Is there a way to limit the number of top level items in a custom menu?

Question

I wish to implement the wordpress 3 menus API in a client site, but the designs has restraint on the width of the top level menu items. How can I be sure the client won't exceed that limit?

Answer 1

The easiest way to accomplish this would be to filter wp_nav_menu_items or more precisely wp_nav_menu_{$menu->slug}_items and cut extra items from output.

It would probably me more pretty and proper to limit/warn user in admin area, but at moment I have no remote idea where to start with that. I should learn up on admin side some time. :)