[xorg-xgamma] Xgamma and xrandr discrepancy

Adrian C. anrxc at sysphere.org
Sat Dec 21 08:14:38 PST 2013

Hello I have a small issue with xgamma for a very long time that nobody 
could explain to me, so now I'd like to ask the developers.

To get decent colors on my workstation and external monitors I want to 
apply gamma correction. For me these magic values do it "Gamma 0.75 0.65 
0.60", I set them in xorg.conf for each monitor.

If it happens that an external monitor wasn't connected when I started X 
I can attach it with xrandr. Well when I do that the colors on the 
monitor are completely off. Even though xgamma reports "-> Red 0.750, 
Green 0.650, Blue 0.600" when I check, the colors are simply wrong. I 
have to kill X, start, and everything is back to normal. These forced 
restarts partly defeat the hotplugging ideas in xrandr.

Here's what Xorg.0.log has to say:
> [ 44816.100] (II) intel(0): Using default gamma of (1.0, 1.0, 1.0)  unless otherwise stated.
> [ 44816.101] (II) intel(0): Output VGA1 wants gamma correction (0.8, 0.6, 0.6)

Trying to correct colors my self, after using xrandr, isn't succesful. 
xgamma doesn't produce good colors. I have also tried to set gamma with 
xrandr, both when attaching the display or afterwords, i.e. by using 
this switch --gamma 0.75:0.65:0.60 or --gamma 0.8:0.6:0.6. This produces 
bad results as well. Colors are always wrong, always very washed out to 
my eye.

Nothing but an X restart does it for years, across 5 portable computers 
and all forms and sizes of CRT and LCD monitors. Could anyone explain 
why? Thanks.

Adrian C. (anrxc) | anrxc..sysphere.org | PGP ID: D20A0618
PGP FP: 02A5 628A D8EE 2A93 996E  929F D5CB 31B7 D20A 0618

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