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

flow/surface_frame.h

@@ -93,6 +93,19 @@ class SurfaceFrame {
     //
     // Defaults to true, which is generally a safe value.
     bool frame_boundary = true;
+
+    // Whether this surface presents with a CATransaction on Apple platforms.
+    //
+    // When there are platform views in the scene, the drawable needs to be
+    // presented in the same CATransaction as the one created for platform view
+    // mutations.
+    //
+    // If the drawables are being presented from the raster thread, we cannot
+    // 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.
+    bool present_with_transaction = false;
   };
 
   bool Encode();

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;
 
+  /// Mark this surface as presenting with a transaction.
+  ///
+  /// If true, [Present] will block on the scheduling of a command buffer.
+  void PresentWithTransaction(bool present_with_transaction) {
+    present_with_transaction_ = present_with_transaction;
+  }
+
   // |Surface|
   bool Present() const override;
 
@@ -74,6 +81,7 @@ class SurfaceMTL final : public Surface {
   bool requires_blit_ = false;
   std::optional<IRect> clip_rect_;
   bool frame_boundary_ = false;
+  bool present_with_transaction_ = false;
 
   static bool ShouldPerformPartialRepaint(std::optional<IRect> damage_rect);
 

impeller/renderer/backend/metal/surface_mtl.mm

@@ -286,7 +286,7 @@ - (void)flutterPrepareForPresent:(nonnull id<MTLCommandBuffer>)commandBuffer;
     // If the threads have been merged, or there is a pending frame capture,
     // then block on cmd buffer scheduling to ensure that the
     // transaction/capture work correctly.
-    if ([[NSThread currentThread] isMainThread] ||
+    if (present_with_transaction_ || [[NSThread currentThread] isMainThread] ||
         [[MTLCaptureManager sharedCaptureManager] isCapturing] ||
         alwaysWaitForScheduling) {
       TRACE_EVENT0("flutter", "waitUntilScheduled");

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

@@ -109,8 +109,11 @@
                          disable_partial_repaint = disable_partial_repaint_,  //
                          aiks_context = aiks_context_,                        //
                          drawable,                                            //
-                         last_texture                                         //
+                         last_texture,                                        //
+                         mtl_layer                                            //
   ](SurfaceFrame& surface_frame, DlCanvas* canvas) mutable -> bool {
+        mtl_layer.presentsWithTransaction = surface_frame.submit_info().present_with_transaction;
+
         if (!aiks_context) {
           return false;
         }
@@ -151,6 +154,7 @@
         if (!surface) {
           return false;
         }
+        surface->PresentWithTransaction(surface_frame.submit_info().present_with_transaction);
 
         if (clip_rect && clip_rect->IsEmpty()) {
           surface_frame.set_user_data(std::move(surface));
@@ -271,6 +275,8 @@
         auto surface = impeller::SurfaceMTL::MakeFromTexture(aiks_context->GetContext(),
                                                              mtl_texture, clip_rect);
 
+        surface->PresentWithTransaction(surface_frame.submit_info().present_with_transaction);
+
         if (clip_rect && clip_rect->IsEmpty()) {
           return surface->Present();
         }

shell/gpu/gpu_surface_metal_skia.mm

@@ -157,8 +157,9 @@
     return nullptr;
   }
 
-  auto encode_callback = [this, drawable](const SurfaceFrame& surface_frame,
-                                          DlCanvas* canvas) -> bool {
+  SurfaceFrame::EncodeCallback encode_callback =
+      [this, drawable, mtl_layer](const SurfaceFrame& surface_frame, DlCanvas* canvas) -> bool {
+    mtl_layer.presentsWithTransaction = surface_frame.submit_info().present_with_transaction;
     if (canvas == nullptr) {
       FML_DLOG(ERROR) << "Canvas not available.";
       return false;
@@ -186,7 +187,8 @@
     return true;
   };
 
-  auto submit_callback = [this, drawable](const SurfaceFrame& surface_frame) -> bool {
+  SurfaceFrame::SubmitCallback submit_callback =
+      [this, drawable](const SurfaceFrame& surface_frame) -> bool {
     TRACE_EVENT0("flutter", "GPUSurfaceMetal::Submit");
     return delegate_->PresentDrawable(drawable);
   };

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;
 }