Flash Guard

Flash Guard is an adaptive dimming utility to dynamically darken bright screen contents

why?

As a chronic migraine sufferer, the sudden contrast difference from dark applications to bright white pages is a big trigger.

jUsT uSe DaRk ReAdEr

Sure, I used to use Dark Reader, but there are some issues with it:

1. It doesn't always render images, diagrams, etc. properly
2. Some pages don't work
3. Only works in your browser. What about applications that don't support dark mode?

installation

Note

Only X11 is supported

Clone the repo and build the project:

git clone https://github.com/buxxket/flashguard
cd flashguard
make install

This builds the binary, installs a systemd service to handle starting the program, and creates a basic config file at ~/.config/flashguard/flashguard.config.

customisation

There are a few knobs you can turn to adjust the dimming speed and amount. The config file lives in ~/.config/flashguard/flashguard.config.

If you want to start from the shipped defaults, copy the file from the repo root or let make install create one for you. A complete example config is shown below:

# Flash Guard
#
# All values are optional. Remove a line to fall back to the built-in default.

fps=144 # update frequency in frames per second
min_brightness=0.6 # minimum screen brightness
max_brightness=1.0 # maximum screen brightness
curve_start_avg=0.10 # average luminance where dimming begins
curve_end_avg=0.95 # average luminance where dimming ends
curve_gamma=0.5 # curve steepness
curve_shoulder=0.35 # curve shoulder
avg_input_gamma=1.0 # input gamma applied to sampled brightness
avg_bias=0.0 # bias applied to sampled brightness
brightness_smoothing=0.0 # smoothing factor from 0 to 1
grid_x=40 # horizontal sample grid size
grid_y=24 # vertical sample grid size

The most useful settings are:

• fps for how often the screen is sampled.
• min_brightness and max_brightness for the allowed brightness range.
• curve_start_avg and curve_end_avg for where dimming starts and ends.
• grid_x and grid_y for the sampling grid size.

starting

You can start the Flash Guard with systemd:

systemd --user start flashguard.service

To enable Flash Guard to start automatically when you login to your system, you can enable the systemd service:

systemd --user enable --now flashguard.service

stopping

You can stop Flash Guard with:

systemd --user stop flashguard.service

To disable auto-start, disable the systemd service:

systemd --user disable flashguard.service

logs

Like any systemd service, you can view the logs via journalctl:

journalctl --user -fu flashguard.service