Dinamically switch between Xinerama and Multiseat

[Tobias Kaminsky]

Hello,

I have 2 TFTs with each 1280x1024.
Normally I work alone on the pc -> Xinerama.
But sometimes my girlfriend wants to work on the pc, too. But I do not want to 
log out, change KDM and log in again.

So I need something that works on the fly.

Here is what I have this far:

1) Starting X across both TFTs.
2) DISPLAY=:0 Xephyr :1 -br +xinerama -screen 2560x1024
This lets me have one big screen where I can load KDM.
3) DISPLAY=:1 xrandr -s 1280x1024 lets me change the size to one TFT.

3.1) Starting another Xephyr on the other TFT with a small Window Manager is 
no big deal.
----> Two Xephyr, one one each TFT

Now "backwards":
Closing one Xephyr.

4) DISPLAY=:1 xrandr -s 2560x1024
Not a supported mode any longer.

This is my problem. Starting Xephyr with 2560x1024 works fine.
But after resizing it, the maximum resolution is 1600x1200.

Also adding a new modeline does not help as it is accepted for the first time 
but not being displayed nor possible to select it.

Any suggestions would be nice.

------
xrandr-1.2.3
xorg-server-1.5.2

Portage 2.2_rc15 (default/linux/amd64/2008.0, gcc-4.3.2, glibc-2.8_p20080602-
r0, 2.6.27.6 x86_64)
System uname: Linux-2.6.27.6-x86_64-AMD_Phenom-tm-_9850_Quad-Core_Processor-
with-glibc2.2.5  
------

Thanks
Tobi