Linux XFCE scripts for changing xrandr and dpi settings on hdmi toggle

10-hdmi-dpi.rules

#/etc/udev/rules.d/10-hdmi-dpi.rules
KERNEL=="card0", ACTION=="change", RUN+="/home/hxss/.config/scripts/xorg/hdmi.sh"

hdmi-config.service

#/home/hxss/.config/systemd/user/hdmi-config.service

[Unit]
Description=Run HDMI configuration

[Service]
ExecStart=/home/hxss/.config/scripts/xorg/hdmi.sh

hdmi.sh

#!/bin/sh

hdmiState=`cat /sys/class/drm/*HDMI*/status`

function chngDPI() {
	case "$hdmiState" in
		"connected")
			scale=1
			dpi=96
			;;
		*)
			scale=1.4
			dpi=124
			;;
	esac

	# dconf write /org/cinnamon/desktop/interface/text-scaling-factor $scale
	logger -p info "dpi: $dpi"
	xfconf-query -c xsettings -p /Xft/DPI -s $dpi
}

function xrandr_restore()
{
	params=''
	for display in `xfconf-query -c displays -l | perl -ne '/\/Default\/([^\/]*)\n/ and print "$1\n"'`
	do
		active=`xfconf-query -c displays -p /Default/$display/Active`
		$active && state="auto" || state="off"
		posx=`xfconf-query -c displays -p /Default/$display/Position/X`
		posy=`xfconf-query -c displays -p /Default/$display/Position/Y`

		params="${params}--output $display --$state --pos ${posx}x${posy} "
	done

	logger -p info "xrandr $params"
	xrandr $params
}

function xfce_xrandr() {
	logger -p info "xfce_xrandr; HDMI $hdmiState"
	case "$hdmiState" in
		"connected") xrandr_restore ;;
		*)           xrandr --auto  ;;
	esac
}

logger -p info "${BASH_SOURCE[0]}"

user=`stat -c %U $0`

if [ "$user" == `whoami` ]; then
	chngDPI
	xfce_xrandr
elif [ "`w -hs $user`" ]; then
	machinectl shell --uid=$user .host /usr/bin/systemctl --user --no-block start hdmi-config.service
fi

I'm looking for a script to scale up XFCE when i enable a display profile with my 4K TV. Could you explain what this does in more detail?

this script toggle dpi and apply xrandr settings from xfconf when you insert hdmi cable