JScrollPaneからあふれるJListのアイテムをフェイドアウト表示する

class FadeScrollLayerUI extends LayerUI<JScrollPane> {
  public static final int OVERFLOW = 32;

  @Override public void paint(Graphics g, JComponent c) {
    super.paint(g, c);
    Graphics2D g2 = (Graphics2D) g.create();
    g2.setRenderingHint(
        RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
    g2.setPaint(new Color(0x12_FF_FF_FF, true));
    if (c instanceof JLayer) {
      JScrollPane scroll = (JScrollPane) ((JLayer<?>) c).getView();
      Rectangle r = scroll.getViewportBorderBounds();
      BoundedRangeModel m = scroll.getVerticalScrollBar().getModel();
      g2.setClip(r);
      if (m.getMinimum() < m.getValue()) {
        for (int i = OVERFLOW; i > 0; i--) {
          g2.fillRect(0, r.y - i, r.width, OVERFLOW - i);
        }
      }
      if (m.getValue() + m.getExtent() < m.getMaximum()) {
        g2.translate(r.x, r.y + r.height - OVERFLOW);
        for (int i = 0; i < OVERFLOW; i++) {
          g2.fillRect(0, i, r.width, OVERFLOW - i);
        }
      }
    }
    g2.dispose();
  }
}