Path: utzoo!attcan!uunet!decwrl!bacchus.pa.dec.com!wsl.dec.com!klee
From: klee@wsl.dec.com (Ken Lee)
Newsgroups: comp.windows.x
Subject: Re: Display sharing
Message-ID: <1990Oct1.163506@wsl.dec.com>
Date: 1 Oct 90 23:35:06 GMT
References: <9010011634.AA26923@ATHENA.MIT.EDU>
Sender: news@wrl.dec.com (News)
Reply-To: klee@wsl.dec.com
Organization: DEC Western Software Laboratory
Lines: 38

In article <9010011634.AA26923@ATHENA.MIT.EDU>, rabbit@houvmscc.iinus1.ibm.COM writes:
|> We have a requirement for the
|> capability to share displays between consoles that are going to be a
|> variety of workstations of an unknown flavor running Xwindows.

There are 2 things that can be shared in a user interface:

1.  output - the same graphics are drawn on each monitor
2.  input - the user at each monitor may interact with the user interface

The first part is easy.  There are many techniques, both in hardware
and in software, for duplicating displays.  Hardware solutions, such as
splitting and amplifying the RGB out signals and sending them to
multiple monitors are probably the cheapest.

If you want many users to be able to send keyboard and mouse input to
an X client program, you have to do quite a bit more work.  There are
several ways to do this:

1.  modify the server to split the protocol
2.  modify Xlib to split the protocol
3.  modify the client to send different protocol streams to different servers

All 3 possibilities have been prototyped.  1 and 2 are the cheapest, as
you don't have to modify the client programs.  With 1, you don't even
have to recompile them.  As far as I know, none of these prototypes has
been made publically available.  The third technique, modifying the
client, has the potential to give you the best user interface.  There
are many user interface problems with multi-user application semantics
and only modifying the applications gives you a chance to properly
address these.  Several multi-user clients, mostly games, using this
technique are publically available.

-- 
Ken Lee
DEC Western Software Laboratory, Palo Alto, Calif.
Internet: klee@wsl.dec.com
uucp: uunet!decwrl!klee