qt: added qt{5,6}ctSettings options (#8271)

Added qtctSettings option to qt module to make it possible to configure qt(5/6)ct declaratively.

modules/misc/qt.nix

@@ -8,6 +8,10 @@
 let
   cfg = config.qt;
 
+  qtctFormat = pkgs.formats.ini {
+    listToValue = values: lib.concatStringsSep ", " values;
+  };
+
   # Map platform names to their packages.
   platformPackages = with pkgs; {
     gnome = [
@@ -286,7 +290,34 @@ in
           '';
         };
       };
-    };
+    }
+    // (lib.genAttrs' [ "qt5ct" "qt6ct" ] (
+      name:
+      lib.nameValuePair "${name}Settings" (
+        lib.mkOption {
+          type = lib.types.nullOr qtctFormat.type;
+          default = null;
+          example = lib.literalExpression ''
+            {
+              Appearance = {
+                style = "kvantum";
+                icon_theme = "Papirus-Dark";
+                standar_dialogs = "xdgdesktopportal";
+              };
+              Fonts = {
+                fixed = "\"DejaVuSansM Nerd Font Mono,12\"";
+                general = "\"DejaVu Sans,12\"";
+              };
+            }
+          '';
+          description = ''
+            Qtct configuration. Writes settings to `${name}/${name}.conf`
+            file. Lists will be translated to comma-separated strings.
+            Fonts must be quoted (see example).
+          '';
+        }
+      )
+    ));
   };
 
   config =
@@ -397,5 +428,18 @@ in
       ]
       ++ lib.optionals (platformTheme.name != null) [ "QT_QPA_PLATFORMTHEME" ]
       ++ lib.optionals (cfg.style.name != null) [ "QT_STYLE_OVERRIDE" ];
+
+      xdg.configFile =
+        lib.pipe
+          [ "qt5ct" "qt6ct" ]
+          [
+            (lib.filter (qtct: cfg."${qtct}Settings" != null))
+            (lib.flip lib.genAttrs' (
+              qtct:
+              lib.nameValuePair "${qtct}/${qtct}.conf" {
+                source = qtctFormat.generate "${qtct}-config" cfg."${qtct}Settings";
+              }
+            ))
+          ];
     };
 }

tests/modules/misc/qt/default.nix

@@ -4,4 +4,7 @@
   qt-platform-theme-gtk3 = ./qt-platform-theme-gtk3.nix;
   qt-platform-theme-gnome = ./qt-platform-theme-gnome.nix;
   qt-platform-theme-kde6-migration = ./qt-platform-theme-kde6-migration.nix;
+  qt-qt5ct-settings = ./qt-qt5ct-settings.nix;
+  qt-qt6ct-settings = ./qt-qt6ct-settings.nix;
+  qt-qtct-settings = ./qt-qtct-settings.nix;
 }

tests/modules/misc/qt/qt-qt5ct-settings.nix

@@ -0,0 +1,13 @@
+{
+  qt = {
+    enable = true;
+    qt5ctSettings = {
+      test_section.test_option = "test";
+    };
+  };
+
+  nmt.script = ''
+    assertFileExists "home-files/.config/qt5ct/qt5ct.conf"
+    assertPathNotExists "home-files/.config/qt6ct/qt6ct.conf"
+  '';
+}

tests/modules/misc/qt/qt-qt6ct-settings.nix

@@ -0,0 +1,13 @@
+{
+  qt = {
+    enable = true;
+    qt6ctSettings = {
+      test_section.test_option = "test";
+    };
+  };
+
+  nmt.script = ''
+    assertFileExists "home-files/.config/qt6ct/qt6ct.conf"
+    assertPathNotExists "home-files/.config/qt5ct/qt5ct.conf"
+  '';
+}

tests/modules/misc/qt/qt-qtct-settings.nix

@@ -0,0 +1,16 @@
+{
+  qt = {
+    enable = true;
+    qt5ctSettings = {
+      test_section.test_option = "test";
+    };
+    qt6ctSettings = {
+      test_section.test_option = "test";
+    };
+  };
+
+  nmt.script = ''
+    assertFileExists "home-files/.config/qt5ct/qt5ct.conf"
+    assertFileExists "home-files/.config/qt6ct/qt6ct.conf"
+  '';
+}