When using the CrossfadeTransport, fade music out if stopped (or the app is exited).

src/core/audio/CrossfadeTransport.cpp

@@ -61,6 +61,7 @@ CrossfadeTransport::CrossfadeTransport()
 
 CrossfadeTransport::~CrossfadeTransport() {
     this->Stop();
+    this->crossfader.Drain();
 }
 
 PlaybackState CrossfadeTransport::GetPlaybackState() {
@@ -93,9 +94,8 @@ void CrossfadeTransport::ReloadOutput() {
 void CrossfadeTransport::Stop() {
     {
         Lock lock(this->stateMutex);
-        this->crossfader.Stop();
-        this->active.Stop();
-        this->next.Stop();
+        this->active.Reset();
+        this->next.Reset();
     }
 
     this->SetPlaybackState(PlaybackStopped);

src/core/audio/Crossfader.cpp

@@ -125,6 +125,18 @@ void Crossfader::Stop() {
     this->contextList.clear();
 }
 
+void Crossfader::Drain() {
+    LOCK(this->contextListLock);
+
+    if (this->contextList.size()) {
+        for (FadeContextPtr context : this->contextList) {
+            context->direction = FadeOut;
+        }
+
+        this->drainCondition.wait(lock);
+    }
+}
+
 void Crossfader::OnPlayerDestroying(Player* player) {
     if (player) {
         LOCK(this->contextListLock);
@@ -269,6 +281,7 @@ void Crossfader::ProcessMessage(IMessage &message) {
             }
             else {
                 this->Emptied();
+                this->drainCondition.notify_all();
             }
         }
         break;

src/core/audio/Crossfader.h

@@ -72,6 +72,7 @@ namespace musik { namespace core { namespace audio {
             void Pause();
             void Resume();
             void Stop();
+            void Drain();
 
         private:
             void ThreadLoop();
@@ -96,6 +97,7 @@ namespace musik { namespace core { namespace audio {
             musik::core::runtime::MessageQueue messageQueue;
             std::list<FadeContextPtr> contextList;
             std::atomic<bool> quit, paused;
+            std::condition_variable_any drainCondition;
             ITransport& transport;
     };