Improve audio and volume handling.

Prevent a deadlock in AudioManager mixer callback when stopping sounds.
Detach and free mixer handle before closing it in
VolumeControl::deinit().

src/AudioManager.cpp

@@ -28,17 +28,13 @@ void AudioManager::mixAudio(void *unused, Uint8 *stream, int len)
 			}
 			//mix sample into stream
 			SDL_MixAudio(stream, &(sound->getData()[sound->getPosition()]), restLength, SDL_MIX_MAXVOLUME);
-			if (sound->getPosition() + restLength >= sound->getLength())
-			{
-				//if the position is beyond the end of the buffer, stop playing the sample
-				sound->stop();
-			}
-			else 
+			if (sound->getPosition() + restLength < sound->getLength())
 			{
 				//sample hasn't ended yet
-				sound->setPosition(sound->getPosition() + restLength);
 				stillPlaying = true;
 			}
+			//set new sound position. if this is at or beyond the end of the sample, it will stop automatically
+			sound->setPosition(sound->getPosition() + restLength);
 		}
 		//advance to next sound
 		++soundIt;

src/Sound.cpp

@@ -82,18 +82,19 @@ void Sound::play()
 	if(mSampleData == NULL)
 		return;
 
+	SDL_LockAudio();
 	if (playing)
 	{
 		//replay from start. rewind the sample to the beginning
-		SDL_LockAudio();
 		mSamplePos = 0;
-		SDL_UnlockAudio();
+		
 	}
 	else
 	{
 		//flag our sample as playing
 		playing = true;
 	}
+	SDL_UnlockAudio();
 	//tell the AudioManager to start playing samples
 	AudioManager::getInstance()->play();
 }
@@ -126,6 +127,8 @@ void Sound::setPosition(Uint32 newPosition)
 {
 	mSamplePos = newPosition;
 	if (mSamplePos >= mSampleLength) {
+		//got to or beyond the end of the sample. stop playing
+		playing = false;
 		mSamplePos = 0;
 	}
 }

src/VolumeControl.cpp

@@ -215,6 +215,8 @@ void VolumeControl::deinit()
 	#error TODO: Not implemented for MacOS yet!!!
 #elif defined(__linux__)
 	if (mixerHandle != nullptr) {
+		snd_mixer_detach(mixerHandle, mixerCard);
+		snd_mixer_free(mixerHandle);
 		snd_mixer_close(mixerHandle);
 		mixerHandle = nullptr;
 		mixerElem = nullptr;