[RFC wayland-protocols] Add alpha-compositing protocol

[Daniel Stone]

Hi Alexandros,

On Tue, 8 Aug 2017 at 15:25, Alexandros Frantzis
<alexandros.frantzis at collabora.com> wrote:
> This protocol specifies a set of interfaces used to control the alpha
> compositing and blending of surface contents.
>
> It's based on the Chromium Wayland protocol of the same name ([1]),
> with a few changes made to the blending_equation enumeration.
>
> [...]
>
> +  <interface name="zwp_blending_v1" version="1">
> +    <description summary="blending interface to a wl_surface">
> +      An additional interface to a wl_surface object, which allows the
> +      client to specify the blending equation used for compositing and
> +      an alpha value applied to the whole surface.
> +
> +      When the blending object is created its blending equation is
> +      'none' and its alpha is 1.0, i.e., it's inactive by default. Clients
> +      can activate it by setting the blending equation and alpha value.

This doesn't specify any interaction with per-pixel alpha values. Is
it an additional step after per-pixel alpha, or does it replace
per-pixel alpha?

Beyond that, looks good to me.

Cheers,
Daniel