anchor.diff:  , docbook_xml_dtd_45
   , docbook_xml_dtd_42
   }:
  +
  +# Documentation is only built when building libraries.
  +assert withDocumentation -> withLibraries;
   
   # Require the optional to be enabled until upstream fixes or removes the configure flag
   assert expat != null;
  
positive.code: , libxml2
  , wayland
  , expat ? null # Build wayland-scanner (currently cannot be disabled as of 1.7.0)
  , withDocumentation ? stdenv.hostPlatform == stdenv.buildPlatform
  , graphviz-nox
  , doxygen
  , libxslt
  
negative.code:   ];
  
    buildInputs = [
      expat
      libxml2
    ] ++ lib.optionals withLibraries [
      libffi
    ] ++ lib.optionals withDocumentation [
      docbook_xsl
      docbook_xml_dtd_45
      docbook_xml_dtd_42
    ];
  
    meta = with lib; {
      description = "Core Wayland window system code and protocol";
      longDescription = ''
        Wayland is a project to define a protocol for a compositor to talk to its
  