[New Feature]Support mouse wheel event on the scrollbar widget (#109659)

* rebase master and add a test

* fix the test

* fix the test

* fix the test

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

@@ -1458,13 +1458,17 @@ class RawScrollbar extends StatefulWidget {
 /// scrollbar track.
 class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProviderStateMixin<T> {
   Offset? _startDragScrollbarAxisOffset;
+  Offset? _lastDragUpdateOffset;
   double? _startDragThumbOffset;
-  ScrollController? _currentController;
+  ScrollController? _cachedController;
   Timer? _fadeoutTimer;
   late AnimationController _fadeoutAnimationController;
   late Animation<double> _fadeoutOpacityAnimation;
   final GlobalKey  _scrollbarPainterKey = GlobalKey();
   bool _hoverIsActive = false;
+  bool _thumbDragging = false;
+
+  ScrollController? get _effectiveScrollController => widget.controller ?? PrimaryScrollController.maybeOf(context);
 
   /// Used to paint the scrollbar.
   ///
@@ -1550,12 +1554,11 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
   }
 
   void _validateInteractions(AnimationStatus status) {
-    final ScrollController? scrollController = widget.controller ?? PrimaryScrollController.maybeOf(context);
     if (status == AnimationStatus.dismissed) {
       assert(_fadeoutOpacityAnimation.value == 0.0);
       // We do not check for a valid scroll position if the scrollbar is not
       // visible, because it cannot be interacted with.
-    } else if (scrollController != null && enableGestures) {
+    } else if (_effectiveScrollController != null && enableGestures) {
       // Interactive scrollbars need to be properly configured. If it is visible
       // for interaction, ensure we are set up properly.
       assert(_debugCheckHasValidScrollPosition());
@@ -1566,7 +1569,7 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
     if (!mounted) {
       return true;
     }
-    final ScrollController? scrollController = widget.controller ?? PrimaryScrollController.maybeOf(context);
+    final ScrollController? scrollController = _effectiveScrollController;
     final bool tryPrimary = widget.controller == null;
     final String controllerForError = tryPrimary
       ? 'PrimaryScrollController'
@@ -1698,11 +1701,11 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
   }
 
   void _updateScrollPosition(Offset updatedOffset) {
-    assert(_currentController != null);
+    assert(_cachedController != null);
     assert(_startDragScrollbarAxisOffset != null);
     assert(_startDragThumbOffset != null);
 
-    final ScrollPosition position = _currentController!.position;
+    final ScrollPosition position = _cachedController!.position;
     late double primaryDelta;
     switch (position.axisDirection) {
       case AxisDirection.up:
@@ -1761,9 +1764,9 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
   /// current scroll controller does not have any attached positions.
   @protected
   Axis? getScrollbarDirection() {
-    assert(_currentController != null);
+    assert(_cachedController != null);
-    if (_currentController!.hasClients) {
+    if (_cachedController!.hasClients) {
-      return _currentController!.position.axis;
+      return _cachedController!.position.axis;
     }
     return null;
   }
@@ -1788,7 +1791,7 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
   @mustCallSuper
   void handleThumbPressStart(Offset localPosition) {
     assert(_debugCheckHasValidScrollPosition());
-    _currentController = widget.controller ?? PrimaryScrollController.maybeOf(context);
+    _cachedController = _effectiveScrollController;
     final Axis? direction = getScrollbarDirection();
     if (direction == null) {
       return;
@@ -1797,6 +1800,7 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
     _fadeoutAnimationController.forward();
     _startDragScrollbarAxisOffset = localPosition;
     _startDragThumbOffset = scrollbarPainter.getThumbScrollOffset();
+    _thumbDragging = true;
   }
 
   /// Handler called when a currently active long press gesture moves.
@@ -1806,7 +1810,11 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
   @mustCallSuper
   void handleThumbPressUpdate(Offset localPosition) {
     assert(_debugCheckHasValidScrollPosition());
-    final ScrollPosition position = _currentController!.position;
+    if (_lastDragUpdateOffset == localPosition) {
+      return;
+    }
+    _lastDragUpdateOffset = localPosition;
+    final ScrollPosition position = _cachedController!.position;
     if (!position.physics.shouldAcceptUserOffset(position)) {
       return;
     }
@@ -1822,22 +1830,24 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
   @mustCallSuper
   void handleThumbPressEnd(Offset localPosition, Velocity velocity) {
     assert(_debugCheckHasValidScrollPosition());
+    _thumbDragging = false;
     final Axis? direction = getScrollbarDirection();
     if (direction == null) {
       return;
     }
     _maybeStartFadeoutTimer();
     _startDragScrollbarAxisOffset = null;
+    _lastDragUpdateOffset = null;
     _startDragThumbOffset = null;
-    _currentController = null;
+    _cachedController = null;
   }
 
   void _handleTrackTapDown(TapDownDetails details) {
     // The Scrollbar should page towards the position of the tap on the track.
     assert(_debugCheckHasValidScrollPosition());
-    _currentController = widget.controller ?? PrimaryScrollController.maybeOf(context);
+    _cachedController = _effectiveScrollController;
 
-    final ScrollPosition position = _currentController!.position;
+    final ScrollPosition position = _cachedController!.position;
     if (!position.physics.shouldAcceptUserOffset(position)) {
       return;
     }
@@ -1845,22 +1855,22 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
     double scrollIncrement;
     // Is an increment calculator available?
     final ScrollIncrementCalculator? calculator = Scrollable.maybeOf(
-      _currentController!.position.context.notificationContext!,
+      _cachedController!.position.context.notificationContext!,
     )?.widget.incrementCalculator;
     if (calculator != null) {
       scrollIncrement = calculator(
         ScrollIncrementDetails(
           type: ScrollIncrementType.page,
-          metrics: _currentController!.position,
+          metrics: _cachedController!.position,
         ),
       );
     } else {
       // Default page increment
-      scrollIncrement = 0.8 * _currentController!.position.viewportDimension;
+      scrollIncrement = 0.8 * _cachedController!.position.viewportDimension;
     }
 
     // Adjust scrollIncrement for direction
-    switch (_currentController!.position.axisDirection) {
+    switch (_cachedController!.position.axisDirection) {
       case AxisDirection.up:
         if (details.localPosition.dy > scrollbarPainter._thumbOffset) {
           scrollIncrement = -scrollIncrement;
@@ -1883,8 +1893,8 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
         break;
     }
 
-    _currentController!.position.moveTo(
+    _cachedController!.position.moveTo(
-      _currentController!.position.pixels + scrollIncrement,
+      _cachedController!.position.pixels + scrollIncrement,
       duration: const Duration(milliseconds: 100),
       curve: Curves.easeInOut,
     );
@@ -1892,8 +1902,7 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
 
   // ScrollController takes precedence over ScrollNotification
   bool _shouldUpdatePainter(Axis notificationAxis) {
-    final ScrollController? scrollController = widget.controller ??
+    final ScrollController? scrollController = _effectiveScrollController;
-        PrimaryScrollController.maybeOf(context);
     // Only update the painter of this scrollbar if the notification
     // metrics do not conflict with the information we have from the scroll
     // controller.
@@ -1979,8 +1988,7 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
 
   Map<Type, GestureRecognizerFactory> get _gestures {
     final Map<Type, GestureRecognizerFactory> gestures = <Type, GestureRecognizerFactory>{};
-    final ScrollController? controller = widget.controller ?? PrimaryScrollController.maybeOf(context);
+    if (_effectiveScrollController == null || !enableGestures) {
-    if (controller == null || !enableGestures) {
       return gestures;
     }
 
@@ -2086,6 +2094,64 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
     _maybeStartFadeoutTimer();
   }
 
+  // Returns the delta that should result from applying [event] with axis and
+  // direction taken into account.
+  double _pointerSignalEventDelta(PointerScrollEvent event) {
+    assert(_cachedController != null);
+    double delta = _cachedController!.position.axis == Axis.horizontal
+      ? event.scrollDelta.dx
+      : event.scrollDelta.dy;
+
+    if (axisDirectionIsReversed(_cachedController!.position.axisDirection)) {
+      delta *= -1;
+    }
+    return delta;
+  }
+
+  // Returns the offset that should result from applying [event] to the current
+  // position, taking min/max scroll extent into account.
+  double _targetScrollOffsetForPointerScroll(double delta) {
+    assert(_cachedController != null);
+    return math.min(
+      math.max(_cachedController!.position.pixels + delta, _cachedController!.position.minScrollExtent),
+      _cachedController!.position.maxScrollExtent,
+    );
+  }
+
+  void _handlePointerScroll(PointerEvent event) {
+    assert(event is PointerScrollEvent);
+    _cachedController = _effectiveScrollController;
+    final double delta = _pointerSignalEventDelta(event as PointerScrollEvent);
+    final double targetScrollOffset = _targetScrollOffsetForPointerScroll(delta);
+    if (delta != 0.0 && targetScrollOffset != _cachedController!.position.pixels) {
+      _cachedController!.position.pointerScroll(delta);
+    }
+  }
+
+  void _receivedPointerSignal(PointerSignalEvent event) {
+    _cachedController = _effectiveScrollController;
+    // Only try to scroll if the bar absorb the hit test.
+    if ((scrollbarPainter.hitTest(event.localPosition) ?? false) &&
+        _cachedController != null &&
+        _cachedController!.hasClients &&
+        (!_thumbDragging || kIsWeb)) {
+      final ScrollPosition position = _cachedController!.position;
+      if (event is PointerScrollEvent && position != null) {
+        if (!position.physics.shouldAcceptUserOffset(position)) {
+          return;
+        }
+        final double delta = _pointerSignalEventDelta(event);
+        final double targetScrollOffset = _targetScrollOffsetForPointerScroll(delta);
+        if (delta != 0.0 && targetScrollOffset != position.pixels) {
+          GestureBinding.instance.pointerSignalResolver.register(event, _handlePointerScroll);
+        }
+      } else if (event is PointerScrollInertiaCancelEvent) {
+        position.jumpTo(position.pixels);
+        // Don't use the pointer signal resolver, all hit-tested scrollables should stop.
+      }
+    }
+  }
+
   @override
   void dispose() {
     _fadeoutAnimationController.dispose();
@@ -2103,6 +2169,8 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
       child: NotificationListener<ScrollNotification>(
         onNotification: _handleScrollNotification,
         child: RepaintBoundary(
+          child: Listener(
+            onPointerSignal: _receivedPointerSignal,
             child: RawGestureDetector(
               gestures: _gestures,
               child: MouseRegion(
@@ -2145,6 +2213,7 @@ class RawScrollbarState<T extends RawScrollbar> extends State<T> with TickerProv
             ),
           ),
         ),
+      ),
     );
   }
 }

packages/flutter/test/cupertino/scrollbar_test.dart

@@ -1200,6 +1200,8 @@ void main() {
     pointer.hover(const Offset(793.0, 15.0));
     await tester.sendEventToBinding(pointer.scroll(const Offset(0.0, 20.0)));
     await tester.pumpAndSettle();
+
+    if (!kIsWeb) {
       // Scrolling while holding the drag on the scrollbar and still hovered over
       // the scrollbar should not have changed the scroll offset.
       expect(pointer.location, const Offset(793.0, 15.0));
@@ -1214,11 +1216,16 @@ void main() {
           color: _kScrollbarColor.color,
         ),
       );
+    } else {
+      expect(pointer.location, const Offset(793.0, 15.0));
+      expect(scrollController.offset, previousOffset + 20.0);
+    }
+
 
     // Drag is still being held, move pointer to be hovering over another area
     // of the scrollable (not over the scrollbar) and execute another pointer scroll
     pointer.hover(tester.getCenter(find.byType(SingleChildScrollView)));
-    await tester.sendEventToBinding(pointer.scroll(const Offset(0.0, -70.0)));
+    await tester.sendEventToBinding(pointer.scroll(const Offset(0.0, -90.0)));
     await tester.pumpAndSettle();
     // Scrolling while holding the drag on the scrollbar changed the offset
     expect(pointer.location, const Offset(400.0, 300.0));

packages/flutter/test/material/scrollbar_test.dart

@@ -1634,6 +1634,8 @@ void main() {
     pointer.hover(const Offset(798.0, 15.0));
     await tester.sendEventToBinding(pointer.scroll(const Offset(0.0, 20.0)));
     await tester.pumpAndSettle();
+
+    if (!kIsWeb) {
       // Scrolling while holding the drag on the scrollbar and still hovered over
       // the scrollbar should not have changed the scroll offset.
       expect(pointer.location, const Offset(798.0, 15.0));
@@ -1656,11 +1658,15 @@ void main() {
             color: const Color(0x99000000),
           ),
       );
+    } else {
+      expect(pointer.location, const Offset(798.0, 15.0));
+      expect(scrollController.offset, previousOffset + 20.0);
+    }
 
     // Drag is still being held, move pointer to be hovering over another area
     // of the scrollable (not over the scrollbar) and execute another pointer scroll
     pointer.hover(tester.getCenter(find.byType(SingleChildScrollView)));
-    await tester.sendEventToBinding(pointer.scroll(const Offset(0.0, -70.0)));
+    await tester.sendEventToBinding(pointer.scroll(const Offset(0.0, -90.0)));
     await tester.pumpAndSettle();
     // Scrolling while holding the drag on the scrollbar changed the offset
     expect(pointer.location, const Offset(400.0, 300.0));

packages/flutter/test/widgets/scrollbar_test.dart

@@ -1607,6 +1607,8 @@ void main() {
     pointer.hover(const Offset(798.0, 15.0));
     await tester.sendEventToBinding(pointer.scroll(const Offset(0.0, 20.0)));
     await tester.pumpAndSettle();
+
+    if (!kIsWeb) {
       // Scrolling while holding the drag on the scrollbar and still hovered over
       // the scrollbar should not have changed the scroll offset.
       expect(pointer.location, const Offset(798.0, 15.0));
@@ -1629,11 +1631,15 @@ void main() {
             color: const Color(0x66bcbcbc),
           ),
       );
+    } else {
+      expect(pointer.location, const Offset(798.0, 15.0));
+      expect(scrollController.offset, previousOffset + 20.0);
+    }
 
     // Drag is still being held, move pointer to be hovering over another area
     // of the scrollable (not over the scrollbar) and execute another pointer scroll
     pointer.hover(tester.getCenter(find.byType(SingleChildScrollView)));
-    await tester.sendEventToBinding(pointer.scroll(const Offset(0.0, -70.0)));
+    await tester.sendEventToBinding(pointer.scroll(const Offset(0.0, -90.0)));
     await tester.pumpAndSettle();
     // Scrolling while holding the drag on the scrollbar changed the offset
     expect(pointer.location, const Offset(400.0, 300.0));
@@ -2788,4 +2794,50 @@ void main() {
         ),
     );
   });
+
+  testWidgets('The bar support mouse wheel event', (WidgetTester tester) async {
+    // Regression test for https://github.com/flutter/flutter/pull/109659
+    final ScrollController scrollController = ScrollController();
+    Widget buildFrame() {
+      return Directionality(
+        textDirection: TextDirection.ltr,
+        child: MediaQuery(
+          data: const MediaQueryData(),
+          child: PrimaryScrollController(
+            controller: scrollController,
+            child: RawScrollbar(
+              thumbVisibility: true,
+              controller: scrollController,
+              child: const SingleChildScrollView(
+                primary: true,
+                child: SizedBox(
+                  width: double.infinity,
+                  height: 1200.0,
+                ),
+              ),
+            ),
+          ),
+        ),
+      );
+    }
+
+    await tester.pumpWidget(buildFrame());
+    await tester.pumpAndSettle();
+    expect(scrollController.offset, 0.0);
+
+    // Execute a pointer scroll hover on the scroll bar
+    final TestPointer pointer = TestPointer(1, ui.PointerDeviceKind.mouse);
+    pointer.hover(const Offset(798.0, 15.0));
+    await tester.sendEventToBinding(pointer.scroll(const Offset(0.0, 30.0)));
+    await tester.pumpAndSettle();
+
+    expect(scrollController.offset, 30.0);
+
+    // Execute a pointer scroll outside the scroll bar
+    pointer.hover(const Offset(198.0, 15.0));
+    await tester.sendEventToBinding(pointer.scroll(const Offset(0.0, 70.0)));
+    await tester.pumpAndSettle();
+
+    expect(scrollController.offset, 100.0);
+  }, variant: TargetPlatformVariant.all());
 }