Damask: First-run configuration hook and non-destructive activation #1161

Summary

Configure non-destructive defaults for Damask without overwriting personal wallpapers or colliding with GNOME's built-in timed day/night wallpaper cycle.

Technical Context

• Flatpak apps run against GKeyfileSettingsBackend with config located at ~/.var/app/app.drey.Damask/config/glib-2.0/settings/keyfile.
• Damask's GSettings schema separates root application preferences (app.drey.Damask) from source plugins (app.drey.Damask.sources.slideshow). Keys like folder-uri belong strictly to [app/drey/Damask/sources/slideshow].
• Damask enumerates folders non-recursively. Wallpaper images live in /usr/share/backgrounds/bluefin/ (not the root /usr/share/backgrounds/).
• Because Bluefin ships timed day/night XML slideshows natively, setting active-source='slideshow' by default would overwrite org.gnome.desktop.background picture-uri with static images and bypass day/night crossfades. Leaving active-source='none' pre-seeds the desired interval and settings while letting the user activate the rotator deliberately.

Implementation Steps

1. Add user setup hook system_files/bluefin/usr/share/ublue-os/user-setup.hooks.d/25-damask-setup.sh:
   • Source /usr/lib/ublue/setup-services/libsetup.sh and call version-script damask-setup user 1 || exit 0.
   • Ensure directory ~/.var/app/app.drey.Damask/config/glib-2.0/settings exists.
   • Write pre-seeded keyfile:

     [app/drey/Damask]
     refresh-interval='86400'
     enable-automatic-refresh=true
     run-in-background=true
     active-source='none'
     
     [app/drey/Damask/sources/slideshow]
     folder-uri='file:///usr/share/backgrounds/bluefin'
     sort-by='random'

   • Enable user unit systemctl --user enable damask.service (which is safely guarded by ConditionPathExists=| so it only activates when Damask is installed).

Testing & Verification

• Bats unit test executing hook in isolated environment and verifying generated keyfile structure and permissions.
• Verify idempotency on repeat runs via version-script.