How do I setup Xdmx with gdm?

[Tom Schutter <tom@platte.com>]

Can anyone give me a clue as to how to have gdm use Xdmx?

The only hint that I can find is from
http://www.gnome.org/projects/gdm/docs/2.13/configuration.html:
  ProxyXServer=

  The X server command line for a XDMCP proxy. Any nested X server like
Xnest, Xephr or
  Xdmx should work fairly well. 

But adding this to /etc/gdm/gdm.conf doesn't seem to do anything:
  [xdmcp]
  Enable=true
  EnableProxy=true
  ProxyXServer=/usr/bin/X11/Xdmx :1 -display :0 -display tobi-d:0
+xinerama

I can run Xdmx from a terminal, but I get no session.  The best idea
would seem to be to have gdm run Xdmx, and then provide the session.

-- 
Tom Schutter (mailto:tom@platte.com)
Platte River Associates, Inc. (http://www.platte.com)