// c = JComponent or something implementing swing()
static JComponent wrap(O swingable) {
  if (swingable == null) null;
  JComponent c;
  if (swingable instanceof JComponent) c = (JComponent) swingable;
  ifclass Swingable
    else if (swingable instanceof Swingable) c = swingable/Swingable.visualize();
  endif
  else c = (JComponent) callOpt(swingable, "swing");
  if (c instanceof JTable || c instanceof JList
    || c instanceof JTextArea || c instanceof JEditorPane
    || c instanceof JTextPane || c instanceof JTree)
    ret jscroll(c);
  ret c == null ? jlabel(str(swingable)) : c;
}