Persist the user's active audio device choice across chromeos session and reboots.

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;
+  // Sets the device active state in prefs.
+  // Note: |activate_by_user| indicates whether |device| is set to active
+  // by user or by priority, and it only matters when |active| is true.
+  virtual void SetDeviceActive(const AudioDevice& device,
+                               bool active,
+                               bool activate_by_user) = 0;
+  // Returns false if it fails to get device active state from prefs.
+  // Otherwise, returns true, pass the active state data in |*active|
+  // and |*activate_by_user|.
+  // Note: |*activate_by_user| only matters when |*active| is true.
+  virtual bool GetDeviceActive(const AudioDevice& device,
+                               bool* active,
+                               bool* activate_by_user) = 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_