anchor.diff:      gnutls
       gtk
       libgcrypt
  +    libice
       libjpeg
       libnotify
       libsecret
  +    libsm
       libsoup
  +    libx11
  +    libxext
  +    libxtst
       telepathy_glib
  +    xorgproto
       zlib
  -  ] ++ optionals (xorg != null) [
  -    xorg.libICE
  -    xorg.libSM
  -    xorg.libX11
  -    xorg.libXext
  -    xorg.libXtst
  -    xorg.xproto
     ];
   
     configureFlags = [
  
positive.code: , gnutls
  , gtk
  , libgcrypt
  , libjpeg
  , libnotify
  , libsecret
  , libsoup
  , telepathy_glib
  , xorg
  , zlib
  
  , channel
  }:
  
  assert xorg != null ->
    xorg.libICE != null
    && xorg.libSM != null
    && xorg.libX11 != null
    && xorg.libXext != null
    && xorg.libXtst != null
    && xorg.xproto != null;
  
  let
    inherit (stdenv.lib)
  
negative.code:     "--enable-schemas-compile"
      "--${boolWt (telepathy_glib != null)}-telepathy"
      "--${boolWt (libsecret != null)}-secret"
      "--${boolWt (libxll != null)}-x"
      "--${boolWt (gnutls != null)}-gnutls"
      "--${boolWt (libgcrypt != null)}-gcrypt"
      "--${boolWt (avahi != null)}-avahi"
  