detect_screen

#!/bin/bash
#
# Copyright (C) 2017 barbUk
#
# This program is free software: you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free Software
# Foundation, either version 3 of the License, or (at your option) any later
# version.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along with
# this program. If not, see <http://www.gnu.org/licenses/>.
#
# =================================
# Put this script in your path, make it executable
# and add a new udev rule in /etc/udev/rules.d/99-monitor.rules:
# ACTION=="change", SUBSYSTEM=="drm", ENV{HOTPLUG}=="1", ENV{XAUTHORITY}="/home/user/.Xauthority", RUN+=detect-screen"
#
set -o errexit -o pipefail -o nounset

# shellcheck disable=2012
displaynum=$(ls /tmp/.X11-unix/* | sed s#/tmp/.X11-unix/X##)
DISPLAY=":$displaynum"
XAUTHORITY="${XAUTHORITY:-$HOME/.Xauthority}"

primary_screen=$(DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY xrandr | awk '/\<connected primary\>/ {print $1}')
connected_screens=$(DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY xrandr | awk '/\<connected\>/ && !/primary/  {print $1}')
other_screens=$(DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY xrandr | awk '!/^[[:blank:]]/ && $1 !~ /^Screen$/ && $3 !~ /primary/ {print $1}')

if [[ "$connected_screens" == VGA* ]] || [[ "$connected_screens" == DP* ]] || [[ "$connected_screens" == HDMI* ]]; then
  DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY xrandr --output "$primary_screen" --primary --output "$connected_screens" --left-of "$primary_screen" --auto
else
  off=()
  for output in $other_screens; do
    off+=(--output "$output" --off)
  done
  DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY xrandr --output "$primary_screen" --primary "${off[@]}"
fi