Well, as you know I've been poking around in the theme engine. I tried generating a UML diagram in VS Code from Theme.ts, it, well, didn't do anything, so I was thinking of starting by making it so that it does.
My broader goal is to abstract the theming engine to make it easier and safer to develop new themes, and eventually to make it possible to update the theme colors on the fly in response to system events.
(Something I was thinking might be a safe eventual approach is ripping off the GtkStyleContext API so as not to reinvent the wheel, especially since GTK Styles are just CSS.)
How does that sound for scope? If the changes I make don't break existing functionality while accomplishing the above goals (and improving documentation) is that something you might be interested in integrating at some point down the line?