[PATCH weston] ivi-shell: add screen_remove_layer API

[Pekka Paalanen]

On Mon, 30 Jan 2017 14:42:42 +0000
"Ucan, Emre (ADITG/SW1)" <eucan at de.adit-jv.com> wrote:

> Hi Pekka,
> 
> You are right. I will send second patch and add the function to end
> of the function list.
> 
> It is stated in ivi-shell/README that ivi_layout interface is stable.
> But I think should not be stable yet. Because we are missing some
> important features (e.g. output hotplugging) or some existing
> feautures are IMO unnecessary (e.g. orientation). Furthermore,
> libweston is changing quite fast. It gets new features in every
> release. If we want to use these new features in ivi-shell, we have
> to add new APIs time to time into ivi_layout interface.

So far libweston also breaks its ABI on every release (major version
bump). That covers also ivi-layout API in my opinion, but has not been
clearly documented I believe. The opinion may have even been different
at the time of writing the README, too - I think it was before
libweston was a thing.

In any case my standpoint is that ABI breaks are major features unless
there is a very good reason to break things closer to a release.

> I want to implement a shared library for ivi-shell (libweston-ivi)
> similar to weston-desktop library, when I have time. Then, it would
> be easier to handle ABI breakages. Because it will be parallely
> installable. Another advantage is that adding an API would be just a
> minor version bump, because it would be backwards compatible.

There are a lot of shared objects involved with ivi-shell already.
Would be nice to see some high level plans and architecture
documentation on how it all fits together and which parts can change
how. I fear there might be too many different interfaces that need to
be maintained.

Would you swallow ivi-layout into libweston-ivi.so?

Will hmi-controller.so be a plugin to weston, ivi-shell or
libweston-ivi.so?

Will the ivi-shell plugin remain with Weston, or move to libweston? Or
will it become libweston-ivi.so?

IVI is different from libweston-desktop: the latter needs considerable
code for handling the client-facing protocols and it implements many
practical details, while leaving the high-level window management to
the user (the desktop-shell plugin). IVI however has very little
client-facing protocol and all of window management is externalized to
controller plugins, so it's hard to see any analogue.

If your idea is to transform ivi-layout into libweston-ivi.so, merge
ivi-shell plugin into it, and change controller plugins to be on the
same level as the desktop-shell Weston plugin is, I think that might be
a good idea. A libweston-based compositor written purely for IVI would
not need a controller as a plugin at all, but just link to and use
libweston-ivi which offers the window management interfaces (ivi-layout
API).

I'm not asking you answer these questions here in this thread, but they
are things I think you would need to consider.


Thanks,
pq

PS. In my mind I have had the idea of turning main.c et al. into a
static convenience library and turning each shell plugin into a
separate executable instead. But, it's a lot of work for questionable
gain, and will have issues with weston-launch.
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