exo: Implement wayland gamepad support

components/exo/gamepad.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_EXO_GAMEPAD_H_
+#define COMPONENTS_EXO_GAMEPAD_H_
+
+#include <memory>
+
+#include "base/macros.h"
+#include "base/sequenced_task_runner.h"
+#include "base/threading/thread.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "device/gamepad/gamepad_data_fetcher.h"
+
+namespace exo {
+class GamepadDelegate;
+
+// This class represents a gamepad, it implements a background thread
+// for polling gamepad devices and notifies the GamepadDelegate of any
+// changes.
+class Gamepad {
+ public:
+  // This class will post tasks to invoke the delegate on the thread runner
+  // which is associated with the thread that is creating this instance.
+  Gamepad(size_t id, GamepadDelegate* delegate);
+
+  // Allows test cases to specify a GamepadDataFetcher to provide mock gamepad
+  // data.
+  Gamepad(size_t id,
+          GamepadDelegate* delegate,
+          std::unique_ptr<device::GamepadDataFetcher> fetcher);
+  virtual ~Gamepad();
+
+ private:
+  // Schedules a poll on the polling thread. Can be called from any thread.
+  void ScheduleOnPoll();
+
+  // Polls devices for new data and posts delegate updates.
+  // Can only be called on the polling thread.
+  void OnPoll();
+
+  // Initializes the underlying gamepad data fetcher.
+  // Can only be called on the polling thread.
+  void InitializePollingThread();
+
+  // Gamepad id
+  size_t id_;
+
+  // The delegate instance that all events are dispatched to.
+  GamepadDelegate* const delegate_;
+
+  // Implements the logic to fetch gamepad information from connected devices.
+  std::unique_ptr<device::GamepadDataFetcher> fetcher_;
+
+  // The thread on which the polling is executed.
+  std::unique_ptr<base::Thread> polling_thread_;
+
+  // The current state of gamepad.
+  blink::WebGamepads state_;
+
+  // Reference to the task runner of the thread that created this instance.
+  scoped_refptr<base::SingleThreadTaskRunner> origin_task_runner_;
+
+  base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(Gamepad);
+};
+
+}  // namespace exo
+
+#endif  // COMPONENTS_EXO_GAMEPAD_H_