JComboBoxにAnimated GIFを表示する

private static ImageIcon makeImageIcon(URL url, final JComboBox combo, final int row) {
  ImageIcon icon = new ImageIcon(url);
  // Wastefulness: icon.setImageObserver(combo);
  icon.setImageObserver(new ImageObserver() {
    // @see http://www2.gol.com/users/tame/swing/examples/SwingExamples.html
    @Override public boolean imageUpdate(
        Image img, int infoflags, int x, int y, int w, int h) {
      if (combo.isShowing() && (infoflags & (FRAMEBITS | ALLBITS)) != 0) {
        if (combo.getSelectedIndex() == row) {
          combo.repaint();
        }
        BasicComboPopup p = (BasicComboPopup) combo.getAccessibleContext()
                                                   .getAccessibleChild(0);
        JList list = p.getList();
        if (list.isShowing()) {
          list.repaint(list.getCellBounds(row, row));
        }
      }
      return (infoflags & (ALLBITS|ABORT)) == 0;
    };
  });
  return icon;
}