feature: switch between front and back cameras

lib/src/track/local_video_track.dart

@@ -5,6 +5,8 @@ import 'options.dart';
 import 'video_track.dart';
 
 class LocalVideoTrack extends VideoTrack {
+  RTCRtpSender? get sender => transceiver?.sender;
+
   LocalVideoTrack(String name, MediaStreamTrack mediaTrack, MediaStream stream)
       : super(name, mediaTrack, stream);
 
@@ -14,6 +16,41 @@ class LocalVideoTrack extends VideoTrack {
       options = LocalVideoTrackOptions(params: VideoPresets.qhd);
     }
 
+    try {
+      var stream = await _createCameraStream(options);
+      return LocalVideoTrack("camera", stream.getVideoTracks().first, stream);
+    } catch (e) {
+      return Future.error(e);
+    }
+  }
+
+  Future<void> restartTrack([LocalVideoTrackOptions? options]) async {
+    if (sender == null) {
+      return Future.error(TrackCreateError('could not restart track'));
+    }
+
+    if (options == null) {
+      options = LocalVideoTrackOptions(params: VideoPresets.qhd);
+    }
+
+    try {
+      var stream = await _createCameraStream(options);
+      var track = stream.getVideoTracks().first;
+      mediaStream = stream;
+      await mediaTrack.stop();
+      mediaTrack = track;
+      await sender?.replaceTrack(track);
+    } catch (e) {
+      return Future.error(e);
+    }
+  }
+
+  static Future<MediaStream> _createCameraStream(
+      LocalVideoTrackOptions? options) async {
+    if (options == null) {
+      options = LocalVideoTrackOptions(params: VideoPresets.qhd);
+    }
+
     try {
       var stream = await navigator.mediaDevices.getUserMedia({
         "audio": false,
@@ -24,7 +61,7 @@ class LocalVideoTrack extends VideoTrack {
         return Future.error(TrackCreateError());
       }
 
-      return LocalVideoTrack("camera", stream.getVideoTracks().first, stream);
+      return stream;
     } catch (e) {
       return Future.error(e);
     }

lib/src/track/options.dart

@@ -3,9 +3,12 @@ class LocalVideoTrackOptions {
   VideoParameter params;
 
   LocalVideoTrackOptions({
-    required VideoParameter params,
+    VideoParameter? params,
     CameraPosition? position,
-  }) : this.params = params {
+  }) : params = VideoPresets.qhd {
+    if (params != null) {
+      this.params = params;
+    }
     if (position != null) {
       this.position = position;
     }

lib/src/track/remote_track_publication.dart

@@ -49,6 +49,9 @@ class RemoteTrackPublication extends TrackPublication {
       _participant.delegate?.onTrackUnmuted(_participant, this);
       _participant.roomDelegate?.onTrackUnmuted(_participant, this);
     }
+    if (subscribed) {
+      track?.mediaTrack.enabled = !val;
+    }
     _participant.muteChanged();
   }
 

lib/src/track/track.dart

@@ -22,6 +22,8 @@ class Track {
 
   Track(this.kind, this.name, this.mediaTrack);
 
+  bool get muted => mediaTrack.muted == null ? false : mediaTrack.muted!;
+
   RTCRtpMediaType get mediaType {
     switch (kind) {
       case TrackType.AUDIO:

lib/src/track/video_track.dart

@@ -1,18 +1,27 @@
+import 'package:flutter/material.dart';
 import 'package:flutter_webrtc/flutter_webrtc.dart';
 
 import '../proto/livekit_models.pb.dart';
 import 'track.dart';
 
-class VideoTrack extends Track {
-  MediaStream? mediaStream;
+/// A video track will notify when its mediaTrack has changed.
+class VideoTrack extends Track with ChangeNotifier {
+  MediaStream? _mediaStream;
 
-  VideoTrack(String name, MediaStreamTrack mediaTrack, this.mediaStream)
+  VideoTrack(String name, MediaStreamTrack mediaTrack, this._mediaStream)
       : super(TrackType.VIDEO, name, mediaTrack);
 
+  MediaStream? get mediaStream => _mediaStream;
+
+  set mediaStream(MediaStream? stream) {
+    _mediaStream = stream;
+    notifyListeners();
+  }
+
   @override
   stop() {
     super.stop();
-    mediaStream?.dispose();
-    mediaStream = null;
+    _mediaStream?.dispose();
+    _mediaStream = null;
   }
 }

lib/src/widget/video_track_renderer.dart

@@ -23,22 +23,35 @@ class _VideoTrackRendererState extends State<VideoTrackRenderer> {
   @override
   void initState() {
     super.initState();
+    widget.track.addListener(_trackChanged);
     _initRenderer();
   }
 
   @override
   void dispose() {
+    widget.track.removeListener(_trackChanged);
     _renderer.dispose();
     super.dispose();
   }
 
-  _initRenderer() async {
-    await _renderer.initialize();
+  @override
+  void didUpdateWidget(covariant VideoTrackRenderer oldWidget) {
+    oldWidget.track.removeListener(_trackChanged);
+    widget.track.addListener(_trackChanged);
+    super.didUpdateWidget(oldWidget);
+  }
+
+  _trackChanged() {
     setState(() {
       _renderer.srcObject = widget.track.mediaStream;
     });
   }
 
+  _initRenderer() async {
+    await _renderer.initialize();
+    _trackChanged();
+  }
+
   @override
   Widget build(BuildContext context) {
     var isLocal = widget.track is LocalVideoTrack;