[macOS] Force clipping to path when platform view clip rect is rotated

shell/platform/darwin/macos/framework/Source/FlutterMutatorView.mm

@@ -92,6 +92,14 @@ CATransform3D ToCATransform3D(const FlutterTransformation& t) {
   return transform;
 }
 
+bool AffineTransformIsOnlyScaleOrTranslate(const CGAffineTransform& transform) {
+  return transform.b == 0 && transform.c == 0;
+}
+
+bool IsZeroSize(const FlutterSize size) {
+  return size.width == 0 && size.height == 0;
+}
+
 CGRect FromFlutterRect(const FlutterRect& rect) {
   return CGRectMake(rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top);
 }
@@ -182,6 +190,13 @@ bool RoundRectCornerIntersects(const FlutterRoundedRect& roundRect, const Flutte
 }
 
 CGPathRef PathFromRoundedRect(const FlutterRoundedRect& roundedRect) {
+  if (IsZeroSize(roundedRect.lower_left_corner_radius) &&
+      IsZeroSize(roundedRect.lower_right_corner_radius) &&
+      IsZeroSize(roundedRect.upper_left_corner_radius) &&
+      IsZeroSize(roundedRect.upper_right_corner_radius)) {
+    return CGPathCreateWithRect(FromFlutterRect(roundedRect.rect), nullptr);
+  }
+
   CGMutablePathRef path = CGPathCreateMutable();
 
   const auto& rect = roundedRect.rect;
@@ -306,7 +321,7 @@ CGRect MasterClipFromMutations(CGRect bounds, const MutationVector& mutations) {
 } ClipRoundedRect;
 
 /// Returns the set of all rounded rect paths generated by clips in the mutations vector.
-NSMutableArray* RoundedRectClipsFromMutations(CGRect master_clip, const MutationVector& mutations) {
+NSMutableArray* ClipPathFromMutations(CGRect master_clip, const MutationVector& mutations) {
   std::vector<ClipRoundedRect> rounded_rects;
 
   CATransform3D transform = CATransform3DIdentity;
@@ -320,22 +335,36 @@ CGRect MasterClipFromMutations(CGRect bounds, const MutationVector& mutations) {
       case kFlutterPlatformViewMutationTypeTransformation:
         transform = CATransform3DConcat(ToCATransform3D(mutation.transformation), transform);
         break;
-      case kFlutterPlatformViewMutationTypeClipRect:
+      case kFlutterPlatformViewMutationTypeClipRect: {
+        CGAffineTransform affineTransform = CATransform3DGetAffineTransform(transform);
+        // Shearing or rotation requires path clipping.
+        if (!AffineTransformIsOnlyScaleOrTranslate(affineTransform)) {
+          rounded_rects.push_back(
+              {FlutterRoundedRect{mutation.clip_rect, FlutterSize{0, 0}, FlutterSize{0, 0},
+                                  FlutterSize{0, 0}, FlutterSize{0, 0}},
+               affineTransform});
+        }
+        break;
+      }
       case kFlutterPlatformViewMutationTypeOpacity:
         break;
     }
   }
 
   NSMutableArray* paths = [NSMutableArray array];
   for (const auto& r : rounded_rects) {
-    CGAffineTransform inverse = CGAffineTransformInvert(r.transform);
-    // Transform master clip to clip rect coordinates and check if this view intersects one of the
-    // corners, which means we need to use path clipping.
-    CGRect localMasterClip = CGRectApplyAffineTransform(master_clip, inverse);
+    bool requiresPath = !AffineTransformIsOnlyScaleOrTranslate(r.transform);
+    if (!requiresPath) {
+      CGAffineTransform inverse = CGAffineTransformInvert(r.transform);
+      // Transform master clip to clip rect coordinates and check if this view intersects one of the
+      // corners, which means we need to use path clipping.
+      CGRect localMasterClip = CGRectApplyAffineTransform(master_clip, inverse);
+      requiresPath = RoundRectCornerIntersects(r.rrect, ToFlutterRect(localMasterClip));
+    }
 
     // Only clip to rounded rectangle path if the view intersects some of the round corners. If
     // not, clipping to masterClip is enough.
-    if (RoundRectCornerIntersects(r.rrect, ToFlutterRect(localMasterClip))) {
+    if (requiresPath) {
       CGPathRef path = PathFromRoundedRect(r.rrect);
       CGPathRef transformedPath = CGPathCreateCopyByTransformingPath(path, &r.transform);
       [paths addObject:(__bridge id)transformedPath];
@@ -481,7 +510,7 @@ - (void)applyFlutterLayer:(const FlutterLayer*)layer {
   self.hidden = NO;
 
   /// Paths in global logical coordinates that need to be clipped to.
-  NSMutableArray* paths = RoundedRectClipsFromMutations(masterClip, mutations);
+  NSMutableArray* paths = ClipPathFromMutations(masterClip, mutations);
   [self updatePathClipViewsWithPaths:paths];
 
   /// Update PlatformViewContainer, PlatformView, and apply transforms and axis-aligned clip rect.

shell/platform/darwin/macos/framework/Source/FlutterMutatorViewTest.mm

@@ -13,6 +13,8 @@ @interface FlutterMutatorView (Private)
 
 @end
 
+static constexpr float kMaxErr = 1e-10;
+
 namespace {
 void ApplyFlutterLayer(FlutterMutatorView* view,
                        FlutterSize size,
@@ -45,8 +47,6 @@ void ApplyFlutterLayer(FlutterMutatorView* view,
 // In order to avoid architecture-specific floating point differences we don't check for exact
 // equality using, for example, CATransform3DEqualToTransform.
 void ExpectTransform3DEqual(const CATransform3D& t, const CATransform3D& u) {
-  constexpr float kMaxErr = 1e-10;
-
   EXPECT_NEAR(t.m11, u.m11, kMaxErr);
   EXPECT_NEAR(t.m12, u.m12, kMaxErr);
   EXPECT_NEAR(t.m13, u.m13, kMaxErr);
@@ -340,6 +340,42 @@ void ExpectTransform3DEqual(const CATransform3D& t, const CATransform3D& u) {
   EXPECT_TRUE(mutatorView.platformViewContainer.isFlipped);
 }
 
+TEST(FlutterMutatorViewTest, RectsClipsToPathWhenRotated) {
+  NSView* platformView = [[NSView alloc] init];
+  FlutterMutatorView* mutatorView = [[FlutterMutatorView alloc] initWithPlatformView:platformView];
+  std::vector<FlutterPlatformViewMutation> mutations{
+      {
+          .type = kFlutterPlatformViewMutationTypeTransformation,
+          // Roation M_PI / 8
+          .transformation =
+              FlutterTransformation{
+                  .scaleX = 0.9238795325112867,
+                  .skewX = -0.3826834323650898,
+                  .skewY = 0.3826834323650898,
+                  .scaleY = 0.9238795325112867,
+              },
+      },
+      {
+          .type = kFlutterPlatformViewMutationTypeClipRect,
+          .clip_rect = FlutterRect{110, 60, 150, 150},
+      },
+      {
+          .type = kFlutterPlatformViewMutationTypeTransformation,
+          .transformation =
+              FlutterTransformation{
+                  .scaleX = 1,
+                  .transX = 100,
+                  .scaleY = 1,
+                  .transY = 50,
+              },
+      },
+  };
+  ApplyFlutterLayer(mutatorView, FlutterSize{30, 20}, mutations);
+  EXPECT_EQ(mutatorView.pathClipViews.count, 1ul);
+  EXPECT_NEAR(mutatorView.platformViewContainer.frame.size.width, 35.370054622640396, kMaxErr);
+  EXPECT_NEAR(mutatorView.platformViewContainer.frame.size.height, 29.958093621178421, kMaxErr);
+}
+
 TEST(FlutterMutatorViewTest, RoundRectClipsToPath) {
   NSView* platformView = [[NSView alloc] init];
   FlutterMutatorView* mutatorView = [[FlutterMutatorView alloc] initWithPlatformView:platformView];