code: public void push(AbstractDrawer drawer, AjaxRequestTarget target, String cssClass) {
  		ListItem item = new ListItem("next", drawer, this, cssClass);
  
  		drawers.push(item);
  		if (first == null) {
  			first = item;
  			addOrReplace(first);
  		} else {
  			ListItem iter = first;
  			while (iter.next != null) {
  				iter = iter.next;
  			}
  			iter.add(item);
  		}
  
  		if (target!=null) {
  			target.add(item);
  
  			target.appendJavaScript("$('#"+item.item.getMarkupId()+"').modaldrawer('show');");
  			if (item.previous!=null) {
  				target.appendJavaScript("$('#"+item.previous.item.getMarkupId()+"').removeClass('shown-modal');");
  				target.appendJavaScript("$('#"+item.previous.item.getMarkupId()+"').addClass('hidden-modal');");
  			}
  
  		}
  		drawer.setManager(this);
  	}
docs: Push and display a drawer on the page during an AJAX request,
  and inject an optional CSS class onto the drawer's immediate container.
  
  @param drawer
  The drawer to be pushed. Cannot be null.
  @param target
  The current AJAX target.
  @param cssClass
  The name of the class to be injected.