It seems that the XP Menus are currently unable to extend beyond the main window if it is too small to contain them. The GTK+ port on the other hand, does handle this, so I assume Xlib should be able to as well.
This is because the xlib port still creates the menu windows as children of the parent window instead of creating an override redirect window like it should. Once ICCCM code is in place I can fix this problem. I've added the dependency.
Please ignore the spam. Changing address.
bustage from my reassign