QR code / barcode scanner — a Mob plugin (extracted from mob core in Wave 3).

Opens a full-screen camera preview. When a code is detected the view dismisses automatically and the result is delivered to handle_info. A scan/2 ends in one of:

handle_info({:scan, :result, %{type: :qr, value: "https://..."}}, socket)
handle_info({:scan, :cancelled}, socket)
handle_info({:scan, :permission_denied}, socket)
handle_info({:scan, :not_available}, socket)

• :cancelled — the scanner closed without a code (the user cancelled; on Android also when no host Activity is attached or CameraX can't bind the camera).
• :permission_denied — camera access is denied/restricted, or the user refused the prompt. Nothing is presented; send the user to Settings.
• :not_available — the scanner could not open: iOS found no camera input; Android could not launch MobScannerActivity, or the host Activity was finishing/destroyed/replaced by launch time (the cause is logged to logcat under the MobScanner tag).

Requires the mob_camera plugin for the :camera permission. The :camera runtime-permission capability (its registry handler on iOS and the MobPermissionProvider mapping on Android) is owned by mob_camera — activate mob_camera alongside this plugin and request :camera via Mob.Permissions.request/2 before calling scan/2. mob_camera's manifest also carries the iOS NSCameraUsageDescription plist key. If :camera is still undecided when scan/2 runs, the scanner shows the system prompt itself and opens once it is granted.

iOS: AVCaptureMetadataOutput. Android: CameraX + ML Kit BarcodeScanning in a plugin-owned full-screen Activity (io.mob.scanner.MobScannerActivity), declared in the host manifest by the native build from this plugin's manifest.

When the native side refuses a call

scan/2 keeps returning the socket. When the native side refuses the call (on Android, {:error, :bridge_not_registered} when MobScannerBridge never registered), it logs a warning naming the function and the reason, and no {:scan, …} message follows. mix mob.selftest reports an unregistered bridge before you get that far.