[PATCH wayland-protocols v7] Add zwp_linux_explicit_synchronization_v1

[Scott Anderson]

On 4/02/20 10:16 pm, Pekka Paalanen wrote:
> 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

Just as a follow up, I plan to add support in wlroots. I want to go with 
a much more elaborate implementation than Weston's one, which changes 
some of our fundamental assumptions about surface state, and requires a 
lot of changes, which is why it has been slow to get implemented.

I have a description about it here [1] that other compositors might be 
interested in.

Scott

[1]: https://github.com/swaywm/wlroots/issues/894#issuecomment-465096345