viewer: improved playback ux

app/widget/viewer/viewer.h

@@ -254,7 +254,7 @@ private:
 
   PreviewAutoCacher auto_cacher_;
 
-  int active_queue_jobs_;
+  QVector<RenderTicketWatcher*> queue_watchers_;
 
   std::shared_ptr<PreviewAudioDevice> audio_playback_device_;
   std::list<RenderTicketWatcher*> audio_playback_queue_;
@@ -317,6 +317,8 @@ private slots:
 
   void ReceivedAudioBufferForScrubbing();
 
+  void ForceRequeueFromCurrentTime();
+
 };
 
 }