code: protected void render() {
  		if (graphicsHandler.getHandlerGroup() != null) {
  			invisibleClickArea = createInvisibleMask();
  			invisibleClickArea.addDoubleClickHandler(this);
  			invisibleClickArea.addClickHandler(this);
  			invisibleClickArea.addMouseDownHandler(this);
  			invisibleClickArea.addMouseUpHandler(this);
  			invisibleClickArea.addMouseMoveHandler(this);
  		}
  	}
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