Non root Xorg

This guide details running X server under user account.

It was only tested under nouveau, but all kms driver should work.

Additional prerequisities
Some of this support is pretty fresh so one definitely needs to install unstable packages

Also depending on driver support there may be need to install development packages from x11 overlay. For example xf86-video-nouveau doesn't have any version with necessary changes so -9999 package is needed.

Rebuilding Xorg
Disable suid USE flag:

Rebuild Xorg

Making necessary changes to system
Now you can run X as user, however because none of login managers are capable yet of doing necessary permision handling it needs some workarounds. In particular, X run by user needs to be able to access /dev/input files and it needs to be started manually.

To access /dev/input files it's easiest to add them to group and allow user to access them.

Create udev rule to change /dev/input group on boot:

Reload udev rules to get the new permissions (note that this may interfere with your input devices on the current vty)

If logged on tty1 use vt1, on tty2 use vt2, and so on

X should now run as user.