element-web/src/components/views/elements/effects/EffectsOverlay.tsx

import React, {FunctionComponent, useEffect, useRef} from 'react';
import dis from '../../../../dispatcher/dispatcher';
import ICanvasEffect from './ICanvasEffect.js';

type EffectsOverlayProps = {
    roomWidth: number;
}

const EffectsOverlay: FunctionComponent<EffectsOverlayProps> = ({roomWidth}) => {
    const canvasRef = useRef<HTMLCanvasElement>(null);
    const effectsRef = useRef<Map<String, ICanvasEffect>>(new Map<String, ICanvasEffect>());

    const resize = () => {
        canvasRef.current.height = window.innerHeight;
    };

    const lazyLoadEffectModule = async (name: string): Promise<ICanvasEffect> => {
        if(!name) return null;
        let effect = effectsRef.current[name] ?? null;
        if(effect === null) {
            try {
                var { default: Effect } = await import(`./${name}`);
                effect = new Effect();
                effectsRef.current[name] = effect;
            } catch (err) {
                console.warn('Unable to load effect module at \'./${name}\'.', err)
            }
        }
        return effect;
    }

    const onAction = (payload: { action: string }) => {
        const actionPrefix = 'effects.';
        if(payload.action.indexOf(actionPrefix) === 0) {
            const effect = payload.action.substr(actionPrefix.length);
            lazyLoadEffectModule(effect).then((module) => module?.start(canvasRef.current));
        }
    };

    // on mount
    useEffect(() => {
        const dispatcherRef = dis.register(onAction);
        const canvas = canvasRef.current;
        canvas.width = roomWidth;
        canvas.height = window.innerHeight;
        window.addEventListener('resize', resize, true);
        
        return () => {            
            dis.unregister(dispatcherRef);
            window.removeEventListener('resize', resize);
            for(const effect in effectsRef.current) {
                effectsRef.current[effect]?.stop();
            }
        };
    }, []);

    // on roomWidth change
    useEffect(() => {
        canvasRef.current.width = roomWidth;
    }, [roomWidth]);
    
    return (
        <canvas
            ref={canvasRef}
            style={{
                display: 'block',
                zIndex: 999999,
                pointerEvents: 'none',
                position: 'fixed',
                top: 0,
                right: 0,
            }}
        />
    )
}

export default EffectsOverlay;