Merge branch 'v0.21.x' into master

src/player/Thread.cxx

@@ -443,7 +443,7 @@ Player::ActivateDecoder() noexcept
 	pc.audio_format.Clear();
 
 	{
-		/* call syncPlaylistWithQueue() in the main thread */
+		/* call playlist::SyncWithPlayer() in the main thread */
 		const ScopeUnlock unlock(pc.mutex);
 		pc.listener.OnPlayerSync();
 	}
@@ -684,6 +684,12 @@ Player::SeekDecoder(std::unique_lock<Mutex> &lock) noexcept
 	/* re-fill the buffer after seeking */
 	buffering = true;
 
+	{
+		/* call syncPlaylistWithQueue() in the main thread */
+		const ScopeUnlock unlock(pc.mutex);
+		pc.listener.OnPlayerSync();
+	}
+
 	return true;
 }
 
@@ -1175,6 +1181,11 @@ try {
 			{
 				const ScopeUnlock unlock(mutex);
 				do_play(*this, dc, buffer);
+
+				/* give the main thread a chance to
+				   queue another song, just in case
+				   we've stopped playback
+				   spuriously */
 				listener.OnPlayerSync();
 			}