KDE

KDE Plasma is a desktop environment that aims to be simple by default, powerful when needed.

Installation

To use KDE Plasma, add this to your configuration.nix:

services.xserver.enable = true;
services.xserver.displayManager.sddm.enable = true;
services.xserver.desktopManager.plasma5.enable = true;

Or if you want to use Plasma 6, available on nixpkgs-unstable:

services.xserver.enable = true;
services.xserver.displayManager.sddm.enable = true;
services.desktopManager.plasma6.enable = true;

Excluding some KDE Plasma applications from the default install

Plasma 5

Not all applications that come pre-installed with the KDE Plasma desktop environment are desirable for everyone to have on their machines. There's a way to edit configuration.nix to exclude some optional packages, for example as follows:

environment.plasma5.excludePackages = with pkgs.libsForQt5; [
  plasma-browser-integration
  konsole
  oxygen
];

Plasma 6

environment.plasma6.excludePackages = with pkgs.kdePackages; [
  plasma-browser-integration
  konsole
  oxygen
];

Configuration

GNOME desktop integration

Using the following example configuration, QT applications will have a look similar to the GNOME desktop, using a dark theme.

qt = {
  enable = true;
  platformTheme = "gnome";
  style = "adwaita-dark";
};

For other themes, you may need the packages libsForQt5.qt5ct and libsForQt5.qtstyleplugin-kvantum and a symlink from ~/.config/Kvantum/ to your theme package. Here is an example using Arc-Dark and Home Manager. In the Home Manager configuration:

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

xdg.configFile = {
  "Kvantum/ArcDark".source = "${pkgs.arc-kde-theme}/share/Kvantum/ArcDark";
  "Kvantum/kvantum.kvconfig".text = "[General]\ntheme=ArcDark";
};

For more details, see this forum post.

Troubleshooting

Qt/KDE applications segfault on start

This is caused by a stale QML cache (see this issue). A dirty way to fix this is by running on a terminal the following command:

find ${XDG_CACHE_HOME:-$HOME/.cache}/**/qmlcache -type f -delete

GTK themes are not applied in Wayland applications / Window Decorations missing / Cursor looks different

This affects GTK applications including Firefox and Thunderbird.

Add to your configuration.nix the following line:

programs.dconf.enable = true;

You might also need to set a GTK theme Breeze imitating the KDE theme with the same name in System Settings -> Application Style -->Configure GNOME/GTK Application Style.

(See this issue)

KMail Renders Blank Messages

When you see the message grantlee.template: "Plugin library 'kde_grantlee_plugin' not found." and/or kmail does shows only empty message then add to your configuration.nix the following line:

environment.sessionVariables = {
  NIX_PROFILES = "${pkgs.lib.concatStringsSep " " (pkgs.lib.reverseList config.environment.profiles)}";
};

(See this issue)

Launch KDE in Wayland session

Plasma 5

services.xserver.displayManager.defaultSession = "plasmawayland";

Plasma 6

For KDE Plasma 6, the defaults have changed. KDE Plasma 6 runs on Wayland with the default session set to plasma. If you want to use the X11 session as your default session, change it to plasmax11.

services.xserver.displayManager.defaultSession = "plasma";

Launch SDDM in Wayland too

It's possible to launch sddm in Wayland too to try to avoid running an X server.

services.xserver.displayManager.sddm.wayland.enable = true;

Tips and tricks

Plasma-Manager

Note: Plasma-Manager is not matured yet and currently unofficial

By default, the Plasma configuration can be handled like on traditional systems. With plasma-manager, it is possible to make Plasma configurations via nix by providing home-manager modules.