elementary OS Flatpak Theme Changer

eftc.moon

--- Run this script using a cronjob. I'm running this according to my elementary OS settings:
--- From 06:00 AM (light theme) to 09:00 PM (dark theme) Mexico City Timezone 

exec = (command, ...) ->
  io.popen "#{command} #{table.concat (table.pack ...), ' '}"

FLATHUB_APPS = {}
local COLOR_SCHEME
local THEME

do
  with exec "gsettings get org.freedesktop prefers-color-scheme"
    COLOR_SCHEME = ((\read "*a")\gsub "'(.-)'", "%1")\gsub "%s", ""
    \close!

  with exec "gsettings get org.gnome.desktop.interface gtk-theme"
    THEME = ((\read "*a")\gsub "'(.-)'", "%1")\gsub "%s", ""
    \close!

  with exec "flatpak list --app --columns=application,origin"
    for line in \lines!
      application, origin = line\match "^([%w._-]+)%s*(%w+)%s*$"
      if origin != "appcenter"
        table.insert FLATHUB_APPS, application

    \close!

SYSTEM_THEME = if COLOR_SCHEME == "dark" then "#{THEME}-dark" else THEME

--- Do the actual thing
for app_id in *FLATHUB_APPS
  with exec "flatpak override --user --env=GTK_THEME=#{SYSTEM_THEME} #{app_id}"
    \close!

Thanks to https://gist.github.com/ImranR98/8d6423fdc11022162cf416cc6de0d9af/ for the idea.

Update: No need for this as elementary joined forces with major DEs out there (KDE, GNOME) to make the Freedesktop Color Scheme preference a thing! Firefox 98 will surely support it, as well as most GNOME apps using libadwaita.

https://blogs.gnome.org/alexm/2021/10/04/dark-style-preference/
https://bugzilla.mozilla.org/show_bug.cgi?id=1734934