// assumes frame is supposed to be visible right now
svoid waitForFrameClose(JFrame f) {
  new Var<Flag> flag;
  new CloseablesHolder closer;
  
  swing {
    if (!isVisible(f)) ret;
    flag.set(new Flag);
    closer.add(tempOnFrameClose(f, flag->raise()));
  }
  
  temp closer;
  if (flag.has()) flag->waitUntilUp();
}