static void calAddAutoLayoutSwitch(CirclesAndLines cal, final Canvas canvas, bool on) {
  final new Var<Timer timer;
  final CALSpringLayout layout = new(cal);
  Runnable r;
  addToWindow(canvas, jcenteredline(onChange(jcheckbox("Auto-Layout"), r = r {
    if (timer.has()) { cancelTimer(timer!); timer.set(null); }
    else timer.set(awtCalcEvery2(canvas, 100, r {
      layout.step();
      updateCanvas(canvas);
    }));
  })));
  if (on) r.run();
}