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In article <187@sol.warwick.ac.uk> cudcv@warwick.ac.uk (Rob McMahon) writes:
>... the TeX cm* fonts [on the] 2700 ... are really weedy. ...
>I assume this is a write-white vs. write-black problem, so
>that's my first question - Am I right ?

Yes.

>Now, I have all the metafont input to these fonts, so I'm thinking it must
>be possible to produce some more appropriate fonts.

It is indeed possible.  Don Knuth, genius that he is, foresaw this
problem when he wrote Metafont84 and the Computer Modern fonts.
Either that or it hit him in the face after he wrote the original
Metafont.  :-)

Anyway, what you need to do is to define a `mode' for the 2700.  I
have not yet had time to play with Metafont, so I am not sure just
what these are, but here is the `Imagen 8/300' mode:

	mode_def imagen =  % imagen mode: for the Imagen 8/300 (Canon engine)
	 proofing:=0;      % no, we're not making proofs
	 fontmaking:=1;      % yes, we are making a font
	 tracingtitles:=0;    % no, don't show titles in the log
	 pixels_per_inch:=300;
	 blacker:=0;      % Canon engine is black enough
	 fillin:=.2;      % and it tends to fill in diagonals
	 o_correction:=.6;    %
	enddef;

`blacker', `fillin', and `o_correction' are the knobs to tweak.
I believe `blacker' controls a generic pixel-emphasiser, while
`fillin' adjusts diagonal lines, and `o_correction' is for
`overshoot': lines that print slightly longer than intended.

This problem brings up another point (which, incidentally, is the
reason I am posting this, rather than mailing it):  One set of
fonts is not sufficient.  If fonts are to be downloaded---which
seems unavoidable, at least for now---then any site that maintains
more than one kind of print engine will need more than one
rasterisation of each font.  At present it is possible to do this,
but it is an administrative nightmare.  Each device driver has its
own idea of where to find fonts; in many cases this is a compiled-in
pathname such as `/usr/lib/tex/fonts'.  Other drivers allow a path
variable, e.g., PXLPATH in my older C-TeX drivers.  This allows a
user to override the compiled-in path, to use, say,
`/usr/lib/tex/fonts.2700'.  I now think that this is too clumsy,
especially given the recent proliferation of font file formats:
GF, PK, PXL, Imagen's RST, and whatever else is out there.

The solution I have adopted now is better, but (I think) still not
ideal.  I have a single configuration file `/usr/lib/tex/fontdesc'
that looks something like this:

	#
	# C-TeX font configurations
	#
	# N.B.: choose only one of `box' or `blank' TFM fonts.
	#
	# %f expands to the font, %m to the appropriate magnification.
	# SLOP is a hack, to pick up `nearby' fonts in case of roundoff
	# error in magnification computations.

	# current directory always searched first
	#	TYPE	SPEC	SLOP	PATH
	font	pk	*	2	%f.%mpk
	font	gf	*	2	%f.%mgf
	font	pxl	*	2	%f.%mpxl
	font	box	*	0	%f.tfm

	# `invisible' SLiTeX fonts
	font	invis	*	0	/usr/lib/tex/fonts/invis/%f.tfm

	# Canon (Imagen 8/300, et alii) fonts
	font	pk	canon	2	/usr/lib/tex/fonts/canon/%f/%f.%mpk
	font	gf	canon	2	/usr/lib/tex/fonts/canon/%f/%f.%mgf

	# Raven (Xerox 2700, et alii) fonts
	font	pk	raven	2	/usr/lib/tex/fonts/raven/%f/%f.%mpk
	font	gf	raven	2	/usr/lib/tex/fonts/raven/%f/%f.%mgf

	# If all else fails, draw boxes.
	font	box	*	0	/usr/lib/tex/fonts/%f.tfm

The font description file name can be set in the environment variable
TEXFONTDESC.  The major problem with this scheme is that it is
difficult to set up a font description file.  Once that has been
done, however, it is easy to describe any arrangement of fonts.
I hope that this scheme will prove useful, and that others will
implement something compatible in their drivers.  (The C-TeX font
code is freely available to software developers, or will be when
I can get at it again: it is on a machine that is down with hardware
troubles.)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
UUCP:	seismo!mimsy!chris	ARPA/CSNet:	chris@mimsy.umd.edu

In article <187@sol.warwick.ac.uk> I write:
><munch>
>
>I finally got my dvi->2700 driver working, but the fonts I get from converting
>the TeX cm* fonts to 2700 format are really weedy.
>
...
>
>Now, I have all the metafont input to these fonts, so I'm thinking it must
>be possible to produce some more appropriate fonts.

Well thanks to Nelson H.F. Beebe <Beebe@arpa.utah-science> and
particularly to Karl Berry <kbb%edu.brown.cs@relay.cs.net>, and having
R'dTFS&M I find that when you make Metafont, you really ought to add a
local changes file on the end of the plain base (i.e. ** plain ; input
local ; dump ; end), an example of which lives in waits.mf.  This
defines modes which describe your output devices.  I used the qms mode,
and this seems a fair first approximation.

When you install TeX, it seems you shouldn't just accept the pk/pxl
files supplied, but you really should install metafont at the same
time, and make up a set of fonts appropriate to your output device.

It seems a shame that neither the TeX, nor the Metafont installation
instructions point you in this direction, but you either have to read
the Metafont book, or the sources to plain.base.

If anyone has any accurate values for 'blacker', 'fillin', and
'o_correction' for a Xerox 2700 I'd appreciate seeing them.

        Rob
-- 
UUCP:   ...!mcvax!ukc!warwick!cudcv
JANET:  cudcv@uk.ac.warwick.daisy       ARPA:   cudcv@daisy.warwick.ac.uk
PHONE:  +44 203 523037
Rob McMahon, Computer Unit, Warwick University, Coventry CV4 7AL, England