Reverts "[engine] more consistently flush dart event loop, run vsync callback immediately (#56738)"

fml/task_runner.cc

@@ -52,7 +52,6 @@ bool TaskRunner::RunsTasksOnCurrentThread() {
                                                 loop_queue_id);
 }
 
-// static
 void TaskRunner::RunNowOrPostTask(const fml::RefPtr<fml::TaskRunner>& runner,
                                   const fml::closure& task) {
   FML_DCHECK(runner);
@@ -63,20 +62,4 @@ void TaskRunner::RunNowOrPostTask(const fml::RefPtr<fml::TaskRunner>& runner,
   }
 }
 
-// static
-void TaskRunner::RunNowAndFlushMessages(
-    const fml::RefPtr<fml::TaskRunner>& runner,
-    const fml::closure& task) {
-  FML_DCHECK(runner);
-  if (runner->RunsTasksOnCurrentThread()) {
-    task();
-    // Post an empty task to make the UI message loop run its task observers.
-    // The observers will execute any Dart microtasks queued by the platform
-    // message handler.
-    runner->PostTask([] {});
-  } else {
-    runner->PostTask(task);
-  }
-}
-
 }  // namespace fml

fml/task_runner.h

@@ -62,14 +62,6 @@ class TaskRunner : public fml::RefCountedThreadSafe<TaskRunner>,
   static void RunNowOrPostTask(const fml::RefPtr<fml::TaskRunner>& runner,
                                const fml::closure& task);
 
-  /// Like RunNowOrPostTask, except that if the task can be immediately
-  /// executed, an empty task will still be posted to the runner afterwards.
-  ///
-  /// This is used to ensure that messages posted to Dart from the platform
-  /// thread always flush the Dart event loop.
-  static void RunNowAndFlushMessages(const fml::RefPtr<fml::TaskRunner>& runner,
-                                     const fml::closure& task);
-
  protected:
   explicit TaskRunner(fml::RefPtr<MessageLoopImpl> loop);
 

shell/common/fixtures/shell_test.dart

@@ -640,13 +640,3 @@ void testSemanticsActions() {
     });
   };
 }
-
-@pragma('vm:entry-point')
-void testPointerActions() {
-  PlatformDispatcher.instance.onPointerDataPacket = (PointerDataPacket pointer) async {
-    await null;
-    Future<void>.value().then((_) {
-      notifyNative();
-    });
-  };
-}

shell/common/shell.cc

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "fml/task_runner.h"
 #define RAPIDJSON_HAS_STDSTRING 1
 #include "flutter/shell/common/shell.h"
 
@@ -1037,7 +1036,7 @@ void Shell::OnPlatformViewSetViewportMetrics(int64_t view_id,
         }
       });
 
-  fml::TaskRunner::RunNowAndFlushMessages(
+  fml::TaskRunner::RunNowOrPostTask(
       task_runners_.GetUITaskRunner(),
       [engine = engine_->GetWeakPtr(), view_id, metrics]() {
         if (engine) {
@@ -1076,16 +1075,24 @@ void Shell::OnPlatformViewDispatchPlatformMessage(
   }
 #endif  // FLUTTER_RUNTIME_MODE == FLUTTER_RUNTIME_MODE_DEBUG
 
-  // The static leak checker gets confused by the use of fml::MakeCopyable.
-  // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks)
-  fml::TaskRunner::RunNowAndFlushMessages(
-      task_runners_.GetUITaskRunner(),
-      fml::MakeCopyable([engine = engine_->GetWeakPtr(),
-                         message = std::move(message)]() mutable {
-        if (engine) {
-          engine->DispatchPlatformMessage(std::move(message));
-        }
-      }));
+  if (task_runners_.GetUITaskRunner()->RunsTasksOnCurrentThread()) {
+    engine_->DispatchPlatformMessage(std::move(message));
+
+    // Post an empty task to make the UI message loop run its task observers.
+    // The observers will execute any Dart microtasks queued by the platform
+    // message handler.
+    task_runners_.GetUITaskRunner()->PostTask([] {});
+  } else {
+    // The static leak checker gets confused by the use of fml::MakeCopyable.
+    // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks)
+    task_runners_.GetUITaskRunner()->PostTask(
+        fml::MakeCopyable([engine = engine_->GetWeakPtr(),
+                           message = std::move(message)]() mutable {
+          if (engine) {
+            engine->DispatchPlatformMessage(std::move(message));
+          }
+        }));
+  }
 }
 
 // |PlatformView::Delegate|
@@ -1097,7 +1104,7 @@ void Shell::OnPlatformViewDispatchPointerDataPacket(
   TRACE_FLOW_BEGIN("flutter", "PointerEvent", next_pointer_flow_id_);
   FML_DCHECK(is_set_up_);
   FML_DCHECK(task_runners_.GetPlatformTaskRunner()->RunsTasksOnCurrentThread());
-  fml::TaskRunner::RunNowAndFlushMessages(
+  fml::TaskRunner::RunNowOrPostTask(
       task_runners_.GetUITaskRunner(),
       fml::MakeCopyable([engine = weak_engine_, packet = std::move(packet),
                          flow_id = next_pointer_flow_id_]() mutable {
@@ -1115,8 +1122,7 @@ void Shell::OnPlatformViewDispatchSemanticsAction(int32_t node_id,
   FML_DCHECK(is_set_up_);
   FML_DCHECK(task_runners_.GetPlatformTaskRunner()->RunsTasksOnCurrentThread());
 
-  fml::TaskRunner::RunNowAndFlushMessages(
-      task_runners_.GetUITaskRunner(),
+  task_runners_.GetUITaskRunner()->PostTask(
       fml::MakeCopyable([engine = engine_->GetWeakPtr(), node_id, action,
                          args = std::move(args)]() mutable {
         if (engine) {
@@ -1130,26 +1136,25 @@ void Shell::OnPlatformViewSetSemanticsEnabled(bool enabled) {
   FML_DCHECK(is_set_up_);
   FML_DCHECK(task_runners_.GetPlatformTaskRunner()->RunsTasksOnCurrentThread());
 
-  fml::TaskRunner::RunNowAndFlushMessages(
-      task_runners_.GetUITaskRunner(),
-      [engine = engine_->GetWeakPtr(), enabled] {
-        if (engine) {
-          engine->SetSemanticsEnabled(enabled);
-        }
-      });
+  fml::TaskRunner::RunNowOrPostTask(task_runners_.GetUITaskRunner(),
+                                    [engine = engine_->GetWeakPtr(), enabled] {
+                                      if (engine) {
+                                        engine->SetSemanticsEnabled(enabled);
+                                      }
+                                    });
 }
 
 // |PlatformView::Delegate|
 void Shell::OnPlatformViewSetAccessibilityFeatures(int32_t flags) {
   FML_DCHECK(is_set_up_);
   FML_DCHECK(task_runners_.GetPlatformTaskRunner()->RunsTasksOnCurrentThread());
 
-  fml::TaskRunner::RunNowAndFlushMessages(
-      task_runners_.GetUITaskRunner(), [engine = engine_->GetWeakPtr(), flags] {
-        if (engine) {
-          engine->SetAccessibilityFeatures(flags);
-        }
-      });
+  fml::TaskRunner::RunNowOrPostTask(task_runners_.GetUITaskRunner(),
+                                    [engine = engine_->GetWeakPtr(), flags] {
+                                      if (engine) {
+                                        engine->SetAccessibilityFeatures(flags);
+                                      }
+                                    });
 }
 
 // |PlatformView::Delegate|

shell/common/shell_unittests.cc

@@ -4312,8 +4312,7 @@ TEST_F(ShellTest, NavigationMessageDispachedImmediately) {
   ASSERT_FALSE(DartVMRef::IsInstanceRunning());
 }
 
-// Verifies a semantics Action will flush the dart event loop.
-TEST_F(ShellTest, SemanticsActionsFlushMessageLoop) {
+TEST_F(ShellTest, SemanticsActionsPostTask) {
   Settings settings = CreateSettingsForFixture();
   ThreadHost thread_host("io.flutter.test." + GetCurrentTestName() + ".",
                          ThreadHost::Type::kPlatform);
@@ -4328,49 +4327,20 @@ TEST_F(ShellTest, SemanticsActionsFlushMessageLoop) {
   configuration.SetEntrypoint("testSemanticsActions");
 
   RunEngine(shell.get(), std::move(configuration));
-  fml::CountDownLatch latch(1);
-  AddNativeCallback(
-      // The Dart native function names aren't very consistent but this is
-      // just the native function name of the second vm entrypoint in the
-      // fixture.
-      "NotifyNative",
-      CREATE_NATIVE_ENTRY([&](auto args) { latch.CountDown(); }));
 
   task_runners.GetPlatformTaskRunner()->PostTask([&] {
     SendSemanticsAction(shell.get(), 0, SemanticsAction::kTap,
                         fml::MallocMapping(nullptr, 0));
   });
-  latch.Wait();
 
-  DestroyShell(std::move(shell), task_runners);
-  ASSERT_FALSE(DartVMRef::IsInstanceRunning());
-}
-
-// Verifies a pointer event will flush the dart event loop.
-TEST_F(ShellTest, PointerPacketFlushMessageLoop) {
-  Settings settings = CreateSettingsForFixture();
-  ThreadHost thread_host("io.flutter.test." + GetCurrentTestName() + ".",
-                         ThreadHost::Type::kPlatform);
-  auto task_runner = thread_host.platform_thread->GetTaskRunner();
-  TaskRunners task_runners("test", task_runner, task_runner, task_runner,
-                           task_runner);
-
-  EXPECT_EQ(task_runners.GetPlatformTaskRunner(),
-            task_runners.GetUITaskRunner());
-  auto shell = CreateShell(settings, task_runners);
-  auto configuration = RunConfiguration::InferFromSettings(settings);
-  configuration.SetEntrypoint("testPointerActions");
-
-  RunEngine(shell.get(), std::move(configuration));
+  // Fulfill native function for the second Shell's entrypoint.
   fml::CountDownLatch latch(1);
   AddNativeCallback(
       // The Dart native function names aren't very consistent but this is
       // just the native function name of the second vm entrypoint in the
       // fixture.
       "NotifyNative",
       CREATE_NATIVE_ENTRY([&](auto args) { latch.CountDown(); }));
-
-  DispatchFakePointerData(shell.get(), 23);
   latch.Wait();
 
   DestroyShell(std::move(shell), task_runners);

shell/common/vsync_waiter.cc

@@ -128,10 +128,7 @@ void VsyncWaiter::FireCallback(fml::TimePoint frame_start_time,
     fml::TaskQueueId ui_task_queue_id =
         task_runners_.GetUITaskRunner()->GetTaskQueueId();
 
-    // This task does not need to use RunNowAndFlushMessages as the
-    // vsync callback will explicitly flush the Dart event loop.
-    fml::TaskRunner::RunNowOrPostTask(
-        task_runners_.GetUITaskRunner(),
+    task_runners_.GetUITaskRunner()->PostTask(
         [ui_task_queue_id, callback, flow_identifier, frame_start_time,
          frame_target_time, pause_secondary_tasks]() {
           FML_TRACE_EVENT_WITH_FLOW_IDS(