Alt functionality on menus

Question

I'm implementing a main menu and wondering if the functionality I'm getting is normal or I'm missing something. Our QA team brought this up.
On a typical Windows application when I click Alt-F (assuming I have a _File menu), it shows the complete File menu (i.e. shows all subitems below the word File).
On my JavaFX application, if I click Alt-F, it highlights the File menu, but doesn't show child items unless I click the Down button
Is there a way to ensure the complete File menu opens when clicking Alt-F?

Answer 1

This isn't a problem with Mnemonic parsing, this is a problem with how the menu responds to the parsing.
I've put an example below. In this example I have one menu (_Items) with three menu items (Item A, Item B, Item _C). When I click Alt+I, I would expect it to pop open the Items menu and show the three menu items.
Unfortunately, it just highlights the Items menu header, and I don't see the menu items unless I press the Down key. This is not typical menu behavior.
Am I missing something or is this a bug with JavaFX menus?
public class JavaFXApplication1 extends Application {
    public static void main(String[] args) {
        Application.launch(args);
    @Override public void start(Stage stage) {
        MenuItem itemA = new MenuItem("Item _A");
        MenuItem itemB = new MenuItem("Item _B");
        MenuItem itemC = new MenuItem("Item _C");
        Menu items = new Menu("_Items");
        items.getItems().addAll(itemA, itemB, itemC);
        MenuBar bar = new MenuBar();
        bar.getMenus().add(items);
        VBox vp = new VBox();
        vp.getChildren().addAll(bar);
        stage.setScene(new Scene(vp, 300, 300));
        stage.show();
}