port scan timeout to iOS

@@ -54,6 +54,12 @@ public class MobileScanner: NSObject, AVCaptureVideoDataOutputSampleBufferDelega
     private let backgroundQueue = DispatchQueue(label: "camera-handling")
 
     var standardZoomFactor: CGFloat = 1
+    
+    private var nextScanTime = 0.0
+    
+    private var imagesCurrentlyBeingProcessed = 0
+    
+    public var timeoutSeconds: Double = 0
 
     init(registry: FlutterTextureRegistry?, mobileScannerCallback: @escaping MobileScannerCallback, torchModeChangeCallback: @escaping TorchModeChangeCallback, zoomScaleChangeCallback: @escaping ZoomScaleChangeCallback) {
         self.registry = registry
@@ -89,8 +95,15 @@ public class MobileScanner: NSObject, AVCaptureVideoDataOutputSampleBufferDelega
         }
         latestBuffer = imageBuffer
         registry?.textureFrameAvailable(textureId)
-        if ((detectionSpeed == DetectionSpeed.normal || detectionSpeed == DetectionSpeed.noDuplicates) && i > 10 || detectionSpeed == DetectionSpeed.unrestricted) {
-            i = 0
+        
+        let currentTime = Date().timeIntervalSince1970
+        let eligibleForScan = currentTime > nextScanTime && imagesCurrentlyBeingProcessed == 0
+        
+        if ((detectionSpeed == DetectionSpeed.normal || detectionSpeed == DetectionSpeed.noDuplicates) && eligibleForScan || detectionSpeed == DetectionSpeed.unrestricted) {
+
+            nextScanTime = currentTime + timeoutSeconds
+            imagesCurrentlyBeingProcessed += 1
+            
             let ciImage = latestBuffer.image
 
             let image = VisionImage(image: ciImage)
@@ -101,6 +114,8 @@ public class MobileScanner: NSObject, AVCaptureVideoDataOutputSampleBufferDelega
             )
 
             scanner.process(image) { [self] barcodes, error in
+                imagesCurrentlyBeingProcessed -= 1
+                
                 if (detectionSpeed == DetectionSpeed.noDuplicates) {
                     let newScannedBarcodes = barcodes?.map { barcode in
                         return barcode.rawValue
@@ -114,8 +129,6 @@ public class MobileScanner: NSObject, AVCaptureVideoDataOutputSampleBufferDelega
 
                 mobileScannerCallback(barcodes, error, ciImage)
             }
-        } else {
-            i+=1
         }
     }
 
@@ -301,7 +314,7 @@ public class MobileScanner: NSObject, AVCaptureVideoDataOutputSampleBufferDelega
         
         do {
             try device.lockForConfiguration()
-            var maxZoomFactor = device.activeFormat.videoMaxZoomFactor
+            let maxZoomFactor = device.activeFormat.videoMaxZoomFactor
             
             var actualScale = (scale * 4) + 1
             
@@ -348,8 +361,6 @@ public class MobileScanner: NSObject, AVCaptureVideoDataOutputSampleBufferDelega
         scanner.process(image, completion: callback)
     }
 
-    var i = 0
-
     var barcodesString: Array<String?>?
 
 

@@ -12,8 +12,9 @@ public class SwiftMobileScannerPlugin: NSObject, FlutterPlugin {
     /// The handler sends all information via an event channel back to Flutter
     private let barcodeHandler: BarcodeHandler
 
+    /// The points for the scan window.
     static var scanWindow: [CGFloat]?
-    
+        
     private static func isBarcodeInScanWindow(barcode: Barcode, imageSize: CGSize) -> Bool {
         let scanwindow = SwiftMobileScannerPlugin.scanWindow!
         let barcodeminX = barcode.cornerPoints![0].cgPointValue.x
@@ -103,7 +104,9 @@ public class SwiftMobileScannerPlugin: NSObject, FlutterPlugin {
         let formats: Array<Int> = (call.arguments as! Dictionary<String, Any?>)["formats"] as? Array ?? []
         let returnImage: Bool = (call.arguments as! Dictionary<String, Any?>)["returnImage"] as? Bool ?? false
         let speed: Int = (call.arguments as! Dictionary<String, Any?>)["speed"] as? Int ?? 0
-
+        let timeoutMs: Int = (call.arguments as! Dictionary<String, Any?>)["timeout"] as? Int ?? 0
+        self.mobileScanner.timeoutSeconds = Double(timeoutMs / 1000)
+        
         let formatList = formats.map { format in return BarcodeFormat(rawValue: format)}
         var barcodeOptions: BarcodeScannerOptions? = nil
 
@@ -168,7 +171,7 @@ public class SwiftMobileScannerPlugin: NSObject, FlutterPlugin {
     
     /// Toggles the zoomScale
     private func setScale(_ call: FlutterMethodCall, _ result: @escaping FlutterResult) {
-        var scale = call.arguments as? CGFloat
+        let scale = call.arguments as? CGFloat
         if (scale == nil) {
             result(FlutterError(code: "MobileScanner",
                                               message: "You must provide a scale when calling setScale!",