[PATCH wayland] Add "enum" attribute to "arg" elements

[Jeroen Bollen]

About the 2 ways of adding an enum:

The user can always specify an error handler to handle unknown values. The
error handle can then handle the error value, or unknown value.

On Mon, 27 Apr 2015 09:05 Pekka Paalanen <ppaalanen at gmail.com> wrote:

> On Sat, 25 Apr 2015 14:11:32 +0000
> Jeroen Bollen <jbinero at gmail.com> wrote:
>
> > > I think that totally depends on how the interface is specified. This
> > > applies only to one of the two ways an <enum> can grow.
> >
> > What other way can it grow? It can only grow bigger. If the application
> > isn't aware of new values added, it should output a warning or an error.
>
> These:
>
> On Wed, 22 Apr 2015 09:34:51 +0300
> Pekka Paalanen <ppaalanen at gmail.com> wrote:
>
> > There are two ways to add values to an existing <enum>:
> >
> > - Bumping the interface version, and ensuring the new values are used
> >   only with the appropriate runtime interface version.
> >
> > - From the first definition of an interface, specify how unknown values
> >   should be handled. Otherwise users do not expect unknown values to
> >   appear.
>
> The latter case is where you do not want an automatic always-on warning
> or error.
>
>
> > On Fri, 24 Apr 2015 22:05 Bill Spitzak <spitzak at gmail.com> wrote:
> >
> > > Since all the codegen packages that want to use this enum attribute
> have
> > > not been written yet I don't think back-compatibility is an issue. They
> > > are not using uint because they do not exist yet!
>
> Except if you happen to have an old libwayland which you develop your
> 3rd party app against, for instance because you use a distribution that
> does not include a more recent version yet.
>
> Depending on the language, I suppose the breakage could go both ways?
> Is there a language where an enum is not allowed to be implicitly
> converted to a uint or int?
>
>
> Thanks,
> pq
>
> > > The C codegen can continue to ignore the enum, or use it in a way that
> > > does not break code that tries to pass an integer or the wrong enum.
> > >
> > > On 04/24/2015 12:07 AM, Pekka Paalanen wrote:
> > >
> > > > The purpose of docenum was purely for documentation. An API generator
> > > > must ignore all docenum annotations. This was the backward-compatible
> > > > addition.
> > > >
> > > > Any attribute that modifies the generated API in incompatible ways
> > > > cannot be added after the interface has been released as stable. If
> > > > your function argument was uint, and you change it to an enum in a
> > > > strictly typed language, does it not have a good chance of breaking
> > > > someone's build?
> > >
>
>
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