anchor.diff:  with stdenv.lib;
   stdenv.mkDerivation rec {
     pname = "libass";
  -  version = "0.14.0";
  +  version = "0.15.0";
   
     src = fetchurl {
       url = "https://github.com/libass/libass/releases/download/${version}/${pname}-${version}.tar.xz";
  -    sha256 = "18iqznl4mabhj9ywfsz4kwvbsplcv1jjxq50nxssvbj8my1267w8";
  +    sha256 = "0cz8v6kh3f2j5rdjrra2z0h715fa16vjm7kambvqx9hak86262cz";
     };
   
     configureFlags = [
       (mkFlag encaSupport "enca")
       (mkFlag fontconfigSupport "fontconfig")
  -    (mkFlag harfbuzzSupport "harfbuzz")
       (mkFlag rasterizerSupport "rasterizer")
       (mkFlag largeTilesSupport "large-tiles")
     ];
   
     nativeBuildInputs = [ pkgconfig yasm ];
   
  -  buildInputs = [ freetype fribidi ]
  +  buildInputs = [ freetype fribidi harfbuzz ]
       ++ optional encaSupport enca
       ++ optional fontconfigSupport fontconfig
  -    ++ optional harfbuzzSupport harfbuzz
       ++ optional stdenv.isDarwin libiconv;
   
     meta = {
  
positive.code: { stdenv, fetchurl, pkgconfig, yasm
  , freetype, fribidi
  , encaSupport ? true, enca ? null # enca support
  , fontconfigSupport ? true, fontconfig ? null # fontconfig support
  , harfbuzzSupport ? true, harfbuzz ? null # harfbuzz support
  , rasterizerSupport ? false # Internal rasterizer
  , largeTilesSupport ? false # Use larger tiles in the rasterizer
  , libiconv
  
negative.code: 
  assert encaSupport -> enca != null;
  assert fontconfigSupport -> fontconfig != null;
  
  let
    mkFlag = optSet: flag: if optSet then "--enable-${flag}" else "--disable-${flag}";
  