HDR support in Wayland/Weston

[Chris Murphy]

On Thu, Mar 7, 2019 at 2:35 PM Graeme Gill <graeme2 at argyllcms.com> wrote:
>
> Michel Dänzer wrote:
>
> > It sounds like KMS leases could be a pretty good fit for a calibration
> > application. It can lease each output individually from the Wayland
> > compositor and fully control it using KMS APIs, while the Wayland
> > compositor continues running normally on other outputs.
>
> There seems to be this idea that has got a hold amongst many commentators
> on this topic here, that somehow the display calibration and profiling
> application NEEDs raw and direct access to the a display to operate.

Just to underscore how mistaken such an assumption would be, the
self-calibrating displays on the market produce a display state of
behavior (white point, black point, primaries, and tone reproduction
curve), and an ICC profile that describes that state, without any
respect whatsoever to behaviors in the OS or the connection between
display and computer. That ICC profile correctly describes that
display whether the OS is macOS or Windows.

If everything is correctly done, that would also be true for Linux
whether GNOME, KDE, Xorg, or any Wayland compositor. The profile
doesn't describe how wrong a display is, it doesn't describe a
correction. It merely maps RGB values, submitted by an ordinary
application for display, to their color appearance (all kinds of
media, environment, observer assumptions are baked into that term).

The small problem we might have for the rest of the displays that
aren't self-calibrating, is lack of platform support parity for the
various video card LUTs. But for that (important) detail, it should
otherwise be true that an ICC profile describes the display's state
regardless of the display rendering pipeline (ergo, regardless of
platform).



-- 
Chris Murphy