anchor.diff:    buildInputs = [ glib libXinerama ]
       ++ optionals docsSupport        [ docbook2x docbook_xsl docbook_xml_dtd_44 libxslt man less ]
       ++ optional  ncursesSupport     ncurses
  -    ++ optional  x11Support         xlibsWrapper
  +    ++ optionals x11Support         [ freetype xorg.libICE xorg.libX11 xorg.libXext xorg.libXft xorg.libSM ]
       ++ optional  xdamageSupport     libXdamage
       ++ optional  imlib2Support      imlib2
       ++ optional  luaSupport         lua
  
positive.code:                             , docbook_xsl ? null , docbook_xml_dtd_44 ? null
  
  , ncursesSupport      ? true      , ncurses       ? null
  , x11Support          ? true      , xlibsWrapper           ? null
  , xdamageSupport      ? x11Support, libXdamage    ? null
  , doubleBufferSupport ? x11Support
  , imlib2Support       ? x11Support, imlib2        ? null
  
negative.code: 
  assert ncursesSupport      -> ncurses != null;
  
  assert xdamageSupport      -> x11Support && libXdamage != null;
  assert imlib2Support       -> x11Support && imlib2     != null;
  assert luaSupport          -> lua != null;
  