Merge pull request #78 from djpnewton/rear-cam-web

fix use of 'facingMode' to enable rear cam on web

@@ -80,8 +80,10 @@ class MobileScannerWebPlugin {
   Future<Map> _start(arguments) async {
     vidDiv.children = [video];
 
-    final CameraFacing cameraFacing =
-        arguments['cameraFacing'] ?? CameraFacing.front;
+    var cameraFacing = CameraFacing.front;
+    if (arguments.containsKey('facing')) {
+      cameraFacing = CameraFacing.values[arguments['facing']];
+    }
 
     // See https://github.com/flutter/flutter/issues/41563
     // ignore: UNDEFINED_PREFIXED_NAME
@@ -105,18 +107,17 @@ class MobileScannerWebPlugin {
       Map? capabilities =
           html.window.navigator.mediaDevices?.getSupportedConstraints();
       if (capabilities != null && capabilities['facingMode']) {
-        UserMediaOptions constraints = UserMediaOptions(
-            video: VideoOptions(
-          facingMode:
-              (cameraFacing == CameraFacing.front ? 'user' : 'environment'),
-          width: {'ideal': 4096},
-          height: {'ideal': 2160},
-        ));
+        var constraints = {
+          'video': VideoOptions(
+              facingMode:
+                  (cameraFacing == CameraFacing.front ? 'user' : 'environment'))
+        };
 
         _localStream =
-            await html.window.navigator.getUserMedia(video: constraints);
+            await html.window.navigator.mediaDevices?.getUserMedia(constraints);
       } else {
-        _localStream = await html.window.navigator.getUserMedia(video: true);
+        _localStream = await html.window.navigator.mediaDevices
+            ?.getUserMedia({'video': true});
       }
 
       video.srcObject = _localStream;
@@ -146,7 +147,7 @@ class MobileScannerWebPlugin {
         'torchable': hasFlash
       };
     } catch (e) {
-      throw PlatformException(code: 'MobileScannerWeb', message: e.toString());
+      throw PlatformException(code: 'MobileScannerWeb', message: '$e');
     }
   }
 
@@ -166,7 +167,7 @@ class MobileScannerWebPlugin {
   Future<void> cancel() async {
     try {
       // Stop the camera stream
-      _localStream!.getTracks().forEach((track) {
+      _localStream?.getTracks().forEach((track) {
         if (track.readyState == 'live') {
           track.stop();
         }