This program uses the Tk windowing/graphics library. There
are two implementations of Tk for Mac OS X. One, Tk-X11, is
built on top of the X11 window system.  This version of Tk
is very similar to Tk on other platforms, including
GNU/Linux, on which this program has been developed. If you
want the program to work as closely as possible to its
design, you should install X11 and Tk-X11.

Tk-Aqua is built on top of Aqua, the native
windowing/graphics system for Mac OS X.  If you use Tk-Aqua,
you will get a look-and-feel that is closer to that of other
native Macintosh programs than if you use Tk-X11. The
downside is that, by enforcing a numver of user interface
design decisions made by Apple, Tk-Aqua cannot do some
things that Tk-X11 can. Among the differences are the
following:

(a) Tk-Aqua will only put menus on the menubar. It refuses to put
    command buttons on the menubar.

(b) Tk-Aqua does not support multi-column menus.

(c) Tk-Aqua does not support multi-line button labels.

The most import of these is the first. This program makes
use of commands on the menubar. If it is run unmodified
under Tk-Aqua, these commands are simply omitted.  In order
to allow the program to be used under Tk-Aqua, if it detects
that it is running under Tk-Aqua, it creates a menubar of
its own at the top of the window containing buttons for
these commands. The other menubar entries are put on the
usual Mac menu at the top of the screen. This makes the
commands accessible at the expense of splitting the menu
into two parts.
