jitsi-meet/react/features/external-api/subscriber.js

// @flow

import { StateListenerRegistry } from '../base/redux';
import { shouldDisplayTileView } from '../video-layout';

declare var APP: Object;

/**
 * StateListenerRegistry provides a reliable way of detecting changes to
 * preferred layout state and dispatching additional actions.
 */
StateListenerRegistry.register(
    /* selector */ state => shouldDisplayTileView(state),
    /* listener */ displayTileView => {
        APP.API.notifyTileViewChanged(displayTileView);
    });