Add support for text selection via mouse to Cupertino text fields (#29769)

packages/flutter/lib/src/cupertino/text_field.dart

@@ -533,6 +533,28 @@ class _CupertinoTextFieldState extends State<CupertinoTextField> with AutomaticK
     _editableTextKey.currentState.showToolbar();
   }
 
+  void _handleMouseDragSelectionStart(DragStartDetails details) {
+    _renderEditable.selectPositionAt(
+      from: details.globalPosition,
+      cause: SelectionChangedCause.drag,
+    );
+  }
+
+  void _handleMouseDragSelectionUpdate(
+      DragStartDetails startDetails,
+      DragUpdateDetails updateDetails,
+  ) {
+    _renderEditable.selectPositionAt(
+      from: startDetails.globalPosition,
+      to: updateDetails.globalPosition,
+      cause: SelectionChangedCause.drag,
+    );
+  }
+
+  void _handleMouseDragSelectionEnd(DragEndDetails details) {
+    _requestKeyboard();
+  }
+
   void _handleSelectionChanged(TextSelection selection, SelectionChangedCause cause) {
     if (cause == SelectionChangedCause.longPress) {
       _editableTextKey.currentState?.bringIntoView(selection.base);
@@ -742,6 +764,9 @@ class _CupertinoTextFieldState extends State<CupertinoTextField> with AutomaticK
               onSingleLongTapMoveUpdate: _handleSingleLongTapMoveUpdate,
               onSingleLongTapEnd: _handleSingleLongTapEnd,
               onDoubleTapDown: _handleDoubleTapDown,
+              onDragSelectionStart: _handleMouseDragSelectionStart,
+              onDragSelectionUpdate: _handleMouseDragSelectionUpdate,
+              onDragSelectionEnd: _handleMouseDragSelectionEnd,
               behavior: HitTestBehavior.translucent,
               child: _addTextDependentAttachments(paddedEditable, textStyle),
             ),

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

@@ -743,7 +743,7 @@ class _TextFieldState extends State<TextField> with AutomaticKeepAliveClientMixi
     }
   }
 
-  void _handleDragSelectionStart(DragStartDetails details) {
+  void _handleMouseDragSelectionStart(DragStartDetails details) {
     _renderEditable.selectPositionAt(
       from: details.globalPosition,
       cause: SelectionChangedCause.drag,
@@ -751,7 +751,7 @@ class _TextFieldState extends State<TextField> with AutomaticKeepAliveClientMixi
     _startSplash(details.globalPosition);
   }
 
-  void _handleDragSelectionUpdate(
+  void _handleMouseDragSelectionUpdate(
       DragStartDetails startDetails,
       DragUpdateDetails updateDetails,
   ) {
@@ -930,8 +930,8 @@ class _TextFieldState extends State<TextField> with AutomaticKeepAliveClientMixi
           onSingleLongTapMoveUpdate: _handleSingleLongTapMoveUpdate,
           onSingleLongTapEnd: _handleSingleLongTapEnd,
           onDoubleTapDown: _handleDoubleTapDown,
-          onDragSelectionStart: _handleDragSelectionStart,
-          onDragSelectionUpdate: _handleDragSelectionUpdate,
+          onDragSelectionStart: _handleMouseDragSelectionStart,
+          onDragSelectionUpdate: _handleMouseDragSelectionUpdate,
           behavior: HitTestBehavior.translucent,
           child: child,
         ),

packages/flutter/test/cupertino/text_field_test.dart

@@ -8,7 +8,7 @@ import 'package:flutter/cupertino.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter/foundation.dart';
-import 'package:flutter/gestures.dart' show DragStartBehavior;
+import 'package:flutter/gestures.dart' show DragStartBehavior, PointerDeviceKind;
 import 'package:flutter_test/flutter_test.dart';
 
 class MockClipboard {
@@ -1791,6 +1791,99 @@ void main() {
     expect(controller.selection.extentOffset, 5);
   });
 
+  testWidgets('Can select text by dragging with a mouse', (WidgetTester tester) async {
+    final TextEditingController controller = TextEditingController();
+
+    await tester.pumpWidget(
+      CupertinoApp(
+        home: Center(
+          child: CupertinoTextField(
+            dragStartBehavior: DragStartBehavior.down,
+            controller: controller,
+            style: const TextStyle(
+              fontFamily: 'Ahem',
+              fontSize: 10.0,
+            ),
+          ),
+        ),
+      ),
+    );
+
+    const String testValue = 'abc def ghi';
+    await tester.enterText(find.byType(CupertinoTextField), testValue);
+    // Skip past scrolling animation.
+    await tester.pump();
+    await tester.pump(const Duration(milliseconds: 200));
+
+    final Offset ePos = textOffsetToPosition(tester, testValue.indexOf('e'));
+    final Offset gPos = textOffsetToPosition(tester, testValue.indexOf('g'));
+
+    final TestGesture gesture = await tester.startGesture(ePos, kind: PointerDeviceKind.mouse);
+    await tester.pump();
+    await gesture.moveTo(gPos);
+    await tester.pump();
+    await gesture.up();
+    await tester.pumpAndSettle();
+
+    expect(controller.selection.baseOffset, testValue.indexOf('e'));
+    expect(controller.selection.extentOffset, testValue.indexOf('g'));
+  });
+
+  testWidgets('Continuous dragging does not cause flickering', (WidgetTester tester) async {
+    int selectionChangedCount = 0;
+    const String testValue = 'abc def ghi';
+    final TextEditingController controller = TextEditingController(text: testValue);
+
+    controller.addListener(() {
+      selectionChangedCount++;
+    });
+
+    await tester.pumpWidget(
+      CupertinoApp(
+        home: Center(
+          child: CupertinoTextField(
+            dragStartBehavior: DragStartBehavior.down,
+            controller: controller,
+            style: const TextStyle(
+              fontFamily: 'Ahem',
+              fontSize: 10.0,
+            ),
+          ),
+        ),
+      ),
+    );
+
+    final Offset cPos = textOffsetToPosition(tester, 2); // Index of 'c'.
+    final Offset gPos = textOffsetToPosition(tester, 8); // Index of 'g'.
+    final Offset hPos = textOffsetToPosition(tester, 9); // Index of 'h'.
+
+    // Drag from 'c' to 'g'.
+    final TestGesture gesture = await tester.startGesture(cPos, kind: PointerDeviceKind.mouse);
+    await tester.pump();
+    await gesture.moveTo(gPos);
+    await tester.pumpAndSettle();
+
+    expect(selectionChangedCount, isNonZero);
+    selectionChangedCount = 0;
+    expect(controller.selection.baseOffset, 2);
+    expect(controller.selection.extentOffset, 8);
+
+    // Tiny movement shouldn't cause text selection to change.
+    await gesture.moveTo(gPos + const Offset(4.0, 0.0));
+    await tester.pumpAndSettle();
+    expect(selectionChangedCount, 0);
+
+    // Now a text selection change will occur after a significant movement.
+    await gesture.moveTo(hPos);
+    await tester.pump();
+    await gesture.up();
+    await tester.pumpAndSettle();
+
+    expect(selectionChangedCount, 1);
+    expect(controller.selection.baseOffset, 2);
+    expect(controller.selection.extentOffset, 9);
+  });
+
   testWidgets(
     'text field respects theme',
     (WidgetTester tester) async {