Several days and a lot of hair pulling later, I *think* I got resize transactions working?? Maybe? Hopefully?
Resize transactions is when all windows that must resize together, resize together, with no mismatching frames in between. For example, all windows in a column must add up to the full screen height.
This requires correct configure acks on the client (looking at you, Blender) and very careful state update delaying and resize throttling on the compositor side.
narrator: there was still one case where it didn't work due to a bug
okay, surely this time it definitely works for all correctly written clients