This question might seen similar to Emulating extra displays but it's different in the important detail.
Suppose I'd like to test a feature for certain window manager with multi monitor support using RANDR extension. Seems like it is impossible to achieve this using Xrandr/Xdmx. I've tried different combinations with +extension RANDR and +xinerama parameters both to Xrandr and Xdmx but without luck so far. Also, I didn't find any clue in man pages for both commands.
My simple case is:
Xephyr -screen 800x800+0+0 -ac :1 &
sleep 1
Xephyr -screen 800x800+800+0 -ac :2 &
sleep 1
Xdmx +extension RANDR -xinput local -display :1 -display :2 -ac :3 &
sleep 1
DISPLAY=:3 window-manager
I've also tried to simply use only Xephyr:
Xephyr +extension RANDR -screen 800x800+0+0 -screen 800x800+800+0 -ac :3 &
sleep 1
DISPLAY=:3 window-manager
but obviously it creates two separate X screens, so the root window is not shared between the screens.
Is there any other way for getting xrandr to report two available outputs with my case?
