// use setForeground and setBackground for the colors
// TODO: repaint more sparingly
sclass JColorBar > JComponentWithChangeListeners {
  settableWithVar double value;
  settableWithVar double max = 100;
  
  *() {
    setForeground(Color.red);
    for (var : ll(varValue(), varMax()))
      var.onChange(l0 repaint);
    jMinSize(50, 10, this);
  }

  public void paintComponent(Graphics g) {
    super.paintComponent(g); // paint background
    int w = getWidth(), h = getHeight();
    fillRect(g, 0, 0, iround(w*clampZeroToOne(doubleRatio(value, max))), h, getForeground());
  }
}