fix(macOS): add transform3D property to RCTUIView with anchor point and hit testing fixes

On macOS, AppKit resets layer.transform to identity during its display
cycle because NSView has no built-in transform property. This adds a
transform3D property to RCTUIView that persists the transform and
re-applies it in updateLayer.

Also fixes two related issues in the compat layer:
- Compensates for macOS layer.anchorPoint defaulting to {0,0} instead
  of {0.5, 0.5}, so transforms apply from the view's center.
- Uses CALayer coordinate conversion in hitTest: and
  RCTUIViewHitTestWithEvent, which correctly accounts for layer.transform
  (NSView's convertPoint:fromView: does not).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Saadnajmi

packages/react-native/React/RCTUIKit/RCTUIView.h

@@ -56,6 +56,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 @property (nonatomic, copy) NSColor *backgroundColor;
 @property (nonatomic) CGAffineTransform transform;
+@property (nonatomic) CATransform3D transform3D;
 
 /**
  * Specifies whether the view should receive the mouse down event when the
@@ -75,7 +76,6 @@ NS_ASSUME_NONNULL_BEGIN
  */
 @property (nonatomic, assign) BOOL enableFocusRing;
 
-// [macOS
 /**
  * iOS compatibility shim. On macOS, this forwards to accessibilityChildren.
  */
@@ -90,9 +90,9 @@ NS_ASSUME_NONNULL_BEGIN
 
 #if !TARGET_OS_OSX
 
-UIKIT_STATIC_INLINE RCTPlatformView *RCTUIViewHitTestWithEvent(RCTPlatformView *view, CGPoint point, __unused UIEvent *__nullable event)
+UIKIT_STATIC_INLINE RCTPlatformView *RCTUIViewHitTestWithEvent(RCTPlatformView *view, CGPoint point, RCTPlatformView *fromView, __unused UIEvent *__nullable event)
 {
-  return [view hitTest:point withEvent:event];
+  return [view hitTest:[view convertPoint:point fromView:fromView] withEvent:event];
 }
 
 UIKIT_STATIC_INLINE void RCTUIViewSetContentModeRedraw(UIView *view)
@@ -107,11 +107,15 @@ UIKIT_STATIC_INLINE BOOL RCTUIViewIsDescendantOfView(RCTPlatformView *view, RCTP
 
 #else // TARGET_OS_OSX
 
-NS_INLINE RCTPlatformView *RCTUIViewHitTestWithEvent(RCTPlatformView *view, CGPoint point, __unused UIEvent *__nullable event)
+// Use CALayer coordinate conversion which correctly accounts for layer.transform.
+// NSView's convertPoint:fromView: does not account for layer transforms on macOS.
+// IMPORTANT -- NSView's hitTest: expects a point in the superview's coordinate space,
+// so we convert from fromView → superview using CALayer, which handles layer transforms correctly.
+// This allows hit testing to work correctly between nested RCTUIViews and plain NSViews.
+NS_INLINE RCTPlatformView *RCTUIViewHitTestWithEvent(RCTPlatformView *view, CGPoint point, RCTPlatformView *fromView, __unused UIEvent *__nullable event)
 {
-  // [macOS IMPORTANT -- point is in local coordinate space, but OSX expects super coordinate space for hitTest:
   NSView *superview = [view superview];
-  NSPoint pointInSuperview = superview != nil ? [view convertPoint:point toView:superview] : point;
+  NSPoint pointInSuperview = superview != nil ? [superview.layer convertPoint:point fromLayer:fromView.layer] : point;
   return [view hitTest:pointInSuperview];
 }
 

packages/react-native/React/RCTUIKit/RCTUIView.m

@@ -9,6 +9,7 @@
 
 #if TARGET_OS_OSX
 
+#import <QuartzCore/QuartzCore.h>
 #import <React/RCTUIView.h>
 
 // UIView
@@ -21,6 +22,8 @@ @implementation RCTUIView
   BOOL _userInteractionEnabled;
   BOOL _mouseDownCanMoveWindow;
   BOOL _respondsToDisplayLayer;
+  CATransform3D _transform3D;
+  BOOL _hasCustomTransform3D;
 }
 
 + (NSSet<NSString *> *)keyPathsForValuesAffectingValueForKey:(NSString *)key
@@ -51,6 +54,8 @@ @implementation RCTUIView
     self->_enableFocusRing = YES;
     self->_mouseDownCanMoveWindow = YES;
     self->_respondsToDisplayLayer = [self respondsToSelector:@selector(displayLayer:)];
+    self->_transform3D = CATransform3DIdentity;
+    self->_hasCustomTransform3D = NO;
   }
   return self;
 }
@@ -127,20 +132,46 @@ - (CGAffineTransform)transform
 
 - (void)setTransform:(CGAffineTransform)transform
 {
-  self.layer.affineTransform = transform;
+  self.transform3D = CATransform3DMakeAffineTransform(transform);
+}
+
+- (CATransform3D)transform3D
+{
+  return _transform3D;
+}
+
+- (void)setTransform3D:(CATransform3D)transform3D
+{
+  // On macOS, layer.anchorPoint defaults to {0, 0} instead of {0.5, 0.5} on iOS.
+  // Compensate so transforms are applied from the view's center as expected.
+  CGPoint anchorPoint = self.layer.anchorPoint;
+  if (CGPointEqualToPoint(anchorPoint, CGPointZero) && !CATransform3DEqualToTransform(transform3D, CATransform3DIdentity)) {
+    CATransform3D originAdjust = CATransform3DTranslate(CATransform3DIdentity, self.frame.size.width / 2, self.frame.size.height / 2, 0);
+    transform3D = CATransform3DConcat(CATransform3DConcat(CATransform3DInvert(originAdjust), transform3D), originAdjust);
+  }
+
+  _transform3D = transform3D;
+  _hasCustomTransform3D = !CATransform3DEqualToTransform(transform3D, CATransform3DIdentity);
+  self.layer.transform = transform3D;
 }
 
 - (NSView *)hitTest:(NSPoint)point
 {
-  // IMPORTANT point is passed in super coordinates by OSX, but expected to be passed in local coordinates
-  NSView *superview = [self superview];
-  NSPoint pointInSelf = superview != nil ? [self convertPoint:point fromView:superview] : point;
-  return [self hitTest:pointInSelf withEvent:nil];
+  // NSView's hitTest: receives a point in superview coordinates. Convert to local
+  // coordinates using CALayer, which correctly accounts for layer.transform.
+  // NSView's convertPoint:fromView: does NOT account for layer transforms.
+  CGPoint localPoint;
+  if (self.layer.superlayer) {
+    localPoint = [self.layer convertPoint:point fromLayer:self.layer.superlayer];
+  } else {
+    localPoint = point;
+  }
+  return [self hitTest:localPoint withEvent:nil];
 }
 
 - (BOOL)wantsUpdateLayer
 {
-  return [self respondsToSelector:@selector(displayLayer:)];
+  return _respondsToDisplayLayer || _hasCustomTransform3D;
 }
 
 - (void)updateLayer
@@ -153,8 +184,13 @@ - (void)updateLayer
     [layer setBackgroundColor:[_backgroundColor CGColor]];
   }
 
-  // In Fabric, wantsUpdateLayer is always enabled and doesn't guarantee that
-  // the instance has a displayLayer method.
+  // On macOS, AppKit's layer-backed view system resets layer.transform to identity
+  // during its layout/display cycle because NSView has no built-in transform property
+  // (unlike UIView on iOS). We must re-apply the stored transform after each cycle.
+  if (_hasCustomTransform3D && !CATransform3DEqualToTransform(layer.transform, _transform3D)) {
+    layer.transform = _transform3D;
+  }
+
   if (_respondsToDisplayLayer) {
     [(id<CALayerDelegate>)self displayLayer:layer];
   }