Swing/ComboBoxForceOpaque のバックアップ(No.1)

UIManager.put("ComboBox.forceOpaque", Boolean.FALSE);
Insets ins = UIManager.getInsets("ComboBox.padding");
ins.right = 0;
UIManager.put("ComboBox.padding", ins);
// ...
JComboBox<String> comboBox = new JComboBox<>(MODEL);
comboBox.setForeground(Color.WHITE);
comboBox.setBackground(BACKGROUND);
UIDefaults d1 = new UIDefaults();
d1.put("ComboBox:\"ComboBox.listRenderer\".background", BACKGROUND);
d1.put("ComboBox:\"ComboBox.listRenderer\".textForeground", Color.WHITE);
d1.put("ComboBox:\"ComboBox.listRenderer\"[Selected].background", Color.LIGHT_GRAY);
d1.put("ComboBox:\"ComboBox.listRenderer\"[Selected].textForeground", Color.BLACK);
// d1.put("ComboBox:\"ComboBox.listRenderer\".opaque", Boolean.TRUE);
ListCellRenderer<? super String> renderer = comboBox.getRenderer();
if (renderer instanceof JComponent) {
  putClientProperty((JComponent) renderer, d1);
}
// ...
private static final class ComboRenderer extends DefaultListCellRenderer {
  @Override public Component getListCellRendererComponent(
      JList<?> list, Object value, int index, boolean isSelected, boolean cellHasFocus) {
    list.setBackground(BACKGROUND);
    list.setForeground(Color.WHITE);
    list.setSelectionBackground(Color.LIGHT_GRAY);
    list.setSelectionForeground(Color.BLACK);
    return super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
  }
}
// ...
private static JComboBox<String> makeComboBox2() {
  return new JComboBox<String>(MODEL) {
    @Override public void updateUI() {
      setRenderer(null);
      super.updateUI();
      ListCellRenderer<? super String> r = getRenderer();
      setRenderer((list, value, index, isSelected, cellHasFocus) -> {
        Component c = r.getListCellRendererComponent(
            list, value, index, isSelected, cellHasFocus);
        ((JComponent) c).setOpaque(true);
        return c;
      });
      ComboPopup popup = (ComboPopup) getAccessibleContext().getAccessibleChild(0);
      JList<?> list = popup.getList();
      list.setBackground(BACKGROUND);
      list.setForeground(Color.WHITE);
      list.setSelectionBackground(Color.LIGHT_GRAY);
      list.setSelectionForeground(Color.BLACK);
      setBackground(BACKGROUND);
    }
  };
}