imp: add zoomScaleState value notifier.

@@ -138,6 +138,7 @@ class MobileScanner(
         torch: Boolean,
         detectionSpeed: DetectionSpeed,
         torchStateCallback: TorchStateCallback,
+        zoomScaleStateCallback: ZoomScaleStateCallback,
         mobileScannerStartedCallback: MobileScannerStartedCallback,
         detectionTimeout: Long
     ) {
@@ -201,6 +202,11 @@ class MobileScanner(
                 torchStateCallback(state)
             }
 
+            // Register the zoom scale listener
+            camera!!.cameraInfo.zoomState.observe(activity) { state ->
+                zoomScaleStateCallback(state.linearZoom.toDouble())
+            }
+
 
             // Enable torch if provided
             camera!!.cameraControl.enableTorch(torch)

@@ -6,4 +6,5 @@ typealias MobileScannerCallback = (barcodes: List<Map<String, Any?>>, image: Byt
 typealias AnalyzerCallback = (barcodes: List<Map<String, Any?>>?) -> Unit
 typealias MobileScannerErrorCallback = (error: String) -> Unit
 typealias TorchStateCallback = (state: Int) -> Unit
+typealias ZoomScaleStateCallback = (zoomScale: Double) -> Unit
 typealias MobileScannerStartedCallback = (parameters: MobileScannerStartParameters) -> Unit
\ No newline at end of file

@@ -70,6 +70,11 @@ class MobileScannerHandler(
         barcodeHandler.publishEvent(mapOf("name" to "torchState", "data" to state))
     }
 
+    private val zoomScaleStateCallback: ZoomScaleStateCallback = {zoomScale: Double ->
+        barcodeHandler.publishEvent(mapOf("name" to "zoomScaleState", "data" to zoomScale))
+    }
+
+
     init {
         methodChannel = MethodChannel(binaryMessenger,
             "dev.steenbakker.mobile_scanner/scanner/method")
@@ -152,7 +157,7 @@ class MobileScannerHandler(
         val detectionSpeed: DetectionSpeed = DetectionSpeed.values().first { it.intValue == speed}
 
         try {
-            mobileScanner!!.start(barcodeScannerOptions, returnImage, position, torch, detectionSpeed, torchStateCallback, mobileScannerStartedCallback = {
+            mobileScanner!!.start(barcodeScannerOptions, returnImage, position, torch, detectionSpeed, torchStateCallback, zoomScaleStateCallback, mobileScannerStartedCallback = {
                 result.success(mapOf(
                     "textureId" to it.id,
                     "size" to mapOf("width" to it.width, "height" to it.height),

@@ -13,6 +13,7 @@ import MLKitBarcodeScanning
 
 typealias MobileScannerCallback = ((Array<Barcode>?, Error?, UIImage) -> ())
 typealias TorchModeChangeCallback = ((Int?) -> ())
+typealias ZoomScaleChangeCallback = ((Double?) -> ())
 
 public class MobileScanner: NSObject, AVCaptureVideoDataOutputSampleBufferDelegate, FlutterTexture {
     /// Capture session of the camera
@@ -36,6 +37,10 @@ public class MobileScanner: NSObject, AVCaptureVideoDataOutputSampleBufferDelega
     /// When torch mode is changes, this callback will be called
     let torchModeChangeCallback: TorchModeChangeCallback
 
+    /// When zoom scale is changes, this callback will be called
+    let zoomScaleChangeCallback: ZoomScaleChangeCallback
+
+
     /// If provided, the Flutter registry will be used to send the output of the CaptureOutput to a Flutter texture.
     private let registry: FlutterTextureRegistry?
 
@@ -47,10 +52,11 @@ public class MobileScanner: NSObject, AVCaptureVideoDataOutputSampleBufferDelega
 
     var detectionSpeed: DetectionSpeed = DetectionSpeed.noDuplicates
 
-    init(registry: FlutterTextureRegistry?, mobileScannerCallback: @escaping MobileScannerCallback, torchModeChangeCallback: @escaping TorchModeChangeCallback) {
+    init(registry: FlutterTextureRegistry?, mobileScannerCallback: @escaping MobileScannerCallback, torchModeChangeCallback: @escaping TorchModeChangeCallback, zoomScaleChangeCallback: @escaping ZoomScaleChangeCallback) {
         self.registry = registry
         self.mobileScannerCallback = mobileScannerCallback
         self.torchModeChangeCallback = torchModeChangeCallback
+        self.zoomScaleChangeCallback = zoomScaleChangeCallback
         super.init()
     }
 
@@ -133,6 +139,7 @@ public class MobileScanner: NSObject, AVCaptureVideoDataOutputSampleBufferDelega
         }
 
         device.addObserver(self, forKeyPath: #keyPath(AVCaptureDevice.torchMode), options: .new, context: nil)
+        device.addObserver(self, forKeyPath: #keyPath(AVCaptureDevice.videoZoomFactor), options: .new, context: nil)
         do {
             try device.lockForConfiguration()
             if device.isFocusModeSupported(.continuousAutoFocus) {
@@ -199,6 +206,7 @@ public class MobileScanner: NSObject, AVCaptureVideoDataOutputSampleBufferDelega
             captureSession.removeOutput(output)
         }
         device.removeObserver(self, forKeyPath: #keyPath(AVCaptureDevice.torchMode))
+        device.removeObserver(self, forKeyPath: #keyPath(AVCaptureDevice.videoZoomFactor))
         registry?.unregisterTexture(textureId)
         textureId = nil
         captureSession = nil
@@ -228,6 +236,10 @@ public class MobileScanner: NSObject, AVCaptureVideoDataOutputSampleBufferDelega
             // off = 0; on = 1; auto = 2;
             let state = change?[.newKey] as? Int
             torchModeChangeCallback(state)
+        case "videoZoomFactor":
+            let zoomFactor = change?[.newKey] as? CGFloat ?? 1
+            let zoomScale = (zoomFactor - 1) / 4
+            zoomScaleChangeCallback(Double(zoomScale))
         default:
             break
         }

@@ -57,6 +57,8 @@ public class SwiftMobileScannerPlugin: NSObject, FlutterPlugin {
             }
         }, torchModeChangeCallback: { torchState in
             barcodeHandler.publishEvent(["name": "torchState", "data": torchState])
+        }, zoomScaleChangeCallback: { zoomScale in
+            barcodeHandler.publishEvent(["name": "zoomScaleState", "data": zoomScale])
         })
         self.barcodeHandler = barcodeHandler
         super.init()

@@ -85,6 +85,10 @@ class MobileScannerController {
   late final ValueNotifier<CameraFacing> cameraFacingState =
       ValueNotifier(facing);
 
+  /// A notifier that provides zoomScale.
+  final ValueNotifier<double> zoomScaleState = ValueNotifier(0.0);
+
+
   bool isStarting = false;
 
   /// A notifier that provides availability of the Torch (Flash)
@@ -337,6 +341,9 @@ class MobileScannerController {
         final state = TorchState.values[data as int? ?? 0];
         torchState.value = state;
         break;
+      case 'zoomScaleState':
+        zoomScaleState.value = data as double? ?? 0.0;
+        break;
       case 'barcode':
         if (data == null) return;
         final parsed = (data as List)