[RFC wayland-protocols] Color management protocol

[Carsten Haitzler (The Rasterman)]

On Sat, 14 Jan 2017 11:52:25 +0100 Kai-Uwe <ku.b-list at gmx.de> said:

> Am 14.01.2017 um 03:24 schrieb Carsten Haitzler (The Rasterman):
> > On Fri, 13 Jan 2017 18:08:51 +0200 Pekka Paalanen <ppaalanen at gmail.com>
> > said:
> >> Oh, ok, that's why. We could as easily have the compositor show the
> >> color swatch only on a part of the output and leave the rest of the
> >> area for normal use.
> >>
> >> However, if that is done with a special protocol so that the compositor
> >> actually knows this is the profiling color swatch, it can make sure
> >> other windows cannot interfere. It could be like the color swatch was
> >> on an always-on-top overlay. You cannot do that any other way from a
> >> Wayland client.
> >>
> >> And if unform color for the swatch is all you need, the protocol could
> >> simply take 3 numbers for the color instead of an image buffer. Then
> >> people would not get the urge to abuse this interface for e.g.
> >> application splash screens.
> > 
> > i kind of like the idea of a special protocol with 32bit ints per rgb etc.
> > to say "display this exact uncalibrated color as-is without luts or
> > anything else in the way"... but apply it to a separate toplevel
> > window/surface (and put your guided ui controls in another window) or...
> > use a subsurface.
> 
> +1 for subsurface. The compositor can even take over responsibility to
> move the belonging window to the desired output, for the case the
> underlying application can not manage or handle that itself (e.g. for
> mirrored outputs).

indeed as it knows the parent surface etc. and thus can "do the right thing"
without the calibration app needing to know or care at all.

in the end a calibrator really just needs to present some data (unmolested by
gamma luts/color correction/blending etc.) onto a display so some colorimiter
device dangling on the screen can read it and feed back what it sees. using
this dat produce a set of calibration data a compositor (or an app) canuse
later that would be applicable to that monitor.

-- 
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The Rasterman (Carsten Haitzler)    raster at rasterman.com