fix stretch effect with rtl support (#113214)

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

@@ -744,7 +744,7 @@ class _StretchingOverscrollIndicatorState extends State<StretchingOverscrollIndi
     return false;
   }
 
-  AlignmentDirectional _getAlignmentForAxisDirection(double overscroll) {
+  AlignmentGeometry _getAlignmentForAxisDirection(double overscroll) {
     // Accounts for reversed scrollables by checking the AxisDirection
     switch (widget.axisDirection) {
       case AxisDirection.up:
@@ -753,16 +753,16 @@ class _StretchingOverscrollIndicatorState extends State<StretchingOverscrollIndi
             : AlignmentDirectional.bottomCenter;
       case AxisDirection.right:
         return overscroll > 0
-            ? AlignmentDirectional.centerEnd
-            : AlignmentDirectional.centerStart;
+            ? Alignment.centerRight
+            : Alignment.centerLeft;
       case AxisDirection.down:
         return overscroll > 0
             ? AlignmentDirectional.bottomCenter
             : AlignmentDirectional.topCenter;
       case AxisDirection.left:
         return overscroll > 0
-            ? AlignmentDirectional.centerStart
-            : AlignmentDirectional.centerEnd;
+            ? Alignment.centerLeft
+            : Alignment.centerRight;
     }
   }
 
@@ -796,7 +796,7 @@ class _StretchingOverscrollIndicatorState extends State<StretchingOverscrollIndi
               break;
           }
 
-          final AlignmentDirectional alignment = _getAlignmentForAxisDirection(
+          final AlignmentGeometry alignment = _getAlignmentForAxisDirection(
             _lastOverscrollNotification?.overscroll ?? 0.0
           );
 

packages/flutter/test/widgets/overscroll_stretch_indicator_test.dart

@@ -18,11 +18,16 @@ void main() {
     ScrollController controller, {
     Axis axis = Axis.vertical,
     bool reverse = false,
+    TextDirection textDirection = TextDirection.ltr,
   }) {
     final AxisDirection axisDirection;
     switch (axis) {
       case Axis.horizontal:
+        if (textDirection == TextDirection.rtl) {
+          axisDirection = reverse ? AxisDirection.right : AxisDirection.left;
+        } else {
           axisDirection = reverse ? AxisDirection.left : AxisDirection.right;
+        }
         break;
       case Axis.vertical:
         axisDirection = reverse ? AxisDirection.up : AxisDirection.down;
@@ -30,7 +35,7 @@ void main() {
     }
 
     return Directionality(
-      textDirection: TextDirection.ltr,
+      textDirection: textDirection,
       child: MediaQuery(
         data: const MediaQueryData(size: Size(800.0, 600.0)),
         child: ScrollConfiguration(
@@ -218,6 +223,92 @@ void main() {
     );
   });
 
+  testWidgets('Stretch overscroll works in reverse - horizontal - RTL', (WidgetTester tester) async {
+    final GlobalKey box1Key = GlobalKey();
+    final GlobalKey box2Key = GlobalKey();
+    final GlobalKey box3Key = GlobalKey();
+    final ScrollController controller = ScrollController();
+    await tester.pumpWidget(
+      buildTest(
+        box1Key,
+        box2Key,
+        box3Key,
+        controller,
+        axis: Axis.horizontal,
+        reverse: true,
+        textDirection: TextDirection.rtl,
+      )
+    );
+
+    expect(find.byType(StretchingOverscrollIndicator), findsOneWidget);
+    expect(find.byType(GlowingOverscrollIndicator), findsNothing);
+    final RenderBox box1 = tester.renderObject(find.byKey(box1Key));
+    final RenderBox box2 = tester.renderObject(find.byKey(box2Key));
+    final RenderBox box3 = tester.renderObject(find.byKey(box3Key));
+
+    expect(controller.offset, 0.0);
+    expect(box1.localToGlobal(Offset.zero), Offset.zero);
+    expect(box2.localToGlobal(Offset.zero), const Offset(300.0, 0.0));
+    expect(box3.localToGlobal(Offset.zero), const Offset(600.0, 0.0));
+    await expectLater(
+      find.byType(CustomScrollView),
+      matchesGoldenFile('overscroll_stretch.horizontal.reverse.rtl.start.png'),
+    );
+
+    TestGesture gesture = await tester.startGesture(tester.getCenter(find.byType(CustomScrollView)));
+    // Overscroll the start
+    await gesture.moveBy(const Offset(200.0, 0.0));
+    await tester.pumpAndSettle();
+
+    expect(box1.localToGlobal(Offset.zero), Offset.zero);
+    expect(box2.localToGlobal(Offset.zero).dx, greaterThan(305.0));
+    expect(box3.localToGlobal(Offset.zero).dx, greaterThan(610.0));
+    await expectLater(
+      find.byType(CustomScrollView),
+      matchesGoldenFile('overscroll_stretch.horizontal.reverse.rtl.start.stretched.png'),
+    );
+
+    await gesture.up();
+    await tester.pumpAndSettle();
+
+    // Stretch released back to the start
+    expect(box1.localToGlobal(Offset.zero), Offset.zero);
+    expect(box2.localToGlobal(Offset.zero), const Offset(300.0, 0.0));
+    expect(box3.localToGlobal(Offset.zero), const Offset(600.0, 0.0));
+
+    // Jump to end of the list
+    controller.jumpTo(controller.position.maxScrollExtent);
+    await tester.pumpAndSettle();
+    expect(controller.offset, 100.0);
+    expect(box1.localToGlobal(Offset.zero).dx, -100.0);
+    expect(box2.localToGlobal(Offset.zero).dx, 200.0);
+    expect(box3.localToGlobal(Offset.zero).dx, 500.0);
+    await expectLater(
+      find.byType(CustomScrollView),
+      matchesGoldenFile('overscroll_stretch.horizontal.reverse.rtl.end.png'),
+    );
+
+    gesture = await tester.startGesture(tester.getCenter(find.byType(CustomScrollView)));
+    // Overscroll the end
+    await gesture.moveBy(const Offset(-200.0, 0.0));
+    await tester.pumpAndSettle();
+    expect(box1.localToGlobal(Offset.zero).dx, lessThan(-116.0));
+    expect(box2.localToGlobal(Offset.zero).dx, lessThan(190.0));
+    expect(box3.localToGlobal(Offset.zero).dx, lessThan(500.0));
+    await expectLater(
+      find.byType(CustomScrollView),
+      matchesGoldenFile('overscroll_stretch.horizontal.reverse.rtl.end.stretched.png'),
+    );
+
+    await gesture.up();
+    await tester.pumpAndSettle();
+
+    // Stretch released back
+    expect(box1.localToGlobal(Offset.zero).dx, -100.0);
+    expect(box2.localToGlobal(Offset.zero).dx, 200.0);
+    expect(box3.localToGlobal(Offset.zero).dx, 500.0);
+  });
+
   testWidgets('Stretch overscroll horizontally', (WidgetTester tester) async {
     final GlobalKey box1Key = GlobalKey();
     final GlobalKey box2Key = GlobalKey();
@@ -295,6 +386,46 @@ void main() {
     expect(box3.localToGlobal(Offset.zero).dx, 500.0);
   });
 
+  testWidgets('Stretch overscroll horizontally RTl', (WidgetTester tester) async {
+    final GlobalKey box1Key = GlobalKey();
+    final GlobalKey box2Key = GlobalKey();
+    final GlobalKey box3Key = GlobalKey();
+    final ScrollController controller = ScrollController();
+    await tester.pumpWidget(
+      buildTest(
+        box1Key,
+        box2Key,
+        box3Key,
+        controller,
+        axis: Axis.horizontal,
+        textDirection: TextDirection.rtl,
+      )
+    );
+
+    expect(find.byType(StretchingOverscrollIndicator), findsOneWidget);
+    expect(find.byType(GlowingOverscrollIndicator), findsNothing);
+    final RenderBox box1 = tester.renderObject(find.byKey(box1Key));
+    final RenderBox box2 = tester.renderObject(find.byKey(box2Key));
+    final RenderBox box3 = tester.renderObject(find.byKey(box3Key));
+
+    expect(controller.offset, 0.0);
+    expect(box1.localToGlobal(Offset.zero), const Offset(500.0, 0.0));
+    expect(box2.localToGlobal(Offset.zero), const Offset(200.0, 0.0));
+    expect(box3.localToGlobal(Offset.zero), const Offset(-100.0, 0.0));
+
+    final TestGesture gesture = await tester.startGesture(tester.getCenter(find.byType(CustomScrollView)));
+    // Overscroll
+    await gesture.moveBy(const Offset(-200.0, 0.0));
+    await tester.pumpAndSettle();
+    expect(box1.localToGlobal(Offset.zero).dx, lessThan(500.0));
+    expect(box2.localToGlobal(Offset.zero).dx, lessThan(200.0));
+    expect(box3.localToGlobal(Offset.zero).dx, lessThan(-100.0));
+    await expectLater(
+      find.byType(CustomScrollView),
+      matchesGoldenFile('overscroll_stretch.horizontal.rtl.png'),
+    );
+  });
+
   testWidgets('Disallow stretching overscroll', (WidgetTester tester) async {
     final GlobalKey box1Key = GlobalKey();
     final GlobalKey box2Key = GlobalKey();