[fabric] Add mouse enter/leave tracking on scroll

Summary:
This diff adds a bounds change observer to the wrapping clip view, allowing to be notified when the view position is changing because a parent scroll view is being scrolled.

This allows the view to evaluate the new cursor position and check if mouse enter/leave events have to be emitted.

Test Plan:
* Run Zeratul with Fabric enabled.
* Scroll the messages view without moving the cursor position and check that enter/leave tracking is working as expected.

 https://pxl.cl/4jSxh

Reviewers: shawndempsey, #rn-desktop

Reviewed By: shawndempsey

Differential Revision: https://phabricator.intern.facebook.com/D53529018

Tasks: T154617556

Author: Nick Lefever

packages/react-native/React/Fabric/Mounting/ComponentViews/View/RCTViewComponentView.mm

@@ -50,6 +50,7 @@ @implementation RCTViewComponentView {
   BOOL _isJSResponder;
   BOOL _removeClippedSubviews;
   BOOL _hasMouseOver; // [macOS]
+  BOOL _hasClipViewBoundsObserver; // [macOS]
   NSTrackingArea *_trackingArea; // [macOS]
   NSMutableArray<RCTUIView *> *_reactSubviews; // [macOS]
   NSSet<NSString *> *_Nullable _propKeysManagedByAnimated_DO_NOT_USE_THIS_IS_BROKEN;
@@ -649,6 +650,7 @@ - (void)finalizeUpdates:(RNComponentViewUpdateMask)updateMask
   [self invalidateLayer];
 
   [self updateTrackingAreas];
+  [self updateClipViewBoundsObserverIfNeeded];
 }
 
 - (void)prepareForRecycle
@@ -1720,6 +1722,38 @@ - (void)updateMouseOverIfNeeded
   }
 }
 
+- (void)updateClipViewBoundsObserverIfNeeded
+{
+  // Subscribe to view bounds changed notification so that the view can be notified when a
+  // scroll event occurs either due to trackpad/gesture based scrolling or a scrollwheel event
+  // both of which would not cause the mouseExited to be invoked.
+
+  NSClipView *clipView = self.window ? self.enclosingScrollView.contentView : nil;
+  
+  BOOL hasMouseEventHandler = _props->macOSViewEvents[facebook::react::MacOSViewEvents::Offset::MouseEnter] ||
+    _props->macOSViewEvents[facebook::react::MacOSViewEvents::Offset::MouseLeave];
+
+  if (_hasClipViewBoundsObserver && (!clipView || !hasMouseEventHandler)) {
+    _hasClipViewBoundsObserver = NO;
+    [[NSNotificationCenter defaultCenter] removeObserver:self
+                                                    name:NSViewBoundsDidChangeNotification
+                                                  object:nil];
+  } else if (!_hasClipViewBoundsObserver && clipView && hasMouseEventHandler) {
+    _hasClipViewBoundsObserver = YES;
+    [[NSNotificationCenter defaultCenter] addObserver:self
+                                             selector:@selector(updateMouseOverIfNeeded)
+                                                 name:NSViewBoundsDidChangeNotification
+                                               object:clipView];
+    [self updateMouseOverIfNeeded];
+  }
+}
+
+- (void)viewDidMoveToWindow
+{
+  [self updateClipViewBoundsObserverIfNeeded];
+  [super viewDidMoveToWindow];
+}
+
 - (void)updateTrackingAreas
 {
   if (_trackingArea) {