[Windows] Add restart hooks, and reset keyboard

shell/platform/windows/flutter_windows_engine.cc

@@ -257,6 +257,10 @@ bool FlutterWindowsEngine::RunWithEntrypoint(const char* entrypoint) {
     auto host = static_cast<FlutterWindowsEngine*>(user_data);
     return host->HandlePlatformMessage(engine_message);
   };
+  args.on_pre_engine_restart_callback = [](void* user_data) {
+    auto host = static_cast<FlutterWindowsEngine*>(user_data);
+    host->view()->OnPreEngineRestart();
+  };
 
   args.custom_task_runners = &custom_task_runners;
 

shell/platform/windows/flutter_windows_view.cc

@@ -55,17 +55,7 @@ void FlutterWindowsView::SetEngine(
 
   // Set up the system channel handlers.
   auto internal_plugin_messenger = internal_plugin_registrar_->messenger();
-#ifdef WINUWP
-  flutter::KeyboardKeyHandler::EventDispatcher dispatch_event = nullptr;
-  flutter::KeyboardKeyEmbedderHandler::GetKeyStateHandler get_key_state =
-      nullptr;
-#else
-  flutter::KeyboardKeyHandler::EventDispatcher dispatch_event = SendInput;
-  flutter::KeyboardKeyEmbedderHandler::GetKeyStateHandler get_key_state =
-      GetKeyState;
-#endif
-  RegisterKeyboardHandlers(internal_plugin_messenger, dispatch_event,
-                           get_key_state);
+  InitializeKeyboard();
   platform_handler_ = PlatformHandler::Create(internal_plugin_messenger, this);
   cursor_handler_ = std::make_unique<flutter::CursorHandler>(
       internal_plugin_messenger, binding_handler_.get());
@@ -137,6 +127,11 @@ void FlutterWindowsView::ForceRedraw() {
   }
 }
 
+void FlutterWindowsView::OnPreEngineRestart() {
+  keyboard_handlers_.clear();
+  InitializeKeyboard();
+}
+
 void FlutterWindowsView::OnWindowSizeChanged(size_t width, size_t height) {
   // Called on the platform thread.
   std::unique_lock<std::mutex> lock(resize_mutex_);
@@ -257,6 +252,21 @@ void FlutterWindowsView::OnCursorRectUpdated(const Rect& rect) {
   binding_handler_->OnCursorRectUpdated(rect);
 }
 
+void FlutterWindowsView::InitializeKeyboard() {
+  auto internal_plugin_messenger = internal_plugin_registrar_->messenger();
+#ifdef WINUWP
+  flutter::KeyboardKeyHandler::EventDispatcher dispatch_event = nullptr;
+  flutter::KeyboardKeyEmbedderHandler::GetKeyStateHandler get_key_state =
+      nullptr;
+#else
+  flutter::KeyboardKeyHandler::EventDispatcher dispatch_event = SendInput;
+  flutter::KeyboardKeyEmbedderHandler::GetKeyStateHandler get_key_state =
+      GetKeyState;
+#endif
+  RegisterKeyboardHandlers(internal_plugin_messenger, dispatch_event,
+                           get_key_state);
+}
+
 // Sends new size  information to FlutterEngine.
 void FlutterWindowsView::SendWindowMetrics(size_t width,
                                            size_t height,

shell/platform/windows/flutter_windows_view.h

@@ -90,6 +90,12 @@ class FlutterWindowsView : public WindowBindingHandlerDelegate,
   // Returns the frame buffer id for the engine to render to.
   uint32_t GetFrameBufferId(size_t width, size_t height);
 
+  // Called when the engine is restarted.
+  //
+  // This should reset necessary states to as if the view has just been
+  // created. This is typically caused by a hot restart (Shift-R in CLI.)
+  void OnPreEngineRestart();
+
   // |WindowBindingHandlerDelegate|
   void OnWindowSizeChanged(size_t width, size_t height) override;
 
@@ -207,6 +213,11 @@ class FlutterWindowsView : public WindowBindingHandlerDelegate,
     kDone,
   };
 
+  // Initialize states related to keyboard.
+  //
+  // This is called when the view is first created, or restarted.
+  void InitializeKeyboard();
+
   // Sends a window metrics update to the Flutter engine using current window
   // dimensions in physical
   void SendWindowMetrics(size_t width, size_t height, double dpiscale) const;

shell/platform/windows/flutter_windows_view_unittests.cc

@@ -34,7 +34,7 @@ struct TestResponseHandle {
   void* user_data;
 };
 
-static const bool test_response = false;
+static bool test_response = false;
 
 constexpr uint64_t kKeyEventFromChannel = 0x11;
 constexpr uint64_t kKeyEventFromEmbedder = 0x22;
@@ -80,6 +80,8 @@ std::unique_ptr<FlutterWindowsEngine> GetTestEngine() {
 TEST(FlutterWindowsViewTest, KeySequence) {
   std::unique_ptr<FlutterWindowsEngine> engine = GetTestEngine();
 
+  test_response = false;
+
   auto window_binding_handler =
       std::make_unique<::testing::NiceMock<MockWindowBindingHandler>>();
   FlutterWindowsView view(std::move(window_binding_handler));
@@ -94,5 +96,35 @@ TEST(FlutterWindowsViewTest, KeySequence) {
   key_event_logs.clear();
 }
 
+TEST(FlutterWindowsViewTest, RestartClearsKeyboardState) {
+  std::unique_ptr<FlutterWindowsEngine> engine = GetTestEngine();
+
+  auto window_binding_handler =
+      std::make_unique<::testing::NiceMock<MockWindowBindingHandler>>();
+  FlutterWindowsView view(std::move(window_binding_handler));
+  view.SetEngine(std::move(engine));
+
+  test_response = false;
+
+  // Receives a KeyA down. Events are dispatched and decided unhandled. Now the
+  // keyboard key handler is waiting for the redispatched event.
+  view.OnKey(kVirtualKeyA, kScanCodeKeyA, WM_KEYDOWN, 'a', false, false);
+  EXPECT_EQ(key_event_logs.size(), 2);
+  EXPECT_EQ(key_event_logs[0], kKeyEventFromEmbedder);
+  EXPECT_EQ(key_event_logs[1], kKeyEventFromChannel);
+  key_event_logs.clear();
+
+  // Resets state so that the keyboard key handler is no longer waiting.
+  view.OnPreEngineRestart();
+
+  // Receives another KeyA down. If the state had not been cleared, this event
+  // will be considered the redispatched event and ignored.
+  view.OnKey(kVirtualKeyA, kScanCodeKeyA, WM_KEYDOWN, 'a', false, false);
+  EXPECT_EQ(key_event_logs.size(), 2);
+  EXPECT_EQ(key_event_logs[0], kKeyEventFromEmbedder);
+  EXPECT_EQ(key_event_logs[1], kKeyEventFromChannel);
+  key_event_logs.clear();
+}
+
 }  // namespace testing
 }  // namespace flutter