Dark mode for terminal users

I firmly believe that you should use light mode when the ambient lighting is bright. As far as I know, science agrees with that, since dark text on a white background is easier to read than the opposite.

But after the sun has set and you’ve dimmed all the lights, staring at a bright screen seems wrong and it looks out of place when the rest of your system switches to dark mode.

For the longest time I’ve therefore wanted to have the automatic dark/light mode switching in my terminal environment, which consists of Alacritty, tmux, Fish and Neovim (tmux doesn’t define any color values of its own, so we can ignore it).

I finally got around to spending some time on this not so tricky problem and I’d say I’m 85% there. I use my own color theme which exports config files for, among other things, all three programs listed above. And all config files are available in a dark and a light mode. Meaning, in Neovim I can simply switch to the dark version with :color yui_dark. Since Neovim has a nice client/server architecture I can also do this remotely:

:let g:lightline.colorscheme = "yui_dark" | colorscheme yui_dark | call lightline#init() | call lightline#colorscheme() | call lightline#update()<CR>

Alacritty also has a nice API for changing config values from the shell. You can read more about it under man alacritty-msg (and man 5 alacritty for the config values) but the gist is alacritty msg config -w -1 'colors.cursor.background="#CCCCCC"'.

Lastly, for configuring the Fish shell syntax colors you use shell commands anyway, so the exported “config” is a Fish file that I can call whenever I want. The file has commands like this:

set fish_color_match eae9e9
set fish_color_selection --background=474355
set fish_color_search_match --background=4f4b5f
...

In other words: I now have shell commands for remotely changing Alacritty, Fish and Neovim from light to dark mode and vice versa. The “only” thing left to do is to find a way of running either of the two variants when the system switches themes.