clean up the scan window overlay

Author: navaronbracke

CHANGELOG.md

@@ -11,6 +11,7 @@ Bugs fixed:
 
 Improvements:
 * Added a basic barcode overlay widget, for use with the camera preview.
+* Added a basic scan window overlay widget, for use with the camera preview.
 * Update the bundled MLKit model for Android to version `17.3.0`.
 * Added documentation in places where it was missing.
 * Added `color` and `style` properties to the `BarcodePainter` widget.

lib/mobile_scanner.dart

@@ -29,5 +29,5 @@ export 'src/objects/url_bookmark.dart';
 export 'src/objects/wifi.dart';
 export 'src/overlay/barcode_overlay.dart';
 export 'src/overlay/barcode_painter.dart';
-export 'src/overlay/scanner_overlay.dart';
-export 'src/overlay/scanner_painter.dart';
+export 'src/overlay/scan_window_overlay.dart';
+export 'src/overlay/scan_window_painter.dart';

lib/src/overlay/scan_window_overlay.dart

@@ -0,0 +1,50 @@
+import 'package:flutter/material.dart';
+import 'package:mobile_scanner/src/mobile_scanner_controller.dart';
+import 'package:mobile_scanner/src/overlay/scan_window_painter.dart';
+
+/// This widget represents an overlay that paints a scan window cutout.
+class ScanWindowOverlay extends StatelessWidget {
+  /// Construct a new [ScanWindowOverlay] instance.
+  const ScanWindowOverlay({
+    super.key,
+    required this.controller,
+    required this.scanWindow,
+    this.color = const Color(0x80000000),
+  });
+
+  /// The color for the scan window box.
+  ///
+  /// Defaults to [Colors.black] with 50% opacity.
+  final Color color;
+
+  /// The controller that manages the camera preview.
+  final MobileScannerController controller;
+
+  /// The scan window for the overlay.
+  final Rect scanWindow;
+
+  @override
+  Widget build(BuildContext context) {
+    if (scanWindow.isEmpty || scanWindow.isInfinite) {
+      return const SizedBox();
+    }
+
+    return ValueListenableBuilder(
+      valueListenable: controller,
+      builder: (context, value, child) {
+        // Not ready.
+        if (!value.isInitialized || !value.isRunning || value.error != null || value.size.isEmpty) {
+          return const SizedBox();
+        }
+
+        return CustomPaint(
+          size: value.size,
+          painter: ScanWindowPainter(
+            scanWindow: scanWindow,
+            color: color,
+          ),
+        );
+      },
+    );
+  }
+}

lib/src/overlay/scan_window_painter.dart

@@ -4,16 +4,14 @@ import 'package:flutter/material.dart';
 class ScanWindowPainter extends CustomPainter {
   /// Construct a new [ScanWindowPainter] instance.
   const ScanWindowPainter({
+    required this.color,
     required this.scanWindow,
-    this.color = const Color(0x80000000),
   });
 
   /// The color for the scan window box.
   final Color color;
 
-  /// The rectangle defining the scan window.
-  ///
-  /// Defaults to [Colors.black] with 50% opacity.
+  /// The rectangle that defines the scan window.
   final Rect scanWindow;
 
   @override
@@ -32,7 +30,7 @@ class ScanWindowPainter extends CustomPainter {
     final overlayWithCutoutPath = Path.combine(PathOperation.difference, backgroundPath, cutoutPath);
 
     // Paint the overlay with the cutout
-    final paint = Paint()..color = Colors.black.withOpacity(0.5);
+    final paint = Paint()..color = color;
     canvas.drawPath(overlayWithCutoutPath, paint);
   }