Fix UX-015: ZXing async callback silently swallows camera errors - add handleCameraError(), 5s cameraFailTimer, error branch in decodeFromVideoDevice callback

static/index.html

@@ -2893,20 +2893,48 @@
 
         setScanStatus('Point camera at a barcode', 'success');
 
+        // Camera readiness check: if the video never starts streaming
+        // (no media attached within 5s), treat as camera failure
+        const cameraFailTimer = setTimeout(() => {
+          if (video.readyState === 0 && scanningActive) {
+            console.warn('Camera stream never started — showing manual fallback');
+            scanningActive = false;
+            video.style.display = 'none';
+            if (codeReader) {
+              try { codeReader.reset(); } catch (e) { /* ignore */ }
+            }
+            handleCameraError(new Error('No camera stream — connect a camera or enter ID manually'));
+          }
+        }, 5000);
+
         // decodeFromVideoDevice handles camera + scanning in one call
         codeReader.decodeFromVideoDevice(deviceId, video, (result, err) => {
+          // Clear the timeout once we get any callback (stream started or error)
+          clearTimeout(cameraFailTimer);
           if (result && scanningActive) {
             const val = result.getText();
             if (val && val !== currentScannedMachineId) {
               handleBarcode(val.trim());
             }
+          } else if (err && scanningActive) {
+            // ZXing reports camera errors through the callback (not as exceptions)
+            console.error('ZXing camera error:', err);
+            handleCameraError(new Error(err.message || err));
           }
         });
       } catch (e) {
         console.error('Camera error:', e);
+        handleCameraError(e);
+      }
+    }
+
+    function handleCameraError(e) {
       setScanStatus('Camera failed: ' + e.message, 'error');
       const ph = document.getElementById('cameraPlaceholder');
-        if (ph) ph.innerHTML = `<span class="cam-icon">${gi("📷")}</span><div class="cam-hint" style="margin-top:4px;">Camera: ${e.message}</div>`;
+      if (ph) {
+        ph.style.display = 'block';
+        ph.innerHTML = `<span class="cam-icon">${gi("📷")}</span><div class="cam-hint" style="margin-top:4px;">Camera: ${e.message}</div>`;
+      }
       // Show manual search fallback
       const fallback = document.getElementById('manualSearchFallback');
       if (fallback) {
@@ -2921,7 +2949,8 @@
           <button class="btn btn-primary btn-sm" onclick="handleManualBarcode()" style="margin-top:6px;width:100%;">Search</button>
           <button class="btn btn-outline btn-sm" onclick="startScanning()" style="margin-top:6px;width:100%;">Try camera again</button>
         `;
-        }
+        // Focus the manual input for convenience
+        setTimeout(() => document.getElementById('manualBarcodeInput')?.focus(), 100);
       }
     }