session

#!/bin/bash
# The dx Desktop session. ./start runs it under dbus-run-session as the leader
# of a new session; ./stop signals that whole session. It runs a headless
# labwc, the Waymote gateway on 127.0.0.1:5900 (restarted when it exits), a
# foot terminal, and Chromium with DevTools on 127.0.0.1:9222. The session
# ends when labwc exits. stdout and stderr go to session.log.
set -u

desktop=/opt/dx/desktop
state="$HOME/.local/state/dx-desktop"
runtime="$state/runtime"

log() {
  printf '%s session: %s\n' "$(date -u +%FT%TZ)" "$*"
}

failed() {
  printf '%s\n' "$1" >"$state/session.failed"
  log "$1"
  exit 1
}

# Record the session ID (the dbus-run-session leader) for ./start and ./stop.
# Every program in the desktop inherits it as DX_DESKTOP_SESSION, so ./stop
# also finds those that labwc starts in sessions of their own.
sid=$(ps -o sid= -p "$$" | tr -d ' ')
printf '%s\n' "$sid" >"$state/session.pid"
export DX_DESKTOP_SESSION="$sid"

case "${LANG:-}" in
  *.UTF-8 | *.utf8 | *.utf-8 | *.UTF8) ;;
  *) export LANG=C.UTF-8 ;;
esac
export XDG_RUNTIME_DIR="$runtime"
export XDG_SESSION_TYPE=wayland
export XDG_CURRENT_DESKTOP=labwc:wlroots
export WLR_BACKENDS=headless
export WLR_HEADLESS_OUTPUTS=1
export WLR_LIBINPUT_NO_DEVICES=1
export WLR_RENDERER=pixman
export DX_DESKTOP_STATE="$state"
unset DISPLAY WAYLAND_DISPLAY

rm -rf "$runtime" "$state/environment"
mkdir -m 0700 "$runtime" || failed "cannot create $runtime"
for name in waymote chromium foot; do
  file="$state/$name.log"
  if [ -f "$file" ] && [ "$(stat -c %s "$file")" -gt 1048576 ]; then
    mv -f "$file" "$file.1"
  fi
done

stopping=
started=
# shellcheck disable=SC2329 # invoked by the traps below
cleanup() {
  [ -n "$stopping" ] && return
  stopping=1
  # Any exit before the gateway launched (a failed command, an unset
  # variable) is a failed start, which ./start reports at once.
  if [ -z "$started" ] && [ ! -f "$state/session.failed" ]; then
    printf 'the session exited during startup: %s\n' \
      "$(tail -n 1 "$state/session.log" 2>/dev/null | cut -c 1-200)" \
      >"$state/session.failed"
  fi
  trap '' TERM INT HUP
  log "stopping"
  # Every process this script started shares its process group.
  kill -TERM 0 2>/dev/null
  wait
}
trap 'cleanup; exit 0' TERM INT HUP
trap cleanup EXIT

log "starting labwc"
labwc --config-dir "$desktop/labwc" &
labwc_pid=$!

# labwc's autostart (labwc/autostart) writes the display variables once the
# compositor and its Xwayland socket exist.
for _ in $(seq 1 100); do
  [ -f "$state/environment" ] && break
  kill -0 "$labwc_pid" 2>/dev/null || failed "labwc exited during startup"
  sleep 0.1
done
[ -f "$state/environment" ] || failed "labwc did not start within 10s"
# shellcheck disable=SC1091
. "$state/environment"
[ -n "${WAYLAND_DISPLAY:-}" ] || failed "labwc started without a Wayland display"
log "labwc ready: WAYLAND_DISPLAY=$WAYLAND_DISPLAY DISPLAY=${DISPLAY:-}"

# The headless output starts at 1280x720; the viewer may resize it. 30 Hz
# matches the encoder frame rate, so clients render no faster than streamed.
wlr-randr --output HEADLESS-1 --custom-mode 1280x720@30Hz ||
  log "wlr-randr could not set the initial mode"

(
  # No audio source: the gateway then runs no Opus encoder, and the session
  # needs no PulseAudio (deploy/orb/README.md#desktop).
  # bin/ffmpeg keeps the encoder's RTP sockets on loopback.
  export PATH="$desktop/bin:$PATH"
  backoff=1
  while :; do
    started=$SECONDS
    "$desktop/waymote/bin/waymote-gateway" \
      -listen 127.0.0.1:5900 \
      -streamd "$desktop/waymote/bin/waymote-streamd" \
      -bitrate 4000 \
      -frame-rate 30 \
      >>"$state/waymote.log" 2>&1 </dev/null
    status=$?
    if [ $((SECONDS - started)) -gt 60 ]; then
      backoff=1
    fi
    log "waymote-gateway exited with status $status; restarting in ${backoff}s"
    sleep "$backoff"
    backoff=$((backoff * 2 > 30 ? 30 : backoff * 2))
  done
) &

started=1

foot --working-directory="$HOME" >>"$state/foot.log" 2>&1 </dev/null &
# The repository's or project's Desktop resume script, or else Chromium at
# about:blank (./resume).
"$desktop/resume" </dev/null &

while kill -0 "$labwc_pid" 2>/dev/null; do
  wait "$labwc_pid"
done
log "labwc exited"
exit 0