anchor.diff:  { enableMultiThreading ? true
  -, enableG3toG4         ? false
   , enableInventor       ? false
  -, enableGDML           ? false
   , enableQT             ? false
   , enableXM             ? false
   , enableOpenGLX11      ? true
  
positive.code:     "-DGEANT4_USE_PYTHON=${if enablePython then "ON" else "OFF"}"
      "-DGEANT4_USE_RAYTRACER_X11=${if enableRaytracerX11 then "ON" else "OFF"}"
      "-DGEANT4_USE_SYSTEM_CLHEP=${if clhep != null then "ON" else "OFF"}"
      "-DGEANT4_USE_SYSTEM_EXPAT=${if expat != null then "ON" else "OFF"}"
      "-DGEANT4_USE_SYSTEM_ZLIB=${if zlib != null then "ON" else "OFF"}"
      "-DGEANT4_BUILD_MULTITHREADED=${if enableMultiThreading then "ON" else "OFF"}"
    ] ++ lib.optionals stdenv.isDarwin [
      "-DXQuartzGL_INCLUDE_DIR=${libGL.dev}/include"
  
negative.code:     ++ lib.optionals enableInventor [ libXpm coin3d soxt motif ]
      ++ lib.optionals enablePython [ boost_python python3 ];
  
    propagatedBuildInputs = [ clhep expat xercesc zlib libGL ]
      ++ lib.optionals enableXM [ motif ]
      ++ lib.optionals enableQT [ qtbase ];
  
  