Drag and Drop (#62)

* Flutter 3.0.3

* Container click without ink passes coordinates in event

* Drag and Drop implementation

.appveyor.yml

@@ -135,7 +135,7 @@ for:
 
     install:
       - brew install cocoapods
-      - curl https://storage.googleapis.com/flutter_infra_release/releases/stable/macos/flutter_macos_3.0.2-stable.zip -o flutter_macos_stable.zip
+      - curl https://storage.googleapis.com/flutter_infra_release/releases/stable/macos/flutter_macos_3.0.3-stable.zip -o flutter_macos_stable.zip
       - unzip -qq flutter_macos_stable.zip
       - export PATH="$PATH:`pwd`/flutter/bin"
       - flutter --version
@@ -204,7 +204,7 @@ for:
 
     install:
       - export LANG=en_US.UTF-8
-      - curl https://storage.googleapis.com/flutter_infra_release/releases/stable/macos/flutter_macos_3.0.2-stable.zip -o flutter_macos_stable.zip
+      - curl https://storage.googleapis.com/flutter_infra_release/releases/stable/macos/flutter_macos_3.0.3-stable.zip -o flutter_macos_stable.zip
       - unzip -qq flutter_macos_stable.zip
       - export PATH="$PATH:`pwd`/flutter/bin"
       - flutter --version

ci/install_flutter.ps1

@@ -1,7 +1,7 @@
 $distPath = "$env:TEMP\flutter_windows_stable.zip"
 
 Write-Host "Downloading Flutter SDK..."
-(New-Object Net.WebClient).DownloadFile("https://storage.googleapis.com/flutter_infra_release/releases/stable/windows/flutter_windows_3.0.2-stable.zip", $distPath)
+(New-Object Net.WebClient).DownloadFile("https://storage.googleapis.com/flutter_infra_release/releases/stable/windows/flutter_windows_3.0.3-stable.zip", $distPath)
 
 Write-Host "Unpacking Flutter SDK..."
 7z x $distPath -o"$env:SystemDrive\" | Out-Null

client/lib/controls/container.dart

@@ -81,12 +81,13 @@ class ContainerControl extends StatelessWidget {
           cursor: SystemMouseCursors.click,
           child: GestureDetector(
             child: container,
-            onTap: () {
+            onTapDown: (details) {
               debugPrint("Container ${control.id} clicked!");
               ws.pageEventFromWeb(
                   eventTarget: control.id,
                   eventName: "click",
-                  eventData: control.attrs["data"] ?? "");
+                  eventData: control.attrString("data", "")! +
+                      "${details.localPosition.dx}:${details.localPosition.dy} ${details.globalPosition.dx}:${details.globalPosition.dy}");
             },
           ),
         );

client/lib/controls/create_control.dart

@@ -14,6 +14,8 @@ import 'clipboard.dart';
 import 'column.dart';
 import 'container.dart';
 import 'divider.dart';
+import 'drag_target.dart';
+import 'draggable.dart';
 import 'dropdown.dart';
 import 'elevated_button.dart';
 import 'floating_action_button.dart';
@@ -145,6 +147,18 @@ Widget createControl(Control? parent, String id, bool parentDisabled) {
               control: controlView.control,
               children: controlView.children,
               parentDisabled: parentDisabled);
+        case ControlType.draggable:
+          return DraggableControl(
+              parent: parent,
+              control: controlView.control,
+              children: controlView.children,
+              parentDisabled: parentDisabled);
+        case ControlType.dragTarget:
+          return DragTargetControl(
+              parent: parent,
+              control: controlView.control,
+              children: controlView.children,
+              parentDisabled: parentDisabled);
         case ControlType.card:
           return CardControl(
               parent: parent,

client/lib/controls/drag_target.dart

@@ -0,0 +1,93 @@
+import 'dart:convert';
+
+import 'package:flet_view/controls/error.dart';
+import 'package:flutter/material.dart';
+
+import '../models/control.dart';
+import '../web_socket_client.dart';
+import 'create_control.dart';
+
+class DragTargetControl extends StatelessWidget {
+  final Control? parent;
+  final Control control;
+  final List<Control> children;
+  final bool parentDisabled;
+
+  const DragTargetControl(
+      {Key? key,
+      this.parent,
+      required this.control,
+      required this.children,
+      required this.parentDisabled})
+      : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    debugPrint("DragTarget build: ${control.id}");
+
+    var group = control.attrString("group", "");
+    var contentCtrls =
+        children.where((c) => c.name == "content" && c.isVisible);
+    bool disabled = control.isDisabled || parentDisabled;
+
+    Widget? child = contentCtrls.isNotEmpty
+        ? createControl(control, contentCtrls.first.id, disabled)
+        : null;
+
+    if (child == null) {
+      return const ErrorControl("DragTarget should have content.");
+    }
+
+    return DragTarget<String>(
+      builder: (
+        BuildContext context,
+        List<dynamic> accepted,
+        List<dynamic> rejected,
+      ) {
+        debugPrint(
+            "DragTarget.builder ${control.id}: accepted=${accepted.length}, rejected=${rejected.length}");
+        return child;
+      },
+      onWillAccept: (data) {
+        debugPrint("DragTarget.onAccept ${control.id}: $data");
+        String srcGroup = "";
+        if (data != null) {
+          var jd = json.decode(data);
+          srcGroup = jd["group"] as String;
+        }
+        var groupsEqual = srcGroup == group;
+        ws.pageEventFromWeb(
+            eventTarget: control.id,
+            eventName: "will_accept",
+            eventData:
+                control.attrString("data", "")! + groupsEqual.toString());
+        return groupsEqual;
+      },
+      onAccept: (data) {
+        debugPrint("DragTarget.onAccept ${control.id}: $data");
+        var jd = json.decode(data);
+        var srcId = jd["id"] as String;
+        ws.pageEventFromWeb(
+            eventTarget: control.id,
+            eventName: "accept",
+            eventData: control.attrString("data", "")! + srcId);
+      },
+      // onAcceptWithDetails: (details) {
+      //   debugPrint(
+      //       "onAcceptWithDetails: ${details.data} ${details.offset}");
+      // },
+      onLeave: (data) {
+        debugPrint("DragTarget.onLeave ${control.id}: $data");
+        String srcId = "";
+        if (data != null) {
+          var jd = json.decode(data);
+          srcId = jd["id"] as String;
+        }
+        ws.pageEventFromWeb(
+            eventTarget: control.id,
+            eventName: "leave",
+            eventData: control.attrString("data", "")! + srcId);
+      },
+    );
+  }
+}

client/lib/controls/draggable.dart

@@ -0,0 +1,72 @@
+import 'dart:convert';
+
+import 'package:flet_view/controls/error.dart';
+import 'package:flutter/material.dart';
+
+import '../models/control.dart';
+import 'create_control.dart';
+
+class DraggableControl extends StatelessWidget {
+  final Control? parent;
+  final Control control;
+  final List<Control> children;
+  final bool parentDisabled;
+
+  const DraggableControl(
+      {Key? key,
+      this.parent,
+      required this.control,
+      required this.children,
+      required this.parentDisabled})
+      : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    debugPrint("DragTarget build: ${control.id}");
+
+    var group = control.attrString("group", "");
+    var contentCtrls =
+        children.where((c) => c.name == "content" && c.isVisible);
+    var contentWhenDraggingCtrls =
+        children.where((c) => c.name == "content_when_dragging" && c.isVisible);
+    var contentFeedbackCtrls =
+        children.where((c) => c.name == "content_feedback" && c.isVisible);
+    bool disabled = control.isDisabled || parentDisabled;
+
+    Widget? child = contentCtrls.isNotEmpty
+        ? createControl(control, contentCtrls.first.id, disabled)
+        : null;
+
+    Widget? childWhenDragging = contentWhenDraggingCtrls.isNotEmpty
+        ? createControl(control, contentWhenDraggingCtrls.first.id, disabled)
+        : null;
+
+    Widget? childFeedback = contentFeedbackCtrls.isNotEmpty
+        ? createControl(control, contentFeedbackCtrls.first.id, disabled)
+        : null;
+
+    if (child == null) {
+      return const ErrorControl("Draggable should have content.");
+    }
+
+    var data = json.encode({"id": control.id, "group": group});
+
+    return Draggable<String>(
+      data: data,
+      child: MouseRegion(
+        cursor: SystemMouseCursors.grab,
+        child: child,
+      ),
+      childWhenDragging: childWhenDragging,
+      feedback: MouseRegion(
+        cursor: SystemMouseCursors.grabbing,
+        child: childFeedback ?? Opacity(opacity: 0.5, child: child),
+      ),
+      // dragAnchorStrategy: (d, context, offset) {
+      //   debugPrint("dragAnchorStrategy: ${offset.dx}, ${offset.dy}");
+      //   return offset;
+      // }
+      //feedbackOffset: const Offset(-30, -30),
+    );
+  }
+}

client/lib/models/control_type.dart

@@ -9,6 +9,8 @@ enum ControlType {
   column,
   container,
   divider,
+  draggable,
+  dragTarget,
   dropdown,
   dropdownOption,
   elevatedButton,

sdk/python/flet/__init__.py

@@ -8,6 +8,8 @@
 from flet.container import Container
 from flet.control import Control
 from flet.divider import Divider
+from flet.drag_target import DragTarget
+from flet.draggable import Draggable
 from flet.dropdown import Dropdown
 from flet.elevated_button import ElevatedButton
 from flet.filled_button import FilledButton

sdk/python/flet/drag_target.py

@@ -0,0 +1,94 @@
+from beartype import beartype
+
+from flet.control import Control
+from flet.ref import Ref
+
+
+class DragTarget(Control):
+    def __init__(
+        self,
+        ref: Ref = None,
+        disabled: bool = None,
+        visible: bool = None,
+        data: any = None,
+        #
+        # Specific
+        #
+        group: str = None,
+        content: Control = None,
+        on_will_accept=None,
+        on_accept=None,
+        on_leave=None,
+    ):
+
+        Control.__init__(
+            self,
+            ref=ref,
+            disabled=disabled,
+            visible=visible,
+            data=data,
+        )
+
+        self.__content: Control = None
+
+        self.group = group
+        self.content = content
+        self.on_will_accept = on_will_accept
+        self.on_accept = on_accept
+        self.on_leave = on_leave
+
+    def _get_control_name(self):
+        return "dragtarget"
+
+    def _get_children(self):
+        children = []
+        if self.__content:
+            self.__content._set_attr_internal("n", "content")
+            children.append(self.__content)
+        return children
+
+    # group
+    @property
+    def group(self):
+        return self._get_attr("group")
+
+    @group.setter
+    @beartype
+    def group(self, value):
+        self._set_attr("group", value)
+
+    # content
+    @property
+    def content(self):
+        return self.__content
+
+    @content.setter
+    def content(self, value):
+        self.__content = value
+
+    # on_will_accept
+    @property
+    def on_will_accept(self):
+        return self._get_event_handler("will_accept")
+
+    @on_will_accept.setter
+    def on_will_accept(self, handler):
+        self._add_event_handler("will_accept", handler)
+
+    # on_accept
+    @property
+    def on_accept(self):
+        return self._get_event_handler("accept")
+
+    @on_accept.setter
+    def on_accept(self, handler):
+        self._add_event_handler("accept", handler)
+
+    # on_leave
+    @property
+    def on_leave(self):
+        return self._get_event_handler("leave")
+
+    @on_leave.setter
+    def on_leave(self, handler):
+        self._add_event_handler("leave", handler)