anchor.diff:    void zoomBy(double delta) {
       scale.setValues(scale.x + delta, scale.y + delta);
       _zoomDirty = true;
  +    Ranger.Application.instance.eventBus.fire(this);
  +
       _updateMatrix();
     }
     
  
positive.code:  */
  class ZoomGroup extends Ranger.GroupNode with UTE.Tweenable {
    static const int TWEEN_SCALE = 1;
  
    bool _zoomDirty = true;
    Vector2 scaleCenter = new Vector2.zero();
  
negative.code:     switch(tweenType) {
        case TWEEN_SCALE:
          currentScale = newValues[0];
          break;
        case TRANSLATE_XY:
          position.x = newValues[0];
          position.y = newValues[1];
          dirty = true;
          break;
      }
    }
  