Can I ask why you did it in ruby? I like ruby, don't get me wrong, but that seems pretty low on the list of languages an X12 would be written in.

I think an X12 would be X11 with a cleaned up codebase, removed features, and additions of modern features that Wayland or Quartz have without compromising compatibility more than necessary

Because I like Ruby and it's compact, and most of my stack, including my terminal, wm, font renderer and X11 bindings are already in Ruby (the latter two are reused directly).

Also because I was curious if it'd be viable, and turns out its fast enough (for a low level backend I might end up pulling in Mesa and some optimized blitting code, but otherwise pure Ruby is all you need)

To me an X12 implies significant protocol changes, or it's just another X11 implementation - X11 is the protocol, not a specific implementation.

And it turns out significant protocol changes might just not be particularly worthwhile given you can run most X11 clients with a few thousand lines (including XRender, Xinerama, and other key extensions)

Instead you certainly can make savings by ditching old hardware, and not bothering to make legacy drawing modes fast. I'm not going to commit to full compatibility, so maybe the x12 label might still make sense, but gtk + qt compatibility + about a dozen simple extra drawing calls gives you most X11 clients.