anchor.diff:    }
   
     void update() {
  -    if(object == null) return;
  +    if (object == null) return;
       var center = object.target;
       var position = object.position;
       var offset = position - center;
  
positive.code:       _state = STATE_ZOOM;
        _zoomStart.setValues(e.client.x.toDouble(), e.client.y.toDouble());
      }
      _mouseMoveSubscription = html.document.onMouseMove.listen(_onMouseMove);
      _mouseUpSubscription = html.document.onMouseUp.listen(_onMouseUp);
    }
  