here must not exist a window named <I>pathName</I>, but
<I>pathName</I>'s parent must exist.
<P>
A menubutton is a widget that displays a textual string, bitmap, or image
and is associated with a menu widget.
If text is displayed, it must all be in a single font, but it
can occupy multiple lines on the screen (if it contains newlines
or if wrapping occurs because of the <B>-wraplength</B> option) and
one of the characters may optionally be underlined using the
<B>-underline</B> option.  In normal usage, pre