[camera_web] Add support for pausing and resuming the camera preview (#…

…4239)

* chore: update camera_platform_interface to 2.1.0
* feat: add pause to Camera
* test: add Camera pause test
* feat: add pausePreview and resumePreview implementation
* test: add pausePreview and resumePreview tests

packages/camera/camera_web/example/integration_test/camera_test.dart

@@ -214,6 +214,24 @@ void main() {
       });
     });
 
+    group('pause', () {
+      testWidgets('pauses the camera stream', (tester) async {
+        final camera = Camera(
+          textureId: textureId,
+          cameraService: cameraService,
+        );
+
+        await camera.initialize();
+        await camera.play();
+
+        expect(camera.videoElement.paused, isFalse);
+
+        camera.pause();
+
+        expect(camera.videoElement.paused, isTrue);
+      });
+    });
+
     group('stop', () {
       testWidgets('resets the camera stream', (tester) async {
         final camera = Camera(

packages/camera/camera_web/example/integration_test/camera_web_test.dart

@@ -1459,6 +1459,135 @@ void main() {
       });
     });
 
+    group('pausePreview', () {
+      testWidgets('calls pause on the camera', (tester) async {
+        final camera = MockCamera();
+
+        // Save the camera in the camera plugin.
+        (CameraPlatform.instance as CameraPlugin).cameras[cameraId] = camera;
+
+        await CameraPlatform.instance.pausePreview(cameraId);
+
+        verify(camera.pause).called(1);
+      });
+
+      group('throws PlatformException', () {
+        testWidgets(
+            'with notFound error '
+            'if the camera does not exist', (tester) async {
+          expect(
+            () async => await CameraPlatform.instance.pausePreview(cameraId),
+            throwsA(
+              isA<PlatformException>().having(
+                (e) => e.code,
+                'code',
+                CameraErrorCode.notFound.toString(),
+              ),
+            ),
+          );
+        });
+
+        testWidgets('when pause throws DomException', (tester) async {
+          final camera = MockCamera();
+          final exception = FakeDomException(DomException.NOT_SUPPORTED);
+
+          when(camera.pause).thenThrow(exception);
+
+          // Save the camera in the camera plugin.
+          (CameraPlatform.instance as CameraPlugin).cameras[cameraId] = camera;
+
+          expect(
+            () async => await CameraPlatform.instance.pausePreview(cameraId),
+            throwsA(
+              isA<PlatformException>().having(
+                (e) => e.code,
+                'code',
+                exception.name,
+              ),
+            ),
+          );
+        });
+      });
+    });
+
+    group('resumePreview', () {
+      testWidgets('calls play on the camera', (tester) async {
+        final camera = MockCamera();
+
+        when(camera.play).thenAnswer((_) async => {});
+
+        // Save the camera in the camera plugin.
+        (CameraPlatform.instance as CameraPlugin).cameras[cameraId] = camera;
+
+        await CameraPlatform.instance.resumePreview(cameraId);
+
+        verify(camera.play).called(1);
+      });
+
+      group('throws PlatformException', () {
+        testWidgets(
+            'with notFound error '
+            'if the camera does not exist', (tester) async {
+          expect(
+            () async => await CameraPlatform.instance.resumePreview(cameraId),
+            throwsA(
+              isA<PlatformException>().having(
+                (e) => e.code,
+                'code',
+                CameraErrorCode.notFound.toString(),
+              ),
+            ),
+          );
+        });
+
+        testWidgets('when play throws DomException', (tester) async {
+          final camera = MockCamera();
+          final exception = FakeDomException(DomException.NOT_SUPPORTED);
+
+          when(camera.play).thenThrow(exception);
+
+          // Save the camera in the camera plugin.
+          (CameraPlatform.instance as CameraPlugin).cameras[cameraId] = camera;
+
+          expect(
+            () async => await CameraPlatform.instance.resumePreview(cameraId),
+            throwsA(
+              isA<PlatformException>().having(
+                (e) => e.code,
+                'code',
+                exception.name,
+              ),
+            ),
+          );
+        });
+
+        testWidgets('when play throws CameraWebException', (tester) async {
+          final camera = MockCamera();
+          final exception = CameraWebException(
+            cameraId,
+            CameraErrorCode.unknown,
+            'description',
+          );
+
+          when(camera.play).thenThrow(exception);
+
+          // Save the camera in the camera plugin.
+          (CameraPlatform.instance as CameraPlugin).cameras[cameraId] = camera;
+
+          expect(
+            () async => await CameraPlatform.instance.resumePreview(cameraId),
+            throwsA(
+              isA<PlatformException>().having(
+                (e) => e.code,
+                'code',
+                exception.code.toString(),
+              ),
+            ),
+          );
+        });
+      });
+    });
+
     testWidgets(
         'buildPreview returns an HtmlElementView '
         'with an appropriate view type', (tester) async {
@@ -1993,6 +2122,42 @@ void main() {
 
           await streamQueue.cancel();
         });
+
+        testWidgets(
+            'emits a CameraErrorEvent '
+            'on resumePreview error', (tester) async {
+          final exception = CameraWebException(
+            cameraId,
+            CameraErrorCode.unknown,
+            'description',
+          );
+
+          when(camera.play).thenThrow(exception);
+
+          final Stream<CameraErrorEvent> eventStream =
+              CameraPlatform.instance.onCameraError(cameraId);
+
+          final streamQueue = StreamQueue(eventStream);
+
+          expect(
+            () async => await CameraPlatform.instance.resumePreview(cameraId),
+            throwsA(
+              isA<PlatformException>(),
+            ),
+          );
+
+          expect(
+            await streamQueue.next,
+            equals(
+              CameraErrorEvent(
+                cameraId,
+                'Error code: ${exception.code}, error message: ${exception.description}',
+              ),
+            ),
+          );
+
+          await streamQueue.cancel();
+        });
       });
 
       testWidgets('onVideoRecordedEvent throws UnimplementedError',

packages/camera/camera_web/lib/src/camera.dart

@@ -119,6 +119,11 @@ class Camera {
     await videoElement.play();
   }
 
+  /// Pauses the camera stream on the current frame.
+  void pause() async {
+    videoElement.pause();
+  }
+
   /// Stops the camera stream and resets the camera source.
   void stop() {
     final tracks = videoElement.srcObject?.getTracks();

packages/camera/camera_web/lib/src/camera_web.dart

@@ -517,6 +517,27 @@ class CameraPlugin extends CameraPlatform {
     }
   }
 
+  @override
+  Future<void> pausePreview(int cameraId) async {
+    try {
+      getCamera(cameraId).pause();
+    } on html.DomException catch (e) {
+      throw PlatformException(code: e.name, message: e.message);
+    }
+  }
+
+  @override
+  Future<void> resumePreview(int cameraId) async {
+    try {
+      await getCamera(cameraId).play();
+    } on html.DomException catch (e) {
+      throw PlatformException(code: e.name, message: e.message);
+    } on CameraWebException catch (e) {
+      _addCameraErrorEvent(e);
+      throw PlatformException(code: e.code.toString(), message: e.description);
+    }
+  }
+
   @override
   Widget buildPreview(int cameraId) {
     return HtmlElementView(

packages/camera/camera_web/pubspec.yaml

@@ -21,7 +21,7 @@ flutter:
         fileName: camera_web.dart
 
 dependencies:
-  camera_platform_interface: ^2.0.1
+  camera_platform_interface: ^2.1.0
   flutter:
     sdk: flutter
   flutter_web_plugins: