Improve QR scanner: prefer built-in camera, add rectOfInterest, fallback metadata types

Sources/QRScannerView.swift

@@ -99,8 +99,17 @@ class QRScannerWindowController: NSObject, AVCaptureMetadataOutputObjectsDelegat
     // 在后台线程初始化摄像头
     private func setupCaptureOnBackground(previewHost: NSView) {
         let session = AVCaptureSession()
+        session.sessionPreset = .high
         
-        guard let device = AVCaptureDevice.default(for: .video) else {
+        // 优先选内置摄像头，避免 Continuity Camera 不支持 metadata
+        var device: AVCaptureDevice?
+        if let builtIn = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .unspecified) {
+            device = builtIn
+        } else {
+            device = AVCaptureDevice.default(for: .video)
+        }
+        
+        guard let device = device else {
             DispatchQueue.main.async { [weak self] in
                 self?.showError("No camera available")
             }
@@ -125,6 +134,12 @@ class QRScannerWindowController: NSObject, AVCaptureMetadataOutputObjectsDelegat
             // 检查摄像头是否支持 QR 码识别
             if output.availableMetadataObjectTypes.contains(.qr) {
                 output.metadataObjectTypes = [.qr]
+                output.rectOfInterest = CGRect(x: 0.1, y: 0.1, width: 0.8, height: 0.8)
+            } else {
+                // fallback: 支持什么就用什么
+                let types = output.availableMetadataObjectTypes.filter { $0 == .qr || $0 == .ean13 || $0 == .ean8 || $0 == .code128 }
+                if !types.isEmpty {
+                    output.metadataObjectTypes = types
                 } else {
                     DispatchQueue.main.async { [weak self] in
                         self?.showError("Camera does not support QR code scanning")
@@ -132,6 +147,7 @@ class QRScannerWindowController: NSObject, AVCaptureMetadataOutputObjectsDelegat
                     return
                 }
             }
+        }
         
         let previewLayer = AVCaptureVideoPreviewLayer(session: session)
         previewLayer.videoGravity = .resizeAspectFill