How to fix qt themes in nixos?

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1

I’m trying out nixos in a virtual machine (gnome desktop) to test it outandI’ve come to love it, except for the fact that qt themes don’t really work,pic related https://files.catbox.moe/gj7vcw.jpg. I tried installing qt5ct tosee if that fixes the issue but in the styles optionsit doesn’t give me anoption to select gtk. I thought of using kvantum to fixthe problem but it’snot in the nixos repo. Does anyone have any idea on how Icould fix this?Myconfiguration.nix is here https://files.catbox.moe/1l3gmv.nix

2

This page in the ArchLinux wiki may be helpful, as most of the strategies described apply to NixOS too.

Kvantum is in nixpkgs: NixOS Search - Loading...

3

You can check my config here configurations/dracula.nix at 0f41d4a04c6dce1ceac6ab4e4aeaf588f68be844 · addy419/configurations · GitHub If you face issues with theme consistency even after installing Kvantum, I highly suggest using lxqt-config (also in the dots above)

4

To get Qt themes working on Nixos you need to install the theme engine you want to use, and then use the QT_STYLE_OVERRIDE environment variable to select it.

For example, I’m using the following, which works for VLC:

/etc/nixos/confuration.nix:

   ...
      environment.systemPackages = with pkgs; [
        # The following is a Qt theme engine, which can be configured with kvantummanager
        libsForQt5.qtstyleplugin-kvantum
     ];

     environment.variables = {
        # This will become a global environment variable
       "QT_STYLE_OVERRIDE"="kvantum";
     };

Even after a nixos-rebuild switch the settings won’t take effect. The simplest way is to simply log back in, that way /etc/profile is sourced properly.

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5

This is no longer working as of Nixos 22,
somehow the QT styles are now hardcoded into the module:

building Nix...
building the system configuration...
error: The option `environment.variables.QT_QPA_PLATFORMTHEME' has conflicting definition values:
       - In `/etc/nixos/configuration.nix': "qt5ct"
       - In `/nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/config/qt5.nix': "gnome"
(use '--show-trace' to show detailed location information)

  environment.variables = {
    QT_QPA_PLATFORMTHEME = "qt5ct";
  };
6

You can override this using

  environment.variables = lib.mkForce {
    QT_STYLE_OVERRIDE = "{theme}";
  };

I think qt.style needs to be modified to include options for qt5ct and kvantum if they’re installed.

1 Like
7

hello quasi a god :grinning_face_with_smiling_eyes:
This also doesn’t seem to work for me.
How would I modify qt.style?

8

What theme exactly are you trying to use? Are you using something like qt5ct or Kvantum to set your theme?

9

My config seems pretty straight forward but each time I open kvantummanager the kvantum (default) is selected and I can’t seems to change to my installed theme.

qt.enable = true;
qt.platformTheme = "qtct";
qt.style.name = "kvantum";

home.packages = with pkgs; [

  (catppuccin-kvantum.override {
    accent = "Mauve";
    variant = "Mocha";
  })
];

xdg.configFile."Kvantum/kvantum.kvconfig".source = (pkgs.formats.ini {}).generate "kvantum.kvconfig" {
  General.Theme = "Catppuccin-Mocha-Mauve";
};
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10

If you remove the xdg.configFile and open Kvantum, do you see the catppuccin theme in the list?

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11

I feel very dumb mentioning this but apparently “Theme” needed to be “theme”. Of course kvantummanager couldn’t change the theme because its config was read-only since it was in the nix store.

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12

Haha it happens. For config files like that, I usually set it up in the GUI then add it to my Nix config by just pasting the text in.

1 Like