Xlib: connection refused by server

Trying run under root:
su
swscanner
I received following error message:
Xlib: connection to ":0.0" refused by server

Easy solution, run under regular user:
xhost +localhost
OR:
xhost local:root

Then run under root:
export XAUTHORITY=/home/regular_user_name/.Xauthority

Where regular_user_name is name of the user doing command su.