brightness

# -*- mode: sh; -*-

calc() {
    echo "$1" | bc | cut -d. -f1 ;
}

read -r max_br < /sys/class/backlight/intel_backlight/max_brightness

## These are var to fiddle with brightness stepping:
# step_f stepping (factor part)
# step_c stepping (constant part)
step_f="1.25"
step_c=$(calc "$max_br / 200")

## hi_cut and lo_cut guarantee writes to brightness stay in the legal range
hi_cut=$(calc "$max_br / $step_f - $step_c")
lo_cut=$(calc "$step_c * $step_f")

sys_bl="/sys/class/backlight/intel_backlight/brightness"
read -r cur < $sys_bl

case "$1" in
    up)
        if [ "$cur" -gt "$hi_cut" ]; then
            echo "$max_br" > $sys_bl
        elif [ "$cur" -lt "$lo_cut" ]; then
            echo "$lo_cut" > $sys_bl
        else	calc "$cur * $step_f + $step_c" > $sys_bl
        fi
        ;;
    down)
        if [ "$cur" -le "$lo_cut" ]; then
            echo 0 > $sys_bl
        else	calc "$cur / $step_f - $step_c" > $sys_bl
        fi
        ;;
    max)
        echo "$max_br" > $sys_bl
        ;;
    min)
        echo 1 > $sys_bl
        ;;
    off)
        echo 0 > $sys_bl
        ;;
    *)
        echo "Unrecognized brightness command: $1" >&2
esac