[RFC wayland] protocol: Add wl_surface.buffer_damage

[Bill Spitzak]

On Mon, Nov 9, 2015 at 11:47 PM, Pekka Paalanen <ppaalanen at gmail.com> wrote:

> On Mon, 9 Nov 2015 10:28:13 -0800
> Bill Spitzak <spitzak at gmail.com> wrote:
>
> > I believe wl_surface.damage should be defined as "the same as
> > w_surface.buffer_damage if the only transforms are due to an integer
> buffer
> > scale and the 8 possible buffer transforms". This means it is undefined
> if
> > the wl_scalar proposal is used, and avoids the need to define it for any
> > future transform possibilities.
>
> I have no idea how that could help with anything. It does not matter
> what the mapping is between surface and buffer coordinate systems:
> damage is in surface space, and buffer_damage is in buffer space. There
> is nothing ambiguous about that, even if someone added even more
> transformations between them.
>

A rectangle in a rotated coordinate space, or which has edges or corners
that do not correspond to pixel edges/corners is ambiguous as far as
describing what pixels are damaged. I suppose you could say that it is
enlarged to the bounding box in buffer space but I think it might be better
to just say that you should not use the old api.
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