metamask-extension/ui/components/app/qr-hardware-popover/enhanced-reader.js

import React, { useEffect, useMemo, useState } from 'react';
import { BarcodeFormat, DecodeHintType } from '@zxing/library';
import { BrowserQRCodeReader } from '@zxing/browser';
import log from 'loglevel';
import PropTypes from 'prop-types';
import { MILLISECOND } from '../../../../shared/constants/time';
import Spinner from '../../ui/spinner';

const EnhancedReader = ({ handleScan }) => {
  const [canplay, setCanplay] = useState(false);
  const codeReader = useMemo(() => {
    const hint = new Map();
    hint.set(DecodeHintType.POSSIBLE_FORMATS, [BarcodeFormat.QR_CODE]);
    return new BrowserQRCodeReader(hint, {
      delayBetweenScanAttempts: MILLISECOND * 100,
      delayBetweenScanSuccess: MILLISECOND * 100,
    });
  }, []);

  useEffect(() => {
    const videoElem = document.getElementById('video');
    const canplayListener = () => {
      setCanplay(true);
    };
    videoElem.addEventListener('canplay', canplayListener);
    const promise = codeReader.decodeFromVideoDevice(
      undefined,
      'video',
      (result) => {
        if (result) {
          handleScan(result.getText());
        }
      },
    );
    return () => {
      videoElem.removeEventListener('canplay', canplayListener);
      promise
        .then((controls) => {
          if (controls) {
            controls.stop();
          }
        })
        .catch(log.info);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  return (
    <div className="qr-scanner__content__video-wrapper">
      <video
        id="video"
        style={{
          display: canplay ? 'block' : 'none',
          width: '100%',
          filter: 'blur(4px)',
        }}
      />
      {canplay ? null : <Spinner color="var(--color-warning-default)" />}
    </div>
  );
};

EnhancedReader.propTypes = {
  handleScan: PropTypes.func.isRequired,
};

export default EnhancedReader;