Software brightness control for Hyprland via hyprsunset — gamma dimming with warm color shift at low levels

brightness

#!/bin/bash
# Software brightness control via hyprsunset
# Usage: brightness up|down|set <value>
# Stores state in ~/.local/state/brightness
#
# Two phases:
#   100% → 15%: reduce gamma (dims the screen while maintaining contrast)
#   15% → 0%:   gamma stays at 15%, temperature shifts warm (6500K → 2000K)
#               This "dims" further by removing blue light, keeping readability

STATE_FILE="$HOME/.local/state/brightness"
STEP=5
MIN=0
MAX=100

# Below this gamma level, stop dimming and start warming instead
GAMMA_FLOOR=20

# Warm color temp range
TEMP_NEUTRAL=6500
TEMP_WARMEST=2000

# Read current brightness
if [[ -f "$STATE_FILE" ]]; then
    current=$(cat "$STATE_FILE")
else
    current=100
fi

case "$1" in
    up)
        new=$((current + STEP))
        [[ $new -gt $MAX ]] && new=$MAX
        ;;
    down)
        new=$((current - STEP))
        [[ $new -lt $MIN ]] && new=$MIN
        ;;
    set)
        new=$2
        [[ $new -gt $MAX ]] && new=$MAX
        [[ $new -lt $MIN ]] && new=$MIN
        ;;
    get)
        echo "$current"
        exit 0
        ;;
    *)
        echo "Usage: brightness up|down|set <value>|get"
        exit 1
        ;;
esac

# Save new value
echo "$new" > "$STATE_FILE"

# Calculate gamma and temperature
if [[ $new -ge $GAMMA_FLOOR ]]; then
    # Phase 1: normal dimming, neutral color
    gamma=$new
    temp=$TEMP_NEUTRAL
else
    # Phase 2: gamma stays at floor, temperature goes warm
    gamma=$GAMMA_FLOOR
    # Linear interpolation: at 15% = 6500K, at 0% = 2000K
    temp_range=$((TEMP_NEUTRAL - TEMP_WARMEST))
    progress=$((GAMMA_FLOOR - new))
    temp=$((TEMP_NEUTRAL - (progress * temp_range / GAMMA_FLOOR)))
fi

# Apply via hyprsunset (kill existing instance first)
pkill -x hyprsunset 2>/dev/null
sleep 0.1

if [[ $gamma -ge 100 && $temp -eq $TEMP_NEUTRAL ]]; then
    # Full brightness, no color shift — no need for hyprsunset
    :
else
    hyprsunset -g "$gamma" -t "$temp" &>/dev/null &
    disown
fi

# Show OSD notification
if [[ $new -ge $GAMMA_FLOOR ]]; then
    notify-send -t 1000 -h string:x-canonical-private-synchronous:brightness \
        -h int:value:"$new" "Brightness ${new}%"
else
    notify-send -t 1000 -h string:x-canonical-private-synchronous:brightness \
        -h int:value:"$new" "Brightness ${new}% (${temp}K)"
fi