Finally finished making niri screencasts asynchronously wait for rendering completion before handing the buffer over to PipeWire. This fixes screencast flickering problems on NVIDIA setups.
https://github.com/YaLTeR/niri/pull/2175
This is not PW explicit sync; I can now finish that too (OBS and PW released their fixes), but it'll act more as an optimization on top of the current code (since only OBS can use it for now, and not on its Flathub build (PW is too old there)).