// if f returns true, form is hidden
static void disableButtonWhileCalcing2(final O /*F0<Bool>*/ f) {
  final JButton button = heldInstance(JButton);
  disableButton(button);
  thread {
    try {
      bool ok = isTrue(callF(f));
      if (ok) disposePossiblyInternalFrame(button);
    } finally {
      enableButton(button);
    }
  }
}