chromeos/audio/audio_devices_pref_handler.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 CHROMEOS_AUDIO_AUDIO_DEVICES_PREF_HANDLER_H_
#define CHROMEOS_AUDIO_AUDIO_DEVICES_PREF_HANDLER_H_

#include "base/memory/ref_counted.h"
#include "chromeos/audio/audio_pref_observer.h"
#include "chromeos/chromeos_export.h"

class PrefService;

namespace chromeos {

struct AudioDevice;

// Used to represent an audio device's state. This state should be updated
// to AUDIO_STATE_ACTIVE when it is selected as active or set to
// AUDIO_STATE_INACTIVE when selected to a different device. When the audio
// device is unplugged, its last active/inactive state should be stored.
// The default value of device state will be AUDIO_STATE_NOT_AVAILABLE if
// the device is not found in the pref settings.
// Note that these states enum can't be renumbered or it would break existing
// preference.
enum AudioDeviceState {
  AUDIO_STATE_ACTIVE = 0,
  AUDIO_STATE_INACTIVE = 1,
  AUDIO_STATE_NOT_AVAILABLE = 2,
};

// Interface that handles audio preference related work, reads and writes
// audio preferences, and notifies AudioPrefObserver for audio preference
// changes.
class CHROMEOS_EXPORT AudioDevicesPrefHandler
    : public base::RefCountedThreadSafe<AudioDevicesPrefHandler> {
 public:
  // Integer because C++ does not allow static const double in header files.
  static const int kDefaultOutputVolumePercent = 75;
  static const int kDefaultHdmiOutputVolumePercent = 100;

  // Gets the audio output volume value from prefs for a device. Since we can
  // only have either a gain or a volume for a device (depending on whether it
  // is input or output), we don't really care which value it is.
  virtual double GetOutputVolumeValue(const AudioDevice* device) = 0;
  virtual double GetInputGainValue(const AudioDevice* device) = 0;
  // Sets the audio volume or gain value to prefs for a device.
  virtual void SetVolumeGainValue(const AudioDevice& device, double value) = 0;

  // Reads the audio mute value from prefs for a device.
  virtual bool GetMuteValue(const AudioDevice& device) = 0;
  // Sets the audio mute value to prefs for a device.
  virtual void SetMuteValue(const AudioDevice& device, bool mute_on) = 0;

  virtual AudioDeviceState GetDeviceState(const AudioDevice& device) = 0;
  virtual void SetDeviceState(const AudioDevice& device,
                              AudioDeviceState state) = 0;

  // Reads the audio output allowed value from prefs.
  virtual bool GetAudioOutputAllowedValue() = 0;

  // Adds an audio preference observer.
  virtual void AddAudioPrefObserver(AudioPrefObserver* observer) = 0;
  // Removes an audio preference observer.
  virtual void RemoveAudioPrefObserver(AudioPrefObserver* observer) = 0;

 protected:
  virtual ~AudioDevicesPrefHandler() {}

 private:
  friend class base::RefCountedThreadSafe<AudioDevicesPrefHandler>;
};

}  // namespace chromeos

#endif  // CHROMEOS_AUDIO_AUDIO_DEVICES_PREF_HANDLER_H_