scratch-vm/src/blocks/scratch3_event.js

const Cast = require('../util/cast');

const Scratch3EventBlocks = function (runtime) {
    /**
     * The runtime instantiating this block package.
     * @type {Runtime}
     */
    this.runtime = runtime;
};

/**
 * Retrieve the block primitives implemented by this package.
 * @return {object.<string, Function>} Mapping of opcode to Function.
 */
Scratch3EventBlocks.prototype.getPrimitives = function () {
    return {
        event_broadcast: this.broadcast,
        event_broadcastandwait: this.broadcastAndWait,
        event_whengreaterthan: this.hatGreaterThanPredicate
    };
};

Scratch3EventBlocks.prototype.getHats = function () {
    return {
        event_whenflagclicked: {
            restartExistingThreads: true
        },
        event_whenkeypressed: {
            restartExistingThreads: false
        },
        event_whenthisspriteclicked: {
            restartExistingThreads: true
        },
        event_whenbackdropswitchesto: {
            restartExistingThreads: true
        },
        event_whengreaterthan: {
            restartExistingThreads: false,
            edgeActivated: true
        },
        event_whenbroadcastreceived: {
            restartExistingThreads: true
        }
    };
};

Scratch3EventBlocks.prototype.hatGreaterThanPredicate = function (args, util) {
    const option = Cast.toString(args.WHENGREATERTHANMENU).toLowerCase();
    const value = Cast.toNumber(args.VALUE);
    // @todo: Other cases :)
    if (option === 'timer') {
        return util.ioQuery('clock', 'projectTimer') > value;
    }
    return false;
};

Scratch3EventBlocks.prototype.broadcast = function (args, util) {
    const broadcastOption = Cast.toString(args.BROADCAST_OPTION);
    util.startHats('event_whenbroadcastreceived', {
        BROADCAST_OPTION: broadcastOption
    });
};

Scratch3EventBlocks.prototype.broadcastAndWait = function (args, util) {
    const broadcastOption = Cast.toString(args.BROADCAST_OPTION);
    // Have we run before, starting threads?
    if (!util.stackFrame.startedThreads) {
        // No - start hats for this broadcast.
        util.stackFrame.startedThreads = util.startHats(
            'event_whenbroadcastreceived', {
                BROADCAST_OPTION: broadcastOption
            }
        );
        if (util.stackFrame.startedThreads.length === 0) {
            // Nothing was started.
            return;
        }
    }
    // We've run before; check if the wait is still going on.
    const instance = this;
    const waiting = util.stackFrame.startedThreads.some(thread => instance.runtime.isActiveThread(thread));
    if (waiting) {
        util.yield();
    }
};

module.exports = Scratch3EventBlocks;