🐛 [Bug] QR code generation blocks the UI thread — causes stutter on rapid reconnects

[PranavAgarkar07]

The Problem

Every time the server URL changes (new connection, IP change, sender starts), BeamSync generates a QR code. QR generation creates a 220×220 PNG with error correction — all on the main JavaScript thread. This blocks the UI for 10-30ms per generation. 📱

During network flapping (VPN switching, unstable Wi-Fi), multiple generations queue up and the UI becomes noticeably janky.

Where to Look

• desktop/frontend/src/App.svelte — generateQR() at line 508. The QRCode.toDataURL() call is synchronous and CPU-intensive.
• Consider debouncing (don't regenerate if called again within 100ms) or offloading to a microtask.

The Goal

• QR generation should not block the UI
• Debounce rapid URL changes so only the last one triggers a QR regen
• Test: rapidly change the server URL 10 times — UI should stay responsive throughout

[mittalsonal]

Hi maintainer, I verified desktop/frontend/src/App.svelte still calls QRCode.toDataURL immediately in generateQR() whenever the URL changes. Please assign this to me for GSSoC. I can debounce rapid URL changes, guard against stale callback results, and keep the visible QR behavior unchanged while preventing repeated synchronous generations during reconnect churn.