anchor.diff:        style = mkOption {
           type = types.enum [
             "adwaita"
  +          "adwaita-dark"
             "cleanlooks"
             "gtk2"
             "motif"
  
positive.code:           <variablelist>
              <varlistentry>
                <term><literal>adwaita</literal></term>
                <listitem><para>Use Adwaita Qt style with
                  <link xlink:href="https://github.com/FedoraQt/adwaita-qt">adwaita</link>
                </para></listitem>
  
negative.code: 
    cfg = config.qt5;
  
    isQGnome = cfg.platformTheme == "gnome" && builtins.elem cfg.style ["adwaita" "adwaita-dark"];
    isQtStyle = cfg.platformTheme == "gtk2" && !(builtins.elem cfg.style ["adwaita" "adwaita-dark"]);
  
    packages = if isQGnome then [ pkgs.qgnomeplatform pkgs.adwaita-qt ]
      else if isQtStyle then [ pkgs.libsForQt5.qtstyleplugins ]
  