NSMenuFX with popup

package de.jangassen.nsmenufx.samples;

import de.jangassen.MenuToolkit;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Menu;
import javafx.scene.control.MenuBar;
import javafx.scene.control.MenuItem;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Popup;
import javafx.stage.Stage;

public class AboutMenu extends Application {

  @Override
  public void start(Stage primaryStage) {

    Popup popup = new Popup();
    popup.setX(300);
    popup.setY(200);
    popup.getContent().addAll(new Circle(25, 25, 50, Color.AQUAMARINE));

    Button show = new Button("Show");
    show.setOnAction(event -> popup.show(primaryStage));

    primaryStage.setScene(new Scene(new StackPane(show), 300, 200));
    primaryStage.show();
    MenuToolkit tk = MenuToolkit.toolkit();

    Menu applicationMenu = tk.createDefaultApplicationMenu("MyApp");

    MenuBar bar = new MenuBar();
    bar.getMenus().add(applicationMenu);
    tk.setMenuBar(bar);

    Menu menu = new Menu("test");
    MenuItem myItem = new MenuItem("Hallo welt");
    menu.getItems().add(myItem);
    tk.setDockIconMenu(menu);
  }
}