[linux] Adds raw key event handler (#163)

Author: franciscojma86

library/linux/src/embedder.cc

@@ -26,6 +26,7 @@
 
 #include <flutter_embedder.h>
 
+#include "library/linux/src/internal/key_event_handler.h"
 #include "library/linux/src/internal/keyboard_hook_handler.h"
 #include "library/linux/src/internal/plugin_handler.h"
 #include "library/linux/src/internal/text_input_plugin.h"
@@ -50,6 +51,10 @@ struct FlutterEmbedderState {
   // deleted from the heap.
   std::vector<flutter_desktop_embedding::KeyboardHookHandler *>
       keyboard_hook_handlers;
+  // Handles raw key interactions from GLFW.
+  // TODO: Move key_event_handler once
+  // https://github.com/google/flutter-desktop-embedding/issues/102 is resolved.
+  std::unique_ptr<flutter_desktop_embedding::KeyEventHandler> key_event_handler;
 };
 
 static constexpr char kDefaultWindowTitle[] = "Flutter";
@@ -272,6 +277,10 @@ GLFWwindow *CreateFlutterWindow(size_t initial_width, size_t initial_height,
   FlutterEmbedderState *state = new FlutterEmbedderState();
   state->plugin_handler = std::make_unique<PluginHandler>(engine);
   state->engine = engine;
+
+  state->key_event_handler =
+      std::make_unique<KeyEventHandler>(state->plugin_handler.get());
+  state->keyboard_hook_handlers.push_back(state->key_event_handler.get());
   auto input_plugin = std::make_unique<TextInputPlugin>();
   state->keyboard_hook_handlers.push_back(input_plugin.get());
 

library/linux/src/internal/key_event_handler.cc

@@ -0,0 +1,65 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+#include "library/linux/src/internal/key_event_handler.h"
+
+#include <json/json.h>
+#include <iostream>
+
+#include "library/linux/src/internal/json_message_codec.h"
+
+static constexpr char kChannelName[] = "flutter/keyevent";
+
+static constexpr char kKeyCodeKey[] = "keyCode";
+static constexpr char kKeyMapKey[] = "keymap";
+static constexpr char kTypeKey[] = "type";
+
+static constexpr char kAndroidKeyMap[] = "android";
+static constexpr char kKeyUp[] = "keyup";
+static constexpr char kKeyDown[] = "keydown";
+// TODO: This event is not supported by Flutter. Add once it's implemented.
+static constexpr char kRepeat[] = "repeat";
+
+namespace flutter_desktop_embedding {
+
+KeyEventHandler::KeyEventHandler(const BinaryMessenger *messenger)
+    : messenger_(messenger), channel_(kChannelName) {}
+
+KeyEventHandler::~KeyEventHandler() {}
+
+void KeyEventHandler::CharHook(GLFWwindow *window, unsigned int code_point) {}
+
+void KeyEventHandler::KeyboardHook(GLFWwindow *window, int key, int scancode,
+                                   int action, int mods) {
+  // TODO: Translate to a cross-platform key code system rather than passing
+  // the native key code.
+  Json::Value args;
+  args[kKeyCodeKey] = key;
+  args[kKeyMapKey] = kAndroidKeyMap;
+
+  switch (action) {
+    case GLFW_PRESS:
+      args[kTypeKey] = kKeyDown;
+      break;
+    case GLFW_RELEASE:
+      args[kTypeKey] = kKeyUp;
+      break;
+    default:
+      std::cerr << "Unknown key event action: " << action << std::endl;
+      return;
+  }
+  auto message = JsonMessageCodec::GetInstance().EncodeMessage(args);
+  messenger_->Send(channel_, message->data(), message->size());
+}
+
+}  // namespace flutter_desktop_embedding

library/linux/src/internal/key_event_handler.h

@@ -0,0 +1,44 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+#ifndef LIBRARY_LINUX_SRC_INTERNAL_KEY_EVENT_HANDLER_H_
+#define LIBRARY_LINUX_SRC_INTERNAL_kEY_EVENT_HANDLER_H_
+
+#include "library/linux/include/flutter_desktop_embedding/binary_messenger.h"
+#include "library/linux/src/internal/keyboard_hook_handler.h"
+
+namespace flutter_desktop_embedding {
+
+// Implements a KeyboardHookHandler
+//
+// Handles key events and forwards them to the Flutter engine.
+class KeyEventHandler : public KeyboardHookHandler {
+ public:
+  explicit KeyEventHandler(const BinaryMessenger *messenger);
+  virtual ~KeyEventHandler();
+
+  // KeyboardHookHandler.
+  void KeyboardHook(GLFWwindow *window, int key, int scancode, int action,
+                    int mods) override;
+  void CharHook(GLFWwindow *window, unsigned int code_point) override;
+
+ private:
+  // Binds this plugin to the given caller-owned binary messenger. It must
+  // remain valid for the life of the plugin.
+  const BinaryMessenger *messenger_;
+  std::string channel_;
+};
+
+}  // namespace flutter_desktop_embedding
+
+#endif  // LIBRARY_LINUX_SRC_INTERNAL_KEY_EVENT_HANDLER_H_