code: @Override
  	public void add(final WComponent component) {
  		getCardContainer().add(component);
  		CardManagerModel model = getComponentModel();
  
  		if (model.visibleComponent == null) {
  			model.visibleComponent = component;
  		}
  	}
docs: Override add so that components are added to the (invisible) container.
  
  @param component the component to add.