gummy

gummy is a simple screen manager for Linux. It provides an easy-to-use CLI for quickly modifying:

• backlight brightness
• pixel brightness
• color temperature

Automatic adjustments are also available, based on any of these inputs:

• ALS: your laptop's ambient light sensor, if available.
• Screenlight: screen lightness, i.e. the brightness of the contents being displayed on your screen.
• Time: a time range for the day (e.g. from 06:00 to 18:00).

Wayland

gummy works on Wayland as of version 0.5.2. However, the following features do not work yet:

• pixel brightness
• color temperature
• screenlight

Installation

Debian users: the Debian package is provided by me for convenience. It's based on Ubuntu 22.04 and may not work on your particular Debian-based distro. Maintainers welcome!

NixOS users: you must add the following line to configuration.nix: services.udev.packages = [ pkgs.gummy ];

gummy uses the ddcutil library on your system for managing backlights of external monitors. The kernel module i2c-dev is needed if you want this functionality.

i2c-dev is built-in in some distributions. Otherwise, you must load it explicitly. This guide shows you how to load it automatically.

You can quickly load it with the command: sudo modprobe i2c-dev. This method does not survive a system reboot, however.

Until ddcutil 1.4+, you must add your user to the "i2c" group for rootless operation.

sudo usermod <user-name> -aG i2c

Generally, a reboot is recommended to ensure gummy can operate your screens without elevated privileges.

Usage

Type gummy -h to print all the available options.

Screen settings are applied to all screens, unless the -s option with a screen number (starting from 0) is provided. All relevant settings can be increased or decreased by prefixing the value with a "+" or "-" sign.

Quick guide:

Troubleshooting

If you experience screen flickering: disable any program that might change screen gamma, such as Redshift. Some system daemons might also cause screen flickering, such as colord. Check if it's running in your system, and try disabling it. I may add functionality to disable gamma control in the future (while keeping backlight control), so that gummy can work with any other gamma-adjusting software.

If backlight adjustments don't work, make sure DDC/CI is enabled in your screen's control panel. Your screen might not support DDC/CI: in that case, you might want to use pixel brightness as a substitute.

Building from source

System requirements:

• C++20 compiler
• CMake v3.14 or later
• libxcb (with extensions: randr, shm, image)
• libsystemd
• libsdbus-c++
• libddcutil

Apt packages

sudo apt install build-essential cmake libxcb1-dev libxcb-randr0-dev libxcb-shm0-dev libxcb-image0-dev libsystemd-dev libsdbus-c++-dev libddcutil-dev

Installation

git clone https://github.com/Fushko/gummy.git --depth 1 && cd gummy
mkdir build && cd build
cmake .. -DCMAKE_INSTALL_PREFIX=/usr/local -DCMAKE_BUILD_TYPE="Release"
cmake --build . -j && sudo cmake --install .

Credits

This project makes (hopefully good) use of these excellent libraries:

• JSON [MIT]
• fmt [MIT]
• spdlog [MIT]
• CLI11 [BSD-3-clause]
• libxcb [MIT]
• libsystemd [GPLv2]
• libddcutil [GPLv2]

Temperature adjustments use the color ramp provided by Ingo Thies for Redshift.

Donations

You can buy me a coffee at: https://coindrop.to/fushko

License

Copyright 2021-2023 Francesco Fusco

Released under the terms of the GNU General Public License v3.0.