What Debian SDL package for SDL with/in Xen?

[Rakotomandimby Mihamina <mihamina.rakotomandimby@etu.univ-orleans.fr>]

Hi,
I want to install an unmodified OS (aka in full virtualization mode, on my VT 
CPU) as a domU.
When I set "sdl=1" in the guest configuration file, and then 
"xm start the-guest.cfg", to SDL window pops up.
When I use VNC, I can also connect. But I wonder why it doesnot work the SDL 
way...
I guess I am missing some SDL related package. But which ones?
I use Debian Sid, I installed Xen (3.0.3) fully with apt.

Just for information:

debian:/etc/xen/vm# dpkg -l | grep sdl
ii  libsdl1.2debian                    1.2.11-7          
ii  libsdl1.2debian-alsa               1.2.11-7