[ios] Link PlatformView back to semantics tree

shell/platform/darwin/ios/framework/Source/FlutterPlatformViews.mm

@@ -406,10 +406,15 @@ static bool ClipRRectContainsPlatformViewBoundingRect(const SkRRect& clip_rrect,
 }
 
 UIView* FlutterPlatformViewsController::GetPlatformViewByID(int64_t view_id) {
+  return [GetFlutterTouchInterceptingViewByID(view_id) embeddedView];
+}
+
+FlutterTouchInterceptingView* FlutterPlatformViewsController::GetFlutterTouchInterceptingViewByID(
+    int64_t view_id) {
   if (views_.empty()) {
     return nil;
   }
-  return [touch_interceptors_[view_id].get() embeddedView];
+  return touch_interceptors_[view_id].get();
 }
 
 long FlutterPlatformViewsController::FindFirstResponderPlatformViewId() {
@@ -957,6 +962,7 @@ @implementation FlutterTouchInterceptingView {
   fml::scoped_nsobject<DelayingGestureRecognizer> _delayingRecognizer;
   FlutterPlatformViewGestureRecognizersBlockingPolicy _blockingPolicy;
   UIView* _embeddedView;
+  NSObject* _flutterAccessibilityContainer;
 }
 - (instancetype)initWithEmbeddedView:(UIView*)embeddedView
              platformViewsController:
@@ -1035,6 +1041,14 @@ - (void)touchesCancelled:(NSSet<UITouch*>*)touches withEvent:(UIEvent*)event {
 - (void)touchesEnded:(NSSet*)touches withEvent:(UIEvent*)event {
 }
 
+- (void)setFlutterAccessibilityContainer:(NSObject*)flutterAccessibilityContainer {
+  _flutterAccessibilityContainer = flutterAccessibilityContainer;
+}
+
+- (id)accessibilityContainer {
+  return _flutterAccessibilityContainer;
+}
+
 @end
 
 @implementation DelayingGestureRecognizer {

shell/platform/darwin/ios/framework/Source/FlutterPlatformViewsTest.mm

@@ -19,6 +19,10 @@
 static FlutterPlatformViewsTestMockPlatformView* gMockPlatformView = nil;
 const float kFloatCompareEpsilon = 0.001;
 
+@interface FlutterTouchInterceptingView (Test)
+- (id)accessibilityContainer;
+@end
+
 @interface FlutterPlatformViewsTestMockPlatformView : UIView
 @end
 @implementation FlutterPlatformViewsTestMockPlatformView
@@ -3099,4 +3103,12 @@ - (void)testOnlyPlatformViewsAreRemovedWhenReset {
   XCTAssertEqual(mockFlutterView.subviews.firstObject, someView);
 }
 
+- (void)testFlutterTouchInterceptingViewLinksToAccessibilityContainer {
+  FlutterTouchInterceptingView* touchInteceptorView =
+      [[[FlutterTouchInterceptingView alloc] init] autorelease];
+  NSObject* container = [[[NSObject alloc] init] autorelease];
+  [touchInteceptorView setFlutterAccessibilityContainer:container];
+  XCTAssertEqualObjects([touchInteceptorView accessibilityContainer], container);
+}
+
 @end

shell/platform/darwin/ios/framework/Source/FlutterPlatformViews_Internal.h

@@ -12,6 +12,7 @@
 #import "flutter/shell/platform/darwin/common/framework/Headers/FlutterChannels.h"
 #import "flutter/shell/platform/darwin/ios/framework/Headers/FlutterPlatformViews.h"
 #import "flutter/shell/platform/darwin/ios/framework/Headers/FlutterPlugin.h"
+#import "flutter/shell/platform/darwin/ios/framework/Source/SemanticsObject.h"
 #import "flutter/shell/platform/darwin/ios/ios_context.h"
 
 @class FlutterTouchInterceptingView;
@@ -234,6 +235,8 @@ class FlutterPlatformViewsController {
   // returns nil.
   UIView* GetPlatformViewByID(int64_t view_id);
 
+  FlutterTouchInterceptingView* GetFlutterTouchInterceptingViewByID(int64_t);
+
   PostPrerollResult PostPrerollAction(
       const fml::RefPtr<fml::RasterThreadMerger>& raster_thread_merger);
 
@@ -409,7 +412,7 @@ class FlutterPlatformViewsController {
 // This view has 2 roles:
 // 1. Delay or prevent touch events from arriving the embedded view.
 // 2. Dispatching all events that are hittested to the embedded view to the FlutterView.
-@interface FlutterTouchInterceptingView : UIView
+@interface FlutterTouchInterceptingView : UIView <FlutterSemanticsProtocol>
 - (instancetype)initWithEmbeddedView:(UIView*)embeddedView
              platformViewsController:
                  (fml::WeakPtr<flutter::FlutterPlatformViewsController>)platformViewsController
@@ -424,6 +427,7 @@ class FlutterPlatformViewsController {
 
 // Get embedded view
 - (UIView*)embeddedView;
+
 @end
 
 @interface UIView (FirstResponder)

shell/platform/darwin/ios/framework/Source/SemanticsObject.h

@@ -19,6 +19,14 @@ constexpr float kScrollExtentMaxForInf = 1000;
 @class FlutterCustomAccessibilityAction;
 @class FlutterPlatformViewSemanticsContainer;
 
+@protocol FlutterSemanticsProtocol <NSObject>
+// Adding functionalities for any object to assign accessibilityContainer.
+// For example, this allows the PlatformView be able to link back to the accessibility tree.
+// See: https://github.com/flutter/flutter/issues/135504
+- (void)setFlutterAccessibilityContainer:(NSObject*)flutterAccessibilityContainer;
+
+@end
+
 /**
  * A node in the iOS semantics tree. This object is a wrapper over a native accessibiliy
  * object, which is stored in the property `nativeAccessibility`. In the most case, the
@@ -171,7 +179,8 @@ constexpr float kScrollExtentMaxForInf = 1000;
 
 - (instancetype)initWithBridge:(fml::WeakPtr<flutter::AccessibilityBridgeIos>)bridge
                            uid:(int32_t)uid
-                  platformView:(UIView*)platformView NS_DESIGNATED_INITIALIZER;
+                  platformView:(UIView<FlutterSemanticsProtocol>*)platformView
+    NS_DESIGNATED_INITIALIZER;
 
 @end
 

shell/platform/darwin/ios/framework/Source/SemanticsObject.mm

@@ -5,7 +5,6 @@
 #import "flutter/shell/platform/darwin/ios/framework/Source/SemanticsObject.h"
 
 #include "flutter/fml/platform/darwin/scoped_nsobject.h"
-#import "flutter/shell/platform/darwin/ios/framework/Source/FlutterPlatformViews_Internal.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterSemanticsScrollView.h"
 
 namespace {
@@ -157,9 +156,7 @@ @interface FlutterScrollableSemanticsObject ()
 @property(nonatomic, retain) FlutterSemanticsScrollView* scrollView;
 @end
 
-@implementation FlutterScrollableSemanticsObject {
-  fml::scoped_nsobject<SemanticsObjectContainer> _container;
-}
+@implementation FlutterScrollableSemanticsObject
 
 - (instancetype)initWithBridge:(fml::WeakPtr<flutter::AccessibilityBridgeIos>)bridge
                            uid:(int32_t)uid {
@@ -865,9 +862,10 @@ @implementation FlutterPlatformViewSemanticsContainer
 
 - (instancetype)initWithBridge:(fml::WeakPtr<flutter::AccessibilityBridgeIos>)bridge
                            uid:(int32_t)uid
-                  platformView:(nonnull UIView*)platformView {
+                  platformView:(UIView<FlutterSemanticsProtocol>*)platformView {
   if (self = [super initWithBridge:bridge uid:uid]) {
     _platformView = [platformView retain];
+    [platformView setFlutterAccessibilityContainer:self];
   }
   return self;
 }
@@ -882,12 +880,6 @@ - (id)nativeAccessibility {
   return _platformView;
 }
 
-#pragma mark - UIAccessibilityContainer overrides
-
-- (NSArray*)accessibilityElements {
-  return @[ _platformView ];
-}
-
 @end
 
 @implementation SemanticsObjectContainer {

shell/platform/darwin/ios/framework/Source/SemanticsObjectTest.mm

@@ -89,6 +89,26 @@ void AccessibilityObjectDidLoseFocus(int32_t id) override {}
 }  // namespace
 }  // namespace flutter
 
+// A mock platform view for testing
+@interface TestPlatformView : UIView <FlutterSemanticsProtocol>
+
+@property(weak, nonatomic) NSObject* container;
+- (id)accessibilityContainer;
+
+@end
+
+@implementation TestPlatformView
+
+- (void)setFlutterAccessibilityContainer:(NSObject*)flutterAccessibilityContainer {
+  self.container = flutterAccessibilityContainer;
+}
+
+- (id)accessibilityContainer {
+  return self.container;
+}
+
+@end
+
 @interface SemanticsObjectTest : XCTestCase
 @end
 
@@ -210,7 +230,8 @@ - (void)testAccessibilityHitTestSearchCanReturnPlatformView {
   SemanticsObject* object0 = [[SemanticsObject alloc] initWithBridge:bridge uid:0];
   SemanticsObject* object1 = [[SemanticsObject alloc] initWithBridge:bridge uid:1];
   SemanticsObject* object3 = [[SemanticsObject alloc] initWithBridge:bridge uid:3];
-  UIView* platformView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
+  TestPlatformView* platformView =
+      [[TestPlatformView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
   FlutterPlatformViewSemanticsContainer* platformViewSemanticsContainer =
       [[FlutterPlatformViewSemanticsContainer alloc] initWithBridge:bridge
                                                                 uid:1
@@ -901,15 +922,15 @@ - (void)testFlutterPlatformViewSemanticsContainer {
   fml::WeakPtrFactory<flutter::MockAccessibilityBridge> factory(
       new flutter::MockAccessibilityBridge());
   fml::WeakPtr<flutter::MockAccessibilityBridge> bridge = factory.GetWeakPtr();
-  __weak UIView* weakPlatformView;
+  __weak TestPlatformView* weakPlatformView;
   @autoreleasepool {
-    UIView* platformView = [[UIView alloc] init];
+    TestPlatformView* platformView = [[TestPlatformView alloc] init];
 
     FlutterPlatformViewSemanticsContainer* container =
         [[FlutterPlatformViewSemanticsContainer alloc] initWithBridge:bridge
                                                                   uid:1
                                                          platformView:platformView];
-    XCTAssertEqualObjects(container.accessibilityElements, @[ platformView ]);
+    XCTAssertEqualObjects(platformView.accessibilityContainer, container);
     weakPlatformView = platformView;
     XCTAssertNotNil(weakPlatformView);
   }

shell/platform/darwin/ios/framework/Source/accessibility_bridge.mm

@@ -279,7 +279,7 @@ static void ReplaceSemanticsObject(SemanticsObject* oldObject,
     return [[[FlutterPlatformViewSemanticsContainer alloc]
         initWithBridge:weak_ptr
                    uid:node.id
-          platformView:weak_ptr->GetPlatformViewsController()->GetPlatformViewByID(
+          platformView:weak_ptr->GetPlatformViewsController()->GetFlutterTouchInterceptingViewByID(
                            node.platformViewId)] autorelease];
   } else {
     return [[[FlutterSemanticsObject alloc] initWithBridge:weak_ptr uid:node.id] autorelease];