Stop screen sharing when disabled from system UI.

app/src/main/java/org/thoughtcrime/securesms/ringrtc/CameraEventListener.java

@@ -11,4 +11,5 @@ public interface CameraEventListener {
   void onFullyInitialized();
   void onCameraSwitchCompleted(@NonNull CameraState newCameraState);
   void onCameraStopped();
+  void onScreenShareStopped();
 }

app/src/main/java/org/thoughtcrime/securesms/ringrtc/OutgoingVideoSourceRouter.kt

@@ -19,7 +19,7 @@ import kotlin.concurrent.Volatile
 class OutgoingVideoSourceRouter(
   private val context: Context,
   private val eglBase: EglBaseWrapper,
-  cameraEventListener: CameraEventListener,
+  private val cameraEventListener: CameraEventListener,
   desiredCameraDirection: CameraState.Direction
 ) : CameraControl {
 
@@ -92,7 +92,12 @@ class OutgoingVideoSourceRouter(
     }
 
     if (screenShareCapturer == null) {
-      screenShareCapturer = ScreenShareCapturer(context, eglBase, ScreenSideObserver())
+      screenShareCapturer = ScreenShareCapturer(
+        context = context,
+        eglBase = eglBase,
+        sink = ScreenSideObserver(),
+        onMediaProjectionStopped = cameraEventListener::onScreenShareStopped
+      )
     }
 
     screenShareCapturer!!.start(mediaProjectionData)

app/src/main/java/org/thoughtcrime/securesms/ringrtc/ScreenShareCapturer.kt

@@ -24,7 +24,8 @@ import kotlin.math.max
 class ScreenShareCapturer(
   private val context: Context,
   private val eglBase: EglBaseWrapper,
-  private val sink: CapturerObserver
+  private val sink: CapturerObserver,
+  private val onMediaProjectionStopped: () -> Unit
 ) {
 
   companion object {
@@ -70,6 +71,7 @@ class ScreenShareCapturer(
         object : MediaProjection.Callback() {
           override fun onStop() {
             Log.i(TAG, "MediaProjection stopped")
+            onMediaProjectionStopped()
           }
 
           override fun onCapturedContentResize(width: Int, height: Int) {

app/src/main/java/org/thoughtcrime/securesms/service/webrtc/SignalCallManager.java

@@ -1098,6 +1098,11 @@ public final class SignalCallManager implements CallManager.Observer, GroupCall.
     setEnableVideo(false);
   }
 
+  @Override
+  public void onScreenShareStopped() {
+    stopScreenShare();
+  }
+
   @Override
   public void onForeground() {
     process((s, p) -> {