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From: jg@zorch.crl.dec.com (Jim Gettys)
Newsgroups: comp.windows.x
Subject: Re: OW as a PostScript X server...
Message-ID: <1990Nov13.040710.28580@crl.dec.com>
Date: 13 Nov 90 04:07:10 GMT
References: <9011121513.AA06367@islanders.> <1990Nov12.221429.23721@crl.dec.com> <1990Nov13.004034.5670@mcs.anl.gov>
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Organization: DEC Cambridge Research Lab
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In article <1990Nov13.004034.5670@mcs.anl.gov> korp@atlantis.ees.anl.gov (Peter Korp) writes:
>In article <1990Nov12.221429.23721@crl.dec.com> jg@crl.dec.com (Jim Gettys) writes:
>>In article <9011121513.AA06367@islanders.>, fgreco@dprg-330.GOVt.shearson.COM (Frank Greco) writes:
>>> > 
>>> > 	And, no X extensions are involved; you're guaranteed to get PS
>>> > 	rendering with OW.
>>> > 
>
>[various ramblings deleted]
>
>>The technical problem with the X11/NeWS merged server is the following:
>>
>>If you want to mix X and PostScript based imaging models (and I know people
>>who do, for very good reasons; each imaging model has much to offer the
>>application programmer), you have to synchronize the two connections.  This is 
>>more than a minor pain to an application programmer in this cicumstances
>>(and can be a non-trival performance problem; it basically involves putting
>>XSync calls and equivalent everywhere you care about order, which requires
>>a server round trip); and comes naturally if you are talking to a server 
>>over a single connection.
>>
>
>This is only true to a certain extent. If you are only going to do imaging
>then no round trip is required. If you wish to use the NeWS input facilities
>as WELL AS the X input facilities then the problem you describe becomes an
>issue.

Given that you are talking to a server over two separate connections,
each with independent buffering in X, NeWS libraries, socket buffers and
server buffers on both the client and the server, there is no
way to guarantee sequentiality of output I can see without forcing a round trip
on each connection.  If I'm wrong, I'd be happy to understand how
you avoid this.  A flush just sends the data; it doesn't guarantee the
server has processed it; I believe a sync in some form is required to get
sequential output for any application which mixes X and PostScript imaging
models with separate connections.

This is why I believe that DPS's approach is the correct one (independent
of the details; I haven't programmed it, so reserve judgement as to
whether the interfaces are well done) and X11/NeWS
merged server is incorrect, as I understand the two approaches.
Of course, you could do the X extension in reverse (X inside the NeWS
protocol); that would be equivalent, but two separate connections seem
to be generating really great problems for anyone who wants to mix imaging
models, and a fundamental problem with the approach.

>>And as to the rest of your message, isn't Shearson the brokerage house that
>>has taken a big interest in Sun Microsystems? Or is it one of the other
>>ones?
>>				- Jim
>

My apologies; done in a moment of weakness, regretted immediately.
				- Jim
--
Digital Equipment Corporation
Cambridge Research Laboratory