From 5a7a39ec6d0c8bceceba8210cf4ca91c19f2523b Mon Sep 17 00:00:00 2001
From: Adam Gleitman <adgleitm@microsoft.com>
Date: Wed, 26 Jun 2024 14:48:25 -0700
Subject: [PATCH] Use *shadow* view traversal for handling nested mouse events

---
 .../Libraries/Text/Text/RCTTextView.mm        | 16 +++++++++++++---
 .../react-native/React/Views/RCTShadowView.h  |  7 +++++++
 .../react-native/React/Views/RCTShadowView.m  | 19 +++++++++++++++++++
 3 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/packages/react-native/Libraries/Text/Text/RCTTextView.mm b/packages/react-native/Libraries/Text/Text/RCTTextView.mm
index 3f20a4cf5a994d..5c78e25db8d960 100644
--- a/packages/react-native/Libraries/Text/Text/RCTTextView.mm
+++ b/packages/react-native/Libraries/Text/Text/RCTTextView.mm
@@ -12,6 +12,7 @@
 #endif // [macOS]
 
 #import <React/RCTAssert.h> // [macOS]
+#import <React/RCTUIManager.h> // [macOS]
 #import <React/RCTUtils.h>
 #import <React/UIView+React.h>
 #import <React/RCTFocusChangeEvent.h> // [macOS]
@@ -506,13 +507,20 @@ - (void)updateHoveredSubviewWithEvent:(NSEvent *)event
 
   // self will always be an ancestor of any views we pass in here, so it serves as a good default option.
   // Also, if we do set from/to nil, we have to call the relevant events on the entire subtree.
-  RCTPlatformView *commonAncestor = [(_currentHoveredSubview ?: self) ancestorSharedWithView:(hoveredView ?: self)] ?: self;
+  RCTUIManager *uiManager = [[_eventDispatcher bridge] uiManager];
+  RCTShadowView *oldShadowView = [uiManager shadowViewForReactTag:[(_currentHoveredSubview ?: self) reactTag]];
+  RCTShadowView *newShadowView = [uiManager shadowViewForReactTag:[(hoveredView ?: self) reactTag]];
 
-  for (RCTPlatformView *exitedView = _currentHoveredSubview; exitedView != commonAncestor && exitedView != nil; exitedView = [exitedView superview]) {
+  // Find the common ancestor between the two shadow views
+  RCTShadowView *commonAncestor = [oldShadowView ancestorSharedWithShadowView:newShadowView];
+
+  for (RCTShadowView *exitedShadowView = oldShadowView; exitedShadowView != commonAncestor && exitedShadowView != nil; exitedShadowView = [exitedShadowView reactSuperview]) {
+    RCTPlatformView *exitedView = [uiManager viewForReactTag:[exitedShadowView reactTag]];
     if (![exitedView isKindOfClass:[RCTUIView class]]) {
       RCTLogError(@"Unexpected view of type %@ found in hierarchy, must be RCTUIView or subclass", [exitedView class]);
       continue;
     }
+
     RCTUIView *exitedReactView = (RCTUIView *)exitedView;
     [self sendMouseEventWithBlock:[exitedReactView onMouseLeave]
                      locationInfo:[self locationInfoFromEvent:event]
@@ -522,11 +530,13 @@ - (void)updateHoveredSubviewWithEvent:(NSEvent *)event
 
   // We cache these so we can call them from outermost to innermost
   NSMutableArray<RCTUIView *> *enteredViewHierarchy = [NSMutableArray new];
-  for (RCTPlatformView *enteredView = hoveredView; enteredView != commonAncestor && enteredView != nil; enteredView = [enteredView superview]) {
+  for (RCTShadowView *enteredShadowView = newShadowView; enteredShadowView != commonAncestor && enteredShadowView != nil; enteredShadowView = [enteredShadowView reactSuperview]) {
+    RCTPlatformView *enteredView = [uiManager viewForReactTag:[enteredShadowView reactTag]];
     if (![enteredView isKindOfClass:[RCTUIView class]]) {
       RCTLogError(@"Unexpected view of type %@ found in hierarchy, must be RCTUIView or subclass", [enteredView class]);
       continue;
     }
+
     [enteredViewHierarchy addObject:(RCTUIView *)enteredView];
   }
   for (NSInteger i = [enteredViewHierarchy count] - 1; i >= 0; i--) {
diff --git a/packages/react-native/React/Views/RCTShadowView.h b/packages/react-native/React/Views/RCTShadowView.h
index 8c7567076bb309..e02c71bef76c0c 100644
--- a/packages/react-native/React/Views/RCTShadowView.h
+++ b/packages/react-native/React/Views/RCTShadowView.h
@@ -241,6 +241,13 @@ typedef void (^RCTApplierBlock)(NSDictionary<NSNumber *, RCTPlatformView *> *vie
  */
 - (CGRect)measureLayoutRelativeToAncestor:(RCTShadowView *)ancestor;
 
+// [macOS
+/**
+ * Returns the closest ancestor shared by this shadow view and another specified shadow view.
+ */
+- (RCTShadowView *)ancestorSharedWithShadowView:(RCTShadowView *)shadowView;
+// macOS]
+
 /**
  * Checks if the current shadow view is a descendant of the provided `ancestor`
  */
diff --git a/packages/react-native/React/Views/RCTShadowView.m b/packages/react-native/React/Views/RCTShadowView.m
index 802d6b6da8d149..c54940a2212866 100644
--- a/packages/react-native/React/Views/RCTShadowView.m
+++ b/packages/react-native/React/Views/RCTShadowView.m
@@ -182,6 +182,25 @@ - (CGRect)measureLayoutRelativeToAncestor:(RCTShadowView *)ancestor
   return (CGRect){offset, self.layoutMetrics.frame.size};
 }
 
+// [macOS
+- (RCTShadowView *)ancestorSharedWithShadowView:(RCTShadowView *)shadowView
+{
+  // TODO: This can be optimized by climbing up both hierarchies at the same time
+  NSMutableSet<RCTShadowView *> *selfSuperviews = [NSMutableSet set];
+  for (RCTShadowView *view = self; view != nil; view = [view reactSuperview]) {
+    [selfSuperviews addObject:view];
+  }
+
+  for (RCTShadowView *candidateView = shadowView; candidateView != nil; candidateView = [candidateView reactSuperview]) {
+    if ([selfSuperviews containsObject:candidateView]) {
+      return candidateView;
+    }
+  }
+
+  return nil;
+}
+// macOS]
+
 - (BOOL)viewIsDescendantOf:(RCTShadowView *)ancestor
 {
   RCTShadowView *shadowView = self;