#!/bin/bash

# generate xauth file for Docker container

CONTAINER_HOSTNAME=$1
XAUTH_FILE=$2

mkdir -p $(dirname $XAUTH_FILE)
 
# attempt to bring host DISPLAY/xauth to container

rm -f $XAUTH_FILE && touch $XAUTH_FILE
DOCKER_XAUTH=$(xauth list $DISPLAY | awk '{print $3}')
DOCKER_DISPLAY=$DISPLAY

# assume that <hostname>:# displays are TCP displays, use docker host IP as display in container
# this requres sshd_config option "X11UseLocalhost no"
if [[ $DISPLAY == $(hostname)* ]]; then
	DOCKER_DISPLAY="172.17.0.1:$(echo $DISPLAY | cut -d : -f 2)"
fi

# if we have no magic cookie (e.g. bad DISPLAY, or wide-open DISPLAY), just bail
if [ "$DOCKER_XAUTH" == "" ]; then
	echo $DOCKER_DISPLAY
	exit
fi

# if DISPLAY is just :# (no hostname), assume this is a local unix-socket X11 server
if [[ $DOCKER_DISPLAY == :* ]]; then
	xauth -f $XAUTH_FILE add $CONTAINER_HOSTNAME/unix$DOCKER_DISPLAY . $DOCKER_XAUTH
else
	xauth -f $XAUTH_FILE add $DOCKER_DISPLAY . $DOCKER_XAUTH
fi

echo $DOCKER_DISPLAY