anchor.diff:      (enableFeature dvdnavSupport   "dvdnav")
       (enableFeature openalSupport   "openal")
       (enableFeature sdl2Support     "sdl2")
  +    (enableFeature sixelSupport    "sixel")
       (enableFeature vaapiSupport    "vaapi")
       (enableFeature waylandSupport  "wayland")
       (enableFeature stdenv.isLinux  "dvbin")
  
positive.code:   , mesa   ? null
  
  , alsaSupport        ? stdenv.isLinux, alsaLib       ? null
  , bluraySupport      ? true,           libbluray     ? null
  , bs2bSupport        ? true,           libbs2b       ? null
  , cacaSupport        ? true,           libcaca       ? null
  , cmsSupport         ? true,           lcms2         ? null
  , dvdnavSupport      ? stdenv.isLinux, libdvdnav     ? null
  , libpngSupport      ? true,           libpng        ? null
  , pulseSupport       ? config.pulseaudio or stdenv.isLinux, libpulseaudio ? null
  , rubberbandSupport  ? stdenv.isLinux, rubberband    ? null
  , screenSaverSupport ? true,           libXScrnSaver ? null
  , sdl2Support        ? true,           SDL2          ? null
  , speexSupport       ? true,           speex         ? null
  , swiftSupport       ? false,          swift         ? null
  , theoraSupport      ? true,           libtheora     ? null
  , vaapiSupport       ? stdenv.isLinux, libva         ? null
  , vdpauSupport       ? true,           libvdpau      ? null
  , xineramaSupport    ? stdenv.isLinux, libXinerama   ? null
  , xvSupport          ? stdenv.isLinux, libXv         ? null
  , zimgSupport        ? true,           zimg          ? null
  , archiveSupport     ? true,           libarchive    ? null
  , jackaudioSupport   ? false,          libjack2      ? null
  , openalSupport      ? true,           openalSoft    ? null
  , vapoursynthSupport ? false,          vapoursynth   ? null
  }:
  
  with stdenv.lib;
  
negative.code:     ++ optional rubberbandSupport  rubberband
      ++ optional screenSaverSupport libXScrnSaver
      ++ optional sdl2Support        SDL2
      ++ optional sixelSupport       libsixel
      ++ optional speexSupport       speex
      ++ optional theoraSupport      libtheora
      ++ optional vaapiSupport       libva
  