// layouter: voidfunc(Container) or func(Container) -> Dimension
// (return value is preferred size)
static JPanel customLayoutPanel(fO layouter) {
  ret jpanel(layoutManagerFromFunction(layouter));
}

static JPanel customLayoutPanel(fO layouter, fL<? extends Component> components) {
  final JPanel panel = customLayoutPanel(layouter);
  if (nempty(components)) swing {
    panel.addAll(components);
  }
  ret panel;
}