public static UserAction show(Window owner) {
    final Region root;
    try {
      root = FXMLLoader.load(PosApplication.class.getResource("MessageBox.fxml"));
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
    MessageBox messageBox = new MessageBox();
    messageBox.initModality(Modality.APPLICATION_MODAL);
    messageBox.initOwner(owner);
    messageBox.initStyle(StageStyle.TRANSPARENT);
    StageBuilder.create()
        .scene(SceneBuilder.create()
            .root(root).build())
        .applyTo(messageBox);
    messageBox.showAndWait();

    UserAction userAction = messageBox.userAction;
    messageBox = null;

    return userAction;
  }