Effort for upgrading from 1.3 to 1.5

[Jason Ekstrand]

On Mar 20, 2014 9:59 AM, "Pekka Paalanen" <ppaalanen at gmail.com> wrote:
>
> On Thu, 20 Mar 2014 13:31:31 +0000
> "Konopelko, Pavel (P.)" <pkonopel at visteon.com> wrote:
>
> > Hello everybody,
> >
> > Question:
> > Given that somebody has Wayland/Weston 1.3 already integrated in
> > their system, what would it take to upgrade to the upcoming
> > Wayland/Weston 1.5?  Is this just a matter of re-building it and
> > everything will continue working out of the box?  Are there any
> > adjustments in the graphics stack (drivers, EGL support, etc.) needed
> > to support 1.5?  Are there any adjustments on the application side
> > needed to work with 1.5?
>
> Hi,
>
> oh, 1.3 seems like ages ago, I can't remember. But, looking at the git
> history of few selected files should be enlightening, for instance in
> Wayland src/wayland-client.h and src/wayland-server.h, and also the
> protocol specification in protocol/wayland.xml. In Weston
> src/compositor.h.
>
> For clients, things are kept backward-compatible. For Weston plugins,
> change from 1.n to 1.n+1 is not guaranteed to be compatible.
>
> Libwayland API is stable and backward-compatible. The Wayland protocol
> is also kept stable, but we are moving from wl_shell to xdg_shell,
> though that probably does not concern you.
>
> On EGL front, you probably should be looking at the history of the
> specification files in Mesa, e.g.:
>
http://cgit.freedesktop.org/mesa/mesa/log/docs/specs/WL_bind_wayland_display.spec
> to get an overview.
>
> I think application side should just work, all in all.

As Pekka said, from the libwayland and client-side everything *should* be
stable.  We've put a lot of work into keeping things API and ABI-stable as
we've changed them.  EGL implementations should be following the EGL API's
that haven't changed.

On the weston side, things are not so stable.  In particular, the
weston_view structure was added in 1.4 and this changed the weston
scenegraph somewhat substantially.  In particulare, the concepts of "node
in the scenegraph" and "client surface" were split apart so that the same
surface can appear at multiple locations at once.  If you are writing your
own shell plugin this change may be small or large depending on how the
plugin is written.  My guess, given the little I understand about IVI is
that it shouldn't be too hard, but it won't be trivial.

>
> > Background:
> > The question is related to the weston-ivi-shell patch series
> > submitted by Nobuhiko Tanibata.  This work is connected to the work
> > that GENIVI [1] previously did in the area of IVI Layer Management.
> > On the GENIVI side, the original plan was to propose the ivi-shell
> > and the corresponding protocol to the Wayland project.  However, it
> > was expected that it will take time to review and agree the
> > protocols.  Until then the plan provided for adopting an out-of-tree
> > patch based on Wayland/Weston 1.3 for GENIVI purposes.  Once the
> > ivi-shell would be integrated in Wayland/Weston, GENIVI would switch
> > to the upstream version.
> >
> > Now that the patch series was well accepted and that only a few
> > changes were suggested to the original protocol, it would make more
> > sense for GENIVI to align with the upstream right away.  The only
> > catch is that the content of the next GENIVI release is being
> > finalized right now and the decision must be done quickly.  During
> > the original reviews in GENIVI, using Wayland/Weston 1.3 as the basis
> > was already approved.  The above question is an attempt to estimate
> > the impact of adopting 1.5 instead.  Any hints and information on
> > possible upgrade problems would be therefore greatly appreciated.
>
> Sorry, I think "well accepted" may still be a slight overstatement at
> the moment. It's just so hard to find time to review anything. When you
> get a "looks good to me" then that's accepted by that particular
> person, but even that is not enough to get into Wayland/Weston
> upstream. For that you need to convince Kristian, who seems to be
> extremely busy nowadays.

Agreed.  Personally, I like the direction the protocol has taken.
Unfortunately, I haven't had time to review any of the code or the library
api.  As Pekka said, to a certain extent, we're waiting on Kristian to be
able to take a look at it and give an opinion on how it ought to fit into
the Wayland ecosystem.  However, he's been pretty busy with the X.org and
GNOME merge windows coming up so I wouldn't expect a lot for a little bit
yet.

Hope that helps,
--Jason Ekstrand
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