sclass DynamicVStack extends JPanel {
  int spacing = 10;
  
  *() {
    super(new GridBagLayout);
    add(jrigid(), gridBagConstraints_vstack_rest());
  }

  void addComponent(final Component c) {
    swing {
      add(c, gridBagConstraints_vstack_1(spacing), getComponentCount()-1);
      revalidate();
    }
  }
}