Fix crash on audio settings change.

.vscode/settings.json

@@ -40,6 +40,7 @@
         "ratio": "cpp",
         "tuple": "cpp",
         "type_traits": "cpp",
-        "stdexcept": "cpp"
+        "stdexcept": "cpp",
+        "fstream": "cpp"
     }
 }

src/common/AudioQueue.cxx

@@ -132,3 +132,15 @@ Int16* AudioQueue::dequeue(Int16* fragment)
 
   return nextFragment;
 }
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void AudioQueue::closeSink(Int16* fragment)
+{
+  lock_guard<mutex> guard(myMutex);
+
+  if (myFirstFragmentForDequeue && fragment)
+    throw new runtime_error("attempt to return unknown buffer on closeSink");
+
+  if (!myFirstFragmentForDequeue)
+    myFirstFragmentForDequeue = fragment;
+}

src/common/AudioQueue.hxx

@@ -86,15 +86,21 @@ class AudioQueue
     Int16* enqueue(Int16* fragment = 0);
 
     /**
-     * Dequeue a fragment for playback and return the played fragment. This may
-     * return 0 if there is no queued fragment to return (in this case, the returned
-     * fragment is not enqueued and must be passed in the next invocation).
-     *
-     * @param fragment  The returned fragment. This must be empty on the first call (when
-     *                  there is nothing to return).
+       Dequeue a fragment for playback and return the played fragment. This may
+       return 0 if there is no queued fragment to return (in this case, the returned
+       fragment is not enqueued and must be passed in the next invocation).
+
+       @param fragment  The returned fragment. This must be empty on the first call (when
+                        there is nothing to return).
      */
     Int16* dequeue(Int16* fragment = 0);
 
+    /**
+      Return the currently playing fragment without drawing a new one. This is called
+      if the sink is closed and prepares the queue to be reopened.
+     */
+    void closeSink(Int16* fragment);
+
   private:
 
     // The size of an individual fragment (in stereo / mono samples)

src/common/SoundSDL2.cxx

@@ -143,6 +143,7 @@ void SoundSDL2::close()
 
   mute(true);
 
+  if (myAudioQueue) myAudioQueue->closeSink(myCurrentFragment);
   myAudioQueue = 0;
   myCurrentFragment = 0;