Reduce compositor-to-backend lookup
There are a few places where backends look up the backend pointer from the compositor via to_xyz_backend()
helpers when creating heads or outputs. With the compositor->backend
pointer this is trivial now, but with multi-backend support this pointer would go away and it would be required to iterate over all backends to find the correct one.
Reduce to_xyz_backend()
usage or pass a weston_backend
pointer and simplify the helpers into container_of()
wrappers, for the windowed output API.
This might be an alternative to the suggestion in !578 (comment 1866445).
/cc @mol