Added onSelectionChange callback to SelectionRegion and SelectionArea (#108985)

packages/flutter/lib/src/material/selection_area.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'package:flutter/cupertino.dart';
+import 'package:flutter/rendering.dart';
 
 import 'debug.dart';
 import 'desktop_text_selection.dart';
@@ -41,6 +42,7 @@ class SelectionArea extends StatefulWidget {
     this.focusNode,
     this.selectionControls,
     this.magnifierConfiguration,
+    this.onSelectionChanged,
     required this.child,
   });
 
@@ -63,6 +65,9 @@ class SelectionArea extends StatefulWidget {
   /// If it is null, the platform specific selection control is used.
   final TextSelectionControls? selectionControls;
 
+  /// Called when the selected content changes.
+  final ValueChanged<SelectedContent?>? onSelectionChanged;
+
   /// The child widget this selection area applies to.
   ///
   /// {@macro flutter.widgets.ProxyWidget.child}
@@ -112,6 +117,7 @@ class _SelectionAreaState extends State<SelectionArea> {
       focusNode: _effectiveFocusNode,
       selectionControls: controls,
       magnifierConfiguration: widget.magnifierConfiguration ?? TextMagnifier.adaptiveMagnifierConfiguration,
+      onSelectionChanged: widget.onSelectionChanged,
       child: widget.child,
     );
   }

packages/flutter/lib/src/widgets/selectable_region.dart

@@ -204,6 +204,7 @@ class SelectableRegion extends StatefulWidget {
     required this.selectionControls,
     required this.child,
     this.magnifierConfiguration = TextMagnifierConfiguration.disabled,
+    this.onSelectionChanged,
   });
 
   /// {@macro flutter.widgets.magnifier.TextMagnifierConfiguration.intro}
@@ -230,6 +231,9 @@ class SelectableRegion extends StatefulWidget {
   /// [TextSelectionControls] implementation with no controls.
   final TextSelectionControls selectionControls;
 
+  /// Called when the selected content changes.
+  final ValueChanged<SelectedContent?>? onSelectionChanged;
+
   @override
   State<StatefulWidget> createState() => _SelectableRegionState();
 }
@@ -252,6 +256,7 @@ class _SelectableRegionState extends State<SelectableRegion> with TextSelectionD
                                         || _selectionDelegate.value.endSelectionPoint != null;
 
   Orientation? _lastOrientation;
+  SelectedContent? _lastSelectedContent;
 
   @override
   void initState() {
@@ -389,8 +394,16 @@ class _SelectableRegionState extends State<SelectableRegion> with TextSelectionD
     _selectEndTo(offset: details.globalPosition, continuous: true);
   }
 
+  void _updateSelectedContentIfNeeded() {
+    if (_lastSelectedContent?.plainText != _selectable?.getSelectedContent()?.plainText) {
+      _lastSelectedContent = _selectable?.getSelectedContent();
+      widget.onSelectionChanged?.call(_lastSelectedContent);
+    }
+  }
+
   void _handleMouseDragEnd(DragEndDetails details) {
     _finalizeSelection();
+    _updateSelectedContentIfNeeded();
   }
 
   void _handleTouchLongPressStart(LongPressStartDetails details) {
@@ -398,6 +411,7 @@ class _SelectableRegionState extends State<SelectableRegion> with TextSelectionD
     _selectWordAt(offset: details.globalPosition);
     _showToolbar();
     _showHandles();
+    _updateSelectedContentIfNeeded();
   }
 
   void _handleTouchLongPressMoveUpdate(LongPressMoveUpdateDetails details) {
@@ -406,6 +420,7 @@ class _SelectableRegionState extends State<SelectableRegion> with TextSelectionD
 
   void _handleTouchLongPressEnd(LongPressEndDetails details) {
     _finalizeSelection();
+    _updateSelectedContentIfNeeded();
   }
 
   void _handleRightClickDown(TapDownDetails details) {
@@ -413,6 +428,7 @@ class _SelectableRegionState extends State<SelectableRegion> with TextSelectionD
     _selectWordAt(offset: details.globalPosition);
     _showHandles();
     _showToolbar(location: details.globalPosition);
+    _updateSelectedContentIfNeeded();
   }
 
   // Selection update helper methods.
@@ -451,6 +467,7 @@ class _SelectableRegionState extends State<SelectableRegion> with TextSelectionD
  void _onAnyDragEnd(DragEndDetails details) {
   _selectionOverlay!.hideMagnifier(shouldShowToolbar: true);
   _stopSelectionEndEdgeUpdate();
+  _updateSelectedContentIfNeeded();
  }
 
   void _stopSelectionEndEdgeUpdate() {
@@ -802,6 +819,7 @@ class _SelectableRegionState extends State<SelectableRegion> with TextSelectionD
   void _clearSelection() {
     _finalizeSelection();
     _selectable?.dispatchSelectionEvent(const ClearSelectionEvent());
+    _updateSelectedContentIfNeeded();
   }
 
   Future<void> _copy() async {
@@ -836,6 +854,7 @@ class _SelectableRegionState extends State<SelectableRegion> with TextSelectionD
       _showToolbar();
       _showHandles();
     }
+    _updateSelectedContentIfNeeded();
   }
 
   @override

packages/flutter/test/material/selection_area_test.dart

@@ -4,9 +4,17 @@
 
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
+import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 
+Offset textOffsetToPosition(RenderParagraph paragraph, int offset) {
+  const Rect caret = Rect.fromLTWH(0.0, 0.0, 2.0, 20.0);
+  final Offset localOffset = paragraph.getOffsetForCaret(TextPosition(offset: offset), caret);
+  return paragraph.localToGlobal(localOffset);
+}
+
 void main() {
   testWidgets('SelectionArea uses correct selection controls', (WidgetTester tester) async {
     await tester.pumpWidget(const MaterialApp(
@@ -33,4 +41,35 @@ void main() {
         break;
     }
   }, variant: TargetPlatformVariant.all());
+
+  testWidgets('onSelectionChange is called when the selection changes', (WidgetTester tester) async {
+    SelectedContent? content;
+
+    await tester.pumpWidget(MaterialApp(
+      home: SelectionArea(
+        child: const Text('How are you'),
+        onSelectionChanged: (SelectedContent? selectedContent) => content = selectedContent,
+      ),
+    ));
+    final RenderParagraph paragraph = tester.renderObject<RenderParagraph>(find.descendant(of: find.text('How are you'), matching: find.byType(RichText)));
+    final TestGesture gesture = await tester.startGesture(textOffsetToPosition(paragraph, 4), kind: PointerDeviceKind.mouse);
+    expect(content, isNull);
+    addTearDown(gesture.removePointer);
+    await tester.pump();
+
+    await gesture.moveTo(textOffsetToPosition(paragraph, 7));
+    await gesture.up();
+    await tester.pump();
+    expect(content, isNotNull);
+    expect(content!.plainText, 'are');
+
+    // Backwards selection.
+    await gesture.down(textOffsetToPosition(paragraph, 3));
+    expect(content, isNull);
+    await gesture.moveTo(textOffsetToPosition(paragraph, 0));
+    await gesture.up();
+    await tester.pump();
+    expect(content, isNotNull);
+    expect(content!.plainText, 'How');
+  });
 }

packages/flutter/test/widgets/selectable_region_test.dart

@@ -1208,6 +1208,43 @@ void main() {
     skip: kIsWeb, // [intended] Web uses its native context menu.
     variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS, TargetPlatform.android }),
   );
+
+  testWidgets('onSelectionChange is called when the selection changes', (WidgetTester tester) async {
+    SelectedContent? content;
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: SelectableRegion(
+          onSelectionChanged: (SelectedContent? selectedContent) => content = selectedContent,
+          focusNode: FocusNode(),
+          selectionControls: materialTextSelectionControls,
+          child: const Center(
+            child: Text('How are you'),
+          ),
+        ),
+      ),
+    );
+    final RenderParagraph paragraph = tester.renderObject<RenderParagraph>(find.descendant(of: find.text('How are you'), matching: find.byType(RichText)));
+    final TestGesture gesture = await tester.startGesture(textOffsetToPosition(paragraph, 4), kind: PointerDeviceKind.mouse);
+    expect(content, isNull);
+    addTearDown(gesture.removePointer);
+    await tester.pump();
+
+    await gesture.moveTo(textOffsetToPosition(paragraph, 7));
+    await gesture.up();
+    await tester.pump();
+    expect(content, isNotNull);
+    expect(content!.plainText, 'are');
+
+    // Backwards selection.
+    await gesture.down(textOffsetToPosition(paragraph, 3));
+    expect(content, isNull);
+    await gesture.moveTo(textOffsetToPosition(paragraph, 0));
+    await gesture.up();
+    await tester.pump();
+    expect(content, isNotNull);
+    expect(content!.plainText, 'How');
+  });
 }
 
 class SelectionSpy extends LeafRenderObjectWidget {