[WIP] Allow running macOS embedder with UI and platform thread merged

ci/licenses_golden/licenses_flutter

@@ -43720,9 +43720,9 @@ ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterTex
 ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterTextInputSemanticsObjectTest.mm + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterTextureRegistrar.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterTextureRegistrar.mm + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterThreadSynchronizer.h + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterThreadSynchronizer.mm + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterThreadSynchronizerTest.mm + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterResizeSynchronizer.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterResizeSynchronizer.mm + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterResizeSynchronizerTest.mm + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterTimeConverter.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterTimeConverter.mm + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/macos/framework/Source/FlutterUmbrellaImportTests.m + ../../../flutter/LICENSE

lib/ui/ui_dart_state.cc

@@ -22,6 +22,16 @@ extern void syslog(int, const char*, ...);
 }
 #endif
 
+namespace {
+static std::set<flutter::UIDartState*> state;
+}
+
+void UglyHackFlushMicrotasks() {
+  for (auto s : state) {
+    s->FlushMicrotasksNow();
+  }
+}
+
 using tonic::ToDart;
 
 namespace flutter {
@@ -73,10 +83,12 @@ UIDartState::UIDartState(
       isolate_name_server_(std::move(isolate_name_server)),
       context_(context) {
   AddOrRemoveTaskObserver(true /* add */);
+  state.insert(this);
 }
 
 UIDartState::~UIDartState() {
   AddOrRemoveTaskObserver(false /* remove */);
+  state.erase(this);
 }
 
 const std::string& UIDartState::GetAdvisoryScriptURI() const {

runtime/dart_isolate.cc

@@ -509,7 +509,7 @@ bool DartIsolate::Initialize(Dart_Isolate dart_isolate) {
     SetMessageHandlingTaskRunner(GetTaskRunners().GetPlatformTaskRunner(),
                                  true);
   } else {
-    SetMessageHandlingTaskRunner(GetTaskRunners().GetUITaskRunner(), false);
+    SetMessageHandlingTaskRunner(GetTaskRunners().GetUITaskRunner(), true);
   }
 
   if (tonic::CheckAndHandleError(

shell/platform/darwin/macos/BUILD.gn

@@ -91,6 +91,10 @@ source_set("flutter_framework_source") {
     "framework/Source/FlutterPlatformViewController.mm",
     "framework/Source/FlutterRenderer.h",
     "framework/Source/FlutterRenderer.mm",
+    "framework/Source/FlutterResizeSynchronizer.h",
+    "framework/Source/FlutterResizeSynchronizer.mm",
+    "framework/Source/FlutterRunLoop.h",
+    "framework/Source/FlutterRunLoop.mm",
     "framework/Source/FlutterSurface.h",
     "framework/Source/FlutterSurface.mm",
     "framework/Source/FlutterSurfaceManager.h",
@@ -101,8 +105,6 @@ source_set("flutter_framework_source") {
     "framework/Source/FlutterTextInputSemanticsObject.mm",
     "framework/Source/FlutterTextureRegistrar.h",
     "framework/Source/FlutterTextureRegistrar.mm",
-    "framework/Source/FlutterThreadSynchronizer.h",
-    "framework/Source/FlutterThreadSynchronizer.mm",
     "framework/Source/FlutterTimeConverter.h",
     "framework/Source/FlutterTimeConverter.mm",
     "framework/Source/FlutterVSyncWaiter.h",
@@ -190,10 +192,10 @@ executable("flutter_desktop_darwin_unittests") {
     "framework/Source/FlutterMutatorViewTest.mm",
     "framework/Source/FlutterPlatformNodeDelegateMacTest.mm",
     "framework/Source/FlutterPlatformViewControllerTest.mm",
+    "framework/Source/FlutterResizeSynchronizerTest.mm",
     "framework/Source/FlutterSurfaceManagerTest.mm",
     "framework/Source/FlutterTextInputPluginTest.mm",
     "framework/Source/FlutterTextInputSemanticsObjectTest.mm",
-    "framework/Source/FlutterThreadSynchronizerTest.mm",
     "framework/Source/FlutterVSyncWaiterTest.mm",
     "framework/Source/FlutterViewControllerTest.mm",
     "framework/Source/FlutterViewControllerTestUtils.h",

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

@@ -24,6 +24,7 @@
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterMouseCursorPlugin.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformViewController.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterRenderer.h"
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterRunLoop.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterTimeConverter.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterVSyncWaiter.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h"
@@ -37,6 +38,8 @@
 
 using flutter::kFlutterImplicitViewId;
 
+extern void UglyHackFlushMicrotasks();
+
 /**
  * Constructs and returns a FlutterLocale struct corresponding to |locale|, which must outlive
  * the returned struct.
@@ -455,8 +458,6 @@ @implementation FlutterEngine {
   // A method channel for miscellaneous platform functionality.
   FlutterMethodChannel* _platformChannel;
 
-  FlutterThreadSynchronizer* _threadSynchronizer;
-
   // Whether the application is currently the active application.
   BOOL _active;
 
@@ -499,6 +500,9 @@ - (instancetype)initWithName:(NSString*)labelPrefix
       allowHeadlessExecution:(BOOL)allowHeadlessExecution {
   self = [super init];
   NSAssert(self, @"Super init cannot be nil");
+
+  [FlutterRunLoop ensureMainLoopInitialized];
+
   _pasteboard = [[FlutterPasteboard alloc] init];
   _active = NO;
   _visible = NO;
@@ -527,7 +531,6 @@ - (instancetype)initWithName:(NSString*)labelPrefix
                            object:nil];
 
   _platformViewController = [[FlutterPlatformViewController alloc] init];
-  _threadSynchronizer = [[FlutterThreadSynchronizer alloc] init];
   [self setUpPlatformViewChannel];
   [self setUpAccessibilityChannel];
   [self setUpNotificationCenterListeners];
@@ -653,7 +656,8 @@ - (BOOL)runWithEntrypoint:(NSString*)entrypoint {
   const FlutterCustomTaskRunners custom_task_runners = {
       .struct_size = sizeof(FlutterCustomTaskRunners),
       .platform_task_runner = &cocoa_task_runner_description,
-      .thread_priority_setter = SetThreadPriority};
+      .thread_priority_setter = SetThreadPriority,
+      .merged_ui_thread = 1};
   flutterArguments.custom_task_runners = &custom_task_runners;
 
   [self loadAOTData:_project.assetsPath];
@@ -739,9 +743,7 @@ - (void)registerViewController:(FlutterViewController*)controller
   NSAssert([_viewControllers objectForKey:@(viewIdentifier)] == nil,
            @"The requested view ID is occupied.");
   [_viewControllers setObject:controller forKey:@(viewIdentifier)];
-  [controller setUpWithEngine:self
-               viewIdentifier:viewIdentifier
-           threadSynchronizer:_threadSynchronizer];
+  [controller setUpWithEngine:self viewIdentifier:viewIdentifier];
   NSAssert(controller.viewIdentifier == viewIdentifier, @"Failed to assign view ID.");
   // Verify that the controller's property are updated accordingly. Failing the
   // assertions is likely because either the FlutterViewController or the
@@ -769,13 +771,7 @@ - (void)viewControllerViewDidLoad:(FlutterViewController*)viewController {
                           [timeConverter CAMediaTimeToEngineTime:targetTimestamp];
                       FlutterEngine* engine = weakSelf;
                       if (engine) {
-                        // It is a bit unfortunate that embedder requires OnVSync call on
-                        // platform thread just to immediately redispatch it to UI thread.
-                        // We are already on UI thread right now, but have to do the
-                        // extra hop to main thread.
-                        [engine->_threadSynchronizer performOnPlatformThread:^{
-                          engine->_embedderAPI.OnVsync(_engine, baton, timeNanos, targetTimeNanos);
-                        }];
+                        engine->_embedderAPI.OnVsync(_engine, baton, timeNanos, targetTimeNanos);
                       }
                     }];
   FML_DCHECK([_vsyncWaiters objectForKey:@(viewController.viewIdentifier)] == nil);
@@ -1132,9 +1128,6 @@ - (void)shutDownEngine {
     return;
   }
 
-  [_threadSynchronizer shutdown];
-  _threadSynchronizer = nil;
-
   FlutterEngineResult result = _embedderAPI.Deinitialize(_engine);
   if (result != kSuccess) {
     NSLog(@"Could not de-initialize the Flutter engine: error %d", result);
@@ -1331,10 +1324,6 @@ - (BOOL)clipboardHasStrings {
   return flutter::GetSwitchesFromEnvironment();
 }
 
-- (FlutterThreadSynchronizer*)testThreadSynchronizer {
-  return _threadSynchronizer;
-}
-
 #pragma mark - FlutterAppLifecycleDelegate
 
 - (void)setApplicationState:(flutter::AppLifecycleState)state {
@@ -1518,29 +1507,23 @@ - (BOOL)unregisterTextureWithID:(int64_t)textureID {
 
 #pragma mark - Task runner integration
 
-- (void)runTaskOnEmbedder:(FlutterTask)task {
-  if (_engine) {
-    auto result = _embedderAPI.RunTask(_engine, &task);
-    if (result != kSuccess) {
-      NSLog(@"Could not post a task to the Flutter engine.");
-    }
-  }
-}
-
 - (void)postMainThreadTask:(FlutterTask)task targetTimeInNanoseconds:(uint64_t)targetTime {
   __weak FlutterEngine* weakSelf = self;
-  auto worker = ^{
-    [weakSelf runTaskOnEmbedder:task];
-  };
 
   const auto engine_time = _embedderAPI.GetCurrentTime();
-  if (targetTime <= engine_time) {
-    dispatch_async(dispatch_get_main_queue(), worker);
 
-  } else {
-    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, targetTime - engine_time),
-                   dispatch_get_main_queue(), worker);
-  }
+  [FlutterRunLoop.mainRunLoop
+      performBlock:^{
+        FlutterEngine* self = weakSelf;
+        if (_engine) {
+          auto result = _embedderAPI.RunTask(_engine, &task);
+          if (result != kSuccess) {
+            NSLog(@"Could not post a task to the Flutter engine.");
+          }
+        }
+        UglyHackFlushMicrotasks();
+      }
+        afterDelay:(targetTime - (double)engine_time) / 1000000000.0];
 }
 
 // Getter used by test harness, only exposed through the FlutterEngine(Test) category

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

@@ -33,8 +33,6 @@
 // CREATE_NATIVE_ENTRY and MOCK_ENGINE_PROC are leaky by design
 // NOLINTBEGIN(clang-analyzer-core.StackAddressEscape)
 
-constexpr int64_t kImplicitViewId = 0ll;
-
 @interface FlutterEngine (Test)
 /**
  * The FlutterCompositor object currently in use by the FlutterEngine.
@@ -526,7 +524,7 @@ @implementation MockableFlutterEngine
                 result:^(id result){
                 }];
 
-  [engine.testThreadSynchronizer blockUntilFrameAvailable];
+  // [engine.testThreadSynchronizer blockUntilFrameAvailable];
 
   CALayer* rootLayer = viewController.flutterView.layer;
 
@@ -863,20 +861,6 @@ @implementation MockableFlutterEngine
   }
 }
 
-TEST_F(FlutterEngineTest, ThreadSynchronizerNotBlockingRasterThreadAfterShutdown) {
-  FlutterThreadSynchronizer* threadSynchronizer = [[FlutterThreadSynchronizer alloc] init];
-  [threadSynchronizer shutdown];
-
-  std::thread rasterThread([&threadSynchronizer] {
-    [threadSynchronizer performCommitForView:kImplicitViewId
-                                        size:CGSizeMake(100, 100)
-                                      notify:^{
-                                      }];
-  });
-
-  rasterThread.join();
-}
-
 TEST_F(FlutterEngineTest, ManageControllersIfInitiatedByController) {
   NSString* fixtures = @(flutter::testing::GetFixturesPath());
   FlutterDartProject* project = [[FlutterDartProject alloc]

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

@@ -224,10 +224,6 @@ typedef NS_ENUM(NSInteger, FlutterAppExitResponse) {
 - (NSArray<NSScreen*>*)screens;
 @end
 
-@interface FlutterEngine (Tests)
-- (nonnull FlutterThreadSynchronizer*)testThreadSynchronizer;
-@end
-
 NS_ASSUME_NONNULL_END
 
 #endif  // FLUTTER_SHELL_PLATFORM_DARWIN_MACOS_FRAMEWORK_SOURCE_FLUTTERENGINE_INTERNAL_H_

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

@@ -0,0 +1,40 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_SHELL_PLATFORM_DARWIN_MACOS_FRAMEWORK_SOURCE_FLUTTERRESIZESYNCHRONIZER_H_
+#define FLUTTER_SHELL_PLATFORM_DARWIN_MACOS_FRAMEWORK_SOURCE_FLUTTERRESIZESYNCHRONIZER_H_
+
+#import <Cocoa/Cocoa.h>
+
+#import "flutter/shell/platform/darwin/macos/framework/Headers/FlutterViewController.h"
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterRunLoop.h"
+
+@interface FlutterResizeSynchronizer : NSObject
+
+/**
+ * Begins a resize operation for the given size. Block the thread until
+ * performCommitForSize: with the same size is called.
+ * While the thread is blocked Flutter messages are being pumped.
+ * See [FlutterRunLoop pollOnce].
+ */
+- (void)beginResizeForSize:(CGSize)size notify:(nonnull dispatch_block_t)notify;
+
+/**
+ * Called from raster thread. Schedules the given block on platform thread
+ * at given delay and unblocks the platform thread if waiting for the surface
+ * during resize.
+ */
+- (void)performCommitForSize:(CGSize)size
+                      notify:(nonnull dispatch_block_t)notify
+                       delay:(NSTimeInterval)delay;
+
+/**
+ * Called when the view is shut down. Unblocks platform thread if blocked
+ * during resize.
+ */
+- (void)shutDown;
+
+@end
+
+#endif  // FLUTTER_SHELL_PLATFORM_DARWIN_MACOS_FRAMEWORK_SOURCE_FLUTTERRESIZESYNCHRONIZER_H_

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

@@ -0,0 +1,60 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterResizeSynchronizer.h"
+
+#import "flutter/fml/logging.h"
+
+@implementation FlutterResizeSynchronizer {
+  std::atomic_bool _inResize;
+  bool _shuttingDown;
+  bool _hasFrame;
+  CGSize _contentSize;
+}
+
+- (void)beginResizeForSize:(CGSize)size notify:(nonnull dispatch_block_t)notify {
+  if (!_hasFrame || _shuttingDown) {
+    notify();
+    return;
+  }
+
+  _inResize = true;
+  _contentSize = CGSizeMake(-1, -1);
+  notify();
+  CFAbsoluteTime start = CFAbsoluteTimeGetCurrent();
+  while (true) {
+    if (CGSizeEqualToSize(_contentSize, size) || _shuttingDown) {
+      break;
+    }
+    if (CFAbsoluteTimeGetCurrent() - start > 1.0) {
+      FML_LOG(ERROR) << "Resize timed out.";
+      break;
+    }
+    [FlutterRunLoop.mainRunLoop pollOnce];
+  }
+  _inResize = false;
+}
+
+- (void)performCommitForSize:(CGSize)size
+                      notify:(nonnull dispatch_block_t)notify
+                       delay:(NSTimeInterval)delay {
+  if (_inResize) {
+    delay = 0;
+  }
+  [FlutterRunLoop.mainRunLoop
+      performBlock:^{
+        _hasFrame = YES;
+        _contentSize = size;
+        notify();
+      }
+        afterDelay:delay];
+}
+
+- (void)shutDown {
+  [FlutterRunLoop.mainRunLoop performBlock:^{
+    _shuttingDown = YES;
+  }];
+}
+
+@end

shell/platform/darwin/macos/framework/Source/FlutterThreadSynchronizerTest.mm → shell/platform/darwin/macos/framework/Source/FlutterResizeSynchronizerTest.mm

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#if 0
+
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterThreadSynchronizer.h"
 
 #import "flutter/fml/synchronization/waitable_event.h"
@@ -374,3 +376,5 @@ - (void)joinRender {
   [scaffold joinMain];
   EXPECT_FALSE([synchronizer isWaitingWhenMutexIsAvailable]);
 }
+
+#endif