Cherrypick Scrollview parity and revert Scrollview regression PRs for stable 0.80

change/react-native-windows-8a4ff7bf-ac06-4eb1-9a58-378dc5d976fa.json

@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Implement onMomentumScrollEnd and onMomentumScrollBegin for Fabric ScrollView",
+  "packageName": "react-native-windows",
+  "email": "[email protected]",
+  "dependentChangeType": "patch"
+}

packages/playground/Samples/scrollViewSnapSample.tsx

@@ -288,6 +288,12 @@ export default class Bootstrap extends React.Component<{}, any> {
             onScrollEndDrag={() => {
               console.log('onScrollEndDrag');
             }}
+            onMomentumScrollBegin={() => {
+              console.log('onMomentumScrollBegin');
+            }}
+            onMomentumScrollEnd={() => {
+              console.log('onMomentumScrollEnd');
+            }}
             onScroll={() => {
               console.log('onScroll');
             }}

vnext/Microsoft.ReactNative/CompositionSwitcher.idl

@@ -31,13 +31,6 @@ namespace Microsoft.ReactNative.Composition.Experimental
     SwitchThumb,
   };
 
-  enum SnapAlignment
-  {
-    Start,
-    Center,
-    End,
-  };
-
   [webhosthidden]
   [uuid("172def51-9e1a-4e3c-841a-e5a470065acc")] // uuid needed for empty interfaces
   [version(0)]
@@ -118,6 +111,8 @@ namespace Microsoft.ReactNative.Composition.Experimental
     event Windows.Foundation.EventHandler<IScrollPositionChangedArgs> ScrollPositionChanged;
     event Windows.Foundation.EventHandler<IScrollPositionChangedArgs> ScrollBeginDrag;
 	  event Windows.Foundation.EventHandler<IScrollPositionChangedArgs> ScrollEndDrag;
+    event Windows.Foundation.EventHandler<IScrollPositionChangedArgs> ScrollMomentumBegin;
+    event Windows.Foundation.EventHandler<IScrollPositionChangedArgs> ScrollMomentumEnd;
     void ContentSize(Windows.Foundation.Numerics.Vector2 size);
     Windows.Foundation.Numerics.Vector3 ScrollPosition { get; };
     void ScrollBy(Windows.Foundation.Numerics.Vector3 offset, Boolean animate);
@@ -127,7 +122,7 @@ namespace Microsoft.ReactNative.Composition.Experimental
     void SetMaximumZoomScale(Single maximumZoomScale);
     void SetMinimumZoomScale(Single minimumZoomScale);
     Boolean Horizontal;
-    void SetSnapPoints(Boolean snapToStart, Boolean snapToEnd, Windows.Foundation.Collections.IVectorView<Single> offsets, SnapAlignment snapToAlignment);
+    void SetSnapPoints(Boolean snapToStart, Boolean snapToEnd, Windows.Foundation.Collections.IVectorView<Single> offsets);
   }
 
   [webhosthidden]

vnext/Microsoft.ReactNative/Fabric/Composition/CompositionContextHelper.cpp

@@ -27,8 +27,6 @@
 
 namespace Microsoft::ReactNative::Composition::Experimental {
 
-using namespace winrt::Microsoft::ReactNative::Composition::Experimental;
-
 template <typename TSpriteVisual>
 struct CompositionTypeTraits {};
 
@@ -711,24 +709,50 @@ struct CompScrollerVisual : winrt::implements<
     void IdleStateEntered(
         typename TTypeRedirects::InteractionTracker sender,
         typename TTypeRedirects::InteractionTrackerIdleStateEnteredArgs args) noexcept {
+      // If we were in inertia and are now idle, momentum has ended
+      if (m_outer->m_inertia) {
+        m_outer->FireScrollMomentumEnd({sender.Position().x, sender.Position().y});
+      }
+
+      // If we were interacting but never entered inertia (Interacting -> Idle),
+      // and the interaction was user-driven (requestId == 0), fire end-drag here.
+      // Note: if the interactionRequestId was non-zero it was caused by a Try* call
+      // (programmatic), so we should not fire onScrollEndDrag.
+      if (m_outer->m_interacting && args.RequestId() == 0) {
+        m_outer->FireScrollEndDrag({sender.Position().x, sender.Position().y});
+      }
+
+      // Clear state flags
       m_outer->m_custom = false;
       m_outer->m_inertia = false;
+      m_outer->m_interacting = false;
     }
     void InertiaStateEntered(
         typename TTypeRedirects::InteractionTracker sender,
         typename TTypeRedirects::InteractionTrackerInertiaStateEnteredArgs args) noexcept {
       m_outer->m_custom = false;
       m_outer->m_inertia = true;
       m_outer->m_currentPosition = args.NaturalRestingPosition();
-      // When the user stops interacting with the object, tracker can go into two paths:
-      // 1. tracker goes into idle state immediately
-      // 2. tracker has just started gliding into Inertia state
-      // Fire ScrollEndDrag
-      m_outer->FireScrollEndDrag({args.NaturalRestingPosition().x, args.NaturalRestingPosition().y});
+
+      if (!m_outer->m_interacting && args.RequestId() == 0) {
+        m_outer->FireScrollBeginDrag({args.NaturalRestingPosition().x, args.NaturalRestingPosition().y});
+      }
+
+      // If interaction was user-driven (requestId == 0),
+      // fire ScrollEndDrag here (Interacting -> Inertia caused by user lift).
+      if (m_outer->m_interacting && args.RequestId() == 0) {
+        m_outer->FireScrollEndDrag({args.NaturalRestingPosition().x, args.NaturalRestingPosition().y});
+      }
+
+      // Fire momentum scroll begin when we enter inertia (user or programmatic)
+      m_outer->FireScrollMomentumBegin({args.NaturalRestingPosition().x, args.NaturalRestingPosition().y});
     }
     void InteractingStateEntered(
         typename TTypeRedirects::InteractionTracker sender,
         typename TTypeRedirects::InteractionTrackerInteractingStateEnteredArgs args) noexcept {
+      // Mark that we're now interacting and remember the requestId (user manipulations => 0)
+      m_outer->m_interacting = true;
+
       // Fire when the user starts dragging the object
       m_outer->FireScrollBeginDrag({sender.Position().x, sender.Position().y});
     }
@@ -738,6 +762,10 @@ struct CompScrollerVisual : winrt::implements<
     void ValuesChanged(
         typename TTypeRedirects::InteractionTracker sender,
         typename TTypeRedirects::InteractionTrackerValuesChangedArgs args) noexcept {
+      if (!m_outer->m_interacting && args.RequestId() == 0) {
+        m_outer->FireScrollBeginDrag({args.Position().x, args.Position().y});
+      }
+      m_outer->m_interacting = true;
       m_outer->m_currentPosition = args.Position();
       m_outer->FireScrollPositionChanged({args.Position().x, args.Position().y});
     }
@@ -873,11 +901,9 @@ struct CompScrollerVisual : winrt::implements<
   void SetSnapPoints(
       bool snapToStart,
       bool snapToEnd,
-      winrt::Windows::Foundation::Collections::IVectorView<float> const &offsets,
-      SnapAlignment snapToAlignment) noexcept {
+      winrt::Windows::Foundation::Collections::IVectorView<float> const &offsets) noexcept {
     m_snapToStart = snapToStart;
     m_snapToEnd = snapToEnd;
-    m_snapToAlignment = snapToAlignment;
     m_snapToOffsets.clear();
     if (offsets) {
       for (auto const &offset : offsets) {
@@ -985,6 +1011,20 @@ struct CompScrollerVisual : winrt::implements<
     return m_scrollEndDragEvent.add(handler);
   }
 
+  winrt::event_token ScrollMomentumBegin(
+      winrt::Windows::Foundation::EventHandler<
+          winrt::Microsoft::ReactNative::Composition::Experimental::IScrollPositionChangedArgs> const
+          &handler) noexcept {
+    return m_scrollMomentumBeginEvent.add(handler);
+  }
+
+  winrt::event_token ScrollMomentumEnd(
+      winrt::Windows::Foundation::EventHandler<
+          winrt::Microsoft::ReactNative::Composition::Experimental::IScrollPositionChangedArgs> const
+          &handler) noexcept {
+    return m_scrollMomentumEndEvent.add(handler);
+  }
+
   void ScrollPositionChanged(winrt::event_token const &token) noexcept {
     m_scrollPositionChangedEvent.remove(token);
   }
@@ -997,6 +1037,14 @@ struct CompScrollerVisual : winrt::implements<
     m_scrollEndDragEvent.remove(token);
   }
 
+  void ScrollMomentumBegin(winrt::event_token const &token) noexcept {
+    m_scrollMomentumBeginEvent.remove(token);
+  }
+
+  void ScrollMomentumEnd(winrt::event_token const &token) noexcept {
+    m_scrollMomentumEndEvent.remove(token);
+  }
+
   void ContentSize(winrt::Windows::Foundation::Numerics::float2 const &size) noexcept {
     m_contentSize = size;
     m_contentVisual.Size(size);
@@ -1075,6 +1123,14 @@ struct CompScrollerVisual : winrt::implements<
     m_scrollEndDragEvent(*this, winrt::make<CompScrollPositionChangedArgs>(position));
   }
 
+  void FireScrollMomentumBegin(winrt::Windows::Foundation::Numerics::float2 position) noexcept {
+    m_scrollMomentumBeginEvent(*this, winrt::make<CompScrollPositionChangedArgs>(position));
+  }
+
+  void FireScrollMomentumEnd(winrt::Windows::Foundation::Numerics::float2 position) noexcept {
+    m_scrollMomentumEndEvent(*this, winrt::make<CompScrollPositionChangedArgs>(position));
+  }
+
   void UpdateMaxPosition() noexcept {
     m_interactionTracker.MaxPosition(
         {std::max<float>(m_contentSize.x - m_visualSize.x, 0),
@@ -1104,22 +1160,6 @@ struct CompScrollerVisual : winrt::implements<
     }
 
     snapPositions.insert(snapPositions.end(), m_snapToOffsets.begin(), m_snapToOffsets.end());
-
-    // Adjust snap positions based on alignment
-    const float viewportSize = m_horizontal ? visualSize.x : visualSize.y;
-    if (m_snapToAlignment == SnapAlignment::Center) {
-      // For center alignment, offset snap positions by half the viewport size
-      for (auto &position : snapPositions) {
-        position = std::max(0.0f, position - viewportSize / 2.0f);
-      }
-    } else if (m_snapToAlignment == SnapAlignment::End) {
-      // For end alignment, offset snap positions by the full viewport size
-      for (auto &position : snapPositions) {
-        position = std::max(0.0f, position - viewportSize);
-      }
-    }
-    // For Start alignment, no adjustment needed
-
     std::sort(snapPositions.begin(), snapPositions.end());
     snapPositions.erase(std::unique(snapPositions.begin(), snapPositions.end()), snapPositions.end());
 
@@ -1247,9 +1287,9 @@ struct CompScrollerVisual : winrt::implements<
   bool m_snapToStart{true};
   bool m_snapToEnd{true};
   std::vector<float> m_snapToOffsets;
-  SnapAlignment m_snapToAlignment{SnapAlignment::Start};
   bool m_inertia{false};
   bool m_custom{false};
+  bool m_interacting{false};
   winrt::Windows::Foundation::Numerics::float3 m_targetPosition;
   winrt::Windows::Foundation::Numerics::float3 m_currentPosition;
   winrt::Windows::Foundation::Numerics::float2 m_contentSize{0};
@@ -1263,6 +1303,12 @@ struct CompScrollerVisual : winrt::implements<
   winrt::event<winrt::Windows::Foundation::EventHandler<
       winrt::Microsoft::ReactNative::Composition::Experimental::IScrollPositionChangedArgs>>
       m_scrollEndDragEvent;
+  winrt::event<winrt::Windows::Foundation::EventHandler<
+      winrt::Microsoft::ReactNative::Composition::Experimental::IScrollPositionChangedArgs>>
+      m_scrollMomentumBeginEvent;
+  winrt::event<winrt::Windows::Foundation::EventHandler<
+      winrt::Microsoft::ReactNative::Composition::Experimental::IScrollPositionChangedArgs>>
+      m_scrollMomentumEndEvent;
   typename TTypeRedirects::SpriteVisual m_visual{nullptr};
   typename TTypeRedirects::SpriteVisual m_contentVisual{nullptr};
   typename TTypeRedirects::InteractionTracker m_interactionTracker{nullptr};

vnext/Microsoft.ReactNative/Fabric/Composition/ScrollViewComponentView.cpp

@@ -27,7 +27,6 @@
 namespace winrt::Microsoft::ReactNative::Composition::implementation {
 
 constexpr float c_scrollerLineDelta = 16.0f;
-constexpr auto c_maxSnapPoints = 1000;
 
 enum class ScrollbarHitRegion : int {
   Unknown = -1,
@@ -741,15 +740,6 @@ void ScrollViewComponentView::updateBackgroundColor(const facebook::react::Share
   }
 }
 
-winrt::Windows::Foundation::Collections::IVector<float> ScrollViewComponentView::CreateSnapToOffsets(
-    const std::vector<float> &offsets) {
-  auto snapToOffsets = winrt::single_threaded_vector<float>();
-  for (const auto &offset : offsets) {
-    snapToOffsets.Append(offset);
-  }
-  return snapToOffsets;
-}
-
 void ScrollViewComponentView::updateProps(
     facebook::react::Props::Shared const &props,
     facebook::react::Props::Shared const &oldProps) noexcept {
@@ -818,13 +808,11 @@ void ScrollViewComponentView::updateProps(
 
   if (oldViewProps.snapToStart != newViewProps.snapToStart || oldViewProps.snapToEnd != newViewProps.snapToEnd ||
       oldViewProps.snapToOffsets != newViewProps.snapToOffsets) {
-    if (oldViewProps.snapToInterval != newViewProps.snapToInterval) {
-      updateSnapPoints();
-    } else {
-      const auto snapToOffsets = CreateSnapToOffsets(newViewProps.snapToOffsets);
-      m_scrollVisual.SetSnapPoints(
-          newViewProps.snapToStart, newViewProps.snapToEnd, snapToOffsets.GetView(), SnapAlignment::Center);
+    const auto snapToOffsets = winrt::single_threaded_vector<float>();
+    for (const auto &offset : newViewProps.snapToOffsets) {
+      snapToOffsets.Append(static_cast<float>(offset));
     }
+    m_scrollVisual.SetSnapPoints(newViewProps.snapToStart, newViewProps.snapToEnd, snapToOffsets.GetView());
   }
 }
 
@@ -875,9 +863,6 @@ void ScrollViewComponentView::updateContentVisualSize() noexcept {
   m_verticalScrollbarComponent->ContentSize(contentSize);
   m_horizontalScrollbarComponent->ContentSize(contentSize);
   m_scrollVisual.ContentSize(contentSize);
-
-  // Update snap points if snapToInterval is being used, as content size affects the number of snap points
-  updateSnapPoints();
 }
 
 void ScrollViewComponentView::prepareForRecycle() noexcept {}
@@ -1354,6 +1339,32 @@ winrt::Microsoft::ReactNative::Composition::Experimental::IVisual ScrollViewComp
         }
       });
 
+  m_scrollMomentumBeginRevoker = m_scrollVisual.ScrollMomentumBegin(
+      winrt::auto_revoke,
+      [this](
+          winrt::IInspectable const & /*sender*/,
+          winrt::Microsoft::ReactNative::Composition::Experimental::IScrollPositionChangedArgs const &args) {
+        auto eventEmitter = GetEventEmitter();
+        if (eventEmitter) {
+          auto scrollMetrics = getScrollMetrics(eventEmitter, args);
+          std::static_pointer_cast<facebook::react::ScrollViewEventEmitter const>(eventEmitter)
+              ->onMomentumScrollBegin(scrollMetrics);
+        }
+      });
+
+  m_scrollMomentumEndRevoker = m_scrollVisual.ScrollMomentumEnd(
+      winrt::auto_revoke,
+      [this](
+          winrt::IInspectable const & /*sender*/,
+          winrt::Microsoft::ReactNative::Composition::Experimental::IScrollPositionChangedArgs const &args) {
+        auto eventEmitter = GetEventEmitter();
+        if (eventEmitter) {
+          auto scrollMetrics = getScrollMetrics(eventEmitter, args);
+          std::static_pointer_cast<facebook::react::ScrollViewEventEmitter const>(eventEmitter)
+              ->onMomentumScrollEnd(scrollMetrics);
+        }
+      });
+
   return visual;
 }
 
@@ -1450,50 +1461,4 @@ void ScrollViewComponentView::updateShowsVerticalScrollIndicator(bool value) noe
 void ScrollViewComponentView::updateDecelerationRate(float value) noexcept {
   m_scrollVisual.SetDecelerationRate({value, value, value});
 }
-
-SnapAlignment ScrollViewComponentView::convertSnapToAlignment(
-    facebook::react::ScrollViewSnapToAlignment alignment) noexcept {
-  switch (alignment) {
-    case facebook::react::ScrollViewSnapToAlignment::Center:
-      return SnapAlignment::Center;
-    case facebook::react::ScrollViewSnapToAlignment::End:
-      return SnapAlignment::End;
-    case facebook::react::ScrollViewSnapToAlignment::Start:
-    default:
-      return SnapAlignment::Start;
-  }
-}
-
-void ScrollViewComponentView::updateSnapPoints() noexcept {
-  const auto &viewProps = *std::static_pointer_cast<const facebook::react::ScrollViewProps>(this->viewProps());
-  const auto snapToOffsets = CreateSnapToOffsets(viewProps.snapToOffsets);
-  // Typically used in combination with snapToAlignment and decelerationRate="fast"
-  auto snapAlignment = SnapAlignment::Center;
-  auto decelerationRate = viewProps.decelerationRate;
-
-  // snapToOffsets has priority over snapToInterval (matches React Native behavior)
-  if (viewProps.snapToInterval > 0 && decelerationRate >= 0.99) {
-    snapAlignment = convertSnapToAlignment(viewProps.snapToAlignment);
-    // Generate snap points based on interval
-    // Calculate the content size to determine how many intervals to create
-    float contentLength = viewProps.horizontal
-        ? std::max(m_contentSize.width, m_layoutMetrics.frame.size.width) * m_layoutMetrics.pointScaleFactor
-        : std::max(m_contentSize.height, m_layoutMetrics.frame.size.height) * m_layoutMetrics.pointScaleFactor;
-
-    float interval = static_cast<float>(viewProps.snapToInterval) * m_layoutMetrics.pointScaleFactor;
-
-    // Ensure we have a reasonable minimum interval to avoid infinite loops or excessive memory usage
-    if (interval >= 1.0f && contentLength > 0) {
-      // Generate offsets at each interval, but limit the number of snap points to avoid excessive memory usage
-      int snapPointCount = 0;
-
-      for (float offset = 0; offset <= contentLength && snapPointCount < c_maxSnapPoints; offset += interval) {
-        snapToOffsets.Append(offset);
-        snapPointCount++;
-      }
-    }
-  }
-
-  m_scrollVisual.SetSnapPoints(viewProps.snapToStart, viewProps.snapToEnd, snapToOffsets.GetView(), snapAlignment);
-}
 } // namespace winrt::Microsoft::ReactNative::Composition::implementation