menubuttonA menubutton widget displays like a button, but when activated a menu pops
up. The menu of the menubutton is defined through the menu command
and is attached to the menubutton.
An example of a menu button:
menubutton .mb -menu .mb.m -text "mymenu"
menu .mb.m
.mb.m add command -label hello
.mb.m add command -label goodbye
which crates a menubutton widget named .mb with attached menu
.mb.m and displays the text `mymenu'. Menu .mb.m is
defined as two command options, one labelled hello and the other
labelled goodbye. When the menubutton .mb is clicked on
then the menu .mb.m will popup and its options can be chosen.