Add double click and double click + drag gestures to SelectionArea (#124817)

Adds double click to select a word.
Adds double click + drag to select word by word.

https://user-images.githubusercontent.com/948037/234363577-941c36bc-ac42-4b7f-84aa-26b106c9ff05.mov

Partially fixes #104552

packages/flutter/lib/src/rendering/selection.dart

@@ -375,26 +375,44 @@ class SelectWordSelectionEvent extends SelectionEvent {
 ///
 /// The [globalPosition] contains the new offset of the edge.
 ///
-/// This event is dispatched when the framework detects [DragStartDetails] in
+/// The [granularity] contains the granularity that the selection edge should move by.
+/// Only [TextGranularity.character] and [TextGranularity.word] are currently supported.
+///
+/// This event is dispatched when the framework detects [TapDragStartDetails] in
 /// [SelectionArea]'s gesture recognizers for mouse devices, or the selection
 /// handles have been dragged to new locations.
 class SelectionEdgeUpdateEvent extends SelectionEvent {
   /// Creates a selection start edge update event.
   ///
   /// The [globalPosition] contains the location of the selection start edge.
+  ///
+  /// The [granularity] contains the granularity which the selection edge should move by.
+  /// This value defaults to [TextGranularity.character].
   const SelectionEdgeUpdateEvent.forStart({
-    required this.globalPosition
-  }) : super._(SelectionEventType.startEdgeUpdate);
+    required this.globalPosition,
+    TextGranularity? granularity
+  }) : granularity = granularity ?? TextGranularity.character, super._(SelectionEventType.startEdgeUpdate);
 
   /// Creates a selection end edge update event.
   ///
   /// The [globalPosition] contains the new location of the selection end edge.
+  ///
+  /// The [granularity] contains the granularity which the selection edge should move by.
+  /// This value defaults to [TextGranularity.character].
   const SelectionEdgeUpdateEvent.forEnd({
-    required this.globalPosition
-  }) : super._(SelectionEventType.endEdgeUpdate);
+    required this.globalPosition,
+    TextGranularity? granularity
+  }) : granularity = granularity ?? TextGranularity.character, super._(SelectionEventType.endEdgeUpdate);
 
   /// The new location of the selection edge.
   final Offset globalPosition;
+
+  /// The granularity for which the selection moves.
+  ///
+  /// Only [TextGranularity.character] and [TextGranularity.word] are currently supported.
+  ///
+  /// Defaults to [TextGranularity.character].
+  final TextGranularity granularity;
 }
 
 /// Extends the start or end of the selection by a given [TextGranularity].
@@ -686,7 +704,7 @@ class SelectionGeometry {
 
 /// The geometry information of a selection point.
 @immutable
-class SelectionPoint {
+class SelectionPoint with Diagnosticable {
   /// Creates a selection point object.
   ///
   /// All properties must not be null.
@@ -730,6 +748,14 @@ class SelectionPoint {
       handleType,
     );
   }
+
+  @override
+  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+    super.debugFillProperties(properties);
+    properties.add(DiagnosticsProperty<Offset>('localPosition', localPosition));
+    properties.add(DoubleProperty('lineHeight', lineHeight));
+    properties.add(EnumProperty<TextSelectionHandleType>('handleType', handleType));
+  }
 }
 
 /// The type of selection handle to be displayed.

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

@@ -1177,11 +1177,11 @@ class _ScrollableSelectionContainerDelegate extends MultiSelectableSelectionCont
     if (event.type == SelectionEventType.endEdgeUpdate) {
       _currentDragEndRelatedToOrigin = _inferPositionRelatedToOrigin(event.globalPosition);
       final Offset endOffset = _currentDragEndRelatedToOrigin!.translate(-deltaToOrigin.dx, -deltaToOrigin.dy);
-      event = SelectionEdgeUpdateEvent.forEnd(globalPosition: endOffset);
+      event = SelectionEdgeUpdateEvent.forEnd(globalPosition: endOffset, granularity: event.granularity);
     } else {
       _currentDragStartRelatedToOrigin = _inferPositionRelatedToOrigin(event.globalPosition);
       final Offset startOffset = _currentDragStartRelatedToOrigin!.translate(-deltaToOrigin.dx, -deltaToOrigin.dy);
-      event = SelectionEdgeUpdateEvent.forStart(globalPosition: startOffset);
+      event = SelectionEdgeUpdateEvent.forStart(globalPosition: startOffset, granularity: event.granularity);
     }
     final SelectionResult result = super.handleSelectionEdgeUpdate(event);
 
@@ -1430,6 +1430,9 @@ class _ScrollableSelectionContainerDelegate extends MultiSelectableSelectionCont
       final Offset deltaToOrigin = _getDeltaToScrollOrigin(state);
       final Offset startOffset = _currentDragStartRelatedToOrigin!.translate(-deltaToOrigin.dx, -deltaToOrigin.dy);
       selectable.dispatchSelectionEvent(SelectionEdgeUpdateEvent.forStart(globalPosition: startOffset));
+      // Make sure we track that we have synthesized a start event for this selectable,
+      // so we don't synthesize events unnecessarily.
+      _selectableStartEdgeUpdateRecords[selectable] = state.position.pixels;
     }
     final double? previousEndRecord = _selectableEndEdgeUpdateRecords[selectable];
     if (_currentDragEndRelatedToOrigin != null &&
@@ -1438,6 +1441,9 @@ class _ScrollableSelectionContainerDelegate extends MultiSelectableSelectionCont
       final Offset deltaToOrigin = _getDeltaToScrollOrigin(state);
       final Offset endOffset = _currentDragEndRelatedToOrigin!.translate(-deltaToOrigin.dx, -deltaToOrigin.dy);
       selectable.dispatchSelectionEvent(SelectionEdgeUpdateEvent.forEnd(globalPosition: endOffset));
+      // Make sure we track that we have synthesized an end event for this selectable,
+      // so we don't synthesize events unnecessarily.
+      _selectableEndEdgeUpdateRecords[selectable] = state.position.pixels;
     }
   }
 

packages/flutter/test/material/selection_area_test.dart

@@ -157,6 +157,7 @@ void main() {
 
     // Backwards selection.
     await gesture.down(textOffsetToPosition(paragraph, 3));
+    await tester.pumpAndSettle();
     expect(content, isNull);
     await gesture.moveTo(textOffsetToPosition(paragraph, 0));
     await gesture.up();

packages/flutter/test/widgets/scrollable_selection_test.dart

@@ -4,6 +4,7 @@
 
 import 'dart:ui' as ui;
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
@@ -106,6 +107,89 @@ void main() {
     await gesture.up();
   });
 
+  testWidgets('mouse can select multiple widgets on double-click drag', (WidgetTester tester) async {
+    await tester.pumpWidget(MaterialApp(
+      home: SelectionArea(
+        selectionControls: materialTextSelectionControls,
+        child: ListView.builder(
+          itemCount: 100,
+          itemBuilder: (BuildContext context, int index) {
+            return Text('Item $index');
+          },
+        ),
+      ),
+    ));
+    await tester.pumpAndSettle();
+
+    final RenderParagraph paragraph1 = tester.renderObject<RenderParagraph>(find.descendant(of: find.text('Item 0'), matching: find.byType(RichText)));
+    final TestGesture gesture = await tester.startGesture(textOffsetToPosition(paragraph1, 2), kind: ui.PointerDeviceKind.mouse);
+    addTearDown(gesture.removePointer);
+    await tester.pump();
+
+    await gesture.up();
+    await tester.pump();
+    await gesture.down(textOffsetToPosition(paragraph1, 2));
+    await tester.pumpAndSettle();
+    expect(paragraph1.selections[0], const TextSelection(baseOffset: 0, extentOffset: 4));
+
+    await gesture.moveTo(textOffsetToPosition(paragraph1, 4));
+    await tester.pump();
+    expect(paragraph1.selections[0], const TextSelection(baseOffset: 0, extentOffset: 5));
+
+    final RenderParagraph paragraph2 = tester.renderObject<RenderParagraph>(find.descendant(of: find.text('Item 1'), matching: find.byType(RichText)));
+    await gesture.moveTo(textOffsetToPosition(paragraph2, 4));
+    // Should select the rest of paragraph 1.
+    expect(paragraph1.selections[0], const TextSelection(baseOffset: 0, extentOffset: 6));
+    expect(paragraph2.selections[0], const TextSelection(baseOffset: 0, extentOffset: 5));
+
+    final RenderParagraph paragraph3 = tester.renderObject<RenderParagraph>(find.descendant(of: find.text('Item 3'), matching: find.byType(RichText)));
+    await gesture.moveTo(textOffsetToPosition(paragraph3, 3));
+    expect(paragraph1.selections[0], const TextSelection(baseOffset: 0, extentOffset: 6));
+    expect(paragraph2.selections[0], const TextSelection(baseOffset: 0, extentOffset: 6));
+    expect(paragraph3.selections[0], const TextSelection(baseOffset: 0, extentOffset: 4));
+
+    await gesture.up();
+  }, skip: kIsWeb); // https://github.com/flutter/flutter/issues/125582.
+
+  testWidgets('mouse can select multiple widgets on double-click drag - horizontal', (WidgetTester tester) async {
+    await tester.pumpWidget(MaterialApp(
+      home: SelectionArea(
+        selectionControls: materialTextSelectionControls,
+        child: ListView.builder(
+          scrollDirection: Axis.horizontal,
+          itemCount: 100,
+          itemBuilder: (BuildContext context, int index) {
+            return Text('Item $index');
+          },
+        ),
+      ),
+    ));
+    await tester.pumpAndSettle();
+
+    final RenderParagraph paragraph1 = tester.renderObject<RenderParagraph>(find.descendant(of: find.text('Item 0'), matching: find.byType(RichText)));
+    final TestGesture gesture = await tester.startGesture(textOffsetToPosition(paragraph1, 2), kind: ui.PointerDeviceKind.mouse);
+    addTearDown(gesture.removePointer);
+    await tester.pump();
+    await gesture.up();
+    await tester.pump();
+
+    await gesture.down(textOffsetToPosition(paragraph1, 2));
+    await tester.pumpAndSettle();
+    expect(paragraph1.selections[0], const TextSelection(baseOffset: 0, extentOffset: 4));
+
+    await gesture.moveTo(textOffsetToPosition(paragraph1, 4));
+    await tester.pump();
+    expect(paragraph1.selections[0], const TextSelection(baseOffset: 0, extentOffset: 5));
+
+    final RenderParagraph paragraph2 = tester.renderObject<RenderParagraph>(find.descendant(of: find.text('Item 1'), matching: find.byType(RichText)));
+    await gesture.moveTo(textOffsetToPosition(paragraph2, 5) + const Offset(0, 5));
+    // Should select the rest of paragraph 1.
+    expect(paragraph1.selections[0], const TextSelection(baseOffset: 0, extentOffset: 6));
+    expect(paragraph2.selections[0], const TextSelection(baseOffset: 0, extentOffset: 6));
+
+    await gesture.up();
+  }, skip: kIsWeb); // https://github.com/flutter/flutter/issues/125582.
+
   testWidgets('select to scroll forward', (WidgetTester tester) async {
     final ScrollController controller = ScrollController();
     await tester.pumpWidget(MaterialApp(