[Windows] Move DWM composition status to Windows proc table for mocking (flutter/engine#49397)

The `FlutterWindowsView` needs the `DwmIsCompositionEnabled` win32 API to check whether it should block presents until the v-blank to prevent screen tearing.

Currently, the view used the `FlutterWindow` to allow mocking this win32 API. However, the window is a complex type with lots of other responsibilities. The `WindowsProcTable` is the new preferred type for mocking win32 API.

Part of https://github.com/flutter/flutter/issues/140626

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

engine/src/flutter/shell/platform/windows/flutter_window.cc

@@ -372,18 +372,6 @@ ui::AXPlatformNodeWin* FlutterWindow::GetAlert() {
   return alert_node_.get();
 }
 
-bool FlutterWindow::NeedsVSync() const {
-  // If the Desktop Window Manager composition is enabled,
-  // the system itself synchronizes with v-sync.
-  // See: https://learn.microsoft.com/windows/win32/dwm/composition-ovw
-  BOOL composition_enabled;
-  if (SUCCEEDED(::DwmIsCompositionEnabled(&composition_enabled))) {
-    return !composition_enabled;
-  }
-
-  return true;
-}
-
 void FlutterWindow::OnWindowStateEvent(WindowStateEvent event) {
   switch (event) {
     case WindowStateEvent::kShow:

engine/src/flutter/shell/platform/windows/flutter_window.h

@@ -193,9 +193,6 @@ class FlutterWindow : public KeyboardManager::WindowDelegate,
   // |WindowBindingHandler|
   virtual ui::AXPlatformNodeWin* GetAlert() override;
 
-  // |WindowBindingHandler|
-  virtual bool NeedsVSync() const override;
-
   // Called to obtain a pointer to the fragment root delegate.
   virtual ui::AXFragmentRootDelegateWin* GetAxFragmentRootDelegate();
 

engine/src/flutter/shell/platform/windows/flutter_windows.cc

@@ -82,8 +82,8 @@ FlutterDesktopViewControllerRef FlutterDesktopViewControllerCreate(
           width, height, engine_ptr->windows_proc_table());
 
   auto engine = std::unique_ptr<flutter::FlutterWindowsEngine>(engine_ptr);
-  auto view =
-      std::make_unique<flutter::FlutterWindowsView>(std::move(window_wrapper));
+  auto view = std::make_unique<flutter::FlutterWindowsView>(
+      std::move(window_wrapper), engine_ptr->windows_proc_table());
   auto controller = std::make_unique<flutter::FlutterWindowsViewController>(
       std::move(engine), std::move(view));
 

engine/src/flutter/shell/platform/windows/flutter_windows_view.cc

@@ -40,8 +40,7 @@ bool SurfaceWillUpdate(size_t cur_width,
 
 /// Update the surface's swap interval to block until the v-blank iff
 /// the system compositor is disabled.
-void UpdateVsync(const FlutterWindowsEngine& engine,
-                 const WindowBindingHandler& window) {
+void UpdateVsync(const FlutterWindowsEngine& engine, bool needs_vsync) {
   AngleSurfaceManager* surface_manager = engine.surface_manager();
   if (!surface_manager) {
     return;
@@ -52,7 +51,6 @@ void UpdateVsync(const FlutterWindowsEngine& engine,
   // the raster thread. If the engine is initializing, the raster thread doesn't
   // exist yet and the render surface can be made current on the platform
   // thread.
-  auto needs_vsync = window.NeedsVSync();
   if (engine.running()) {
     engine.PostRasterThreadTask([surface_manager, needs_vsync]() {
       surface_manager->SetVSyncEnabled(needs_vsync);
@@ -72,7 +70,13 @@ void UpdateVsync(const FlutterWindowsEngine& engine,
 }  // namespace
 
 FlutterWindowsView::FlutterWindowsView(
-    std::unique_ptr<WindowBindingHandler> window_binding) {
+    std::unique_ptr<WindowBindingHandler> window_binding,
+    std::shared_ptr<WindowsProcTable> windows_proc_table)
+    : windows_proc_table_(std::move(windows_proc_table)) {
+  if (windows_proc_table_ == nullptr) {
+    windows_proc_table_ = std::make_shared<WindowsProcTable>();
+  }
+
   // Take the binding handler, and give it a pointer back to self.
   binding_handler_ = std::move(window_binding);
   binding_handler_->SetView(this);
@@ -114,7 +118,7 @@ void FlutterWindowsView::OnEmptyFrameGenerated() {
   // resize_status_ is set to kDone.
   engine_->surface_manager()->ResizeSurface(
       GetWindowHandle(), resize_target_width_, resize_target_height_,
-      binding_handler_->NeedsVSync());
+      NeedsVsync());
   resize_status_ = ResizeState::kFrameGenerated;
 }
 
@@ -130,7 +134,7 @@ bool FlutterWindowsView::OnFrameGenerated(size_t width, size_t height) {
     // Platform thread is blocked for the entire duration until the
     // resize_status_ is set to kDone.
     engine_->surface_manager()->ResizeSurface(GetWindowHandle(), width, height,
-                                              binding_handler_->NeedsVSync());
+                                              NeedsVsync());
     resize_status_ = ResizeState::kFrameGenerated;
     return true;
   }
@@ -638,7 +642,7 @@ void FlutterWindowsView::CreateRenderSurface() {
     engine_->surface_manager()->CreateSurface(GetWindowHandle(), bounds.width,
                                               bounds.height);
 
-    UpdateVsync(*engine_, *binding_handler_);
+    UpdateVsync(*engine_, NeedsVsync());
 
     resize_target_width_ = bounds.width;
     resize_target_height_ = bounds.height;
@@ -706,7 +710,7 @@ void FlutterWindowsView::UpdateSemanticsEnabled(bool enabled) {
 }
 
 void FlutterWindowsView::OnDwmCompositionChanged() {
-  UpdateVsync(*engine_, *binding_handler_);
+  UpdateVsync(*engine_, NeedsVsync());
 }
 
 void FlutterWindowsView::OnWindowStateEvent(HWND hwnd, WindowStateEvent event) {
@@ -715,4 +719,11 @@ void FlutterWindowsView::OnWindowStateEvent(HWND hwnd, WindowStateEvent event) {
   }
 }
 
+bool FlutterWindowsView::NeedsVsync() const {
+  // If the Desktop Window Manager composition is enabled,
+  // the system itself synchronizes with vsync.
+  // See: https://learn.microsoft.com/windows/win32/dwm/composition-ovw
+  return !windows_proc_table_->DwmIsCompositionEnabled();
+}
+
 }  // namespace flutter

engine/src/flutter/shell/platform/windows/flutter_windows_view.h

@@ -23,6 +23,7 @@
 #include "flutter/shell/platform/windows/window_binding_handler.h"
 #include "flutter/shell/platform/windows/window_binding_handler_delegate.h"
 #include "flutter/shell/platform/windows/window_state.h"
+#include "flutter/shell/platform/windows/windows_proc_table.h"
 
 namespace flutter {
 
@@ -35,7 +36,9 @@ class FlutterWindowsView : public WindowBindingHandlerDelegate {
   //
   // In order for object to render Flutter content the SetEngine method must be
   // called with a valid FlutterWindowsEngine instance.
-  FlutterWindowsView(std::unique_ptr<WindowBindingHandler> window_binding);
+  FlutterWindowsView(
+      std::unique_ptr<WindowBindingHandler> window_binding,
+      std::shared_ptr<WindowsProcTable> windows_proc_table = nullptr);
 
   virtual ~FlutterWindowsView();
 
@@ -365,9 +368,16 @@ class FlutterWindowsView : public WindowBindingHandlerDelegate {
   void SendPointerEventWithData(const FlutterPointerEvent& event_data,
                                 PointerState* state);
 
+  // If true, rendering to the window should synchronize with the vsync
+  // to prevent screen tearing.
+  bool NeedsVsync() const;
+
   // The engine associated with this view.
   FlutterWindowsEngine* engine_ = nullptr;
 
+  // Mocks win32 APIs.
+  std::shared_ptr<WindowsProcTable> windows_proc_table_;
+
   // Keeps track of pointer states in relation to the window.
   std::unordered_map<int32_t, std::unique_ptr<PointerState>> pointer_states_;
 

engine/src/flutter/shell/platform/windows/flutter_windows_view_unittests.cc

@@ -21,6 +21,7 @@
 #include "flutter/shell/platform/windows/testing/engine_modifier.h"
 #include "flutter/shell/platform/windows/testing/mock_angle_surface_manager.h"
 #include "flutter/shell/platform/windows/testing/mock_window_binding_handler.h"
+#include "flutter/shell/platform/windows/testing/mock_windows_proc_table.h"
 #include "flutter/shell/platform/windows/testing/test_keyboard.h"
 
 #include "gmock/gmock.h"
@@ -814,18 +815,20 @@ TEST(FlutterWindowsViewTest, WindowResizeTests) {
 
   auto window_binding_handler =
       std::make_unique<NiceMock<MockWindowBindingHandler>>();
+  auto windows_proc_table = std::make_shared<MockWindowsProcTable>();
   std::unique_ptr<MockAngleSurfaceManager> surface_manager =
       std::make_unique<MockAngleSurfaceManager>();
 
-  EXPECT_CALL(*window_binding_handler.get(), NeedsVSync)
-      .WillOnce(Return(false));
+  EXPECT_CALL(*windows_proc_table.get(), DwmIsCompositionEnabled)
+      .WillOnce(Return(true));
   EXPECT_CALL(
       *surface_manager.get(),
       ResizeSurface(_, /*width=*/500, /*height=*/500, /*enable_vsync=*/false))
       .Times(1);
   EXPECT_CALL(*surface_manager.get(), DestroySurface).Times(1);
 
-  FlutterWindowsView view(std::move(window_binding_handler));
+  FlutterWindowsView view(std::move(window_binding_handler),
+                          std::move(windows_proc_table));
   modifier.SetSurfaceManager(std::move(surface_manager));
   view.SetEngine(engine.get());
 
@@ -861,18 +864,20 @@ TEST(FlutterWindowsViewTest, TestEmptyFrameResizes) {
 
   auto window_binding_handler =
       std::make_unique<NiceMock<MockWindowBindingHandler>>();
+  auto windows_proc_table = std::make_shared<MockWindowsProcTable>();
   std::unique_ptr<MockAngleSurfaceManager> surface_manager =
       std::make_unique<MockAngleSurfaceManager>();
 
-  EXPECT_CALL(*window_binding_handler.get(), NeedsVSync)
-      .WillOnce(Return(false));
+  EXPECT_CALL(*windows_proc_table.get(), DwmIsCompositionEnabled)
+      .WillOnce(Return(true));
   EXPECT_CALL(
       *surface_manager.get(),
       ResizeSurface(_, /*width=*/500, /*height=*/500, /*enable_vsync=*/false))
       .Times(1);
   EXPECT_CALL(*surface_manager.get(), DestroySurface).Times(1);
 
-  FlutterWindowsView view(std::move(window_binding_handler));
+  FlutterWindowsView view(std::move(window_binding_handler),
+                          std::move(windows_proc_table));
   modifier.SetSurfaceManager(std::move(surface_manager));
   view.SetEngine(engine.get());
 
@@ -1254,17 +1259,19 @@ TEST(FlutterWindowsViewTest, DisablesVSyncAtStartup) {
       std::make_unique<MockFlutterWindowsEngine>();
   auto window_binding_handler =
       std::make_unique<NiceMock<MockWindowBindingHandler>>();
+  auto windows_proc_table = std::make_shared<MockWindowsProcTable>();
   std::unique_ptr<MockAngleSurfaceManager> surface_manager =
       std::make_unique<MockAngleSurfaceManager>();
 
   EXPECT_CALL(*engine.get(), running).WillRepeatedly(Return(false));
   EXPECT_CALL(*engine.get(), PostRasterThreadTask).Times(0);
 
-  EXPECT_CALL(*window_binding_handler.get(), NeedsVSync)
-      .WillOnce(Return(false));
+  EXPECT_CALL(*windows_proc_table.get(), DwmIsCompositionEnabled)
+      .WillOnce(Return(true));
 
   EngineModifier modifier(engine.get());
-  FlutterWindowsView view(std::move(window_binding_handler));
+  FlutterWindowsView view(std::move(window_binding_handler),
+                          std::move(windows_proc_table));
 
   InSequence s;
   EXPECT_CALL(*surface_manager.get(), CreateSurface(_, _, _))
@@ -1289,15 +1296,18 @@ TEST(FlutterWindowsViewTest, EnablesVSyncAtStartup) {
       std::make_unique<MockFlutterWindowsEngine>();
   auto window_binding_handler =
       std::make_unique<NiceMock<MockWindowBindingHandler>>();
+  auto windows_proc_table = std::make_shared<MockWindowsProcTable>();
   std::unique_ptr<MockAngleSurfaceManager> surface_manager =
       std::make_unique<MockAngleSurfaceManager>();
 
   EXPECT_CALL(*engine.get(), running).WillRepeatedly(Return(false));
   EXPECT_CALL(*engine.get(), PostRasterThreadTask).Times(0);
-  EXPECT_CALL(*window_binding_handler.get(), NeedsVSync).WillOnce(Return(true));
+  EXPECT_CALL(*windows_proc_table.get(), DwmIsCompositionEnabled)
+      .WillOnce(Return(false));
 
   EngineModifier modifier(engine.get());
-  FlutterWindowsView view(std::move(window_binding_handler));
+  FlutterWindowsView view(std::move(window_binding_handler),
+                          std::move(windows_proc_table));
 
   InSequence s;
   EXPECT_CALL(*surface_manager.get(), CreateSurface(_, _, _))
@@ -1322,14 +1332,17 @@ TEST(FlutterWindowsViewTest, DisablesVSyncAfterStartup) {
       std::make_unique<MockFlutterWindowsEngine>();
   auto window_binding_handler =
       std::make_unique<NiceMock<MockWindowBindingHandler>>();
+  auto windows_proc_table = std::make_shared<MockWindowsProcTable>();
   std::unique_ptr<MockAngleSurfaceManager> surface_manager =
       std::make_unique<MockAngleSurfaceManager>();
 
   EXPECT_CALL(*engine.get(), running).WillRepeatedly(Return(true));
-  EXPECT_CALL(*window_binding_handler.get(), NeedsVSync).WillOnce(Return(true));
+  EXPECT_CALL(*windows_proc_table.get(), DwmIsCompositionEnabled)
+      .WillOnce(Return(true));
 
   EngineModifier modifier(engine.get());
-  FlutterWindowsView view(std::move(window_binding_handler));
+  FlutterWindowsView view(std::move(window_binding_handler),
+                          std::move(windows_proc_table));
 
   InSequence s;
   EXPECT_CALL(*surface_manager.get(), CreateSurface(_, _, _))
@@ -1340,7 +1353,7 @@ TEST(FlutterWindowsViewTest, DisablesVSyncAfterStartup) {
         callback();
         return true;
       });
-  EXPECT_CALL(*surface_manager.get(), SetVSyncEnabled(true)).Times(1);
+  EXPECT_CALL(*surface_manager.get(), SetVSyncEnabled(false)).Times(1);
   EXPECT_CALL(*surface_manager.get(), ClearCurrent).Times(0);
 
   EXPECT_CALL(*engine.get(), Stop).Times(1);
@@ -1359,15 +1372,18 @@ TEST(FlutterWindowsViewTest, EnablesVSyncAfterStartup) {
       std::make_unique<MockFlutterWindowsEngine>();
   auto window_binding_handler =
       std::make_unique<NiceMock<MockWindowBindingHandler>>();
+  auto windows_proc_table = std::make_shared<MockWindowsProcTable>();
   std::unique_ptr<MockAngleSurfaceManager> surface_manager =
       std::make_unique<MockAngleSurfaceManager>();
 
   EXPECT_CALL(*engine.get(), running).WillRepeatedly(Return(true));
 
-  EXPECT_CALL(*window_binding_handler.get(), NeedsVSync).WillOnce(Return(true));
+  EXPECT_CALL(*windows_proc_table.get(), DwmIsCompositionEnabled)
+      .WillOnce(Return(false));
 
   EngineModifier modifier(engine.get());
-  FlutterWindowsView view(std::move(window_binding_handler));
+  FlutterWindowsView view(std::move(window_binding_handler),
+                          std::move(windows_proc_table));
 
   InSequence s;
   EXPECT_CALL(*surface_manager.get(), CreateSurface(_, _, _))
@@ -1398,6 +1414,7 @@ TEST(FlutterWindowsViewTest, UpdatesVSyncOnDwmUpdates) {
       std::make_unique<MockFlutterWindowsEngine>();
   auto window_binding_handler =
       std::make_unique<NiceMock<MockWindowBindingHandler>>();
+  auto windows_proc_table = std::make_shared<MockWindowsProcTable>();
   std::unique_ptr<MockAngleSurfaceManager> surface_manager =
       std::make_unique<MockAngleSurfaceManager>();
 
@@ -1409,14 +1426,15 @@ TEST(FlutterWindowsViewTest, UpdatesVSyncOnDwmUpdates) {
         return true;
       });
 
-  EXPECT_CALL(*window_binding_handler.get(), NeedsVSync)
-      .WillOnce(Return(true))
-      .WillOnce(Return(false));
+  EXPECT_CALL(*windows_proc_table.get(), DwmIsCompositionEnabled)
+      .WillOnce(Return(false))
+      .WillOnce(Return(true));
 
   EXPECT_CALL(*surface_manager.get(), ClearCurrent).Times(0);
 
   EngineModifier modifier(engine.get());
-  FlutterWindowsView view(std::move(window_binding_handler));
+  FlutterWindowsView view(std::move(window_binding_handler),
+                          std::move(windows_proc_table));
 
   InSequence s;
   EXPECT_CALL(*surface_manager.get(), SetVSyncEnabled(true)).Times(1);

engine/src/flutter/shell/platform/windows/testing/mock_window_binding_handler.h

@@ -40,7 +40,6 @@ class MockWindowBindingHandler : public WindowBindingHandler {
   MOCK_METHOD(PointerLocation, GetPrimaryPointerLocation, (), (override));
   MOCK_METHOD(AlertPlatformNodeDelegate*, GetAlertDelegate, (), (override));
   MOCK_METHOD(ui::AXPlatformNodeWin*, GetAlert, (), (override));
-  MOCK_METHOD(bool, NeedsVSync, (), (const override));
 
  private:
   FML_DISALLOW_COPY_AND_ASSIGN(MockWindowBindingHandler);

engine/src/flutter/shell/platform/windows/testing/mock_windows_proc_table.h

@@ -21,14 +21,16 @@ class MockWindowsProcTable : public WindowsProcTable {
   MOCK_METHOD(BOOL,
               GetPointerType,
               (UINT32 pointer_id, POINTER_INPUT_TYPE* pointer_type),
-              (override));
+              (const, override));
 
   MOCK_METHOD(LRESULT,
               GetThreadPreferredUILanguages,
               (DWORD, PULONG, PZZWSTR, PULONG),
               (const, override));
 
-  MOCK_METHOD(bool, GetHighContrastEnabled, (), (override));
+  MOCK_METHOD(bool, GetHighContrastEnabled, (), (const, override));
+
+  MOCK_METHOD(bool, DwmIsCompositionEnabled, (), (const, override));
 
  private:
   FML_DISALLOW_COPY_AND_ASSIGN(MockWindowsProcTable);

engine/src/flutter/shell/platform/windows/window_binding_handler.h

@@ -96,10 +96,6 @@ class WindowBindingHandler {
 
   // Retrieve the alert node.
   virtual ui::AXPlatformNodeWin* GetAlert() = 0;
-
-  // If true, rendering to the window should synchronize with the vsync
-  // to prevent screen tearing.
-  virtual bool NeedsVSync() const = 0;
 };
 
 }  // namespace flutter

engine/src/flutter/shell/platform/windows/windows_proc_table.cc

@@ -4,6 +4,9 @@
 
 #include "flutter/shell/platform/windows/windows_proc_table.h"
 
+#include <WinUser.h>
+#include <dwmapi.h>
+
 namespace flutter {
 
 WindowsProcTable::WindowsProcTable() {
@@ -17,7 +20,7 @@ WindowsProcTable::~WindowsProcTable() {
 }
 
 BOOL WindowsProcTable::GetPointerType(UINT32 pointer_id,
-                                      POINTER_INPUT_TYPE* pointer_type) {
+                                      POINTER_INPUT_TYPE* pointer_type) const {
   if (!get_pointer_type_.has_value()) {
     return FALSE;
   }
@@ -32,7 +35,7 @@ LRESULT WindowsProcTable::GetThreadPreferredUILanguages(DWORD flags,
   return ::GetThreadPreferredUILanguages(flags, count, languages, length);
 }
 
-bool WindowsProcTable::GetHighContrastEnabled() {
+bool WindowsProcTable::GetHighContrastEnabled() const {
   HIGHCONTRAST high_contrast = {.cbSize = sizeof(HIGHCONTRAST)};
   if (!::SystemParametersInfoW(SPI_GETHIGHCONTRAST, sizeof(HIGHCONTRAST),
                                &high_contrast, 0)) {
@@ -42,4 +45,13 @@ bool WindowsProcTable::GetHighContrastEnabled() {
   return high_contrast.dwFlags & HCF_HIGHCONTRASTON;
 }
 
+bool WindowsProcTable::DwmIsCompositionEnabled() const {
+  BOOL composition_enabled;
+  if (SUCCEEDED(::DwmIsCompositionEnabled(&composition_enabled))) {
+    return composition_enabled;
+  }
+
+  return true;
+}
+
 }  // namespace flutter

engine/src/flutter/shell/platform/windows/windows_proc_table.h

@@ -24,11 +24,12 @@ class WindowsProcTable {
   // Used to react differently to touch or pen inputs. Returns false on failure.
   // Available on Windows 8 and newer, otherwise returns false.
   virtual BOOL GetPointerType(UINT32 pointer_id,
-                              POINTER_INPUT_TYPE* pointer_type);
+                              POINTER_INPUT_TYPE* pointer_type) const;
 
   // Get the preferred languages for the thread, and optionally the process,
   // and system, in that order, depending on the flags.
-  // See
+  //
+  // See:
   // https://learn.microsoft.com/windows/win32/api/winnls/nf-winnls-getthreadpreferreduilanguages
   virtual LRESULT GetThreadPreferredUILanguages(DWORD flags,
                                                 PULONG count,
@@ -38,9 +39,16 @@ class WindowsProcTable {
   // Get whether high contrast is enabled.
   //
   // Available on Windows 8 and newer, otherwise returns false.
-  // See
+  //
+  // See:
   // https://learn.microsoft.com/windows/win32/winauto/high-contrast-parameter
-  virtual bool GetHighContrastEnabled();
+  virtual bool GetHighContrastEnabled() const;
+
+  // Get whether the system compositor, DWM, is enabled.
+  //
+  // See:
+  // https://learn.microsoft.com/windows/win32/api/dwmapi/nf-dwmapi-dwmiscompositionenabled
+  virtual bool DwmIsCompositionEnabled() const;
 
  private:
   using GetPointerType_ = BOOL __stdcall(UINT32 pointerId,