Hyprland External Monitor Brightness Control

A simple vibe-coded bash script to control external monitor brightness using DDC/CI commands in Hyprland. Adjusts brightness only on the currently focused monitor.

Features

• Control brightness of the monitor where your cursor is currently located
• Increase or decrease brightness by specified percentage (default 20%)

Prerequisites

1. Install ddcutil

Arch Linux:

sudo pacman -S ddcutil

2. Load i2c-dev Kernel Module

The i2c-dev kernel module is required for DDC communication:

# Load the module temporarily
sudo modprobe i2c-dev

# Make it permanent by adding to modules-load
echo "i2c-dev" | sudo tee /etc/modules-load.d/i2c-dev.conf

3. Set Up Permissions

Add your user to the i2c group to avoid needing sudo:

sudo usermod -a -G i2c $USER

Note: You'll need to log out and back in for group changes to take effect.

4. Install jq (for JSON parsing)

Arch Linux:

sudo pacman -S jq

Installation

1. Download the script:

   curl -o ~/.local/bin/bright https://raw.githubusercontent.com/nasht/bright/main/bright
   chmod +x ~/.local/bin/bright

2. Configure monitor mapping:

   First, identify your monitors:

   # Get Hyprland monitor names
   hyprctl monitors
   
   # Get ddcutil display numbers
   ddcutil detect

   Then edit the script and update the get_active_display() function's case statement to match your setup:

   case "$active_monitor" in
       "DP-1") echo 1 ;;      # Your first monitor
       "HDMI-A-1") echo 2 ;;  # Your second monitor
       *) echo 1 ;;           # Default fallback
   esac

Usage

# Increase brightness by 20% (default)
bright +

# Decrease brightness by 20%
bright -

# Increase brightness by 10%
bright + 10

# Decrease brightness by 5%
bright - 5

Hyprland Keybinding Setup

Add these keybindings to your ~/.config/hypr/hyprland.conf:

# Monitor brightness controls
hyprctl monitors

After adding the keybindings, reload your Hyprland config:

binde = CTRL, F1,  exec, ~/bin/bright -
binde = CTRL, F2,  exec, ~/bin/bright +

Troubleshooting

"No displays detected" error

1. Check if i2c-dev module is loaded:

   lsmod | grep i2c_dev

2. Verify i2c devices exist:

   ls -la /dev/i2c-*

3. Test ddcutil detection:

   ddcutil detect

Permission denied errors

1. Check group membership:

   groups $USER

   Should include i2c group.

2. Check device permissions:

   ls -la /dev/i2c-*

3. If still having issues, try udev rules:

   echo 'KERNEL=="i2c-[0-9]*", GROUP="i2c", MODE="0660"' | sudo tee /etc/udev/rules.d/45-ddcutil-i2c.rules
   sudo udevadm control --reload-rules && sudo udevadm trigger

Monitor not responding

Some monitors don't support DDC/CI or have it disabled:

1. Check monitor OSD settings for DDC/CI enable option
2. Try different cables (some USB-C to DisplayPort adapters don't support DDC)
3. Test with a different VCP code:

   ddcutil capabilities

Script runs but brightness doesn't change

1. Verify the monitor mapping in the script matches your setup
2. Test ddcutil manually:

   ddcutil --display 1 getvcp 10
   ddcutil --display 1 setvcp 10 50

Contributing

Feel free to submit issues and pull requests to improve the script or documentation.

License

MIT License - feel free to modify and distribute.