RE: a DSSSL typesetter

["Reynolds, Gregg" <greynolds@xxxxxxxxxxxxxx>]

> -----Original Message-----
> From:	Brandon Ibach [SMTP:bibach@xxxxxxxxxxxxxx]
> Sent:	Friday, May 08, 1998 1:46 PM
> To:	dssslist@xxxxxxxxxxxxxxxx
> Subject:	Re: a DSSSL typesetter
> 
> has anyone ever thought of implementing TeX's functionality in
> PostScript?  In other words, you could setup a simple Jade backend
> which would write the stream of flow objects to a PostScript file, and
> a standard set of PostScript routines would typeset those objects
> directly, rather than having TeX output (via DVI->ps) a stream of
> "stupid" PostScript code which just says "move here, draw this".
>    Perhaps I'm oversimplifying here, and I mean no disrespect to what
> TeX accomplishes, but it just seems that PostScript has all the
> facilities to pull off what TeX does, and it would eliminate the extra
> step of running TeX.  The two possible scenarios I see are to have the
> actual rendering process (ie, the printer itself) run these routines,
> or code the routines to simply write out a stream of "stupid"
> PostScript code, much as TeX does.
>    Has anything like this been thought of, attempted, or done?  Or am
> I just completely off the wall here?
> 
> -Brandon :)
	[Reynolds, Gregg]  
	Brandon:

	No, you're not so terribly off the wall, but I think it's more
complicated than you suspect.  
	 
	TeX and Postscript are quite different beasts.  Postscript is
usually categorized as a page-description language, TeX as a typesetting
language.  Each is extremely good at what it does, and not so well
suited for other tasks.  Postscript can put ink on paper in whatever
pattern you desire, but knows next to nothing about typesetting.  There
is no way to tell it, for example, typeset this footnote at the bottom
of this page, and if takes up more than 1 inch, chop it off at 1/2 inch,
and flow the rest to the bottom of the following page(s).  I suppose in
principle one could write a postscript program to handle such
compositional tasks, but the language just isn't suited for it, so it
would be really hard.  TeX on the other hand isn't as powerful as PS for
simply laying marks on the page (though is it quite powerful in this
respect in its own right), but it understands typesetting.  Where to
break lines and pages, for example, or how to handle such traditional
typesetting conventions as leaders and rules.  Such stuff can get very
very complicated.  

	A complete implementation of  DSSSL probably would generate  PS
or PDF, but that output would in turn would be generated by a TeX-like
typesetting engine, and you probably wouldn't want to do that in a
page-description language.  In a sense one could view DSSSL as a
successor to the typesetting *language* invented by Knuth to implement
his ideas.  But to adapt TeX (the program, not the language) to DSSSL is
a pretty big project.  A great project, which I would love to undertake
if I had the time, but a big project.

	Best of luck,

	Gregg


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