snapshot of https://github.com/jitsi/jitsi-meet.git @ fd1749dd28f4138aa80234fc7f311b19aaffa0e7 (2026-09-15)

react/features/base/lastn/middleware.ts

@@ -0,0 +1,92 @@
+import { debounce } from 'lodash-es';
+
+import { IStore } from '../../app/types';
+import { SET_FILMSTRIP_ENABLED } from '../../filmstrip/actionTypes';
+import { APP_STATE_CHANGED } from '../../mobile/background/actionTypes';
+import {
+    SET_CAR_MODE,
+    VIRTUAL_SCREENSHARE_REMOTE_PARTICIPANTS_UPDATED
+} from '../../video-layout/actionTypes';
+import { CONFERENCE_JOINED } from '../conference/actionTypes';
+import { SET_LOW_BANDWIDTH_MODE } from '../low-bandwidth-mode/actionTypes';
+import { getParticipantById } from '../participants/functions';
+import MiddlewareRegistry from '../redux/MiddlewareRegistry';
+
+import { setLastN } from './actions';
+import logger from './logger';
+
+/**
+ * Updates the last N value in the conference based on the current state of the redux store.
+ *
+ * @param {Store} store - The redux store.
+ * @private
+ * @returns {void}
+ */
+const _updateLastN = debounce(({ dispatch, getState }: IStore) => {
+    const state = getState();
+    const { conference } = state['features/base/conference'];
+
+    if (!conference) {
+        logger.debug('There is no active conference, not updating last N');
+
+        return;
+    }
+
+    const { enabled: audioOnly } = state['features/base/low-bandwidth-mode'];
+    const { appState } = state['features/mobile/background'] || {};
+    const { enabled: filmStripEnabled } = state['features/filmstrip'];
+    const config = state['features/base/config'];
+    const { carMode } = state['features/video-layout'];
+
+    // Select the (initial) lastN value based on the following preference order.
+    // 1. The last-n value from 'startLastN' if it is specified in config.js
+    // 2. The last-n value from 'channelLastN' if specified in config.js.
+    // 3. -1 as the default value.
+    let lastNSelected = config.startLastN ?? (config.channelLastN ?? -1);
+
+    // Because this is shared, on web appState is always undefined,
+    // meaning that it is never active
+    if (navigator.product === 'ReactNative' && (appState !== 'active' || carMode)) {
+        lastNSelected = 0;
+    } else if (audioOnly) {
+        const { remoteScreenShares, tileViewEnabled } = state['features/video-layout'];
+        const largeVideoParticipantId = state['features/large-video'].participantId;
+        const largeVideoParticipant
+            = largeVideoParticipantId ? getParticipantById(state, largeVideoParticipantId) : undefined;
+
+        // Use tileViewEnabled state from redux here instead of determining if client should be in tile
+        // view since we make an exception only for screenshare when in audio-only mode. If the user unpins
+        // the screenshare, lastN will be set to 0 here. It will be set to 1 if screenshare has been auto pinned.
+        if (!tileViewEnabled && largeVideoParticipant && !largeVideoParticipant.local) {
+            lastNSelected = (remoteScreenShares || []).includes(largeVideoParticipantId ?? '') ? 1 : 0;
+        } else {
+            lastNSelected = 0;
+        }
+    } else if (!filmStripEnabled) {
+        lastNSelected = 1;
+    }
+
+    const { lastN } = state['features/base/lastn'];
+
+    if (lastN !== lastNSelected) {
+        dispatch(setLastN(lastNSelected));
+    }
+}, 1000); /* Don't send this more often than once a second. */
+
+
+MiddlewareRegistry.register(store => next => action => {
+    const result = next(action);
+
+    switch (action.type) {
+    case APP_STATE_CHANGED:
+    case CONFERENCE_JOINED:
+    case SET_LOW_BANDWIDTH_MODE:
+    case SET_CAR_MODE:
+    case SET_FILMSTRIP_ENABLED:
+    case VIRTUAL_SCREENSHARE_REMOTE_PARTICIPANTS_UPDATED:
+        _updateLastN(store);
+        break;
+    }
+
+    return result;
+});