// action: voidfunc(S item)
static JList listPopupMenuItemsThreaded(final JList list, O... params) {
  for (int i = 0; i+1 < l(params); i += 2) {
    if (isMenuSeparatorIndicator(params[i])) continue with --i;
    fO action = params[i+1];
    listPopupMenuItem(list, str(params[i]), voidfunc(fS item) {
      thread-messagebox {
        callF(action, item);
      }
    });
  }
  ret list;
}