anchor.diff:  let
     boolToCMake = b: if b then "ON" else "OFF";
   
  -  irrlichtMt = stdenv.mkDerivation rec {
  -    pname = "irrlichtMt";
  -    version = "1.9.0mt4";
  -    src = fetchFromGitHub {
  -      owner = "minetest";
  -      repo = "irrlicht";
  -      rev = version;
  -      sha256 = "sha256-YlXn9LrfGkjdb8+zQGDgrInolUYj9nVSF2AXWFpEEkw=";
  -    };
  -    nativeBuildInputs = [ cmake ];
  -    buildInputs = [ zlib libjpeg libpng libGLU libGL libXrandr libX11 libXxf86vm ]
  -    ++ lib.optionals stdenv.isDarwin [ Cocoa Kernel ];
  -    outputs = [ "out" "dev" ];
  -    meta = irrlicht.meta;
  -  };
  +  irrlichtmtInput = irrlichtmt.override { inherit withTouchSupport; };
   
     generic = { version, rev ? version, sha256, dataRev ? version, dataSha256, buildClient ? true, buildServer ? false }: let
       sources = {
  
positive.code:       "-DOpenGL_GL_PREFERENCE=GLVND"
      ] ++ optionals buildServer [
        "-DENABLE_PROMETHEUS=1"
      ];
  
      NIX_CFLAGS_COMPILE = "-DluaL_reg=luaL_Reg"; # needed since luajit-2.1.0-beta3
  
negative.code: { lib, stdenv, fetchFromGitHub, cmake, irrlichtmt, libpng, bzip2, curl, libogg, jsoncpp
  , libjpeg, libXxf86vm, libGLU, libGL, openal, libvorbis, sqlite, luajit
  , freetype, gettext, doxygen, ncurses, graphviz, xorg, gmp, libspatialindex
  , leveldb, postgresql, hiredis, libiconv, zlib, libXrandr, libX11, ninja, prometheus-cpp
  , OpenGL, OpenAL ? openal, Carbon, Cocoa, withTouchSupport ? false
  }:
  
  with lib;
  