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From: daniel@mirsa.inria.fr (Daniel Dardailler)
Newsgroups: comp.windows.x
Subject: Re: XSelectNextEvent()
Message-ID: <137@mirsa.inria.fr>
Date: 10 Mar 89 09:20:25 GMT
Reply-To: daniel@mirsa.inria.fr (Daniel Dardailler)
Organization: Bull Research Center. Sophia Antipolis. France
Lines: 51

DL> is David D. Levine.
DD>> is me.

Thanks for your comments, David.

DD>> 	I want to wait for X events from more than one X server.
DD>>	(it's for a communication program named xtalk, which act
DD>>     basically like the unix-talk but with the X protocol and
DD>> 	 windows/mouse convenience: independent window, drawing facility, 
DD>> 	 talk with several persons...)

DL> I'd say that this application is a good candidate for
DL> multi-processing.  

Several processes was my first implementation. I only ask xpert for an 
other possible solution with a centralysing one. 

DL>                    You have two asynchronous event sources.  If you
DL> try to deal with them both in one (synchronous) process, you will
DL> either spend a lot of time in pointless looping (which is expensive of
DL> CPU time) or block on one event source while ignoring input on the
DL> other (which increases response time).  

It seems to me that the X server (itself :-) is "one (synchronous) process"
waiting for MANY "asynchronous event sources". What do you do with the
IPC select call?
The real problem is in fact that after the select call, I have problems
for reading a given number of events. Open issue.

DL>			                    I'd suggest you fork() two
DL> processes, one to watch each display, which communicate with each
DL> other via pipes or shared memory.

I prefer to return to my first idea and have several independent processes 
communicating with SendEvent requests. So they don't have to wait from 
another socket than the X server one.

DL> This solution has nothing to do with X, really, but it's the best one
DL> I can think of offhand...

If I can (and I can) build my program with no other network protocols 
than the X Window System Protocol-V11, it will be portable on ALL
X11 platform. Any other RPC mecanisms dealing with the same number of OS 
is welcome.


   Daniel Dardailler                   |      Email : daniel@mirsa.inria.fr  
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