Moved calculateScanWindowRelativeToTextureInPercentage() into own file for unit tests

@@ -6,6 +6,7 @@ import 'package:mobile_scanner/src/mobile_scanner_controller.dart';
 import 'package:mobile_scanner/src/mobile_scanner_exception.dart';
 import 'package:mobile_scanner/src/objects/barcode_capture.dart';
 import 'package:mobile_scanner/src/objects/mobile_scanner_arguments.dart';
+import 'package:mobile_scanner/src/scan_window_calculation.dart';
 
 /// The function signature for the error builder.
 typedef MobileScannerErrorBuilder = Widget Function(
@@ -175,75 +176,6 @@ class _MobileScannerState extends State<MobileScanner>
     }
   }
 
-  /// the [scanWindow] rect will be relative and scaled to the [widgetSize] not the texture. so it is possible,
-  /// depending on the [fit], for the [scanWindow] to partially or not at all overlap the [textureSize]
-  ///
-  /// since when using a [BoxFit] the content will always be centered on its parent. we can convert the rect
-  /// to be relative to the texture.
-  ///
-  /// since the textures size and the actuall image (on the texture size) might not be the same, we also need to
-  /// calculate the scanWindow in terms of percentages of the texture, not pixels.
-  Rect calculateScanWindowRelativeToTextureInPercentage(
-    BoxFit fit,
-    Rect scanWindow,
-    Size textureSize,
-    Size widgetSize,
-  ) {
-    double fittedTextureWidth;
-    double fittedTextureHeight;
-
-    switch (fit) {
-      case BoxFit.contain:
-        final widthRatio = widgetSize.width / textureSize.width;
-        final heightRatio = widgetSize.height / textureSize.height;
-        final scale = widthRatio < heightRatio ? widthRatio : heightRatio;
-        fittedTextureWidth = textureSize.width * scale;
-        fittedTextureHeight = textureSize.height * scale;
-        break;
-
-      case BoxFit.cover:
-        final widthRatio = widgetSize.width / textureSize.width;
-        final heightRatio = widgetSize.height / textureSize.height;
-        final scale = widthRatio > heightRatio ? widthRatio : heightRatio;
-        fittedTextureWidth = textureSize.width * scale;
-        fittedTextureHeight = textureSize.height * scale;
-        break;
-
-      case BoxFit.fill:
-        fittedTextureWidth = widgetSize.width;
-        fittedTextureHeight = widgetSize.height;
-        break;
-
-      case BoxFit.fitHeight:
-        final ratio = widgetSize.height / textureSize.height;
-        fittedTextureWidth = textureSize.width * ratio;
-        fittedTextureHeight = widgetSize.height;
-        break;
-
-      case BoxFit.fitWidth:
-        final ratio = widgetSize.width / textureSize.width;
-        fittedTextureWidth = widgetSize.width;
-        fittedTextureHeight = textureSize.height * ratio;
-        break;
-
-      case BoxFit.none:
-      case BoxFit.scaleDown:
-        fittedTextureWidth = textureSize.width;
-        fittedTextureHeight = textureSize.height;
-        break;
-    }
-
-    final offsetX = (widgetSize.width - fittedTextureWidth) / 2;
-    final offsetY = (widgetSize.height - fittedTextureHeight) / 2;
-
-    final left = (scanWindow.left - offsetX) / fittedTextureWidth;
-    final top = (scanWindow.top - offsetY) / fittedTextureHeight;
-    final right = (scanWindow.right - offsetX) / fittedTextureWidth;
-    final bottom = (scanWindow.bottom - offsetY) / fittedTextureHeight;
-
-    return Rect.fromLTRB(left, top, right, bottom);
-  }
-
   Rect? scanWindow;
 
   @override

+import 'package:flutter/rendering.dart';
+
+/// the [scanWindow] rect will be relative and scaled to the [widgetSize] not the texture. so it is possible,
+/// depending on the [fit], for the [scanWindow] to partially or not at all overlap the [textureSize]
+///
+/// since when using a [BoxFit] the content will always be centered on its parent. we can convert the rect
+/// to be relative to the texture.
+///
+/// since the textures size and the actuall image (on the texture size) might not be the same, we also need to
+/// calculate the scanWindow in terms of percentages of the texture, not pixels.
+Rect calculateScanWindowRelativeToTextureInPercentage(
+  BoxFit fit,
+  Rect scanWindow,
+  Size textureSize,
+  Size widgetSize,
+) {
+  double fittedTextureWidth;
+  double fittedTextureHeight;
+
+  switch (fit) {
+    case BoxFit.contain:
+      final widthRatio = widgetSize.width / textureSize.width;
+      final heightRatio = widgetSize.height / textureSize.height;
+      final scale = widthRatio < heightRatio ? widthRatio : heightRatio;
+      fittedTextureWidth = textureSize.width * scale;
+      fittedTextureHeight = textureSize.height * scale;
+      break;
+
+    case BoxFit.cover:
+      final widthRatio = widgetSize.width / textureSize.width;
+      final heightRatio = widgetSize.height / textureSize.height;
+      final scale = widthRatio > heightRatio ? widthRatio : heightRatio;
+      fittedTextureWidth = textureSize.width * scale;
+      fittedTextureHeight = textureSize.height * scale;
+      break;
+
+    case BoxFit.fill:
+      fittedTextureWidth = widgetSize.width;
+      fittedTextureHeight = widgetSize.height;
+      break;
+
+    case BoxFit.fitHeight:
+      final ratio = widgetSize.height / textureSize.height;
+      fittedTextureWidth = textureSize.width * ratio;
+      fittedTextureHeight = widgetSize.height;
+      break;
+
+    case BoxFit.fitWidth:
+      final ratio = widgetSize.width / textureSize.width;
+      fittedTextureWidth = widgetSize.width;
+      fittedTextureHeight = textureSize.height * ratio;
+      break;
+
+    case BoxFit.none:
+    case BoxFit.scaleDown:
+      fittedTextureWidth = textureSize.width;
+      fittedTextureHeight = textureSize.height;
+      break;
+  }
+
+  final offsetX = (widgetSize.width - fittedTextureWidth) / 2;
+  final offsetY = (widgetSize.height - fittedTextureHeight) / 2;
+
+  final left = (scanWindow.left - offsetX) / fittedTextureWidth;
+  final top = (scanWindow.top - offsetY) / fittedTextureHeight;
+  final right = (scanWindow.right - offsetX) / fittedTextureWidth;
+  final bottom = (scanWindow.bottom - offsetY) / fittedTextureHeight;
+
+  return Rect.fromLTRB(left, top, right, bottom);
+}