feat(screenshare): support remote wireless screensharing (#3809)

* feat(screenshare): support remote wireless screensharing

- Pass events to the ProxyConnectionService so it can
  handle establishing a peer connection so a remote
  participant, not in the conference, can send a
  video stream to the local participant to use as a
  local desktop stream.
- Modify the existing start screensharing flow to accept
  a desktop stream instead of always trying to create one.

* adjust ProxyConnectionService for lib review changes

conference.js

             receiver.stop();
         }
 
+        this._stopProxyConnection();
+
         let promise = null;
 
         if (didHaveVideo) {
 
     /**
      * Creates desktop (screensharing) {@link JitsiLocalTrack}
+     *
      * @param {Object} [options] - Screen sharing options that will be passed to
      * createLocalTracks.
-     *
+     * @param {Object} [options.desktopSharing]
+     * @param {Object} [options.desktopStream] - An existing desktop stream to
+     * use instead of creating a new desktop stream.
      * @return {Promise.<JitsiLocalTrack>} - A Promise resolved with
      * {@link JitsiLocalTrack} for the screensharing or rejected with
      * {@link JitsiTrackError}.
         const didHaveVideo = Boolean(this.localVideo);
         const wasVideoMuted = this.isLocalVideoMuted();
 
-        return createLocalTracksF({
-            desktopSharingSourceDevice: options.desktopSharingSources
-                ? null : config._desktopSharingSourceDevice,
-            desktopSharingSources: options.desktopSharingSources,
-            devices: [ 'desktop' ],
-            desktopSharingExtensionExternalInstallation: {
-                interval: 500,
-                checkAgain: () => DSExternalInstallationInProgress,
-                listener: (status, url) => {
-                    switch (status) {
-                    case 'waitingForExtension': {
-                        DSExternalInstallationInProgress = true;
-                        externalInstallation = true;
-                        const listener = () => {
-                            // Wait a little bit more just to be sure that we
-                            // won't miss the extension installation
-                            setTimeout(
-                                () => {
+        const getDesktopStreamPromise = options.desktopStream
+            ? Promise.resolve([ options.desktopStream ])
+            : createLocalTracksF({
+                desktopSharingSourceDevice: options.desktopSharingSources
+                    ? null : config._desktopSharingSourceDevice,
+                desktopSharingSources: options.desktopSharingSources,
+                devices: [ 'desktop' ],
+                desktopSharingExtensionExternalInstallation: {
+                    interval: 500,
+                    checkAgain: () => DSExternalInstallationInProgress,
+                    listener: (status, url) => {
+                        switch (status) {
+                        case 'waitingForExtension': {
+                            DSExternalInstallationInProgress = true;
+                            externalInstallation = true;
+                            const listener = () => {
+                                // Wait a little bit more just to be sure that
+                                // we won't miss the extension installation
+                                setTimeout(() => {
                                     DSExternalInstallationInProgress = false;
                                 },
                                 500);
-                            APP.UI.removeListener(
+                                APP.UI.removeListener(
+                                    UIEvents.EXTERNAL_INSTALLATION_CANCELED,
+                                    listener);
+                            };
+
+                            APP.UI.addListener(
                                 UIEvents.EXTERNAL_INSTALLATION_CANCELED,
                                 listener);
-                        };
-
-                        APP.UI.addListener(
-                            UIEvents.EXTERNAL_INSTALLATION_CANCELED,
-                            listener);
-                        APP.UI.showExtensionExternalInstallationDialog(url);
-                        break;
-                    }
-                    case 'extensionFound':
-                        // Close the dialog.
-                        externalInstallation && $.prompt.close();
-                        break;
-                    default:
+                            APP.UI.showExtensionExternalInstallationDialog(url);
+                            break;
+                        }
+                        case 'extensionFound':
+                            // Close the dialog.
+                            externalInstallation && $.prompt.close();
+                            break;
+                        default:
 
-                        // Unknown status
+                            // Unknown status
+                        }
                     }
                 }
-            }
-        }).then(([ desktopStream ]) => {
+            });
+
+        return getDesktopStreamPromise.then(([ desktopStream ]) => {
             // Stores the "untoggle" handler which remembers whether was
             // there any video before and whether was it muted.
             this._untoggleScreenSharing
     hangup(requestFeedback = false) {
         eventEmitter.emit(JitsiMeetConferenceEvents.BEFORE_HANGUP);
 
+        this._stopProxyConnection();
+
         APP.store.dispatch(destroyLocalTracks());
         this._localTracksInitialized = false;
         this.localVideo = null;
         return this.localVideo.sourceType;
     },
 
+    /**
+     * Callback invoked by the external api create or update a direct connection
+     * from the local client to an external client.
+     *
+     * @param {Object} event - The object containing information that should be
+     * passed to the {@code ProxyConnectionService}.
+     * @returns {void}
+     */
+    onProxyConnectionEvent(event) {
+        if (!this._proxyConnection) {
+            this._proxyConnection = new JitsiMeetJS.ProxyConnectionService({
+                /**
+                 * The proxy connection feature is currently tailored towards
+                 * taking a proxied video stream and showing it as a local
+                 * desktop screen.
+                 */
+                convertVideoToDesktop: true,
+
+                /**
+                 * Callback invoked to pass messages from the local client back
+                 * out to the external client.
+                 *
+                 * @param {string} peerJid - The jid of the intended recipient
+                 * of the message.
+                 * @param {Object} data - The message that should be sent. For
+                 * screensharing this is an iq.
+                 * @returns {void}
+                 */
+                onSendMessage: (peerJid, data) =>
+                    APP.API.sendProxyConnectionEvent({
+                        data,
+                        to: peerJid
+                    }),
+
+                /**
+                 * Callback invoked when the remote peer of the proxy connection
+                 * has provided a video stream, intended to be used as a local
+                 * desktop stream.
+                 *
+                 * @param {JitsiLocalTrack} remoteProxyStream - The media
+                 * stream to use as a local desktop stream.
+                 * @returns {void}
+                 */
+                onRemoteStream: desktopStream => {
+                    if (desktopStream.videoType !== 'desktop') {
+                        logger.warn('Received a non-desktop stream to proxy.');
+                        desktopStream.dispose();
+
+                        return;
+                    }
+
+                    this.toggleScreenSharing(undefined, { desktopStream });
+                }
+            });
+        }
+
+        this._proxyConnection.processMessage(event);
+    },
+
     /**
      * Sets the video muted status.
      *
         if (score === -1 || (score >= 1 && score <= 5)) {
             APP.store.dispatch(submitFeedback(score, message, room));
         }
+    },
+
+    /**
+     * Terminates any proxy screensharing connection that is active.
+     *
+     * @private
+     * @returns {void}
+     */
+    _stopProxyConnection() {
+        if (this._proxyConnection) {
+            this._proxyConnection.stop();
+        }
+
+        this._proxyConnection = null;
     }
 };

modules/API/API.js

             sendAnalytics(createApiEvent('display.name.changed'));
             APP.conference.changeLocalDisplayName(displayName);
         },
+        'proxy-connection-event': event => {
+            APP.conference.onProxyConnectionEvent(event);
+        },
         'submit-feedback': feedback => {
             sendAnalytics(createApiEvent('submit.feedback'));
             APP.conference.submitFeedback(feedback.score, feedback.message);
         });
     }
 
+    /**
+     * Notifies the external application (spot) that the local jitsi-participant
+     * has a status update.
+     *
+     * @param {Object} event - The message to pass onto spot.
+     * @returns {void}
+     */
+    sendProxyConnectionEvent(event: Object) {
+        this._sendEvent({
+            name: 'proxy-connection-event',
+            ...event
+        });
+    }
+
     /**
      * Sends event to the external application.
      *

modules/API/external/external_api.js

     'outgoing-message': 'outgoingMessage',
     'participant-joined': 'participantJoined',
     'participant-left': 'participantLeft',
+    'proxy-connection-event': 'proxyConnectionEvent',
     'video-ready-to-close': 'readyToClose',
     'video-conference-joined': 'videoConferenceJoined',
     'video-conference-left': 'videoConferenceLeft',
         eventList.forEach(event => this.removeEventListener(event));
     }
 
+    /**
+     * Passes an event along to the local conference participant to establish
+     * or update a direct peer connection. This is currently used for developing
+     * wireless screensharing with room integration and it is advised against to
+     * use as its api may change.
+     *
+     * @param {Object} event - An object with information to pass along.
+     * @param {Object} event.data - The payload of the event.
+     * @param {string} event.from - The jid of the sender of the event. Needed
+     * when a reply is to be sent regarding the event.
+     * @returns {void}
+     */
+    sendProxyConnectionEvent(event) {
+        this._transport.sendEvent({
+            data: [ event ],
+            name: 'proxy-connection-event'
+        });
+    }
+
     /**
      * Returns the configuration for electron for the windows that are open
      * from Jitsi Meet.