fix(filmstrip) Make dominant speaker visible at all times (#11874)

* fix(filmstrip) Make dominant speaker visible at all times.

* squash: address review comments.

react/features/base/participants/functions.js

@@ -46,6 +46,59 @@ const AVATAR_CHECKER_FUNCTIONS = [
 ];
 /* eslint-enable arrow-body-style, no-unused-vars */
 
+/**
+ * Returns the list of active speakers that should be moved to the top of the sorted list of participants so that the
+ * dominant speaker is visible always on the vertical filmstrip in stage layout.
+ *
+ * @param {Function | Object} stateful - The (whole) redux state, or redux's {@code getState} function to be used to
+ * retrieve the state.
+ * @returns {Array<string>}
+ */
+export function getActiveSpeakersToBeDisplayed(stateful: Object | Function) {
+    const state = toState(stateful);
+    const {
+        fakeParticipants,
+        sortedRemoteScreenshares,
+        sortedRemoteVirtualScreenshareParticipants,
+        speakersList
+    } = state['features/base/participants'];
+    const { visibleRemoteParticipants } = state['features/filmstrip'];
+
+    // Do not re-sort the active speakers if all of them are currently visible.
+    if (typeof visibleRemoteParticipants === 'undefined' || speakersList.size <= visibleRemoteParticipants.size) {
+        return speakersList;
+    }
+    const activeSpeakers = new Map(speakersList);
+    let availableSlotsForActiveSpeakers = visibleRemoteParticipants.size;
+
+    // Remove screenshares from the count.
+    if (getMultipleVideoSupportFeatureFlag(state)) {
+        if (sortedRemoteVirtualScreenshareParticipants) {
+            availableSlotsForActiveSpeakers -= sortedRemoteVirtualScreenshareParticipants.size * 2;
+            for (const screenshare of Array.from(sortedRemoteVirtualScreenshareParticipants.keys())) {
+                const ownerId = getVirtualScreenshareParticipantOwnerId(screenshare);
+
+                activeSpeakers.delete(ownerId);
+            }
+        }
+    } else if (sortedRemoteScreenshares) {
+        availableSlotsForActiveSpeakers -= sortedRemoteScreenshares.size;
+        for (const id of Array.from(sortedRemoteScreenshares.keys())) {
+            activeSpeakers.delete(id);
+        }
+    }
+
+    // Remove shared video from the count.
+    if (fakeParticipants) {
+        availableSlotsForActiveSpeakers -= fakeParticipants.size;
+    }
+    const truncatedSpeakersList = Array.from(activeSpeakers).slice(0, availableSlotsForActiveSpeakers);
+
+    truncatedSpeakersList.sort((a, b) => a[1].localeCompare(b[1]));
+
+    return new Map(truncatedSpeakersList);
+}
+
 /**
  * Resolves the first loadable avatar URL for a participant.
  *

react/features/filmstrip/functions.any.js

@@ -1,7 +1,7 @@
 // @flow
 
-import { getSourceNameSignalingFeatureFlag } from '../base/config';
-import { getVirtualScreenshareParticipantOwnerId } from '../base/participants';
+import { getMultipleVideoSupportFeatureFlag } from '../base/config';
+import { getActiveSpeakersToBeDisplayed, getVirtualScreenshareParticipantOwnerId } from '../base/participants';
 
 import { setRemoteParticipants } from './actions';
 import { isFilmstripScrollVisible } from './functions';
@@ -34,42 +34,36 @@ export function updateRemoteParticipants(store: Object, participantId: ?number)
     const {
         fakeParticipants,
         sortedRemoteParticipants,
-        sortedRemoteScreenshares,
-        speakersList
+        sortedRemoteScreenshares
     } = state['features/base/participants'];
     const remoteParticipants = new Map(sortedRemoteParticipants);
     const screenShares = new Map(sortedRemoteScreenshares);
     const screenShareParticipants = sortedRemoteVirtualScreenshareParticipants
         ? [ ...sortedRemoteVirtualScreenshareParticipants.keys() ] : [];
     const sharedVideos = fakeParticipants ? Array.from(fakeParticipants.keys()) : [];
-    const speakers = new Map(speakersList);
+    const speakers = getActiveSpeakersToBeDisplayed(state);
 
-    if (getSourceNameSignalingFeatureFlag(state)) {
+    if (getMultipleVideoSupportFeatureFlag(state)) {
         for (const screenshare of screenShareParticipants) {
             const ownerId = getVirtualScreenshareParticipantOwnerId(screenshare);
 
             remoteParticipants.delete(ownerId);
             remoteParticipants.delete(screenshare);
-
-            speakers.delete(ownerId);
-            speakers.delete(screenshare);
         }
     } else {
         for (const screenshare of screenShares.keys()) {
             remoteParticipants.delete(screenshare);
-            speakers.delete(screenshare);
         }
     }
 
     for (const sharedVideo of sharedVideos) {
         remoteParticipants.delete(sharedVideo);
-        speakers.delete(sharedVideo);
     }
     for (const speaker of speakers.keys()) {
         remoteParticipants.delete(speaker);
     }
 
-    if (getSourceNameSignalingFeatureFlag(state)) {
+    if (getMultipleVideoSupportFeatureFlag(state)) {
         // Always update the order of the thumnails.
         const participantsWithScreenShare = screenShareParticipants.reduce((acc, screenshare) => {
             const ownerId = getVirtualScreenshareParticipantOwnerId(screenshare);