public void destroy(Widget w) {
	    int id;
	    if(!rwidgets.containsKey(w))
		id = -1;
	    else
		id = rwidgets.get(w);
	    synchronized(robots) {
		for(Robot r : robots)
		    r.dstwdg(id, w);
	    }
	    super.destroy(w);
	}