static JWindow makeUnimportantWindow(Component c) {
  swing {
    Map map = cast vm_generalMap_get("unimportant windows");
    if (map == null)
      vm_generalMap_put("unimportant windows", map = callJavaX('newWeakHashMap()));
    JWindow w = makeWindow(c);
    map.put(w, true);
    ret w;
  }
}