$ show yudielcurbelo/react-qr-scanner
@yudiel/react-qr-scanner is a React library for scanning QR codes and barcodes using the device camera. It implements a layered hook architecture where `useCamera` manages low-level camera access and settings via a task queue pattern to prevent race conditions, `useScanner` implements the barcode detection loop using requestAnimationFrame with configurable timing and duplicate detection, and `useDevices` enumerates available video input devices. The main `Scanner` component orchestrates these hooks, handles coordinate transformation from video resolution to display space for accurate overlay rendering, and provides optional UI components for camera controls (torch, zoom, on/off). The library handles browser-specific quirks like the torch/zoom constraint conflict on mobile devices and provides robust error mapping for camera access issues.
The LLM identified 3 files worth highlighting for reuse:
A deep equality function that correctly handles React refs by ignoring the 'ref' key during comparison, preventing false positives when comparing props or constraints. It recursively compares primitives, dates, objects, and arrays, with special handling for Date objects by comparing time values. This utility is used to prevent unnecessary camera restarts when constraints haven't actually changed.
Maps DOMException and Error objects to a consistent IScannerError type with specific error kinds (permission-denied, no-camera, in-use, etc.). It detects special cases like secure context requirements and Stream API support through error message inspection, falling back to 'unknown' for unmapped errors. This provides normalized error handling across different browsers and environments.
Contains three tracking visualization functions for drawing on detected barcodes: outline (connects corner points), boundingBox (draws box around barcode), and centerText (displays rawValue with JSON-aware syntax highlighting). The centerText function features particularly sophisticated logic including JSON parsing, syntax coloring (blue for keys, green for values, black for punctuation), and LRU caching (32 entries) of parsed segments to avoid re-parsing the same values on each frame.