[RFC PATCH wayland-protocols] Introduce logical output protocol for Xwayland

Pekka Paalanen ppaalanen at gmail.com
Fri Jun 30 09:04:51 UTC 2017

On Fri, 30 Jun 2017 04:38:07 -0400 (EDT)
Olivier Fourdan <ofourdan at redhat.com> wrote:

> Hi Jonas,
> > On Thu, Jun 29, 2017 at 04:44:34PM +0200, Olivier Fourdan wrote:  
> > > This introduces a new protocol for the compositor to describe outputs
> > > size in a logical way for Xwayland.

> > Adding it to wl_output might be fine anyway, as we could refer to it
> > when talking about how clients should not rely on calculating its own
> > "output size" by looking at wl_output::mode, wl_output::transform and
> > wl_output::scale, but we could just as well clarify that they simply
> > shouldn't.  
> Yes, on further consideration and as we discussed earlier today on
> irc, this might be of interest to some other clients as well, so
> adding it to the existing wl_output interface makes sense imho,
> rather than adding an Xwayland specific interface...


please consider that it is impossible to have a stabilization period
for changes to the wl_output interface. What ever you add will be set
in stone immediately, before a considerable user base has had a chance
to try it. There will be no going back once it's there, AFAICT no way
to have it reasonably tested on the field beforehand.

In hindsight I think the position x,y arguments we already have in
wl_output do not belong there. Only traditional 2D desktops can
meaningfully set them. They already break down completely in IVI
systems, where the outputs may be independent in the sense that there
is no path in the logical coordinate system that you could take to
travel from one output to another in a way that would make sense. Not
all systems have a single connected area created from outputs, that
design is quite specific to desktops.

I would like us to be careful with not adding more desktop assumptions
to core Wayland interfaces. Whether this proposal would add some, I
cannot tell yet.

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