add support for border radius & border styling to scan window painter

Author: navaronbracke

lib/src/overlay/scan_window_painter.dart

@@ -4,10 +4,34 @@ import 'package:flutter/material.dart';
 class ScanWindowPainter extends CustomPainter {
   /// Construct a new [ScanWindowPainter] instance.
   const ScanWindowPainter({
+    required this.borderColor,
+    required this.borderRadius,
+    required this.borderStrokeCap,
+    required this.borderStrokeJoin,
+    required this.borderStyle,
+    required this.borderWidth,
     required this.color,
     required this.scanWindow,
   });
 
+  /// The color for the scan window border.
+  final Color borderColor;
+
+  /// The border radius for the scan window and its border.
+  final BorderRadius borderRadius;
+
+  /// The stroke cap for the border around the scan window.
+  final StrokeCap borderStrokeCap;
+
+  /// The stroke join for the border around the scan window.
+  final StrokeJoin borderStrokeJoin;
+
+  /// The style for the border around the scan window.
+  final PaintingStyle borderStyle;
+
+  /// The width for the border around the scan window.
+  final double borderWidth;
+
   /// The color for the scan window box.
   final Color color;
 
@@ -20,22 +44,53 @@ class ScanWindowPainter extends CustomPainter {
       return;
     }
 
-    // Define the main overlay path covering the entire screen
+    // Define the main overlay path covering the entire screen.
     final backgroundPath = Path()..addRect(Offset.zero & size);
 
-    // Define the cutout path in the center
-    final cutoutPath = Path()..addRect(scanWindow);
+    // The cutout rect depends on the border radius.
+    final RRect cutoutRect = borderRadius == BorderRadius.zero
+        ? RRect.fromRectAndCorners(scanWindow)
+        : RRect.fromRectAndCorners(
+            scanWindow,
+            topLeft: borderRadius.topLeft,
+            topRight: borderRadius.topRight,
+            bottomLeft: borderRadius.bottomLeft,
+            bottomRight: borderRadius.bottomRight,
+          );
+
+    // The cutout path is always in the center.
+    final Path cutoutPath = Path()..addRRect(cutoutRect);
 
     // Combine the two paths: overlay minus the cutout area
-    final overlayWithCutoutPath = Path.combine(PathOperation.difference, backgroundPath, cutoutPath);
+    final Path overlayWithCutoutPath = Path.combine(
+      PathOperation.difference,
+      backgroundPath,
+      cutoutPath,
+    );
+
+    final Paint overlayWithCutoutPaint = Paint()
+      ..color = color
+      ..style = PaintingStyle.fill
+      ..blendMode = BlendMode.dstOver;
+
+    final Paint borderPaint = Paint()
+      ..color = borderColor
+      ..style = borderStyle
+      ..strokeWidth = borderWidth
+      ..strokeCap = borderStrokeCap
+      ..strokeJoin = borderStrokeJoin;
+
+    // Paint the overlay with the cutout.
+    canvas.drawPath(overlayWithCutoutPath, overlayWithCutoutPaint);
 
-    // Paint the overlay with the cutout
-    final paint = Paint()..color = color;
-    canvas.drawPath(overlayWithCutoutPath, paint);
+    // Then, draw the border around the cutout area.
+    canvas.drawRRect(cutoutRect, borderPaint);
   }
 
   @override
   bool shouldRepaint(ScanWindowPainter oldDelegate) {
-    return oldDelegate.scanWindow != scanWindow || oldDelegate.color != color;
+    return oldDelegate.scanWindow != scanWindow ||
+        oldDelegate.color != color ||
+        oldDelegate.borderRadius != borderRadius;
   }
 }