[PATCH wayland] protocol: Add deprecation note about wl_shell

[Nils Chr. Brause]

Hi!

On 4 December 2017 at 09:16, Pekka Paalanen <ppaalanen at gmail.com> wrote:
> On Sat,  2 Dec 2017 10:57:45 +0800
> Jonas Ådahl <jadahl at gmail.com> wrote:
>
>> Now that xdg_shell is stable and much better defined than wl_shell we
>> can finally deprecate wl_shell and guide users towards xdg_shell
>> instead.
>>
>> Signed-off-by: Jonas Ådahl <jadahl at gmail.com>
>> ---
>
> Hi,
>
> Acked-by: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
>
>>
>> Eventually we can consider adding deprecation attributes the
>> <interface> XML nodes that'll turn into compiler warnings, but this is
>> at least a start moving away from wl_shell. I imagine the wl_shell users
>> today (SDL, GLFW at least) to hopefully migrate soon, but keep the
>> wl_shell as a fallback for the time being while compositors add support
>> for xdg_shell. So we probably don't want to add compiler warnings for
>> them just yet.

I really like the idea of a deprecation attribute. The C++ bindings
would use it to add the [[deprecated("reason")]] attribute specifier
sequences to interface classes, event callbacks and request methods.
The value of the XML attribute could be what to use instead, e.g:

<interface name="wl_shell" version="1" deprecated="xdg_wm_base">

This value could be used in the C++ bindings as the "reason" argument.

>
> I would imagine compositors wanting to keep the support for a long
> time, so maybe the warnings would be just in the client header?

Yes, of course, this would be client only.

>
> OTOH, ISTR problems with having deprecation warnings in
> system-installed headers, compilers ignoring them...

I don't know about gcc, but g++ certainly doesn't ignore the
[[deprecated]] attribute on headers in /usr/include. I just tested
this with g++ 7.2.

>
>
> Thanks,
> pq

Cheers,
Nils

>
>
>>  protocol/wayland.xml | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/protocol/wayland.xml b/protocol/wayland.xml
>> index aabc7ae..77d991e 100644
>> --- a/protocol/wayland.xml
>> +++ b/protocol/wayland.xml
>> @@ -976,6 +976,9 @@
>>
>>        It allows clients to associate a wl_shell_surface with
>>        a basic surface.
>> +
>> +      Note! This protocol is deprecated and not intended for production use.
>> +      For desktop-style user interfaces, use xdg_shell.
>>      </description>
>>
>>      <enum name="error">
>
>
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