Try to fix missing music after switching

m_current_music assignment should be done in sfx thread if music is on

src/audio/music_information.cpp

@@ -22,6 +22,7 @@
 #include <iostream>
 
 #include "audio/music_dummy.hpp"
+#include "audio/music_manager.hpp"
 #include "audio/music_ogg.hpp"
 #include "config/user_config.hpp"
 #include "io/file_manager.hpp"
@@ -143,6 +144,29 @@ void MusicInformation::addMusicToTracks()
     }
 }   // addMusicToTracks
 
+//-----------------------------------------------------------------------------
+/** Return false if it should not be started, done in sfx thread.
+ */
+bool MusicInformation::preStart()
+{
+    MusicInformation* old_mi = music_manager->m_current_music.load();
+    // If this music is already playing, ignore this call.
+    if (isPlaying() ||
+        (old_mi != NULL && old_mi == this && old_mi->isPlaying()))
+    {
+        return false;
+    }
+    // It is possible here that startMusic() will be called without first
+    // calling stopMusic(). This would cause a memory leak by overwriting
+    // m_current_music without first releasing its resources. Guard against
+    // this here by making sure that stopMusic() is called before starting
+    // new music.
+    if (old_mi)
+        old_mi->stopMusic();
+    music_manager->m_current_music.store(this);
+    return true;
+}   // preStart
+
 //-----------------------------------------------------------------------------
 /** Starts the music.
  */

src/audio/music_information.hpp

@@ -97,6 +97,8 @@ private:
     void   switchToFastMusic();
     void   setTemporaryVolume(float volume);
     // ------------------------------------------------------------------------
+    bool   preStart();
+    // ------------------------------------------------------------------------
     /** Sets the music to be waiting, i.e. startMusic still needs to be
     *  called. Used to pre-load track music during track loading time. */
     void setMusicWaiting() { m_music_waiting = true; }

src/audio/music_manager.cpp

@@ -175,24 +175,22 @@ void MusicManager::startMusic()
  */
 void MusicManager::startMusic(MusicInformation* mi, bool start_right_now)
 {
-    if (STKProcess::getType() != PT_MAIN)
+    if (STKProcess::getType() != PT_MAIN || !m_initialized)
         return;
 
-    // If this music is already playing, ignore this call.
-    if (m_current_music != NULL &&
-        m_current_music == mi &&
-        m_current_music->isPlaying())
+    if (!UserConfigParams::m_music)
+    {
+        // Save it so it can be turned on later in options menu
+        m_current_music = mi;
         return;
+    }
 
-    // It is possible here that startMusic() will be called without first
-    // calling stopMusic(). This would cause a memory leak by overwriting
-    // m_current_music without first releasing its resources. Guard against
-    // this here by making sure that stopMusic() is called before starting
-    // new music.
-    stopMusic();
-    m_current_music = mi;
-
-    if(!mi || !UserConfigParams::m_music || !m_initialized) return;
+    if (!mi)
+    {
+        // NULL music will stop current music
+        clearCurrentMusic();
+        return;
+    }
 
     SFXManager::get()->queue(start_right_now ? SFXManager::SFX_MUSIC_START
                                              : SFXManager::SFX_MUSIC_WAITING,

src/audio/music_manager.hpp

@@ -24,6 +24,7 @@
 #include "audio/music_information.hpp"
 #include "utils/no_copy.hpp"
 
+#include <atomic>
 #include <map>
 #include <string>
 #include <vector>
@@ -36,8 +37,9 @@ class Vec3;
   */
 class MusicManager : public NoCopy
 {
+friend class MusicInformation;
 private:
-    MusicInformation        *m_current_music;
+    std::atomic<MusicInformation*> m_current_music;
 
     /** If the sound could not be initialized, e.g. if the player doesn't has
      *  a sound card, we want to avoid anything sound related so we crash the

src/audio/sfx_manager.cpp

@@ -425,6 +425,8 @@ void SFXManager::mainLoop(void *obj)
         case SFX_UPDATE:     me->reallyUpdateNow(current);        break;
         case SFX_MUSIC_START:
         {
+            if (!current->m_music_information->preStart())
+                break;
             current->m_music_information->setDefaultVolume();
             current->m_music_information->startMusic();           break;
         }
@@ -445,6 +447,7 @@ void SFXManager::mainLoop(void *obj)
             mi->setTemporaryVolume(current->m_parameter.getX());  break;
         }
         case SFX_MUSIC_WAITING:
+               current->m_music_information->preStart();
                current->m_music_information->setMusicWaiting();   break;
         case SFX_MUSIC_DEFAULT_VOLUME:
         {