[iOS] Fix platfotm view called multiple times (flutter/engine#19292)

engine/src/flutter/flow/embedded_views.h

@@ -124,7 +124,7 @@ class Mutator {
 //
 // For example consider the following stack: [T1, T2, T3], where T1 is the top
 // of the stack and T3 is the bottom of the stack. Applying this mutators stack
-// to a platform view P1 will result in T1(T2(T2(P1))).
+// to a platform view P1 will result in T1(T2(T3(P1))).
 class MutatorsStack {
  public:
   MutatorsStack() = default;

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterPlatformViews.mm

@@ -157,13 +157,13 @@ void FlutterPlatformViewsController::OnCreate(FlutterMethodCall* call, FlutterRe
   NSObject<FlutterPlatformView>* embedded_view = [factory createWithFrame:CGRectZero
                                                            viewIdentifier:viewId
                                                                 arguments:params];
+  UIView* platform_view = [embedded_view view];
   // Set a unique view identifier, so the platform view can be identified in unit tests.
-  [embedded_view view].accessibilityIdentifier =
-      [NSString stringWithFormat:@"platform_view[%ld]", viewId];
+  platform_view.accessibilityIdentifier = [NSString stringWithFormat:@"platform_view[%ld]", viewId];
   views_[viewId] = fml::scoped_nsobject<NSObject<FlutterPlatformView>>([embedded_view retain]);
 
   FlutterTouchInterceptingView* touch_interceptor = [[[FlutterTouchInterceptingView alloc]
-                  initWithEmbeddedView:embedded_view.view
+                  initWithEmbeddedView:platform_view
                platformViewsController:GetWeakPtr()
       gestureRecognizersBlockingPolicy:gesture_recognizers_blocking_policies[viewType]]
       autorelease];
@@ -311,11 +311,11 @@ void FlutterPlatformViewsController::PrerollCompositeEmbeddedView(
   views_to_recomposite_.insert(view_id);
 }
 
-NSObject<FlutterPlatformView>* FlutterPlatformViewsController::GetPlatformViewByID(int view_id) {
+UIView* FlutterPlatformViewsController::GetPlatformViewByID(int view_id) {
   if (views_.empty()) {
     return nil;
   }
-  return views_[view_id].get();
+  return [touch_interceptors_[view_id].get() embeddedView];
 }
 
 std::vector<SkCanvas*> FlutterPlatformViewsController::GetCurrentCanvases() {
@@ -451,7 +451,7 @@ void FlutterPlatformViewsController::Reset() {
 }
 
 SkRect FlutterPlatformViewsController::GetPlatformViewRect(int view_id) {
-  UIView* platform_view = [views_[view_id].get() view];
+  UIView* platform_view = GetPlatformViewByID(view_id);
   UIScreen* screen = [UIScreen mainScreen];
   CGRect platform_view_cgrect = [platform_view convertRect:platform_view.bounds
                                                     toView:flutter_view_];
@@ -747,6 +747,7 @@ void FlutterPlatformViewsController::CommitCATransactionIfNeeded() {
 @implementation FlutterTouchInterceptingView {
   fml::scoped_nsobject<DelayingGestureRecognizer> _delayingRecognizer;
   FlutterPlatformViewGestureRecognizersBlockingPolicy _blockingPolicy;
+  UIView* _embeddedView;
 }
 - (instancetype)initWithEmbeddedView:(UIView*)embeddedView
              platformViewsController:
@@ -756,6 +757,7 @@ void FlutterPlatformViewsController::CommitCATransactionIfNeeded() {
   self = [super initWithFrame:embeddedView.frame];
   if (self) {
     self.multipleTouchEnabled = YES;
+    _embeddedView = embeddedView;
     embeddedView.autoresizingMask =
         (UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight);
 
@@ -777,6 +779,10 @@ void FlutterPlatformViewsController::CommitCATransactionIfNeeded() {
   return self;
 }
 
+- (UIView*)embeddedView {
+  return [[_embeddedView retain] autorelease];
+}
+
 - (void)releaseGesture {
   _delayingRecognizer.get().state = UIGestureRecognizerStateFailed;
 }

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterPlatformViewsTest.mm

@@ -39,6 +39,7 @@ const float kFloatCompareEpsilon = 0.001;
 
 @interface FlutterPlatformViewsTestMockFlutterPlatformView : NSObject <FlutterPlatformView>
 @property(nonatomic, strong) UIView* view;
+@property(nonatomic, assign) BOOL viewCreated;
 @end
 
 @implementation FlutterPlatformViewsTestMockFlutterPlatformView
@@ -46,10 +47,23 @@ const float kFloatCompareEpsilon = 0.001;
 - (instancetype)init {
   if (self = [super init]) {
     _view = [[FlutterPlatformViewsTestMockPlatformView alloc] init];
+    _viewCreated = NO;
   }
   return self;
 }
 
+- (UIView*)view {
+  [self checkViewCreatedOnce];
+  return _view;
+}
+
+- (void)checkViewCreatedOnce {
+  if (self.viewCreated) {
+    abort();
+  }
+  self.viewCreated = YES;
+}
+
 - (void)dealloc {
   [_view release];
   _view = nil;
@@ -107,6 +121,60 @@ fml::RefPtr<fml::TaskRunner> CreateNewThread(std::string name) {
 
 @implementation FlutterPlatformViewsTest
 
+- (void)testFlutterViewOnlyCreateOnceInOneFrame {
+  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);
+
+  FlutterPlatformViewsTestMockFlutterPlatformFactory* factory =
+      [[FlutterPlatformViewsTestMockFlutterPlatformFactory new] autorelease];
+  flutterPlatformViewsController->RegisterViewFactory(
+      factory, @"MockFlutterPlatformView",
+      FlutterPlatformViewGestureRecognizersBlockingPolicyEager);
+  FlutterResult result = ^(id result) {
+  };
+  flutterPlatformViewsController->OnMethodCall(
+      [FlutterMethodCall
+          methodCallWithMethodName:@"create"
+                         arguments:@{@"id" : @2, @"viewType" : @"MockFlutterPlatformView"}],
+      result);
+  UIView* mockFlutterView = [[[UIView alloc] initWithFrame:CGRectMake(0, 0, 500, 500)] autorelease];
+  flutterPlatformViewsController->SetFlutterView(mockFlutterView);
+  // Create embedded view params
+  flutter::MutatorsStack stack;
+  // Layer tree always pushes a screen scale factor to the stack
+  SkMatrix screenScaleMatrix =
+      SkMatrix::MakeScale([UIScreen mainScreen].scale, [UIScreen mainScreen].scale);
+  stack.PushTransform(screenScaleMatrix);
+  // Push a translate matrix
+  SkMatrix translateMatrix = SkMatrix::MakeTrans(100, 100);
+  stack.PushTransform(translateMatrix);
+  SkMatrix finalMatrix;
+  finalMatrix.setConcat(screenScaleMatrix, translateMatrix);
+
+  auto embeddedViewParams =
+      std::make_unique<flutter::EmbeddedViewParams>(finalMatrix, SkSize::Make(300, 300), stack);
+
+  flutterPlatformViewsController->PrerollCompositeEmbeddedView(2, std::move(embeddedViewParams));
+  flutterPlatformViewsController->CompositeEmbeddedView(2);
+
+  flutterPlatformViewsController->GetPlatformViewRect(2);
+
+  XCTAssertNotNil(gMockPlatformView);
+
+  flutterPlatformViewsController->Reset();
+}
+
 - (void)testCanCreatePlatformViewWithoutFlutterView {
   flutter::FlutterPlatformViewsTestMockPlatformViewDelegate mock_delegate;
   auto thread_task_runner = CreateNewThread("FlutterPlatformViewsTest");

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterPlatformViews_Internal.h

@@ -150,12 +150,12 @@ class FlutterPlatformViewsController {
   void PrerollCompositeEmbeddedView(int view_id,
                                     std::unique_ptr<flutter::EmbeddedViewParams> params);
 
-  // Returns the `FlutterPlatformView` object associated with the view_id.
+  // Returns the `FlutterPlatformView`'s `view` object associated with the view_id.
   //
   // If the `FlutterPlatformViewsController` does not contain any `FlutterPlatformView` object or
   // a `FlutterPlatformView` object asscociated with the view_id cannot be found, the method
   // returns nil.
-  NSObject<FlutterPlatformView>* GetPlatformViewByID(int view_id);
+  UIView* GetPlatformViewByID(int view_id);
 
   PostPrerollResult PostPrerollAction(fml::RefPtr<fml::RasterThreadMerger> raster_thread_merger);
 
@@ -331,6 +331,9 @@ class FlutterPlatformViewsController {
 
 // Prevent the touch sequence from ever arriving to the embedded view.
 - (void)blockGesture;
+
+// Get embedded view
+- (UIView*)embeddedView;
 @end
 
 #endif  // FLUTTER_SHELL_PLATFORM_DARWIN_IOS_FRAMEWORK_SOURCE_FLUTTERPLATFORMVIEWS_INTERNAL_H_

engine/src/flutter/shell/platform/darwin/ios/framework/Source/SemanticsObject.mm

@@ -559,7 +559,7 @@ flutter::SemanticsAction GetSemanticsActionForScrollDirection(
     _semanticsObject = object;
     auto controller = object.bridge->GetPlatformViewsController();
     if (controller) {
-      _platformView = [[controller->GetPlatformViewByID(object.node.platformViewId) view] retain];
+      _platformView = [controller->GetPlatformViewByID(object.node.platformViewId) retain];
     }
   }
   return self;

engine/src/flutter/testing/scenario_app/ios/Scenarios/Scenarios/TextPlatformView.m

@@ -67,6 +67,7 @@
 @implementation TextPlatformView {
   UITextView* _textView;
   FlutterMethodChannel* _channel;
+  BOOL _viewCreated;
 }
 
 - (instancetype)initWithFrame:(CGRect)frame
@@ -87,11 +88,18 @@
     [_textView addGestureRecognizer:gestureRecognizer];
     gestureRecognizer.testTapGestureRecognizerDelegate = self;
     _textView.accessibilityLabel = @"";
+
+    _viewCreated = NO;
   }
   return self;
 }
 
 - (UIView*)view {
+  // Makes sure the engine only calls this method once.
+  if (_viewCreated) {
+    abort();
+  }
+  _viewCreated = YES;
   return _textView;
 }