I built a barcode scanning system using Chrome's built-in BarcodeDetector
. I based the work on Paul Kinlan's QR code scanner which works fine on my phone, but when I run my own code on my phone, it often causes Chrome or the whole System UI to freeze. Sometimes it gets so bad that I need to restart the phone by holding down the power button.
I have tried debugging in the Chrome developer console, but when the phone freezes, so does the developer console.
When I comment out the actual QR code detection, I can leave the page open in Chrome for 10 minutes and it just keeps running. With QR code detection running, the phone will freeze anywhere from immediately to 3 minutes later.
I put the support files (js and HTML) in a Gist - I don't think they are the issue because everything works when the barcode scanning is commented out.
My first attempt:
// Inspired by/based on on https://github.com/PaulKinlan/qrcode/blob/production/app/scripts/main.mjs
import WebCamManager from './scan/WebCamManager.js';
(function () {
'use strict';
var QRCodeCamera = function (element) {
var root = document.getElementById(element);
var cameraRoot = root.querySelector('.CameraRealtime');
var cameraManager = new WebCamManager(cameraRoot);
var cameraVideo = root.querySelector('.Camera-video');
// Offscreen canvas is supposed to help with processing speed
var cameraCanvas = new OffscreenCanvas(1,1);
var context = cameraCanvas.getContext('2d');
const detector = new BarcodeDetector({
formats: ['qr_code'],
});
cameraManager.onframeready = async function (frameData) {
cameraCanvas.width = cameraVideo.videoWidth;
cameraCanvas.height = cameraVideo.videoHeight;
context.drawImage(frameData, 0, 0, cameraVideo.videoWidth, cameraVideo.videoHeight);
if (self.onframe) {
// Comment out the line below to stop processing QR codes
await self.onframe(cameraCanvas);
}
};
var processingFrame = false;
self.onframe = async function (cameraCanvas) {
// There is a frame in the camera, what should we do with it?
if (processingFrame == false) {
processingFrame = true;
let result = await detector.detect(cameraCanvas);
processingFrame = false;
if (result === undefined || result === null || result.length === 0) {
return
};
if ('vibrate' in navigator) {
navigator.vibrate([200]);
}
cameraManager.stop();
var currentURL = new URL(window.location.href);
var newURL;
if (result[0].rawValue
&& (newURL = new URL(result[0].rawValue))
&& newURL.hostname == currentURL.hostname
&& newURL.pathname.startsWith('/pickup/qr/')
) {
window.location.href = newURL;
} else {
alert('Unsupported QR Code: ' + result[0].rawValue);
}
cameraManager.start();
}
};
};
window.addEventListener('load', function () {
var camera = new QRCodeCamera('camera');
});
})();
I also tried splitting the QR detection to a worker (worker code in Gist), but I have the same issue:
const worker = new Worker('/js/scan-worker.js');
worker.addEventListener('message', async (e) => {
if (Array.isArray(e.data)) {
var result = e.data;
if (result === undefined || result === null || result.length === 0) {
processingFrame = false;
return
};
if ('vibrate' in navigator) {
navigator.vibrate([200]);
}
var currentURL = new URL(window.location.href);
var newURL;
if (result[0].rawValue
&& (newURL = new URL(result[0].rawValue))
&& newURL.hostname == currentURL.hostname
&& newURL.pathname.startsWith('/pickup/qr/')
) {
worker.terminate();
window.location.href = newURL;
} else {
alert('Unsupported QR Code: ' + result[0].rawValue);
}
} else {
var newError = document.createElement('div');
newError.classList.add('alert', 'alert-danger');
newError.innerHTML = e.data;
errorContainer.prepend(newError);
worker.terminate();
}
processingFrame = false;
});
cameraManager.onframeready = async function (frameData) {
if (processingFrame == false) {
cameraCanvas.width = cameraVideo.videoWidth;
cameraCanvas.height = cameraVideo.videoHeight;
context.drawImage(frameData, 0, 0, cameraVideo.videoWidth, cameraVideo.videoHeight);
if (self.onframe) {
await self.onframe(cameraCanvas, context);
}
}
};
self.onframe = async function (cameraCanvas, context) {
// There is a frame in the camera, what should we do with it?
if (processingFrame == false) {
processingFrame = true;
worker.postMessage(context.getImageData(0, 0, cameraCanvas.width, cameraCanvas.height));
}
};
Not sure if this would make a difference - all the JS code is run through Laravel Mix.
from Why does this barcode detection cause Chrome or the whole Android OS to crash?
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