[Windows] Prepare keyboard & text input plugins for multi-view (#39464)

* Start

* Add keyboard reset hook

* Update comment

* Format

Author: loic-sharma

shell/platform/windows/flutter_windows_engine.cc

@@ -17,6 +17,7 @@
 #include "flutter/shell/platform/common/path_utils.h"
 #include "flutter/shell/platform/windows/accessibility_bridge_windows.h"
 #include "flutter/shell/platform/windows/flutter_windows_view.h"
+#include "flutter/shell/platform/windows/keyboard_key_channel_handler.h"
 #include "flutter/shell/platform/windows/system_utils.h"
 #include "flutter/shell/platform/windows/task_runner.h"
 #include "flutter/third_party/accessibility/ax/ax_node.h"
@@ -206,6 +207,8 @@ FlutterWindowsEngine::FlutterWindowsEngine(
   // Set up internal channels.
   // TODO: Replace this with an embedder.h API. See
   // https://github.com/flutter/flutter/issues/71099
+  internal_plugin_registrar_ =
+      std::make_unique<PluginRegistrar>(plugin_registrar_.get());
   cursor_handler_ =
       std::make_unique<CursorHandler>(messenger_wrapper_.get(), this);
   platform_handler_ =
@@ -322,7 +325,7 @@ bool FlutterWindowsEngine::Run(std::string_view entrypoint) {
   };
   args.on_pre_engine_restart_callback = [](void* user_data) {
     auto host = static_cast<FlutterWindowsEngine*>(user_data);
-    host->view()->OnPreEngineRestart();
+    host->OnPreEngineRestart();
   };
   args.update_semantics_callback = [](const FlutterSemanticsUpdate* update,
                                       void* user_data) {
@@ -401,6 +404,7 @@ bool FlutterWindowsEngine::Stop() {
 
 void FlutterWindowsEngine::SetView(FlutterWindowsView* view) {
   view_ = view;
+  InitializeKeyboard();
 }
 
 void FlutterWindowsEngine::OnVsync(intptr_t baton) {
@@ -561,6 +565,47 @@ void FlutterWindowsEngine::SendSystemLocales() {
                               flutter_locale_list.size());
 }
 
+void FlutterWindowsEngine::InitializeKeyboard() {
+  if (view_ == nullptr) {
+    FML_LOG(ERROR) << "Cannot initialize keyboard on Windows headless mode.";
+  }
+
+  auto internal_plugin_messenger = internal_plugin_registrar_->messenger();
+  KeyboardKeyEmbedderHandler::GetKeyStateHandler get_key_state = GetKeyState;
+  KeyboardKeyEmbedderHandler::MapVirtualKeyToScanCode map_vk_to_scan =
+      [](UINT virtual_key, bool extended) {
+        return MapVirtualKey(virtual_key,
+                             extended ? MAPVK_VK_TO_VSC_EX : MAPVK_VK_TO_VSC);
+      };
+  keyboard_key_handler_ = std::move(CreateKeyboardKeyHandler(
+      internal_plugin_messenger, get_key_state, map_vk_to_scan));
+  text_input_plugin_ =
+      std::move(CreateTextInputPlugin(internal_plugin_messenger));
+}
+
+std::unique_ptr<KeyboardHandlerBase>
+FlutterWindowsEngine::CreateKeyboardKeyHandler(
+    BinaryMessenger* messenger,
+    KeyboardKeyEmbedderHandler::GetKeyStateHandler get_key_state,
+    KeyboardKeyEmbedderHandler::MapVirtualKeyToScanCode map_vk_to_scan) {
+  auto keyboard_key_handler = std::make_unique<KeyboardKeyHandler>();
+  keyboard_key_handler->AddDelegate(
+      std::make_unique<KeyboardKeyEmbedderHandler>(
+          [this](const FlutterKeyEvent& event, FlutterKeyEventCallback callback,
+                 void* user_data) {
+            return SendKeyEvent(event, callback, user_data);
+          },
+          get_key_state, map_vk_to_scan));
+  keyboard_key_handler->AddDelegate(
+      std::make_unique<KeyboardKeyChannelHandler>(messenger));
+  return keyboard_key_handler;
+}
+
+std::unique_ptr<TextInputPlugin> FlutterWindowsEngine::CreateTextInputPlugin(
+    BinaryMessenger* messenger) {
+  return std::make_unique<TextInputPlugin>(messenger, view_);
+}
+
 bool FlutterWindowsEngine::RegisterExternalTexture(int64_t texture_id) {
   return (embedder_api_.RegisterExternalTexture(engine_, texture_id) ==
           kSuccess);
@@ -625,6 +670,13 @@ FlutterWindowsEngine::CreateAccessibilityBridge(FlutterWindowsEngine* engine,
   return std::make_shared<AccessibilityBridgeWindows>(engine, view);
 }
 
+void FlutterWindowsEngine::OnPreEngineRestart() {
+  // Reset the keyboard's state on hot restart.
+  if (view_) {
+    InitializeKeyboard();
+  }
+}
+
 gfx::NativeViewAccessible FlutterWindowsEngine::GetNativeAccessibleFromId(
     AccessibilityNodeId id) {
   if (!accessibility_bridge_) {

shell/platform/windows/flutter_windows_engine.h

@@ -25,10 +25,13 @@
 #include "flutter/shell/platform/windows/flutter_desktop_messenger.h"
 #include "flutter/shell/platform/windows/flutter_project_bundle.h"
 #include "flutter/shell/platform/windows/flutter_windows_texture_registrar.h"
+#include "flutter/shell/platform/windows/keyboard_handler_base.h"
+#include "flutter/shell/platform/windows/keyboard_key_embedder_handler.h"
 #include "flutter/shell/platform/windows/platform_handler.h"
 #include "flutter/shell/platform/windows/public/flutter_windows.h"
 #include "flutter/shell/platform/windows/settings_plugin.h"
 #include "flutter/shell/platform/windows/task_runner.h"
+#include "flutter/shell/platform/windows/text_input_plugin.h"
 #include "flutter/shell/platform/windows/window_proc_delegate_manager.h"
 #include "flutter/shell/platform/windows/window_state.h"
 #include "flutter/shell/platform/windows/windows_registry.h"
@@ -163,6 +166,11 @@ class FlutterWindowsEngine {
                     FlutterKeyEventCallback callback,
                     void* user_data);
 
+  KeyboardHandlerBase* keyboard_key_handler() {
+    return keyboard_key_handler_.get();
+  }
+  TextInputPlugin* text_input_plugin() { return text_input_plugin_.get(); }
+
   // Sends the given message to the engine, calling |reply| with |user_data|
   // when a response is received from the engine if they are non-null.
   bool SendPlatformMessage(const char* channel,
@@ -249,6 +257,22 @@ class FlutterWindowsEngine {
   void UpdateAccessibilityFeatures(FlutterAccessibilityFeature flags);
 
  protected:
+  // Creates the keyboard key handler.
+  //
+  // Exposing this method allows unit tests to override in order to
+  // capture information.
+  virtual std::unique_ptr<KeyboardHandlerBase> CreateKeyboardKeyHandler(
+      BinaryMessenger* messenger,
+      KeyboardKeyEmbedderHandler::GetKeyStateHandler get_key_state,
+      KeyboardKeyEmbedderHandler::MapVirtualKeyToScanCode map_vk_to_scan);
+
+  // Creates the text input plugin.
+  //
+  // Exposing this method allows unit tests to override in order to
+  // capture information.
+  virtual std::unique_ptr<TextInputPlugin> CreateTextInputPlugin(
+      BinaryMessenger* messenger);
+
   // Creates an accessibility bridge with the provided parameters.
   //
   // By default this method calls AccessibilityBridge's constructor. Exposing
@@ -257,6 +281,12 @@ class FlutterWindowsEngine {
       FlutterWindowsEngine* engine,
       FlutterWindowsView* view);
 
+  // Invoked by the engine right before the engine is restarted.
+  //
+  // This should reset necessary states to as if the engine has just been
+  // created. This is typically caused by a hot restart (Shift-R in CLI.)
+  void OnPreEngineRestart();
+
  private:
   // Allows swapping out embedder_api_ calls in tests.
   friend class EngineModifier;
@@ -267,6 +297,12 @@ class FlutterWindowsEngine {
   // system changes.
   void SendSystemLocales();
 
+  // Create the keyboard & text input sub-systems.
+  //
+  // This requires that a view is attached to the engine.
+  // Calling this method again resets the keyboard state.
+  void InitializeKeyboard();
+
   void HandleAccessibilityMessage(FlutterDesktopMessengerRef messenger,
                                   const FlutterDesktopMessage* message);
 
@@ -309,12 +345,21 @@ class FlutterWindowsEngine {
   // May be nullptr if ANGLE failed to initialize.
   std::unique_ptr<AngleSurfaceManager> surface_manager_;
 
+  // The plugin registrar managing internal plugins.
+  std::unique_ptr<PluginRegistrar> internal_plugin_registrar_;
+
   // Handler for cursor events.
   std::unique_ptr<CursorHandler> cursor_handler_;
 
   // Handler for the flutter/platform channel.
   std::unique_ptr<PlatformHandler> platform_handler_;
 
+  // Handlers for keyboard events from Windows.
+  std::unique_ptr<KeyboardHandlerBase> keyboard_key_handler_;
+
+  // Handlers for text events from Windows.
+  std::unique_ptr<TextInputPlugin> text_input_plugin_;
+
   // The settings plugin.
   std::unique_ptr<SettingsPlugin> settings_plugin_;
 

shell/platform/windows/flutter_windows_view.cc

@@ -9,7 +9,6 @@
 #include "flutter/fml/platform/win/wstring_conversion.h"
 #include "flutter/shell/platform/common/accessibility_bridge.h"
 #include "flutter/shell/platform/windows/keyboard_key_channel_handler.h"
-#include "flutter/shell/platform/windows/keyboard_key_embedder_handler.h"
 #include "flutter/shell/platform/windows/text_input_plugin.h"
 #include "flutter/third_party/accessibility/ax/platform/ax_platform_node_win.h"
 
@@ -59,42 +58,12 @@ void FlutterWindowsView::SetEngine(
 
   engine_->SetView(this);
 
-  internal_plugin_registrar_ =
-      std::make_unique<PluginRegistrar>(engine_->GetRegistrar());
-
-  // Set up the system channel handlers.
-  auto internal_plugin_messenger = internal_plugin_registrar_->messenger();
-  InitializeKeyboard();
-
   PhysicalWindowBounds bounds = binding_handler_->GetPhysicalWindowBounds();
 
   SendWindowMetrics(bounds.width, bounds.height,
                     binding_handler_->GetDpiScale());
 }
 
-std::unique_ptr<KeyboardHandlerBase>
-FlutterWindowsView::CreateKeyboardKeyHandler(
-    BinaryMessenger* messenger,
-    KeyboardKeyEmbedderHandler::GetKeyStateHandler get_key_state,
-    KeyboardKeyEmbedderHandler::MapVirtualKeyToScanCode map_vk_to_scan) {
-  auto keyboard_key_handler = std::make_unique<KeyboardKeyHandler>();
-  keyboard_key_handler->AddDelegate(
-      std::make_unique<KeyboardKeyEmbedderHandler>(
-          [this](const FlutterKeyEvent& event, FlutterKeyEventCallback callback,
-                 void* user_data) {
-            return engine_->SendKeyEvent(event, callback, user_data);
-          },
-          get_key_state, map_vk_to_scan));
-  keyboard_key_handler->AddDelegate(
-      std::make_unique<KeyboardKeyChannelHandler>(messenger));
-  return keyboard_key_handler;
-}
-
-std::unique_ptr<TextInputPlugin> FlutterWindowsView::CreateTextInputPlugin(
-    BinaryMessenger* messenger) {
-  return std::make_unique<TextInputPlugin>(messenger, this);
-}
-
 uint32_t FlutterWindowsView::GetFrameBufferId(size_t width, size_t height) {
   // Called on an engine-controlled (non-platform) thread.
   std::unique_lock<std::mutex> lock(resize_mutex_);
@@ -129,10 +98,6 @@ void FlutterWindowsView::ForceRedraw() {
   }
 }
 
-void FlutterWindowsView::OnPreEngineRestart() {
-  InitializeKeyboard();
-}
-
 void FlutterWindowsView::OnWindowSizeChanged(size_t width, size_t height) {
   // Called on the platform thread.
   std::unique_lock<std::mutex> lock(resize_mutex_);
@@ -176,7 +141,7 @@ void FlutterWindowsView::OnPointerMove(double x,
                                        FlutterPointerDeviceKind device_kind,
                                        int32_t device_id,
                                        int modifiers_state) {
-  keyboard_key_handler_->SyncModifiersIfNeeded(modifiers_state);
+  engine_->keyboard_key_handler()->SyncModifiersIfNeeded(modifiers_state);
   SendPointerMove(x, y, GetOrCreatePointerState(device_kind, device_id));
 }
 
@@ -293,20 +258,6 @@ void FlutterWindowsView::OnResetImeComposing() {
   binding_handler_->OnResetImeComposing();
 }
 
-void FlutterWindowsView::InitializeKeyboard() {
-  auto internal_plugin_messenger = internal_plugin_registrar_->messenger();
-  KeyboardKeyEmbedderHandler::GetKeyStateHandler get_key_state = GetKeyState;
-  KeyboardKeyEmbedderHandler::MapVirtualKeyToScanCode map_vk_to_scan =
-      [](UINT virtual_key, bool extended) {
-        return MapVirtualKey(virtual_key,
-                             extended ? MAPVK_VK_TO_VSC_EX : MAPVK_VK_TO_VSC);
-      };
-  keyboard_key_handler_ = std::move(CreateKeyboardKeyHandler(
-      internal_plugin_messenger, get_key_state, map_vk_to_scan));
-  text_input_plugin_ =
-      std::move(CreateTextInputPlugin(internal_plugin_messenger));
-}
-
 // Sends new size  information to FlutterEngine.
 void FlutterWindowsView::SendWindowMetrics(size_t width,
                                            size_t height,
@@ -454,7 +405,7 @@ void FlutterWindowsView::SendPointerPanZoomEnd(int32_t device_id) {
 }
 
 void FlutterWindowsView::SendText(const std::u16string& text) {
-  text_input_plugin_->TextHook(text);
+  engine_->text_input_plugin()->TextHook(text);
 }
 
 void FlutterWindowsView::SendKey(int key,
@@ -464,32 +415,32 @@ void FlutterWindowsView::SendKey(int key,
                                  bool extended,
                                  bool was_down,
                                  KeyEventCallback callback) {
-  keyboard_key_handler_->KeyboardHook(
+  engine_->keyboard_key_handler()->KeyboardHook(
       key, scancode, action, character, extended, was_down,
       [=, callback = std::move(callback)](bool handled) {
         if (!handled) {
-          text_input_plugin_->KeyboardHook(key, scancode, action, character,
-                                           extended, was_down);
+          engine_->text_input_plugin()->KeyboardHook(
+              key, scancode, action, character, extended, was_down);
         }
         callback(handled);
       });
 }
 
 void FlutterWindowsView::SendComposeBegin() {
-  text_input_plugin_->ComposeBeginHook();
+  engine_->text_input_plugin()->ComposeBeginHook();
 }
 
 void FlutterWindowsView::SendComposeCommit() {
-  text_input_plugin_->ComposeCommitHook();
+  engine_->text_input_plugin()->ComposeCommitHook();
 }
 
 void FlutterWindowsView::SendComposeEnd() {
-  text_input_plugin_->ComposeEndHook();
+  engine_->text_input_plugin()->ComposeEndHook();
 }
 
 void FlutterWindowsView::SendComposeChange(const std::u16string& text,
                                            int cursor_pos) {
-  text_input_plugin_->ComposeChangeHook(text, cursor_pos);
+  engine_->text_input_plugin()->ComposeChangeHook(text, cursor_pos);
 }
 
 void FlutterWindowsView::SendScroll(double x,