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Newsgroups: comp.lang.postscript,
Subject: PostScript vs. X as a graphics protocol
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Organization: Brown University Department of Computer Science
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*******PROBLEM:

I've heard that some people prefer PostScript as a graphics protcol
over some other protocols like the X protocol for the following
reason:

1. PostScript is a program, which means that you can pack the data in 
   the best way possible, and include a tiny program to interpret it.

2. The X protocol is defined and static, so you can only do the things
   that the X protocol allows. Your data must be in one of the
   predefined forms.

*******EXAMPLE:

If I wanted to generate a picture made up of filled regions,
I could use the X protocol like this:

    line line line line fill line line line line fill line line line fill
    etc. etc.

Where the lines and fills belong to some predefined format. In
PostScript I can prepend a special program to let me do the lines and
filling more compactly, like this:

/p 4/f{{}forall moveto gsave{dup 32 mod dup 15 mul rotate sub p div 0 rlineto}
forall fill grestore}def 4 scale 1 def(``f`f`f)dup(  )f( i).3 setgray f/p 8 def
1 setgray/h(F!6! 2477!W)def h("4)h(,C)h(6O)h(LT)h(^O)h(tC)h(~6)(7!6!"7#$&6!7 #)
(9~)(""""""""""")(}~)(fTV``Vt)(9!)(e!FR"n&44ED-w@-7&&b)(C2)11{f}repeat showpage

********THINK-UMS:

Well, pros and cons that I can think of.

PostScript Con: the program passed in through the protocol
                could be a security problem.

PostScript Con: the program could be non-portable. When you port 
                X to a platform, it's done. With a PostScript protocol
                each protocol program needs porting.

PostScript Pro: Takes less space than X.

X Pro: No need to interpret and compile incoming program. Large common
       stuff can be handled directly.

PostScript Con: Unless you combined a little of the "static programs"
                of the X method, you'd never be able to interpret data
                at all unless there were a program sent with it!

PostScript Con: Is PostScript fast enough?

********DISCUSSION?

Now, I come from MIT where a lot of X stuff happened, but I also
like PostScript a lot. So I am undecided.

Any opinions on this choice and where/when one or the other is best?

What systems use PostScript as a protocol? The NeXT does this, right?

I'm not going to cross-post this to an X newsgroup because I'm just
kind of curious to hear some opinions. I'm not trying to start a
flame session between two newsgroups or anything!! :)

-Jon
%! Jon Monsarrat   jgm@cs.brown.edu   Brown University %! Obfuscated PostScript
0 0 moveto 15 setlinewidth(qlllll-??LHHL??llH?hH7t,7olCAHH@)1 setlinejoin{dup
10 mul rotate 80 lt{50 0 rlineto}{50 0 rmoveto}ifelse}forall stroke showpage