Toggle Grayscale Effect in Plasma Desktop KWin with adjusted gamma (X11)

kwin_grayscale_toggle.sh

#!/bin/bash

# PREREQUISITES
# - KWin Grayscale Effect
#   https://store.kde.org/p/1263836/
#   install it via System Settings -> Workspace Behavior -> Desktop Effects [Get New Desktop Effects...] and search for "Grayscale Effect"
#   OR ALTERNATIVELY
#   install it from command line:
#   /usr/lib/kf5/kpackagehandlers/knshandler kns://plasmoids.knsrc/api.kde-look.org/1263836
#
# - xgamma command 
#   part of xorg-xgamma system package on Arch Linux

# If the KWin Grayscale effect is enabled, turn it off and set display gamma to 1.00
if [[ $(qdbus org.kde.KWin /Effects isEffectLoaded "kwin4_effect_grayscale") = true ]]; then
	xgamma -gamma 1.00 -q
	qdbus org.kde.KWin /Effects toggleEffect "kwin4_effect_grayscale"
else
	# otherwise set gamma to 0.90 and enable the effect
	xgamma -gamma 0.90 -q
	qdbus org.kde.KWin /Effects toggleEffect "kwin4_effect_grayscale"
fi

# OPTIONAL BUT STRONGLY RECOMMENDED
# - place the script somewhere where you can find it, mark it as executable with "chmod +x scriptname.sh"
# - configure global custom shortcut in Plasma pointing to this script
#   https://docs.kde.org/trunk5/en/kde-workspace/kcontrol/khotkeys/index.html