Well, I'm happy to release the first stable version of niri, my scrollable-tiling compositor: https://github.com/YaLTeR/niri/releases/tag/v0.1.0
Very satisfied with the current state, even though there's plenty left to do. Took a lot of time and work but I've certainly learned a lot, and I'm glad to have contributed a bit to Smithay too!
Before adding more animations into niri, I'm making a "visual tests" application. It shows a set of hardcoded scenarios which I can quickly go through and visually check that everything looks right.
It uses solid color rectangles as "windows", but otherwise this is the real niri layout code and real niri + Smithay rendering code, drawing to a GTK GL area.
For example, on the last test you can see that my offscreen code currently clips CSD shadows (during the open animation).