This is based on the API that will be used for no-copy presentation. But
wraps it in `set_buffer`.
This also fixes the Wayland buffer code to set `self.width` and
`self.height` on resize, and set the length of the shared memory file
when the buffer is created.
Co-authored-by: jtnunley <jtnunley01@gmail.com>
This adds a fallback using `shm_open`/`shm_unlink` for platforms where
`memfd_create` doesn't exist. This seems to be how this is normally
handled, though it's a bit ugly.
This also builds the wayland/x11 code for NetBSD/OpenBSD/DragonFlyBSD.
Add CI builds for FreeBSD and NetBSD. We would need some kind of
virtualisation though to actually run tests on such targets.
I've tested the `shm_open` logic on Linux, but haven't run it on any
BSDs.
