Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!ncar!ico!rcd
From: rcd@ico.isc.com (Dick Dunn)
Newsgroups: comp.lang.postscript
Subject: PostScript Level II, contextual forms
Summary: wrong level for these decisions
Message-ID: <1990Aug22.051728.16659@ico.isc.com>
Date: 22 Aug 90 05:17:28 GMT
References: <9607@goofy.Apple.COM> <1289.26d27708@waikato.ac.nz>
Organization: Interactive Systems Corporation, Boulder, CO
Lines: 28

ccc_ldo@waikato.ac.nz (Lawrence D'Oliveiro, Waikato University) writes:
> What sort of support will Level II PostScript have for contextual forms?
> As I've tried to point out before, this is important not only for non-Roman
> writing systems, but for some Roman fonts as well.

> * A string of text shouldn't need to contain different codes to represent
>   different contextual forms of the same character. Instead, this should
>   be resolved at the time the text is drawn. This keeps things simple for
>   the application.

While the nature of the problem is correctly stated, PostScript is the
wrong level to make such a decision.  At the level of PostScript, the
output of text should be regarded as the output of a sequence of glyphs
which have no inherent semantics.  Characters are simply objects being
placed on the page or screen...it doesn't make sense to ascribe language-
dependent context to them.  If there is any "semantic" content to a
character at the PostScript level, it has to do with things like width or
bounding box.

Decisions have to be made upstream of PostScript anyway.  For one example,
consider that text justification depends on character widths.  The
substitution of one glyph for another will alter the justification and 
potentially thereby alter the layout of an entire page.  You don't do the
layout in PostScript (unless you're (a) a masochist, (b) doing simplistic
layout, and (c) patient:-)
-- 
Dick Dunn     rcd@ico.isc.com -or- ico!rcd       Boulder, CO   (303)449-2870
   ...Are you making this up as you go along?