#!/bin/sh -e

# xvfb-run - run the specified command in a virtual X server

# This script starts an instance of Xvfb, the "fake" X server, runs a
# command with that server available, and kills the X server when
# done.  The return value of the command becomes the return value of
# this script.
#
# If anyone is using this to build a Debian package, make sure the
# package Build-Depends on xvfb and xfonts-base.
#
# If anyone is using this to build an ALT Linux package, make sure the
# package BuildRequires XFree86-Xvfb and XFree86-utils.

DISPLAYNUM=90
STARTWAIT=5
LISTENTCP="-nolisten tcp"
AUTODISPLAYNUM=n

usage()
{
  echo "Usage: $0 [OPTION]... [command]"
  echo
  echo "run specified X client or command in a virtual X server environment"
  echo
  echo "  -a --auto-displaynum      Try to get a free display number, starting at --display-num"
  echo "  -n --display-num=NUM      Display number to use (default:$DISPLAYNUM)"
  echo "  -l --listen-tcp           Enable TCP port listening in the X server"
  echo "  -t --timeout=DELAY        Timeout in seconds to wait for Xvfb to start (default:$STARTWAIT)"
  echo "  -h --help                 Display this help and exit"
}

force_kill_xvfb() {
	kill $XVFBPID 2> /dev/null ||:
}

# Start an Xvfb server process in the background
# using the display number passed as a parameter.
# Perform checks to guard against a premature server exit or a display hijack.
# Set the XVFBPID variable to the PID of the server started.
start_xvfb() {
	local dispnum=$1

	# start Xvfb in the background and wait a little
	Xvfb :$dispnum -screen 0 640x480x8 $LISTENTCP > /dev/null 2>&1 &
	XVFBPID=$!

	# poll for the server lock file to appear
	local countdown=$STARTWAIT
	while [ ! -r /tmp/.X$dispnum-lock ]; do
		if [ $countdown = 0 ]; then
			echo "$0: can't access lockfile /tmp/.X$dispnum-lock" >&2
			force_kill_xvfb
			return 2
		fi
		sleep 1
		countdown=$((countdown-1))
	done

	# check if it really is our process behind the display
	if [ ! -O /tmp/.X$dispnum-lock ]; then
		echo "$0: can't obtain lockfile /tmp/.X$dispnum-lock" >&2
		force_kill_xvfb
		return 1
	fi
	local lockpid
	read lockpid < /tmp/.X$dispnum-lock
	if [ "$XVFBPID" != "$lockpid" ]; then
		echo "$0: display :$dispnum has been taken by another process" >&2
		force_kill_xvfb
		return 1
	fi

	# Poll for the X server socket to be established
	while [ ! -O /tmp/.X11-unix/X$dispnum ]; do
		if [ $countdown = 0 ]; then
			echo "$0: can't access socket for display :$dispnum" >&2
			force_kill_xvfb
			return 2
		fi
		sleep 1
		countdown=$((countdown-1))
	done

	# finally, check that the server has not exited
	if ! kill -0 $XVFBPID 2>/dev/null; then
		echo "$0: Xvfb server has died" >&2
		return 2
	fi

	return 0
}

# Shut down the Xvfb server whose PID is in the XVFBPID variable
shutdown_xvfb() {
	kill $XVFBPID ||:
}


# Parse command line
ARGS=`getopt --options +an:lt:w:h \
	--long auto-displaynum,display-num:,listen-tcp,timeout:,wait:,help \
	--name "$0" -- "$@"`
eval set -- "$ARGS"
while true ; do
    case "$1" in
      '-a'|'--auto-displaynum')
      	    AUTODISPLAYNUM=y
      	    ;;
      '-n'|'--display-num')
	    DISPLAYNUM="$2"
	    shift
	    ;;
      '-l'|'--listen-tcp')
	    LISTENTCP=
	    ;;
      '-t'|'--timeout'|'-w'|'--wait')
	    STARTWAIT="$2"
	    shift
	    ;;
      '-h'|'--help')
	    usage
	    exit 1
	    ;;
      '--')
	    # end of options
	    shift
	    break
	    ;;
    esac

    shift
done

# create the transient authority file
AUTHFILE=$(mktemp -t xvfb-run.XXXXXXXX)
XAUTHORITY="$AUTHFILE"
export XAUTHORITY
MCOOKIE=$(mcookie)

# The main loop increments display numbers
while true ; do
	# check for the X server lock file
	if [ -f /tmp/.X$DISPLAYNUM-lock ]; then
		if [ $AUTODISPLAYNUM = y ]; then
			DISPLAYNUM=$((DISPLAYNUM+1))
			continue
		else
			echo "$0: lock file exists for display $DISPLAYNUM" >&2
			RETVAL=1
			break
		fi
	fi

	# set up an X authority cookie
	xauth add :$DISPLAYNUM . $MCOOKIE >/dev/null 2>&1

	# start Xvfb
	start_xvfb $DISPLAYNUM
	XVFBSTATUS=$?
	case $XVFBSTATUS in
	    0)
		# run the command and save its exit status
		set +e
		DISPLAY=:$DISPLAYNUM "$@"
		RETVAL=$?
		set -e
		# kill Xvfb
		shutdown_xvfb
		break
		;;
	    1)
		# a non-fatal startup failure
		# (can fall back to other display number)
		if [ $AUTODISPLAYNUM != y ]; then
			RETVAL=$XVFBSTATUS
			break
		fi
		;;
	    2)
		# a fatal startup failure
		RETVAL=$XVFBSTATUS
		break
		;;
	esac

	# clean up
	xauth remove :$DISPLAYNUM >/dev/null 2>&1

	# continue with the next display number
	DISPLAYNUM=$((DISPLAYNUM+1))
done

# remove the authority file
rm -f "$AUTHFILE"

# return the executed command's exit status
exit $RETVAL