DDC Automatic Brightness

A GTK application for controlling external monitor brightness using DDC/CI with automatic adjustment capabilities.

Features

Automatic Brightness Control

• Ambient light sensor-based adjustment with configurable curves
• Follow main/internal monitor brightness
• Time-based scheduled brightness throughout the day
• Smooth gradual transitions

Monitor Control

• Manual brightness adjustment via slider
• Support for multiple external monitors
• Per-monitor configuration and settings
• Real-time hardware detection (with udev)

Installation

Download pre-built package (easiest)

Download the latest .deb from the Releases page and install:

sudo apt install ddccontrol          # runtime dependency
sudo dpkg -i ddc-automatic-brightness-gtk_*.deb

Build from source

Prerequisites

# Ubuntu/Debian (Required)
sudo apt install build-essential libgtk-3-dev libglib2.0-dev libayatana-appindicator3-dev ddccontrol

# Ubuntu/Debian (Optional - for hardware auto-detection)
sudo apt install libudev-dev

# Fedora
sudo dnf install gcc gtk3-devel glib2-devel libayatana-appindicator-gtk3-devel ddccontrol libudev-devel

# Arch Linux
sudo pacman -S base-devel gtk3 glib2 libayatana-appindicator ddccontrol systemd-libs

Build and install

cd src/
make check-deps  # Verify all dependencies
make             # Build the application

# Install system-wide
sudo make install

# Or create package for distribution
make package
sudo dpkg -i ddc-automatic-brightness-gtk_[version]_amd64.deb

Usage

Command Line Options

./ddc-automatic-brightness-gtk [options]

Options:
  --tray, --minimized  Start minimized to system tray
  --no-gui             Run in background (tray only)
  --help, -h           Show help

GUI Controls

Monitor Selection: Choose your external monitor from dropdown

Manual Control: Use slider for immediate brightness adjustment

Auto Brightness Modes:

• Ambient Light Sensor: Automatic adjustment based on ambient light
• Follow Main Monitor: Match internal/main monitor brightness
• Time Schedule: Follow daily brightness schedule

Configuration Dialogs:

• Configure Light Sensor Curve: Visual graph with lux-to-brightness mapping
• Configure Schedule: 24-hour brightness timeline with visual graph
• Luminosity Sensitivity: Adjust hysteresis to prevent flickering (0-100 lux)

Configuration

Settings stored in ~/.config/ddc-automatic-brightness/config.ini:

Technical Details

Architecture

src/
├── main.c                  # Application core and tray integration
├── brightness_control.c    # DDC/CI monitor communication
├── monitor_detect.c        # Monitor discovery and management
├── light_sensor.c          # Ambient light sensor integration
├── laptop_backlight.c      # Internal monitor brightness reading
├── scheduler.c             # Time-based brightness scheduling
├── config.c                # Configuration management
├── *_dialog.c              # Configuration UI dialogs
└── *.h                     # Header files

Dependencies

• GTK 3.0: GUI framework
• GLib 2.0: Core utilities and configuration
• libayatana-appindicator3: System tray support
• ddccontrol: DDC/CI monitor communication
• libudev (optional): Hardware auto-detection
• Cairo: Graph rendering

Ambient Light Sensor Requirements

Requires IIO (Industrial I/O) ambient light sensor via /sys/bus/iio/devices/. Supported on laptops with built-in ALS hardware.

Troubleshooting

No Monitors Detected

# Test ddccontrol directly
sudo ddccontrol -p

# Check permissions
sudo usermod -a -G i2c $USER
# Log out and back in

# Manual refresh in GUI
Click "Refresh Monitors" button

Brightness Not Changing

# Verify DDC/CI support
sudo ddccontrol dev:/dev/i2c-X -r 0x10

# Check monitor is available
The app shows monitor status in the dropdown

No Tray Icon

# Install tray support
sudo apt install libayatana-appindicator3-dev

# Rebuild
make clean && make

Hardware Auto-Detection Not Working

# Install udev development headers
sudo apt install libudev-dev

# Rebuild with hardware detection
make clean && make check-deps && make

License

GNU General Public License v2.0