// c = JComponent or something implementing swing()
static JComponent wrap(O swingable) {
  JComponent c = cast swingable instanceof JComponent ? swingable : callOpt(swingable, "swing");
  if (c instanceof JTable || c instanceof JList
    || c instanceof JTextArea || c instanceof JEditorPane
    || c instanceof JTextPane)
    ret new JScrollPane(c);
  ret c;
}