qt: add module

modules/misc/news.nix

@@ -647,6 +647,16 @@ in
           A new module is available: 'services.flameshot'.
         '';
       }
+
+      {
+        time = "2018-05-18T18:34:15+00:00";
+        message = ''
+          A new module is available: 'qt'
+
+          At the moment this module allows you to set up Qt to use the
+          GTK+ theme, and not much else.
+        '';
+      }
     ];
   };
 }

modules/misc/qt.nix

@@ -0,0 +1,39 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.qt;
+  dag = config.lib.dag;
+
+in
+
+{
+  meta.maintainers = [ maintainers.rycee ];
+
+  options = {
+    qt = {
+      enable = mkEnableOption "Qt 4 and 5 configuration";
+
+      useGtkTheme = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Whether Qt 4 and 5 should be set up to use the GTK theme
+          settings.
+        '';
+      };
+    };
+  };
+
+  config = mkIf (cfg.enable && cfg.useGtkTheme) {
+    home.sessionVariables.QT_QPA_PLATFORMTHEME = "gtk2";
+    home.packages = [ pkgs.libsForQt5.qtstyleplugins ];
+
+    home.activation.useGtkThemeInQt4 = dag.entryAfter ["writeBoundary"] ''
+      $DRY_RUN_CMD ${pkgs.crudini}/bin/crudini $VERBOSE_ARG \
+        --set $HOME/.config/Trolltech.conf Qt style GTK+
+    '';
+  };
+}

modules/modules.nix

@@ -21,6 +21,7 @@ let
     ./misc/news.nix
     ./misc/nixpkgs.nix
     ./misc/pam.nix
+    ./misc/qt.nix
     ./misc/xdg.nix
     ./programs/autorandr.nix
     ./programs/bash.nix