Enums, bitfields and wl_arrays

[Erik De Rijcke]

Adding enum members is backward compatible for Java. If you compile against
an enum with 2 members, and later on a new member is added, you can simply
use the new version of the enum.

Important however is that the order of old members do not change when new
members are added.

On Thu, Oct 8, 2015 at 10:27 PM, Daniel Stone <daniel at fooishbar.org> wrote:

> Hi,
>
> On 8 October 2015 at 21:13, Daniel Stone <daniel at fooishbar.org> wrote:
> > On 5 October 2015 at 21:31, Victor Berger <victor.berger at m4x.org> wrote:
> >> In this case, for a "closed" enum, the binding can decide to ignore any
> >> value received on the wire that is not described in the XML, as anyway,
> the
> >> client would not know what to do with it (and if they knew, they should
> be
> >> using a more recent version of the binding).
> >
> > This should never happen. The compositor is responsible for tracking
> > which version the client has bound, and not sending it values it
> > doesn't know what to do with.
> >
> > I've heard mention that xdg-shell allows this, but I also can't see it
> > anywhere in the spec. Jasper?
>
> Whoops ...
>
> 9:18 PM <Jasper> daniels, sorry, what were we talking about with enums?
> 9:20 PM <daniels> Jasper: people are concerned that xdg-shell has
> 'open' enums, in that a compositor can send a configure event with
> enum values unknown to the client
> 9:20 PM <Jasper> daniels, that's correct
> 9:20 PM <daniels> Jasper: bollocks, really?
> 9:20 PM <Jasper> daniels,
> http://cgit.freedesktop.org/wayland/weston/tree/protocol/xdg-shell.xml#n321
> 9:23 PM <daniels> Jasper: ah, i see - that does make quite a bit of sense
> 9:23 PM <daniels> Jasper: but i do wonder if we should bound that by
> what the client actually supports, e.g. don't send gnome-specific
> values unless the client has bound gtk_shell
> 9:23 PM <Jasper> daniels, the state mechanism is designed to solve a
> very specific race condition, so we don't want people inventing their
> own protocols to do the same.
> 9:24 PM <daniels> Jasper: oh, indeed
> 9:24 PM <Jasper> daniels, I would be fine with that, but I'm not sure
> it helps Rust clients.
> 9:24 PM <daniels> Jasper: indeed, more of a general musing
> 9:24 PM <daniels> Jasper: thanks for pointing that out; not sure how i
> missed it
>
> How does that play with Java/Haskell/etc? Would that just degenerate
> into a plain undecorated uint, or ... ?
>
> Cheers,
> Daniel
>
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