Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!sun-barr!newstop!sun!satori!dmc
From: dmc%satori@Sun.COM (Doug Cook)
Newsgroups: comp.windows.x
Subject: Re: Multiple-server X clients - do they exist?
Keywords: X
Message-ID: <124309@sun.Eng.Sun.COM>
Date: 7 Sep 89 23:23:58 GMT
References: <3522@blake.acs.washington.edu>
Sender: news@sun.Eng.Sun.COM
Reply-To: dmc@sun.UUCP (Doug Cook)
Distribution: usa
Organization: Sun Microsystems, Mountain View
Lines: 27

In article <3522@blake.acs.washington.edu> mbader@cac.washington.edu (Mark Bader) writes:
>Does anyone know if a multiple-server X client is possible?  For
>instance, is there a way to start up an X client and sent its output
>to multiple displays at the same time?
>
>Is this possible by hacking the source?  Or is there an easier way to
>do it (a new feature for X11R4?)

You need to write the client so that it's intelligent enough to handle multiple
display connections. You'll have to explicitly create the resources you need on
each server. The main changes you need to make are in the event-handling loop. On 
a BSD box, you can then use select() on your server connection fd's to determine when 
events are available from any server. Look at the return value from select() to 
determine which server's events you want to process. If data is waiting on more 
than one server connection, use a round-robin algorithm to select a connection. Then 
call the normal Xlib routines (XNextEvent(), etc.) for that server and process the 
event as you would for a single-server client.

There are some subtleties, though. Because you're using select() rather than 
XNextEvent() to determine when server events are waiting, you need to explicitly
flush events for all the display connections at key points (XNextEvent flushes
events before it tries to read them). 

This is a pretty generalized response, but I hope it's enough to answer your
question. If not, please write me directly, and I'll send you some sample code.

	-Doug