WIP: Smooth window resizing on macOS

shell/platform/darwin/macos/BUILD.gn

@@ -67,6 +67,7 @@ source_set("flutter_framework_source") {
   sources += _flutter_framework_headers
 
   deps = [
+    "//flutter/fml:fml",
     "//flutter/shell/platform/darwin/common:framework_shared",
     "//flutter/shell/platform/embedder:embedder_as_internal_library",
   ]
@@ -79,7 +80,9 @@ source_set("flutter_framework_source") {
 
   libs = [
     "Cocoa.framework",
+    "QuartzCore.framework",
     "CoreVideo.framework",
+    "IOSurface.framework",
   ]
 }
 

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

@@ -139,8 +139,7 @@ static bool OnPresent(FlutterEngine* engine) {
 }
 
 static uint32_t OnFBO(FlutterEngine* engine) {
-  // There is currently no case where a different FBO is used, so no need to forward.
-  return 0;
+  return engine.viewController.flutterView.frameBufferId;
 }
 
 static bool OnMakeResourceCurrent(FlutterEngine* engine) {
@@ -262,7 +261,7 @@ - (BOOL)runWithEntrypoint:(NSString*)entrypoint {
   const FlutterCustomTaskRunners custom_task_runners = {
       .struct_size = sizeof(FlutterCustomTaskRunners),
       .platform_task_runner = &cocoa_task_runner_description,
-      .render_task_runner = &cocoa_task_runner_description,
+      .render_task_runner = nullptr,
   };
   flutterArguments.custom_task_runners = &custom_task_runners;
 
@@ -280,7 +279,8 @@ - (BOOL)runWithEntrypoint:(NSString*)entrypoint {
   }
 
   [self sendUserLocales];
-  [self updateWindowMetrics];
+
+  [self.viewController.flutterView start];
   return YES;
 }
 
@@ -291,7 +291,9 @@ - (void)setViewController:(FlutterViewController*)controller {
     [self shutDownEngine];
     _resourceContext = nil;
   }
-  [self updateWindowMetrics];
+  if (_engine) {
+    [self.viewController.flutterView start];
+  }
 }
 
 - (id<FlutterBinaryMessenger>)binaryMessenger {
@@ -317,6 +319,7 @@ - (NSOpenGLContext*)resourceContext {
   return _resourceContext;
 }
 
+// Must be driven by FlutterView (i.e. [FlutterView start])
 - (void)updateWindowMetrics {
   if (!_engine) {
     return;
@@ -334,6 +337,18 @@ - (void)updateWindowMetrics {
   FlutterEngineSendWindowMetricsEvent(_engine, &event);
 }
 
+- (void)scheduleOnRasterTread:(dispatch_block_t)block {
+  void* copy = Block_copy((__bridge void*)block);
+  FlutterEnginePostRenderThreadTask(
+      _engine,
+      [](void* cb) {
+        dispatch_block_t block = (__bridge dispatch_block_t)cb;
+        block();
+        Block_release(block);
+      },
+      copy);
+}
+
 - (void)sendPointerEvent:(const FlutterPointerEvent&)event {
   FlutterEngineSendPointerEvent(_engine, &event, 1);
 }
@@ -380,7 +395,7 @@ - (bool)engineCallbackOnPresent {
   if (!_mainOpenGLContext) {
     return false;
   }
-  [_mainOpenGLContext flushBuffer];
+  [self.viewController.flutterView present];
   return true;
 }
 

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

@@ -26,6 +26,11 @@
  */
 - (void)updateWindowMetrics;
 
+/**
+ * Schedules the block on rater thread.
+ */
+- (void)scheduleOnRasterTread:(nonnull dispatch_block_t)block;
+
 /**
  * Dispatches the given pointer event data to engine.
  */

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

@@ -7,32 +7,39 @@
 /**
  * Listener for view resizing.
  */
-@protocol FlutterViewReshapeListener <NSObject>
+@protocol FlutterViewDelegate <NSObject>
 /**
  * Called when the view's backing store changes size.
  */
 - (void)viewDidReshape:(nonnull NSView*)view;
+- (void)scheduleOnRasterTread:(nonnull dispatch_block_t)block;
+
 @end
 
 /**
  * View capable of acting as a rendering target and input source for the Flutter
  * engine.
  */
-@interface FlutterView : NSOpenGLView
+@interface FlutterView : NSView
+
+@property(readwrite, nonatomic, nonnull) NSOpenGLContext* openGLContext;
+@property(readonly, nonatomic) uint32_t frameBufferId;
 
 - (nullable instancetype)initWithFrame:(NSRect)frame
                           shareContext:(nonnull NSOpenGLContext*)shareContext
-                       reshapeListener:(nonnull id<FlutterViewReshapeListener>)reshapeListener
+                              delegate:(nonnull id<FlutterViewDelegate>)delegate
     NS_DESIGNATED_INITIALIZER;
 
 - (nullable instancetype)initWithShareContext:(nonnull NSOpenGLContext*)shareContext
-                              reshapeListener:
-                                  (nonnull id<FlutterViewReshapeListener>)reshapeListener;
+                                     delegate:(nonnull id<FlutterViewDelegate>)delegate;
 
 - (nullable instancetype)initWithFrame:(NSRect)frameRect
                            pixelFormat:(nullable NSOpenGLPixelFormat*)format NS_UNAVAILABLE;
 - (nonnull instancetype)initWithFrame:(NSRect)frameRect NS_UNAVAILABLE;
 - (nullable instancetype)initWithCoder:(nonnull NSCoder*)coder NS_UNAVAILABLE;
 - (nonnull instancetype)init NS_UNAVAILABLE;
 
+- (void)start;
+- (void)present;
+
 @end