o groups called menu bars
that allow scanning:
if the mouse button is pressed over one menubutton (causing it
to post its menu) and the mouse is moved over another menubutton
in the same menu bar without releasing the mouse button, then the
menu of the first menubutton is unposted and the menu of the
new menubutton is posted instead.
<I>This use is deprecated</I> in favor of setting a <B><A HREF="menu.html">menu</A></B> directly as a
menubar; see the <B><A HREF="toplevel.html">toplevel</A></B>'s <B>-menu</B