plasma: configure default gtk theme

roles/kde/plasma.nix

@@ -1,7 +1,62 @@
 { config, pkgs, lib, ... }:
 
+let
+	themeName = "Breeze";
+	gtk3and4settings = lib.generators.toINI {} {
+		Settings = {
+			gtk-theme-name = themeName;
+			gtk-cursor-theme-name = "breeze_cursors";
+		};
+	};
+
+	# The configuration files that Plasma made have set the theme in gtkrc, not gtkrc-2.0
+	# which is weird cause applying the theme to gtk1 but not 2 is dumb. I'll write it to
+	# both files just in case :3
+	gtk1and2settings = ''
+	include "/run/current-system/sw/share/themes/${themeName}/gtk-2.0/gtkrc"
+	gtk-theme-name="${themeName}"
+	'';
+in
+
 {
 	# Enable the Plasma 5 Desktop Environment.
 	services.xserver.displayManager.sddm.enable = true;
 	services.xserver.desktopManager.plasma5.enable = true;
+
+	# GTK apps need dconf to grab the correct theme on Wayland
+	programs.dconf.enable = true;
+
+	# The NixOS dconf module doesn't support creating databases
+	# (https://github.com/NixOS/nixpkgs/issues/54150), so I'm
+	# doing it manualy
+
+	# https://help.gnome.org/admin/system-admin-guide/stable/dconf-custom-defaults.html.en
+	environment.etc = {
+		"dconf/profile/user".text = "user-db:user\nsystem-db:local";
+		"dconf/db/local.d/00-defaultTheme".text = ''
+			[org/gnome/desktop/interface]
+			gtk-theme='${themeName}'
+		'';
+	};
+
+	system.activationScripts = {
+		dconf = {
+			text= ''
+			echo "updating system dconf database..."
+			${pkgs.dconf}/bin/dconf update
+			touch /testfile
+			'';
+			deps = [ "etc" ];
+		};
+	};
+
+	# Set up GTK to use Breeze instead of adwaita by default
+	# Theese only seem to work on X11, not wayland
+	environment.etc = {
+		"xdg/gtk-4.0/settings.ini".text = gtk3and4settings;
+		"xdg/gtk-3.0/settings.ini".text = gtk3and4settings;
+		"xdg/gtkrc-2.0".text = gtk1and2settings;
+		"xdg/gtkrc".text = gtk1and2settings;
+	};
+	environment.systemPackages = [pkgs.yaru-theme];
 }