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