nexoniarz-config-nixos-laptop/modules/scripts/brightness-ctl.sh

#!/usr/bin/env bash
# Brightness control abstraction: prefers the kernel backlight class (laptop
# panels, via brightnessctl); falls back to DDC/CI over I2C (external
# monitors, via ddcutil) when no backlight device exists. Keeps the rest of
# the config (Quickshell's brightness popup) hardware-agnostic.
set -euo pipefail

has_backlight() {
    [ -n "$(ls -A /sys/class/backlight 2>/dev/null)" ]
}

case "${1:-get}" in
    get)
        if has_backlight; then
            brightnessctl -m | cut -d, -f4 | tr -d '%'
        else
            ddcutil getvcp 10 --brief 2>/dev/null | awk '{print $4}'
        fi
        ;;
    set)
        pct="${2:?usage: brightness-ctl set <0-100>}"
        if has_backlight; then
            brightnessctl set "${pct}%" > /dev/null
        else
            ddcutil setvcp 10 "$pct" > /dev/null
        fi
        ;;
    up|down)
        # brightnessctl takes a relative step directly, but ddcutil's
        # setvcp only takes an absolute value — so the DDC/CI path (this
        # machine's AOC 27G2G8 has no backlight device, so it always takes
        # this path) has to read the current level and clamp the step
        # itself.
        step="${2:-5}"
        if has_backlight; then
            if [ "$1" = "up" ]; then
                brightnessctl set "+${step}%" > /dev/null
            else
                brightnessctl set "${step}%-" > /dev/null
            fi
        else
            cur=$(ddcutil getvcp 10 --brief 2>/dev/null | awk '{print $4}')
            cur="${cur:-50}"
            if [ "$1" = "up" ]; then
                new=$(( cur + step > 100 ? 100 : cur + step ))
            else
                new=$(( cur - step < 0 ? 0 : cur - step ))
            fi
            ddcutil setvcp 10 "$new" > /dev/null
        fi
        ;;
    *)
        echo "usage: brightness-ctl [get|set <0-100>|up [step]|down [step]]" >&2
        exit 1
        ;;
esac