Changes lastN event params to be leaving and entering endpoint IDs.

JitsiConferenceEventManager.js

     const conference = this.conference;
     const rtc = conference.rtc;
 
-    this.rtcForwarder
-        = new EventEmitterForwarder(rtc, this.conference.eventEmitter);
-
     rtc.addListener(
         RTCEvents.REMOTE_TRACK_ADDED,
         conference.onRemoteTrackAdded.bind(conference));
             { value: now });
     });
 
-    this.rtcForwarder.forward(RTCEvents.LASTN_ENDPOINT_CHANGED,
-        JitsiConferenceEvents.LAST_N_ENDPOINTS_CHANGED);
-
     rtc.addListener(
         RTCEvents.AVAILABLE_DEVICES_CHANGED,
         devices => conference.room.updateDeviceAvailability(devices));

JitsiConferenceEvents.js

 
 /**
  * The Last N set is changed.
+ *
+ * @param {Array<string>|null} leavingEndpointIds the ids of all the endpoints
+ * which are leaving Last N
+ * @param {Array<string>|null} enteringEndpointIds the ids of all the endpoints
+ * which are entering Last N
  */
 export const LAST_N_ENDPOINTS_CHANGED = 'conference.lastNEndpointsChanged';
 

doc/API.md

         - MESSAGE_RECEIVED - new text message received. (parameters - id(string), text(string), ts(number))
         - DISPLAY_NAME_CHANGED - user has changed his display name. (parameters - id(string), displayName(string))
         - SUBJECT_CHANGED - notifies that subject of the conference has changed (parameters - subject(string))
-        - LAST_N_ENDPOINTS_CHANGED - last n set was changed (parameters - array of ids of users)
-        - IN_LAST_N_CHANGED - passes boolean property that shows whether the local user is included in last n set of any other user or not. (parameters - boolean)
+        - LAST_N_ENDPOINTS_CHANGED - last n set was changed (parameters - leavingEndpointIds(array) ids of users leaving lastN, enteringEndpointIds(array) ids of users entering lastN)
         - CONFERENCE_JOINED - notifies the local user that he joined the conference successfully. (no parameters)
         - CONFERENCE_LEFT - notifies the local user that he left the conference successfully. (no parameters)
         - DTMF_SUPPORT_CHANGED - notifies if at least one user supports DTMF. (parameters - supports(boolean))

modules/RTC/DataChannels.js

                 // The new/latest list of last-n endpoint IDs.
                 const lastNEndpoints = obj.lastNEndpoints;
 
-                // The list of endpoint IDs which are entering the list of
-                // last-n at this time i.e. were not in the old list of last-n
-                // endpoint IDs.
-                const endpointsEnteringLastN = obj.endpointsEnteringLastN;
-
                 logger.info('Data channel new last-n event: ',
-                    lastNEndpoints, endpointsEnteringLastN, obj);
+                    lastNEndpoints, obj);
                 self.eventEmitter.emit(RTCEvents.LASTN_ENDPOINT_CHANGED,
-                    lastNEndpoints, endpointsEnteringLastN, obj);
+                    lastNEndpoints, obj);
             } else if (colibriClass === 'EndpointMessage') {
                 self.eventEmitter.emit(
                     RTCEvents.ENDPOINT_MESSAGE_RECEIVED, obj.from,

modules/RTC/RTC.js

 import DataChannels from './DataChannels';
 import { getLogger } from 'jitsi-meet-logger';
 import GlobalOnErrorHandler from '../util/GlobalOnErrorHandler';
+import * as JitsiConferenceEvents from '../../JitsiConferenceEvents';
 import JitsiLocalTrack from './JitsiLocalTrack.js';
 import JitsiTrackError from '../../JitsiTrackError';
 import * as JitsiTrackErrors from '../../JitsiTrackErrors';
         this._lastNEndpoints = null;
 
         // The last N change listener.
-        this._lastNChangeListener = null;
+        this._lastNChangeListener = this._onLastNChanged.bind(this);
 
         // Switch audio output device on all remote audio tracks. Local audio
         // tracks handle this event by themselves.
                 this._dataChannelOpenListener);
 
             // Add Last N change listener.
-            this._lastNChangeListener = lastNEndpoints => {
-                this._lastNEndpoints = lastNEndpoints;
-            };
-
             this.addListener(RTCEvents.LASTN_ENDPOINT_CHANGED,
                 this._lastNChangeListener);
         }
     }
 
+    /**
+     * Receives events when Last N had changed.
+     * @param {array} lastNEndpoints the new Last N endpoints.
+     * @private
+     */
+    _onLastNChanged(lastNEndpoints) {
+        const oldLastNEndpoints = this._lastNEndpoints;
+        let leavingLastNEndpoints = [];
+        let enteringLastNEndpoints = [];
+
+        this._lastNEndpoints = lastNEndpoints;
+
+        if (oldLastNEndpoints) {
+            leavingLastNEndpoints = oldLastNEndpoints.filter(
+                id => !this.isInLastN(id));
+
+            if (lastNEndpoints) {
+                enteringLastNEndpoints = lastNEndpoints.filter(
+                    id => oldLastNEndpoints.indexOf(id) === -1);
+            }
+        }
+
+        this.conference.eventEmitter.emit(
+            JitsiConferenceEvents.LAST_N_ENDPOINTS_CHANGED,
+            leavingLastNEndpoints,
+            enteringLastNEndpoints);
+    }
+
     /**
      * Should be called when current media session ends and after the
      * PeerConnection has been closed using PeerConnection.close() method.
             this.dataChannels.closeAllChannels();
             this.dataChannelsOpen = false;
 
-            if (this._lastNChangeListener) {
-                this.removeListener(RTCEvents.LASTN_ENDPOINT_CHANGED,
-                    this._lastNChangeListener);
-            }
+            this.removeListener(RTCEvents.LASTN_ENDPOINT_CHANGED,
+                this._lastNChangeListener);
         }
     }