MarkupStream markupStream = new MarkupStream(markup);
// Flag: we stated the render process
markRendering(true);
MarkupElement elem = markup.get(0);
if (elem instanceof ComponentTag)
{
// Guarantee that the markupStream is set and determineVisibility not yet tested
// See WICKET-2049
((ComponentTag)elem).onBeforeRender(this, markupStream);