[Openicc] XICC specification draft

[David Burren]

On 26/06/2005, at 7:19 AM, Chris Murphy wrote:
>
> Who has written the x11 client for OS X? Apple? If so, it would  
> make sense as a feature request for their x11 client to become  
> aware of the currently selected ICC profile and provide that  
> information back to the x11 server. I'm not sure to what degree  
> this does already occur but I suspect it doesn't. Easy to test  
> thought, with a whacked out RGB display profile with the primaries  
> reversed.
>

As has been pointed out, it sounds like you've got client/server  
concepts reversed for X11.
The X11 server is the software provided (e.g. Xquartz by Apple) that  
does the actual drawing on the screen.
X11 clients are the various pieces of application software that  
connect to the server and send it information to draw, and retrieve  
information such as mouse/keyboard data.

Having the Apple X11 server automatically set the new XICC atom based  
on the current display profile would indeed be a "nice" solution.
However, several issues come up:

In general, "who/what" is expected to set the atom, set display LUTs,  
etc?  In this case OSX will have set the LUT calibration and it makes  
sense for the Xquartz server to also set the atom.  But be careful  
not to establish a requirement that the server does it: in a pure X11  
system it's probably best for a client to do this and handle the  
relevant policy decisions.

Which profile should be used in multi-head configs?  In a traditional  
multi-head X11 system, each screen can be accessed via a different  
$DISPLAY (e.g. machine:0.[screen-number]).  But with this system  
there's no facility to move windows between screens or have them  
spanning screens.  So systems like Xcinerama establish a single  
virtual screen covering the entire multi-head area.  And this is what  
can happen with Apple's Xquartz.  It just presents a simple single- 
screen desktop to the X11 clients.  But that also means only one XICC  
atom.  On an Xcinerama system the user will have to choose one  
profile to use for the entire system.  In Xquartz I expect that the  
server would settle on using the profile for the "primary" display  
(but at least OSX will have set the calibration individually for each  
screen).  Not a perfect system, but at least it's no worse than the  
current behaviour of a lot of "profile-aware" software (e.g. Apple  
Mail, Safari, iView MediaPro, etc) that only know about a single  
display profile.

Cheers
__
David Burren