HDR support in Wayland/Weston

Chris Murphy lists at colorremedies.com
Wed Feb 27 20:47:07 UTC 2019

On Wed, Feb 27, 2019 at 5:27 AM Pekka Paalanen <ppaalanen at gmail.com> wrote:
> there is a single, unambiguous answer on Wayland: the compositor owns
> the pipeline. Therefore we won't have the kind of problems you describe
> above.
> These are the very reasons I am against adding any kind of protocol
> extension that would allow a client to directly touch the pipeline or
> to bypass the compositor.

Well you need a client to do display calibration which necessarily
means altering the video LUT (to linear) in order to do the
measurements from which a correction curve is computed, and then that
client needs to install that curve into the video LUT. Now, colord
clearly has such capability, as it's applying vcgt tags in ICC
profiles now. If colord can do it, then what prevents other clients
from doing it?

> If we had to support such old games that insist on playing with the
> video LUT (assuming that there is just one LUT, no CTM, etc.), we could
> have a Wayland extension that allows attaching the LUT to a wl_surface,
> and then the compositor would apply the LUT any way it wants but only
> to that one window while at the same time all the other windows would
> remain looking good regardless.


Chris Murphy

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