anchor.diff:  { lib
   , stdenv
   , fetchurl
  +, SDL2
  +, curl
   , docbook_xml_dtd_45
   , docbook_xsl
  -, libtool
  -, pkg-config
  -, curl
  -, readline
  -, wget
  -, libobjc
  -, enableX11 ? !stdenv.isDarwin
  +, gtk3
   , libGL
   , libGLU
   , libX11
   , libXpm
  -, enableSdl2 ? true
  -, SDL2
  +, libobjc
  +, libtool
  +, ncurses
  +, pkg-config
  +, readline
  +, wget
  +, wxGTK
  +, enableSDL2 ? true
   , enableTerm ? true
  -, ncurses
   , enableWx ? !stdenv.isDarwin
  -, wxGTK
  -, gtk3
  +, enableX11 ? !stdenv.isDarwin
   }:
   
   stdenv.mkDerivation (finalAttrs: {
  
positive.code:     "--enable-plugins"
      "--enable-pnic"
      "--enable-sb16"
    ] ++ lib.optionals enableX11 [
      "--with-x"
      "--with-x11"
    ] ++ lib.optionals enableSdl2 [
      "--with-sdl2"
    ] ++ lib.optionals enableTerm [
      "--with-term"
    ] ++ lib.optionals enableWx [
      "--with-wx"
    ];
  
    enableParallelBuilding = true;
  
negative.code:     "--enable-voodoo"
      "--enable-x86-64"
      "--enable-x86-debugger"
    ] ++ lib.optionals enableSDL2 [
      "--with-sdl2"
    ] ++ lib.optionals enableTerm [
      "--with-term"
    ] ++ lib.optionals enableWx [
      "--with-wx"
    ] ++ lib.optionals enableX11 [
      "--with-x"
      "--with-x11"
    ] ++ lib.optionals (!stdenv.isDarwin) [
      "--enable-e1000"
      "--enable-es1370"
  