Path: utzoo!attcan!uunet!bellcore!att!linac!pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!think.com!snorkelwacker.mit.edu!bloom-beacon!LIGHTNING.MCRCIM.MCGILL.EDU!mouse
From: mouse@LIGHTNING.MCRCIM.MCGILL.EDU
Newsgroups: comp.windows.x
Subject: Re: OW as a PostScript X server...
Message-ID: <9011211347.AA18584@lightning.McRCIM.McGill.EDU>
Date: 21 Nov 90 13:47:21 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 34

[about DPS-versus-NeWS and synchronization]
>> If DPS violates my rules above (which is really the principle of
>> "don't surprise the poor programmer") such that simple immediate
>> rendering commands can't be interspersed with X rendering commands
>> and execute in the order the naive programmer expects, then I'm not
>> happy with DPS as it currently stands [...].
> You have to remember that the PostScript language is interpreted and
> allows you to redefine its operators.  There's no way to know that
> the "lineto" operator hasn't been redefined to call a loop that runs
> for 10 minutes.  It's inherent in the nature of the beast.

So?  If I've done this and I call lineto, I expect the connection I do
it on to be blocked for ten minutes.  If I want to run it
asynchronously I'll explicitly "fork" a "process" to do it.  (Quotes
because the terms don't have quite their usual UNIX-style meanings.)

> I would argue that saying "you must always synchronize after
> PostScript rendering before relying upon the results for X calls" an
> easier rule for programmers to remember than something like "you
> don't need to synchronize as long as you use only built-in operators
> that haven't been redefined and you only use <= N of them in one call
> and by the way no loops and no large image manipulations that can
> take several seconds and no text since the font definition can
> contain arbitrary PostScript and..."

Well yes.  But compare it with "you don't need to synchronize unless
you told it to run asycnhronously".  I would say that least surprise
requires that the default be synchronous, and that the little argument
we've just had here bears me out.

					der Mouse

			old: mcgill-vision!mouse
			new: mouse@larry.mcrcim.mcgill.edu