Looks okay, with the comments above about shm_open and to my very limited knowledge of Wayland. Also, some additional comment about the commit split, though at this point it's probably not much a big deal:
Both https://gitlab.winehq.org/wine/wine/-/merge_requests/2944/diffs?commit_id=8d... and https://gitlab.winehq.org/wine/wine/-/merge_requests/2944/diffs?commit_id=ca... fix a broken corner case that has been introduced by the commit before them. In general I think it's better to avoid introducing broken intermediate state.