public DefaultSize getSize() {
/*
* If the popup panel is not attached --> attach in background, get
* size, remove panel. Otherwise just report size.
*/
NEffectPanel effectPanel = getEffectPanel();
boolean attached = effectPanel.isAttached(); // do not inline
if (!attached) {
Style style = effectPanel.getElement().getStyle();
style.setProperty(CSS.POSITION, CSS.FIXED);
style.setProperty(CSS.Z_INDEX, Integer.toString(HIDDEN_Z_INDEX));
rootPanel.add(effectPanel);
}