How to reproduce a Window with native background?

[Thiago Milczarek Sayao]

>From Window.java internal API:


/**
 * Set the background of the window.
 *
 * In most cases the View covers the whole window, so the background color
 * of the window is never seen by the user. However, a window w/o a view
 * does display the background color in its content area.
 *
 * On some platforms setting the background color may produce flickering
 * when painting the content area of the View (even though the View covers
 * the whole window).  Therefore it is recommended to set the background
 * color to windows w/o views only.
 */
public boolean setBackground(final float r, final float g, final float b) {
    Application.checkEventThread();
    checkNotClosed();
    return _setBackground(this.ptr, r, g, b);
}

How to reproduce this scenario? Create a window where this brackground is shown?

Thanks.