Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!elroy.jpl.nasa.gov!decwrl!adobe!heaven!heaven.woodside.ca.us
From: glenn@heaven.woodside.ca.us (Glenn Reid)
Newsgroups: comp.lang.postscript
Subject: Re: Pageview problem
Keywords: pageview %! structuring conventions
Message-ID: <464@heaven.woodside.ca.us>
Date: 30 Mar 91 22:37:41 GMT
References: <1561@vidiot.UUCP>
Sender: glenn@heaven.woodside.ca.us
Lines: 47

Vidiot writes
> But, I have to agree with the logic at Sun regarding how pageview works.
> As pointed out in my previous posting, pageview considers the next instance
> of %! to mean that another PostScript document has been included and to
> ignore all comments until the next %%Trailer, which better be part of the
> included document.  Then it will look at the comments again.  This idea
> here, as I gather it, is that the included document is part of the page
> that it is trying to display.  The included document should only really
> be one page and part of the page it was included with.
> 
> Well, groff kind-of messes up that logic.  By adding the %! line again,
> pageview thought that another PostScript file was included and rightfully
> displayed everything until the %%Trailer came along.  In this case, there
> wasn't an included document.  I agree with the person responsible for the
> pageview code.  If the offending %! is edited from the groff document, the
> document is displayed correctly, one page at a time.  With the -DBROKEN_
> SPOOLER flag turned on, it too displays correctly.
> 
> I feel that groff should not put in the extra %! line at all.  It is the
> only thing that fools pageview, no matter what the state of -DBROKEN_SPOOLER.
> Either PostScript output will display correctly, except as noted.

There is a specific convention for dealing with embedded PS files, and
looking for %! is not it.  After all, %! means very little, in that it is
not even claming to be a conforming document.  In addition, the %%Trailer
comment is optional, and may contain code following the trailer in any
case.  It is certainly a bad idea to do what pageview is described as
doing.

The comments %%BeginDocument and %%EndDocument were created for this
purpose; a spooler could safely skip matching pairs of these comments,
and the comments between them, when scanning a document.  Looking for
%! and %%Trailer is simply not reliable, and in fact would almost never
work, it seems to me.

The BROKEN_SPOOLER constant is useful, although perhaps it should be
BROKEN_PREVIEWER.

Remember, %! just means that the file is PostScript, not that it represents
a document or anything else.  It can appear an arbitrary number of times
within a document.  It is only significant as the very first two characters
in a file.

--
 Glenn Reid				RightBrain Software
 glenn@heaven.woodside.ca.us		NeXT/PostScript developers
 ..{adobe,next}!heaven!glenn		415-851-1785 (fax 851-1470)