import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.Menu;
import javafx.scene.control.MenuBar;
import javafx.scene.control.MenuItem;
import javafx.scene.layout.Priority;
import javafx.scene.layout.VBox;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class PopupTest extends Application {

    private final Label label = new Label("Miracles don’t happen.");

    @Override
    public void start(Stage stage) {
        MenuItem item = new MenuItem("Click me!");
        item.setOnAction(e -> {
            label.setText("It’s a miracle!");
        });
        Menu menu = new Menu("Menu");
        menu.getItems().add(item);
        MenuBar bar = new MenuBar(menu);

        var stackPane = new StackPane(label);
        VBox.setVgrow(stackPane, Priority.ALWAYS);
        label.setStyle("-fx-font-size: 30");
        VBox root = new VBox(bar, stackPane);

        Scene scene = new Scene(root, 400, 400);
        stage.setScene(scene);
        stage.setTitle("JDK-8371781");
        stage.show();
    }

    public static void main(String[] args) {
        launch();
    }
}