startxwin

#!/bin/bash

################################################################################
# Description:
#   startxwin is for use in a WSL environment where an X11 server is required.
#   The server is provided by Cygwin/X. This script is intended to be added to
#   the WSL user's ~/.bashrc file to ensure that an X11 server instance is
#   always running. It does this by calling the same script via cygwin and
#   checking whether an XWin process is running. The server will be started if
#   it is not already running.
#
# Requirements:
#   - WSL (Ubuntu Bionic 18.04) packages: ubuntu-desktop
#   - Cygwin packages: xorg-server, xinit
#
# Installation:
#   - Copy the script to "/c/cygwin/usr/local/bin/startxwin".
#   - Add the line ". /c/cygwin/usr/local/bin/startxwin" to ~/.bashrc
#     Make sure the period is included as the first character of the line.
################################################################################

export DISPLAY=:0

# start cygwin X11 server if we're not in a cygwin environment
if ! uname | grep -q -i 'Cygwin'; then
    ( cmd.exe /v /c 'set HOME=/tmp && C:\cygwin\bin\bash.exe --login -c /usr/local/bin/startxwin' 2>/tmp/X11.log & ) >/dev/null
    xdpyinfo -display $DISPLAY >/dev/null
    return 2>/dev/null || exit 0  # explicit exit return will fail if script not sourced (e.g. debugging)
fi

# otherwise we're in a cywgin environment
log () {
    echo -e "[$(date +'%Y-%m-%d %H:%M:%S')] ${2:-INFO}: $1" >&2
}

start_xwin () {
    readonly local cmd="/usr/bin/XWin $DISPLAY -listen tcp -multiwindow +iglx -nowgl -noprimary >/dev/null 2>&1"
    log "Starting XWin ..."
    log "Command: $cmd"
    eval "$cmd & echo \$!"
    log "Process Id: $!"
}

xwin_pid () {
    ps x | grep [X]Win | awk '{ print $1 }'
}

xwin_running () {
     ps -p $1 >/dev/null
}

XWIN_PID=$(xwin_pid)

if [[ "$XWIN_PID" != "" ]]; then
    log "XWin detected with PID $XWIN_PID"
    exit 0
fi

log "XWin is not running"
XWIN_PID=$(start_xwin)
log "Waiting 0.5 seconds ..."
sleep 0.5

if ! xwin_running $XWIN_PID; then
    log "Failed to start XWin" ERROR
    exit 1
fi

log "XWin is running"