static JInternalFrame centerInternalFrame(JInternalFrame f) {
  Container c = f.getParent();
  if (c != null) {
    print("Container type: " + className(c) + ", bounds: " + c.getBounds());
    f.setLocation((c.getWidth()-f.getWidth())/2, (c.getHeight()-f.getHeight())/2);
  }
  ret f;
}