QR & camera

Summary. Goblin reads and writes QR codes for the things you hand to another person face-to-face: your payment code (nprofile), and your recovery phrase (SeedQR). The camera path decodes standard and animated (multi-frame) QR codes across platforms.

Motivation

In person, a QR is the fastest “address exchange” there is, and for a recovery phrase, scanning beats re-typing 24 words. Goblin uses QR in two directions: show your code so someone can scan-to-pay you, and scan a code to fill a recipient or import a seed. The scanner deliberately refuses to echo sensitive scans (seeds, raw slatepacks) into the UI.

How it works

• Showing. The Receive screen and “My Code” tab render your nprofile (npub + relay hints) as a QR so a payer can scan it and reach you with no lookup. Long payloads use animated Uniform Resources (UR): a sequence of frames.
• Scanning. The camera feed is decoded with rqrr; the recipient row and home header offer a scanner for scan-to-pay, and onboarding offers a SeedQR scan to import a phrase. Only text QR results are accepted into the recipient field; a nostr: prefix is stripped before resolving.
• Cross-platform camera. Backed by nokhwa (V4L on Linux, MSMF on Windows, AVFoundation on macOS). Frames that arrive as raw YUYV are decoded before QR scanning; a “No camera found” state appears if nothing opens.

Reference

• goblin/src/gui/views/camera.rs: CameraContent, the nokhwa capture + rqrr decode, UR reassembly, the unavailable-camera timeout.
• goblin/src/gui/views/qr.rs: QrCodeContent generation (qrcodegen), animated UR output.
• Scan entry points + accepted payloads: goblin/src/gui/views/goblin/send.rs (scan, ScanTab).

References

• The codes it shows: Send & request, Identity (nprofile).