dotfiles/.local/bin/sx

#!/bin/sh --
set -u
# sx - start an xorg server
# https://github.com/Earnestly/sx

: "${SX_CLIENT_SIGNAL:=TERM}"
: "${SX_CLIENT_STOP_CMD:=:}"
: "${SX_LOCK:=${XDG_RUNTIME_DIR:-${TMPDIR:-/tmp}/runtime-${USER:-$(id -un)}}/sx.lock}"

unexport_env() {
	unset SX_LOCK
	unset SX_CLIENT_SIGNAL
	unset SX_CLIENT_STOP_CMD

	"${@}"
}

local_kill() {
	pid="${1:?}"
	shift

	kill -0 "${pid}" 2>/dev/null && {
		kill "${@}" "${pid}"
		wait "${pid}"
		local_kill_exit="${?}"
	}
}

CLEANUP_DONE=0
cleanup() {
	if [ "${CLEANUP_DONE}" -eq 1 ]; then
		return
	fi

	if [ -n "${SX_CLIENT_STOP_CMD}" ] && [ "${SX_CLIENT_STOP_CMD}" != : ]; then
		${SX_CLIENT_STOP_CMD}
	else
		local_kill "${client}" -s "${SX_CLIENT_SIGNAL}"
	fi
	local_kill_exit=0
	local_kill "${server}"

	CLEANUP_DONE=1

	if ! stty "${stty}"; then
		stty sane
	fi

	[ -n "${RMDIR:-}" ] && chmod +w -R "${XAUTHORITY%/*}"
	xauth remove :"${tty}"
	[ -n "${RMDIR:-}" ] && rm -rf "${XAUTHORITY%/*}"
}

usage() {
	printf '%s\n' \
		"Usage: ${0##*/} [action]" \
		'    start <pid> cmd args... - start user services' \
		'    stop  <pid>             - stop user services' \
		'    help                    - show this help'

	exit "${1:-0}"
}

exec 3<>"${SX_LOCK}"

cmd="${1:-}"
shift
case "${cmd}" in
start)
	flock -n 3 || {
		IFS= read -r sx_pid <&3
		echo "sx already running (pid=${sx_pid})" 1>&2
		exit 1
	}

	[ "${#}" -gt 0 ] || {
		echo "please provide command to start after Xorg is ready" 1>&2
		exit 1
	}

	printf '%d\n' "${$}" 1>&3
	;;
stop)
	IFS= read -r sx_pid <&3

	rm -f "${SX_LOCK}" || :
	exec kill "${sx_pid:?}"
	;;
help | -h) usage 0 ;;
*) usage 1 ;;
esac

server=
client=
stty="$(stty -g)"
tty="${TTY:-$(tty)}"
tty="${tty#/dev/tty}"

RMDIR=
[ -n "${XAUTHORITY:-}" ] || {
	XAUTHORITY="$(mktemp --suffix='.Xauthority' -d)/cookie"
	RMDIR=1
}
touch -- "${XAUTHORITY}"
export XAUTHORITY

trap 'cleanup; exit "${local_kill_exit:-0}"' EXIT

# shellcheck disable=2016
trap='cleanup; trap - "${signal}"'
for signal in HUP INT QUIT TERM; do
	# shellcheck disable=2064
	trap "${trap}" "${signal}"
done

# Xorg will return a USR1 signal to the parent process indicating it is ready
# to accept connections if it inherited a USR1 signal with a SIG_IGN
# disposition.  Consequently a client may be started directly from a USR1
# signal handler and obviate the need to poll for server readiness.
trap 'DISPLAY=":${tty}" unexport_env "${@}" 3>&- & wait "${!}"' USR1

xauth add ":${tty}" MIT-MAGIC-COOKIE-1 \
	"$(od -An -N16 -tx /dev/urandom | tr -d ' ')"

if [ -n "${RMDIR:-}" ]; then
	chmod -w -R "${XAUTHORITY%*}"
fi

(
	trap '' USR1 &&
		exec Xorg ":${tty}" "vt${tty}" \
			-auth "${XAUTHORITY}" \
			-arinterval 20 \
			-nolisten tcp \
			-ardelay 200 \
			-keeptty \
			-noreset
) &
server="${!}"
wait "${server}"