ddcbrightness

#!/usr/bin/env bash

## User Configuration #######################################################
conf_step=10
#############################################################################

# Checking Bash version
(( ${BASH_VERSINFO[0]} >= 4 )) || die "This script needs at least bash version 4"

this_basename="${0##*/}"
this_dirname="${0%/*}"

usage() {
    cat <<EOF
Usage: $0 [OPTIONS] <up|down>

Steps DDC brightness up or down for all found DDC displays. DDC brightness means the real physical back lighting.

While laptop screen brightness is already controled directly on most Desktop Environments using special BrightnessUp/Down keys,
this might me useful to control an external HDMI screen brightness on a laptop.
Or to control all 3 screens on DisplayPorts on a desktop system.

As BrightnessUp/Down are often a combination of Fn+F3 and Fn+F4, it's useful to have similar shortcuts like
Super+Alt+F3 and Super+Alt+F4

Usage example: $0 up
Inceasing all found displays brightness by 10 steps

    Options:

    -s, --step              step width (1..50), default: $conf_step

    -d, --debug             Debugging mode
    -h, --help              Show this help
EOF
}

# Checking for ddc binary
ddc_bin="$(type -ap ddcutil)" || die "ddcutil binary not found"

while [[ $1 == -* ]]; do
    case "$1" in
        -s|--step)      shift
                        if [[ $1 == -* || -z $1 ]]; then
                            die "Missing step width"
                        fi
                        if [[ $1 < 1 || $1 > 50 ]]; then
                            die "Step width should be between 1 and 50"
                        fi
                        conf_step="$1"
                        shift;;
        -i|--display)   shift
                        if [[ $1 == -* || -z $1 ]]; then
                            die "Missing display number"
                        fi
                        opt_display="$1"
                        shift;;
        -d|--debug)     opt_debug=1;    shift;;
        -h|--help|-\?)  usage;          exit 0;;
        -*) echo "invalid option: $1" 1>&2; usage; exit 1;;
    esac
done

# Checking action
if [[ -n $1 ]]; then
    if [[ $1 == "up" || $1 == "down" ]]; then
        opt_action="$1"
    else
        die "Action must be 'up' or 'down'"
    fi
else
    die "No action passed"
fi

if [[ -n $opt_display ]];then
    displays=( $opt_display )
else
    readarray -t displays < <(ddcutil detect | awk '/Display/ {print $2}')
    [[ -n $opt_debug ]] && echo "Found displays: ${displays[@]}"
fi

if [[ -n $opt_debug ]]; then
   echo "Action: $opt_action"
   echo "Display: $opt_display"
   echo "Step width: $conf_step"
fi

for display in "${displays[@]}"; do
    current=$(ddcutil --display $display getvcp 10 | sed -n 's/.*current value *= *\([0-9]\+\).*/\1/p')
    
    if [[ $opt_action == "up" ]]; then
        new=$((current + $conf_step))
        if [[ "$new" -gt 100 ]]; then
            new=100
        fi
    elif [[ $opt_action == "down" ]]; then
        new=$((current - $conf_step))
        if [[ "$new" -lt 0 ]]; then
            new=0
        fi
    else
        die "Action $opt_action not supported"
    fi
    
    ddcutil --display $display setvcp 10 $new
    [[ -n $opt_debug ]] && echo "Changed brightness for display $display from $current to $new"
    type -ap notify-send && notify-send -e -t 4000 -i video-display "Changed brightness for display $display from $current to $new"
done