static void calAddAutoLayoutSwitch(CirclesAndLines cal, final Canvas canvas, bool on) {
  calAddAutoLayoutSwitch(new Var(cal), canvas, on);
}

static void calAddAutoLayoutSwitch(final Var<CirclesAndLines> cal, final Canvas canvas, bool on) {
  final new Var<Timer> timer;
  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, new Runnable {
      CALSpringLayout layout = new(cal!);
      CirclesAndLines lastCAL = cal!;
      
      public void run() {
        if (cal! != lastCAL) {
          lastCAL = cal!;
          layout = new CALSpringLayout(cal!);
        }
        layout.step();
        updateCanvas(canvas);
      }
    }));
  })));
  if (on) r.run();
}