Change Sound::Event::PlayMusic to handle crossfading.

Consolidating all the stop/play/fade operations will allow the number of
mutex locks to be reduced in the future.

src/sound/Sound.cpp

@@ -702,12 +702,23 @@ namespace Sound {
 		}
 	}
 
-	void Event::PlayMusic(const char *fx, const float volume_left, const float volume_right, Op op)
+	void Event::PlayMusic(const char *fx, float volume, float fadeDelta, bool repeat, Event* fadeOut)
 	{
+		// The FadeOut, Stop, PlayMusicSample & VolumeAnimate calls perform
+		// five mutex lock operations. These could be reduced to a single
+		// lock/unlock if this were re-written.
+
+		if (fadeOut) {
+			fadeOut->FadeOut(fadeDelta);
+		}
 		Stop();
 		Sample* sample = GetSample(fx);
 		if (sample) {
-			eid = PlayMusicSample(sample, volume_left, volume_right, op);
+			float start = fadeDelta ? 0.0f : volume;
+			eid = PlayMusicSample(sample, start, start, repeat ? Sound::OP_REPEAT : 0);
+			if (fadeDelta) {
+				VolumeAnimate(volume, volume, fadeDelta, fadeDelta);
+			}
 		}
 	}
 

src/sound/Sound.h

@@ -25,7 +25,7 @@ namespace Sound {
 			eid(0) {}
 		void Play(const char *fx, const float volume_left, const float volume_right, Op op);
 		void Play(const char *fx) { Play(fx, 1.0f, 1.0f, 0); }
-		void PlayMusic(const char *fx, const float volume_left, const float volume_right, Op op);
+		void PlayMusic(const char *fx, float volume, float fadeDelta, bool repeat, Event* fadeOut = nullptr);
 		bool Stop();
 		bool IsPlaying() const;
 		bool SetOp(Op op);

src/sound/SoundMusic.cpp

@@ -39,20 +39,18 @@ namespace Sound {
 	void MusicPlayer::Play(const std::string &name, const bool repeat /* = false */, const float fadeDelta /* = 1.f */)
 	{
 		if (!m_enabled) return;
-		Sound::Op op = 0;
-		if (repeat)
-			op |= Sound::OP_REPEAT;
+
+		Event *current, *next;
 		if (m_eventOnePlaying) {
-			m_eventOne.FadeOut(fadeDelta);
-			m_eventTwo.PlayMusic(name.c_str(), 0.f, 0.f, op);
-			m_eventTwo.VolumeAnimate(m_volume, m_volume, fadeDelta, fadeDelta);
 			m_eventOnePlaying = false;
+			current = &m_eventOne;
+			next = &m_eventTwo;
 		} else {
-			m_eventTwo.FadeOut(fadeDelta);
-			m_eventOne.PlayMusic(name.c_str(), 0.f, 0.f, op);
-			m_eventOne.VolumeAnimate(m_volume, m_volume, fadeDelta, fadeDelta);
 			m_eventOnePlaying = true;
+			current = &m_eventTwo;
+			next = &m_eventOne;
 		}
+		next->PlayMusic(name.c_str(), m_volume, repeat, fadeDelta, current);
 		m_playing = true;
 		m_currentSongName = name;
 	}