Asynchronous threaded volume get/set/init

Non-blocking version of init is now being called, and asynchronous set/get of mute and volume is implmenented at PulseAudioMixer level.

The logic has been updated in SystemKeyEventListener so that the audio key behavior follows the latest doc 'Chrome OS Audio Scenarios':
  Increase volume key: unmutes aduio if muted, otherwise increases volume.
  Decrease volume key: do nothing if muted, otherwise decrease volume.
  Mute volume key: always mutes volume.
  UI is displayed after any volume key press.

Currently only the init is being called asynchronously, but the next step will be to add a call allowing asynchronous operation of the volume adjust/unmute sequence from SystemKeyEventListener, and move the ShowVolumeBubble() calls into AudioHandler so that the volume bubble will update once the calls complete on their own thread.

Patch by davej@chromium.org:
http://codereview.chromium.org/2769008/show

BUG=2910
Test=Play video or audio in ChromeOS, and press the system volume up, down, and mute keys to see they follow the above behavior.  Alternating Mute and Increment Volume presses should always bring the volume back to the same level and not creep it upwards.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@51786 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 19 insertions, 32 deletions

diff --git a/chrome/browser/chromeos/audio_handler.cc b/chrome/browser/chromeos/audio_handler.cc
index 05e19ec..f3157ee 100644
--- a/chrome/browser/chromeos/audio_handler.cc
+++ b/chrome/browser/chromeos/audio_handler.cc
@@ -15,10 +15,12 @@ namespace {
 
 const double kSilenceDb = -200.0;
 const double kMinVolumeDb = -90.0;
+// Choosing 6.0dB here instead of 0dB to give user chance to amplify audio some
+// in case sounds or their setup is too quiet for them.
 const double kMaxVolumeDb = 6.0;
 // A value of less than one adjusts quieter volumes in larger steps (giving
 // finer resolution in the higher volumes).
-const double kVolumeBias = 0.7;
+const double kVolumeBias = 0.5;
 
 }  // namespace
 
@@ -29,23 +31,6 @@ const double kVolumeBias = 0.7;
 // TODO(davej): Should we try to regain a connection if for some reason all was
 // initialized fine, but later IsValid() returned false?  Maybe N retries?
 
-double AudioHandler::GetVolumeDb() const {
-  if (!SanityCheck())
-    return kSilenceDb;
-
-  double volume_db = mixer_->GetVolumeDb();
-  if (volume_db <= kSilenceDb)
-    return kSilenceDb;
-  return volume_db;
-}
-
-void AudioHandler::SetVolumeDb(double volume_db) {
-  if (!SanityCheck())
-    return;
-
-  mixer_->SetVolumeDb(volume_db);
-}
-
 double AudioHandler::GetVolumePercent() const {
   if (!SanityCheck())
     return 0;
@@ -69,16 +54,15 @@ void AudioHandler::SetVolumePercent(double volume_percent) {
   mixer_->SetVolumeDb(vol_db);
 }
 
-// Volume range is from kMinVolumeDb at just above 0% to kMaxVolumeDb at 100%
-// with a special case at 0% which maps to kSilenceDb.
 void AudioHandler::AdjustVolumeByPercent(double adjust_by_percent) {
   if (!SanityCheck())
     return;
 
   DLOG(INFO) << "Adjusting Volume by " << adjust_by_percent << " percent";
 
-  double vol = mixer_->GetVolumeDb();
-  double pct = VolumeDbToPercent(vol);
+  double volume = mixer_->GetVolumeDb();
+  double pct = VolumeDbToPercent(volume);
+
   if (pct < 0)
     pct = 0;
   pct = pct + adjust_by_percent;
@@ -86,13 +70,12 @@ void AudioHandler::AdjustVolumeByPercent(double adjust_by_percent) {
     pct = 100.0;
 
   double new_volume;
-
   if (pct <= 0.1)
     new_volume = kSilenceDb;
   else
     new_volume = PercentToVolumeDb(pct);
 
-  if (new_volume != vol)
+  if (new_volume != volume)
     mixer_->SetVolumeDb(new_volume);
 }
 
@@ -112,19 +95,15 @@ void AudioHandler::SetMute(bool do_mute) {
   mixer_->SetMute(do_mute);
 }
 
-void AudioHandler::ToggleMute() {
-  if (!SanityCheck())
-    return;
-
-  mixer_->ToggleMute();
+void AudioHandler::OnMixerInitialized(bool success) {
+  connected_ = success;
+  DLOG(INFO) << "OnMixerInitialized, success = " << success;
 }
 
 AudioHandler::AudioHandler()
     : connected_(false) {
   mixer_.reset(new PulseAudioMixer());
-  if (mixer_->Init()) {
-    connected_ = true;
-  } else {
+  if (!mixer_->Init(NewCallback(this, &AudioHandler::OnMixerInitialized))) {
     LOG(ERROR) << "Unable to connect to PulseAudio";
   }
 }
@@ -135,7 +114,13 @@ AudioHandler::~AudioHandler() {
 inline bool AudioHandler::SanityCheck() const {
   if (!mixer_->IsValid()) {
     if (connected_) {
+      // Something happened and the mixer is no longer valid after having been
+      // initialized earlier.
+      // TODO(davej): Try to reconnect now?
+      connected_ = false;
       LOG(ERROR) << "Lost connection to PulseAudio";
+    } else {
+      LOG(ERROR) << "Mixer not valid";
     }
     return false;
   }
@@ -144,6 +129,8 @@ inline bool AudioHandler::SanityCheck() const {
 
 // VolumeDbToPercent() and PercentToVolumeDb() conversion functions allow us
 // complete control over how the 0 to 100% range is mapped to actual loudness.
+// Volume range is from kMinVolumeDb at just above 0% to kMaxVolumeDb at 100%
+// with a special case at 0% which maps to kSilenceDb.
 //
 // The mapping is confined to these two functions to make it easy to adjust and
 // have everything else just work.  The range is biased to give finer resolution