How to trigger.
***WARNING: Save everything before trying this.***
With a Gnome Classic session. There is a 4 screen multi screen selector
on the panel at the bottom of the screen organized as 2 rows of 2
screens. It has a preferences dialog acessable via a right click when
on an empty space on
Public bug reported:
When multi-screens preferences dialog is brought up and the number of
screens is changed, it messes up and the pannels go away, all windows
vanish, but programs are still running, and you are left with only your
background wallpaper showing with no option other than to reboot
