[iOS] Supported rendering platform views without merging the raster thread.

flow/surface_frame.h

@@ -26,6 +26,9 @@ class SurfaceFrame {
   using SubmitCallback =
       std::function<bool(SurfaceFrame& surface_frame, DlCanvas* canvas)>;
 
+  using DeferredSubmit = std::function<bool()>;
+  using SubmitReciever = std::function<void(DeferredSubmit)>;
+
   // Information about the underlying framebuffer
   struct FramebufferInfo {
     // Indicates whether or not the surface supports pixel readback as used in
@@ -87,6 +90,10 @@ class SurfaceFrame {
     //
     // Defaults to true, which is generally a safe value.
     bool frame_boundary = true;
+
+    bool present_with_transaction = false;
+
+    SubmitReciever submit_receiver;
   };
 
   bool Submit();

impeller/renderer/backend/metal/surface_mtl.h

@@ -58,6 +58,13 @@ class SurfaceMTL final : public Surface {
   // Returns a Rect defining the area of the surface in device pixels
   IRect coverage() const;
 
+  using DeferredSubmit = std::function<bool()>;
+  using SubmitReciever = std::function<void(DeferredSubmit)>;
+
+  void SetSubmitInfo(const SubmitReciever& submit_reciever) {
+    submit_reciever_ = submit_reciever;
+  }
+
   // |Surface|
   bool Present() const override;
 
@@ -75,6 +82,8 @@ class SurfaceMTL final : public Surface {
   std::optional<IRect> clip_rect_;
   bool frame_boundary_ = false;
 
+  SubmitReciever submit_reciever_;
+
   static bool ShouldPerformPartialRepaint(std::optional<IRect> damage_rect);
 
   SurfaceMTL(const std::weak_ptr<Context>& context,

impeller/renderer/backend/metal/surface_mtl.mm

@@ -297,6 +297,14 @@ - (void)flutterPrepareForPresent:(nonnull id<MTLCommandBuffer>)commandBuffer;
       [command_buffer waitUntilScheduled];
 #endif  // defined(FML_OS_IOS_SIMULATOR) && defined(FML_ARCH_CPU_X86_64)
       [drawable_ present];
+    } else if (submit_reciever_) {
+      auto drawable = drawable_;
+      [command_buffer commit];
+      [command_buffer waitUntilScheduled];
+      submit_reciever_([drawable]() -> bool {
+        [drawable present];
+        return true;
+      });
     } else {
       // The drawable may come from a FlutterMetalLayer, so it can't be
       // presented through the command buffer.

shell/gpu/gpu_surface_metal_delegate.h

@@ -77,6 +77,8 @@ class GPUSurfaceMetalDelegate {
   ///
   virtual bool PresentDrawable(GrMTLHandle drawable) const = 0;
 
+  virtual bool PreparePresent(GrMTLHandle drawable) const { return true; }
+
   //------------------------------------------------------------------------------
   /// @brief Returns the handle to the MTLTexture to render to. This is only
   /// called when the specified render target type is `kMTLTexture`.

shell/gpu/gpu_surface_metal_impeller.mm

@@ -117,8 +117,18 @@
                          renderer = impeller_renderer_,                       //
                          aiks_context = aiks_context_,                        //
                          drawable,                                            //
-                         last_texture                                         //
+                         last_texture,                                        //
+                         mtl_layer                                            //
   ](SurfaceFrame& surface_frame, DlCanvas* canvas) mutable -> bool {
+        // When there are platform views in the scene, the drawable needs to be presented in the
+        // same transaction as the one created for platform views. When the drawable are being
+        // presented from the raster thread, we may not be able to use a transaction as it will
+        // dirty the UIViews being presented. If there is a non-Flutter UIView active, such as in
+        // add2app or a presentViewController page transition, then this will cause CoreAnimation
+        // assertion errors and
+        // exit the app.
+        mtl_layer.presentsWithTransaction = surface_frame.submit_info().present_with_transaction;
+
         if (!aiks_context) {
           return false;
         }
@@ -159,6 +169,7 @@
         if (!surface) {
           return false;
         }
+        surface->SetSubmitInfo(surface_frame.submit_info().submit_receiver);
 
         if (clip_rect && clip_rect->IsEmpty()) {
           return surface->Present();
@@ -286,6 +297,8 @@
         auto surface =
             impeller::SurfaceMTL::MakeFromTexture(renderer->GetContext(), mtl_texture, clip_rect);
 
+        surface->SetSubmitInfo(surface_frame.submit_info().submit_receiver);
+
         if (clip_rect && clip_rect->IsEmpty()) {
           return surface->Present();
         }

shell/gpu/gpu_surface_metal_skia.mm

@@ -152,8 +152,10 @@
     return nullptr;
   }
 
-  auto submit_callback = [this, drawable](const SurfaceFrame& surface_frame,
-                                          DlCanvas* canvas) -> bool {
+  auto submit_callback = [this, drawable, mtl_layer](const SurfaceFrame& surface_frame,
+                                                     DlCanvas* canvas) -> bool {
+    mtl_layer.presentsWithTransaction = surface_frame.submit_info().present_with_transaction;
+
     TRACE_EVENT0("flutter", "GPUSurfaceMetal::Submit");
     if (canvas == nullptr) {
       FML_DLOG(ERROR) << "Canvas not available.";
@@ -179,7 +181,15 @@
       damage_[texture] = SkIRect::MakeEmpty();
     }
 
-    return delegate_->PresentDrawable(drawable);
+    if (surface_frame.submit_info().submit_receiver) {
+      delegate_->PreparePresent(drawable);
+      surface_frame.submit_info().submit_receiver(
+          [&, drawable = drawable]() { return delegate_->PresentDrawable(drawable); });
+      return true;
+    } else {
+      delegate_->PreparePresent(drawable);
+      return delegate_->PresentDrawable(drawable);
+    }
   };
 
   SurfaceFrame::FramebufferInfo framebuffer_info;

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

@@ -219,7 +219,6 @@ - (instancetype)initWithName:(NSString*)labelPrefix
   _pluginPublications = [[NSMutableDictionary alloc] init];
   _registrars = [[NSMutableDictionary alloc] init];
   [self recreatePlatformViewController];
-
   _binaryMessenger = [[FlutterBinaryMessengerRelay alloc] initWithParent:self];
   _textureRegistry = [[FlutterTextureRegistryRelay alloc] initWithParent:self];
   _connections.reset(new flutter::ConnectionCollection());
@@ -869,6 +868,8 @@ - (BOOL)createShell:(NSString*)entrypoint
   flutter::Shell::CreateCallback<flutter::PlatformView> on_create_platform_view =
       [self](flutter::Shell& shell) {
         [self recreatePlatformViewController];
+        self->_platformViewsController->SetTaskRunner(
+            shell.GetTaskRunners().GetPlatformTaskRunner());
         return std::make_unique<flutter::PlatformViewIOS>(
             shell, self->_renderingApi, self->_platformViewsController, shell.GetTaskRunners(),
             shell.GetConcurrentWorkerTaskRunner(), shell.GetIsGpuDisabledSyncSwitch());
@@ -1468,6 +1469,8 @@ - (FlutterEngine*)spawnWithEntrypoint:(/*nullable*/ NSString*)entrypoint
   flutter::Shell::CreateCallback<flutter::PlatformView> on_create_platform_view =
       [result, context](flutter::Shell& shell) {
         [result recreatePlatformViewController];
+        result->_platformViewsController->SetTaskRunner(
+            shell.GetTaskRunners().GetPlatformTaskRunner());
         return std::make_unique<flutter::PlatformViewIOS>(
             shell, context, result->_platformViewsController, shell.GetTaskRunners());
       };

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

@@ -12,7 +12,6 @@
 FLUTTER_ASSERT_ARC
 
 // This is mostly a duplication of FlutterView.
-// TODO(amirh): once GL support is in evaluate if we can merge this with FlutterView.
 @implementation FlutterOverlayView {
   fml::CFRef<CGColorSpaceRef> _colorSpaceRef;
 }