JavaFX popup hidden when stage is in fullscreen mode

Question

I am trying to popup a dialog over my fullscreen primary stage in javafx. When I create my popup, it is unexpectedly hidden behind my fullscreen primary stage until the stage is removed from fullscreen mode (via ESC). If I make my primary stage maximized and undecorated instead of fullscreen, then my popup will appear on top of the primary stage as expected.

Am I missing something about how fullscreen mode is different than maximized and undecorated mode? Am I using fullscreen mode improperly?

I am using java version 1.8.0_20 on CentOS 6.5 with Gnome.

Here is my SSCCE:

import javafx.application.*;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.stage.*;

public class TestApplication extends Application {
    private Stage primaryStage;

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

    public void start(Stage stage) {
        this.primaryStage = stage;

        // Create a fullscreen primary stage.    
        primaryStage.setTitle("Main Stage");
        primaryStage.setScene(new Scene(createRoot()));
        primaryStage.setFullScreen(true);

        primaryStage.show();
    }       

    private Parent createRoot() {
        Button button = new Button("Show popup");
        button.setOnAction((event) -> showPopup());

        return button;
    }

    private void showPopup() {
        // Create a popup that should be on top of the primary stage.
        Stage popupStage = new Stage();

        popupStage.setScene(new Scene(createPopupRoot()));
        popupStage.setTitle("Popup Stage");
        popupStage.initModality(Modality.WINDOW_MODAL);
        popupStage.initOwner(primaryStage);

        popupStage.show();
    }

    private Parent createPopupRoot() {
        return new Label("This is a popup!");
    }
}

Answer 1

After repeating this problem with java version '1.8.0_40', I finally found how to fix this problem!

popupStage.initStyle(StageStyle.UTILITY);

Stage.initStyle(StageStyle) -- JavaFX 8

Giving the popup a style of StageStyle.UTILITY seems to keep the popup in front of the fullscreen window even when clicking outside of the popup.

I saw this same issue when using the new Alert class in java 1.8.0_40, and setting the style to StageStyle.UTILITY fixed that as well (Dialog.initStyle(StageStyle) -- JavaFX 8).

I don't know why this works.

Side Note:

It looks like removing the call to popupStage.initOwner(...) allows the popup to appear above the full screen application, but clicking outside of the popup causes the popup to disappear.