Add ALSA support to volume keys

chrome/browser/chromeos/audio_mixer_base.h

+// Copyright (c) 2010 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_MIXER_BASE_H_
+#define CHROME_BROWSER_CHROMEOS_AUDIO_MIXER_BASE_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/callback.h"
+
+namespace chromeos {
+
+const double kSilenceDb = -200.0;
+
+class AudioMixerBase {
+ public:
+  enum State {
+    UNINITIALIZED = 0,
+    INITIALIZING,
+    READY,
+    SHUTTING_DOWN,
+    IN_ERROR
+  };
+
+  AudioMixerBase() {}
+  virtual ~AudioMixerBase() {}
+
+  // Non-blocking, connect to Mixer and find a default device, and call
+  // callback when complete with success code.
+  typedef Callback1<bool>::Type InitDoneCallback;
+  virtual bool Init(InitDoneCallback* callback) = 0;
+
+  // Blocking init call guarantees Mixer is connected before returning.
+  virtual bool InitSync() = 0;
+
+  // Blocking call. Returns a default of kSilenceDb on error.
+  virtual double GetVolumeDb() const = 0;
+
+  virtual void GetVolumeLimits(double* vol_min, double* vol_max) = 0;
+
+  // Non-blocking call.
+  virtual void SetVolumeDb(double vol_db) = 0;
+
+  // Gets the mute state of the default device (true == mute). Blocking call.
+  // Returns a default of false on error.
+  virtual bool IsMute() const = 0;
+
+  // Non-Blocking call.
+  virtual void SetMute(bool mute) = 0;
+
+  // Returns READY if we have a valid working connection to the Mixer.
+  // This can return IN_ERROR if we lose the connection, even after an original
+  // successful init.  Non-blocking call.
+  virtual State CheckState() const = 0;
+
+ protected:
+
+  DISALLOW_COPY_AND_ASSIGN(AudioMixerBase);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_AUDIO_MIXER_BASE_H_
+