anchor.diff:  
   let
     ver_maj = "3.16";
  -  ver_min = "6";
  +  ver_min = "7";
     version = "${ver_maj}.${ver_min}";
   in
   stdenv.mkDerivation rec {
  
positive.code: 
    src = fetchurl {
      url = "mirror://gnome/sources/gtk+/${ver_maj}/gtk+-${version}.tar.xz";
      sha256 = "1gpzlnfrifc17yfk0zki6b2vmsfpf5cmrbh232s6iaan11np44jd";
    };
  
    nativeBuildInputs = [ pkgconfig gettext gobjectIntrospection perl ];
  
negative.code:     ''; # workaround for bug of nix-mode for Emacs */ '';
    };
  
    meta = with stdenv.lib; {
      description = "A multi-platform toolkit for creating graphical user interfaces";
  
      longDescription = ''
  