Re: Combine Displays of several X-Servers

From: Wayne Throop (throopw_at_sheol.org)
Date: 03/17/04 

Date: Wed, 17 Mar 2004 08:02:17 GMT

: Marek Jawurek <icetatatu@gmx.de>
: what I am looking for, is a solution to combine several computers and
: their VGA cards for having a huge X Xinerama Display. I tried out DMX
: (Distributed Machine X ?GUESS SO) but it is still under heavy development
: and not even close to stable. I would also consider using a different
: windowing system.
: The goal of my project is to have a lot of displays that I can access
: using my notebook.
: Any ideas ?

I have used two methods. Both have their problems,
but both are useful in some circumstances, and both are
quite mature, stable methods.

First, x2x or synergy (that's two distinct but similar tools that do
roughly the same job, so that "or" is "one or the other"). This doesn't
fully fuse displays together, but you can use a single keyboard/mouse
across all the displays; moving the mouse off the edge of one screen
brings it up on the next display, and so on. Further, the X selections
are fused together, so you can select on one screen, and paste in
another. What you can't do is drag an app from one display to another,
nor have an app span displays. For moving apps from one display to
another, you might use xmove, but it wouldn't be as natural as just
dragging it, and it apps still couldn't span displays. Even with these
limitations, I find it very useful; I use this idea both on my desktop
displays at home, and with my laptop when visiting places where extra
dumb(ish) X terminals are available for extra pixels.

Second, a single VNC desktop with multiple VNC viewers. Possibly
coupled with use of x2x or synergy, and possibly just using VNC's full
screen mode to allow the mouse and keyboard to operate on all the
screens; I'm most familar with just VNC by itself for this method.
Create an Xvnc desktop with enough pixels to cover all the displays,
with a geometry upon which you can tile the actual displays. Then on
each display, start a vncviewer, and have each viewer display a
different region of the underlying Xvnc desktop. This will allow you to
drag apps between the displays, and have apps span displays. If you
don't use x2x or synergy, it'd probably be most convenient to mostly
just draw on the other displays, and do interactive mousing on one of
the displays in full screen mode; to mouse on another display, you just
move the mouse there, which is nice, but that drags the "main" display
away from where it "should be" in the virtual desktop.

So, both schemes have disadvantages compared to an N-headed Xinerama
setup. But they do allow good use of multiple displays on multiple
distributed computers, and they are both quite stable. I mostly use the
x2x/synergy technique, and it usually does what I need. On the few cases
where I wanted to run an app spanning displays (eg, a spread*** with
very long rows), the VNC method works for getting all the pixels displayed
across multiple screens, even if mousing around can be a bit of a pain.

Wayne Throop throopw@sheol.org http://sheol.org/throopw