Collaboration on standard Wayland protocol extensions

Pekka Paalanen ppaalanen at
Tue Mar 29 09:17:46 UTC 2016

On Tue, 29 Mar 2016 08:25:19 +0300
Giulio Camuffo <giuliocamuffo at> wrote:

> 2016-03-29 6:23 GMT+03:00 Drew DeVault <sir at>:
> > On 2016-03-29  2:15 AM, Martin Peres wrote:  
> >> I was proposing for applications to just bind the interface and see if it
> >> works or not. But Giulio's proposal makes sense because it could be used to
> >> both grant and revoke rights on the fly.  
> >
> > I think both solutions have similar merit and I don't feel strongly
> > about either one.  
> If the client just binds the interface the compositor needs to
> immediately create the resource and send the protocol error, if the
> client is not authorized. It doesn't have the time to ask the user for
> input on the matter, while my proposal gives the compositor that.

More precisely, you cannot gracefully fail to use an interface exposed
via wl_registry. It either works, or the client gets disconnected.
Protocol error always means disconnection, and wl_registry has no other
choice to communicate a "no, you can't use this".

Checking "whether an interface works or not" is also not trivial. It
would likely lead to adding a "yes, this works" event to all such
interfaces, since anything less explicit is harder than necessary. But
why do that separately in every interface rather than in a common

Btw. I did say in the past that I didn't quite understand or like
Giulio's proposal, but I have come around since. For the above reasons,
it does make sense on a high level.

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