Windows: Client Wrapper: Expose TaskRunner

ci/licenses_golden/licenses_flutter

@@ -1740,11 +1740,13 @@ FILE: ../../../flutter/shell/platform/windows/angle_surface_manager.h
 FILE: ../../../flutter/shell/platform/windows/client_wrapper/dart_project_unittests.cc
 FILE: ../../../flutter/shell/platform/windows/client_wrapper/flutter_engine.cc
 FILE: ../../../flutter/shell/platform/windows/client_wrapper/flutter_engine_unittests.cc
+FILE: ../../../flutter/shell/platform/windows/client_wrapper/flutter_task_runner_unittests.cc
 FILE: ../../../flutter/shell/platform/windows/client_wrapper/flutter_view_controller.cc
 FILE: ../../../flutter/shell/platform/windows/client_wrapper/flutter_view_controller_unittests.cc
 FILE: ../../../flutter/shell/platform/windows/client_wrapper/flutter_view_unittests.cc
 FILE: ../../../flutter/shell/platform/windows/client_wrapper/include/flutter/dart_project.h
 FILE: ../../../flutter/shell/platform/windows/client_wrapper/include/flutter/flutter_engine.h
+FILE: ../../../flutter/shell/platform/windows/client_wrapper/include/flutter/flutter_task_runner.h
 FILE: ../../../flutter/shell/platform/windows/client_wrapper/include/flutter/flutter_view.h
 FILE: ../../../flutter/shell/platform/windows/client_wrapper/include/flutter/flutter_view_controller.h
 FILE: ../../../flutter/shell/platform/windows/client_wrapper/include/flutter/plugin_registrar_windows.h

shell/platform/windows/client_wrapper/BUILD.gn

@@ -8,6 +8,7 @@ import("//flutter/testing/testing.gni")
 _wrapper_includes = [
   "include/flutter/dart_project.h",
   "include/flutter/flutter_engine.h",
+  "include/flutter/flutter_task_runner.h",
   "include/flutter/flutter_view_controller.h",
   "include/flutter/flutter_view.h",
   "include/flutter/plugin_registrar_windows.h",
@@ -76,6 +77,7 @@ executable("client_wrapper_windows_unittests") {
   sources = [
     "dart_project_unittests.cc",
     "flutter_engine_unittests.cc",
+    "flutter_task_runner_unittests.cc",
     "flutter_view_controller_unittests.cc",
     "flutter_view_unittests.cc",
     "plugin_registrar_windows_unittests.cc",

shell/platform/windows/client_wrapper/flutter_task_runner_unittests.cc

@@ -0,0 +1,79 @@
+// 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.
+
+#include <memory>
+#include <string>
+
+#include "flutter/shell/platform/windows/client_wrapper/include/flutter/flutter_task_runner.h"
+#include "flutter/shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.h"
+#include "gtest/gtest.h"
+
+namespace flutter {
+namespace {
+
+// Stub implementation to validate calls to the API.
+class TestWindowsApi : public testing::StubFlutterWindowsApi {
+ public:
+  TestWindowsApi(bool runs_tasks_on_current_thread)
+      : runs_tasks_on_current_thread_(runs_tasks_on_current_thread) {}
+
+  void TaskRunnerPostTask(VoidCallback callback, void* user_data) override {
+    post_task_called_ = true;
+    callback(user_data);
+  }
+
+  bool TaskRunnerRunsTasksOnCurrentThread() override {
+    return runs_tasks_on_current_thread_;
+  }
+
+  bool post_task_called() { return post_task_called_; }
+
+ private:
+  bool runs_tasks_on_current_thread_;
+  bool post_task_called_ = false;
+};
+
+}  // namespace
+
+TEST(FlutterTaskRunnerTest, RunsTasksOnCurrentThreadPassesThrough) {
+  testing::ScopedStubFlutterWindowsApi scoped_api_stub(
+      std::make_unique<TestWindowsApi>(false));
+  auto test_api = static_cast<TestWindowsApi*>(scoped_api_stub.stub());
+  FlutterTaskRunner task_runner(
+      reinterpret_cast<FlutterDesktopTaskRunnerRef>(2));
+
+  EXPECT_FALSE(task_runner.RunsTasksOnCurrentThread());
+}
+
+TEST(FlutterTaskRunnerTest, PostTaskInline) {
+  testing::ScopedStubFlutterWindowsApi scoped_api_stub(
+      std::make_unique<TestWindowsApi>(true));
+  auto test_api = static_cast<TestWindowsApi*>(scoped_api_stub.stub());
+  FlutterTaskRunner task_runner(
+      reinterpret_cast<FlutterDesktopTaskRunnerRef>(2));
+
+  bool task_executed = false;
+  task_runner.PostTask([&task_executed]() { task_executed = true; });
+
+  EXPECT_TRUE(task_runner.RunsTasksOnCurrentThread());
+  EXPECT_TRUE(task_executed);
+  EXPECT_FALSE(test_api->post_task_called());
+}
+
+TEST(FlutterTaskRunnerTest, PostTaskFromOtherThread) {
+  testing::ScopedStubFlutterWindowsApi scoped_api_stub(
+      std::make_unique<TestWindowsApi>(false));
+  auto test_api = static_cast<TestWindowsApi*>(scoped_api_stub.stub());
+  FlutterTaskRunner task_runner(
+      reinterpret_cast<FlutterDesktopTaskRunnerRef>(2));
+
+  bool task_executed = false;
+  task_runner.PostTask([&task_executed]() { task_executed = true; });
+
+  EXPECT_FALSE(task_runner.RunsTasksOnCurrentThread());
+  EXPECT_TRUE(task_executed);
+  EXPECT_TRUE(test_api->post_task_called());
+}
+
+}  // namespace flutter

shell/platform/windows/client_wrapper/flutter_view_unittests.cc

@@ -28,4 +28,12 @@ TEST(FlutterViewTest, HwndAccessPassesThrough) {
   EXPECT_EQ(view.GetNativeWindow(), reinterpret_cast<HWND>(7));
 }
 
+TEST(FlutterViewTest, GetPlatformTaskRunner) {
+  testing::ScopedStubFlutterWindowsApi scoped_api_stub(
+      std::make_unique<TestWindowsApi>());
+  auto test_api = static_cast<TestWindowsApi*>(scoped_api_stub.stub());
+  FlutterView view(reinterpret_cast<FlutterDesktopViewRef>(2));
+  EXPECT_NE(view.GetPlatformTaskRunner(), nullptr);
+}
+
 }  // namespace flutter

shell/platform/windows/client_wrapper/include/flutter/flutter_task_runner.h

@@ -0,0 +1,55 @@
+// 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_WINDOWS_CLIENT_WRAPPER_INCLUDE_FLUTTER_TASK_RUNNER_H_
+#define FLUTTER_SHELL_PLATFORM_WINDOWS_CLIENT_WRAPPER_INCLUDE_FLUTTER_TASK_RUNNER_H_
+
+#include <flutter_windows.h>
+
+#include <functional>
+
+namespace flutter {
+
+// An interface for scheduling tasks on the associated thread.
+class FlutterTaskRunner {
+ public:
+  typedef std::function<void()> VoidCallback;
+  explicit FlutterTaskRunner(FlutterDesktopTaskRunnerRef task_runner)
+      : task_runner_(task_runner) {}
+
+  // Schedules the task for execution by the associated thread.
+  void PostTask(VoidCallback callback) {
+    if (RunsTasksOnCurrentThread()) {
+      callback();
+      return;
+    }
+
+    struct Captures {
+      VoidCallback callback;
+    };
+    auto captures = new Captures();
+    captures->callback = callback;
+    FlutterDesktopTaskRunnerPostTask(
+        task_runner_,
+        [](void* opaque) {
+          auto captures = reinterpret_cast<Captures*>(opaque);
+          captures->callback();
+          delete captures;
+        },
+        captures);
+  }
+
+  // Returns `true` if the associated thread is the current thread.
+  bool RunsTasksOnCurrentThread() {
+    return FlutterDesktopTaskRunnerRunsTasksOnCurrentThread(task_runner_);
+  }
+
+ private:
+  // Handle for interacting with the C API's task runner.
+  FlutterDesktopTaskRunnerRef task_runner_;
+};
+
+}  // namespace flutter
+
+#endif  // FLUTTER_SHELL_PLATFORM_WINDOWS_CLIENT_WRAPPER_INCLUDE_FLUTTER_TASK_RUNNER_H_

shell/platform/windows/client_wrapper/include/flutter/flutter_view.h

@@ -7,12 +7,17 @@
 
 #include <flutter_windows.h>
 
+#include "flutter_task_runner.h"
+
 namespace flutter {
 
 // A view displaying Flutter content.
 class FlutterView {
  public:
-  explicit FlutterView(FlutterDesktopViewRef view) : view_(view) {}
+  explicit FlutterView(FlutterDesktopViewRef view)
+      : view_(view),
+        platform_task_runner_(std::make_unique<FlutterTaskRunner>(
+            FlutterDesktopViewGetTaskRunner(view))) {}
 
   virtual ~FlutterView() = default;
 
@@ -30,9 +35,17 @@ class FlutterView {
   HWND GetNativeWindow() { return FlutterDesktopViewGetHWND(view_); }
 #endif
 
+  // Gets the platform task runner.
+  FlutterTaskRunner* GetPlatformTaskRunner() {
+    return platform_task_runner_.get();
+  }
+
  private:
   // Handle for interacting with the C API's view.
   FlutterDesktopViewRef view_ = nullptr;
+
+  // The task runner for this view.
+  std::unique_ptr<FlutterTaskRunner> platform_task_runner_;
 };
 
 }  // namespace flutter

shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.cc

@@ -150,6 +150,28 @@ HWND FlutterDesktopViewGetHWND(FlutterDesktopViewRef controller) {
   return reinterpret_cast<HWND>(-1);
 }
 
+FlutterDesktopTaskRunnerRef FlutterDesktopViewGetTaskRunner(
+    FlutterDesktopViewRef view) {
+  // The stub ignores this, so just return an arbitrary non-zero value.
+  return reinterpret_cast<FlutterDesktopTaskRunnerRef>(1);
+}
+
+void FlutterDesktopTaskRunnerPostTask(FlutterDesktopTaskRunnerRef task_runner,
+                                      VoidCallback callback,
+                                      void* user_data) {
+  if (s_stub_implementation) {
+    return s_stub_implementation->TaskRunnerPostTask(callback, user_data);
+  }
+}
+
+bool FlutterDesktopTaskRunnerRunsTasksOnCurrentThread(
+    FlutterDesktopTaskRunnerRef task_runner) {
+  if (s_stub_implementation) {
+    return s_stub_implementation->TaskRunnerRunsTasksOnCurrentThread();
+  }
+  return true;
+}
+
 FlutterDesktopViewRef FlutterDesktopPluginRegistrarGetView(
     FlutterDesktopPluginRegistrarRef controller) {
   // The stub ignores this, so just return an arbitrary non-zero value.

shell/platform/windows/client_wrapper/testing/stub_flutter_windows_api.h

@@ -71,6 +71,17 @@ class StubFlutterWindowsApi {
   // Called for FlutterDesktopViewGetHWND.
   virtual HWND ViewGetHWND() { return reinterpret_cast<HWND>(1); }
 
+  // Called for FlutterDesktopViewGetTaskRunner.
+  virtual FlutterDesktopTaskRunnerRef ViewGetTaskRunner() {
+    return reinterpret_cast<FlutterDesktopTaskRunnerRef>(1);
+  }
+
+  // Called for FlutterDesktopTaskRunnerPostTask.
+  virtual void TaskRunnerPostTask(VoidCallback callback, void* user_data) {}
+
+  // Called for FlutterDesktopTaskRunnerRunsTasksOnCurrentThread.
+  virtual bool TaskRunnerRunsTasksOnCurrentThread() { return true; }
+
   // Called for FlutterDesktopPluginRegistrarRegisterTopLevelWindowProcDelegate.
   virtual void PluginRegistrarRegisterTopLevelWindowProcDelegate(
       FlutterDesktopWindowProcCallback delegate,

shell/platform/windows/flutter_windows.cc

@@ -61,6 +61,18 @@ static FlutterDesktopTextureRegistrarRef HandleForTextureRegistrar(
   return reinterpret_cast<FlutterDesktopTextureRegistrarRef>(registrar);
 }
 
+// Returns the task runner corresponding to the given opaque API handle.
+static flutter::TaskRunner* TaskRunnerFromHandle(
+    FlutterDesktopTaskRunnerRef ref) {
+  return reinterpret_cast<flutter::TaskRunner*>(ref);
+}
+
+// Returns the opaque API handle for the given task runner instance.
+static FlutterDesktopTaskRunnerRef HandleForTaskRunner(
+    flutter::TaskRunner* task_runner) {
+  return reinterpret_cast<FlutterDesktopTaskRunnerRef>(task_runner);
+}
+
 void FlutterDesktopViewControllerDestroy(
     FlutterDesktopViewControllerRef controller) {
   delete controller;
@@ -148,11 +160,28 @@ HWND FlutterDesktopViewGetHWND(FlutterDesktopViewRef view) {
 }
 #endif
 
+FlutterDesktopTaskRunnerRef FlutterDesktopViewGetTaskRunner(
+    FlutterDesktopViewRef view) {
+  return HandleForTaskRunner(ViewFromHandle(view)->GetEngine()->task_runner());
+}
+
 FlutterDesktopViewRef FlutterDesktopPluginRegistrarGetView(
     FlutterDesktopPluginRegistrarRef registrar) {
   return HandleForView(registrar->engine->view());
 }
 
+void FlutterDesktopTaskRunnerPostTask(FlutterDesktopTaskRunnerRef task_runner,
+                                      VoidCallback callback,
+                                      void* user_data) {
+  return TaskRunnerFromHandle(task_runner)
+      ->RunNowOrPostTask([user_data, callback]() { callback(user_data); });
+}
+
+bool FlutterDesktopTaskRunnerRunsTasksOnCurrentThread(
+    FlutterDesktopTaskRunnerRef task_runner) {
+  return TaskRunnerFromHandle(task_runner)->RunsTasksOnCurrentThread();
+}
+
 void FlutterDesktopResyncOutputStreams() {
   FILE* unused;
   if (freopen_s(&unused, "CONOUT$", "w", stdout)) {

shell/platform/windows/public/flutter_windows.h

@@ -34,6 +34,10 @@ typedef struct FlutterDesktopView* FlutterDesktopViewRef;
 struct FlutterDesktopEngine;
 typedef struct FlutterDesktopEngine* FlutterDesktopEngineRef;
 
+// Opaque reference to a Flutter platform task runner.
+struct FlutterDesktopTaskRunner;
+typedef struct FlutterDesktopTaskRunner* FlutterDesktopTaskRunnerRef;
+
 // Properties for configuring a Flutter engine instance.
 typedef struct {
   // The path to the flutter_assets folder for the application to be run.
@@ -105,8 +109,8 @@ FLUTTER_EXPORT void FlutterDesktopViewControllerDestroy(
 // Its lifetime is the same as the |controller|'s.
 FLUTTER_EXPORT FlutterDesktopEngineRef FlutterDesktopViewControllerGetEngine(
     FlutterDesktopViewControllerRef controller);
-// Returns the view managed by the given controller.
 
+// Returns the view managed by the given controller.
 FLUTTER_EXPORT FlutterDesktopViewRef
 FlutterDesktopViewControllerGetView(FlutterDesktopViewControllerRef controller);
 
@@ -205,6 +209,24 @@ FlutterDesktopViewGetCoreApplicationView(FlutterDesktopViewRef view);
 FLUTTER_EXPORT HWND FlutterDesktopViewGetHWND(FlutterDesktopViewRef view);
 #endif
 
+// Returns the task runner associated with the view.
+FLUTTER_EXPORT FlutterDesktopTaskRunnerRef
+FlutterDesktopViewGetTaskRunner(FlutterDesktopViewRef view);
+
+// ========== Task Runner ==========
+typedef void (*VoidCallback)(void* user_data);
+
+// Posts a task to the runner.
+FLUTTER_EXPORT void FlutterDesktopTaskRunnerPostTask(
+    FlutterDesktopTaskRunnerRef task_runner,
+    VoidCallback callback,
+    void* user_data);
+
+// Gets a flag indicating whether the task runner executes tasks on the current
+// thread.
+FLUTTER_EXPORT bool FlutterDesktopTaskRunnerRunsTasksOnCurrentThread(
+    FlutterDesktopTaskRunnerRef task_runner);
+
 // ========== Plugin Registrar (extensions) ==========
 // These are Windows-specific extensions to flutter_plugin_registrar.h