jamerst / brightnessd

A simple Python daemon for controlling display brightness via DDC/CI with DBus messages

brightnessd

A simple Python daemon for controlling display brightness via DDC/CI with DBus messages.

Installation

Dependencies

brightnessd requires the following packages to be installed:

• monitorcontrol
• dasbus

Both of these packages can be installed from PyPI with pip.

Service

brightnessd is designed to be run as a user service with systemd. To set it up perform the following steps:

1. Copy brightnessd.py to a location in your home directory, I would recommend ~/.local/bin/.
2. Modify the ExecStart line of brightnessd.service to point to the location of brightnessd.py. Note that this must be an absolute path, it cannot be relative or use variables such as $HOME.
3. Copy brightnessd.service to ~/.local/share/systemd/user/
4. Run systemctl --user enable brightnessd systemctl --user start brightnessd to enable and start the daemon

Usage

brightnessd supports both manual brightness changing and automatic fading. Interaction is through the net.jtattersall.brightness DBus Service.

ChangeBrightness

The net.jtattersall.brightness.ChangeBrightness(amount: int) method allows you to change the brightness of all connected monitors by a given percentage.

Note that calling ChangeBrightness will stop a fade if one is currently in progress.

Example:

dbus-send --print-reply --dest=net.jtattersall.brightness /net/jtattersall/brightness net.jtattersall.brightness.ChangeBrightness int32:-5

This command will decrease the brightness of all monitors by 5%.

The method returns an array of integers, which is the new brightness of each monitor.

Fade

The net.jtattersall.brightness.Fade(target: int, time: int) method automatically fades the brightness of all monitors to target over time seconds in steps of +-1%. This method is asynchronous, it returns early but continues to fade on a background thread.

Note that only one fade can be in progress at once. If Fade could be called again before time has elapsed, be sure to call Stop before calling Fade.

Example:

dbus-send --print-reply --dest=net.jtattersall.brightness /net/jtattersall/brightness net.jtattersall.brightness.Fade int32:20 int32:60

This command will change the brightness of all monitors to 20%, taking 60 seconds.

Stop

The net.jtattersall.brightness.Stop method stops any fades which are currently in progress. You should make sure to call this before Fade if it is possible for Fade to be called again before the time has elapsed.

Troubleshooting

DDC/CI can be a troublesome protocol. Some monitors just don't support it very well. Before using the daemon I would recommend using a tool like ddcutil to check that your monitor supports DDC/CI and to get your environment set up correctly.

To be able to use DDC/CI without root you may have to follow this guide.