Add camera QR scanner to v2 client

Restores the old client's built-in scanner: a TopBar button opens a
camera modal (qr-scanner) that reads Spoolman label codes and opens the
matching spool in the Library. Parses both the WEB+SPOOLMAN:S-<id> URI
and the /spool/show/<id> URL forms.

Camera-start errors are reported specifically: an insecure (non-HTTPS)
context is detected up front via isSecureContext, and other failures are
re-probed via getUserMedia to recover the real error (permission
blocked, no camera, camera in use) since qr-scanner collapses them all
into a generic string.

client_v2/package-lock.json

@@ -9,6 +9,7 @@
       "version": "0.0.1",
       "dependencies": {
         "konva": "^10.3.0",
+        "qr-scanner": "^1.4.2",
         "qrcode": "^1.5.4",
         "svelte-konva": "^1.0.1"
       },
@@ -957,11 +958,16 @@
       "integrity": "sha512-nxAkRSVkN1Y0JC1W8ky/fTfkGsMmcrRsbx+3XoZE+rMOX71kLYTV7fLXpqud1GpbpP5TuffXFqfX7fH2GgZREw==",
       "dev": true,
       "license": "MIT",
-      "peer": true,
       "dependencies": {
         "undici-types": "~8.3.0"
       }
     },
+    "node_modules/@types/offscreencanvas": {
+      "version": "2019.7.3",
+      "resolved": "https://registry.npmjs.org/@types/offscreencanvas/-/offscreencanvas-2019.7.3.tgz",
+      "integrity": "sha512-ieXiYmgSRXUDeOntE1InxjWyvEelZGP63M+cGuquuRLuIKKT1osnkXjxev9B7d1nXSug5vpunx+gNlbVxMlC9A==",
+      "license": "MIT"
+    },
     "node_modules/@types/qrcode": {
       "version": "1.5.6",
       "resolved": "https://registry.npmjs.org/@types/qrcode/-/qrcode-1.5.6.tgz",
@@ -1518,6 +1524,15 @@
         "svelte": "^3.2.0 || ^4.0.0-next.0 || ^5.0.0-next.0"
       }
     },
+    "node_modules/qr-scanner": {
+      "version": "1.4.2",
+      "resolved": "https://registry.npmjs.org/qr-scanner/-/qr-scanner-1.4.2.tgz",
+      "integrity": "sha512-kV1yQUe2FENvn59tMZW6mOVfpq9mGxGf8l6+EGaXUOd4RBOLg7tRC83OrirM5AtDvZRpdjdlXURsHreAOSPOUw==",
+      "license": "MIT",
+      "dependencies": {
+        "@types/offscreencanvas": "^2019.6.4"
+      }
+    },
     "node_modules/qrcode": {
       "version": "1.5.4",
       "resolved": "https://registry.npmjs.org/qrcode/-/qrcode-1.5.4.tgz",

client_v2/package.json

@@ -26,6 +26,7 @@
   },
   "dependencies": {
     "konva": "^10.3.0",
+    "qr-scanner": "^1.4.2",
     "qrcode": "^1.5.4",
     "svelte-konva": "^1.0.1"
   }

client_v2/src/lib/components/QrScannerModal.svelte

@@ -0,0 +1,234 @@
+<script lang="ts">
+	import QrScanner from 'qr-scanner';
+	import { goto } from '$app/navigation';
+	import { base } from '$app/paths';
+	import { parseSpoolCode } from '$lib/utils/spoolCode';
+
+	interface Props {
+		open: boolean;
+		onclose?: () => void;
+	}
+	let { open, onclose }: Props = $props();
+
+	let video = $state<HTMLVideoElement | null>(null);
+	let error = $state<string | null>(null);
+	let starting = $state(false);
+
+	function close() {
+		onclose?.();
+	}
+
+	// A scanned code that decodes to a Spoolman spool id opens that spool in the
+	// Library. Non-Spoolman codes are ignored so the camera keeps scanning.
+	function onDecode(result: QrScanner.ScanResult) {
+		const id = parseSpoolCode(result.data);
+		if (id === null) return;
+		close();
+		goto(`${base}/?sel=spool:${id}`);
+	}
+
+	const MSG = {
+		insecure:
+			'The camera needs a secure connection. Browsers only allow camera access over HTTPS (or via localhost / 127.0.0.1) — open Spoolman that way to scan.',
+		unsupported: 'This browser does not provide camera access.',
+		denied:
+			'Camera access was blocked. Allow the camera permission for this site in your browser, then try again.',
+		notFound: 'No camera was found on this device.',
+		inUse: 'The camera is already in use by another application.',
+		generic: 'Could not start the camera.'
+	};
+
+	/** Map a getUserMedia DOMException to a friendly reason (by its `name`). */
+	function messageForError(err: unknown): string {
+		const name = (err as { name?: string } | null)?.name ?? '';
+		if (name === 'NotAllowedError' || name === 'SecurityError') return MSG.denied;
+		if (name === 'NotFoundError' || name === 'OverconstrainedError' || name === 'DevicesNotFoundError')
+			return MSG.notFound;
+		if (name === 'NotReadableError' || name === 'TrackStartError') return MSG.inUse;
+		return MSG.generic;
+	}
+
+	// qr-scanner collapses every getUserMedia failure into the opaque string
+	// "Camera not found.", so when start() rejects we re-request the camera
+	// ourselves to recover the real error name and report a specific reason.
+	async function classifyStartFailure(): Promise<string> {
+		try {
+			const stream = await navigator.mediaDevices.getUserMedia({ video: { facingMode: 'environment' } });
+			stream.getTracks().forEach((t) => t.stop());
+			return MSG.generic; // camera works now — the earlier failure was transient
+		} catch (err) {
+			return messageForError(err);
+		}
+	}
+
+	// Start the camera while the modal is open and tear it down on close/unmount.
+	// $effect re-runs when `open` (or the bound `video`) changes; its cleanup stops
+	// the stream so the camera light goes off the moment the modal closes.
+	$effect(() => {
+		if (!open || !video) return;
+
+		error = null;
+		starting = false;
+
+		// Insecure (non-HTTPS, non-localhost) origins don't expose the camera API
+		// at all — qr-scanner would only report a generic "camera not found", so
+		// detect this up front and tell the user the real reason before we try.
+		if (!window.isSecureContext || !navigator.mediaDevices?.getUserMedia) {
+			error = !window.isSecureContext ? MSG.insecure : MSG.unsupported;
+			return;
+		}
+
+		let scanner: QrScanner | null = null;
+		let cancelled = false;
+		starting = true;
+
+		scanner = new QrScanner(video, onDecode, {
+			// Prefer the rear camera; ignore frames that don't decode.
+			preferredCamera: 'environment',
+			highlightScanRegion: true,
+			highlightCodeOutline: true,
+			maxScansPerSecond: 5,
+			returnDetailedScanResult: true
+		});
+
+		scanner
+			.start()
+			.then(() => {
+				if (cancelled) scanner?.stop();
+			})
+			.catch(async (err) => {
+				if (cancelled) return;
+				console.error('QR scanner failed to start:', err);
+				error = await classifyStartFailure();
+			})
+			.finally(() => {
+				if (!cancelled) starting = false;
+			});
+
+		return () => {
+			cancelled = true;
+			scanner?.destroy();
+			scanner = null;
+		};
+	});
+</script>
+
+{#if open}
+	<div
+		class="overlay"
+		role="button"
+		tabindex="0"
+		onclick={close}
+		onkeydown={(e) => e.key === 'Escape' && close()}
+	>
+		<div
+			class="modal"
+			role="dialog"
+			aria-modal="true"
+			aria-label="Scan spool QR code"
+			tabindex="-1"
+			onclick={(e) => e.stopPropagation()}
+			onkeydown={(e) => e.stopPropagation()}
+		>
+			<div class="modal-head">
+				<span class="title">Scan a spool</span>
+				<button class="x" onclick={close} aria-label="Close">✕</button>
+			</div>
+
+			<p class="hint">Point your camera at a Spoolman QR code to open its spool.</p>
+
+			<div class="stage">
+				<!-- svelte-ignore a11y_media_has_caption -->
+				<video bind:this={video} playsinline></video>
+				{#if error}
+					<div class="msg error">{error}</div>
+				{:else if starting}
+					<div class="msg">Starting camera…</div>
+				{/if}
+			</div>
+		</div>
+	</div>
+{/if}
+
+<style>
+	.overlay {
+		position: fixed;
+		inset: 0;
+		background: rgba(0, 0, 0, 0.6);
+		z-index: 50;
+		display: flex;
+		align-items: flex-start;
+		justify-content: center;
+		padding: 8vh 16px 16px;
+	}
+	.modal {
+		width: 460px;
+		max-width: 100%;
+		display: flex;
+		flex-direction: column;
+		background: var(--bg);
+		border: 1px solid var(--border-strong);
+		border-radius: var(--radius-xl);
+		box-shadow: 0 20px 60px rgba(0, 0, 0, 0.6);
+		overflow: hidden;
+	}
+	.modal-head {
+		display: flex;
+		align-items: center;
+		gap: 10px;
+		padding: 16px 20px 0;
+		flex: none;
+	}
+	.title {
+		font-weight: 700;
+		font-size: 16px;
+	}
+	.x {
+		margin-left: auto;
+		color: var(--text-dim);
+		cursor: pointer;
+		font-size: 15px;
+		padding: 4px 8px;
+		background: none;
+		border: none;
+	}
+	.x:hover {
+		color: var(--text);
+	}
+	.hint {
+		padding: 8px 20px 0;
+		margin: 0;
+		font-size: 12.5px;
+		color: var(--text-muted);
+	}
+	.stage {
+		position: relative;
+		margin: 14px 20px 20px;
+		aspect-ratio: 1 / 1;
+		background: #000;
+		border-radius: var(--radius-md);
+		overflow: hidden;
+	}
+	.stage video {
+		width: 100%;
+		height: 100%;
+		object-fit: cover;
+		display: block;
+	}
+	.msg {
+		position: absolute;
+		inset: auto 12px 12px;
+		text-align: center;
+		font-size: 12.5px;
+		color: #fff;
+		background: rgba(0, 0, 0, 0.55);
+		padding: 8px 12px;
+		border-radius: var(--radius);
+	}
+	.msg.error {
+		inset: 12px;
+		display: flex;
+		align-items: center;
+		justify-content: center;
+	}
+</style>

client_v2/src/lib/components/TopBar.svelte

@@ -8,9 +8,10 @@
 
 	interface Props {
 		onadd?: () => void;
+		onscan?: () => void;
 	}
 
-	let { onadd }: Props = $props();
+	let { onadd, onscan }: Props = $props();
 
 	// The search box lives in the layout (above the routed page), so it reads the
 	// query straight from the URL and writes it back through the params helper.
@@ -22,6 +23,25 @@
 		<Logo />
 		<div class="nav-desktop"><NavTabs /></div>
 		<div class="spacer"></div>
+		<button class="scan-btn" onclick={onscan} aria-label="Scan spool QR code" title="Scan spool QR code">
+			<svg
+				viewBox="0 0 24 24"
+				width="18"
+				height="18"
+				fill="none"
+				stroke="currentColor"
+				stroke-width="2"
+				stroke-linecap="round"
+				stroke-linejoin="round"
+				aria-hidden="true"
+			>
+				<path d="M3 8V5a2 2 0 0 1 2-2h3" />
+				<path d="M21 8V5a2 2 0 0 0-2-2h-3" />
+				<path d="M3 16v3a2 2 0 0 0 2 2h3" />
+				<path d="M21 16v3a2 2 0 0 1-2 2h-3" />
+				<path d="M3 12h18" />
+			</svg>
+		</button>
 		<div class="search-desktop">
 			<SearchInput value={query} placeholder={'⌕ Search — try "red" or "pla"'} oninput={(v) => setQuery(v)} />
 		</div>
@@ -62,6 +82,23 @@
 	.spacer {
 		flex: 1;
 	}
+	.scan-btn {
+		flex: none;
+		display: inline-flex;
+		align-items: center;
+		justify-content: center;
+		width: 36px;
+		height: 36px;
+		border-radius: var(--radius-md);
+		border: 1px solid var(--border-strong);
+		background: none;
+		color: var(--text-2);
+		cursor: pointer;
+	}
+	.scan-btn:hover {
+		color: var(--text);
+		border-color: var(--accent);
+	}
 
 	.mobile-search,
 	.mobile-nav {

client_v2/src/lib/stores/ui.svelte.ts

@@ -9,6 +9,9 @@ class UiState {
 	addModalOpen = $state(false);
 	addModalFilamentId = $state<string | null>(null);
 
+	/** QR-code scanner modal (camera). */
+	scannerOpen = $state(false);
+
 	/** Open the Add-spools modal, optionally pre-seeded with a filament. */
 	openAddModal(filamentId?: string) {
 		this.addModalFilamentId = filamentId ?? null;
@@ -18,6 +21,13 @@ class UiState {
 		this.addModalOpen = false;
 		this.addModalFilamentId = null;
 	}
+
+	openScanner() {
+		this.scannerOpen = true;
+	}
+	closeScanner() {
+		this.scannerOpen = false;
+	}
 }
 
 export const ui = new UiState();

client_v2/src/lib/utils/spoolCode.ts

@@ -0,0 +1,19 @@
+// Parse the payload of a scanned Spoolman label back into a spool id. Mirrors
+// the two forms produced by the QR generator (lib/labels/qr.ts) and understood
+// by the old client's scanner (client/src/components/qrCodeScanner.tsx):
+//   scheme → WEB+SPOOLMAN:S-<id>            (compact custom URI)
+//   url    → <base_url>/spool/show/<id>     (opens in a browser)
+// Anything that isn't a Spoolman code returns null, so unrelated codes in view
+// are simply ignored.
+
+const SCHEME_RE = /^web\+spoolman:s-(?<id>[0-9]+)$/i;
+const URL_RE = /^https?:\/\/[^/]+(?:\/[^/]+)*\/spool\/show\/(?<id>[0-9]+)\/?$/i;
+
+/** Extract the spool id from a scanned code, or null if it isn't a Spoolman code. */
+export function parseSpoolCode(raw: string): number | null {
+	const text = raw.trim();
+	const match = SCHEME_RE.exec(text) ?? URL_RE.exec(text);
+	if (!match?.groups) return null;
+	const id = Number(match.groups.id);
+	return Number.isSafeInteger(id) ? id : null;
+}

client_v2/src/routes/+layout.svelte

@@ -3,6 +3,7 @@
 	import TopBar from '$components/TopBar.svelte';
 	import Footer from '$components/Footer.svelte';
 	import AddSpoolModal from '$components/AddSpoolModal.svelte';
+	import QrScannerModal from '$components/QrScannerModal.svelte';
 	import { ui } from '$lib/stores/ui.svelte';
 	import { settings } from '$lib/stores/settings.svelte';
 	import { startLiveSync } from '$lib/api/liveSync';
@@ -19,7 +20,7 @@
 </script>
 
 <div class="app">
-	<TopBar onadd={() => ui.openAddModal()} />
+	<TopBar onadd={() => ui.openAddModal()} onscan={() => ui.openScanner()} />
 	<main>
 		{@render children()}
 	</main>
@@ -32,6 +33,8 @@
 	onclose={() => ui.closeAddModal()}
 />
 
+<QrScannerModal open={ui.scannerOpen} onclose={() => ui.closeScanner()} />
+
 <style>
 	.app {
 		display: flex;