static JPanel leftAlignedButtons(O... params) {
  new L<JComponent> l;
  for (int i = 0; i < l(params); i += 2)
    if (params[i] != null)
      if (params[i] instanceof JComponent)
        l.add((JComponent) params[i--]);
      else
        l.add(jbutton((S) params[i], params[i+1]));
  ret jline(l);
}