BrightnessControl

A command-line tool for adjusting screen brightness on Linux systems using Xorg. Unlike traditional backlight controls, BrightnessControl uses xrandr to modify display brightness at the software level, giving you fine-grained control over your monitors.

Features

• Per-monitor brightness control - Set different brightness levels for each connected display
• Smooth brightness transitions - Gradual fading between brightness levels
• Blue light filter - Built-in night light functionality using xrandr or redshift
• Multi-monitor support - Control all monitors simultaneously or target specific displays
• Daemon architecture - Fast, responsive brightness adjustments with persistent settings

Requirements

• Linux with Xorg (Wayland not supported)
• xrandr (usually pre-installed)
• redshift (optional, for enhanced blue light filtering)

Installation

Option 1: Pre-compiled Binaries (Recommended)

Download the latest binary from GitHub Releases and place it in your PATH.

Option 2: Build from Source

1. Install Rust:

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

2. Install runtime dependencies:

# Ubuntu/Debian
sudo apt install x11-xserver-utils redshift

# Arch Linux
sudo pacman -S xorg-xrandr redshift

3. Build and install:

cargo install --path . --root ~/.local/

Make sure ~/.local/bin is in your PATH.

Quick Start

1. Start the daemon:

brightness_control daemon --start

2. Adjust brightness:

# Increase brightness by 10%
brightness_control brightness --increment 10

# Set brightness to 50%
brightness_control brightness --set 50

# Decrease brightness by 5%
brightness_control brightness --decrement 5

3. Toggle night light:

brightness_control nightlight --toggle

Usage Examples

Basic Brightness Control

# Using full commands
brightness_control brightness --increment 10
brightness_control brightness --set 80

# Using shortcuts (same functionality)
brightness_control b -i10
brightness_control b -s80

Multi-Monitor Control

# Control all connected monitors
brightness_control --enabled brightness --set 70

# Control specific monitor
brightness_control --monitor eDP-1 brightness --increment 15

# Control the "active" monitor (BrightnessControl's concept)
brightness_control --active brightness --decrement 5

Advanced Features

# Set brightness without smooth fading
brightness_control b --no-fade --set 60

# Interrupt current fade and change brightness
brightness_control b --terminate-fade --increment 10

# Get current brightness levels
brightness_control get --brightness

# List connected displays
brightness_control get --displays

Monitor Management

# Refresh display configuration (after connecting/disconnecting monitors)
brightness_control monitors --reconfigure-displays

# Set active monitor for --active flag
brightness_control monitors --set-active HDMI-1

Configuration

BrightnessControl stores its configuration in ~/.config/brightnesscontrol/config.toml. The daemon creates this file with default settings on first run.

To see all available options:

brightness_control config --print-config-template

To reload configuration without restarting:

brightness_control config --reload

Key Configuration Options

• Brightness fading: Control smooth transitions between brightness levels
• Blue light filter: Choose between xrandr (default) or redshift
• Auto-remove displays: Automatically handle disconnected monitors
• Default monitor behavior: Set how commands apply to monitors by default

Configuring Redshift

To allow brightness_control to use redshift as a blue light filter while still using xrandr for brightness control, you must change redshift's adjustment mode away from randr to vidmode.

sed -i 's/adjustment-method=randr/adjustment-method=vidmode/' ~/.config/redshift.conf

Keybinding Setup

For convenient daily use, bind these commands to keyboard shortcuts using your desktop environment's settings or tools like xbindkeys:

# Example keybindings
Alt+PageUp     → brightness_control b -i10    # Increase brightness
Alt+PageDown   → brightness_control b -d10    # Decrease brightness
Alt+End        → brightness_control n -t      # Toggle night light
Alt+Home       → brightness_control m -r      # Refresh displays

Troubleshooting

Daemon won't start: Check if another instance is running with killall brightness_control

No brightness change: Ensure xrandr works directly and your display supports software brightness control

Monitor not detected: Run brightness_control monitors --reconfigure-displays after connecting new displays

How It Works

BrightnessControl uses a client-daemon architecture. The daemon interfaces with xrandr to modify display gamma/brightness values, while client commands communicate with the daemon for fast response times. Settings are automatically saved and restored between sessions.

This approach provides software-level brightness control that works independently of hardware backlight controls, making it especially useful for external monitors or systems where hardware brightness adjustment isn't available.