Utils.getScreen() doesn't handle the case when scene is not added to any Window. The test below throws the following exception:

java.lang.NullPointerException
    at com.sun.javafx.Utils.getOffsetX(Utils.java:645)
    at com.sun.javafx.Utils.getScreen(Utils.java:778)
    at Test.start(Test.java:22)

caused by the following code in Utils.getOffsetX():
            return scene.getX() + scene.getWindow().getX();


The test is

import com.sun.javafx.Utils;
import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;


public class Test extends Application {
    
    public static void main(String[] args) {
        Application.launch(Test.class, args);
    }

    @Override public void start(Stage stage) {
        Rectangle r = new Rectangle();
        Scene sc = new Scene(new Group(r));
        System.out.println(Utils.getScreen(r));
    }
}