anchor.diff:  
       # TODO plugins
       # amodem
  -  ];
  +  ] ++ stdenv.lib.optionals enableQt [ pyqt5 qdarkstyle ];
   
     preBuild = ''
       sed -i 's,usr_share = .*,usr_share = "'$out'/share",g' setup.py
  -    sed -i "s|name = 'libzbar.*'|name='${zbar}/lib/libzbar.so'|" electrum/qrscanner.py
  -    substituteInPlace ./electrum/ecc_fast.py --replace libsecp256k1.so.0 ${secp256k1}/lib/libsecp256k1.so.0
  -  '';
  +    substituteInPlace ./electrum/ecc_fast.py \
  +      --replace ${libsecp256k1_name} ${secp256k1}/lib/libsecp256k1${stdenv.hostPlatform.extensions.sharedLibrary}
  +  '' + (if enableQt then ''
  +    substituteInPlace ./electrum/qrscanner.py \
  +      --replace ${libzbar_name} ${zbar}/lib/libzbar${stdenv.hostPlatform.extensions.sharedLibrary}
  +  '' else ''
  +    sed -i '/qdarkstyle/d' contrib/requirements/requirements.txt
  +  '');
   
  -  postInstall = ''
  +  postInstall = stdenv.lib.optionalString stdenv.isLinux ''
       # Despite setting usr_share above, these files are installed under
       # $out/nix ...
       mv $out/${python3.sitePackages}/nix/store"/"*/share $out
  
positive.code: { stdenv, fetchurl, fetchFromGitHub, python3, python3Packages, zbar, secp256k1
  
  
  # for updater.nix
  
negative.code:     protobuf
      pyaes
      pycryptodomex
      pysocks
      qrcode
      requests
      tlslite-ng
  