ssing
mouse button 1 over the menubutton causes the associated menu to
be posted just underneath the menubutton.  If the mouse is moved over
the menu before releasing the mouse button, the button release
causes the underlying menu entry to be invoked.  When the button
is released, the menu is unposted.
<P>
Menubuttons are used to construct a <B>tk_optionMenu</B>, which is the
preferred mechanism for allowing a user to select one item from a list
on Mac OS X.
<P>
Menubuttons were also typically organized int