anchor.diff: -{ stdenv, fetchurl, cmake, libGLU_combined, libX11, xorgproto, libXt
  +{ stdenv, fetchurl, cmake, libGLU_combined, libX11, xorgproto, libXt, libtiff
   , qtLib ? null
   # Darwin support
   , Cocoa, CoreServices, DiskArbitration, IOKit, CFNetwork, Security, GLUT, OpenGL
  
positive.code:     sha256 = "0nm7xwwj7rnsxjdv2ssviys8nhci4n9iiiqm2y14s520hl2dsp1d";
    };
  
    buildInputs = [ cmake ]
      ++ optional (qtLib != null) qtLib
      ++ optionals stdenv.isLinux [ libGLU_combined libX11 xorgproto libXt ]
      ++ optionals stdenv.isDarwin [ xpc Cocoa CoreServices DiskArbitration IOKit
  
negative.code:   # built and requiring one of the shared objects.
    # At least, we use -fPIC for other packages to be able to use this in shared
    # objects.
    cmakeFlags = [ "-DCMAKE_C_FLAGS=-fPIC" "-DCMAKE_CXX_FLAGS=-fPIC" "-DVTK_USE_SYSTEM_TIFF=1" ]
      ++ optional (qtLib != null) [ "-DVTK_USE_QT:BOOL=ON" ]
      ++ optional stdenv.isDarwin "-DOPENGL_INCLUDE_DIR=${OpenGL}/Library/Frameworks";
  
  