maplibre-gl/src/source/rtl_text_plugin_main_thread.ts

BSD licensed community fork of mapbox-gl, a WebGL interactive maps library

import {browser} from '../util/browser.ts';
import {Event, Evented} from '../util/evented.ts';
import {warnOnce} from '../util/util.ts';
import {type RTLPluginStatus, RTLPluginLoadedEventName, type PluginState} from './rtl_text_plugin_status.ts';
import {type GlobalDispatcher, getGlobalDispatcher} from '../util/global_dispatcher.ts';
import {MessageType} from '../util/actor_messages.ts';

class RTLMainThreadPlugin extends Evented {
    status: RTLPluginStatus = 'unavailable';
    url: string = null;
    dispatcher: GlobalDispatcher = getGlobalDispatcher();

    constructor() {
        super();
        this.dispatcher.on('workerscreate', () => this._resyncWorkers());
    }

    /**
     * Re-syncs the plugin into freshly created workers. A `loading` plugin needs no re-sync: its
     * in-flight request targets the newest workers, and re-requesting would double-load the
     * script when the plugin's own broadcast is what created the workers.
     */
    async _resyncWorkers(): Promise<void> {
        try {
            if (this.status === 'deferred') {
                await this._syncState('deferred');
            } else if (this.status === 'loaded') {
                await this._requestImport();
            }
        } catch (error) {
            warnOnce(`Failed to load the RTL text plugin into the new workers: ${error}`);
        }
    }

    /** Sync RTL plugin state by broadcasting a message to the worker */
    _syncState(statusToSend: RTLPluginStatus): Promise<PluginState[]> {
        this.status = statusToSend;
        return this.dispatcher.broadcast(MessageType.syncRTLPluginState, {pluginStatus: statusToSend, pluginURL: this.url})
            .catch((e: any) => {
                this.status = 'error';
                throw e;
            });
    }

    /** This one is exposed to outside */
    getRTLTextPluginStatus(): RTLPluginStatus {
        return this.status;
    }

    clearRTLTextPlugin(): void {
        this.status = 'unavailable';
        this.url = null;
    }

    async setRTLTextPlugin(url: string, deferred: boolean = false): Promise<void> {
        if (this.url) {
            // error
            throw new Error('setRTLTextPlugin cannot be called multiple times.');
        }

        this.url = browser.resolveURL(url);
        if (!this.url) {
            throw new Error(`requested url ${url} is invalid`);
        }
        if (this.status === 'unavailable') {

            // from initial state:
            if (deferred) {

                this.status = 'deferred';
                // fire and forget: in this case it does not need wait for the broadcasting result
                // it is important to sync the deferred status once because
                // symbol_bucket will be checking it in worker
                this._syncState(this.status);

            } else {
                return this._requestImport();
            }

        } else if (this.status === 'requested') {
            return this._requestImport();
        }
    }

    /** Send a message to worker which will import the RTL plugin script */
    async _requestImport() : Promise<void> {

        // all errors/exceptions will be handled by _syncState
        await this._syncState('loading');
        this.status = 'loaded';
        this.fire(new Event(RTLPluginLoadedEventName));
    }

    /** Start a lazy loading process of RTL plugin */
    lazyLoad(): void {
        if (this.status === 'unavailable') {
            this.status = 'requested';
        } else if (this.status === 'deferred') {
            this._requestImport();
        }
    }
}

let rtlMainThreadPlugin: RTLMainThreadPlugin = null;

export function rtlMainThreadPluginFactory(): RTLMainThreadPlugin {
    rtlMainThreadPlugin ||= new RTLMainThreadPlugin();
    return rtlMainThreadPlugin;
}