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/memory/weak_ptr.h"
+#include "base/sequenced_task_runner.h"
+#include "base/synchronization/lock.h"
+#include "base/threading/thread.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "device/gamepad/gamepad_data_fetcher.h"
+#include "ui/aura/client/focus_change_observer.h"
+
+namespace exo {
+class GamepadDelegate;
+
+// This class represents one or more gamepads, it implements a background thread
+// for polling gamepad devices and notifies the GamepadDelegate of any
+// changes.
+class Gamepad : public aura::client::FocusChangeObserver {
+ 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.
+  explicit Gamepad(GamepadDelegate* delegate);
+  // Allows test cases to specify a GamepadDataFetcher to provide mock gamepad
+  // data.
+  Gamepad(GamepadDelegate* delegate,
+          std::unique_ptr<device::GamepadDataFetcher> fetcher);
+  ~Gamepad() override;
+
+  // Overridden aura::client::FocusChangeObserver:
+  void OnWindowFocused(aura::Window* gained_focus,
+                       aura::Window* lost_focus) override;
+
+ 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();
+
+  // Posts updates of gamepad data to delegate. Can only be called on the
+  // origin thread.
+  void PostGamepadChanges(const blink::WebGamepad new_pad);
+
+  // The delegate instance that all events are dispatched to.
+  GamepadDelegate* const delegate_;
+
+  // The current state of the gamepad represented by this instance.
+  blink::WebGamepad pad_state_;
+
+  // True if an exosphere window is currently focused.

[reveman, 2016/06/30 18:06:11]

s/an exosphere window/a client surface/

[denniskempin, 2016/07/01 02:34:35]

Done.

+  bool exo_focused_{false};

[reveman, 2016/06/30 18:06:11]

nit: remove exo_ prefix

[denniskempin, 2016/07/01 02:34:35]

Done.

+
+  // Reference to the task runner of the thread that created this instance.
+  scoped_refptr<base::SingleThreadTaskRunner> origin_task_runner_;
+
+  // ThreadChecker for the origin thread
+  base::ThreadChecker origin_thread_checker_;
+
+  // The thread on which the polling is executed. It accesses only the variables
+  // below, which are marked as only used by the polling thread.
+  std::unique_ptr<base::Thread> polling_thread_;
+
+  // Implements the logic to fetch gamepad information from connected devices.
+  // Only used by polling thread.
+  std::unique_ptr<device::GamepadDataFetcher> fetcher_;
+
+  // The current state of all gamepads. Only used by polling thread.
+  blink::WebGamepads state_;
+
+  // ThreadChecker for the polling thread.
+  base::ThreadChecker polling_thread_checker_;
+
+  // Weak pointer to this, created during construction on origin thread, but
+  // only used by polling thread to post tasks back to the origin thread.
+  base::WeakPtr<Gamepad> weak_this_;

[reveman, 2016/06/30 18:06:11]

Chromium code will typically keep a callbacks that reference a weak ptr instead.
Can you do that in this case too?

[denniskempin, 2016/07/01 02:34:35]

Done.

+
+  // Weak pointer factory to create the above weak pointer.
+  base::WeakPtrFactory<Gamepad> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(Gamepad);
+};
+
+}  // namespace exo
+
+#endif  // COMPONENTS_EXO_GAMEPAD_H_