Tampermonkey script to work around issues with SpeedSolving forum hotkeys

speedsolving-hotkey-fixer.js

// ==UserScript==
// @name         SpeedSolving Hotkey Fixer
// @namespace    https://voltara.org/
// @version      0.1
// @description  Work around glitchy SpeedSolving forum hotkeys
// @author       Voltara
// @match        https://www.speedsolving.com/forum/*
// @grant        none
// ==/UserScript==

// Replaces Alt-0 .. Alt-9 with Ctrl-0 .. Ctrl-9 to avoid conflicting with browser tab switching
// Use keypress modifiers instead of keyup modifiers
// Blocks spurious keyup events

(function() {
    'use strict';

    var modmask = function (e) {
        return (e.ctrlKey && 1) | (e.shiftKey && 2) | (e.altKey && 4) | (e.metaKey && 8);
    }

    var keys = { }, busy = false;

    document.addEventListener("keypress", function (e) {
        if (e.key < "0" || e.key > "9") {
            return;
        }
        keys[e.key] = modmask(e);
    }, true);

    document.addEventListener("keyup", function (e) {
        if (busy) {
            return;
        }

        if (e.key < "0" || e.key > "9") {
            return;
        }

        var m0 = keys[e.key], m = modmask(e);
        keys[e.key] = undefined;

        // block spurious keyup
        if (m0 == undefined) {
            e.stopPropagation();
            return;
        }

        // block altKey
        if (m0 & 4) {
            e.stopPropagation();
            return;
        }

        // convert ctrlKey to altKey
        if (m0 == 1 && (m == 0 || m == 1)) {
            var ei = { };
            for (var key in e) {
                ei[key] = e[key];
            }
            ei.ctrlKey = false;
            ei.altKey = true;

            e.stopPropagation();
            busy = true;
            e.target.dispatchEvent(new KeyboardEvent('keyup', ei));
            busy = false;
        }
    }, true);
})();