scaleapp

#!/bin/bash
#
# scaleapp - Run an X11 application in a scaled view using XPRA from xpra.org
#
# Requirements:
#   - Arch packages: xpra-winswitch, gtkglext, python2-gtkglext
#   - file /etc/X11/Xwrapper.config with line 'allowed_users=anybody'
#
# Usage:
#      scaleapp <command> [args...]  
#                           to run <command> with a scaling factor.
#                           This will spawn a background display server during
#                           the first invokation which will remain active even
#                           after the command finsihes. 
#  or  scaleapp --stop      to stop the background display server again
#
# Environment:
#   SCALEAPP_FACTOR=<number>      the scaling factor. Default: 2
#   SCALEAPP_DISPLAYNO=<number>   the DISPLAY number for the background display
#                                 server. Default: 100
#

scalingfactor=${SCALEAPP_FACTOR:-2}
displayno=${SCALEAPP_DISPLAYNO:-100}

displaystr=":${displayno}"
stop=false

usage="Usage: scaleapp [options] <command> [args...]"


help() {
  echo -e "scaleapp - Run an X11 application in a scaled view using XPRA"
  echo -e ""
  echo -e "$usage"
  echo -e ""
  echo -e "  Runs <command> with optional arguments [args] in a background display server,"
  echo -e "  redirects all output to the current display server and scales its display by"
  echo -e "  a certain scaling factor given in environment variable SCALEAPP_FACTOR."
  echo -e ""
  echo -e "Options:"
  echo -e "  -s|--stop  Stop any running background display server before continuing."
  echo -e "             Use --stop without <command> to clean up."
  echo -e "             Attention: this also kills any running applications started"
  echo -e "             with scaleapp!"
  echo -e "  -h|--help  Display this help"
  echo -e ""
  echo -e "Environment:"
  echo -e "  SCALEAPP_FACTOR=<num>     scaling factor (default: ${scalingfactor})"
  echo -e "  SCALEAPP_DISPLAYNO=<num>  display number for the background display server"
  echo -e "                            (default: ${displayno})"
  echo -e ""
  exit
}

error() {
  local msg="$1"; shift
  echo -e "\033[0;31mError: ${msg}\033[0m\n" 1>&2
  exit 1
}


# parse command line arguments
case "$1" in
  -h|--help) help; exit;;
  -s|--stop) stop=true; shift;;
  (-*) error "unrecognized option: $1\n\n$usage";;
esac


# fix clipboard warning
export XPRA_CLIPBOARD_LIMIT=1000


# function to check if xpra server is running
check_xpra_server_running() {
  local tries="${1:-1}" # number of tries (default 1)
  local invert=$2       # if non null invert logic (check if _not_ running)
  local retval
  for ((i=1;i<=tries;i++)); do
    retval=$(xpra info $displaystr >/dev/null)$?
    [[ -z "$invert" && $retval -eq 0 ]] && break
    [[ -n "$invert" && $retval -gt 0 ]] && break
    sleep 1
  done
  echo $retval
}


# stop if requested
if [ "$stop" = true ]; then
  if [ $(check_xpra_server_running 1 not) -eq 0 ]; then
    echo "Stopping display $displaystr on request..."
    xpra stop $displaystr
    # wait 5 retries until server not available
    check_xpra_server_running 5 not >/dev/null
  else
    echo "Stop requested for display $displaystr but server is not running -- skipped."
  fi
fi


# if we do not have a command we can exit here
if [ $# -eq 0 ]; then
  echo "No command given, nothing to do. ;)"
  exit
fi


# check if display server is already running
if [ $(check_xpra_server_running) -ne 0 ]; then
  echo -e "Display server on $displaystr apparently not running. Starting..."
  xpra start $displaystr --dpi=96
  echo -e "\nCheck if running..."
  if [ $(check_xpra_server_running 10) -ne 0 ]; then
    errtext="Could not start command \"$1\".\n\nReason: could not attach to background display server."
    zenity --error --title=scaleapp --text="$errtext" &
    error "$errtext"
  fi
  echo -e "\nAttaching..."
  xpra attach $displaystr --dpi=96 --desktop-scaling=$scalingfactor &
fi


# now execute command on scaled display
DISPLAY=$displaystr exec "$@"