[Windows] Add force redraw to the C++ client wrapper

shell/platform/windows/client_wrapper/flutter_view_controller.cc

@@ -29,6 +29,10 @@ FlutterViewController::~FlutterViewController() {
   }
 }
 
+void FlutterViewController::ForceRedraw() {
+  FlutterDesktopViewControllerForceRedraw(controller_);
+}
+
 std::optional<LRESULT> FlutterViewController::HandleTopLevelWindowProc(
     HWND hwnd,
     UINT message,

shell/platform/windows/client_wrapper/flutter_view_controller_unittests.cc

@@ -27,6 +27,11 @@ class TestWindowsApi : public testing::StubFlutterWindowsApi {
   // |flutter::testing::StubFlutterWindowsApi|
   void ViewControllerDestroy() override { view_controller_destroyed_ = true; }
 
+  // |flutter::testing::StubFlutterWindowsApi|
+  void ViewControllerForceRedraw() override {
+    view_controller_force_redrawed_ = true;
+  }
+
   // |flutter::testing::StubFlutterWindowsApi|
   FlutterDesktopEngineRef EngineCreate(
       const FlutterDesktopEngineProperties& engine_properties) override {
@@ -41,10 +46,14 @@ class TestWindowsApi : public testing::StubFlutterWindowsApi {
 
   bool engine_destroyed() { return engine_destroyed_; }
   bool view_controller_destroyed() { return view_controller_destroyed_; }
+  bool view_controller_force_redrawed() {
+    return view_controller_force_redrawed_;
+  }
 
  private:
   bool engine_destroyed_ = false;
   bool view_controller_destroyed_ = false;
+  bool view_controller_force_redrawed_ = false;
 };
 
 }  // namespace
@@ -79,4 +88,15 @@ TEST(FlutterViewControllerTest, GetView) {
   EXPECT_NE(controller.view(), nullptr);
 }
 
+TEST(FlutterViewControllerTest, ForceRedraw) {
+  DartProject project(L"data");
+  testing::ScopedStubFlutterWindowsApi scoped_api_stub(
+      std::make_unique<TestWindowsApi>());
+  auto test_api = static_cast<TestWindowsApi*>(scoped_api_stub.stub());
+  FlutterViewController controller(100, 100, project);
+
+  controller.ForceRedraw();
+  EXPECT_TRUE(test_api->view_controller_force_redrawed());
+}
+
 }  // namespace flutter

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

@@ -44,6 +44,9 @@ class FlutterViewController {
   // Returns the view managed by this controller.
   FlutterView* view() { return view_.get(); }
 
+  // Requests new frame from the engine and repaints the view.
+  void ForceRedraw();
+
   // Allows the Flutter engine and any interested plugins an opportunity to
   // handle the given message.
   //

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

@@ -65,7 +65,11 @@ FlutterDesktopViewRef FlutterDesktopViewControllerGetView(
 }
 
 void FlutterDesktopViewControllerForceRedraw(
-    FlutterDesktopViewControllerRef controller) {}
+    FlutterDesktopViewControllerRef controller) {
+  if (s_stub_implementation) {
+    s_stub_implementation->ViewControllerForceRedraw();
+  }
+}
 
 bool FlutterDesktopViewControllerHandleTopLevelWindowProc(
     FlutterDesktopViewControllerRef controller,

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

@@ -38,6 +38,9 @@ class StubFlutterWindowsApi {
   // Called for FlutterDesktopViewControllerDestroy.
   virtual void ViewControllerDestroy() {}
 
+  // Called for FlutterDesktopViewControllerForceRedraw.
+  virtual void ViewControllerForceRedraw() {}
+
   // Called for FlutterDesktopViewControllerHandleTopLevelWindowProc.
   virtual bool ViewControllerHandleTopLevelWindowProc(HWND hwnd,
                                                       UINT message,

shell/platform/windows/public/flutter_windows.h

@@ -107,7 +107,7 @@ FLUTTER_EXPORT FlutterDesktopEngineRef FlutterDesktopViewControllerGetEngine(
 FLUTTER_EXPORT FlutterDesktopViewRef
 FlutterDesktopViewControllerGetView(FlutterDesktopViewControllerRef controller);
 
-// Requests new frame from engine and repaints the view
+// Requests new frame from the engine and repaints the view.
 FLUTTER_EXPORT void FlutterDesktopViewControllerForceRedraw(
     FlutterDesktopViewControllerRef controller);