Toolkit tk = Toolkit.getDefaultToolkit();
Insets insets = tk.getScreenInsets(GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration());
Dimension size = tk.getScreenSize();
stage.setUndecorated(true);
final JFrame frame = (JFrame) stage.getNativeWindow();
undoFullscreen = new Callback() {
public void call(Object event) {
stage.setUndecorated(false);
frame.setLocation(oldLocation);
frame.setSize(oldSize);
}