/** Creates an empty popup panel. A child widget must be added to it before it is shown. */
public PopupPanel() {
super();
super.getContainerElement().appendChild(impl.createElement());
// Default position of popup should be in the upper-left corner of the
// window. By setting a default position, the popup will not appear in
// an undefined location if it is shown before its position is set.
setPopupPosition(0, 0);
setStyleName(DEFAULT_STYLENAME);
setStyleName(getContainerElement(), "popupContent");
}
