sclass JForm is Swingable {
  new L parts;
  new FormLayout1 layout;
  JPanel panel;
  
  // called after form is submitted. can set after form is generated
  settable IVF1<Component> frameCloser;
  
  *(O... parts) { this.parts = asList(parts); }
  
  cachedVisual
    panel = jpanel(layout,
      showForm_arrange1(showForm_makeComponents(
        c -> frameCloser?.get(c),
        flattenToArray(parts))));
}