this post was submitted on 04 Mar 2024
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I have calibrated my monitors to create icc profiles, they show up in KDE color management and everything used to work exactly as it should. Now every time I start my computer it goes like this:

  1. I log in to my account
  2. It shows my desktop, with the right colour correction.
  3. After a few seconds the colours revert to look un-calibrated on both monitors.
  4. I restart the colord service and it loads the colour correction again.

As an alternative to step 4, if I go to KDE colour settings, select the default profile and then back to my profile then it also starts looking good again.

This problem must've started a week or two ago, but unfortunately I haven't been able to pinpoint exactly when. I haven't touched anything related to colour management in months, and don't think I've done any changes to my system other than upgrading packages.

Can't see anything colour related in the syslog except colord loading the correct profiles. I removed all the old profiles that I wasn't using anyway. I removed dispcal's profile loader from autostart to make sure it wasn't interfering with something. The profiles are both installed system wide and in my user folder.

Using Fedora 39 KDE.

Anyone have any idea what could be wrong, or even how to debug this?

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[–] [email protected] 4 points 4 months ago (1 children)

Is that on Xorg, or on Wayland? On Xorg, a bunch of different processes can try to take control over the gamma_lut of a screen (like night light in KWin vs the gamma settings page vs some games like CS2 vs colord), so if you're on Xorg I'd be surprised if you didn't have issues with it sooner...

[–] [email protected] 1 points 4 months ago

Xorg, but it has worked without issues on Fedora for over a year, and it also worked on Xubuntu before that :/

I know nvidia-settings messes up the colors if I open its GUI, but I haven't found any other program which does so. I do use nvidia-settings from a script when power limiting + overclocking my GPU, but I have verified that it doesn't mess with the colours, and I've also had it for almost a year so it's not new.

[–] [email protected] 3 points 4 months ago (2 children)

I am so glad to have come across this post because I thought I was going crazy. My colour was resetting and darkening, figured I was somehow hitting the button by mistake for it on my monitor to change between a preset or something. Had no idea the monitor could be controlled from the pc like that?

Glad I am not the only one having this problem

[–] [email protected] 3 points 4 months ago

Colour management/correction is done by the computer without involving the monitor afaik.

But I have a suspicion what might be causing your issue.. Computers can indeed control monitor settings such as brightness and power on/off through something which I believe is called DDC/CI (in case you wanna search for more information). When I bought a new Dell monitor I got an issue where it would randomly change brightness every now and then. I have my Linux PC hooked up to 2 monitors, and my work Windows laptop also connected to one of them. So while I was working, my own PC would think that I was idle and dimmed the screens. However, unlike my old monitors, the Dell would accept DDC/CI commands on all connections, not only the selected one. I just turned off monitor dimming in KDE control panel power settings as a workaround, and let it turn the monitor signal off immediately on inactivity.

While researching the issue, I also came across multiple posts by people having problems with Dell monitors randomly changing brightness, with only one computer connected, so it could also be that.. Dell has a reset procedure which they claim should fix it, but it's different for pretty much every model, so you'll have to find the one for yours, in case you have a Dell monitor. Some people wrote that it didn't work and they had to RMA the monitors.

[–] [email protected] 1 points 4 months ago* (last edited 4 months ago)

This post has also confirmed that I, also, am not crazy. I knew its was changing randomly!

[–] [email protected] 3 points 4 months ago (1 children)

No idea other than some ideas to maybe debug this.

Maybe monitor process executions and see what is going on? Either using the auditing subsystem, https://secopsmonkey.com/monitoring-process-execution-with-auditd.html of BFP perhaps. I saw a look of BFP but not sure if it is a good result: https://medium.com/@yunwei356/ebpf-tutorial-by-example-7-capturing-process-execution-event-printing-output-with-perf-event-cc6213d19c76

[–] [email protected] 1 points 4 months ago

Thanks! I'll give it a try. Never used it before but it sounds interesting

[–] [email protected] 3 points 4 months ago (1 children)

I'm away from my computer right now, so Im not 100% sure, but I think you can set display profiles. You should be able to set a display profile that will auto load on login and should set your display options that you want. Maybe this can work despite the colord issues?

I'll verify if kde display profiles are a thing and if they can help your use case tomorrow.

[–] [email protected] 1 points 4 months ago (1 children)

I meant I use the KDE colour management settings to set the calibrated icc profiles for each display. I guess it uses colord under the hood, since restarting the service reloads the profiles. Or did you mean some other kind of display profile?

[–] [email protected] 1 points 4 months ago (1 children)

Sorry. I think it was gnome I was thinking about. The display configuration for gnome allows for specifying layout and advanced profiles when it detects certain monitors are plugged in. Things like dpi, font size, etc. I have a computer hooked up to my TV that runs gnome and another that upstairs running kde

[–] [email protected] 1 points 4 months ago

No worries, any attempt to help solve this is welcome :)