new xwayland protocol

Andreas Ericsson ae at
Fri Sep 14 01:36:53 PDT 2012

On 09/14/2012 08:40 AM, Pekka Paalanen wrote:
> On Thu, 13 Sep 2012 11:27:50 -0700
> Bill Spitzak <spitzak at> wrote:
>> Tiago Vignatti wrote:
>>> It features ... forwarding global coordinates to X
>> I don't like the idea that X clients are "privileged" to get this
>> information, while real Wayland clients can't get it.
> X is special. X clients expect run under an X server like they always
> have. This means they need some form of global coordinates. These
> coordinates could be faked, too, in case the geometry of the Wayland
> server is not rectangular. In that case, X would probably need a
> (virtual) root window, that solves all global coordinate problems. The
> same for Wine, I guess.
> I rephrase: X clients are not "privileged". They are X clients, not
> Wayland clients.
>> What is going to happen is Wayland clients are going to use the X api
>> just to get this information.
> No, that is impossible. There is no way for a client to associate a
> surface or coordinates from the X API to any objects in the Wayland
> API. Clients in Wayland are isolated, and the xwm and the xwayland
> server are other Wayland clients, hence they are isolated from the app
> in the Wayland protocol. If apps use X API, they fully become X clients.
> If you are worried that any Wayland client would be able to use the
> interfaces reserved for the xwm or xwayland, I'm sure we can deny that
> and produce protocol errors, if anyone attempted it.
>> I can tell you right now that our own
>> software is not going to be usable unless we can save window layouts,
> Saving layouts will be solved differently than in X.
>> and we are interested in portability to Windows and OS/X where the way
>> to place windows on various outputs is to use the coordinates, not an id
>> for the output.
> I don't understand what you mean by portability here. You cannot run an
> X app in Windows without an X server, either.
>> My recommendation is to give up on useless "purity" and make Wayland
>> clients be able to get and set the exact x/y coordinates of their surfaces.
> Apparently you have forgot all about, say, dome projectors or virtual
> displays, where the output is a half sphere. Good luck mapping Cartesian
> global coordinates there in any meaningful way.
> I'm not making virtual displays up, btw. I have been explaining Wayland
> to someone who is researching just that.

While it's a good idea to be able to support minority use cases like that,
I don't think it's a very good idea to do it in a way that makes wayland
less useful for a far greater audience. Most of us have plain rectangular
screens, and I pretty much like having my applications open up where they
were last, or at the place where I tell them to. Ideally windows would
move further up and to the left if the desired window size is greater than
the area where we're supposed to draw it. That would make things behave
properly when moving from an external screen to the internal one on a

Andreas Ericsson          at
OP5 AB                   
Tel: +46 8-230225                  Fax: +46 8-230231

Considering the successes of the wars on alcohol, poverty, drugs and
terror, I think we should give some serious thought to declaring war
on peace.

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