Fix Modal page offset measuring for AdjustPan and AdjustResize (#12661)

* Watch for margin

* Fix modal margins and measuring when soft keyboard opens

* - fix offsets

* - force tests to setup testing scenario

* Update ModalNavigationManager.Android.cs

* - add additional comments

src/Controls/src/Core/Compatibility/Handlers/Shell/Android/ShellFlyoutTemplatedContentRenderer.cs

@@ -122,21 +122,17 @@ protected virtual void LoadView(IShellContext shellContext)
 				// so we want to delay loading to the latest possible point in time so
 				// it doesn't delay initial startup.
 				GenericGlobalLayoutListener ggll = null;
-				ggll = new GenericGlobalLayoutListener(InitialLoad);
-				sfl.ViewTreeObserver.AddOnGlobalLayoutListener(ggll);
+				ggll = new GenericGlobalLayoutListener(InitialLoad, sfl);
 
-				void InitialLoad()
+				void InitialLoad(GenericGlobalLayoutListener listener, AView view)
 				{
 					OnFlyoutViewLayoutChanging();
 
 					if (_flyoutContentView == null || ggll == null)
 						return;
 
-					var listener = ggll;
 					ggll = null;
-
-					// Once initial load has finished let's just attach to Layout Changing
-					sfl.ViewTreeObserver.RemoveOnGlobalLayoutListener(listener);
+					listener.Invalidate();
 					sfl.LayoutChanging += OnFlyoutViewLayoutChanging;
 				}
 			}

src/Controls/src/Core/Compatibility/Handlers/Shell/Android/ShellToolbarTracker.cs

@@ -76,8 +76,7 @@ public ShellToolbarTracker(IShellContext shellContext, AToolbar toolbar, DrawerL
 			_drawerLayout = drawerLayout ?? throw new ArgumentNullException(nameof(drawerLayout));
 			_appBar = _platformToolbar.Parent.GetParentOfType<AppBarLayout>();
 
-			_globalLayoutListener = new GenericGlobalLayoutListener(() => UpdateNavBarHasShadow(Page));
-			_appBar.ViewTreeObserver.AddOnGlobalLayoutListener(_globalLayoutListener);
+			_globalLayoutListener = new GenericGlobalLayoutListener((_,_) => UpdateNavBarHasShadow(Page), _appBar);
 			_platformToolbar.SetNavigationOnClickListener(this);
 			((IShellController)ShellContext.Shell).AddFlyoutBehaviorObserver(this);
 			ShellContext.Shell.Toolbar.PropertyChanged += OnToolbarPropertyChanged;
@@ -174,9 +173,6 @@ protected override void Dispose(bool disposing)
 
 			if (disposing)
 			{
-				if (_appBar.IsAlive() && _appBar.ViewTreeObserver.IsAlive())
-					_appBar.ViewTreeObserver.RemoveOnGlobalLayoutListener(_globalLayoutListener);
-
 				_globalLayoutListener.Invalidate();
 
 				if (_backButtonBehavior != null)

src/Controls/src/Core/Platform/Android/GenericGlobalLayoutListener.cs

@@ -1,21 +1,31 @@
 using System;
 using Android.Views;
+using AView = Android.Views.View;
 using Object = Java.Lang.Object;
 
 namespace Microsoft.Maui.Controls.Platform
 {
 	internal class GenericGlobalLayoutListener : Object, ViewTreeObserver.IOnGlobalLayoutListener
 	{
-		Action _callback;
+		Action<GenericGlobalLayoutListener, AView?>? _callback;
+		WeakReference<AView>? _targetView;
 
-		public GenericGlobalLayoutListener(Action callback)
+		public GenericGlobalLayoutListener(Action<GenericGlobalLayoutListener, AView?> callback, AView? targetView = null)
 		{
 			_callback = callback;
+
+			if (targetView?.ViewTreeObserver != null)
+			{
+				_targetView = new WeakReference<AView>(targetView);
+				targetView.ViewTreeObserver.AddOnGlobalLayoutListener(this);
+			}
 		}
 
 		public void OnGlobalLayout()
 		{
-			_callback?.Invoke();
+			AView? targetView = null;
+			_targetView?.TryGetTarget(out targetView);
+			_callback?.Invoke(this, targetView);
 		}
 
 		protected override void Dispose(bool disposing)
@@ -29,6 +39,16 @@ protected override void Dispose(bool disposing)
 		internal void Invalidate()
 		{
 			_callback = null;
+
+			if (_targetView != null &&
+				_targetView.TryGetTarget(out var targetView) &&
+				targetView.IsAlive() &&
+				targetView.ViewTreeObserver != null)
+			{
+				targetView.ViewTreeObserver.RemoveOnGlobalLayoutListener(this);
+			}
+
+			_targetView = null;
 		}
 	}
 }

src/Controls/src/Core/Platform/ModalNavigationManager/ModalNavigationManager.Android.cs

@@ -8,30 +8,39 @@
 using Android.Views.Animations;
 using AndroidX.Activity;
 using AndroidX.AppCompat.App;
+using AndroidX.AppCompat.Widget;
+using AndroidX.Core.View;
 using AndroidX.Fragment.App;
 using Microsoft.Maui.Graphics;
+using Microsoft.Maui.Platform;
 using AView = Android.Views.View;
 
 namespace Microsoft.Maui.Controls.Platform
 {
 	internal partial class ModalNavigationManager
 	{
-		ViewGroup GetModalParentView()
+		ViewGroup? _modalParentView;
+
+		// This is only here for the device tests to use.
+		// With the device tests we have a `FakeActivityRootView` and a `WindowTestFragment`
+		// that we use to replicate the `DecorView` and `MainActivity`
+		// The tests will set this to the `FakeActivityRootView` so that the `modals`
+		// are part of the correct testing space.
+		// If/When we move to opening new activities we can remove this code.
+		internal void SetModalParentView(ViewGroup viewGroup)
 		{
-			var currentRootView = GetCurrentRootView() as ViewGroup;
-
-			if (_window?.PlatformActivity?.GetWindow() == _window)
-			{
-				currentRootView = _window?.PlatformActivity?.Window?.DecorView as ViewGroup;
-			}
+			_modalParentView = viewGroup;
+		}
 
-			return currentRootView ??
+		ViewGroup GetModalParentView()
+		{
+			return _modalParentView ??
+				_window?.PlatformActivity?.Window?.DecorView as ViewGroup ??
 				throw new InvalidOperationException("Root View Needs to be set");
 		}
 
 		bool _navAnimationInProgress;
 		internal const string CloseContextActionsSignalName = "Xamarin.CloseContextActions";
-		Page CurrentPage => _navModel.CurrentPage;
 
 		// AFAICT this is specific to ListView and Context Items
 		internal bool NavAnimationInProgress
@@ -198,6 +207,10 @@ sealed class ModalContainer : ViewGroup
 			ModalFragment _modalFragment;
 			FragmentManager? _fragmentManager;
 			NavigationRootManager? NavigationRootManager => _modalFragment.NavigationRootManager;
+			int _currentRootViewHeight = 0;
+			int _currentRootViewWidth = 0;
+			GenericGlobalLayoutListener? _rootViewLayoutListener;
+			AView? _rootView;
 
 			AView GetWindowRootView() =>
 				 _windowMauiContext
@@ -213,7 +226,6 @@ public ModalContainer(
 			{
 				_windowMauiContext = windowMauiContext;
 				Modal = modal;
-
 				_backgroundView = new AView(_windowMauiContext.Context);
 				UpdateBackgroundColor();
 				AddView(_backgroundView);
@@ -229,22 +241,110 @@ public ModalContainer(
 					.BeginTransaction()
 					.Add(this.Id, _modalFragment)
 					.Commit();
+			}
 
+			protected override void OnAttachedToWindow()
+			{
+				base.OnAttachedToWindow();
 				UpdateMargin();
+				UpdateRootView(GetWindowRootView());
+			}
+
+			protected override void OnDetachedFromWindow()
+			{
+				base.OnDetachedFromWindow();
+				UpdateRootView(null);
+			}
+
+			void UpdateRootView(AView? rootView)
+			{
+				if (_rootView.IsAlive() && _rootView != null)
+				{
+					_rootView.LayoutChange -= OnRootViewLayoutChanged;
+					_rootView = null;
+				}
+
+				if (rootView.IsAlive() && rootView != null)
+				{
+					rootView.LayoutChange += OnRootViewLayoutChanged;
+					_rootView = rootView;
+					_currentRootViewHeight = _rootView.MeasuredHeight;
+					_currentRootViewWidth = _rootView.MeasuredWidth;
+				}
+			}
+
+			// If the RootView changes sizes that means we also need to change sizes
+			// This will typically happen when the user is opening the soft keyboard 
+			// which sometimes causes the available window size to change
+			void OnRootViewLayoutChanged(object? sender, LayoutChangeEventArgs e)
+			{
+				if (Modal == null || sender is not AView view)
+					return;
+
+				var modalStack = Modal?.Navigation?.ModalStack;
+				if (modalStack == null ||
+					modalStack.Count == 0 ||
+					modalStack[modalStack.Count - 1] != Modal)
+				{
+					return;
+				}
+
+				if ((_currentRootViewHeight != view.MeasuredHeight || _currentRootViewWidth != view.MeasuredWidth)
+					&& this.ViewTreeObserver != null)
+				{
+					// When the keyboard closes Android calls layout but doesn't call remeasure.
+					// MY guess is that this is due to the modal not being part of the FitSystemWindowView
+					// The modal is added to the decor view so its dimensions don't get updated.
+					// So, here we are waiting for the layout pass to finish and then we remeasure the modal					
+					//
+					// For .NET 8 we'll convert this all over to using a DialogFragment
+					// which means we can delete most of the awkward code here
+					_currentRootViewHeight = view.MeasuredHeight;
+					_currentRootViewWidth = view.MeasuredWidth;
+					if (!this.IsInLayout)
+					{
+						this.InvalidateMeasure(Modal);
+						return;
+					}
+
+					_rootViewLayoutListener ??= new GenericGlobalLayoutListener((listener, view) =>
+					{
+						if (view != null && !this.IsInLayout)
+						{
+							listener.Invalidate();
+							_rootViewLayoutListener = null;
+							this.InvalidateMeasure(Modal);
+						}
+					}, this);
+				}
 			}
 
 			void UpdateMargin()
 			{
 				// This sets up the modal container to be offset from the top of window the same
 				// amount as the view it's covering. This will make it so the
-				// ModalContainer takes into account the statusbar or lack thereof
-				var rootView = GetWindowRootView();
-				int y = (int)rootView.GetLocationOnScreenPx().Y;
+				// ModalContainer takes into account the StatusBar or lack thereof
+				var decorView = Context?.GetActivity()?.Window?.DecorView;
 
-				if (this.LayoutParameters is ViewGroup.MarginLayoutParams mlp &&
-					mlp.TopMargin != y)
+				if (decorView != null && this.LayoutParameters is ViewGroup.MarginLayoutParams mlp)
 				{
-					mlp.TopMargin = y;
+					var windowInsets = ViewCompat.GetRootWindowInsets(decorView);
+					if (windowInsets != null)
+					{
+						var barInsets = windowInsets.GetInsetsIgnoringVisibility(WindowInsetsCompat.Type.SystemBars());
+
+						if (mlp.TopMargin != barInsets.Top)
+							mlp.TopMargin = barInsets.Top;
+
+						if (mlp.LeftMargin != barInsets.Left)
+							mlp.LeftMargin = barInsets.Left;
+
+						if (mlp.RightMargin != barInsets.Right)
+							mlp.RightMargin = barInsets.Right;
+
+						if (mlp.BottomMargin != barInsets.Bottom)
+							mlp.BottomMargin = barInsets.Bottom;
+					}
 				}
 			}
 
@@ -262,8 +362,8 @@ protected override void OnMeasure(int widthMeasureSpec, int heightMeasureSpec)
 					return;
 				}
 
-				var rootView = GetWindowRootView();
 				UpdateMargin();
+				var rootView = GetWindowRootView();
 
 				widthMeasureSpec = MeasureSpecMode.Exactly.MakeMeasureSpec(rootView.MeasuredWidth);
 				heightMeasureSpec = MeasureSpecMode.Exactly.MakeMeasureSpec(rootView.MeasuredHeight);
@@ -314,6 +414,10 @@ public void Destroy()
 
 				Modal.Handler = null;
 
+				UpdateRootView(null);
+				_rootViewLayoutListener?.Invalidate();
+				_rootViewLayoutListener = null;
+
 				_fragmentManager
 					.BeginTransaction()
 					.Remove(_modalFragment)

src/Controls/tests/DeviceTests/ControlsHandlerTestBase.Android.cs

@@ -198,6 +198,11 @@ public override AView OnCreateView(ALayoutInflater inflater, AViewGroup containe
 				FakeActivityRootView.AddView(handler.PlatformViewUnderTest);
 				handler.PlatformViewUnderTest.LayoutParameters = new FitWindowsFrameLayout.LayoutParams(AViewGroup.LayoutParams.MatchParent, AViewGroup.LayoutParams.MatchParent);
 
+				if (_window is Window window)
+				{
+					window.ModalNavigationManager.SetModalParentView(FakeActivityRootView);
+				}
+
 				return FakeActivityRootView;
 			}