XmMegaButtonWidget allows menu with a scrolling array of menu buttons as on other windowing systems. When the number of items in the xmMegaButtonWidget becomes greater than the XmNvisibleItemCount up and down arrows become visible at the top and bottom respectively of the widget. If not the widget looks like an ordinary menu, apart from being one widget, the advantage being that you can have a menu with thousands of choices but only the the overhead of one widget.
