Sddm: customize the currently applied theme

roles/kde/plasma.nix

@@ -19,8 +19,12 @@ let
 in
 
 {
-	# Enable the Plasma 5 Desktop Environment.
+	services.xserver = {
-	services.xserver.desktopManager.plasma5.enable = true;
+		# Enable the Plasma 5 Desktop Environment
+		desktopManager.plasma5.enable = true;
+		displayManager.defaultSession = "plasmawayland";
+	};
+
 
 	# GTK apps need dconf to grab the correct theme on Wayland
 	programs.dconf.enable = true;
@@ -57,5 +61,4 @@ in
 		"xdg/gtkrc-2.0".text = gtk1and2settings;
 		"xdg/gtkrc".text = gtk1and2settings;
 	};
-	environment.systemPackages = [pkgs.yaru-theme];
 }

roles/kde/sddm.nix

@@ -1,15 +1,57 @@
-{ config, ... }:
+{ config, pkgs, ... }:
+
+let
+	currentTheme = config.services.xserver.displayManager.sddm.theme;
+
+	sddm-sugar-candy = pkgs.stdenv.mkDerivation {
+		pname = "sddm-sugar-candy";
+		version = "master";
+		src = pkgs.fetchgit {
+			url = "https://framagit.org/MarianArlt/sddm-sugar-candy.git";
+			hash = "sha256-XggFVsEXLYklrfy1ElkIp9fkTw4wvXbyVkaVCZq4ZLU=";
+		};
+		installPhase = ''
+			runHook preInstall
+
+			mkdir -p $out/share/sddm/themes/sugar-candy
+			cp -r /build/sddm-sugar-candy/* $out/share/sddm/themes/sugar-candy
+
+			runHook postInstall
+		'';
+	};
+
+	/*
+	Adds a theme.conf.user file to the current sddm theme's folder,
+	allowing you to change it's configuration without needing to
+	repackage it
+	*/
+	customcfg = pkgs.stdenv.mkDerivation {
+		name = "sddm-theme-customizer";
+		dontUnpack = true;
+		# TODO: generate theme.conf.user outside of installPhase
+		installPhase = ''
+			runHook preInstall
+
+			mkdir -p $out/share/sddm/themes/${currentTheme}/
+			echo "[General]
+			background = ${pkgs.plasma-workspace-wallpapers}/share/wallpapers/MilkyWay/contents/images/5120x2880.png" >> $out/share/sddm/themes/${currentTheme}/theme.conf.user
+
+			runHook postInstall
+		'';
+	};
+in
 
 {
 	# Enable SDDM.
 	services.xserver.displayManager.sddm = {
 		enable = true;
+		theme = "sugar-candy";
 		settings = {
 			General = { Numlock = "on"; };
 		};
 	};
 
-
+	environment.systemPackages = [ sddm-sugar-candy customcfg ];
 	/*
 	Sddm has a very annoying bug where it sometimes hangs at shutdown
 	if you use Plasma's wayland session. The bug is already fixed upstream,