[PATCH wayland-protocols v7] Add zwp_linux_explicit_synchronization_v1

[Pekka Paalanen]

On Mon, 3 Feb 2020 23:26:55 -0600
Jason Ekstrand <jason at jlekstrand.net> wrote:

> Sorry to drag up ancient threads, but what's the status of this?  I see
> rumors that it's in Weston.  Is it stable?  Is it implemented anywhere
> else?  It'd be great, for the sake of Vulkan, if we could get this stable
> and everywhere.
> 
> --Jason
> 
> On Mon, Dec 17, 2018 at 11:25 AM Tomek Bury <tomek.bury at gmail.com> wrote:
> 
> > Thanks! That looks better than my patch.
> >
> > On Mon, 17 Dec 2018 at 15:37, Alexandros Frantzis <  
> > alexandros.frantzis at collabora.com> wrote:  

> >> [1] https://gitlab.freedesktop.org/wayland/weston/merge_requests/32

Hi,

the above MR is merged, the code is in Weston and is supposed to work.
I have a vague recollection that the implementation might not be
"totally optimal" in all cases, meaning that it may choose to deliver
`immediate_release` rather than `fenced_release` even if the latter was
theoretically possible.

I don't know about other compositors, we don't have the extension
information site up yet.

The protocol itself is in unstable:
https://gitlab.freedesktop.org/wayland/wayland-protocols/tree/master/unstable/linux-explicit-synchronization

This does not mean that we can break it at will. The committed protocol
is stable in the sense that we cannot break it anymoe, but unstable in
the sense that zwp_linux_explicit_synchronization_v1 is not the final
name.

IOW, it is safe to look for Wayland extension
zwp_linux_explicit_synchronization_v1 and use it. If we need changes
that cannot be made backward-compatible, a new extension with name
zwp_linux_explicit_synchronization_v2 will be created. Once we are sure
we do not need backward-incompatible changes anymore, the extension
will be renamed to wp_linux_explicit_synchronization which will be the
final change that all servers and clients should very much implement.

Both compositors and clients are encouraged to implement all major
versions of the extension if possible for maximum compatibility.

TL;DR:

If you find a Wayland compositor advertising
zwp_linux_explicit_synchronization_v1 via wl_registry, feel free to use
it and expect it to not break from under you.


Thanks,
pq
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