anchor.diff:   * an Outgoing [Scene].
    */
   abstract class TransitionScene extends Scene {
  +//  StreamSubscription _busSubscription;
  +
     Scene inScene;
     Scene outScene;
     double duration;
  
positive.code:   void onExit() {
      super.onExit();
  
      // TODO INPUT Enable events during transitions
  
      outScene.onExit();
  
negative.code:     // a EventBus call instead.
      Scheduler scheduler = Application.instance.scheduler;
      scheduler.scheduleUpdateTarget(_setNewScene, 0.0, Timer.REPEAT_FOREVER, 0.0, !isRunning);
      
  //    Application.instance.eventBus.fire(this);
  
    }
    
    // UpdateTarget callback
  