KDE: Force color scheme for single application (feddit.org)

submitted 1 month ago by ackthxbye@feddit.org to c/linux4noobs@programming.dev

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I'm on Nobara Linux (with KDE6) using a dark theme. I'm using Unity Mod Manager on some games, which, with my current configuration has unreadable text on buttons etc because the text color is the same as the button-background.

When I switch the color in the settings to a light-mode theme like Breeze, everything in Unity Mod Manager becomes perfectly readable.

How do I force a single application to use light mode and/or a specific color-scheme?

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[-] Ephera@lemmy.ml 3 points 1 month ago

This might work: https://discuss.kde.org/t/change-color-or-theme-of-specific-window/1884/6

I'm not familiar with Unity Mod Manager, so hard to say or give detailed instructions.

If you happen to know how to run Unity Mod Manager from the terminal, the easiest way to check whether it will work, is by first running export GTK_THEME=Default and then running Unity Mod Manager in the same terminal.

This export command sets an environment variable (GTK_THEME). In case Unity Mod Manager respects the GTK theme of your system, it will presumably respect that environment variable.

From what I've quickly read up on Unity Mod Manager, it is implemented in C#, so I'm guessing it does not use GTK directly (but might still try to emulate its theme from the GTK theme) and well, it might behave weirdly under Linux in general...

[-] ackthxbye@feddit.org 1 points 1 month ago

Unfortunately doesn't work for me. I launch Unity Mod Manger with mono ./UnityModManager.exe but I also tried it on Kate, both with the commandline and the Menu-Editor shown in the last post. Both Unity Mod Manager and Kate launch, but do not change how they look.

[-] Ephera@lemmy.ml 1 points 1 month ago* (last edited 1 month ago)

Well, it won't work for Kate, because Kate is implemented using the Qt framework, so will preferentially use the Qt theme on your system. You would have to try it on e.g. Inkscape, which uses the GTK framework. (I did just try it on Inkscape to confirm that.)

We're getting into the technical details of how these applications are implemented, so I can't make this any less confusing.
But basically, KDE generally uses Qt, but it also generates a GTK theme, so that Inkscape et al don't look out of place.
Applications not specifically developed for Linux are likely to refer to that GTK theme for their own theming, even if they aren't implemented in GTK themselves. Firefox also does this, for example.

UnityModManager seems to be implemented using neither Qt, nor GTK, but rather Microsoft's .NET Framework. So, yeah, kind of no idea what it's gonna do here.

You could try telling KDE to generate a specific GTK theme and see if that does anything: (There's a button in the top-right of the screenshot.)

You may also want to see, if it's maybe this issue: https://github.com/newman55/unity-mod-manager/issues/88

[-] ackthxbye@feddit.org 2 points 3 weeks ago

Right, I confirmed UnityModManager looks different when I change the GTK theme.

Then, instead of Kate, I tried changing the GTK theme like you showed in Lutris and that works.

So the issue seems to lie with Mono. I found this old issue https://github.com/mono/mono/issues/9998 Mono seems to ignore the GTK_THEME environment variable. However there is a workaround: GTK_DATA_PREFIX= mono ./UnityModManager.exe makes mono default to a classic window theme.

Thanks for your help!

[-] Ephera@lemmy.ml 1 points 3 weeks ago

Ah, cool that you were able to fix it! 🙂

this post was submitted on 11 Dec 2025

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