communicate video enabling status using data channel

Session/Calls/CallVC.swift

@@ -37,6 +37,7 @@ final class CallVC : UIViewController, WebRTCSessionDelegate {
     
     private lazy var remoteVideoView: RTCMTLVideoView = {
         let result = RTCMTLVideoView()
+        result.alpha = 0
         result.contentMode = .scaleAspectFill
         return result
     }()
@@ -293,7 +294,11 @@ final class CallVC : UIViewController, WebRTCSessionDelegate {
     }
     
     func isRemoteVideoDidChange(isEnabled: Bool) {
-        remoteVideoView.isHidden = !isEnabled
+        DispatchQueue.main.async {
+            UIView.animate(withDuration: 0.25) {
+                self.remoteVideoView.alpha = isEnabled ? 1 : 0
+            }
+        }
     }
     
     // MARK: Interaction

SessionMessagingKit/Calls/WebRTCSession+DataChannel.swift

@@ -3,18 +3,17 @@ import Foundation
 
 extension WebRTCSession: RTCDataChannelDelegate {
     
-    internal func createDataChannel() {
+    internal func createDataChannel() -> RTCDataChannel? {
         let dataChannelConfiguration = RTCDataChannelConfiguration()
-        dataChannelConfiguration.isOrdered = true
-        dataChannelConfiguration.isNegotiated = true
-        dataChannelConfiguration.maxRetransmits = 30
-        dataChannelConfiguration.maxPacketLifeTime = 30000
-        dataChannel = peerConnection.dataChannel(forLabel: "DATACHANNEL", configuration: dataChannelConfiguration)
-        dataChannel?.delegate = self
+        guard let dataChannel = peerConnection.dataChannel(forLabel: "VIDEOCONTROL", configuration: dataChannelConfiguration) else {
+            print("[Calls] Couldn't create data channel.")
+            return nil
+        }
+        return dataChannel
     }
     
     public func sendJSON(_ json: JSON) {
-        if let dataChannel = dataChannel, let jsonAsData = try? JSONSerialization.data(withJSONObject: json, options: [ .fragmentsAllowed ]) {
+        if let dataChannel = remoteDataChannel, let jsonAsData = try? JSONSerialization.data(withJSONObject: json, options: [ .fragmentsAllowed ]) {
             let dataBuffer = RTCDataBuffer(data: jsonAsData, isBinary: false)
             dataChannel.sendData(dataBuffer)
         }
@@ -22,7 +21,7 @@ extension WebRTCSession: RTCDataChannelDelegate {
     
     // MARK: Data channel delegate
     public func dataChannelDidChangeState(_ dataChannel: RTCDataChannel) {
-        print("[Calls] Data channed did change to \(dataChannel.readyState)")
+        print("[Calls] Data channel did change to \(dataChannel.readyState)")
     }
     
     public func dataChannel(_ dataChannel: RTCDataChannel, didReceiveMessageWith buffer: RTCDataBuffer) {

SessionMessagingKit/Calls/WebRTCSession.swift

@@ -74,7 +74,8 @@ public final class WebRTCSession : NSObject, RTCPeerConnectionDelegate {
     }()
     
     // Data Channel
-    internal var dataChannel: RTCDataChannel?
+    internal var localDataChannel: RTCDataChannel?
+    internal var remoteDataChannel: RTCDataChannel?
     
     // MARK: Error
     public enum Error : LocalizedError {
@@ -99,12 +100,17 @@ public final class WebRTCSession : NSObject, RTCPeerConnectionDelegate {
         peerConnection.add(localVideoTrack, streamIds: mediaStreamTrackIDS)
         // Configure audio session
         configureAudioSession()
+        
+        // Data channel
+        if let dataChannel = createDataChannel() {
+            dataChannel.delegate = self
+            self.localDataChannel = dataChannel
+        }
     }
     
     // MARK: Signaling
     public func sendPreOffer(to sessionID: String, using transaction: YapDatabaseReadWriteTransaction) -> Promise<Void> {
         print("[Calls] Sending pre-offer message.")
-        createDataChannel()
         guard let thread = TSContactThread.fetch(for: sessionID, using: transaction) else { return Promise(error: Error.noThread) }
         let (promise, seal) = Promise<Void>.pending()
         DispatchQueue.main.async {
@@ -267,8 +273,7 @@ public final class WebRTCSession : NSObject, RTCPeerConnectionDelegate {
     
     public func peerConnection(_ peerConnection: RTCPeerConnection, didOpen dataChannel: RTCDataChannel) {
         print("[Calls] Data channel opened.")
-        self.dataChannel = dataChannel
-        self.dataChannel?.delegate = self
+        self.remoteDataChannel = dataChannel
     }
 }