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, with the black Goblin logo centred in the code. The screen’s Share and Copy actions hand over the same nprofile string. 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 plain nostr:<nprofile> code fills only the recipient; a pay-URI code (for example a GoblinPay checkout QR, nostr:<nprofile>?amount=…&memo=…) also fills the amount and note, so scanning a checkout needs no retyping. Prefilling is all scanning does: the amount and review screens still confirm the send.
• 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).