Fix stop sharing button state.

vector/src/main/java/im/vector/app/features/call/VectorCallViewModel.kt

@@ -224,7 +224,8 @@ class VectorCallViewModel @AssistedInject constructor(
                         formattedDuration = webRtcCall.formattedDuration(),
                         isHD = webRtcCall.mxCall.isVideoCall && webRtcCall.currentCaptureFormat() is CaptureFormat.HD,
                         canOpponentBeTransferred = webRtcCall.mxCall.capabilities.supportCallTransfer(),
-                        transferee = computeTransfereeState(webRtcCall.mxCall)
+                        transferee = computeTransfereeState(webRtcCall.mxCall),
+                        isSharingScreen = webRtcCall.isSharingScreen()
                 )
             }
             updateOtherKnownCall(webRtcCall)

vector/src/main/java/im/vector/app/features/call/webrtc/WebRtcCall.kt

@@ -97,6 +97,7 @@ import kotlin.coroutines.CoroutineContext
 private const val STREAM_ID = "userMedia"
 private const val AUDIO_TRACK_ID = "${STREAM_ID}a0"
 private const val VIDEO_TRACK_ID = "${STREAM_ID}v0"
+private const val SCREEN_TRACK_ID = "${STREAM_ID}s0"
 private val DEFAULT_AUDIO_CONSTRAINTS = MediaConstraints()
 private const val INVITE_TIMEOUT_IN_MS = 60_000L
 
@@ -805,7 +806,7 @@ class WebRtcCall(
     }
 
     private fun showScreenLocally(factory: PeerConnectionFactory, videoSource: VideoSource?, localMediaStream: MediaStream?) {
-        localVideoTrack = factory.createVideoTrack(VIDEO_TRACK_ID, videoSource).apply { setEnabled(true) }
+        localVideoTrack = factory.createVideoTrack(SCREEN_TRACK_ID, videoSource).apply { setEnabled(true) }
         localMediaStream?.addTrack(localVideoTrack)
         localSurfaceRenderers.forEach { it.get()?.let { localVideoTrack?.addSink(it) } }
     }
@@ -820,6 +821,13 @@ class WebRtcCall(
         videoCapturer.startCapture(currentCaptureFormat.width, currentCaptureFormat.height, currentCaptureFormat.fps)
     }
 
+    /**
+     * Returns true if the user is sharing the screen, false otherwise.
+     */
+    fun isSharingScreen(): Boolean {
+        return localVideoTrack?.id() == SCREEN_TRACK_ID
+    }
+
     private suspend fun release() {
         listeners.clear()
         mxCall.removeListener(this)