A solution for gamma-adjustment support in Wayland

[Kai-Uwe]

Hello Mattias,

Am 21.12.2016 um 12:31 schrieb Mattias Andrée:
> If there is no API for these thinks, functionality
> such as inverting the colours, lowering the temperature,
> and (requires matrices) simulating defective colour
> vision must be done in the compositor. This is not
> a sustainable solution, an API is necessary. It's bad
> enough that colour management is done by the compositor.

The compositor is a good place for doing color correction, as X11 and
Wayland core developers had repeatedly suggested. I mentioned to you on
the XDG list, that your API will be bypassed by any proper ICC based CMS
and both might start fighting about resources/settings. That's no good I
think. A ICC monitor profile has to set a calibration curve into the
display pipeline. It does currently on X11 systems and Weston has some
code to do as well CLUT setup. Without knowing each other that's a bug
filler, which no one want (at least I hope).

For getting more specialised support into the compositor, the suggested
surface device links for each output are very expressive [as discussed
by Niels+Graeme+me in the color management thread]. A CMS can work with
device links and add features without involving the application. So it
can add device links on its discretion to surfaces, which do not have
them already and support new features like the redshift curves or more
advanced effects. That would be a big benefit for both communities I
guess. For that to work seamless your curves, need to be abstracted and
instead of curves are expressed as ICC profiles of type abstract. So a
CMS can integrate them easily, without to know the bells and whistles
redshift offers its users.

Kai-Uwe