screen selection in kgamma / Monitor Gamma

Duncan 1i5t5.duncan at
Fri Nov 11 18:31:57 GMT 2011

Klaus Klein posted on Fri, 11 Nov 2011 14:58:58 +0100 as excerpted:

> Hi folks,
>   I'm currently using Debian Squeeze with KDE 4.4.5 in parallel to a
>   WinXP environment in a dual boot configuration on my Dell C640 Laptop.
> Furthermore I'm trying to set up a Dual-Head configuration with an
> external Monitor.

> After searching through ->system settings->display for a while, and not
> being able to find brightness, contrast or gamma settings, I realized
> that kgamma was not installed by default. :-(


On gentoo, I'm running my own customized kde package set, so /nothing/ is 
installed by default.  The gentoo/kde folks ship a set list in the kde 
overlay (unfortunately, set support isn't in stable portage yet, so the 
set list can't hit the main tree yet, but I'm running the kde overlay in 
ordered to get current kde anyway), but I copy and rename those sets, 
commenting out packages I don't use, and diff the new sets against mine 
at every six-month 4.x kde bump, when they change, to see what I might 
need to add.

> Now, with kgamma installed, I still can change every setting provided by
> krandrtray and the screens are still identified correctly.
> Nevertheless, as the combo box discribed in the Monitor Gamma
> documentation on ("On multi head systems, select the screen you
> want to alter with the combo box.") is grayed out, kgamma will not allow
> me to select the second screen
> Am I still missing something or is this a bug (feature) ?

Unfortunately, I was hit by this some months ago, as well.  What the 
kgamma screen selector changes is the old xinerama and zaphod mode xorg 
"screen", which is quite dated on most modern systems, which now 
generally use RandR instead.  But kgamma hasn't been updated for randr, 

So it's simply outdated.  I imagine kgamma was more or less ported 
straight across from kde3, and hasn't had any real code updates in years.

I don't have time to check ATM myself, but you could check kde's bugzilla 
for a request bug on it, and either cc yourself, or create a new one if 
you don't find any.  Please post the bug number or link here, and I'll do 
the same.

Meanwhile, what I ultimately did is change the xorg.conf.d/* setting for 
the monitor in question, using xrandr or krandrtray to reactivate the 
monitor and update the setting, until I got what I wanted.  While kgamma 
changes only one monitor, I could still adjust kgamma and the xorg.conf.d/
* setting in tandem, until I got what I needed.  As it happens I didn't 
need to change the color balance, only the general gamma on all three 
channels, which helped.  In theory at least, you should be able to set 
the balance once on the monitor itself, for both OSs, and just change the 
overall gamma for X.

BTW/FWIW, xorg's default gamma is 1.0 (basically linear), while IIRC OSX 
uses 2.25 or some such and MSWormOS uses 1.8, I think.  But I could no 
longer (legally) run either of the proprietary OSs since I can't agree to 
the EULAs, so Linux it is, here, and the others are from memory.  (I 
could of course run one of the free BSDs too, if desired, but Linux has 
been my preference, and since they run xorg too, there shouldn't be a 
difference in this case.)

IIRC I ended up with something like 1.25, here.

Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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