[macOS] Multiview compositor

shell/platform/darwin/macos/framework/Source/FlutterCompositor.h

@@ -46,6 +46,18 @@ class FlutterCompositor {
 
  ~FlutterCompositor() = default;
 
+ // Allocate the resources for displaying a view.
+ //
+ // This method must be called when a view is added to FlutterEngine, and must be
+ // called on the main dispatch queue, or an assertion will be thrown.
+ void AddView(FlutterViewId view_id);
+
+ // Deallocate the resources for displaying a view.
+ //
+ // This method must be called when a view is removed from FlutterEngine, and
+ // must be called on the main dispatch queue, or an assertion will be thrown.
+ void RemoveView(FlutterViewId view_id);
+
  // Creates a backing store and saves updates the backing_store_out data with
  // the new FlutterBackingStore data.
  //
@@ -65,6 +77,11 @@ class FlutterCompositor {
  // `view_id` using the layer content.
  bool Present(FlutterViewIdentifier view_id, const FlutterLayer** layers, size_t layers_count);
 
+ // The number of views that the FlutterCompositor is keeping track of.
+ //
+ // This method must only be used in unit tests.
+ size_t DebugNumViews();
+
  private:
  // A class that contains the information for a view to be presented.
  class ViewPresenter {
@@ -103,7 +120,8 @@ class FlutterCompositor {
  // The controller used to manage creation and deletion of platform views.
  const FlutterPlatformViewController* platform_view_controller_;
 
- std::unordered_map<int64_t, ViewPresenter> presenters_;
+ // The view presenters for views. Each key is a view ID.
+ std::unordered_map<FlutterViewId, ViewPresenter> presenters_;
 
  FML_DISALLOW_COPY_AND_ASSIGN(FlutterCompositor);
 };

shell/platform/darwin/macos/framework/Source/FlutterCompositor.mm

@@ -41,12 +41,19 @@
  FML_CHECK(view_provider != nullptr) << "view_provider cannot be nullptr";
 }
 
+void FlutterCompositor::AddView(FlutterViewId view_id) {
+ dispatch_assert_queue(dispatch_get_main_queue());
+ presenters_.try_emplace(view_id);
+}
+
+void FlutterCompositor::RemoveView(FlutterViewId view_id) {
+ dispatch_assert_queue(dispatch_get_main_queue());
+ presenters_.erase(view_id);
+}
+
 bool FlutterCompositor::CreateBackingStore(const FlutterBackingStoreConfig* config,
  FlutterBackingStore* backing_store_out) {
- // TODO(dkwingsmt): This class only supports single-view for now. As more
- // classes are gradually converted to multi-view, it should get the view ID
- // from somewhere.
- FlutterView* view = [view_provider_ viewForIdentifier:kFlutterImplicitViewId];
+ FlutterView* view = [view_provider_ viewForIdentifier:config->view_id];
  if (!view) {
  return false;
  }
@@ -103,18 +110,31 @@
  // the layer information instead of passing the original pointers from embedder.
  auto layers_copy = std::make_shared<std::vector<LayerVariant>>(CopyLayers(layers, layers_count));
 
- [view.surfaceManager
- presentSurfaces:surfaces
- atTime:presentation_time
- notify:^{
- // Gets a presenter or create a new one for the view.
- ViewPresenter& presenter = presenters_[view_id];
- presenter.PresentPlatformViews(view, *layers_copy, platform_view_controller_);
- }];
+ [view.surfaceManager presentSurfaces:surfaces
+ atTime:presentation_time
+ notify:^{
+ // Accessing presenters_ here does not need a
+ // lock to avoid race condition against
+ // AddView and RemoveView, since all three
+ // take place on the platform thread. (The
+ // macOS API requires platform view presenting
+ // to take place on the platform thread,
+ // enforced by `FlutterThreadSynchronizer`.)
+ dispatch_assert_queue(dispatch_get_main_queue());
+ auto found_presenter = presenters_.find(view_id);
+ if (found_presenter != presenters_.end()) {
+ found_presenter->second.PresentPlatformViews(
+ view, *layers_copy, platform_view_controller_);
+ }
+ }];
 
  return true;
 }
 
+size_t FlutterCompositor::DebugNumViews() {
+ return presenters_.size();
+}
+
 FlutterCompositor::ViewPresenter::ViewPresenter()
  : mutator_views_([NSMapTable strongToStrongObjectsMapTable]) {}
 

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

@@ -528,6 +528,12 @@ - (instancetype)initWithName:(NSString*)labelPrefix
 
  _platformViewController = [[FlutterPlatformViewController alloc] init];
  _threadSynchronizer = [[FlutterThreadSynchronizer alloc] init];
+ // The macOS compositor must be initialized in the initializer because it is
+ // used when adding views, which might happen before runWithEntrypoint.
+ _macOSCompositor = std::make_unique<flutter::FlutterCompositor>(
+ [[FlutterViewEngineProvider alloc] initWithEngine:self],
+ [[FlutterTimeConverter alloc] initWithEngine:self], _platformViewController);
+
  [self setUpPlatformViewChannel];
  [self setUpAccessibilityChannel];
  [self setUpNotificationCenterListeners];
@@ -731,6 +737,7 @@ - (void)loadAOTData:(NSString*)assetsDir {
 
 - (void)registerViewController:(FlutterViewController*)controller
  forIdentifier:(FlutterViewIdentifier)viewIdentifier {
+ _macOSCompositor->AddView(viewIdentifier);
  NSAssert(controller != nil, @"The controller must not be nil.");
  NSAssert(controller.engine == nil,
  @"The FlutterViewController is unexpectedly attached to "
@@ -785,6 +792,7 @@ - (void)viewControllerViewDidLoad:(FlutterViewController*)viewController {
 }
 
 - (void)deregisterViewControllerForIdentifier:(FlutterViewIdentifier)viewIdentifier {
+ _macOSCompositor->RemoveView(viewIdentifier);
  FlutterViewController* controller = [self viewControllerForIdentifier:viewIdentifier];
  // The controller can be nil. The engine stores only a weak ref, and this
  // method could have been called from the controller's dealloc.
@@ -852,10 +860,6 @@ - (FlutterViewController*)viewController {
 }
 
 - (FlutterCompositor*)createFlutterCompositor {
- _macOSCompositor = std::make_unique<flutter::FlutterCompositor>(
- [[FlutterViewEngineProvider alloc] initWithEngine:self],
- [[FlutterTimeConverter alloc] initWithEngine:self], _platformViewController);
-
  _compositor = {};
  _compositor.struct_size = sizeof(FlutterCompositor);
  _compositor.user_data = _macOSCompositor.get();

shell/platform/darwin/macos/framework/Source/FlutterEngineTest.mm

@@ -940,6 +940,31 @@ @implementation MockableFlutterEngine
  EXPECT_EQ(viewController1.viewIdentifier, 0ll);
 }
 
+TEST_F(FlutterEngineTest, RemovingViewDisposesCompositorResources) {
+ NSString* fixtures = @(flutter::testing::GetFixturesPath());
+ FlutterDartProject* project = [[FlutterDartProject alloc]
+ initWithAssetsPath:fixtures
+ ICUDataPath:[fixtures stringByAppendingString:@"/icudtl.dat"]];
+ FlutterEngine* engine = [[FlutterEngine alloc] initWithName:@"test" project:project];
+
+ FlutterViewController* viewController = [[FlutterViewController alloc] initWithEngine:engine
+ nibName:nil
+ bundle:nil];
+ [viewController loadView];
+ [viewController viewDidLoad];
+ viewController.flutterView.frame = CGRectMake(0, 0, 800, 600);
+
+ EXPECT_TRUE([engine runWithEntrypoint:@"drawIntoAllViews"]);
+ [engine.testThreadSynchronizer blockUntilFrameAvailable];
+ EXPECT_EQ(engine.macOSCompositor->DebugNumViews(), 1u);
+
+ engine.viewController = nil;
+ EXPECT_EQ(engine.macOSCompositor->DebugNumViews(), 0u);
+
+ [engine shutDownEngine];
+ engine = nil;
+}
+
 TEST_F(FlutterEngineTest, HandlesTerminationRequest) {
  id engineMock = CreateMockFlutterEngine(nil);
  __block NSString* nextResponse = @"exit";

shell/platform/darwin/macos/framework/Source/fixtures/flutter_desktop_test.dart

@@ -49,6 +49,18 @@ void canCompositePlatformViews() {
  PlatformDispatcher.instance.scheduleFrame();
 }
 
+@pragma('vm:entry-point')
+void drawIntoAllViews() {
+ PlatformDispatcher.instance.onBeginFrame = (Duration duration) {
+ SceneBuilder builder = SceneBuilder();
+ builder.addPicture(Offset(1.0, 1.0), _createSimplePicture());
+ for (final FlutterView view in PlatformDispatcher.instance.views) {
+ view.render(builder.build());
+ }
+ };
+ PlatformDispatcher.instance.scheduleFrame();
+}
+
 /// Returns a [Picture] of a simple black square.
 Picture _createSimplePicture() {
  Paint blackPaint = Paint();