static JButton jPopDownButton(S text, fO... menuParams) {
  ret jbutton(text + " " + unicode_downPointingTriangle(), r {
    new JPopupMenu menu;
    int emptyCount = menu.getComponentCount();
    fillJPopupMenu(menu, menuParams);
    if (menu.getComponentCount() != emptyCount) {
      JButton btn = heldInstance(JButton);
      menu.show(btn, 0, btn.getHeight());
    }
  });
}