anchor.diff:      demo.value = input.value;
     });
   
  -  demo.updated.listen((args) {
  +  demo.output.listen((data) {
       input.style.background = '';
  -  });
  -
  -  demo.error.listen((args) {
  +  }, onError: (error) {
       input.style.background = 'red';
     });
   }
  
positive.code:   }
  }
  
  class _QrCalc
    extends SendPortValue<List, List<bool>> {
    _QrCalc() : super(spawnFunction(_qrIsolate));
  }
  
  void _qrIsolate() {
  
    new SendValuePort<List, List<bool>>((input) {
      final code = new QrCode(input[0], input[1]);
      code.addData(input[2]);
      code.make();
  
      final List<bool> squares = new List<bool>();
  
      for(int x = 0; x < code.moduleCount; x++) {
        for(int y = 0; y < code.moduleCount; y++) {
          squares.add(code.isDark(y, x));
        }
      }
  
      return squares;
    });
  }
  
negative.code:     }
    }
  
    Stream get output => _qrMapper.outputStream;
  
    String get value => _value;
  
  