Gamma correct rendering with Wayland and Weston

Pekka Paalanen ppaalanen at
Mon Oct 1 00:25:51 PDT 2012

On Sun, 30 Sep 2012 08:45:55 -0700
Bill Spitzak <spitzak at> wrote:

> On 09/29/2012 01:28 AM, John Kåre Alsaker wrote:
> >> Wayland also does scaling and rotations but the difference between linear
> >> and srgb is much smaller for these. I think the real solution for this is to
> >> allow clients to know the actual transform of their surfaces to the screen
> >> and be allowed to draw the transformed image, since this will avoid
> >> resampling and filtering, as well as letting the clients choose the color
> >> space.
> > Part of the point of Wayland is that clients shouldn't know about how
> > they are placed or transformed, even if they did, the compositor would
> > still have to compose them and know about the gamma encoding they use.
> Clients certainly should not *have* to know about the transformation, 
> and the shell will transform for them.
> However, even thought there is a deliberate attempt to make clients not 
> know it in current Wayland, I think client awareness of the transform is 
> going to be needed eventually. Lots of clients could draw their 
> transformed windows enormously faster and higher quality than then if 
> they drew the non-transformed one and the shell then transformed the image.

And you would like to kill all innovative uses like:
right? And spherical VR displays, too?

No, this is not yet the reason to expose transformations to clients.
You are only suggesting to make the protocol a huge deal more complex
and restrictive, to optimize a tiny detail prematurely, again. On a
regular desktop, the transformed case is very rare, and even more rare
on cases where the image quality would actually matter that much.

- pq

More information about the wayland-devel mailing list