Run X11 application inside docker without VNC or SSH

I'm so annoyed that people would think of using ssh forwarding or VNC to run a X11 application inside docker. Docker is just a special chroot environment so there must be a more efficient way to setup the communication tunnel required by X11, and here it is:

docker run -v /tmp/.X11-unix:/tmp/.X11-unix -e DISPLAY=unix$DISPLAY

/tmp/.X11-unix contains the unix domain socket file used by your running X11 application, but mounting it inside docker, the X11 app inside docker will  happily access it.