fix(frontend): Improve QR scanning reliability for dark borderless codes#12162
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Pull request overview
This PR replaces the existing QR scanning implementation (previously sourced from @dfinity/gix-components / html5-qrcode) with a locally vendored QRCodeReader that uses the barcode-detector ponyfill (ZXing WASM) to improve scanning reliability for inverted/dark borderless QR codes, especially on mobile.
Changes:
- Added a new local
QRCodeReader.sveltethat usesgetUserMedia+barcode-detector/ponyfillto decode QR codes from a<video>stream. - Updated WalletConnect and general QR scanning flows to use the local
QRCodeReaderinstead of@dfinity/gix-components. - Added a small
nextElementIdutility and introducedbarcode-detectoras a dependency.
Reviewed changes
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Show a summary per file
| File | Description |
|---|---|
| src/frontend/src/lib/utils/html.utils.ts | Adds an element-id helper used by the new QR code reader. |
| src/frontend/src/lib/components/wallet-connect/WalletConnectForm.svelte | Switches to the local QR code reader component. |
| src/frontend/src/lib/components/ui/QRCodeReader.svelte | New QR scanning component using getUserMedia + barcode-detector ponyfill. |
| src/frontend/src/lib/components/qr/QrCodeScanner.svelte | Switches to the local QR code reader component. |
| package.json | Adds barcode-detector dependency. |
| package-lock.json | Lockfile updates for the new dependency tree. |
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DenysKarmazynDFINITY
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# Motivation To use the new library from `QrCodeReader` component (PR #12162) we need to allow it in the CSP.
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Note
This PR is a fork of dfinity/gix-components#759.
Awaiting that review, we simply copy the components in our repo and add it to the next release, since it is a time-sensitive issue.
Motivation
The QR code reader was using
html5-qrcode, which has a known issue with inverted (dark-themed, borderless) QR codes on mobile — they simply cannot be scanned. The library is also unmaintained.Known upstream issues:
Since the root cause is a limitation of
html5-qrcodeitself (no support for inverted QR codes), and the library is no longer maintained, this PR replaces it withbarcode-detector— a Barcode Detection API polyfill powered by ZXing C++ WebAssembly under the hood. The underlying engine natively supports inverted code detection (tryInvertis enabled by default). We tested it manually on a mobile device and dark borderless QR codes are now successfully scanned.Thanks to @sea-snake for the tip!
Changes (copied from gix-components's
QRCodeReader)html5-qrcodedependency entirely in componentQRCodeReader.QRCodeReader:navigator.mediaDevices.getUserMediaAPI, requesting the rear-facing camera (facingMode: "environment") at up to 1920×1080 resolution.<video>element.BarcodeDetectorAPI (viabarcode-detector/ponyfill). A detector instance is created withformats: ["qr_code"]anddetector.detect(videoElement)is called at ~10 fps viasetInterval(scan, 100). The polyfill accepts the<video>element directly — no intermediate<canvas>needed.isProcessingFrame) prevents overlapping decode calls..scan-overlaycontainer with a.scan-regionbox usingbox-shadowto mask the surrounding area and a border styled with the primary color. This replaces the old:global(#qr-shaded-region)overrides that targetedhtml5-qrcode's internal DOM.jsQRtobarcode-detector.barcode-detector@^3.1.1to dependencies and removedhtml5-qrcode.Tests
Manual testing on mobile: dark borderless QR codes are now successfully scanned (this was the main validation, as the core issue only reproduced on real mobile devices).