A small addition to dvidoc, txt, or crudetype

[rocky@watson.ibm.com (Rocky Bernstein)]

I recently looked at the various packages to make the TeX system
typeset for a crude ASCII typewriter (\'a l\`a nroff).

Various packages on the net---dvidoc, txt and crudetype---all seem to
have a similar style option or similar macro definitions.  The macros change
font definitions to use a (hypothetical?) monospace font called
``doc.'' Many of these package also come with doc.tfm.

In none of these packages that I have come across is there a doc.mf,
or doc.vf, or doc.300pk. In fact, I haven't found any of these on the
net separately either.

Well, you may be thinking ``Of course not, you are supposed to use
the dvi file with crudetype (or dvi2tty, or...). It does the job of
ignoring that non-existent font!''

But there are reasons why one might want to have a printable font
around even though a corresponding dvi formatter only looks at the
doc.tfm file. (Actually, perhaps there is just one reason with
ramifications):

1) One might not have such a converter (dvi2tty, crudetype, etc.). I
   might just like to see what such programs might produce.
2) Related to this, I have a DVI file around created by a ``doc'' style
   (such as distributed in the ``txt'' package) and I'd just like to preview
   this.
3) Related to this, rather than go through the process of converting
   to ASCII text and printing this, I'd rather print in the fashion
   that I normally use for La/TeX or DVI files. For example, one might
   use the Emacs-oriented package auctex.

Well, it didn't take long for me to turn doc.tfm into doc.vf to solve
my problems. Basically, I mapped all of the characters in this font to
the corresponding characters in cmtt10. Ideally one would want a font which
is designed to be monospace; cmtt10 is not.

For example, I had considered using an Adobe font, but decided against
it for generality: there are many DVI drivers that don't understand or
care about Adobe fonts. One might also argue that there are a number
of dvi drivers that don't understand virtual fonts either.
However, since virtual fonts should become more prevalent in the
future and since dvicopy can be used to ``unvirtualize'' a virtual dvi
file, it didn't strike me as a big issue.

The other attractive alternative is to modify cmtt10, such as to
remove ligatures and turn it into monospace. Is there a monospace
MetaFont font already around?

Comments? Be happy to share the vf. Really though, it was a trivial
exercise in using tftopl, vptovf and a text editor.

Regards,
  R. Bernstein