[RFC wayland-protocols] Color management protocol

Carsten Haitzler (The Rasterman) raster at rasterman.com
Sat Jan 14 02:24:14 UTC 2017

On Fri, 13 Jan 2017 18:08:51 +0200 Pekka Paalanen <ppaalanen at gmail.com> said:

> On Fri, 13 Jan 2017 16:37:57 +0100
> Florian Höch <lists+wayland-devel at hoech.org> wrote:
> > Am 13.01.2017 um 16:19 schrieb Richard Hughes:
> > > On 13 January 2017 at 14:56, Florian Höch <lists+wayland-devel at hoech.org>
> > > wrote:  
> > >> .. also guarantee that nothing else will be shown on that specific
> > >> output  
> > > 
> > > FWIW, I'd be fine just displaying a color swatch on the entire screen
> > > with no window decorations; the only reason we use a composited window
> > > in gnome-color-manager is so the user knows where the put the sensor.  
> > 
> > Well, that will work for profiling, as long as you don't mind not being
> > able to see progress information (which I would consider a real drawback).
> > Besides it's surely a bit awkward that the computer then cannot be as
> > easily used differently in the meantime if it doesn't have a second
> > monitor connected (not that I'd recommend it, but I often have a music
> > player open during measurements and sometimes it's nice to have the
> > ability to adjust the playlist while lengthy measurements are still
> > running, to give an example. Also who am I to tell people with their new
> > gigantic 4K 40" desktop monitor that they can't use the rest of the
> > available real estate while a comparatively tiny measurement swatch is
> > displayed in the center?).
> > Also a fullscreen color swatch will probably not be able to deal
> > gracefully with things like OLED screens which might have automatic
> > power limiting depending on displayed content and such, which could
> > botch the measurements in a way that makes the resulting profile useless.
> > 
> > It certainly won't work for guided adjustment (unless you re-implement
> > UI), where the feedback displayed in the UI is supposed to guide the
> > user through adjustments to (e.g.) monitor controls he/she needs to make.
> 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.

------------- Codito, ergo sum - "I code, therefore I am" --------------
The Rasterman (Carsten Haitzler)    raster at rasterman.com

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