ChromeOS mixer: Talk to new ChromeOS audio server.

chrome/browser/chromeos/audio/audio_mixer_cras.h

+// Copyright (c) 2012 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 CHROME_BROWSER_CHROMEOS_AUDIO_AUDIO_MIXER_CRAS_H_
+#define CHROME_BROWSER_CHROMEOS_AUDIO_AUDIO_MIXER_CRAS_H_
+#pragma once
+
+#include <cras_client.h>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/synchronization/lock.h"
+#include "base/threading/thread.h"
+#include "chrome/browser/chromeos/audio/audio_mixer.h"
+
+namespace chromeos {
+
+// Simple wrapper for sending volume and mute commands to the audio server on
+// ChromeOS.  Interaction happens on a background thread so that initialization
+// can poll until the server is started.
+class AudioMixerCras : public AudioMixer {
+ public:
+  AudioMixerCras();
+  virtual ~AudioMixerCras();
+
+  // AudioMixer implementation.
+  virtual void Init() OVERRIDE;
+  virtual double GetVolumePercent() OVERRIDE;
+  virtual void SetVolumePercent(double percent) OVERRIDE;
+  virtual bool IsMuted() OVERRIDE;
+  virtual void SetMuted(bool muted) OVERRIDE;
+
+ private:
+  // Tries to connect to CRAS.  On failure, posts a delayed Connect() task to
+  // try again.  Failure could occur if the CRAS server isn't running yet.
+  void Connect();
+
+  // Updates |client_| for current values of |volume_percent_| and
+  // |is_muted_|. No-op if not connected.
+  void ApplyState();
+
+  // Interfaces to the audio server.
+  struct cras_client *client_;
+
+  // Indicates if we have connected |client_| to the server.
+  bool client_connected_;
+
+  // Most recently-requested volume, in percent.  This variable is updated
+  // immediately by SetVolumePercent() (post-initialization); the actual mixer
+  // volume is updated later on |thread_| by ApplyState().
+  double volume_percent_;
+
+  // Most recently-requested muting state.
+  bool is_muted_;
+
+  // Is there already a pending call to ApplyState() scheduled on |thread_|?
+  bool apply_is_pending_;
+
+  // Background thread used for interacting with CRAS.
+  scoped_ptr<base::Thread> thread_;
+
+  // Guards |volume_percent_|, |is_muted_|, and |apply_is_pending_|.
+  base::Lock lock_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioMixerCras);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_AUDIO_AUDIO_MIXER_CRAS_H_