Store audio device's active state in preference

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.
+enum AudioDeviceState {
+  AUDIO_STATE_ACTIVE,

[Daniel Erat, 2016/01/07 17:31:12]

explicitly specify the numbers for these and document that these can't be
renumbered (since that would break existing prefs)

[hychao, 2016/01/11 07:02:32]

Done.

+  AUDIO_STATE_INACTIVE,
+  AUDIO_STATE_NOT_AVAILABLE,
+};
+
 // 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_