Support for showing/hiding status area volume controls in desktop devices

chrome/browser/chromeos/audio/audio_handler.cc

Index: chrome/browser/chromeos/audio/audio_handler.cc
===================================================================
--- chrome/browser/chromeos/audio/audio_handler.cc	(revision 119229)
+++ chrome/browser/chromeos/audio/audio_handler.cc	(working copy)
@@ -10,6 +10,7 @@
 #include "base/logging.h"
 #include "base/memory/singleton.h"
 #include "chrome/browser/chromeos/audio/audio_mixer_alsa.h"
+#include "chrome/browser/chromeos/system/runtime_environment.h"
 #include "content/public/browser/browser_thread.h"
 
 using std::max;
@@ -49,10 +50,16 @@
   return g_audio_handler;
 }
 
-bool AudioHandler::IsInitialized() {
+bool AudioHandler::IsMixerInitialized() {

[xiyuan, 2012/01/27 03:30:29]

nit: move this to after AudioHandler::~AudioHandler since we have moved it in
header.

[achuithb, 2012/01/27 10:12:46]

Done.

   return mixer_->IsInitialized();
 }
 
+// static
+AudioHandler* AudioHandler::GetInstanceIfInitialized() {
+  return g_audio_handler && g_audio_handler->IsMixerInitialized() ?
+         g_audio_handler : NULL;
+}
+
 double AudioHandler::GetVolumePercent() {
   return VolumeDbToPercent(mixer_->GetVolumeDb());
 }
@@ -60,6 +67,7 @@
 void AudioHandler::SetVolumePercent(double volume_percent) {
   volume_percent = min(max(volume_percent, 0.0), 100.0);
   mixer_->SetVolumeDb(PercentToVolumeDb(volume_percent));
+  FOR_EACH_OBSERVER(VolumeObserver, volume_observers_, OnVolumeChanged());
 }
 
 void AudioHandler::AdjustVolumeByPercent(double adjust_by_percent) {
@@ -74,6 +82,7 @@
 
 void AudioHandler::SetMuted(bool mute) {
   mixer_->SetMuted(mute);
+  FOR_EACH_OBSERVER(VolumeObserver, volume_observers_, OnVolumeChanged());
 }
 
 AudioHandler::AudioHandler()
@@ -113,4 +122,26 @@
       (max_volume_db - min_volume_db) + min_volume_db;
 }
 
+void AudioHandler::AddVolumeObserver(VolumeObserver* observer) {
+  volume_observers_.AddObserver(observer);
+}
+
+void AudioHandler::RemoveVolumeObserver(VolumeObserver* observer) {
+  volume_observers_.RemoveObserver(observer);
+}
+
+AudioHandler::VolumeObserver::VolumeObserver() {
+  // AudioHandler should be initialized here if we are on the device, though
+  // the mixer may not have finished initializing yet.
+  DCHECK(AudioHandler::GetInstance() ||
+      !system::runtime_environment::IsRunningOnChromeOS());
+  if (AudioHandler::GetInstance())
+    AudioHandler::GetInstance()->AddVolumeObserver(this);
+}
+
+AudioHandler::VolumeObserver::~VolumeObserver() {
+  if (AudioHandler::GetInstance())
+    AudioHandler::GetInstance()->RemoveVolumeObserver(this);
+}
+
 }  // namespace chromeos