anchor.diff:      ++ lib.optionals enableInventor [ libXpm coin3d soxt motif ]
       ++ lib.optionals enablePython [ boost_python python3 ];
   
  -  propagatedBuildInputs = [ clhep expat zlib libGL ]
  -    ++ lib.optionals enableGDML [ xercesc ]
  +  propagatedBuildInputs = [ clhep expat xercesc zlib libGL ]
       ++ lib.optionals enableXM [ motif ]
       ++ lib.optionals enableQT [ qtbase ];
   
  
positive.code: 
    cmakeFlags = [
      "-DGEANT4_INSTALL_DATA=OFF"
      "-DGEANT4_USE_GDML=${if enableGDML then "ON" else "OFF"}"
      "-DGEANT4_USE_G3TOG4=${if enableG3toG4 then "ON" else "OFF"}"
      "-DGEANT4_USE_QT=${if enableQT then "ON" else "OFF"}"
      "-DGEANT4_USE_XM=${if enableXM then "ON" else "OFF"}"
      "-DGEANT4_USE_OPENGL_X11=${if enableOpenGLX11 then "ON" else "OFF"}"
  
negative.code: # Standard build environment with cmake.
  , lib, stdenv, fetchurl, fetchpatch, cmake
  
  , clhep ? null # not packaged currently
  , expat
  , xercesc
  , zlib
  
  # For enableQT.
  , qtbase
  