anchor.diff:  { stdenv, fetchurl, pkgconfig, gtk3, glibmm, cairomm, pangomm, atkmm, epoxy }:
   
   let
  -  ver_maj = "3.18";
  +  ver_maj = "3.20";
     ver_min = "0";
   in
   stdenv.mkDerivation rec {
  
positive.code: 
    src = fetchurl {
      url = "mirror://gnome/sources/gtkmm/${ver_maj}/${name}.tar.xz";
      sha256 = "829fa113daed74398c49c3f2b7672807f58ba85d0fa463f5bc726e1b0138b86b";
    };
  
    nativeBuildInputs = [ pkgconfig ];
  
negative.code:   propagatedBuildInputs = [ glibmm gtk3 atkmm cairomm pangomm ];
  
    enableParallelBuilding = true;
  
    # https://bugzilla.gnome.org/show_bug.cgi?id=764521
    doCheck = false;
  
    meta = with stdenv.lib; {
      description = "C++ interface to the GTK+ graphical user interface library";
  