[platform_view] fix overlapping platform view not touchable

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

@@ -771,29 +771,16 @@ static bool ClipRRectContainsPlatformViewBoundingRect(const SkRRect& clip_rrect,
 void FlutterPlatformViewsController::BringLayersIntoView(LayersMap layer_map) {
   FML_DCHECK(flutter_view_);
   UIView* flutter_view = flutter_view_.get();
-  auto zIndex = 0;
   // Clear the `active_composition_order_`, which will be populated down below.
   active_composition_order_.clear();
   for (size_t i = 0; i < composition_order_.size(); i++) {
     int64_t platform_view_id = composition_order_[i];
     std::vector<std::shared_ptr<FlutterPlatformViewLayer>> layers = layer_map[platform_view_id];
     UIView* platform_view_root = root_views_[platform_view_id].get();
-
-    if (platform_view_root.superview != flutter_view) {
-      [flutter_view addSubview:platform_view_root];
-    }
-    // Make sure the platform_view_root is higher than the last platform_view_root in
-    // composition_order_.
-    platform_view_root.layer.zPosition = zIndex++;
-
+    // `addSubview` will automatically reorder subview if it is already added.
+    [flutter_view addSubview:platform_view_root];
     for (const std::shared_ptr<FlutterPlatformViewLayer>& layer : layers) {
-      if ([layer->overlay_view_wrapper.get() superview] != flutter_view) {
-        [flutter_view addSubview:layer->overlay_view_wrapper];
-      }
-      // Make sure all the overlays are higher than the platform view.
-      layer->overlay_view_wrapper.get().layer.zPosition = zIndex++;
-      FML_DCHECK(layer->overlay_view_wrapper.get().layer.zPosition >
-                 platform_view_root.layer.zPosition);
+      [flutter_view addSubview:layer->overlay_view_wrapper];
     }
     active_composition_order_.push_back(platform_view_id);
   }

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

@@ -2345,6 +2345,101 @@ - (void)testFlutterPlatformViewControllerBeginFrameShouldResetCompisitionOrder {
   XCTAssertEqual(flutterPlatformViewsController->GetCurrentBuilders().size(), 1UL);
 }
 
+- (void)testFlutterPlatformViewControllerSubmitFrameShouldOrderSubviewsCorrectly {
+  flutter::FlutterPlatformViewsTestMockPlatformViewDelegate mock_delegate;
+  auto thread_task_runner = CreateNewThread("FlutterPlatformViewsTest");
+  flutter::TaskRunners runners(/*label=*/self.name.UTF8String,
+                               /*platform=*/thread_task_runner,
+                               /*raster=*/thread_task_runner,
+                               /*ui=*/thread_task_runner,
+                               /*io=*/thread_task_runner);
+  auto flutterPlatformViewsController = std::make_shared<flutter::FlutterPlatformViewsController>();
+  auto platform_view = std::make_unique<flutter::PlatformViewIOS>(
+      /*delegate=*/mock_delegate,
+      /*rendering_api=*/flutter::IOSRenderingAPI::kSoftware,
+      /*platform_views_controller=*/flutterPlatformViewsController,
+      /*task_runners=*/runners);
+
+  UIView* mockFlutterView = [[[UIView alloc] initWithFrame:CGRectMake(0, 0, 500, 500)] autorelease];
+  flutterPlatformViewsController->SetFlutterView(mockFlutterView);
+
+  FlutterPlatformViewsTestMockFlutterPlatformFactory* factory =
+      [[FlutterPlatformViewsTestMockFlutterPlatformFactory new] autorelease];
+  flutterPlatformViewsController->RegisterViewFactory(
+      factory, @"MockFlutterPlatformView",
+      FlutterPlatformViewGestureRecognizersBlockingPolicyEager);
+  FlutterResult result = ^(id result) {
+  };
+  flutterPlatformViewsController->OnMethodCall(
+      [FlutterMethodCall
+          methodCallWithMethodName:@"create"
+                         arguments:@{@"id" : @0, @"viewType" : @"MockFlutterPlatformView"}],
+      result);
+  UIView* view1 = gMockPlatformView;
+
+  // This overwrites `gMockPlatformView` to another view.
+  flutterPlatformViewsController->OnMethodCall(
+      [FlutterMethodCall
+          methodCallWithMethodName:@"create"
+                         arguments:@{@"id" : @1, @"viewType" : @"MockFlutterPlatformView"}],
+      result);
+  UIView* view2 = gMockPlatformView;
+
+  flutterPlatformViewsController->BeginFrame(SkISize::Make(300, 300));
+  flutter::MutatorsStack stack;
+  SkMatrix finalMatrix;
+  auto embeddedViewParams1 =
+      std::make_unique<flutter::EmbeddedViewParams>(finalMatrix, SkSize::Make(300, 300), stack);
+  flutterPlatformViewsController->PrerollCompositeEmbeddedView(0, std::move(embeddedViewParams1));
+  flutterPlatformViewsController->CompositeEmbeddedView(0);
+  auto embeddedViewParams2 =
+      std::make_unique<flutter::EmbeddedViewParams>(finalMatrix, SkSize::Make(500, 500), stack);
+  flutterPlatformViewsController->PrerollCompositeEmbeddedView(1, std::move(embeddedViewParams2));
+  flutterPlatformViewsController->CompositeEmbeddedView(1);
+
+  // SKSurface is required if the root FlutterView is present.
+  const SkImageInfo image_info = SkImageInfo::MakeN32Premul(1000, 1000);
+  sk_sp<SkSurface> mock_sk_surface = SkSurface::MakeRaster(image_info);
+  flutter::SurfaceFrame::FramebufferInfo framebuffer_info;
+  auto mock_surface = std::make_unique<flutter::SurfaceFrame>(
+      std::move(mock_sk_surface), framebuffer_info,
+      [](const flutter::SurfaceFrame& surface_frame, SkCanvas* canvas) { return true; },
+      /*frame_size=*/SkISize::Make(800, 600));
+
+  XCTAssertTrue(
+      flutterPlatformViewsController->SubmitFrame(nullptr, nullptr, std::move(mock_surface)));
+  // platform view is wrapped by touch interceptor, which itself is wrapped by clipping view.
+  UIView* clippingView1 = view1.superview.superview;
+  UIView* clippingView2 = view2.superview.superview;
+  UIView* flutterView = clippingView1.superview;
+  XCTAssertTrue([flutterView.subviews indexOfObject:clippingView1] <
+                    [flutterView.subviews indexOfObject:clippingView2],
+                @"The first clipping view should be added before the second clipping view.");
+
+  // Need to recreate these params since they are `std::move`ed.
+  flutterPlatformViewsController->BeginFrame(SkISize::Make(300, 300));
+  // Process the second frame in the opposite order.
+  embeddedViewParams2 =
+      std::make_unique<flutter::EmbeddedViewParams>(finalMatrix, SkSize::Make(500, 500), stack);
+  flutterPlatformViewsController->PrerollCompositeEmbeddedView(1, std::move(embeddedViewParams2));
+  flutterPlatformViewsController->CompositeEmbeddedView(1);
+  embeddedViewParams1 =
+      std::make_unique<flutter::EmbeddedViewParams>(finalMatrix, SkSize::Make(300, 300), stack);
+  flutterPlatformViewsController->PrerollCompositeEmbeddedView(0, std::move(embeddedViewParams1));
+  flutterPlatformViewsController->CompositeEmbeddedView(0);
+
+  mock_sk_surface = SkSurface::MakeRaster(image_info);
+  mock_surface = std::make_unique<flutter::SurfaceFrame>(
+      std::move(mock_sk_surface), framebuffer_info,
+      [](const flutter::SurfaceFrame& surface_frame, SkCanvas* canvas) { return true; },
+      /*frame_size=*/SkISize::Make(800, 600));
+  XCTAssertTrue(
+      flutterPlatformViewsController->SubmitFrame(nullptr, nullptr, std::move(mock_surface)));
+  XCTAssertTrue([flutterView.subviews indexOfObject:clippingView1] >
+                    [flutterView.subviews indexOfObject:clippingView2],
+                @"The first clipping view should be added after the second clipping view.");
+}
+
 - (void)testThreadMergeAtEndFrame {
   flutter::FlutterPlatformViewsTestMockPlatformViewDelegate mock_delegate;
   auto thread_task_runner_platform = CreateNewThread("FlutterPlatformViewsTest1");

testing/ios/IosUnitTests/Tests/FlutterEngineConfig.xcconfig

@@ -1,2 +1,3 @@
 FLUTTER_ENGINE[arch=x86_64]=ios_debug_sim_unopt
 FLUTTER_ENGINE[arch=arm64]=ios_debug_sim_unopt_arm64
+FLUTTER_ENGINE=ios_debug_sim_unopt

testing/scenario_app/ios/Scenarios/Scenarios/AppDelegate.m

@@ -60,6 +60,8 @@ - (BOOL)application:(UIApplication*)application
     @"--gesture-reject-after-touches-ended" : @"platform_view_gesture_reject_after_touches_ended",
     @"--gesture-reject-eager" : @"platform_view_gesture_reject_eager",
     @"--gesture-accept" : @"platform_view_gesture_accept",
+    @"--gesture-accept-with-overlapping-platform-views" :
+        @"platform_view_gesture_accept_with_overlapping_platform_views",
     @"--tap-status-bar" : @"tap_status_bar",
     @"--animated-color-square" : @"animated_color_square",
     @"--platform-view-with-continuous-texture" : @"platform_view_with_continuous_texture",

testing/scenario_app/ios/Scenarios/ScenariosUITests/PlatformViewGestureRecognizerTests.m

@@ -165,4 +165,32 @@ - (XCUICoordinate*)getNormalizedCoordinate:(XCUIApplication*)app point:(CGVector
   return coordinate;
 }
 
+- (void)testGestureWithOverlappingPlatformViews {
+  XCUIApplication* app = [[XCUIApplication alloc] init];
+  app.launchArguments = @[ @"--gesture-accept-with-overlapping-platform-views" ];
+  [app launch];
+
+  XCUIElement* foreground = app.otherElements[@"platform_view[0]"];
+  XCTAssertEqual(foreground.frame.origin.x, 50);
+  XCTAssertEqual(foreground.frame.origin.y, 50);
+  XCTAssertEqual(foreground.frame.size.width, 50);
+  XCTAssertEqual(foreground.frame.size.height, 50);
+  XCTAssertTrue([foreground waitForExistenceWithTimeout:kSecondsToWaitForPlatformView]);
+
+  XCUIElement* background = app.otherElements[@"platform_view[1]"];
+  XCTAssertEqual(background.frame.origin.x, 0);
+  XCTAssertEqual(background.frame.origin.y, 0);
+  XCTAssertEqual(background.frame.size.width, 150);
+  XCTAssertEqual(background.frame.size.height, 150);
+  XCTAssertTrue([background waitForExistenceWithTimeout:kSecondsToWaitForPlatformView]);
+
+  XCUIElement* textView = foreground.textViews.firstMatch;
+  XCTAssertTrue(textView.exists);
+
+  XCTAssertTrue(foreground.isHittable);
+  [foreground tap];
+
+  XCTAssertEqualObjects(textView.label,
+                        @"-gestureTouchesBegan-gestureTouchesEnded-platformViewTapped");
+}
 @end

testing/scenario_app/lib/src/platform_view.dart

@@ -1056,6 +1056,133 @@ class PlatformViewForTouchIOSScenario extends Scenario
   }
 }
 
+/// Scenario for verifying overlapping platform views can accept touch gesture.
+/// See: https://github.com/flutter/flutter/issues/118366.
+///
+/// Renders the first frame with a foreground platform view.
+/// Then renders the second frame with the foreground platform view covering
+/// a new background platform view.
+///
+class PlatformViewForOverlappingPlatformViewsScenario extends Scenario
+    with _BasePlatformViewScenarioMixin {
+
+  /// Creates the PlatformViewForOverlappingPlatformViewsScenario.
+  ///
+  /// The [dispatcher] parameter must not be null.
+  PlatformViewForOverlappingPlatformViewsScenario(
+      PlatformDispatcher dispatcher, {
+        required this.foregroundId,
+        required this.backgroundId,
+      })  : super(dispatcher) {
+    _nextFrame = _firstFrame;
+  }
+
+  /// The id for a foreground platform view that covers another background platform view.
+  /// A good example is a dialog prompt in a real app.
+  final int foregroundId;
+
+  /// The id for a background platform view that is covered by a foreground platform view.
+  final int backgroundId;
+
+  late void Function() _nextFrame;
+
+  @override
+  void onBeginFrame(Duration duration) {
+    _nextFrame();
+  }
+
+  void _firstFrame() {
+    final SceneBuilder builder = SceneBuilder();
+
+    builder.pushOffset(100, 100);
+    addPlatformView(
+      foregroundId,
+      width: 100,
+      height: 100,
+      dispatcher: dispatcher,
+      sceneBuilder: builder,
+      text: 'Foreground',
+    );
+    builder.pop();
+
+    final Scene scene = builder.build();
+    window.render(scene);
+    scene.dispose();
+  }
+
+  void _secondFrame() {
+    final SceneBuilder builder = SceneBuilder();
+
+    builder.pushOffset(0, 0);
+    addPlatformView(
+      backgroundId,
+      width: 300,
+      height: 300,
+      dispatcher: dispatcher,
+      sceneBuilder: builder,
+      text: 'Background',
+    );
+    builder.pop();
+
+    builder.pushOffset(100, 100);
+    addPlatformView(
+      foregroundId,
+      width: 100,
+      height: 100,
+      dispatcher: dispatcher,
+      sceneBuilder: builder,
+      text: 'Foreground',
+    );
+    builder.pop();
+
+    final Scene scene = builder.build();
+    window.render(scene);
+    scene.dispose();
+  }
+
+  int _frameCount = 0;
+
+  @override
+  void onDrawFrame() {
+    _frameCount += 1;
+    // TODO(hellohuanlin): Need further investigation - the first 2 frames are dropped for some reason.
+    // Wait for 60 frames to ensure the first frame has actually been rendered
+    // (Minimum required is 3 frames, but just to be safe)
+    if (_nextFrame == _firstFrame && _frameCount == 60) {
+      _nextFrame = _secondFrame;
+    }
+    window.scheduleFrame();
+    super.onDrawFrame();
+  }
+
+  @override
+  void onPointerDataPacket(PointerDataPacket packet) {
+    final PointerData data = packet.data.first;
+    final double x = data.physicalX;
+    final double y = data.physicalY;
+    if (data.change == PointerChange.up && 100 <= x && x < 200 && 100 <= y && y < 200) {
+      const int valueString = 7;
+      const int valueInt32 = 3;
+      const int valueMap = 13;
+      final Uint8List message = Uint8List.fromList(<int>[
+        valueString,
+        ..._encodeString('acceptGesture'),
+        valueMap,
+        1,
+        valueString,
+        ..._encodeString('id'),
+        valueInt32,
+        ..._to32(foregroundId),
+      ]);
+      window.sendPlatformMessage(
+        'flutter/platform_views',
+        message.buffer.asByteData(),
+            (ByteData? response) {},
+      );
+    }
+  }
+}
+
 /// A simple platform view for testing platform view with a continuous texture layer.
 /// For example, it simulates a video being played.
 class PlatformViewWithContinuousTexture extends PlatformViewScenario {

testing/scenario_app/lib/src/scenarios.dart

@@ -51,6 +51,7 @@ Map<String, ScenarioFactory> _scenarios = <String, ScenarioFactory>{
   'platform_view_gesture_reject_eager': () => PlatformViewForTouchIOSScenario(PlatformDispatcher.instance,  id: _viewId++, accept: false),
   'platform_view_gesture_accept': () => PlatformViewForTouchIOSScenario(PlatformDispatcher.instance, id: _viewId++, accept: true),
   'platform_view_gesture_reject_after_touches_ended': () => PlatformViewForTouchIOSScenario(PlatformDispatcher.instance, id: _viewId++, accept: false, rejectUntilTouchesEnded: true),
+  'platform_view_gesture_accept_with_overlapping_platform_views': () => PlatformViewForOverlappingPlatformViewsScenario(PlatformDispatcher.instance, foregroundId: _viewId++, backgroundId: _viewId++),
   'platform_view_scrolling_under_widget':()=>PlatformViewScrollingUnderWidget(PlatformDispatcher.instance, firstPlatformViewId: _viewId++, lastPlatformViewId: _viewId+=16),
   'tap_status_bar': () => TouchesScenario(PlatformDispatcher.instance),
   'initial_route_reply': () => InitialRouteReply(PlatformDispatcher.instance),