Fix edge scrolling on platforms that select word by word on long press move (#113128)

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

@@ -1035,16 +1035,12 @@ class _CupertinoTextFieldState extends State<CupertinoTextField> with Restoratio
     switch (defaultTargetPlatform) {
       case TargetPlatform.iOS:
       case TargetPlatform.macOS:
-        if (cause == SelectionChangedCause.longPress
-            || cause == SelectionChangedCause.drag) {
-          _editableText.bringIntoView(selection.extent);
-        }
-        break;
       case TargetPlatform.linux:
       case TargetPlatform.windows:
       case TargetPlatform.fuchsia:
       case TargetPlatform.android:
-        if (cause == SelectionChangedCause.drag) {
+        if (cause == SelectionChangedCause.longPress
+            || cause == SelectionChangedCause.drag) {
           _editableText.bringIntoView(selection.extent);
         }
         break;

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

@@ -62,45 +62,6 @@ class _TextFieldSelectionGestureDetectorBuilder extends TextSelectionGestureDete
     // Not required.
   }
 
-  @override
-  void onSingleLongTapMoveUpdate(LongPressMoveUpdateDetails details) {
-    if (delegate.selectionEnabled) {
-      final TargetPlatform targetPlatform = Theme.of(_state.context).platform;
-
-      switch (targetPlatform) {
-        case TargetPlatform.iOS:
-        case TargetPlatform.macOS:
-          renderEditable.selectPositionAt(
-            from: details.globalPosition,
-            cause: SelectionChangedCause.longPress,
-          );
-          break;
-        case TargetPlatform.android:
-        case TargetPlatform.fuchsia:
-        case TargetPlatform.linux:
-        case TargetPlatform.windows:
-          renderEditable.selectWordsInRange(
-            from: details.globalPosition - details.offsetFromOrigin,
-            to: details.globalPosition,
-            cause: SelectionChangedCause.longPress,
-          );
-          break;
-      }
-
-      switch (targetPlatform) {
-        case TargetPlatform.android:
-        case TargetPlatform.iOS:
-          editableText.showMagnifier(details.globalPosition);
-          break;
-        case TargetPlatform.fuchsia:
-        case TargetPlatform.linux:
-        case TargetPlatform.macOS:
-        case TargetPlatform.windows:
-          break;
-      }
-    }
-  }
-
   @override
   void onSingleTapUp(TapUpDetails details) {
     super.onSingleTapUp(details);
@@ -110,37 +71,19 @@ class _TextFieldSelectionGestureDetectorBuilder extends TextSelectionGestureDete
 
   @override
   void onSingleLongTapStart(LongPressStartDetails details) {
+    super.onSingleLongTapStart(details);
     if (delegate.selectionEnabled) {
-      final TargetPlatform targetPlatform = Theme.of(_state.context).platform;
-
-      switch (targetPlatform) {
+      switch (Theme.of(_state.context).platform) {
         case TargetPlatform.iOS:
         case TargetPlatform.macOS:
-          renderEditable.selectPositionAt(
-            from: details.globalPosition,
-            cause: SelectionChangedCause.longPress,
-          );
           break;
         case TargetPlatform.android:
         case TargetPlatform.fuchsia:
         case TargetPlatform.linux:
         case TargetPlatform.windows:
-          renderEditable.selectWord(cause: SelectionChangedCause.longPress);
           Feedback.forLongPress(_state.context);
           break;
       }
-
-      switch (targetPlatform) {
-        case TargetPlatform.android:
-        case TargetPlatform.iOS:
-          editableText.showMagnifier(details.globalPosition);
-          break;
-        case TargetPlatform.fuchsia:
-        case TargetPlatform.linux:
-        case TargetPlatform.macOS:
-        case TargetPlatform.windows:
-          break;
-      }
     }
   }
 }
@@ -1150,16 +1093,12 @@ class _TextFieldState extends State<TextField> with RestorationMixin implements
     switch (Theme.of(context).platform) {
       case TargetPlatform.iOS:
       case TargetPlatform.macOS:
-        if (cause == SelectionChangedCause.longPress
-            || cause == SelectionChangedCause.drag) {
-          _editableText?.bringIntoView(selection.extent);
-        }
-        break;
       case TargetPlatform.linux:
       case TargetPlatform.windows:
       case TargetPlatform.fuchsia:
       case TargetPlatform.android:
-        if (cause == SelectionChangedCause.drag) {
+        if (cause == SelectionChangedCause.longPress
+            || cause == SelectionChangedCause.drag) {
           _editableText?.bringIntoView(selection.extent);
         }
         break;

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

@@ -1996,10 +1996,21 @@ class TextSelectionGestureDetectorBuilder {
   @protected
   void onSingleLongTapStart(LongPressStartDetails details) {
     if (delegate.selectionEnabled) {
-      renderEditable.selectPositionAt(
-        from: details.globalPosition,
-        cause: SelectionChangedCause.longPress,
-      );
+      switch (defaultTargetPlatform) {
+        case TargetPlatform.iOS:
+        case TargetPlatform.macOS:
+          renderEditable.selectPositionAt(
+            from: details.globalPosition,
+            cause: SelectionChangedCause.longPress,
+          );
+          break;
+        case TargetPlatform.android:
+        case TargetPlatform.fuchsia:
+        case TargetPlatform.linux:
+        case TargetPlatform.windows:
+          renderEditable.selectWord(cause: SelectionChangedCause.longPress);
+          break;
+      }
 
       switch (defaultTargetPlatform) {
         case TargetPlatform.android:
@@ -2012,6 +2023,9 @@ class TextSelectionGestureDetectorBuilder {
         case TargetPlatform.windows:
           break;
       }
+
+      _dragStartViewportOffset = renderEditable.offset.pixels;
+      _dragStartScrollOffset = _scrollPosition;
     }
   }
 
@@ -2027,11 +2041,35 @@ class TextSelectionGestureDetectorBuilder {
   @protected
   void onSingleLongTapMoveUpdate(LongPressMoveUpdateDetails details) {
     if (delegate.selectionEnabled) {
-      renderEditable.selectPositionAt(
-        from: details.globalPosition,
-        cause: SelectionChangedCause.longPress,
+      // Adjust the drag start offset for possible viewport offset changes.
+      final Offset editableOffset = renderEditable.maxLines == 1
+          ? Offset(renderEditable.offset.pixels - _dragStartViewportOffset, 0.0)
+          : Offset(0.0, renderEditable.offset.pixels - _dragStartViewportOffset);
+      final Offset scrollableOffset = Offset(
+        0.0,
+        _scrollPosition - _dragStartScrollOffset,
       );
 
+      switch (defaultTargetPlatform) {
+        case TargetPlatform.iOS:
+        case TargetPlatform.macOS:
+          renderEditable.selectPositionAt(
+            from: details.globalPosition,
+            cause: SelectionChangedCause.longPress,
+          );
+          break;
+        case TargetPlatform.android:
+        case TargetPlatform.fuchsia:
+        case TargetPlatform.linux:
+        case TargetPlatform.windows:
+          renderEditable.selectWordsInRange(
+            from: details.globalPosition - details.offsetFromOrigin - editableOffset - scrollableOffset,
+            to: details.globalPosition,
+            cause: SelectionChangedCause.longPress,
+          );
+          break;
+      }
+
       switch (defaultTargetPlatform) {
         case TargetPlatform.android:
         case TargetPlatform.iOS:
@@ -2070,6 +2108,8 @@ class TextSelectionGestureDetectorBuilder {
     if (shouldShowSelectionToolbar) {
       editableText.showToolbar();
     }
+    _dragStartViewportOffset = 0.0;
+    _dragStartScrollOffset = 0.0;
   }
 
   /// Handler for [TextSelectionGestureDetector.onSecondaryTap].

packages/flutter/test/material/text_field_test.dart

@@ -2254,7 +2254,123 @@ void main() {
     expect(controller.selection.extentOffset, testValue.indexOf('g'));
   });
 
-  testWidgets('Can drag handles to change selection', (WidgetTester tester) async {
+  testWidgets('Can drag handles to change selection on Apple platforms', (WidgetTester tester) async {
+    final TextEditingController controller = TextEditingController();
+
+    await tester.pumpWidget(
+      overlay(
+        child: TextField(
+          dragStartBehavior: DragStartBehavior.down,
+          controller: controller,
+        ),
+      ),
+    );
+
+    const String testValue = 'abc def ghi';
+    await tester.enterText(find.byType(TextField), testValue);
+    await skipPastScrollingAnimation(tester);
+
+    // Double tap the 'e' to select 'def'.
+    final Offset ePos = textOffsetToPosition(tester, testValue.indexOf('e'));
+    // The first tap.
+    TestGesture gesture = await tester.startGesture(ePos, pointer: 7);
+    await tester.pump();
+    await gesture.up();
+    await tester.pump();
+    await tester.pump(const Duration(milliseconds: 200)); // skip past the frame where the opacity is zero
+
+    // The second tap.
+    await gesture.down(ePos);
+    await tester.pump();
+    await gesture.up();
+    await tester.pump();
+
+    final TextSelection selection = controller.selection;
+    expect(selection.baseOffset, 4);
+    expect(selection.extentOffset, 7);
+
+    final RenderEditable renderEditable = findRenderEditable(tester);
+    List<TextSelectionPoint> endpoints = globalize(
+      renderEditable.getEndpointsForSelection(selection),
+      renderEditable,
+    );
+    expect(endpoints.length, 2);
+
+    // Drag the right handle 2 letters to the right.
+    // We use a small offset because the endpoint is on the very corner
+    // of the handle.
+    Offset handlePos = endpoints[1].point + const Offset(1.0, 1.0);
+    Offset newHandlePos = textOffsetToPosition(tester, testValue.length);
+    gesture = await tester.startGesture(handlePos, pointer: 7);
+    await tester.pump();
+    await gesture.moveTo(newHandlePos);
+    await tester.pump();
+    await gesture.up();
+    await tester.pump();
+
+    expect(controller.selection.baseOffset, 4);
+    expect(controller.selection.extentOffset, 11);
+
+    // Drag the left handle 2 letters to the left.
+    handlePos = endpoints[0].point + const Offset(-1.0, 1.0);
+    newHandlePos = textOffsetToPosition(tester, 2);
+    gesture = await tester.startGesture(handlePos, pointer: 7);
+    await tester.pump();
+    await gesture.moveTo(newHandlePos);
+    await tester.pump();
+    await gesture.up();
+    await tester.pump();
+
+    switch (defaultTargetPlatform) {
+      // On Apple platforms, dragging the base handle makes it the extent.
+      case TargetPlatform.iOS:
+      case TargetPlatform.macOS:
+        expect(controller.selection.baseOffset, 11);
+        expect(controller.selection.extentOffset, 2);
+        break;
+      case TargetPlatform.android:
+      case TargetPlatform.fuchsia:
+      case TargetPlatform.linux:
+      case TargetPlatform.windows:
+        expect(controller.selection.baseOffset, 2);
+        expect(controller.selection.extentOffset, 11);
+        break;
+    }
+
+    // Drag the left handle 2 letters to the left again.
+    endpoints = globalize(
+      renderEditable.getEndpointsForSelection(controller.selection),
+      renderEditable,
+    );
+    handlePos = endpoints[0].point + const Offset(-1.0, 1.0);
+    newHandlePos = textOffsetToPosition(tester, 0);
+    gesture = await tester.startGesture(handlePos, pointer: 7);
+    await tester.pump();
+    await gesture.moveTo(newHandlePos);
+    await tester.pump();
+    await gesture.up();
+    await tester.pump();
+
+    switch (defaultTargetPlatform) {
+      case TargetPlatform.iOS:
+      case TargetPlatform.macOS:
+        // The left handle was already the extent, and it remains so.
+        expect(controller.selection.baseOffset, 11);
+        expect(controller.selection.extentOffset, 0);
+        break;
+      case TargetPlatform.android:
+      case TargetPlatform.fuchsia:
+      case TargetPlatform.linux:
+      case TargetPlatform.windows:
+        expect(controller.selection.baseOffset, 0);
+        expect(controller.selection.extentOffset, 11);
+        break;
+    }
+  },
+    variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS, TargetPlatform.macOS }),
+  );
+
+  testWidgets('Can drag handles to change selection on non-Apple platforms', (WidgetTester tester) async {
     final TextEditingController controller = TextEditingController();
 
     await tester.pumpWidget(
@@ -2360,7 +2476,7 @@ void main() {
         break;
     }
   },
-    variant: TargetPlatformVariant.all(),
+    variant: TargetPlatformVariant.all(excluding: <TargetPlatform>{ TargetPlatform.iOS, TargetPlatform.macOS }),
   );
 
   testWidgets('Cannot drag one handle past the other', (WidgetTester tester) async {
@@ -8578,7 +8694,95 @@ void main() {
     variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS,  TargetPlatform.macOS }),
   );
 
-  testWidgets('long press drag can edge scroll', (WidgetTester tester) async {
+  testWidgets('long press drag can edge scroll on non-Apple platforms', (WidgetTester tester) async {
+    final TextEditingController controller = TextEditingController(
+      text: 'Atwater Peel Sherbrooke Bonaventure Angrignon Peel Côte-des-Neiges',
+    );
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Material(
+          child: Center(
+            child: TextField(
+              controller: controller,
+            ),
+          ),
+        ),
+      ),
+    );
+
+    final RenderEditable renderEditable = findRenderEditable(tester);
+
+    List<TextSelectionPoint> lastCharEndpoint = renderEditable.getEndpointsForSelection(
+      const TextSelection.collapsed(offset: 66), // Last character's position.
+    );
+
+    expect(lastCharEndpoint.length, 1);
+    // Just testing the test and making sure that the last character is off
+    // the right side of the screen.
+    expect(lastCharEndpoint[0].point.dx, 1056);
+
+    final Offset textfieldStart = tester.getTopLeft(find.byType(TextField));
+
+    final TestGesture gesture =
+        await tester.startGesture(textfieldStart);
+    await tester.pump(const Duration(milliseconds: 500));
+
+    expect(
+      controller.selection,
+      const TextSelection(baseOffset: 0, extentOffset: 7, affinity: TextAffinity.upstream),
+    );
+    expect(find.byType(TextButton), findsNothing);
+
+    await gesture.moveBy(const Offset(900, 5));
+    // To the edge of the screen basically.
+    await tester.pump();
+    expect(
+      controller.selection,
+      const TextSelection(baseOffset: 0, extentOffset: 59),
+    );
+    // Keep moving out.
+    await gesture.moveBy(const Offset(1, 0));
+    await tester.pump();
+    expect(
+      controller.selection,
+      const TextSelection(baseOffset: 0, extentOffset: 66),
+    );
+    await gesture.moveBy(const Offset(1, 0));
+    await tester.pump();
+    expect(
+      controller.selection,
+      const TextSelection(baseOffset: 0, extentOffset: 66, affinity: TextAffinity.upstream),
+    ); // We're at the edge now.
+    expect(find.byType(TextButton), findsNothing);
+
+    await gesture.up();
+    await tester.pumpAndSettle();
+
+    // The selection isn't affected by the gesture lift.
+    expect(
+      controller.selection,
+      const TextSelection(baseOffset: 0, extentOffset: 66, affinity: TextAffinity.upstream),
+    );
+    // The toolbar now shows up.
+    expect(find.byType(TextButton), isContextMenuProvidedByPlatform ? findsNothing : findsNWidgets(3));
+
+    lastCharEndpoint = renderEditable.getEndpointsForSelection(
+      const TextSelection.collapsed(offset: 66), // Last character's position.
+    );
+
+    expect(lastCharEndpoint.length, 1);
+    // The last character is now on screen near the right edge.
+    expect(lastCharEndpoint[0].point.dx, moreOrLessEquals(798, epsilon: 1));
+
+    final List<TextSelectionPoint> firstCharEndpoint = renderEditable.getEndpointsForSelection(
+      const TextSelection.collapsed(offset: 0), // First character's position.
+    );
+    expect(firstCharEndpoint.length, 1);
+    // The first character is now offscreen to the left.
+    expect(firstCharEndpoint[0].point.dx, moreOrLessEquals(-257.0, epsilon: 1));
+  }, variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.android, TargetPlatform.fuchsia, TargetPlatform.linux, TargetPlatform.windows }));
+
+  testWidgets('long press drag can edge scroll on Apple platforms', (WidgetTester tester) async {
     final TextEditingController controller = TextEditingController(
       text: 'Atwater Peel Sherbrooke Bonaventure Angrignon Peel Côte-des-Neiges',
     );

packages/flutter/test/widgets/text_selection_test.dart

@@ -433,7 +433,7 @@ void main() {
     expect(dragEndCount, 1);
   });
 
-  testWidgets('test TextSelectionGestureDetectorBuilder long press', (WidgetTester tester) async {
+  testWidgets('test TextSelectionGestureDetectorBuilder long press on Apple Platforms', (WidgetTester tester) async {
     await pumpTextSelectionGestureDetectorBuilder(tester);
     final TestGesture gesture = await tester.startGesture(
       const Offset(200.0, 200.0),
@@ -447,7 +447,23 @@ void main() {
     final FakeRenderEditable renderEditable = tester.renderObject(find.byType(FakeEditable));
     expect(state.showToolbarCalled, isTrue);
     expect(renderEditable.selectPositionAtCalled, isTrue);
-  });
+  }, variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS, TargetPlatform.macOS }));
+
+  testWidgets('test TextSelectionGestureDetectorBuilder long press on non-Apple Platforms', (WidgetTester tester) async {
+    await pumpTextSelectionGestureDetectorBuilder(tester);
+    final TestGesture gesture = await tester.startGesture(
+      const Offset(200.0, 200.0),
+      pointer: 0,
+    );
+    await tester.pump(const Duration(seconds: 2));
+    await gesture.up();
+    await tester.pumpAndSettle();
+
+    final FakeEditableTextState state = tester.state(find.byType(FakeEditableText));
+    final FakeRenderEditable renderEditable = tester.renderObject(find.byType(FakeEditable));
+    expect(state.showToolbarCalled, isTrue);
+    expect(renderEditable.selectWordCalled, isTrue);
+  }, variant: TargetPlatformVariant.all(excluding: <TargetPlatform>{ TargetPlatform.iOS, TargetPlatform.macOS }));
 
   testWidgets('TextSelectionGestureDetectorBuilder right click Apple platforms', (WidgetTester tester) async {
     // Regression test for https://github.com/flutter/flutter/issues/80119