Adding key press detection in the browser process.

media/audio/key_press_monitor.h

+// Copyright (c) 2013 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 MEDIA_AUDIO_KEY_PRESS_MONITOR_H_
+#define MEDIA_AUDIO_KEY_PRESS_MONITOR_H_
+
+#include <set>
+
+#include "base/basictypes.h"
+#include "base/observer_list.h"
+#include "base/synchronization/lock.h"
+#include "media/base/user_input_monitor.h"
+
+namespace base {
+class MessageLoopProxy;
+}  // namespace base
+
+namespace media {
+
+// This class monitors the system-wide key presses and notifies the listeners.
+// Not thread safe. All methods except ctor and dtor should be called on the
+// thread whose message loop is passed to the ctor.
+class KeyPressMonitor : public UserInputObserver {
+ public:
+  class KeyPressListener {
+   public:
+    // This is called on |message_loop_|'s thread.
+    // If a key is held down, OnKeyPressed will be called only once before the
+    // key is released.
+    virtual void OnKeyPressed() = 0;
+
+   protected:
+    virtual ~KeyPressListener() {}
+  };
+
+  // |message_loop| is the message loop that this object runs on and the
+  // listeners are called on.
+  // |io_message_loop| and |ui_message_loop| are the IO and UI message loops
+  // to receive system events. Linux requires the IO message loop, and Mac and
+  // Windows require the UI message loop.
+  KeyPressMonitor(const scoped_refptr<base::MessageLoopProxy>& message_loop,
+                  const scoped_refptr<base::MessageLoopProxy>& io_message_loop,
+                  const scoped_refptr<base::MessageLoopProxy>& ui_message_loop);
+  virtual ~KeyPressMonitor();
+
+  // Impl of UserInputObserver.
+  virtual void OnMouseMoved(const SkIPoint& position) OVERRIDE;
+  virtual void OnKeyboardEvent(ui::EventType event,
+                               ui::KeyboardCode key_code) OVERRIDE;
+
+  // Adds |listener| to receive key press notifications. A listener should not
+  // be added more than once.
+  // The callers should make sure to call RemoveKeyPressListener before
+  // |listener| is destroyed.
+  void AddKeyPressListener(KeyPressListener* listener);
+  // Removes |listener| from receiving key press notifications. Does nothing if
+  // |listener| has not been added or has already been removed.
+  void RemoveKeyPressListener(KeyPressListener* listener);
+
+ private:
+  // Raw pointers of the listeners.
+  ObserverList<KeyPressListener> listeners_;
+  // The message loop of the thread that this object runs on.
+  scoped_refptr<base::MessageLoopProxy> message_loop_;
+  // The browser IO thread message loop.
+  scoped_refptr<base::MessageLoopProxy> io_message_loop_;
+  // The browser UI thread message loop.
+  scoped_refptr<base::MessageLoopProxy> ui_message_loop_;
+  // The object monitoring system events.
+  scoped_ptr<UserInputMonitor> monitor_;
+  // The WeakPtrFactory used to generate WeakPtr to pass to |monitor_|.
+  // Must be invalidated on the |message_loop_| thread.
+  base::WeakPtrFactory<KeyPressMonitor> weak_ptr_factory_;
+  // The set of keys currently held down.
+  std::set<ui::KeyboardCode> pressed_keys_;
+
+  DISALLOW_COPY_AND_ASSIGN(KeyPressMonitor);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_AUDIO_KEY_PRESS_MONITOR_H_