[RFC wayland-protocols] Color management protocol

Pekka Paalanen ppaalanen at gmail.com
Fri Jan 13 16:08:51 UTC 2017

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.

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