Using a timer

The periodic timer in Dart should be a familiar friend of yours by now. This is used to check whether the slide has reached the final position. If it is not there yet, then the position is updated:

    new Timer.periodic(new Duration(milliseconds: 50), (timer) {
      if (isFullScreen && liveSlideY < 0) {
        liveSlide.style.top = liveSlideY.toString() + "px";
        liveSlideY += 50;
      }
    });

You may be concerned that the Timer object runs all the time, even when a presentation is not running fullscreen. In reality, they are very lightweight and the work that the animation performs is so minimal that it will have a negligible impact.