I wrote a blog post about the recent work in GTK to modernize its CSS engine, and the implications for apps using GTK and libadwaita: https://blogs.gnome.org/alicem/2024/06/07/css-happenings/

- What got added
- What got deprecated
- What changed in libadwaita to make use of the new stuff
- What didn't make it tho I wish it did
- What to expect in future