Save/Restore ALSA volume/mute

chrome/browser/chromeos/audio_mixer_alsa.cc

Index: chrome/browser/chromeos/audio_mixer_alsa.cc
diff --git a/chrome/browser/chromeos/audio_mixer_alsa.cc b/chrome/browser/chromeos/audio_mixer_alsa.cc
index 7f96fa4f2cd9daaa67abbc0bdc61c63940f78256..cd08e27d7ae9226923856f18a16b8ca79f09cb1f 100644
--- a/chrome/browser/chromeos/audio_mixer_alsa.cc
+++ b/chrome/browser/chromeos/audio_mixer_alsa.cc
@@ -8,6 +8,10 @@
 
 #include "base/logging.h"
 #include "base/task.h"
+#include "chrome/browser/browser_process.h"
+#include "chrome/browser/browser_thread.h"
+#include "chrome/browser/prefs/pref_service.h"
+#include "chrome/common/pref_names.h"
 
 namespace chromeos {
 
@@ -19,8 +23,6 @@ namespace chromeos {
 // adjusting that as well.  If the PCM element has more volume steps, it allows
 // for finer granularity in the total volume.
 
-// TODO(davej): Serialize volume/mute to preserve settings when restarting.
-
 typedef long alsa_long_t;  // 'long' is required for ALSA API calls.
 
 namespace {
@@ -29,6 +31,7 @@ const char* kMasterVolume = "Master";
 const char* kPCMVolume = "PCM";
 const double kDefaultMinVolume = -90.0;
 const double kDefaultMaxVolume = 0.0;
+const double kPrefVolumeNotSet = -999.0;
 
 }  // namespace
 
@@ -57,6 +60,7 @@ void AudioMixerAlsa::Init(InitDoneCallback* callback) {
     delete callback;
     return;
   }
+  InitPrefs();
 
   // Post the task of starting up, which can block for 200-500ms,
   // so best not to do it on the caller's thread.
@@ -67,6 +71,7 @@ void AudioMixerAlsa::Init(InitDoneCallback* callback) {
 bool AudioMixerAlsa::InitSync() {
   if (!InitThread())
     return false;
+  InitPrefs();
   return InitializeAlsaMixer();
 }
 
@@ -94,6 +99,7 @@ void AudioMixerAlsa::SetVolumeDb(double vol_db) {
   if (mixer_state_ != READY)
     return;
   DoSetVolumeDb_Locked(vol_db);
+  volume_pref_.SetValue(vol_db);
 }
 
 bool AudioMixerAlsa::IsMute() const {
@@ -111,8 +117,8 @@ void AudioMixerAlsa::SetMute(bool mute) {
   // Set volume to minimum on mute, since switching the element off does not
   // always mute as it should.
 
-  // TODO(davej): Setting volume to minimum can be removed once switching the
-  //              element off can be guaranteed to work.
+  // TODO(davej): Remove save_volume_ and setting volume to minimum if
+  //              switching the element off can be guaranteed to mute it.
 
   bool old_value = GetElementMuted_Locked(elem_master_);
 
@@ -128,6 +134,7 @@ void AudioMixerAlsa::SetMute(bool mute) {
   SetElementMuted_Locked(elem_master_, mute);
   if (elem_pcm_)
     SetElementMuted_Locked(elem_pcm_, mute);
+  mute_pref_.SetValue(mute);
 }
 
 AudioMixer::State AudioMixerAlsa::GetState() const {
@@ -144,6 +151,12 @@ AudioMixer::State AudioMixerAlsa::GetState() const {
 void AudioMixerAlsa::DoInit(InitDoneCallback* callback) {
   bool success = InitializeAlsaMixer();
 
+  if (success) {
+    BrowserThread::PostTask(
+        BrowserThread::UI, FROM_HERE,
+        NewRunnableMethod(this, &AudioMixerAlsa::RestoreVolumeMuteOnUIThread));
+  }
+
   if (callback) {
     callback->Run(success);
     delete callback;
@@ -168,6 +181,19 @@ bool AudioMixerAlsa::InitThread() {
   return true;
 }
 
+void AudioMixerAlsa::InitPrefs() {
+  DCHECK(g_browser_process);
+  PrefService* prefs = g_browser_process->local_state();
+  DCHECK(prefs);
+
+  if (!prefs->FindPreference(prefs::kAudioVolume)) {
+    prefs->RegisterRealPref(prefs::kAudioVolume, kPrefVolumeNotSet);
+    prefs->RegisterBooleanPref(prefs::kAudioMute, false);
+  }
+  volume_pref_.Init(prefs::kAudioVolume, prefs, NULL);
+  mute_pref_.Init(prefs::kAudioMute, prefs, NULL);
+}
+
 bool AudioMixerAlsa::InitializeAlsaMixer() {
   AutoLock lock(mixer_state_lock_);
   if (mixer_state_ != INITIALIZING)
@@ -241,6 +267,29 @@ void AudioMixerAlsa::FreeAlsaMixer() {
   }
 }
 
+void AudioMixerAlsa::DoSetVolumeMute(double volume, bool mute) {
+  AutoLock lock(mixer_state_lock_);
+  if (mixer_state_ != READY)
+    return;
+
+  VLOG(1) << "Setting volume to " << volume << "and mute to " << mute;
+  if (mute) {
+    save_volume_ = volume;
+    DoSetVolumeDb_Locked(min_volume_);
+  } else {
+    DoSetVolumeDb_Locked(volume);
+  }
+
+  SetElementMuted_Locked(elem_master_, mute);
+  if (elem_pcm_)
+    SetElementMuted_Locked(elem_pcm_, mute);
+}
+
+void AudioMixerAlsa::RestoreVolumeMuteOnUIThread() {
+  if (volume_pref_.GetValue() != kPrefVolumeNotSet)

[Daniel Erat, 2011/01/13 21:37:21]

Could you do something like GetValue() <= kDefaultMinVolume or track whether the
pref is set or not in a bool or something?  Floating-point equality comparisons
scare me.

[davejcool, 2011/01/14 00:14:12]

I recall problems in the distant past with comparing doubles as well.  I do see
pref tests that verify doubles are equal when set and then read back.  But I
updated the comparison here anyway so there should be no question.

+    DoSetVolumeMute(volume_pref_.GetValue(), mute_pref_.GetValue());
+}
+
 double AudioMixerAlsa::DoGetVolumeDb_Locked() const {
   double vol_total = 0.0;
   GetElementVolume_Locked(elem_master_, &vol_total);
@@ -258,7 +307,6 @@ void AudioMixerAlsa::DoSetVolumeDb_Locked(double vol_db) {
   // If a PCM volume slider exists, then first set the Master volume to the
   // nearest volume >= requested volume, then adjust PCM volume down to get
   // closer to the requested volume.
-
   if (elem_pcm_) {
     SetElementVolume_Locked(elem_master_, vol_db, &actual_vol, 0.9999f);
     SetElementVolume_Locked(elem_pcm_, vol_db - actual_vol, NULL, 0.5f);