Swing/ComboItemHeight のバックアップ(No.5)

JComboBox combo1 = new JComboBox(items);
JLabel renderer1 = (JLabel) combo1.getRenderer();
renderer1.setPreferredSize(new Dimension(0, 32));

JComboBox combo2 = new JComboBox(items);
final ListCellRenderer r = combo2.getRenderer();
final Dimension dim = ((JLabel) r).getPreferredSize();
combo2.setRenderer(new ListCellRenderer() {
  @Override public Component getListCellRendererComponent(
        JList list, Object value, int index,
        boolean isSelected, boolean cellHasFocus) {
    Component c = r.getListCellRendererComponent(
      list, value, index, isSelected, cellHasFocus);
    c.setPreferredSize(new Dimension(100, (index < 0) ? dim.height : 32));
    return c;
  }
});