static JSlider liveSlider(int min, int max, int value, IVF1<Int> onChange) {
  ret swing(() -> {
    JSlider slider = new JSlider(min, max, value);
    slider.addChangeListener(new ChangeListener {
      int lastValue = slider.getValue();
      public void stateChanged(ChangeEvent e) {
        int value = slider.getValue();
        if (value != lastValue) {
          lastValue = value;
          setToolTip(slider, str(value));
          pcallF(onChange, value);
        }
      }
    });
    ret slider;
  });
}