#!/bin/bash

# Don't start a new transition if the previous one isn't done yet
pgrep -u $UID -x xbacklight >/dev/null && exit

# Calculate new target brightness
current_brightness=$(xbacklight -get)
case $1 in
	up)
		target=$((current_brightness * 15 / 10))
		[ $target -ne $current_brightness ] || target=$((target + 1))
		;;
	down)
		target=$((current_brightness * 10 / 15))
		[ $target -ne $current_brightness ] || target=$((target - 1))
		;;
esac

# Boundaries: can't go higher than 100% or lower than 1%
[ $target -le 1   ] && target=1
[ $target -ge 100 ] && target=100

# Smoothly set the new brightness
xbacklight -time 100 -fps 42 -set $target