static int withMargin_defaultWidth = 6;

static JPanel withMargin(Component c) {
  ret withMargin(withMargin_defaultWidth, c);
}

static JPanel withMargin(final int w, final Component c) {
  ret swing(func -> JPanel {
    JPanel p = new JPanel(new BorderLayout);
    int w = withMargin_defaultWidth;
    p.setBorder(BorderFactory.createEmptyBorder(w, w, w, w));
    p.add(c);
    ret p;
  });
}