.GetEnumerator();
+
+        void ICollectionChangedListener.PreChanged(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
         {
-            if (Inner is INotifyCollectionChanged incc)
-            {
-                CollectionChangedEventManager.Instance.RemoveListener(incc, listener);
-            }
         }
 
-        protected void OnItemsSourceChanged(NotifyCollectionChangedEventArgs args)
+        void ICollectionChangedListener.Changed(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
         {
-            _collectionChanged?.Invoke(this, args);
+            _collectionChanged?.Invoke(this, e);
         }
 
-        private void OnCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
+        void ICollectionChangedListener.PostChanged(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
         {
-            OnItemsSourceChanged(e);
+            _postCollectionChanged?.Invoke(this, e);
         }
 
-        private void ThrowDisposed() => throw new ObjectDisposedException(nameof(ItemsSourceView));
+        /// <summary>
+        /// Retrieves the index of the item that has the specified unique identifier (key).
+        /// </summary>
+        /// <param name="index">The index.</param>
+        /// <returns>The key</returns>
+        /// <remarks>
+        /// TODO: Not yet implemented in Avalonia.
+        /// </remarks>
+        internal string KeyFromIndex(int index) => throw new NotImplementedException();
     }
 
     public class ItemsSourceView<T> : ItemsSourceView, IReadOnlyList<T>
@@ -227,9 +236,7 @@ private ItemsSourceView(IEnumerable source)
         /// </summary>
         /// <param name="index">The index.</param>
         /// <returns>The item.</returns>
-#pragma warning disable CS8603
         public new T this[int index] => GetAt(index);
-#pragma warning restore CS8603
 
         /// <summary>
         /// Retrieves the item at the specified index.
@@ -238,23 +245,44 @@ private ItemsSourceView(IEnumerable source)
         /// <returns>The item.</returns>
         public new T GetAt(int index) => (T)Inner[index]!;
 
-        public IEnumerator<T> GetEnumerator() => Inner.Cast<T>().GetEnumerator();
-        IEnumerator IEnumerable.GetEnumerator() => Inner.GetEnumerator();
-
-        public static new ItemsSourceView<T> GetOrCreate(IEnumerable? items)
+        public new IEnumerator<T> GetEnumerator()
         {
-            if (items is ItemsSourceView<T> isv)
+            static IEnumerator<T> EnumerateItems(IList list)
             {
-                return isv;
+                foreach (var o in list)
+                    yield return (T)o;
             }
-            else if (items is null)
+
+            var inner = Inner;
+
+            return inner switch
             {
-                return Empty;
-            }
-            else
+                IEnumerable<T> e => e.GetEnumerator(),
+                _ => EnumerateItems(inner),
+            };
+        }
+
+        IEnumerator IEnumerable.GetEnumerator() => Inner.GetEnumerator();
+
+        /// <summary>
+        /// Gets or creates an <see cref="ItemsSourceView{T}"/> for the specified enumerable.
+        /// </summary>
+        /// <param name="items">The enumerable.</param>
+        /// <remarks>
+        /// This method handles the following three cases:
+        /// - If <paramref name="items"/> is null, returns <see cref="Empty"/>
+        /// - If <paramref name="items"/> is an <see cref="ItemsSourceView"/> returns the existing
+        ///   <see cref="ItemsSourceView"/>
+        /// - Otherwise creates a new <see cref="ItemsSourceView"/>
+        /// </remarks>
+        public static new ItemsSourceView<T> GetOrCreate(IEnumerable? items)
+        {
+            return items switch
             {
-                return new ItemsSourceView<T>(items);
-            }
+                ItemsSourceView<T> isv => isv,
+                null => Empty,
+                _ => new ItemsSourceView<T>(items)
+            };
         }
     }
 }
diff --git a/src/Avalonia.Controls/MenuItem.cs b/src/Avalonia.Controls/MenuItem.cs
index dd336974ca2..594a1c0f628 100644
--- a/src/Avalonia.Controls/MenuItem.cs
+++ b/src/Avalonia.Controls/MenuItem.cs
@@ -659,7 +659,7 @@ private void SubMenuOpenChanged(AvaloniaPropertyChangedEventArgs e)
 
             if (value)
             {
-                foreach (var item in Items!.OfType<MenuItem>())
+                foreach (var item in ItemsView.OfType<MenuItem>())
                 {
                     item.TryUpdateCanExecute();
                 }
diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index 8d1e7f0b96a..9b38c261e7a 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -23,9 +23,7 @@ public PanelContainerGenerator(ItemsPresenter presenter)
             
             _presenter = presenter;
             _presenter.ItemsControl.PropertyChanged += OnItemsControlPropertyChanged;
-
-            if (_presenter.ItemsControl.Items is INotifyCollectionChanged incc)
-                incc.CollectionChanged += OnItemsChanged;
+            _presenter.ItemsControl.ItemsView.PostCollectionChanged += OnItemsChanged;
 
             OnItemsChanged(null, CollectionUtils.ResetEventArgs);
         }
@@ -35,9 +33,7 @@ public void Dispose()
             if (_presenter.ItemsControl is { } itemsControl)
             {
                 itemsControl.PropertyChanged -= OnItemsControlPropertyChanged;
-
-                if (itemsControl.Items is INotifyCollectionChanged incc)
-                    incc.CollectionChanged -= OnItemsChanged;
+                itemsControl.ItemsView.PostCollectionChanged -= OnItemsChanged;
 
                 ClearItemsControlLogicalChildren();
             }
@@ -117,8 +113,7 @@ void Remove(int index, int count)
                 case NotifyCollectionChangedAction.Reset:
                     ClearItemsControlLogicalChildren();
                     children.Clear();
-                    if (_presenter.ItemsControl?.Items is { } items)
-                        Add(0, items);
+                    Add(0, _presenter.ItemsControl.ItemsView);
                     break;
             }
         }
diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index 253726c5aaa..bc304e24e71 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -380,7 +380,7 @@ public override void EndInit()
         /// Scrolls the specified item into view.
         /// </summary>
         /// <param name="item">The item.</param>
-        public void ScrollIntoView(object item) => ScrollIntoView(IndexOf(Items, item));
+        public void ScrollIntoView(object item) => ScrollIntoView(ItemsView.IndexOf(item));
 
         /// <summary>
         /// Tries to get the container that was the source of an event.
diff --git a/src/Avalonia.Controls/Repeater/ItemsRepeater.cs b/src/Avalonia.Controls/Repeater/ItemsRepeater.cs
index 41a0dc384f9..b82637b6677 100644
--- a/src/Avalonia.Controls/Repeater/ItemsRepeater.cs
+++ b/src/Avalonia.Controls/Repeater/ItemsRepeater.cs
@@ -628,7 +628,6 @@ private void OnDataSourcePropertyChanged(ItemsSourceView? oldValue, ItemsSourceV
                 oldValue.CollectionChanged -= OnItemsSourceViewChanged;
             }
 
-            ItemsSourceView?.Dispose();
             ItemsSourceView = newValue;
 
             if (newValue != null)
diff --git a/src/Avalonia.Controls/Selection/SelectionNodeBase.cs b/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
index 33a5525acc8..c5a1a6a7cee 100644
--- a/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
+++ b/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
@@ -21,10 +21,12 @@ protected IEnumerable? Source
             {
                 if (_source != value)
                 {
-                    ItemsView?.RemoveListener(this);
+                    if (ItemsView?.Inner is INotifyCollectionChanged inccOld)
+                        CollectionChangedEventManager.Instance.RemoveListener(inccOld, this);
                     _source = value;
                     ItemsView = value is object ? ItemsSourceView<T>.GetOrCreate(value) : null;
-                    ItemsView?.AddListener(this);
+                    if (ItemsView?.Inner is INotifyCollectionChanged inccNew)
+                        CollectionChangedEventManager.Instance.AddListener(inccNew, this);
                 }
             }
         }
diff --git a/src/Avalonia.Controls/TreeView.cs b/src/Avalonia.Controls/TreeView.cs
index 0c0de9d544c..90e8a608288 100644
--- a/src/Avalonia.Controls/TreeView.cs
+++ b/src/Avalonia.Controls/TreeView.cs
@@ -192,11 +192,8 @@ public void SelectAll()
 
             void AddItems(ItemsControl itemsControl)
             {
-                if (itemsControl.Items is { } items)
-                {
-                    foreach (var item in items)
-                        allItems.Add(item);
-                }
+                foreach (var item in itemsControl.ItemsView)
+                    allItems.Add(item!);
 
                 foreach (var child in itemsControl.GetRealizedContainers())
                 {
@@ -513,7 +510,7 @@ protected override void OnKeyDown(KeyEventArgs e)
                 }
                 else
                 {
-                    SelectedItem = ElementAt(Items, 0);
+                    SelectedItem = ItemsView[0];
                 }
             }
 
diff --git a/src/Avalonia.Controls/TreeViewItem.cs b/src/Avalonia.Controls/TreeViewItem.cs
index 6081fef4e65..538e91053fa 100644
--- a/src/Avalonia.Controls/TreeViewItem.cs
+++ b/src/Avalonia.Controls/TreeViewItem.cs
@@ -150,7 +150,7 @@ protected override void OnKeyDown(KeyEventArgs e)
                 switch (e.Key)
                 {
                     case Key.Right:
-                        if (Items != null && Items.Cast<object>().Any() && !IsExpanded)
+                        if (ItemsView.Count > 0 && !IsExpanded)
                         {
                             IsExpanded = true;
                             e.Handled = true;
@@ -158,7 +158,7 @@ protected override void OnKeyDown(KeyEventArgs e)
                         break;
 
                     case Key.Left:
-                        if (Items is not null && Items.Cast<object>().Any() && IsExpanded)
+                        if (ItemsView.Count > 0 && IsExpanded)
                         {
                             if (IsFocused)
                             {
diff --git a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
index 7ea175fc184..d21959ff8bd 100644
--- a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
@@ -95,7 +95,7 @@ bool ILogicalScrollable.BringIntoView(Control target, Rect targetRect)
 
         protected override Size MeasureOverride(Size availableSize)
         {
-            var items = ItemsControl?.Items as IList ?? Array.Empty<object?>();
+            var items = ItemsControl?.ItemsView ?? ItemsSourceView.Empty;
             var index = (int)_offset.X;
 
             if (index != _realizedIndex)
@@ -195,7 +195,7 @@ protected internal override int IndexFromContainer(Control container)
             return null;
         }
 
-        protected override void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
+        protected override void OnItemsChanged(IReadOnlyList<object?> items, NotifyCollectionChangedEventArgs e)
         {
             base.OnItemsChanged(items, e);
 
@@ -247,7 +247,7 @@ void Remove(int index, int count)
             InvalidateMeasure();
         }
 
-        private Control GetOrCreateElement(IList items, int index)
+        private Control GetOrCreateElement(ItemsSourceView items, int index)
         {
             return GetRealizedElement(index) ??
                 GetItemIsOwnContainer(items, index) ??
@@ -260,7 +260,7 @@ private Control GetOrCreateElement(IList items, int index)
             return _realizedIndex == index ? _realized : null;
         }
 
-        private Control? GetItemIsOwnContainer(IList items, int index)
+        private Control? GetItemIsOwnContainer(ItemsSourceView items, int index)
         {
             Debug.Assert(ItemsControl is not null);
 
@@ -285,7 +285,7 @@ private Control GetOrCreateElement(IList items, int index)
             return null;
         }
 
-        private Control? GetRecycledElement(IList items, int index)
+        private Control? GetRecycledElement(ItemsSourceView items, int index)
         {
             Debug.Assert(ItemsControl is not null);
 
@@ -303,7 +303,7 @@ private Control GetOrCreateElement(IList items, int index)
             return null;
         }
 
-        private Control CreateElement(IList items, int index)
+        private Control CreateElement(ItemsSourceView items, int index)
         {
             Debug.Assert(ItemsControl is not null);
 
diff --git a/src/Avalonia.Controls/VirtualizingPanel.cs b/src/Avalonia.Controls/VirtualizingPanel.cs
index 0d0abe148da..59146656e63 100644
--- a/src/Avalonia.Controls/VirtualizingPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingPanel.cs
@@ -99,7 +99,7 @@ protected virtual void OnItemsControlChanged(ItemsControl? oldValue)
         /// new collection, in which case the <see cref="NotifyCollectionChangedAction"/> will
         /// be <see cref="NotifyCollectionChangedAction.Reset"/>.
         /// </remarks>
-        protected virtual void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
+        protected virtual void OnItemsChanged(IReadOnlyList<object?> items, NotifyCollectionChangedEventArgs e)
         {
         }
 
@@ -158,9 +158,7 @@ internal void Attach(ItemsControl itemsControl)
 
             ItemsControl = itemsControl;
             ItemsControl.PropertyChanged += OnItemsControlPropertyChanged;
-
-            if (ItemsControl.Items is INotifyCollectionChanged incc)
-                incc.CollectionChanged += OnItemsControlItemsChanged;
+            ItemsControl.ItemsView.PostCollectionChanged += OnItemsControlItemsChanged;
         }
 
         internal void Detach()
@@ -168,9 +166,7 @@ internal void Detach()
             var itemsControl = EnsureItemsControl();
 
             itemsControl.PropertyChanged -= OnItemsControlPropertyChanged;
-
-            if (itemsControl.Items is INotifyCollectionChanged incc)
-                incc.CollectionChanged -= OnItemsControlItemsChanged;
+            itemsControl.ItemsView.PostCollectionChanged -= OnItemsControlItemsChanged;
 
             ItemsControl = null;
             Children.Clear();
@@ -187,20 +183,18 @@ private ItemsControl EnsureItemsControl()
 
         private protected virtual void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
         {
-            if (e.Property == ItemsControl.ItemsProperty)
+            if (e.Property == ItemsControl.ItemsViewProperty)
             {
-                if (e.OldValue is INotifyCollectionChanged inccOld)
-                    inccOld.CollectionChanged -= OnItemsControlItemsChanged;
+                var (oldValue, newValue) = e.GetOldAndNewValue<ItemsSourceView>();
+                oldValue.PostCollectionChanged -= OnItemsControlItemsChanged;
                 Refresh();
-                if (e.NewValue is INotifyCollectionChanged inccNew)
-                    inccNew.CollectionChanged += OnItemsControlItemsChanged;
+                newValue.PostCollectionChanged += OnItemsControlItemsChanged;
             }
         }
 
         private void OnItemsControlItemsChanged(object? sender, NotifyCollectionChangedEventArgs e)
         {
-            if (_itemsControl?.Items is IList items)
-                OnItemsChanged(items, e);
+            OnItemsChanged(_itemsControl?.ItemsView ?? ItemsSourceView.Empty, e);
         }
 
         [DoesNotReturn]
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 22526fa29c1..8f423721797 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -1,5 +1,4 @@
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Diagnostics;
@@ -65,7 +64,7 @@ protected override Size MeasureOverride(Size availableSize)
 
             try
             {
-                var items = ItemsControl?.Items as IList;
+                var items = ItemsControl?.ItemsView;
 
                 if (items is null || items.Count == 0)
                 {
@@ -149,7 +148,7 @@ protected override Size ArrangeOverride(Size finalSize)
             }
         }
 
-        protected override void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
+        protected override void OnItemsChanged(IReadOnlyList<object?> items, NotifyCollectionChangedEventArgs e)
         {
             if (_realizedElements is null)
                 return;
@@ -172,7 +171,7 @@ protected override void OnItemsChanged(IList items, NotifyCollectionChangedEvent
 
         protected override IInputElement? GetControl(NavigationDirection direction, IInputElement? from, bool wrap)
         {
-            var count = (ItemsControl?.Items as IList)?.Count ?? 0;
+            var count = ItemsControl?.ItemsView.Count ?? 0;
 
             if (count == 0 || from is not Control fromControl)
                 return null;
@@ -239,7 +238,7 @@ protected override void OnItemsChanged(IList items, NotifyCollectionChangedEvent
 
         protected internal override Control? ScrollIntoView(int index)
         {
-            var items = ItemsControl?.Items as IList;
+            var items = ItemsControl?.ItemsView;
 
             if (_isInLayout || items is null || index < 0 || index >= items.Count)
                 return null;
@@ -296,7 +295,7 @@ protected override void OnItemsChanged(IList items, NotifyCollectionChangedEvent
             return _realizedElements?.Elements ?? Array.Empty<Control>();
         }
 
-        private MeasureViewport CalculateMeasureViewport(IList items)
+        private MeasureViewport CalculateMeasureViewport(ItemsSourceView items)
         {
             Debug.Assert(_realizedElements is not null);
 
@@ -337,7 +336,7 @@ private MeasureViewport CalculateMeasureViewport(IList items)
             };
         }
 
-        private Size CalculateDesiredSize(Orientation orientation, IList items, double sizeV)
+        private Size CalculateDesiredSize(Orientation orientation, ItemsSourceView items, double sizeV)
         {
             var sizeU = EstimateElementSizeU() * items.Count;
 
@@ -402,10 +401,10 @@ private Rect EstimateViewport()
 
         private void GenerateElements(Size availableSize, ref MeasureViewport viewport)
         {
-            Debug.Assert(ItemsControl?.Items is IList);
+            Debug.Assert(ItemsControl is not null);
             Debug.Assert(_measureElements is not null);
 
-            var items = (IList)ItemsControl!.Items;
+            var items = ItemsControl!.ItemsView;
             var horizontal = Orientation == Orientation.Horizontal;
             var index = viewport.firstIndex;
             var u = viewport.startU;
@@ -426,7 +425,7 @@ private void GenerateElements(Size availableSize, ref MeasureViewport viewport)
             } while (u < viewport.viewportUEnd && index < items.Count);
         }
 
-        private Control GetOrCreateElement(IList items, int index)
+        private Control GetOrCreateElement(ItemsSourceView items, int index)
         {
             var e = GetRealizedElement(index) ??
                 GetItemIsOwnContainer(items, index) ??
@@ -443,7 +442,7 @@ private Control GetOrCreateElement(IList items, int index)
             return _realizedElements?.GetElement(index);
         }
 
-        private Control? GetItemIsOwnContainer(IList items, int index)
+        private Control? GetItemIsOwnContainer(ItemsSourceView items, int index)
         {
             if (items[index] is Control controlItem)
             {
@@ -466,7 +465,7 @@ private Control GetOrCreateElement(IList items, int index)
             return null;
         }
 
-        private Control? GetRecycledElement(IList items, int index)
+        private Control? GetRecycledElement(ItemsSourceView items, int index)
         {
             Debug.Assert(ItemsControl is not null);
 
@@ -485,7 +484,7 @@ private Control GetOrCreateElement(IList items, int index)
             return null;
         }
 
-        private Control CreateElement(IList items, int index)
+        private Control CreateElement(ItemsSourceView items, int index)
         {
             Debug.Assert(ItemsControl is not null);
 

From b678339b5dab399489e82f9d288e7473eb16e6ae Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 14:47:17 +0100
Subject: [PATCH 38/64] TreeNodeCollection needs to implement IList now.

---
 .../ViewModels/TreeNodeCollection.cs          | 21 ++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs
index 953afa280bd..0988fd2891f 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs
@@ -8,7 +8,7 @@
 
 namespace Avalonia.Diagnostics.ViewModels
 {
-    internal abstract class TreeNodeCollection : IAvaloniaReadOnlyList<TreeNode>, IDisposable
+    internal abstract class TreeNodeCollection : IAvaloniaReadOnlyList<TreeNode>, IList, IDisposable
     {
         private class EmptyTreeNodeCollection : TreeNodeCollection
         {
@@ -33,6 +33,16 @@ protected override void Initialize(AvaloniaList<TreeNode> nodes)
         public int Count => EnsureInitialized().Count;
 
         protected TreeNode Owner { get; }
+        bool IList.IsFixedSize => false;
+        bool IList.IsReadOnly => true;
+        bool ICollection.IsSynchronized => false;
+        object ICollection.SyncRoot => this;
+
+        object? IList.this[int index] 
+        {
+            get => this[index];
+            set => throw new NotImplementedException();
+        }
 
         public event NotifyCollectionChangedEventHandler? CollectionChanged
         {
@@ -75,5 +85,14 @@ private AvaloniaList<TreeNode> EnsureInitialized()
             }
             return _inner;
         }
+
+        int IList.Add(object? value) => throw new NotImplementedException();
+        void IList.Clear() => throw new NotImplementedException();
+        bool IList.Contains(object? value) => throw new NotImplementedException();
+        int IList.IndexOf(object? value) => throw new NotImplementedException();
+        void IList.Insert(int index, object? value) => throw new NotImplementedException();
+        void IList.Remove(object? value) => throw new NotImplementedException();
+        void IList.RemoveAt(int index) => throw new NotImplementedException();
+        void ICollection.CopyTo(Array array, int index) => throw new NotImplementedException();
     }
 }

From 518391b37db2ff1e442f5369a4f2c789039924c2 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 14:48:41 +0100
Subject: [PATCH 39/64] Make ItemsSourceView ctors private.

So in future we could have different `ItemSourceView` concrete implementations that e.g. have an inner `IReadOnlyList<T>` in order to address #8764.
---
 src/Avalonia.Controls/ItemsControl.cs         |  2 +-
 src/Avalonia.Controls/ItemsSourceView.cs      | 71 ++++++++++++-------
 .../Repeater/ItemsRepeater.cs                 |  2 +-
 .../Selection/SelectionNodeBase.cs            |  2 +-
 .../ItemsSourceViewTests.cs                   | 11 +--
 5 files changed, 51 insertions(+), 37 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index b797ae82951..f8aa38670f4 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -96,7 +96,7 @@ public IBinding? DisplayMemberBinding
         /// </summary>
         public ItemsControl()
         {
-            _itemsView = new(_items);
+            _itemsView = ItemsSourceView.GetOrCreate(_items);
             _itemsView.PostCollectionChanged += ItemsCollectionChanged;
             UpdatePseudoClasses(0);
         }
diff --git a/src/Avalonia.Controls/ItemsSourceView.cs b/src/Avalonia.Controls/ItemsSourceView.cs
index 27fa7cbe48f..c8fc76255c9 100644
--- a/src/Avalonia.Controls/ItemsSourceView.cs
+++ b/src/Avalonia.Controls/ItemsSourceView.cs
@@ -34,7 +34,7 @@ public class ItemsSourceView : IReadOnlyList<object?>,
         /// Initializes a new instance of the ItemsSourceView class for the specified data source.
         /// </summary>
         /// <param name="source">The data source.</param>
-        public ItemsSourceView(IEnumerable source)
+        private protected ItemsSourceView(IEnumerable source)
         {
             _inner = source switch
             {
@@ -166,6 +166,48 @@ public static ItemsSourceView GetOrCreate(IEnumerable? items)
             };
         }
 
+        /// <summary>
+        /// Gets or creates an <see cref="ItemsSourceView{T}"/> for the specified enumerable.
+        /// </summary>
+        /// <param name="items">The enumerable.</param>
+        /// <remarks>
+        /// This method handles the following three cases:
+        /// - If <paramref name="items"/> is null, returns <see cref="Empty"/>
+        /// - If <paramref name="items"/> is an <see cref="ItemsSourceView"/> returns the existing
+        ///   <see cref="ItemsSourceView"/>
+        /// - Otherwise creates a new <see cref="ItemsSourceView"/>
+        /// </remarks>
+        public static ItemsSourceView<T> GetOrCreate<T>(IEnumerable? items)
+        {
+            return items switch
+            {
+                ItemsSourceView<T> isv => isv,
+                null => ItemsSourceView<T>.Empty,
+                _ => new ItemsSourceView<T>(items)
+            };
+        }
+
+        /// <summary>
+        /// Gets or creates an <see cref="ItemsSourceView{T}"/> for the specified enumerable.
+        /// </summary>
+        /// <param name="items">The enumerable.</param>
+        /// <remarks>
+        /// This method handles the following three cases:
+        /// - If <paramref name="items"/> is null, returns <see cref="Empty"/>
+        /// - If <paramref name="items"/> is an <see cref="ItemsSourceView"/> returns the existing
+        ///   <see cref="ItemsSourceView"/>
+        /// - Otherwise creates a new <see cref="ItemsSourceView"/>
+        /// </remarks>
+        public static ItemsSourceView<T> GetOrCreate<T>(IEnumerable<T>? items)
+        {
+            return items switch
+            {
+                ItemsSourceView<T> isv => isv,
+                null => ItemsSourceView<T>.Empty,
+                _ => new ItemsSourceView<T>(items)
+            };
+        }
+
         public IEnumerator<object?> GetEnumerator()
         {
             static IEnumerator<object> EnumerateItems(IList list)
@@ -210,7 +252,7 @@ void ICollectionChangedListener.PostChanged(INotifyCollectionChanged sender, Not
         internal string KeyFromIndex(int index) => throw new NotImplementedException();
     }
 
-    public class ItemsSourceView<T> : ItemsSourceView, IReadOnlyList<T>
+    public sealed class ItemsSourceView<T> : ItemsSourceView, IReadOnlyList<T>
     {
         /// <summary>
         ///  Gets an empty <see cref="ItemsSourceView"/>
@@ -221,12 +263,12 @@ public class ItemsSourceView<T> : ItemsSourceView, IReadOnlyList<T>
         /// Initializes a new instance of the ItemsSourceView class for the specified data source.
         /// </summary>
         /// <param name="source">The data source.</param>
-        public ItemsSourceView(IEnumerable<T> source)
+        internal ItemsSourceView(IEnumerable<T> source)
             : base(source)
         {
         }
 
-        private ItemsSourceView(IEnumerable source)
+        internal ItemsSourceView(IEnumerable source)
             : base(source)
         {
         }
@@ -263,26 +305,5 @@ static IEnumerator<T> EnumerateItems(IList list)
         }
 
         IEnumerator IEnumerable.GetEnumerator() => Inner.GetEnumerator();
-
-        /// <summary>
-        /// Gets or creates an <see cref="ItemsSourceView{T}"/> for the specified enumerable.
-        /// </summary>
-        /// <param name="items">The enumerable.</param>
-        /// <remarks>
-        /// This method handles the following three cases:
-        /// - If <paramref name="items"/> is null, returns <see cref="Empty"/>
-        /// - If <paramref name="items"/> is an <see cref="ItemsSourceView"/> returns the existing
-        ///   <see cref="ItemsSourceView"/>
-        /// - Otherwise creates a new <see cref="ItemsSourceView"/>
-        /// </remarks>
-        public static new ItemsSourceView<T> GetOrCreate(IEnumerable? items)
-        {
-            return items switch
-            {
-                ItemsSourceView<T> isv => isv,
-                null => Empty,
-                _ => new ItemsSourceView<T>(items)
-            };
-        }
     }
 }
diff --git a/src/Avalonia.Controls/Repeater/ItemsRepeater.cs b/src/Avalonia.Controls/Repeater/ItemsRepeater.cs
index b82637b6677..4de6a5188d9 100644
--- a/src/Avalonia.Controls/Repeater/ItemsRepeater.cs
+++ b/src/Avalonia.Controls/Repeater/ItemsRepeater.cs
@@ -442,7 +442,7 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
                     var newDataSource = newEnumerable as ItemsSourceView;
                     if (newEnumerable != null && newDataSource == null)
                     {
-                        newDataSource = new ItemsSourceView(newEnumerable);
+                        newDataSource = ItemsSourceView.GetOrCreate(newEnumerable);
                     }
 
                     OnDataSourcePropertyChanged(ItemsSourceView, newDataSource);
diff --git a/src/Avalonia.Controls/Selection/SelectionNodeBase.cs b/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
index c5a1a6a7cee..01b89325af5 100644
--- a/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
+++ b/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
@@ -24,7 +24,7 @@ protected IEnumerable? Source
                     if (ItemsView?.Inner is INotifyCollectionChanged inccOld)
                         CollectionChangedEventManager.Instance.RemoveListener(inccOld, this);
                     _source = value;
-                    ItemsView = value is object ? ItemsSourceView<T>.GetOrCreate(value) : null;
+                    ItemsView = value is object ? ItemsSourceView.GetOrCreate<T>(value) : null;
                     if (ItemsView?.Inner is INotifyCollectionChanged inccNew)
                         CollectionChangedEventManager.Instance.AddListener(inccNew, this);
                 }
diff --git a/tests/Avalonia.Controls.UnitTests/ItemsSourceViewTests.cs b/tests/Avalonia.Controls.UnitTests/ItemsSourceViewTests.cs
index 22a9b286484..df842b21a71 100644
--- a/tests/Avalonia.Controls.UnitTests/ItemsSourceViewTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ItemsSourceViewTests.cs
@@ -15,7 +15,7 @@ public class ItemsSourceViewTests
         public void Only_Subscribes_To_Source_CollectionChanged_When_CollectionChanged_Subscribed()
         {
             var source = new AvaloniaList<string>();
-            var target = new ItemsSourceView<string>(source);
+            var target = ItemsSourceView.GetOrCreate(source);
             var debug = (INotifyCollectionChangedDebug)source;
 
             Assert.Null(debug.GetCollectionChangedSubscribers());
@@ -31,18 +31,11 @@ void Handler(object sender, NotifyCollectionChangedEventArgs e) { }
             Assert.Null(debug.GetCollectionChangedSubscribers());
         }
 
-        [Fact]
-        public void Cannot_Wrap_An_ItemsSourceView_In_Another()
-        {
-            var source = new ItemsSourceView<string>(new string[0]);
-            Assert.Throws<ArgumentException>(() => new ItemsSourceView<string>(source));
-        }
-
         [Fact]
         public void Cannot_Create_ItemsSourceView_With_Collection_That_Implements_INCC_But_Not_List()
         {
             var source = new InvalidCollection();
-            Assert.Throws<ArgumentException>(() => new ItemsSourceView<string>(source));
+            Assert.Throws<ArgumentException>(() => ItemsSourceView.GetOrCreate(source));
         }
 
         private class InvalidCollection : INotifyCollectionChanged, IEnumerable<string>

From f042127290dcbf6ff1e9de1d903731aff426d1cc Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 15:42:29 +0100
Subject: [PATCH 40/64] Implement a few required members.

---
 .../Diagnostics/ViewModels/TreeNodeCollection.cs              | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs
index 0988fd2891f..77a3697ec1c 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs
@@ -88,8 +88,8 @@ private AvaloniaList<TreeNode> EnsureInitialized()
 
         int IList.Add(object? value) => throw new NotImplementedException();
         void IList.Clear() => throw new NotImplementedException();
-        bool IList.Contains(object? value) => throw new NotImplementedException();
-        int IList.IndexOf(object? value) => throw new NotImplementedException();
+        bool IList.Contains(object? value) => EnsureInitialized().Contains((TreeNode)value!);
+        int IList.IndexOf(object? value) => EnsureInitialized().IndexOf((TreeNode)value!);
         void IList.Insert(int index, object? value) => throw new NotImplementedException();
         void IList.Remove(object? value) => throw new NotImplementedException();
         void IList.RemoveAt(int index) => throw new NotImplementedException();

From d4a8b98b37b71f25fd41d14fd351bee5ddb1a89a Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 15:43:19 +0100
Subject: [PATCH 41/64] Invalidate measure less.

Only invalidate the measure when the viewport changes in the direction of scroll.
---
 src/Avalonia.Controls/VirtualizingStackPanel.cs | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 8f423721797..7e5a00e6f7c 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -528,9 +528,21 @@ private void UpdateElementIndex(Control element, int oldIndex, int newIndex)
 
         private void OnEffectiveViewportChanged(object? sender, EffectiveViewportChangedEventArgs e)
         {
+            var vertical = Orientation == Orientation.Vertical;
+            var oldViewportStart = vertical ? _viewport.Top : _viewport.Left;
+            var oldViewportEnd = vertical ? _viewport.Bottom : _viewport.Right;
+
             _viewport = e.EffectiveViewport;
             _isWaitingForViewportUpdate = false;
-            InvalidateMeasure();
+
+            var newViewportStart = vertical ? _viewport.Top : _viewport.Left;
+            var newViewportEnd = vertical ? _viewport.Bottom : _viewport.Right;
+
+            if (!MathUtilities.AreClose(oldViewportStart, newViewportStart) ||
+                !MathUtilities.AreClose(oldViewportEnd, newViewportEnd))
+            {
+                InvalidateMeasure();
+            }
         }
 
         private static void InvalidateHack(Control c)

From bcb3a6d5ca55e541c19837fc66a9e6727fcdb5fb Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 15:43:55 +0100
Subject: [PATCH 42/64] Fix side panel width.

Variable width was causing the panel to flicker around as the values change.
---
 samples/VirtualizationDemo/MainWindow.xaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/VirtualizationDemo/MainWindow.xaml b/samples/VirtualizationDemo/MainWindow.xaml
index 7748ebcc03e..235f3ef2cc4 100644
--- a/samples/VirtualizationDemo/MainWindow.xaml
+++ b/samples/VirtualizationDemo/MainWindow.xaml
@@ -9,7 +9,7 @@
     <DockPanel LastChildFill="True" Margin="16">
         <StackPanel DockPanel.Dock="Right" 
                     Margin="16 0 0 0" 
-                    MinWidth="150"
+                    Width="150"
                     Spacing="4">
             <ComboBox Items="{Binding Orientations}"
                       SelectedItem="{Binding Orientation}"/>

From 395a90d9207d30f81faa9d01f18ce8e2463c17b8 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 16:11:46 +0100
Subject: [PATCH 43/64] Create containers for remaining ItemsControls.

---
 src/Avalonia.Controls/ComboBox.cs            | 3 +++
 src/Avalonia.Controls/MenuBase.cs            | 3 +++
 src/Avalonia.Controls/MenuItem.cs            | 3 +++
 src/Avalonia.Controls/Primitives/TabStrip.cs | 3 +++
 4 files changed, 12 insertions(+)

diff --git a/src/Avalonia.Controls/ComboBox.cs b/src/Avalonia.Controls/ComboBox.cs
index a573a9d8872..c7ef0d136cd 100644
--- a/src/Avalonia.Controls/ComboBox.cs
+++ b/src/Avalonia.Controls/ComboBox.cs
@@ -170,6 +170,9 @@ public override void InvalidateMirrorTransform()
             UpdateFlowDirection();
         }
 
+        protected internal override Control CreateContainerForItemOverride() => new ComboBoxItem();
+        protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is ComboBoxItem;
+
         /// <inheritdoc/>
         protected override void OnKeyDown(KeyEventArgs e)
         {
diff --git a/src/Avalonia.Controls/MenuBase.cs b/src/Avalonia.Controls/MenuBase.cs
index 3bbd5b7de49..1918964bc89 100644
--- a/src/Avalonia.Controls/MenuBase.cs
+++ b/src/Avalonia.Controls/MenuBase.cs
@@ -133,6 +133,9 @@ public event EventHandler<RoutedEventArgs>? MenuClosed
         /// <inheritdoc/>
         bool IMenuElement.MoveSelection(NavigationDirection direction, bool wrap) => MoveSelection(direction, wrap);
 
+        protected internal override Control CreateContainerForItemOverride() => new MenuItem();
+        protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is MenuItem or Separator;
+
         /// <inheritdoc/>
         protected override void OnKeyDown(KeyEventArgs e)
         {
diff --git a/src/Avalonia.Controls/MenuItem.cs b/src/Avalonia.Controls/MenuItem.cs
index 594a1c0f628..49e423aac8f 100644
--- a/src/Avalonia.Controls/MenuItem.cs
+++ b/src/Avalonia.Controls/MenuItem.cs
@@ -349,6 +349,9 @@ public bool StaysOpenOnClick
         /// <inheritdoc/>
         void IMenuItem.RaiseClick() => RaiseEvent(new RoutedEventArgs(ClickEvent));
 
+        protected internal override Control CreateContainerForItemOverride() => new MenuItem();
+        protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is MenuItem or Separator;
+
         protected override void OnPointerReleased(PointerReleasedEventArgs e)
         {
             base.OnPointerReleased(e);
diff --git a/src/Avalonia.Controls/Primitives/TabStrip.cs b/src/Avalonia.Controls/Primitives/TabStrip.cs
index a6a6f4cec81..b8790d2a44c 100644
--- a/src/Avalonia.Controls/Primitives/TabStrip.cs
+++ b/src/Avalonia.Controls/Primitives/TabStrip.cs
@@ -18,6 +18,9 @@ static TabStrip()
             ItemsPanelProperty.OverrideDefaultValue<TabStrip>(DefaultPanel);
         }
 
+        protected internal override Control CreateContainerForItemOverride() => new TabStripItem();
+        protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is TabStripItem;
+
         /// <inheritdoc/>
         protected override void OnGotFocus(GotFocusEventArgs e)
         {

From 0b3aa3a84bca63c77344a424acbb3a2de7d367a8 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 22:55:08 +0100
Subject: [PATCH 44/64] Prepare new containers before adding to tree.

Prevents compiled bindings failing because the `DataContext` is not yet set and is still inheriting the parent `DataContext`.
---
 src/Avalonia.Controls/ItemsControl.cs                | 12 ++----------
 .../Presenters/PanelContainerGenerator.cs            |  2 +-
 src/Avalonia.Controls/VirtualizingCarouselPanel.cs   |  4 ++--
 3 files changed, 5 insertions(+), 13 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index f8aa38670f4..a082f8cdecc 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -313,9 +313,9 @@ protected internal virtual void PrepareContainerForItemOverride(Control containe
                 hic.Header = item;
                 hic.HeaderTemplate = itemTemplate;
 
-                var treeTemplate = (itemTemplate ?? hic.FindDataTemplate(item)) as ITreeDataTemplate;
+                itemTemplate ??= hic.FindDataTemplate(item) ?? this.FindDataTemplate(item);
 
-                if (treeTemplate is not null)
+                if (itemTemplate is ITreeDataTemplate treeTemplate)
                 {
                     if (item is not null && treeTemplate.ItemsSelector(item) is { } itemsBinding)
                         BindingOperations.Apply(hic, ItemsProperty, itemsBinding, null);
@@ -481,14 +481,6 @@ private protected virtual ItemContainerGenerator CreateItemContainerGenerator()
 
         internal void PrepareItemContainer(Control container, object? item, int index)
         {
-            // Putting this precondition in place in case we want to raise an event when a
-            // container is realized. If we want to do that, then the event subscriber will expect
-            // the container to be attached to the tree. Not using IsAttachedToVisualTree here
-            // because a bunch of tests don't have a rooted visual tree.
-            if (container.GetVisualParent() is null)
-                throw new InvalidOperationException(
-                    "Container must be attached to parent before PrepareItemContainer is called.");
-
             var itemContainerTheme = ItemContainerTheme;
 
             if (itemContainerTheme is not null && 
diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index 9b38c261e7a..9ebff9ac7b6 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -137,9 +137,9 @@ private static void InsertContainer(
                 container = generator.CreateContainer();
             }
 
+            generator.PrepareItemContainer(container, item, index);
             itemsControl.AddLogicalChild(container);
             children.Insert(index, container);
-            generator.PrepareItemContainer(container, item, index);
         }
 
         private void ClearItemsControlLogicalChildren()
diff --git a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
index d21959ff8bd..7f0c0da0652 100644
--- a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
@@ -275,8 +275,8 @@ private Control GetOrCreateElement(ItemsSourceView items, int index)
                 }
                 else if (generator.IsItemItsOwnContainer(controlItem))
                 {
-                    AddInternalChild(controlItem);
                     generator.PrepareItemContainer(controlItem, controlItem, index);
+                    AddInternalChild(controlItem);
                     controlItem.SetValue(ItemIsOwnContainerProperty, true);
                     return controlItem;
                 }
@@ -311,8 +311,8 @@ private Control CreateElement(ItemsSourceView items, int index)
             var item = items[index];
             var container = generator.CreateContainer();
 
-            AddInternalChild(container);
             generator.PrepareItemContainer(container, item, index);
+            AddInternalChild(container);
 
             return container;
         }

From 67d200c1000e1d975807aff7e67d3cac9e021433 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 23:43:49 +0100
Subject: [PATCH 45/64] Fix menu theming.

Don't allow child menus to inherit the top level `Menu`'s `ItemContainerTheme` as that is specific to top-level menu items.
---
 src/Avalonia.Controls/ItemsControl.cs |  2 +-
 src/Avalonia.Controls/Menu.cs         | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index a082f8cdecc..6b51c3d7f02 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -302,7 +302,7 @@ protected internal virtual void PrepareContainerForItemOverride(Control containe
             {
                 if (itemTemplate is not null)
                     ic.ItemTemplate = itemTemplate;
-                if (ItemContainerTheme is { } ict)
+                if (ItemContainerTheme is { } ict && !ict.IsSet(ItemContainerThemeProperty))
                     ic.ItemContainerTheme = ict;
             }
 
diff --git a/src/Avalonia.Controls/Menu.cs b/src/Avalonia.Controls/Menu.cs
index c50cce95899..dbdcad82179 100644
--- a/src/Avalonia.Controls/Menu.cs
+++ b/src/Avalonia.Controls/Menu.cs
@@ -93,5 +93,15 @@ protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
                 inputRoot.AccessKeyHandler.MainMenu = this;
             }
         }
+
+        protected internal override void PrepareContainerForItemOverride(Control element, object? item, int index)
+        {
+            base.PrepareContainerForItemOverride(element, item, index);
+
+            // Child menu items should not inherit the menu's ItemContainerTheme as that is specific
+            // for top-level menu items.
+            if ((element as MenuItem)?.ItemContainerTheme == ItemContainerTheme)
+                element.ClearValue(ItemContainerThemeProperty);
+        }
     }
 }

From 14df77a89735473eaa75605414f5b8a72bcdf250 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 10 Dec 2022 00:22:55 +0100
Subject: [PATCH 46/64] Improve support for variable-sized items.

---
 .../VirtualizingStackPanel.cs                 | 119 ++++++++++++------
 1 file changed, 78 insertions(+), 41 deletions(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 7e5a00e6f7c..7dde543c2a5 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -92,7 +92,7 @@ protected override Size MeasureOverride(Size availableSize)
 
                 // Recycle elements outside of the expected range.
                 _realizedElements.RecycleElementsBefore(viewport.firstIndex, _recycleElement);
-                _realizedElements.RecycleElementsAfter(viewport.estimatedLastIndex, _recycleElement);
+                _realizedElements.RecycleElementsAfter(viewport.lastIndex, _recycleElement);
 
                 // Do the measure, creating/recycling elements as necessary to fill the viewport. Don't
                 // write to _realizedElements yet, only _measureElements.
@@ -307,8 +307,8 @@ private MeasureViewport CalculateMeasureViewport(ItemsSourceView items)
             var viewportStart = Orientation == Orientation.Horizontal ? viewport.X : viewport.Y;
             var viewportEnd = Orientation == Orientation.Horizontal ? viewport.Right : viewport.Bottom;
 
-            var (firstIndex, firstIndexU) = _realizedElements!.GetElementAt(viewportStart);
-            var (lastIndex, _) = _realizedElements.GetElementAt(viewportEnd);
+            var (firstIndex, firstIndexU) = _realizedElements.GetModelIndexAt(viewportStart);
+            var (lastIndex, _) = _realizedElements.GetModelIndexAt(viewportEnd);
             var estimatedElementSize = -1.0;
             var itemCount = items?.Count ?? 0;
 
@@ -329,7 +329,7 @@ private MeasureViewport CalculateMeasureViewport(ItemsSourceView items)
             return new MeasureViewport
             {
                 firstIndex = MathUtilities.Clamp(firstIndex, 0, itemCount - 1),
-                estimatedLastIndex = MathUtilities.Clamp(lastIndex, 0, itemCount - 1),
+                lastIndex = MathUtilities.Clamp(lastIndex, 0, itemCount - 1),
                 viewportUStart = viewportStart,
                 viewportUEnd = viewportEnd,
                 startU = firstIndexU,
@@ -353,23 +353,9 @@ private double EstimateElementSizeU()
             if (_realizedElements is null)
                 return _lastEstimatedElementSizeU;
 
-            var count = _realizedElements.Count;
-            var divisor = 0.0;
-            var total = 0.0;
-
-            for (var i = 0; i < count; ++i)
-            {
-                if (_realizedElements.Elements[i] is object)
-                {
-                    total += _realizedElements.SizeU[i];
-                    ++divisor;
-                }
-            }
-
-            if (divisor == 0 || total == 0)
-                return _lastEstimatedElementSizeU;
-
-            _lastEstimatedElementSizeU = total / divisor;
+            var result = _realizedElements.EstimateElementSizeU();
+            if (result >= 0)
+                _lastEstimatedElementSizeU = result;
             return _lastEstimatedElementSizeU;
         }
 
@@ -409,6 +395,10 @@ private void GenerateElements(Size availableSize, ref MeasureViewport viewport)
             var index = viewport.firstIndex;
             var u = viewport.startU;
 
+            // The layout is likely invalid. Don't create any elements and instead rely on our previous
+            // element size estimates to calculate a new desired size and trigger a new layout pass.
+            if (index >= items.Count)
+                return;
             do
             {
                 var e = GetOrCreateElement(items, index);
@@ -587,6 +577,7 @@ internal class RealizedElementList
             private List<Control?>? _elements;
             private List<double>? _sizes;
             private double _startU;
+            private bool _startUUnstable;
 
             /// <summary>
             /// Gets the number of realized elements.
@@ -671,6 +662,38 @@ public void Add(int modelIndex, Control element, double u, double sizeU)
                 return null;
             }
 
+            /// <summary>
+            /// Gets the model index and start U position of the element at the specified U position.
+            /// </summary>
+            /// <param name="u">The U position.</param>
+            /// <returns>
+            /// A tuple containing:
+            /// - The index of the item at the specified U position, or -1 if the item could not be
+            ///   determined
+            /// - The U position of the start of the item, if determined
+            /// </returns>
+            public (int index, double position) GetModelIndexAt(double u)
+            {
+                if (_elements is null || _sizes is null || _startU > u || _startUUnstable)
+                    return (-1, 0);
+
+                var index = 0;
+                var position = _startU;
+
+                while (index < _elements.Count)
+                {
+                    var size = _sizes[index];
+                    if (double.IsNaN(size))
+                        break;
+                    if (u >= position && u < position + size)
+                        return (index + FirstModelIndex, position);
+                    position += size;
+                    ++index;
+                }
+
+                return (-1, 0);
+            }
+
             /// <summary>
             /// Gets the element at the specified position on the primary axis, if realized.
             /// </summary>
@@ -700,33 +723,42 @@ public void Add(int modelIndex, Control element, double u, double sizeU)
             }
 
             /// <summary>
-            /// Gets the position of an element on the primary axis, if realized.
+            /// Estimates the average U size of all elements in the source collection based on the
+            /// realized elements.
             /// </summary>
-            /// <param name="modelIndex">The index in the source collection of the element.</param>
-            /// <param name="position">
-            /// When the method exits, contains the element's position on the primary axis, if 
-            /// the element is realized.
-            /// </param>
             /// <returns>
-            /// True if the requested element was found, otherwise false.
+            /// The estimated U size of an element, or -1 if not enough information is present to make
+            /// an estimate.
             /// </returns>
-            public bool TryGetElementU(int modelIndex, out double position)
+            public double EstimateElementSizeU()
             {
-                if (_sizes is null || modelIndex < FirstModelIndex || modelIndex > LastModelIndex)
+                var total = 0.0;
+                var divisor = 0.0;
+
+                // Start by averaging the size of the elements before the first realized element.
+                if (FirstModelIndex >= 0 && !_startUUnstable)
                 {
-                    position = double.NaN;
-                    return false;
+                    total += _startU;
+                    divisor += FirstModelIndex;
                 }
 
-                var index = modelIndex - FirstModelIndex;
-                position = StartU;
-
-                for (var i = 0; i < index; ++i)
+                // Average the size of the realized elements.
+                if (_sizes is not null)
                 {
-                    position += _sizes[i];
+                    foreach (var size in _sizes)
+                    {
+                        if (double.IsNaN(size))
+                            continue;
+                        total += size;
+                        ++divisor;
+                    }
                 }
 
-                return true;
+                // We don't have any elements on which to base our estimate.
+                if (divisor == 0 || total == 0)
+                    return -1;
+
+                return total / divisor;
             }
 
             /// <summary>
@@ -781,7 +813,7 @@ public void ItemsInserted(int modelIndex, int count, Action<Control, int, int> u
                         // The insertion point was within the realized elements, insert an empty space
                         // in _elements and _sizes.
                         _elements!.InsertMany(index, null, count);
-                        _sizes!.InsertMany(index, 0.0, count);
+                        _sizes!.InsertMany(index, double.NaN, count);
                     }
                 }
             }
@@ -840,9 +872,13 @@ public void ItemsRemoved(
                     _sizes!.RemoveRange(start, end - start);
 
                     // If the remove started before and ended within our realized elements, then our new
-                    // first index will be the index where the remove started.
+                    // first index will be the index where the remove started. Mark StartU as unstable
+                    // because we can't rely on it now to estimate element heights.
                     if (startIndex <= 0 && end < last)
+                    {
                         _firstIndex = first = modelIndex;
+                        _startUUnstable = true;
+                    }
 
                     // Update the indexes of the elements after the removed range.
                     end = _elements.Count;
@@ -942,6 +978,7 @@ public void RecycleAllElements(Action<Control> recycleElement)
             public void ResetForReuse()
             {
                 _startU = _firstIndex = 0;
+                _startUUnstable = false;
                 _elements?.Clear();
                 _sizes?.Clear();
             }
@@ -950,7 +987,7 @@ public void ResetForReuse()
         private struct MeasureViewport
         {
             public int firstIndex;
-            public int estimatedLastIndex;
+            public int lastIndex;
             public double viewportUStart;
             public double viewportUEnd;
             public double measuredV;

From 6d267f9d2036047d0a6a1a4ab99ec678c69afba3 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 10 Dec 2022 01:16:11 +0100
Subject: [PATCH 47/64] Add scroll anchoring support to ItemsControl.

This necessitated adding another stage to the container preparation lifecycle that will be called after the container is added to the logical and visual trees: `ItemContainerPrepared`. Such a method is going to be necessary anyway if we ever want to expose events for container realization so will probably be worth having regardless.
---
 .../Generators/ItemContainerGenerator.cs      | 20 +++++++++++++++++--
 src/Avalonia.Controls/ItemsControl.cs         | 18 +++++++++++++++++
 .../Presenters/PanelContainerGenerator.cs     |  1 +
 .../VirtualizingCarouselPanel.cs              | 10 +++++++++-
 .../VirtualizingStackPanel.cs                 | 12 ++++++++---
 5 files changed, 55 insertions(+), 6 deletions(-)

diff --git a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
index fe8dda3b98d..b5dc4903bfc 100644
--- a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
+++ b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
@@ -56,6 +56,22 @@ public class ItemContainerGenerator
         public void PrepareItemContainer(Control container, object? item, int index) => 
             _owner.PrepareItemContainer(container, item, index);
 
+        /// <summary>
+        /// Notifies the <see cref="ItemsControl"/> that a container has been fully prepared to
+        /// display an item.
+        /// </summary>
+        /// <param name="container">The container control.</param>
+        /// <param name="item">The item being displayed.</param>
+        /// <param name="index">The index of the item being displayed.</param>
+        /// <remarks>
+        /// This method should be called when a container has been fully prepared and added
+        /// to the logical and visual trees, but may be called before a layout pass has completed.
+        /// It should be called regardless of the result of
+        /// <see cref="IsItemItsOwnContainer(Control)"/>.
+        /// </remarks>
+        public void ItemContainerPrepared(Control container, object? item, int index) =>
+            _owner.ItemContainerPrepared(container, item, index);
+
         /// <summary>
         /// Called when the index for a container changes due to an insertion or removal in the
         /// items collection.
@@ -69,8 +85,8 @@ public void ItemContainerIndexChanged(Control container, int oldIndex, int newIn
         /// <summary>
         /// Undoes the effects of the <see cref="PrepareItemContainer(Control, object, int)"/> method.
         /// </summary>
-        /// <param name="container">The element that's used to display the specified item.</param>
-        public void ClearItemContainer(Control container) => _owner.ClearContainerForItemOverride(container);
+        /// <param name="container">The container control.</param>
+        public void ClearItemContainer(Control container) => _owner.ClearItemContainer(container);
 
         public Control? ContainerFromIndex(int index) => _owner.ContainerFromIndex(index);
         public int IndexFromContainer(Control container) => _owner.IndexFromContainer(container);
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 6b51c3d7f02..6dad539efcc 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -90,6 +90,7 @@ public IBinding? DisplayMemberBinding
         private EventHandler<ChildIndexChangedEventArgs>? _childIndexChanged;
         private IDataTemplate? _displayMemberItemTemplate;
         private Tuple<int, Control>? _containerBeingPrepared;
+        private ScrollViewer? _scrollViewer;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ItemsControl"/> class.
@@ -351,6 +352,12 @@ protected internal virtual void ClearContainerForItemOverride(Control container)
         /// <returns>true if the item is (or is eligible to be) its own container; otherwise, false.</returns>
         protected internal virtual bool IsItemItsOwnContainerOverride(Control item) => true;
 
+        protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
+        {
+            base.OnApplyTemplate(e);
+            _scrollViewer = e.NameScope.Find<ScrollViewer>("PART_ScrollViewer");
+        }
+
         /// <summary>
         /// Handles directional navigation within the <see cref="ItemsControl"/>.
         /// </summary>
@@ -494,10 +501,15 @@ internal void PrepareItemContainer(Control container, object? item, int index)
                 container.DataContext = item;
 
             PrepareContainerForItemOverride(container, item, index);
+        }
 
+        internal void ItemContainerPrepared(Control container, object? item, int index)
+        {
             _containerBeingPrepared = new(index, container);
             _childIndexChanged?.Invoke(this, new ChildIndexChangedEventArgs(container));
             _containerBeingPrepared = null;
+
+            _scrollViewer?.RegisterAnchorCandidate(container);
         }
 
         internal void ItemContainerIndexChanged(Control container, int oldIndex, int newIndex)
@@ -506,6 +518,12 @@ internal void ItemContainerIndexChanged(Control container, int oldIndex, int new
             _childIndexChanged?.Invoke(this, new ChildIndexChangedEventArgs(container));
         }
 
+        internal void ClearItemContainer(Control container)
+        {
+            _scrollViewer?.UnregisterAnchorCandidate(container);
+            ClearContainerForItemOverride(container);
+        }
+
         /// <summary>
         /// Given a collection of items, adds those that are controls to the logical children.
         /// </summary>
diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index 9ebff9ac7b6..1c94c29a356 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -140,6 +140,7 @@ private static void InsertContainer(
             generator.PrepareItemContainer(container, item, index);
             itemsControl.AddLogicalChild(container);
             children.Insert(index, container);
+            generator.ItemContainerPrepared(container, item, index);
         }
 
         private void ClearItemsControlLogicalChildren()
diff --git a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
index 7f0c0da0652..b12be377c44 100644
--- a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
@@ -2,9 +2,11 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
+using System.ComponentModel;
 using System.Diagnostics;
 using System.Threading;
 using System.Threading.Tasks;
+using System.Xml.Linq;
 using Avalonia.Animation;
 using Avalonia.Controls.Primitives;
 using Avalonia.Input;
@@ -264,13 +266,16 @@ private Control GetOrCreateElement(ItemsSourceView items, int index)
         {
             Debug.Assert(ItemsControl is not null);
 
-            if (items[index] is Control controlItem)
+            var item = items[index];
+
+            if (item is Control controlItem)
             {
                 var generator = ItemsControl!.ItemContainerGenerator;
 
                 if (controlItem.IsSet(ItemIsOwnContainerProperty))
                 {
                     controlItem.IsVisible = true;
+                    generator.ItemContainerPrepared(controlItem, item, index);
                     return controlItem;
                 }
                 else if (generator.IsItemItsOwnContainer(controlItem))
@@ -278,6 +283,7 @@ private Control GetOrCreateElement(ItemsSourceView items, int index)
                     generator.PrepareItemContainer(controlItem, controlItem, index);
                     AddInternalChild(controlItem);
                     controlItem.SetValue(ItemIsOwnContainerProperty, true);
+                    generator.ItemContainerPrepared(controlItem, item, index);
                     return controlItem;
                 }
             }
@@ -297,6 +303,7 @@ private Control GetOrCreateElement(ItemsSourceView items, int index)
                 var recycled = _recyclePool.Pop();
                 recycled.IsVisible = true;
                 generator.PrepareItemContainer(recycled, item, index);
+                generator.ItemContainerPrepared(recycled, item, index);
                 return recycled;
             }
 
@@ -313,6 +320,7 @@ private Control CreateElement(ItemsSourceView items, int index)
 
             generator.PrepareItemContainer(container, item, index);
             AddInternalChild(container);
+            generator.ItemContainerPrepared(container, item, index);
 
             return container;
         }
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 7dde543c2a5..e88b10dceb9 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -434,20 +434,24 @@ private Control GetOrCreateElement(ItemsSourceView items, int index)
 
         private Control? GetItemIsOwnContainer(ItemsSourceView items, int index)
         {
-            if (items[index] is Control controlItem)
+            var item = items[index];
+
+            if (item is Control controlItem)
             {
                 var generator = ItemsControl!.ItemContainerGenerator;
 
                 if (controlItem.IsSet(ItemIsOwnContainerProperty))
                 {
                     controlItem.IsVisible = true;
+                    generator.ItemContainerPrepared(controlItem, item, index);
                     return controlItem;
                 }
                 else if (generator.IsItemItsOwnContainer(controlItem))
                 {
-                    AddInternalChild(controlItem);
                     generator.PrepareItemContainer(controlItem, controlItem, index);
+                    AddInternalChild(controlItem);
                     controlItem.SetValue(ItemIsOwnContainerProperty, true);
+                    generator.ItemContainerPrepared(controlItem, item, index);
                     return controlItem;
                 }
             }
@@ -468,6 +472,7 @@ private Control GetOrCreateElement(ItemsSourceView items, int index)
                 var recycled = _recyclePool.Pop();
                 recycled.IsVisible = true;
                 generator.PrepareItemContainer(recycled, item, index);
+                generator.ItemContainerPrepared(recycled, item, index);
                 return recycled;
             }
 
@@ -482,8 +487,9 @@ private Control CreateElement(ItemsSourceView items, int index)
             var item = items[index];
             var container = generator.CreateContainer();
 
-            AddInternalChild(container);
             generator.PrepareItemContainer(container, item, index);
+            AddInternalChild(container);
+            generator.ItemContainerPrepared(container, item, index);
 
             return container;
         }

From 95e854ab136279faee4619ccad98b0a4a966b558 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 10 Dec 2022 17:17:25 +0100
Subject: [PATCH 48/64] Mark methods obsolete.

---
 src/Avalonia.Controls/Generators/ItemContainerGenerator.cs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
index b5dc4903bfc..d362ea24f17 100644
--- a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
+++ b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
@@ -88,7 +88,10 @@ public void ItemContainerIndexChanged(Control container, int oldIndex, int newIn
         /// <param name="container">The container control.</param>
         public void ClearItemContainer(Control container) => _owner.ClearItemContainer(container);
 
+        [Obsolete("Use ItemsControl.ContainerFromIndex")]
         public Control? ContainerFromIndex(int index) => _owner.ContainerFromIndex(index);
+
+        [Obsolete("Use ItemsControl.IndexFromContainer")]
         public int IndexFromContainer(Control container) => _owner.IndexFromContainer(container);
     }
 }

From d7201d28e6c9c396a13ffdaff9bf0ed53da2b70c Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 10 Dec 2022 17:26:53 +0100
Subject: [PATCH 49/64] Removed IItemsPresenterHost.

---
 src/Avalonia.Controls/ItemsControl.cs         | 23 +++++++++++-----
 .../Presenters/IItemsPresenterHost.cs         | 26 -------------------
 .../Presenters/ItemsPresenter.cs              |  2 +-
 ...valoniaXamlIlDataContextTypeTransformer.cs |  2 +-
 .../AvaloniaXamlIlWellKnownTypes.cs           |  4 +--
 5 files changed, 20 insertions(+), 37 deletions(-)
 delete mode 100644 src/Avalonia.Controls/Presenters/IItemsPresenterHost.cs

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 6dad539efcc..4e89c2da17f 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -23,7 +23,7 @@ namespace Avalonia.Controls
     /// Displays a collection of items.
     /// </summary>
     [PseudoClasses(":empty", ":singleitem")]
-    public class ItemsControl : TemplatedControl, IItemsPresenterHost, IChildIndexProvider
+    public class ItemsControl : TemplatedControl, IChildIndexProvider
     {
         /// <summary>
         /// The default value for the <see cref="ItemsPanel"/> property.
@@ -250,12 +250,6 @@ event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexCh
         /// </summary>
         public IEnumerable<Control> GetRealizedContainers() => Presenter?.GetRealizedContainers() ?? Array.Empty<Control>();
 
-        /// <inheritdoc/>
-        void IItemsPresenterHost.RegisterItemsPresenter(ItemsPresenter presenter)
-        {
-            Presenter = presenter;
-            _childIndexChanged?.Invoke(this, ChildIndexChangedEventArgs.Empty);
-        }
 
         /// <summary>
         /// Creates or a container that can be used to display an item.
@@ -486,6 +480,21 @@ private protected virtual ItemContainerGenerator CreateItemContainerGenerator()
         internal void AddLogicalChild(Control c) => LogicalChildren.Add(c);
         internal void RemoveLogicalChild(Control c) => LogicalChildren.Remove(c);
 
+        /// <summary>
+        /// Called by <see cref="ItemsPresenter"/> to register with the <see cref="ItemsControl"/>.
+        /// </summary>
+        /// <param name="presenter">The items presenter.</param>
+        /// <remarks>
+        /// ItemsPresenters can be within nested templates or in popups and so are not necessarily
+        /// created immediately when the ItemsControl control's template is instantiated. Instead
+        /// they register themselves using this method.
+        /// </remarks>
+        internal void RegisterItemsPresenter(ItemsPresenter presenter)
+        {
+            Presenter = presenter;
+            _childIndexChanged?.Invoke(this, ChildIndexChangedEventArgs.Empty);
+        }
+
         internal void PrepareItemContainer(Control container, object? item, int index)
         {
             var itemContainerTheme = ItemContainerTheme;
diff --git a/src/Avalonia.Controls/Presenters/IItemsPresenterHost.cs b/src/Avalonia.Controls/Presenters/IItemsPresenterHost.cs
deleted file mode 100644
index 8bf190dbda7..00000000000
--- a/src/Avalonia.Controls/Presenters/IItemsPresenterHost.cs
+++ /dev/null
@@ -1,26 +0,0 @@
-using Avalonia.Metadata;
-using Avalonia.Styling;
-
-namespace Avalonia.Controls.Presenters
-{
-    /// <summary>
-    /// Represents a control which hosts an items presenter.
-    /// </summary>
-    /// <remarks>
-    /// This interface is implemented by <see cref="ItemsControl"/> which usually contains an
-    /// <see cref="ItemsPresenter"/> and exposes it through its 
-    /// <see cref="ItemsControl.Presenter"/> property. ItemsPresenters can be within
-    /// nested templates or in popups and so are not necessarily created immediately when the
-    /// parent control's template is instantiated so they register themselves using this 
-    /// interface.
-    /// </remarks>
-    [NotClientImplementable]
-    public interface IItemsPresenterHost
-    {
-        /// <summary>
-        /// Registers an <see cref="ItemsPresenter"/> with a host control.
-        /// </summary>
-        /// <param name="presenter">The items presenter.</param>
-        void RegisterItemsPresenter(ItemsPresenter presenter);
-    }
-}
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
index 8297922664d..e0252feed59 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
@@ -143,7 +143,7 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
                 if (change.NewValue is ItemsControl itemsControl)
                 {
                     ItemsControl = itemsControl;
-                    ((IItemsPresenterHost)itemsControl)?.RegisterItemsPresenter(this);
+                    ItemsControl.RegisterItemsPresenter(this);
                 }
             }
             else if (change.Property == ItemsPanelProperty)
diff --git a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlDataContextTypeTransformer.cs b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlDataContextTypeTransformer.cs
index d4dfcf9c4b5..574d46e7375 100644
--- a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlDataContextTypeTransformer.cs
+++ b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlDataContextTypeTransformer.cs
@@ -79,7 +79,7 @@ public IXamlAstNode Transform(AstTransformationContext context, IXamlAstNode nod
                         {
                             var parentType = parentObject.Type.GetClrType();
 
-                            if (context.GetAvaloniaTypes().IItemsPresenterHost.IsDirectlyAssignableFrom(parentType)
+                            if (context.GetAvaloniaTypes().ItemsControl.IsDirectlyAssignableFrom(parentType)
                                 || context.GetAvaloniaTypes().ItemsRepeater.IsDirectlyAssignableFrom(parentType))
                             {
                                 inferredDataContextTypeNode = InferDataContextOfPresentedItem(context, on, parentObject);
diff --git a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlWellKnownTypes.cs b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlWellKnownTypes.cs
index 87a037c16ae..c5bfdd86873 100644
--- a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlWellKnownTypes.cs
+++ b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlWellKnownTypes.cs
@@ -54,7 +54,7 @@ class AvaloniaXamlIlWellKnownTypes
 
         public IXamlType DataTemplate { get; }
         public IXamlType IDataTemplate { get; }
-        public IXamlType IItemsPresenterHost { get; }
+        public IXamlType ItemsControl { get; }
         public IXamlType ItemsRepeater { get; }
         public IXamlType ReflectionBindingExtension { get; }
 
@@ -177,7 +177,7 @@ public AvaloniaXamlIlWellKnownTypes(TransformerConfiguration cfg)
             ResolveByNameExtension = cfg.TypeSystem.GetType("Avalonia.Markup.Xaml.MarkupExtensions.ResolveByNameExtension");
             DataTemplate = cfg.TypeSystem.GetType("Avalonia.Markup.Xaml.Templates.DataTemplate");
             IDataTemplate = cfg.TypeSystem.GetType("Avalonia.Controls.Templates.IDataTemplate");
-            IItemsPresenterHost = cfg.TypeSystem.GetType("Avalonia.Controls.Presenters.IItemsPresenterHost");
+            ItemsControl = cfg.TypeSystem.GetType("Avalonia.Controls.ItemsControl");
             ItemsRepeater = cfg.TypeSystem.GetType("Avalonia.Controls.ItemsRepeater");
             ReflectionBindingExtension = cfg.TypeSystem.GetType("Avalonia.Markup.Xaml.MarkupExtensions.ReflectionBindingExtension");
             RelativeSource = cfg.TypeSystem.GetType("Avalonia.Data.RelativeSource");

From d5a585d7225c6f4ae1d371db8f1e6b40ccf33870 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 10 Dec 2022 21:29:49 +0100
Subject: [PATCH 50/64] Tweaked VirtualizingPanel API.

And added some more doc comments.
---
 .../Generators/ItemContainerGenerator.cs      | 18 ++++++-
 .../VirtualizingCarouselPanel.cs              | 29 +++++------
 src/Avalonia.Controls/VirtualizingPanel.cs    | 28 ++++++++++-
 .../VirtualizingStackPanel.cs                 | 48 ++++++++++---------
 4 files changed, 82 insertions(+), 41 deletions(-)

diff --git a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
index d362ea24f17..b6f54d51ebc 100644
--- a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
+++ b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
@@ -6,7 +6,23 @@ namespace Avalonia.Controls.Generators
     /// Generates containers for an <see cref="ItemsControl"/>.
     /// </summary>
     /// <remarks>
-    /// Although this class is similar to that found in WPF/UWP, in Avalonia this class only
+    /// When creating a container for an item from a <see cref="VirtualizingPanel"/>, the following
+    /// method order should be followed:
+    /// 
+    /// - <see cref="IsItemItsOwnContainer(Control)"/> should first be called if the item is
+    ///   derived from the <see cref="Control"/> class. If this method returns true then the
+    ///   item itself should be used as the container.
+    /// - If <see cref="IsItemItsOwnContainer(Control)"/> returns false then
+    ///   <see cref="CreateContainer"/> should be called to create a new container.
+    /// - <see cref="PrepareItemContainer(Control, object?, int)"/> method should be called for the
+    ///   container.
+    /// - The container should then be added to the panel using 
+    ///   <see cref="VirtualizingPanel.AddInternalChild(Control)"/>
+    /// - Finally, <see cref="ItemContainerPrepared(Control, object?, int)"/> should be called.
+    /// - When the item is ready to be recycled, <see cref="ClearItemContainer(Control)"/> should
+    ///   be called if <see cref="IsItemItsOwnContainer(Control)"/> returned false.
+    /// 
+    /// NOTE: Although this class is similar to that found in WPF/UWP, in Avalonia this class only
     /// concerns itself with generating and clearing item containers; it does not maintain a
     /// record of the currently realized containers, that responsibility is delegated to the
     /// items panel.
diff --git a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
index b12be377c44..f655fd18d40 100644
--- a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
@@ -1,12 +1,9 @@
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
-using System.ComponentModel;
 using System.Diagnostics;
 using System.Threading;
 using System.Threading.Tasks;
-using System.Xml.Linq;
 using Avalonia.Animation;
 using Avalonia.Controls.Primitives;
 using Avalonia.Input;
@@ -97,7 +94,7 @@ bool ILogicalScrollable.BringIntoView(Control target, Rect targetRect)
 
         protected override Size MeasureOverride(Size availableSize)
         {
-            var items = ItemsControl?.ItemsView ?? ItemsSourceView.Empty;
+            var items = Items;
             var index = (int)_offset.X;
 
             if (index != _realizedIndex)
@@ -249,7 +246,7 @@ void Remove(int index, int count)
             InvalidateMeasure();
         }
 
-        private Control GetOrCreateElement(ItemsSourceView items, int index)
+        private Control GetOrCreateElement(IReadOnlyList<object?> items, int index)
         {
             return GetRealizedElement(index) ??
                 GetItemIsOwnContainer(items, index) ??
@@ -262,15 +259,15 @@ private Control GetOrCreateElement(ItemsSourceView items, int index)
             return _realizedIndex == index ? _realized : null;
         }
 
-        private Control? GetItemIsOwnContainer(ItemsSourceView items, int index)
+        private Control? GetItemIsOwnContainer(IReadOnlyList<object?> items, int index)
         {
-            Debug.Assert(ItemsControl is not null);
+            Debug.Assert(ItemContainerGenerator is not null);
 
             var item = items[index];
 
             if (item is Control controlItem)
             {
-                var generator = ItemsControl!.ItemContainerGenerator;
+                var generator = ItemContainerGenerator;
 
                 if (controlItem.IsSet(ItemIsOwnContainerProperty))
                 {
@@ -291,11 +288,11 @@ private Control GetOrCreateElement(ItemsSourceView items, int index)
             return null;
         }
 
-        private Control? GetRecycledElement(ItemsSourceView items, int index)
+        private Control? GetRecycledElement(IReadOnlyList<object?> items, int index)
         {
-            Debug.Assert(ItemsControl is not null);
+            Debug.Assert(ItemContainerGenerator is not null);
 
-            var generator = ItemsControl!.ItemContainerGenerator;
+            var generator = ItemContainerGenerator;
             var item = items[index];
 
             if (_recyclePool?.Count > 0)
@@ -310,11 +307,11 @@ private Control GetOrCreateElement(ItemsSourceView items, int index)
             return null;
         }
 
-        private Control CreateElement(ItemsSourceView items, int index)
+        private Control CreateElement(IReadOnlyList<object?> items, int index)
         {
-            Debug.Assert(ItemsControl is not null);
+            Debug.Assert(ItemContainerGenerator is not null);
 
-            var generator = ItemsControl!.ItemContainerGenerator;
+            var generator = ItemContainerGenerator;
             var item = items[index];
             var container = generator.CreateContainer();
 
@@ -327,7 +324,7 @@ private Control CreateElement(ItemsSourceView items, int index)
 
         private void RecycleElement(Control element)
         {
-            Debug.Assert(ItemsControl is not null);
+            Debug.Assert(ItemContainerGenerator is not null);
 
             if (element.IsSet(ItemIsOwnContainerProperty))
             {
@@ -335,7 +332,7 @@ private void RecycleElement(Control element)
             }
             else
             {
-                ItemsControl!.ItemContainerGenerator.ClearItemContainer(element);
+                ItemContainerGenerator.ClearItemContainer(element);
                 _recyclePool ??= new();
                 _recyclePool.Push(element);
                 element.IsVisible = false;
diff --git a/src/Avalonia.Controls/VirtualizingPanel.cs b/src/Avalonia.Controls/VirtualizingPanel.cs
index 59146656e63..62918c3d35e 100644
--- a/src/Avalonia.Controls/VirtualizingPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingPanel.cs
@@ -1,20 +1,44 @@
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Diagnostics.CodeAnalysis;
+using Avalonia.Controls.Generators;
+using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Utils;
 using Avalonia.Input;
+using Avalonia.Layout;
 
 namespace Avalonia.Controls
 {
     /// <summary>
-    /// Base class for panels that can be used to virtualize items.
+    /// Base class for panels that can be used to virtualize items for an <see cref="ItemsControl"/>.
     /// </summary>
+    /// <remarks>
+    /// Panels should implement the abstract members of this class to provide virtualization of
+    /// items in a <see cref="ItemsControl"/>. Derived panels can manage scrolling by implementing
+    /// <see cref="ILogicalScrollable"/> or by listening to the 
+    /// <see cref="Layoutable.EffectiveViewportChanged"/> event.
+    /// 
+    /// The methods on the <see cref="ItemContainerGenerator"/> should be used to create, prepare and
+    /// clear containers for items.
+    /// </remarks>
     public abstract class VirtualizingPanel : Panel, INavigableContainer
     {
         private ItemsControl? _itemsControl;
 
+        /// <summary>
+        /// Gets the <see cref="ItemContainerGenerator"/> for this <see cref="VirtualizingPanel"/>.
+        /// </summary>
+        public ItemContainerGenerator? ItemContainerGenerator => _itemsControl?.ItemContainerGenerator;
+
+        /// <summary>
+        /// Gets the items to display.
+        /// </summary>
+        protected IReadOnlyList<object?> Items => ItemsControl?.ItemsView ?? ItemsSourceView.Empty;
+
+        /// <summary>
+        /// Gets the <see cref="ItemsControl"/> that the panel is displaying items for.
+        /// </summary>
         protected ItemsControl? ItemsControl 
         {
             get => _itemsControl;
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index e88b10dceb9..8471595a465 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -11,6 +11,9 @@
 
 namespace Avalonia.Controls
 {
+    /// <summary>
+    /// Arranges and virtualizes content on a single line that is oriented either horizontally or vertically.
+    /// </summary>
     public class VirtualizingStackPanel : VirtualizingPanel
     {
         /// <summary>
@@ -64,9 +67,9 @@ protected override Size MeasureOverride(Size availableSize)
 
             try
             {
-                var items = ItemsControl?.ItemsView;
+                var items = Items;
 
-                if (items is null || items.Count == 0)
+                if (items.Count == 0)
                 {
                     RemoveInternalChildRange(0, Children.Count);
                     return default;
@@ -171,7 +174,7 @@ protected override void OnItemsChanged(IReadOnlyList<object?> items, NotifyColle
 
         protected override IInputElement? GetControl(NavigationDirection direction, IInputElement? from, bool wrap)
         {
-            var count = ItemsControl?.ItemsView.Count ?? 0;
+            var count = Items.Count;
 
             if (count == 0 || from is not Control fromControl)
                 return null;
@@ -238,9 +241,9 @@ protected override void OnItemsChanged(IReadOnlyList<object?> items, NotifyColle
 
         protected internal override Control? ScrollIntoView(int index)
         {
-            var items = ItemsControl?.ItemsView;
+            var items = Items;
 
-            if (_isInLayout || items is null || index < 0 || index >= items.Count)
+            if (_isInLayout || index < 0 || index >= items.Count)
                 return null;
 
             if (GetRealizedElement(index) is Control element)
@@ -295,7 +298,7 @@ protected override void OnItemsChanged(IReadOnlyList<object?> items, NotifyColle
             return _realizedElements?.Elements ?? Array.Empty<Control>();
         }
 
-        private MeasureViewport CalculateMeasureViewport(ItemsSourceView items)
+        private MeasureViewport CalculateMeasureViewport(IReadOnlyList<object?> items)
         {
             Debug.Assert(_realizedElements is not null);
 
@@ -336,7 +339,7 @@ private MeasureViewport CalculateMeasureViewport(ItemsSourceView items)
             };
         }
 
-        private Size CalculateDesiredSize(Orientation orientation, ItemsSourceView items, double sizeV)
+        private Size CalculateDesiredSize(Orientation orientation, IReadOnlyList<object?> items, double sizeV)
         {
             var sizeU = EstimateElementSizeU() * items.Count;
 
@@ -387,10 +390,9 @@ private Rect EstimateViewport()
 
         private void GenerateElements(Size availableSize, ref MeasureViewport viewport)
         {
-            Debug.Assert(ItemsControl is not null);
             Debug.Assert(_measureElements is not null);
 
-            var items = ItemsControl!.ItemsView;
+            var items = Items;
             var horizontal = Orientation == Orientation.Horizontal;
             var index = viewport.firstIndex;
             var u = viewport.startU;
@@ -415,7 +417,7 @@ private void GenerateElements(Size availableSize, ref MeasureViewport viewport)
             } while (u < viewport.viewportUEnd && index < items.Count);
         }
 
-        private Control GetOrCreateElement(ItemsSourceView items, int index)
+        private Control GetOrCreateElement(IReadOnlyList<object?> items, int index)
         {
             var e = GetRealizedElement(index) ??
                 GetItemIsOwnContainer(items, index) ??
@@ -432,13 +434,13 @@ private Control GetOrCreateElement(ItemsSourceView items, int index)
             return _realizedElements?.GetElement(index);
         }
 
-        private Control? GetItemIsOwnContainer(ItemsSourceView items, int index)
+        private Control? GetItemIsOwnContainer(IReadOnlyList<object?> items, int index)
         {
             var item = items[index];
 
             if (item is Control controlItem)
             {
-                var generator = ItemsControl!.ItemContainerGenerator;
+                var generator = ItemContainerGenerator!;
 
                 if (controlItem.IsSet(ItemIsOwnContainerProperty))
                 {
@@ -459,11 +461,11 @@ private Control GetOrCreateElement(ItemsSourceView items, int index)
             return null;
         }
 
-        private Control? GetRecycledElement(ItemsSourceView items, int index)
+        private Control? GetRecycledElement(IReadOnlyList<object?> items, int index)
         {
-            Debug.Assert(ItemsControl is not null);
+            Debug.Assert(ItemContainerGenerator is not null);
 
-            var generator = ItemsControl!.ItemContainerGenerator;
+            var generator = ItemContainerGenerator!;
             var item = items[index];
 
 
@@ -479,11 +481,11 @@ private Control GetOrCreateElement(ItemsSourceView items, int index)
             return null;
         }
 
-        private Control CreateElement(ItemsSourceView items, int index)
+        private Control CreateElement(IReadOnlyList<object?> items, int index)
         {
-            Debug.Assert(ItemsControl is not null);
+            Debug.Assert(ItemContainerGenerator is not null);
 
-            var generator = ItemsControl!.ItemContainerGenerator;
+            var generator = ItemContainerGenerator!;
             var item = items[index];
             var container = generator.CreateContainer();
 
@@ -502,7 +504,7 @@ private double GetOrEstimateElementPosition(int index)
 
         private void RecycleElement(Control element)
         {
-            Debug.Assert(ItemsControl is not null);
+            Debug.Assert(ItemContainerGenerator is not null);
             
             if (element.IsSet(ItemIsOwnContainerProperty))
             {
@@ -510,7 +512,7 @@ private void RecycleElement(Control element)
             }
             else
             {
-                ItemsControl!.ItemContainerGenerator.ClearItemContainer(element);
+                ItemContainerGenerator!.ClearItemContainer(element);
                 _recyclePool ??= new();
                 _recyclePool.Push(element);
                 element.IsVisible = false;
@@ -519,7 +521,9 @@ private void RecycleElement(Control element)
 
         private void UpdateElementIndex(Control element, int oldIndex, int newIndex)
         {
-            ItemsControl!.ItemContainerGenerator.ItemContainerIndexChanged(element, oldIndex, newIndex);
+            Debug.Assert(ItemContainerGenerator is not null);
+
+            ItemContainerGenerator.ItemContainerIndexChanged(element, oldIndex, newIndex);
         }
 
         private void OnEffectiveViewportChanged(object? sender, EffectiveViewportChangedEventArgs e)
@@ -575,7 +579,7 @@ void Invalidate(Control c)
         }
 
         /// <summary>
-        /// Stores the realized element state for a <see cref="VirtualizingStackPanel"/> in smooth mode.
+        /// Stores the realized element state for a <see cref="VirtualizingStackPanel"/>.
         /// </summary>
         internal class RealizedElementList
         {

From 9610c80bd3a868e42409d6266f1ee9f39679d845 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 10 Dec 2022 21:34:10 +0100
Subject: [PATCH 51/64] Remove references to "model index".

It's a TreeDataGrid concept (which is where this code was adapted from).
---
 .../VirtualizingStackPanel.cs                 | 120 +++++++++---------
 1 file changed, 60 insertions(+), 60 deletions(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 8471595a465..a02d963ff87 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -102,7 +102,7 @@ protected override Size MeasureOverride(Size availableSize)
                 GenerateElements(availableSize, ref viewport);
 
                 // Now we know what definitely fits, recycle anything left over.
-                _realizedElements.RecycleElementsAfter(_measureElements.LastModelIndex, _recycleElement);
+                _realizedElements.RecycleElementsAfter(_measureElements.LastIndex, _recycleElement);
 
                 // And swap the measureElements and realizedElements collection.
                 (_measureElements, _realizedElements) = (_realizedElements, _measureElements);
@@ -310,8 +310,8 @@ private MeasureViewport CalculateMeasureViewport(IReadOnlyList<object?> items)
             var viewportStart = Orientation == Orientation.Horizontal ? viewport.X : viewport.Y;
             var viewportEnd = Orientation == Orientation.Horizontal ? viewport.Right : viewport.Bottom;
 
-            var (firstIndex, firstIndexU) = _realizedElements.GetModelIndexAt(viewportStart);
-            var (lastIndex, _) = _realizedElements.GetModelIndexAt(viewportEnd);
+            var (firstIndex, firstIndexU) = _realizedElements.GetIndexAt(viewportStart);
+            var (lastIndex, _) = _realizedElements.GetIndexAt(viewportEnd);
             var estimatedElementSize = -1.0;
             var itemCount = items?.Count ?? 0;
 
@@ -595,14 +595,14 @@ internal class RealizedElementList
             public int Count => _elements?.Count ?? 0;
 
             /// <summary>
-            /// Gets the model index of the first realized element, or -1 if no elements are realized.
+            /// Gets the index of the first realized element, or -1 if no elements are realized.
             /// </summary>
-            public int FirstModelIndex => _elements?.Count > 0 ? _firstIndex : -1;
+            public int FirstIndex => _elements?.Count > 0 ? _firstIndex : -1;
 
             /// <summary>
-            /// Gets the model index of the last realized element, or -1 if no elements are realized.
+            /// Gets the index of the last realized element, or -1 if no elements are realized.
             /// </summary>
-            public int LastModelIndex => _elements?.Count > 0 ? _firstIndex + _elements.Count - 1 : -1;
+            public int LastIndex => _elements?.Count > 0 ? _firstIndex + _elements.Count - 1 : -1;
 
             /// <summary>
             /// Gets the elements.
@@ -622,14 +622,14 @@ internal class RealizedElementList
             /// <summary>
             /// Adds a newly realized element to the collection.
             /// </summary>
-            /// <param name="modelIndex">The model index of the element.</param>
+            /// <param name="index">The index of the element.</param>
             /// <param name="element">The element.</param>
             /// <param name="u">The position of the elemnt on the primary axis.</param>
             /// <param name="sizeU">The size of the element on the primary axis.</param>
-            public void Add(int modelIndex, Control element, double u, double sizeU)
+            public void Add(int index, Control element, double u, double sizeU)
             {
-                if (modelIndex < 0)
-                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+                if (index < 0)
+                    throw new ArgumentOutOfRangeException(nameof(index));
 
                 _elements ??= new List<Control?>();
                 _sizes ??= new List<double>();
@@ -639,14 +639,14 @@ public void Add(int modelIndex, Control element, double u, double sizeU)
                     _elements.Add(element);
                     _sizes.Add(sizeU);
                     _startU = u;
-                    _firstIndex = modelIndex;
+                    _firstIndex = index;
                 }
-                else if (modelIndex == LastModelIndex + 1)
+                else if (index == LastIndex + 1)
                 {
                     _elements.Add(element);
                     _sizes.Add(sizeU);
                 }
-                else if (modelIndex == FirstModelIndex - 1)
+                else if (index == FirstIndex - 1)
                 {
                     --_firstIndex;
                     _elements.Insert(0, element);
@@ -660,20 +660,20 @@ public void Add(int modelIndex, Control element, double u, double sizeU)
             }
 
             /// <summary>
-            /// Gets the element at the specified model index, if realized.
+            /// Gets the element at the specified index, if realized.
             /// </summary>
-            /// <param name="modelIndex">The index in the source collection of the element to get.</param>
+            /// <param name="index">The index in the source collection of the element to get.</param>
             /// <returns>The element if realized; otherwise null.</returns>
-            public Control? GetElement(int modelIndex)
+            public Control? GetElement(int index)
             {
-                var index = modelIndex - FirstModelIndex;
-                if (index >= 0 && index < _elements?.Count)
-                    return _elements[index];
+                var i = index - FirstIndex;
+                if (i >= 0 && i < _elements?.Count)
+                    return _elements[i];
                 return null;
             }
 
             /// <summary>
-            /// Gets the model index and start U position of the element at the specified U position.
+            /// Gets the index and start U position of the element at the specified U position.
             /// </summary>
             /// <param name="u">The U position.</param>
             /// <returns>
@@ -682,7 +682,7 @@ public void Add(int modelIndex, Control element, double u, double sizeU)
             ///   determined
             /// - The U position of the start of the item, if determined
             /// </returns>
-            public (int index, double position) GetModelIndexAt(double u)
+            public (int index, double position) GetIndexAt(double u)
             {
                 if (_elements is null || _sizes is null || _startU > u || _startUUnstable)
                     return (-1, 0);
@@ -696,7 +696,7 @@ public void Add(int modelIndex, Control element, double u, double sizeU)
                     if (double.IsNaN(size))
                         break;
                     if (u >= position && u < position + size)
-                        return (index + FirstModelIndex, position);
+                        return (index + FirstIndex, position);
                     position += size;
                     ++index;
                 }
@@ -718,7 +718,7 @@ public void Add(int modelIndex, Control element, double u, double sizeU)
                     return (-1, 0);
 
                 var u = StartU;
-                var i = FirstModelIndex;
+                var i = FirstIndex;
 
                 foreach (var size in _sizes)
                 {
@@ -746,10 +746,10 @@ public double EstimateElementSizeU()
                 var divisor = 0.0;
 
                 // Start by averaging the size of the elements before the first realized element.
-                if (FirstModelIndex >= 0 && !_startUUnstable)
+                if (FirstIndex >= 0 && !_startUUnstable)
                 {
                     total += _startU;
-                    divisor += FirstModelIndex;
+                    divisor += FirstIndex;
                 }
 
                 // Average the size of the realized elements.
@@ -772,38 +772,38 @@ public double EstimateElementSizeU()
             }
 
             /// <summary>
-            /// Gets the model index of the specified element.
+            /// Gets the index of the specified element.
             /// </summary>
             /// <param name="element">The element.</param>
-            /// <returns>The model index or -1 if the element is not present in the collection.</returns>
+            /// <returns>The index or -1 if the element is not present in the collection.</returns>
             public int GetIndex(Control element)
             {
-                return _elements?.IndexOf(element) is int index && index >= 0 ? index + FirstModelIndex : -1;
+                return _elements?.IndexOf(element) is int index && index >= 0 ? index + FirstIndex : -1;
             }
 
             /// <summary>
             /// Updates the elements in response to items being inserted into the source collection.
             /// </summary>
-            /// <param name="modelIndex">The index in the source collection of the insert.</param>
+            /// <param name="index">The index in the source collection of the insert.</param>
             /// <param name="count">The number of items inserted.</param>
             /// <param name="updateElementIndex">A method used to update the element indexes.</param>
-            public void ItemsInserted(int modelIndex, int count, Action<Control, int, int> updateElementIndex)
+            public void ItemsInserted(int index, int count, Action<Control, int, int> updateElementIndex)
             {
-                if (modelIndex < 0)
-                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+                if (index < 0)
+                    throw new ArgumentOutOfRangeException(nameof(index));
                 if (_elements is null || _elements.Count == 0)
                     return;
 
                 // Get the index within the realized _elements collection.
-                var first = FirstModelIndex;
-                var index = modelIndex - first;
+                var first = FirstIndex;
+                var realizedIndex = index - first;
 
-                if (index < Count)
+                if (realizedIndex < Count)
                 {
                     // The insertion point affects the realized elements. Update the index of the
                     // elements after the insertion point.
                     var elementCount = _elements.Count;
-                    var start = Math.Max(index, 0);
+                    var start = Math.Max(realizedIndex, 0);
                     var newIndex = first + count;
 
                     for (var i = start; i < elementCount; ++i)
@@ -813,7 +813,7 @@ public void ItemsInserted(int modelIndex, int count, Action<Control, int, int> u
                         ++newIndex;
                     }
 
-                    if (index <= 0)
+                    if (realizedIndex <= 0)
                     {
                         // The insertion point was before the first element, update the first index.
                         _firstIndex += count;
@@ -822,8 +822,8 @@ public void ItemsInserted(int modelIndex, int count, Action<Control, int, int> u
                     {
                         // The insertion point was within the realized elements, insert an empty space
                         // in _elements and _sizes.
-                        _elements!.InsertMany(index, null, count);
-                        _sizes!.InsertMany(index, double.NaN, count);
+                        _elements!.InsertMany(realizedIndex, null, count);
+                        _sizes!.InsertMany(realizedIndex, double.NaN, count);
                     }
                 }
             }
@@ -831,26 +831,26 @@ public void ItemsInserted(int modelIndex, int count, Action<Control, int, int> u
             /// <summary>
             /// Updates the elements in response to items being removed from the source collection.
             /// </summary>
-            /// <param name="modelIndex">The index in the source collection of the remove.</param>
+            /// <param name="index">The index in the source collection of the remove.</param>
             /// <param name="count">The number of items removed.</param>
             /// <param name="updateElementIndex">A method used to update the element indexes.</param>
             /// <param name="recycleElement">A method used to recycle elements.</param>
             public void ItemsRemoved(
-                int modelIndex,
+                int index,
                 int count,
                 Action<Control, int, int> updateElementIndex,
                 Action<Control> recycleElement)
             {
-                if (modelIndex < 0)
-                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+                if (index < 0)
+                    throw new ArgumentOutOfRangeException(nameof(index));
                 if (_elements is null || _elements.Count == 0)
                     return;
 
                 // Get the removal start and end index within the realized _elements collection.
-                var first = FirstModelIndex;
-                var last = LastModelIndex;
-                var startIndex = modelIndex - first;
-                var endIndex = (modelIndex + count) - first;
+                var first = FirstIndex;
+                var last = LastIndex;
+                var startIndex = index - first;
+                var endIndex = (index + count) - first;
 
                 if (endIndex < 0)
                 {
@@ -886,7 +886,7 @@ public void ItemsRemoved(
                     // because we can't rely on it now to estimate element heights.
                     if (startIndex <= 0 && end < last)
                     {
-                        _firstIndex = first = modelIndex;
+                        _firstIndex = first = index;
                         _startUUnstable = true;
                     }
 
@@ -905,20 +905,20 @@ public void ItemsRemoved(
             /// <summary>
             /// Recycles elements before a specific index.
             /// </summary>
-            /// <param name="modelIndex">The index in the source collection of new first element.</param>
+            /// <param name="index">The index in the source collection of new first element.</param>
             /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void RecycleElementsBefore(int modelIndex, Action<Control> recycleElement)
+            public void RecycleElementsBefore(int index, Action<Control> recycleElement)
             {
-                if (modelIndex <= FirstModelIndex || _elements is null || _elements.Count == 0)
+                if (index <= FirstIndex || _elements is null || _elements.Count == 0)
                     return;
 
-                if (modelIndex > LastModelIndex)
+                if (index > LastIndex)
                 {
                     RecycleAllElements(recycleElement);
                 }
                 else
                 {
-                    var endIndex = modelIndex - FirstModelIndex;
+                    var endIndex = index - FirstIndex;
 
                     for (var i = 0; i < endIndex; ++i)
                     {
@@ -928,27 +928,27 @@ public void RecycleElementsBefore(int modelIndex, Action<Control> recycleElement
 
                     _elements.RemoveRange(0, endIndex);
                     _sizes!.RemoveRange(0, endIndex);
-                    _firstIndex = modelIndex;
+                    _firstIndex = index;
                 }
             }
 
             /// <summary>
             /// Recycles elements after a specific index.
             /// </summary>
-            /// <param name="modelIndex">The index in the source collection of new last element.</param>
+            /// <param name="index">The index in the source collection of new last element.</param>
             /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void RecycleElementsAfter(int modelIndex, Action<Control> recycleElement)
+            public void RecycleElementsAfter(int index, Action<Control> recycleElement)
             {
-                if (modelIndex >= LastModelIndex || _elements is null || _elements.Count == 0)
+                if (index >= LastIndex || _elements is null || _elements.Count == 0)
                     return;
 
-                if (modelIndex < FirstModelIndex)
+                if (index < FirstIndex)
                 {
                     RecycleAllElements(recycleElement);
                 }
                 else
                 {
-                    var startIndex = (modelIndex + 1) - FirstModelIndex;
+                    var startIndex = (index + 1) - FirstIndex;
                     var count = _elements.Count;
 
                     for (var i = startIndex; i < count; ++i)

From f371f1887051dbef75155c59c8cf846c5a3b5216 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 12 Dec 2022 11:48:43 +0100
Subject: [PATCH 52/64] Use correct submodule commit.

Somehow got changed to an older commit.
---
 src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github b/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github
index 491de981dd4..5e498f8bcca 160000
--- a/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github
+++ b/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github
@@ -1 +1 @@
-Subproject commit 491de981dd4433ee58bc9540e2cd4a5d168f8168
+Subproject commit 5e498f8bcca403a34aff5efc825cbb4e12b7fa8e

From 9781a13256db78b92dfc120b33d603a9ac0d1832 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 12 Dec 2022 15:33:27 +0100
Subject: [PATCH 53/64] Remove Smooth suffix.

`VirtualizingStackPanel` only does smooth scrolling now.
---
 ...StackPanelTests_Smooth.cs => VirtualizingStackPanelTests.cs} | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
 rename tests/Avalonia.Controls.UnitTests/{VirtualizingStackPanelTests_Smooth.cs => VirtualizingStackPanelTests.cs} (99%)

diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
similarity index 99%
rename from tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs
rename to tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
index 54b76b1931f..5f21a7a8829 100644
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
@@ -14,7 +14,7 @@
 
 namespace Avalonia.Controls.UnitTests
 {
-    public class VirtualizingStackPanelTests_Smooth
+    public class VirtualizingStackPanelTests
     {
         [Fact]
         public void Creates_Initial_Items()

From c55b7a9000c3d208bb870761ab059d43dec58de2 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 12 Dec 2022 16:36:45 +0100
Subject: [PATCH 54/64] Correctly handle control items being removed.

---
 src/Avalonia.Controls/VirtualizingPanel.cs    | 11 +++
 .../VirtualizingStackPanel.cs                 | 41 +++++---
 .../VirtualizingStackPanelTests.cs            | 97 ++++++++++++++++---
 3 files changed, 119 insertions(+), 30 deletions(-)

diff --git a/src/Avalonia.Controls/VirtualizingPanel.cs b/src/Avalonia.Controls/VirtualizingPanel.cs
index 62918c3d35e..7780843eb54 100644
--- a/src/Avalonia.Controls/VirtualizingPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingPanel.cs
@@ -154,6 +154,17 @@ protected void InsertInternalChild(int index, Control control)
             Children.Insert(index, control);
         }
 
+        /// <summary>
+        /// Removes a child element from the <see cref="Panel.Children"/> collection.
+        /// </summary>
+        /// <param name="child">The child to remove/</param>
+        protected void RemoveInternalChild(Control child)
+        {
+            var itemsControl = EnsureItemsControl();
+            itemsControl.RemoveLogicalChild(child);
+            Children.Remove(child);
+        }
+
         /// <summary>
         /// Removes child elements from the <see cref="Panel.Children"/> collection.
         /// </summary>
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index a02d963ff87..dba45b15051 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -27,6 +27,7 @@ public class VirtualizingStackPanel : VirtualizingPanel
 
         private static readonly Rect s_invalidViewport = new(double.PositiveInfinity, double.PositiveInfinity, 0, 0);
         private readonly Action<Control> _recycleElement;
+        private readonly Action<Control> _recycleElementOnItemRemoved;
         private readonly Action<Control, int, int> _updateElementIndex;
         private int _anchorIndex = -1;
         private Control? _anchorElement;
@@ -41,6 +42,7 @@ public class VirtualizingStackPanel : VirtualizingPanel
         public VirtualizingStackPanel()
         {
             _recycleElement = RecycleElement;
+            _recycleElementOnItemRemoved = RecycleElementOnItemRemoved;
             _updateElementIndex = UpdateElementIndex;
             EffectiveViewportChanged += OnEffectiveViewportChanged;
         }
@@ -68,13 +70,6 @@ protected override Size MeasureOverride(Size availableSize)
             try
             {
                 var items = Items;
-
-                if (items.Count == 0)
-                {
-                    RemoveInternalChildRange(0, Children.Count);
-                    return default;
-                }
-
                 var orientation = Orientation;
 
                 _realizedElements ??= new();
@@ -153,6 +148,8 @@ protected override Size ArrangeOverride(Size finalSize)
 
         protected override void OnItemsChanged(IReadOnlyList<object?> items, NotifyCollectionChangedEventArgs e)
         {
+            InvalidateMeasure();
+
             if (_realizedElements is null)
                 return;
 
@@ -162,14 +159,12 @@ protected override void OnItemsChanged(IReadOnlyList<object?> items, NotifyColle
                     _realizedElements.ItemsInserted(e.NewStartingIndex, e.NewItems!.Count, _updateElementIndex);
                     break;
                 case NotifyCollectionChangedAction.Remove:
-                    _realizedElements.ItemsRemoved(e.OldStartingIndex, e.OldItems!.Count, _updateElementIndex, _recycleElement);
+                    _realizedElements.ItemsRemoved(e.OldStartingIndex, e.OldItems!.Count, _updateElementIndex, _recycleElementOnItemRemoved);
                     break;
                 case NotifyCollectionChangedAction.Reset:
-                    _realizedElements.RecycleAllElements(_recycleElement);
+                    _realizedElements.RecycleAllElements(_recycleElementOnItemRemoved);
                     break;
             }
-
-            InvalidateMeasure();
         }
 
         protected override IInputElement? GetControl(NavigationDirection direction, IInputElement? from, bool wrap)
@@ -314,6 +309,7 @@ private MeasureViewport CalculateMeasureViewport(IReadOnlyList<object?> items)
             var (lastIndex, _) = _realizedElements.GetIndexAt(viewportEnd);
             var estimatedElementSize = -1.0;
             var itemCount = items?.Count ?? 0;
+            var maxIndex = Math.Max(itemCount - 1, 0);
 
             if (firstIndex == -1)
             {
@@ -331,8 +327,8 @@ private MeasureViewport CalculateMeasureViewport(IReadOnlyList<object?> items)
 
             return new MeasureViewport
             {
-                firstIndex = MathUtilities.Clamp(firstIndex, 0, itemCount - 1),
-                lastIndex = MathUtilities.Clamp(lastIndex, 0, itemCount - 1),
+                firstIndex = MathUtilities.Clamp(firstIndex, 0, maxIndex),
+                lastIndex = MathUtilities.Clamp(lastIndex, 0, maxIndex),
                 viewportUStart = viewportStart,
                 viewportUEnd = viewportEnd,
                 startU = firstIndexU,
@@ -468,7 +464,6 @@ private Control GetOrCreateElement(IReadOnlyList<object?> items, int index)
             var generator = ItemContainerGenerator!;
             var item = items[index];
 
-
             if (_recyclePool?.Count > 0)
             {
                 var recycled = _recyclePool.Pop();
@@ -519,6 +514,24 @@ private void RecycleElement(Control element)
             }
         }
 
+        private void RecycleElementOnItemRemoved(Control element)
+        {
+            Debug.Assert(ItemContainerGenerator is not null);
+
+            if (element.IsSet(ItemIsOwnContainerProperty))
+            {
+                RemoveInternalChild(element);
+            }
+            else
+            {
+                ItemContainerGenerator!.ClearItemContainer(element);
+                _recyclePool ??= new();
+                _recyclePool.Push(element);
+                element.IsVisible = false;
+                element.GetObservable(Visual.VisualParentProperty).Subscribe(x => { });
+            }
+        }
+
         private void UpdateElementIndex(Control element, int oldIndex, int newIndex)
         {
             Debug.Assert(ItemContainerGenerator is not null);
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
index 5f21a7a8829..10cb5f8c6be 100644
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
@@ -12,6 +12,8 @@
 using Avalonia.VisualTree;
 using Xunit;
 
+#nullable enable
+
 namespace Avalonia.Controls.UnitTests
 {
     public class VirtualizingStackPanelTests
@@ -20,7 +22,6 @@ public class VirtualizingStackPanelTests
         public void Creates_Initial_Items()
         {
             using var app = App();
-
             var (target, scroll, itemsControl) = CreateTarget();
 
             Assert.Equal(1000, scroll.Extent.Height);
@@ -29,10 +30,35 @@ public void Creates_Initial_Items()
         }
 
         [Fact]
-        public void Scrolls_Down_One_Item()
+        public void Initializes_Initial_Control_Items()
+        {
+            using var app = App();
+            var items = Enumerable.Range(0, 100).Select(x => new Button { Width = 25, Height = 10});
+            var (target, scroll, itemsControl) = CreateTarget(items: items, useItemTemplate: false);
+
+            Assert.Equal(1000, scroll.Extent.Height);
+
+            AssertRealizedControlItems<Button>(target, itemsControl, 0, 10);
+        }
+
+        [Fact]
+        public void Creates_Reassigned_Items()
         {
             using var app = App();
+            var (target, scroll, itemsControl) = CreateTarget(items: Array.Empty<object>());
+
+            Assert.Empty(itemsControl.GetRealizedContainers());
 
+            itemsControl.Items = new[] { "foo", "bar" };
+            Layout(target);
+
+            AssertRealizedItems(target, itemsControl, 0, 2);
+        }
+
+        [Fact]
+        public void Scrolls_Down_One_Item()
+        {
+            using var app = App();
             var (target, scroll, itemsControl) = CreateTarget();
 
             scroll.Offset = new Vector(0, 10);
@@ -45,7 +71,6 @@ public void Scrolls_Down_One_Item()
         public void Scrolls_Down_More_Than_A_Page()
         {
             using var app = App();
-
             var (target, scroll, itemsControl) = CreateTarget();
 
             scroll.Offset = new Vector(0, 200);
@@ -55,12 +80,11 @@ public void Scrolls_Down_More_Than_A_Page()
         }
 
         [Fact]
-        public void Creates_Elements_For_Inserted_Item()
+        public void Creates_Elements_On_Item_Insert()
         {
             using var app = App();
-
             var (target, _, itemsControl) = CreateTarget();
-            var items = (IList)itemsControl.Items;
+            var items = (IList)itemsControl.Items!;
 
             Assert.Equal(10, target.GetRealizedElements().Count);
 
@@ -88,12 +112,11 @@ public void Creates_Elements_For_Inserted_Item()
         }
 
         [Fact]
-        public void Updates_Elements_On_Removed_Row()
+        public void Updates_Elements_On_Item_Remove()
         {
             using var app = App();
-
             var (target, _, itemsControl) = CreateTarget();
-            var items = (IList)itemsControl.Items;
+            var items = (IList)itemsControl.Items!;
 
             Assert.Equal(10, target.GetRealizedElements().Count);
 
@@ -118,10 +141,26 @@ public void Updates_Elements_On_Removed_Row()
             Assert.Equal(elements, target.GetRealizedElements());
         }
 
+        [Fact]
+        public void Removes_Control_Items_From_Panel_On_Item_Remove()
+        {
+            using var app = App();
+            var items = new ObservableCollection<Button>(Enumerable.Range(0, 100).Select(x => new Button { Width = 25, Height = 10 }));
+            var (target, scroll, itemsControl) = CreateTarget(items: items, useItemTemplate: false);
+
+            Assert.Equal(1000, scroll.Extent.Height);
+
+            var removed = items[1];
+            items.RemoveAt(1);
+
+            Assert.Null(removed.Parent);
+            Assert.Null(removed.VisualParent);
+        }
+
         private static IReadOnlyList<int> GetRealizedIndexes(VirtualizingStackPanel target, ItemsControl itemsControl)
         {
             return target.GetRealizedElements()
-                .Select(x => x is null ? -1 : itemsControl.ItemContainerGenerator.IndexFromContainer((Control)x))
+                .Select(x => x is null ? -1 : itemsControl.IndexFromContainer((Control)x))
                 .ToList();
         }
 
@@ -131,19 +170,43 @@ private static void AssertRealizedItems(
             int firstIndex,
             int count)
         {
-            var childIndexes = target.GetLogicalChildren()
-                .Select(x => itemsControl.ItemContainerGenerator.IndexFromContainer((Control)x))
+            Assert.All(target.GetRealizedContainers(), x => Assert.Same(target, x.VisualParent));
+            Assert.All(target.GetRealizedContainers(), x => Assert.Same(itemsControl, x.Parent));
+
+            var childIndexes = target.GetRealizedContainers()?
+                .Select(x => itemsControl.IndexFromContainer(x))
+                .Where(x => x >= 0)
+                .OrderBy(x => x)
+                .ToList();
+            Assert.Equal(Enumerable.Range(firstIndex, count), childIndexes);
+        }
+
+        private static void AssertRealizedControlItems<TContainer>(
+            VirtualizingStackPanel target,
+            ItemsControl itemsControl,
+            int firstIndex,
+            int count)
+        {
+            Assert.All(target.GetRealizedContainers(), x => Assert.IsType<TContainer>(x));
+            Assert.All(target.GetRealizedContainers(), x => Assert.Same(target, x.VisualParent));
+            Assert.All(target.GetRealizedContainers(), x => Assert.Same(itemsControl, x.Parent));
+
+            var childIndexes = target.GetRealizedContainers()?
+                .Select(x => itemsControl.IndexFromContainer(x))
                 .Where(x => x >= 0)
                 .OrderBy(x => x)
                 .ToList();
             Assert.Equal(Enumerable.Range(firstIndex, count), childIndexes);
         }
 
-        private static (VirtualizingStackPanel, ScrollViewer, ItemsControl) CreateTarget(int itemCount = 100)
+        private static (VirtualizingStackPanel, ScrollViewer, ItemsControl) CreateTarget(
+            IEnumerable<object>? items = null,
+            bool useItemTemplate = true)
         {
-            var items = new ObservableCollection<string>(Enumerable.Range(0, itemCount).Select(x => $"Item {x}"));
             var target = new VirtualizingStackPanel();
-            
+
+            items ??= new ObservableCollection<string>(Enumerable.Range(0, 100).Select(x => $"Item {x}"));
+
             var presenter = new ItemsPresenter
             {
                 [~ItemsPresenter.ItemsPanelProperty] = new TemplateBinding(ItemsPresenter.ItemsPanelProperty),
@@ -160,9 +223,11 @@ private static (VirtualizingStackPanel, ScrollViewer, ItemsControl) CreateTarget
                 Items = items,
                 Template = new FuncControlTemplate<ItemsControl>((_, _) => scroll),
                 ItemsPanel = new FuncTemplate<Panel>(() => target),
-                ItemTemplate = new FuncDataTemplate<string>((x, _) => new Canvas { Width = 100, Height = 10 }),
             };
 
+            if (useItemTemplate)
+                itemsControl.ItemTemplate = new FuncDataTemplate<object>((x, _) => new Canvas { Width = 100, Height = 10 });
+
             var root = new TestRoot(true, itemsControl);
             root.ClientSize = new(100, 100);
             root.LayoutManager.ExecuteInitialLayoutPass();

From 76b51cf2a90e85338bb6cefdf1f3551b1882862a Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 12 Dec 2022 17:15:56 +0100
Subject: [PATCH 55/64] Fix property name.

---
 src/Avalonia.Controls/ItemsControl.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 4e89c2da17f..f413cb4972d 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -65,7 +65,7 @@ public class ItemsControl : TemplatedControl, IChildIndexProvider
         /// Defines the <see cref="ItemsView"/> property.
         /// </summary>
         public static readonly DirectProperty<ItemsControl, ItemsSourceView> ItemsViewProperty =
-            AvaloniaProperty.RegisterDirect<ItemsControl, ItemsSourceView>(nameof(Items), o => o.ItemsView);
+            AvaloniaProperty.RegisterDirect<ItemsControl, ItemsSourceView>(nameof(ItemsView), o => o.ItemsView);
 
         /// <summary>
         /// Defines the <see cref="DisplayMemberBinding" /> property

From 54bc9ddeeb87cfd3ad0164728b52633a9bba7b37 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Tue, 13 Dec 2022 11:03:03 +0100
Subject: [PATCH 56/64] Fix adorners in DevTools.

---
 .../Diagnostics/Views/TreePageView.xaml       |  4 ++-
 .../Diagnostics/Views/TreePageView.xaml.cs    | 26 -------------------
 2 files changed, 3 insertions(+), 27 deletions(-)

diff --git a/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml b/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml
index 36bb880a14d..3ca3d0b60ee 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml
+++ b/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml
@@ -11,7 +11,9 @@
       <TreeView.DataTemplates>
         <TreeDataTemplate DataType="vm:TreeNode"
                           ItemsSource="{Binding Children}">
-          <StackPanel Orientation="Horizontal" Spacing="8">
+          <StackPanel Orientation="Horizontal" Spacing="8"
+                      PointerEntered="AddAdorner"
+                      PointerExited="RemoveAdorner">
             <TextBlock Text="{Binding Type}" FontWeight="{Binding FontWeight}"/>
             <TextBlock Text="{Binding Classes}"/>
             <TextBlock Foreground="Gray" Text="{Binding ElementName}"/>
diff --git a/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs b/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs
index d8feb579f05..1a4bb6170ae 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs
@@ -21,7 +21,6 @@ public TreePageView()
         {
             InitializeComponent();
             _tree = this.GetControl<TreeView>("tree");
-            ////_tree.ItemContainerGenerator.Index!.Materialized += TreeViewItemMaterialized;
 
             _adorner = new Panel
             {
@@ -102,30 +101,5 @@ private void InitializeComponent()
         {
             AvaloniaXamlLoader.Load(this);
         }
-
-        ////private void TreeViewItemMaterialized(object? sender, ItemContainerEventArgs e)
-        ////{
-        ////    var item = (TreeViewItem)e.Containers[0].ContainerControl;
-        ////    item.TemplateApplied += TreeViewItemTemplateApplied;
-        ////}
-
-        private void TreeViewItemTemplateApplied(object? sender, TemplateAppliedEventArgs e)
-        {
-            var item = (TreeViewItem)sender!;
-
-            // This depends on the default tree item template.
-            // We want to handle events in the item header but exclude events coming from children.
-            var header = item.FindDescendantOfType<Border>();
-
-            Debug.Assert(header != null);
-
-            if (header != null)
-            {
-                header.PointerEntered += AddAdorner;
-                header.PointerExited += RemoveAdorner;
-            }
-
-            item.TemplateApplied -= TreeViewItemTemplateApplied;
-        }
     }
 }

From 039fb905ad6b18ab939e5863b00f4ebed9939d4d Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Tue, 13 Dec 2022 13:04:32 +0100
Subject: [PATCH 57/64] Handle item move and replace.

---
 .../VirtualizingStackPanel.cs                 |  5 ++
 .../VirtualizingStackPanelTests.cs            | 58 +++++++++++++++++++
 2 files changed, 63 insertions(+)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index dba45b15051..6dec8c6327c 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -161,6 +161,11 @@ protected override void OnItemsChanged(IReadOnlyList<object?> items, NotifyColle
                 case NotifyCollectionChangedAction.Remove:
                     _realizedElements.ItemsRemoved(e.OldStartingIndex, e.OldItems!.Count, _updateElementIndex, _recycleElementOnItemRemoved);
                     break;
+                case NotifyCollectionChangedAction.Replace:
+                case NotifyCollectionChangedAction.Move:
+                    _realizedElements.ItemsRemoved(e.OldStartingIndex, e.OldItems!.Count, _updateElementIndex, _recycleElementOnItemRemoved);
+                    _realizedElements.ItemsInserted(e.NewStartingIndex, e.NewItems!.Count, _updateElementIndex);
+                    break;
                 case NotifyCollectionChangedAction.Reset:
                     _realizedElements.RecycleAllElements(_recycleElementOnItemRemoved);
                     break;
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
index 10cb5f8c6be..c20d4fa41af 100644
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
@@ -141,6 +141,64 @@ public void Updates_Elements_On_Item_Remove()
             Assert.Equal(elements, target.GetRealizedElements());
         }
 
+        [Fact]
+        public void Updates_Elements_On_Item_Replace()
+        {
+            using var app = App();
+            var (target, _, itemsControl) = CreateTarget();
+            var items = (ObservableCollection<string>)itemsControl.Items!;
+
+            Assert.Equal(10, target.GetRealizedElements().Count);
+
+            var toReplace = target.GetRealizedElements().ElementAt(2);
+            items[2] = "new";
+
+            // Container being replaced should have been recycled.
+            Assert.DoesNotContain(toReplace, target.GetRealizedElements());
+            Assert.False(toReplace!.IsVisible);
+
+            var indexes = GetRealizedIndexes(target, itemsControl);
+
+            // Item removed from realized elements at old position and space inserted at new position.
+            Assert.Equal(new[] { 0, 1, -1, 3, 4, 5, 6, 7, 8, 9 }, indexes);
+
+            Layout(target);
+
+            indexes = GetRealizedIndexes(target, itemsControl);
+
+            // After layout the missing container should have been created.
+            Assert.Equal(Enumerable.Range(0, 10), indexes);
+        }
+
+        [Fact]
+        public void Updates_Elements_On_Item_Move()
+        {
+            using var app = App();
+            var (target, _, itemsControl) = CreateTarget();
+            var items = (ObservableCollection<string>)itemsControl.Items!;
+
+            Assert.Equal(10, target.GetRealizedElements().Count);
+
+            var toMove = target.GetRealizedElements().ElementAt(2);
+            items.Move(2, 6);
+
+            // Container being moved should have been recycled.
+            Assert.DoesNotContain(toMove, target.GetRealizedElements());
+            Assert.False(toMove!.IsVisible);
+
+            var indexes = GetRealizedIndexes(target, itemsControl);
+
+            // Item removed from realized elements at old position and space inserted at new position.
+            Assert.Equal(new[] { 0, 1, 2, 3, 4, 5, -1, 7, 8, 9 }, indexes);
+
+            Layout(target);
+
+            indexes = GetRealizedIndexes(target, itemsControl);
+
+            // After layout the missing container should have been created.
+            Assert.Equal(Enumerable.Range(0, 10), indexes);
+        }
+
         [Fact]
         public void Removes_Control_Items_From_Panel_On_Item_Remove()
         {

From 17f7541fdd39943e705975d766be480a558117b7 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Tue, 13 Dec 2022 14:34:32 +0100
Subject: [PATCH 58/64] Fix selection in combination with move.

---
 .../Presenters/PanelContainerGenerator.cs     |  7 +-
 .../Selection/SelectionModel.cs               |  1 +
 .../Selection/SelectionNodeBase.cs            |  1 +
 .../Primitives/SelectingItemsControlTests.cs  | 72 +++++++++++++++++++
 .../Selection/SelectionModelTests_Multiple.cs | 50 +++++++++++++
 .../Selection/SelectionModelTests_Single.cs   | 46 ++++++++++++
 6 files changed, 173 insertions(+), 4 deletions(-)

diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index 1c94c29a356..a2df8c3e5f0 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -81,9 +81,11 @@ void Remove(int index, int count)
             {
                 for (var i = 0; i < count; ++i)
                 {
-                    var c = children[i];
+                    var c = children[index + i];
                     if (!c.IsSet(ItemIsOwnContainerProperty))
                         itemsControl.RemoveLogicalChild(children[i + index]);
+                    else
+                        generator.ClearItemContainer(c);
                 }
 
                 children.RemoveRange(index, count);
@@ -103,9 +105,6 @@ void Remove(int index, int count)
                     Remove(e.OldStartingIndex, e.OldItems!.Count);
                     break;
                 case NotifyCollectionChangedAction.Replace:
-                    Remove(e.OldStartingIndex, e.OldItems!.Count);
-                    Add(e.NewStartingIndex, e.NewItems!);
-                    break;
                 case NotifyCollectionChangedAction.Move:
                     Remove(e.OldStartingIndex, e.OldItems!.Count);
                     Add(e.NewStartingIndex, e.NewItems!);
diff --git a/src/Avalonia.Controls/Selection/SelectionModel.cs b/src/Avalonia.Controls/Selection/SelectionModel.cs
index 9bbddfcbb2a..affe762ea77 100644
--- a/src/Avalonia.Controls/Selection/SelectionModel.cs
+++ b/src/Avalonia.Controls/Selection/SelectionModel.cs
@@ -439,6 +439,7 @@ private protected override void OnSourceCollectionChanged(NotifyCollectionChange
 
             if ((e.Action == NotifyCollectionChangedAction.Remove && e.OldStartingIndex <= oldSelectedIndex) ||
                 (e.Action == NotifyCollectionChangedAction.Replace && e.OldStartingIndex == oldSelectedIndex) ||
+                (e.Action == NotifyCollectionChangedAction.Move && e.OldStartingIndex == oldSelectedIndex) ||
                 e.Action == NotifyCollectionChangedAction.Reset)
             {
                 RaisePropertyChanged(nameof(SelectedItem));
diff --git a/src/Avalonia.Controls/Selection/SelectionNodeBase.cs b/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
index 01b89325af5..69a651aca6d 100644
--- a/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
+++ b/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
@@ -256,6 +256,7 @@ private protected virtual void OnSourceCollectionChanged(NotifyCollectionChanged
                         break;
                     }
                 case NotifyCollectionChangedAction.Replace:
+                case NotifyCollectionChangedAction.Move:
                     {
                         var removeChange = OnItemsRemoved(e.OldStartingIndex, e.OldItems!);
                         var addChange = OnItemsAdded(e.NewStartingIndex, e.NewItems!);
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
index dbea9f79b80..1775d7ef70f 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
@@ -637,6 +637,78 @@ public void Removing_Selected_Item_Should_Clear_Selection_With_BeginInit()
             Assert.False(items.Single().IsSelected);
         }
 
+        [Fact]
+        public void Replacing_Selected_Item_Should_Clear_Selection()
+        {
+            var items = new AvaloniaList<Item>
+            {
+                new Item(),
+                new Item(),
+            };
+
+            var target = new SelectingItemsControl
+            {
+                Items = items,
+                Template = Template(),
+            };
+
+            Prepare(target);
+            target.SelectedIndex = 1;
+
+            Assert.Equal(items[1], target.SelectedItem);
+            Assert.Equal(1, target.SelectedIndex);
+
+            SelectionChangedEventArgs receivedArgs = null;
+
+            target.SelectionChanged += (_, args) => receivedArgs = args;
+
+            var removed = items[1];
+            items[1] = new Item();
+
+            Assert.Null(target.SelectedItem);
+            Assert.Equal(-1, target.SelectedIndex);
+            Assert.NotNull(receivedArgs);
+            Assert.Empty(receivedArgs.AddedItems);
+            Assert.Equal(new[] { removed }, receivedArgs.RemovedItems);
+            Assert.All(items, x => Assert.False(x.IsSelected));
+        }
+
+        [Fact]
+        public void Moving_Selected_Item_Should_Clear_Selection()
+        {
+            var items = new AvaloniaList<Item>
+            {
+                new Item(),
+                new Item(),
+            };
+
+            var target = new SelectingItemsControl
+            {
+                Items = items,
+                Template = Template(),
+            };
+
+            Prepare(target);
+            target.SelectedIndex = 1;
+
+            Assert.Equal(items[1], target.SelectedItem);
+            Assert.Equal(1, target.SelectedIndex);
+
+            SelectionChangedEventArgs receivedArgs = null;
+
+            target.SelectionChanged += (_, args) => receivedArgs = args;
+
+            var removed = items[1];
+            items.Move(1, 0);
+
+            Assert.Null(target.SelectedItem);
+            Assert.Equal(-1, target.SelectedIndex);
+            Assert.NotNull(receivedArgs);
+            Assert.Empty(receivedArgs.AddedItems);
+            Assert.Equal(new[] { removed }, receivedArgs.RemovedItems);
+            Assert.All(items, x => Assert.False(x.IsSelected));
+        }
+
         [Fact]
         public void Resetting_Items_Collection_Should_Clear_Selection()
         {
diff --git a/tests/Avalonia.Controls.UnitTests/Selection/SelectionModelTests_Multiple.cs b/tests/Avalonia.Controls.UnitTests/Selection/SelectionModelTests_Multiple.cs
index 68bdbe51e83..dbbff91fcc6 100644
--- a/tests/Avalonia.Controls.UnitTests/Selection/SelectionModelTests_Multiple.cs
+++ b/tests/Avalonia.Controls.UnitTests/Selection/SelectionModelTests_Multiple.cs
@@ -1259,6 +1259,56 @@ public void Replacing_Selected_Item_Updates_State()
                 Assert.Equal(0, indexesChangedRaised);
             }
 
+            [Fact]
+            public void Moving_Selected_Item_Updates_State()
+            {
+                var target = CreateTarget();
+                var data = (AvaloniaList<string>)target.Source!;
+                var selectionChangedRaised = 0;
+                var selectedIndexRaised = 0;
+                var selectedItemRaised = 0;
+                var indexesChangedRaised = 0;
+
+                target.Source = data;
+                target.SelectRange(1, 4);
+
+                target.PropertyChanged += (s, e) =>
+                {
+                    if (e.PropertyName == nameof(target.SelectedIndex))
+                    {
+                        ++selectedIndexRaised;
+                    }
+
+                    if (e.PropertyName == nameof(target.SelectedItem))
+                    {
+                        ++selectedItemRaised;
+                    }
+                };
+
+                target.IndexesChanged += (s, e) => ++indexesChangedRaised;
+
+                target.SelectionChanged += (s, e) =>
+                {
+                    Assert.Empty(e.DeselectedIndexes);
+                    Assert.Equal(new[] { "bar" }, e.DeselectedItems);
+                    Assert.Empty(e.SelectedIndexes);
+                    Assert.Empty(e.SelectedItems);
+                    ++selectionChangedRaised;
+                };
+
+                data.Move(1, 0);
+
+                Assert.Equal(2, target.SelectedIndex);
+                Assert.Equal(new[] { 2, 3, 4 }, target.SelectedIndexes);
+                Assert.Equal("baz", target.SelectedItem);
+                Assert.Equal(new[] { "baz", "qux", "quux" }, target.SelectedItems);
+                Assert.Equal(2, target.AnchorIndex);
+                Assert.Equal(1, selectionChangedRaised);
+                Assert.Equal(1, selectedIndexRaised);
+                Assert.Equal(1, selectedItemRaised);
+                Assert.Equal(0, indexesChangedRaised);
+            }
+
             [Fact]
             public void Resetting_Source_Updates_State()
             {
diff --git a/tests/Avalonia.Controls.UnitTests/Selection/SelectionModelTests_Single.cs b/tests/Avalonia.Controls.UnitTests/Selection/SelectionModelTests_Single.cs
index 668af3b5d7c..c5370f07490 100644
--- a/tests/Avalonia.Controls.UnitTests/Selection/SelectionModelTests_Single.cs
+++ b/tests/Avalonia.Controls.UnitTests/Selection/SelectionModelTests_Single.cs
@@ -1079,6 +1079,52 @@ public void Replacing_Selected_Item_Updates_State()
                 Assert.Equal(1, selectedItemRaised);
             }
 
+            [Fact]
+            public void Moving_Selected_Item_Updates_State()
+            {
+                var target = CreateTarget();
+                var data = (AvaloniaList<string>)target.Source!;
+                var selectionChangedRaised = 0;
+                var selectedIndexRaised = 0;
+                var selectedItemRaised = 0;
+
+                target.Source = data;
+                target.Select(1);
+
+                target.PropertyChanged += (s, e) =>
+                {
+                    if (e.PropertyName == nameof(target.SelectedIndex))
+                    {
+                        ++selectedIndexRaised;
+                    }
+
+                    if (e.PropertyName == nameof(target.SelectedItem))
+                    {
+                        ++selectedItemRaised;
+                    }
+                };
+
+                target.SelectionChanged += (s, e) =>
+                {
+                    Assert.Empty(e.DeselectedIndexes);
+                    Assert.Equal(new[] { "bar" }, e.DeselectedItems);
+                    Assert.Empty(e.SelectedIndexes);
+                    Assert.Empty(e.SelectedItems);
+                    ++selectionChangedRaised;
+                };
+
+                data.Move(1, 0);
+
+                Assert.Equal(-1, target.SelectedIndex);
+                Assert.Empty(target.SelectedIndexes);
+                Assert.Null(target.SelectedItem);
+                Assert.Empty(target.SelectedItems);
+                Assert.Equal(-1, target.AnchorIndex);
+                Assert.Equal(1, selectionChangedRaised);
+                Assert.Equal(1, selectedIndexRaised);
+                Assert.Equal(1, selectedItemRaised);
+            }
+
             [Fact]
             public void Resetting_Source_Updates_State()
             {

From 2b02afce36deb0747aca8b1a331fab5d99a984fb Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Tue, 13 Dec 2022 17:43:05 +0100
Subject: [PATCH 59/64] Added ItemsPanelRoot for WPF/UWP compat.

---
 src/Avalonia.Controls/ItemsControl.cs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index f413cb4972d..d19a04eb210 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -163,6 +163,11 @@ public IDataTemplate? ItemTemplate
         /// </summary>
         public ItemsPresenter? Presenter { get; private set; }
 
+        /// <summary>
+        /// Gets the <see cref="Panel"/> specified by <see cref="ItemsPanel"/>.
+        /// </summary>
+        public Panel? ItemsPanelRoot => Presenter?.Panel;
+
         /// <summary>
         /// Gets a standardized view over <see cref="Items"/>.
         /// </summary>

From 0dcf836a9058e2ea7c4c33d1560c22cc4651bfd2 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 9 Jan 2023 17:02:38 +0100
Subject: [PATCH 60/64] Remove debug code.

---
 src/Avalonia.Controls/VirtualizingStackPanel.cs | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 6dec8c6327c..c3bf7a3e5df 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -533,7 +533,6 @@ private void RecycleElementOnItemRemoved(Control element)
                 _recyclePool ??= new();
                 _recyclePool.Push(element);
                 element.IsVisible = false;
-                element.GetObservable(Visual.VisualParentProperty).Subscribe(x => { });
             }
         }
 

From 1ef4df181b299278a60600ee75a9114314f99e8a Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 9 Jan 2023 17:05:50 +0100
Subject: [PATCH 61/64] Fix nits.

---
 src/Avalonia.Controls/Generators/ItemContainerGenerator.cs | 2 +-
 src/Avalonia.Controls/VirtualizingStackPanel.cs            | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
index b6f54d51ebc..57ed67b508d 100644
--- a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
+++ b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
@@ -29,7 +29,7 @@ namespace Avalonia.Controls.Generators
     /// </remarks>
     public class ItemContainerGenerator
     {
-        private ItemsControl _owner;
+        private readonly ItemsControl _owner;
 
         internal ItemContainerGenerator(ItemsControl owner) => _owner = owner;
 
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index c3bf7a3e5df..6c88e6e441a 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -127,7 +127,7 @@ protected override Size ArrangeOverride(Size finalSize)
                 {
                     var e = _realizedElements.Elements[i];
 
-                    if (e is object)
+                    if (e is not null)
                     {
                         var sizeU = _realizedElements.SizeU[i];
                         var rect = orientation == Orientation.Horizontal ?
@@ -375,7 +375,7 @@ private Rect EstimateViewport()
 
             while (c is not null)
             {
-                if (!c.Bounds.IsEmpty && c.TransformToVisual(this) is Matrix transform)
+                if (!c.Bounds.IsDefault && c.TransformToVisual(this) is Matrix transform)
                 {
                     viewport = new Rect(0, 0, c.Bounds.Width, c.Bounds.Height)
                         .TransformToAABB(transform);
@@ -990,7 +990,7 @@ public void RecycleAllElements(Action<Control> recycleElement)
 
                 foreach (var e in _elements)
                 {
-                    if (e is object)
+                    if (e is not null)
                         recycleElement(e);
                 }
 

From a9fd9f4474b205a5f460e1bce19fe0506e315d80 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 13 Jan 2023 10:56:52 +0100
Subject: [PATCH 62/64] A few more tests.

Trying to get a repro for an issue seen with DataBox but so far unable to repro in a unit test. Anyway, these tests should be useful.
---
 .../ListBoxTests.cs                           | 85 +++++++++++++++++++
 .../VirtualizingStackPanelTests.cs            | 12 +++
 2 files changed, 97 insertions(+)

diff --git a/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs b/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
index cc824876ac5..3f1a3b6342c 100644
--- a/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
@@ -1,5 +1,7 @@
 using System;
+using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Collections.Specialized;
 using System.Linq;
 using System.Reactive.Subjects;
 using Avalonia.Collections;
@@ -663,6 +665,71 @@ public void SelectedItem_Validation()
             Assert.True(DataValidationErrors.GetErrors(target).SequenceEqual(new[] { exception }));
         }
 
+        [Fact]
+        public void Handles_Resetting_Items()
+        {
+            var items = new ResettingCollection(100);
+            var target = new ListBox
+            {
+                Template = ListBoxTemplate(),
+                Items = items,
+                ItemTemplate = new FuncDataTemplate<string>((_, __) => new Canvas { Height = 10 }),
+            };
+
+            Prepare(target);
+
+            var realized = target.GetRealizedContainers()
+                .Cast<ListBoxItem>()
+                .Select(x => (string)x.DataContext)
+                .ToList();
+
+            Assert.Equal(Enumerable.Range(0, 10).Select(x => $"Item{x}"), realized);
+
+            items.Reverse();
+            Layout(target);
+
+            realized = target.GetRealizedContainers()
+                .Cast<ListBoxItem>()
+                .Select(x => (string)x.DataContext)
+                .ToList();
+
+            Assert.Equal(Enumerable.Range(0, 10).Select(x => $"Item{99 - x}"), realized);
+        }
+
+        [Fact]
+        public void Handles_Resetting_Items_With_Existing_Selection_And_AutoScrollToSelectedItem()
+        {
+            var items = new ResettingCollection(100);
+            var target = new ListBox
+            {
+                Template = ListBoxTemplate(),
+                Items = items,
+                ItemTemplate = new FuncDataTemplate<string>((_, __) => new Canvas { Height = 10 }),
+                AutoScrollToSelectedItem = true,
+                SelectedIndex = 1,
+            };
+
+            Prepare(target);
+
+            var realized = target.GetRealizedContainers()
+                .Cast<ListBoxItem>()
+                .Select(x => (string)x.DataContext)
+                .ToList();
+
+            Assert.Equal(Enumerable.Range(0, 10).Select(x => $"Item{x}"), realized);
+
+            items.Reverse();
+            Layout(target);
+
+            realized = target.GetRealizedContainers()
+                .Cast<ListBoxItem>()
+                .Select(x => (string)x.DataContext)
+                .ToList();
+
+            // "Item1" should remain selected, and now be at the bottom of the viewport.
+            Assert.Equal(Enumerable.Range(0, 10).Select(x => $"Item{10 - x}"), realized);
+        }
+
         private static void RaiseKeyEvent(ListBox listBox, Key key, KeyModifiers inputModifiers = 0)
         {
             listBox.RaiseEvent(new KeyEventArgs
@@ -711,5 +778,23 @@ public void WrapSelection_Should_Wrap()
                 Assert.Equal(true, first.IsSelected);
             }
         }
+
+        private class ResettingCollection : List<string>, INotifyCollectionChanged
+        {
+            public ResettingCollection(int itemCount)
+            {
+                AddRange(Enumerable.Range(0, itemCount).Select(x => $"Item{x}"));
+            }
+
+            public new void Reverse()
+            {
+                base.Reverse();
+                CollectionChanged?.Invoke(
+                    this,
+                    new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+            }
+
+            public event NotifyCollectionChangedEventHandler CollectionChanged;
+        }
     }
 }
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
index c20d4fa41af..aa521c0d379 100644
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
@@ -2,6 +2,7 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Collections.Specialized;
 using System.Linq;
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Templates;
@@ -79,6 +80,17 @@ public void Scrolls_Down_More_Than_A_Page()
             AssertRealizedItems(target, itemsControl, 20, 10);
         }
 
+        [Fact]
+        public void Scrolls_To_Index()
+        {
+            using var app = App();
+            var (target, scroll, itemsControl) = CreateTarget();
+
+            target.ScrollIntoView(20);
+
+            AssertRealizedItems(target, itemsControl, 11, 10);
+        }
+
         [Fact]
         public void Creates_Elements_On_Item_Insert()
         {

From 8600f306e01506567cf641e1147375eb47512404 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 13 Jan 2023 11:16:23 +0100
Subject: [PATCH 63/64] Add redundancy for a problem I can't repro in tests.

There's a problem with `DataBox` that I can't repro in a unit test. Add some redundancy such that if we're still waiting for a viewport update after carrying out a layout pass, force another layout.
---
 src/Avalonia.Controls/VirtualizingStackPanel.cs | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 6c88e6e441a..45f1a02a24d 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -277,12 +277,25 @@ protected override void OnItemsChanged(IReadOnlyList<object?> items, NotifyColle
                     _isWaitingForViewportUpdate = false;
                 }
 
-                // Try to bring the item into view and do a layout pass.
+                // Try to bring the item into view.
                 _anchorElement.BringIntoView();
 
+                // If the viewport does not contain the item to scroll to, set _isWaitingForViewportUpdate:
+                // this should cause the following chain of events:
+                // - Measure is first done with the old viewport (which will be a no-op, see MeasureOverride)
+                // - The viewport is then updated by the layout system which invalidates our measure
+                // - Measure is then done with the new viewport.
                 _isWaitingForViewportUpdate = !_viewport.Contains(rect);
                 root.LayoutManager.ExecuteLayoutPass();
-                _isWaitingForViewportUpdate = false;
+
+                // If for some reason the layout system didn't give us a new viewport during the layout, we
+                // need to do another layout pass as the one that took place was a no-op.
+                if (_isWaitingForViewportUpdate)
+                {
+                    _isWaitingForViewportUpdate = false;
+                    InvalidateMeasure();
+                    root.LayoutManager.ExecuteLayoutPass();
+                }
 
                 var result = _anchorElement;
                 _anchorElement = null;

From d0f479d80cf4f805f2357042fd4f3138f7034d42 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 13 Jan 2023 13:29:30 +0100
Subject: [PATCH 64/64] Don't recycle focused element.

Fixes #9269
---
 .../VirtualizingStackPanel.cs                 | 56 ++++++++++++++++---
 .../VirtualizingStackPanelTests.cs            | 53 +++++++++++++++++-
 2 files changed, 99 insertions(+), 10 deletions(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 45f1a02a24d..3f539ce198f 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -26,7 +26,7 @@ public class VirtualizingStackPanel : VirtualizingPanel
             AvaloniaProperty.RegisterAttached<VirtualizingStackPanel, Control, bool>("ItemIsOwnContainer");
 
         private static readonly Rect s_invalidViewport = new(double.PositiveInfinity, double.PositiveInfinity, 0, 0);
-        private readonly Action<Control> _recycleElement;
+        private readonly Action<Control, int> _recycleElement;
         private readonly Action<Control> _recycleElementOnItemRemoved;
         private readonly Action<Control, int, int> _updateElementIndex;
         private int _anchorIndex = -1;
@@ -38,6 +38,8 @@ public class VirtualizingStackPanel : VirtualizingPanel
         private RealizedElementList? _realizedElements;
         private Rect _viewport = s_invalidViewport;
         private Stack<Control>? _recyclePool;
+        private Control? _unrealizedFocusedElement;
+        private int _unrealizedFocusedIndex = -1;
 
         public VirtualizingStackPanel()
         {
@@ -167,7 +169,7 @@ protected override void OnItemsChanged(IReadOnlyList<object?> items, NotifyColle
                     _realizedElements.ItemsInserted(e.NewStartingIndex, e.NewItems!.Count, _updateElementIndex);
                     break;
                 case NotifyCollectionChangedAction.Reset:
-                    _realizedElements.RecycleAllElements(_recycleElementOnItemRemoved);
+                    _realizedElements.ItemsReset(_recycleElementOnItemRemoved);
                     break;
             }
         }
@@ -482,6 +484,13 @@ private Control GetOrCreateElement(IReadOnlyList<object?> items, int index)
             var generator = ItemContainerGenerator!;
             var item = items[index];
 
+            if (_unrealizedFocusedIndex == index)
+            {
+                var element = _unrealizedFocusedElement;
+                _unrealizedFocusedElement = null;
+                _unrealizedFocusedIndex = -1;
+                return element;
+            }
             if (_recyclePool?.Count > 0)
             {
                 var recycled = _recyclePool.Pop();
@@ -515,7 +524,7 @@ private double GetOrEstimateElementPosition(int index)
             return index * estimatedElementSize;
         }
 
-        private void RecycleElement(Control element)
+        private void RecycleElement(Control element, int index)
         {
             Debug.Assert(ItemContainerGenerator is not null);
             
@@ -523,6 +532,11 @@ private void RecycleElement(Control element)
             {
                 element.IsVisible = false;
             }
+            else if (element.IsKeyboardFocusWithin)
+            {
+                _unrealizedFocusedElement = element;
+                _unrealizedFocusedIndex = index;
+            }
             else
             {
                 ItemContainerGenerator!.ClearItemContainer(element);
@@ -932,12 +946,33 @@ public void ItemsRemoved(
                 }
             }
 
+            /// <summary>
+            /// Recycles all elements in response to the source collection being reset.
+            /// </summary>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void ItemsReset(Action<Control> recycleElement)
+            {
+                if (_elements is null || _elements.Count == 0)
+                    return;
+
+                foreach (var e in _elements)
+                {
+                    if (e is not null)
+                        recycleElement(e);
+                }
+
+                _startU = _firstIndex = 0;
+                _elements?.Clear();
+                _sizes?.Clear();
+
+            }
+
             /// <summary>
             /// Recycles elements before a specific index.
             /// </summary>
             /// <param name="index">The index in the source collection of new first element.</param>
             /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void RecycleElementsBefore(int index, Action<Control> recycleElement)
+            public void RecycleElementsBefore(int index, Action<Control, int> recycleElement)
             {
                 if (index <= FirstIndex || _elements is null || _elements.Count == 0)
                     return;
@@ -953,7 +988,7 @@ public void RecycleElementsBefore(int index, Action<Control> recycleElement)
                     for (var i = 0; i < endIndex; ++i)
                     {
                         if (_elements[i] is Control e)
-                            recycleElement(e);
+                            recycleElement(e, i + FirstIndex);
                     }
 
                     _elements.RemoveRange(0, endIndex);
@@ -967,7 +1002,7 @@ public void RecycleElementsBefore(int index, Action<Control> recycleElement)
             /// </summary>
             /// <param name="index">The index in the source collection of new last element.</param>
             /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void RecycleElementsAfter(int index, Action<Control> recycleElement)
+            public void RecycleElementsAfter(int index, Action<Control, int> recycleElement)
             {
                 if (index >= LastIndex || _elements is null || _elements.Count == 0)
                     return;
@@ -984,7 +1019,7 @@ public void RecycleElementsAfter(int index, Action<Control> recycleElement)
                     for (var i = startIndex; i < count; ++i)
                     {
                         if (_elements[i] is Control e)
-                            recycleElement(e);
+                            recycleElement(e, i + FirstIndex);
                     }
 
                     _elements.RemoveRange(startIndex, _elements.Count - startIndex);
@@ -996,15 +1031,18 @@ public void RecycleElementsAfter(int index, Action<Control> recycleElement)
             /// Recycles all realized elements.
             /// </summary>
             /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void RecycleAllElements(Action<Control> recycleElement)
+            public void RecycleAllElements(Action<Control, int> recycleElement)
             {
                 if (_elements is null || _elements.Count == 0)
                     return;
 
+                var i = FirstIndex;
+
                 foreach (var e in _elements)
                 {
                     if (e is not null)
-                        recycleElement(e);
+                        recycleElement(e, i);
+                    ++i;
                 }
 
                 _startU = _firstIndex = 0;
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
index aa521c0d379..f1dd874c712 100644
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
@@ -227,6 +227,57 @@ public void Removes_Control_Items_From_Panel_On_Item_Remove()
             Assert.Null(removed.VisualParent);
         }
 
+        [Fact]
+        public void Does_Not_Recycle_Focused_Element()
+        {
+            using var app = App();
+            var (target, scroll, itemsControl) = CreateTarget();
+
+            target.GetRealizedElements().First()!.Focus();
+            Assert.True(target.GetRealizedElements().First()!.IsKeyboardFocusWithin);
+
+            scroll.Offset = new Vector(0, 200);
+            Layout(target);
+
+            Assert.All(target.GetRealizedElements(), x => Assert.False(x!.IsKeyboardFocusWithin));
+        }
+
+        [Fact]
+        public void Removing_Item_Of_Focused_Element_Clears_Focus()
+        {
+            using var app = App();
+            var (target, scroll, itemsControl) = CreateTarget();
+
+            var focused = target.GetRealizedElements().First()!;
+            focused.Focus();
+            Assert.True(focused.IsKeyboardFocusWithin);
+
+            scroll.Offset = new Vector(0, 200);
+            Layout(target);
+
+            Assert.All(target.GetRealizedElements(), x => Assert.False(x!.IsKeyboardFocusWithin));
+            Assert.All(target.GetRealizedElements(), x => Assert.NotSame(focused, x));
+        }
+
+        [Fact]
+        public void Scrolling_Back_To_Focused_Element_Uses_Correct_Element()
+        {
+            using var app = App();
+            var (target, scroll, itemsControl) = CreateTarget();
+
+            var focused = target.GetRealizedElements().First()!;
+            focused.Focus();
+            Assert.True(focused.IsKeyboardFocusWithin);
+
+            scroll.Offset = new Vector(0, 200);
+            Layout(target);
+
+            scroll.Offset = new Vector(0, 0);
+            Layout(target);
+
+            Assert.Same(focused, target.GetRealizedElements().First());
+        }
+
         private static IReadOnlyList<int> GetRealizedIndexes(VirtualizingStackPanel target, ItemsControl itemsControl)
         {
             return target.GetRealizedElements()
@@ -326,6 +377,6 @@ private static IControlTemplate ScrollViewerTemplate()
                 }.RegisterInNameScope(ns));
         }
 
-        private static IDisposable App() => UnitTestApplication.Start();
+        private static IDisposable App() => UnitTestApplication.Start(TestServices.RealFocus);
     }
 }