feat: add hasTorch notifier

@@ -77,7 +77,13 @@ class _BarcodeScannerWithControllerState
                   child: Row(
                     mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                     children: [
-                      IconButton(
+                      ValueListenableBuilder(
+                          valueListenable: controller.hasTorchState,
+                          builder: (context, state, child) {
+                            if (state != true) {
+                              return const SizedBox.shrink();
+                            }
+                            return IconButton(
                               color: Colors.white,
                               icon: ValueListenableBuilder(
                                 valueListenable: controller.torchState,
@@ -104,7 +110,8 @@ class _BarcodeScannerWithControllerState
                               ),
                               iconSize: 32.0,
                               onPressed: () => controller.toggleTorch(),
-                      ),
+                            );
+                          }),
                       IconButton(
                         color: Colors.white,
                         icon: isStarted

@@ -99,7 +99,8 @@ class MobileScannerController {
 
   bool isStarting = false;
 
-  bool? _hasTorch;
+  /// A notifier that provides availability of the Torch (Flash)
+  final ValueNotifier<bool?> hasTorchState = ValueNotifier(false);
 
   /// Returns whether the device has a torch.
   ///
@@ -210,8 +211,9 @@ class MobileScannerController {
       );
     }
 
-    _hasTorch = startResult['torchable'] as bool? ?? false;
-    if (_hasTorch! && torchEnabled) {
+    final hasTorch = startResult['torchable'] as bool? ?? false;
+    hasTorchState.value = hasTorch;
+    if (hasTorch && torchEnabled) {
       torchState.value = TorchState.on;
     }
 
@@ -223,7 +225,7 @@ class MobileScannerController {
               startResult['videoHeight'] as double? ?? 0,
             )
           : toSize(startResult['size'] as Map? ?? {}),
-      hasTorch: _hasTorch!,
+      hasTorch: hasTorch,
       textureId: kIsWeb ? null : startResult['textureId'] as int?,
       webId: kIsWeb ? startResult['ViewID'] as String? : null,
     );
@@ -244,7 +246,7 @@ class MobileScannerController {
   ///
   /// Throws if the controller was not initialized.
   Future<void> toggleTorch() async {
-    final hasTorch = _hasTorch;
+    final hasTorch = hasTorchState.value;
 
     if (hasTorch == null) {
       throw const MobileScannerException(

@@ -98,8 +98,7 @@ mixin InternalStreamCreation on WebBarcodeReaderBase {
 
 /// Mixin for libraries that don't have built-in torch support
 mixin InternalTorchDetection on InternalStreamCreation {
-  @override
-  Future<bool> hasTorch() async {
+  Future<List<String>> getSupportedTorchStates() async {
     try {
       final track = localMediaStream?.getVideoTracks();
       if (track != null) {
@@ -107,13 +106,21 @@ mixin InternalTorchDetection on InternalStreamCreation {
         final photoCapabilities = await promiseToFuture<PhotoCapabilities>(
           imageCapture.getPhotoCapabilities(),
         );
-        return photoCapabilities.fillLightMode != null;
+        final fillLightMode = photoCapabilities.fillLightMode;
+        if (fillLightMode != null) {
+          return fillLightMode;
+        }
       }
     } catch (e) {
       // ImageCapture is not supported by some browsers:
       // https://developer.mozilla.org/en-US/docs/Web/API/ImageCapture#browser_compatibility
     }
-    return false;
+    return [];
+  }
+
+  @override
+  Future<bool> hasTorch() async {
+    return (await getSupportedTorchStates()).isNotEmpty;
   }
 
   @override