Merged the "window positions and sizes in IPC" PR. Please test and report if anything's broken or missing, we have time to fix it until the next release.
https://yalter.github.io/niri/niri_ipc/struct.Window.html#structfield.layout
Here's a quick quickshell test I threw together that draws floating windows as rectangles.
Thanks yrkv for getting the PR mostly complete!
Overlay panel showing floating windows in white rectangles at correct positions and sizes.