anchor.diff:  
   stdenv.mkDerivation rec {
     pname = "gtk-vnc";
  -  version = "1.2.0";
  +  version = "1.3.0";
   
     outputs = [ "out" "bin" "man" "dev" ];
   
     src = fetchurl {
       url = "mirror://gnome/sources/${pname}/${lib.versions.majorMinor version}/${pname}-${version}.tar.xz";
  -    sha256 = "0jmr6igyzcj2wmx5v5ywaazvdz3hx6a6rys26yb4l4s71l281bvs";
  +    sha256 = "X6qlgjuMvowLC6HkVsTnDEsa5mhcn+gaQoLZjPAKIR0=";
     };
   
     nativeBuildInputs = [
  
positive.code:     vala
      gettext
      perl # for pod2man
    ];
  
    buildInputs = [
  
negative.code: , vala
  , gettext
  , perl
  , python3
  , gnome
  , gdk-pixbuf
  , zlib
  