feat(screenshare): add auto pin of latest screen share (#4076)

interface_config.js

@@ -195,6 +195,12 @@ var interfaceConfig = {
      */
     // ANDROID_APP_PACKAGE: 'org.jitsi.meet',
 
+    /**
+     * A UX mode where the last screen share participant is automatically
+     * pinned. Note: this mode is experimental and subject to breakage.
+     */
+    // AUTO_PIN_LATEST_SCREEN_SHARE: false,
+
     /**
      * Override the behavior of some notifications to remain displayed until
      * explicitly dismissed through a user action. The value is how long, in

react/features/video-layout/actionTypes.js

@@ -1,3 +1,15 @@
+/**
+ * The type of the action which sets the list of known participant IDs which
+ * have an active screen share.
+ *
+ * @returns {{
+ *     type: SCREEN_SHARE_PARTICIPANTS_UPDATED,
+ *     participantIds: Array<string>
+ * }}
+ */
+export const SCREEN_SHARE_PARTICIPANTS_UPDATED
+    = 'SCREEN_SHARE_PARTICIPANTS_UPDATED';
+
 /**
  * The type of the action which enables or disables the feature for showing
  * video thumbnails in a two-axis tile view.

react/features/video-layout/actions.js

@@ -1,6 +1,27 @@
 // @flow
 
-import { SET_TILE_VIEW } from './actionTypes';
+import {
+    SCREEN_SHARE_PARTICIPANTS_UPDATED,
+    SET_TILE_VIEW
+} from './actionTypes';
+
+/**
+ * Creates a (redux) action which signals that the list of known participants
+ * with screen shares has changed.
+ *
+ * @param {string} participantIds - The participants which currently have active
+ * screen share streams.
+ * @returns {{
+ *     type: SCREEN_SHARE_PARTICIPANTS_UPDATED,
+ *     participantId: string
+ * }}
+ */
+export function setParticipantsWithScreenShare(participantIds: Array<string>) {
+    return {
+        type: SCREEN_SHARE_PARTICIPANTS_UPDATED,
+        participantIds
+    };
+}
 
 /**
  * Creates a (redux) action which signals to set the UI layout to be tiled view

react/features/video-layout/reducer.js

@@ -3,14 +3,30 @@
 import { ReducerRegistry } from '../base/redux';
 import { PersistenceRegistry } from '../base/storage';
 
-import { SET_TILE_VIEW } from './actionTypes';
+import {
+    SCREEN_SHARE_PARTICIPANTS_UPDATED,
+    SET_TILE_VIEW
+} from './actionTypes';
+
+const DEFAULT_STATE = {
+    screenShares: []
+};
 
 const STORE_NAME = 'features/video-layout';
 
-PersistenceRegistry.register(STORE_NAME);
+PersistenceRegistry.register(STORE_NAME, {
+    tileViewEnabled: true
+});
 
-ReducerRegistry.register(STORE_NAME, (state = {}, action) => {
+ReducerRegistry.register(STORE_NAME, (state = DEFAULT_STATE, action) => {
     switch (action.type) {
+    case SCREEN_SHARE_PARTICIPANTS_UPDATED: {
+        return {
+            ...state,
+            screenShares: action.participantIds
+        };
+    }
+
     case SET_TILE_VIEW:
         return {
             ...state,

react/features/video-layout/subscriber.js

@@ -4,9 +4,16 @@ import {
     VIDEO_QUALITY_LEVELS,
     setMaxReceiverVideoQuality
 } from '../base/conference';
-import { StateListenerRegistry } from '../base/redux';
+import {
+    getPinnedParticipant,
+    pinParticipant
+} from '../base/participants';
+import { StateListenerRegistry, equals } from '../base/redux';
 import { selectParticipant } from '../large-video';
 import { shouldDisplayTileView } from './functions';
+import { setParticipantsWithScreenShare } from './actions';
+
+declare var interfaceConfig: Object;
 
 /**
  * StateListenerRegistry provides a reliable way of detecting changes to
@@ -14,11 +21,89 @@ import { shouldDisplayTileView } from './functions';
  */
 StateListenerRegistry.register(
     /* selector */ state => shouldDisplayTileView(state),
-    /* listener */ (displayTileView, { dispatch }) => {
+    /* listener */ (displayTileView, store) => {
+        const { dispatch } = store;
+
         dispatch(selectParticipant());
 
         if (!displayTileView) {
-            dispatch(setMaxReceiverVideoQuality(VIDEO_QUALITY_LEVELS.HIGH));
+            dispatch(
+                setMaxReceiverVideoQuality(VIDEO_QUALITY_LEVELS.HIGH));
+
+            if (typeof interfaceConfig === 'object'
+                && interfaceConfig.AUTO_PIN_LATEST_SCREEN_SHARE) {
+                _updateAutoPinnedParticipant(store);
+            }
+        }
+    }
+);
+
+/**
+ * For auto-pin mode, listen for changes to the known media tracks and look
+ * for updates to screen shares.
+ */
+StateListenerRegistry.register(
+    /* selector */ state => state['features/base/tracks'],
+    /* listener */ (tracks, store) => {
+        if (typeof interfaceConfig !== 'object'
+            && !interfaceConfig.AUTO_PIN_LATEST_SCREEN_SHARE) {
+            return;
+        }
+
+        const oldScreenSharesOrder
+            = store.getState()['features/video-layout'].screenShares || [];
+        const knownSharingParticipantIds = tracks.reduce((acc, track) => {
+            if (track.mediaType === 'video' && track.videoType === 'desktop') {
+                acc.push(track.participantId);
+            }
+
+            return acc;
+        }, []);
+
+        // Filter out any participants which are no longer screen sharing
+        // by looping through the known sharing participants and removing any
+        // participant IDs which are no longer sharing.
+        const newScreenSharesOrder = oldScreenSharesOrder.filter(
+            participantId => knownSharingParticipantIds.includes(participantId));
+
+        // Make sure all new sharing participant get added to the end of the
+        // known screen shares.
+        knownSharingParticipantIds.forEach(participantId => {
+            if (!newScreenSharesOrder.includes(participantId)) {
+                newScreenSharesOrder.push(participantId);
+            }
+        });
+
+        if (!equals(oldScreenSharesOrder, newScreenSharesOrder)) {
+            store.dispatch(
+                setParticipantsWithScreenShare(newScreenSharesOrder));
+
+            _updateAutoPinnedParticipant(store);
         }
     }
 );
+
+/**
+ * Private helper to automatically pin the latest screen share stream or unpin
+ * if there are no more screen share streams.
+ *
+ * @param {Store} store - The redux store.
+ * @returns {void}
+ */
+function _updateAutoPinnedParticipant({ dispatch, getState }) {
+    const state = getState();
+    const screenShares = state['features/video-layout'].screenShares;
+
+    if (!screenShares) {
+        return;
+    }
+
+    const latestScreenshareParticipantId
+        = screenShares[screenShares.length - 1];
+
+    if (latestScreenshareParticipantId) {
+        dispatch(pinParticipant(latestScreenshareParticipantId));
+    } else if (getPinnedParticipant(state['features/base/participants'])) {
+        dispatch(pinParticipant(null));
+    }
+}