// ==UserScript==
// @name        Simple Curtain
// @namespace   *
// @description Hide tab contents
// @author      deep-purple from LOR
// @license     GPLv3
// @include     *
// @version     0.0.1-alpha
// @grant       none
// ==/UserScript==

var curtainConfig = {
    key   : 17, // 16 = Shift, 17 = Ctrl
    image : '//herogamesworld.com/images/my%20little%20pony%20games.jpg',
    style : {
        position           : 'fixed',
        zIndex             : 999999,
        top                : 0,
        bottom             : 0,
        left               : 0,
        right              : 0,
        backgroundColor    : 'rgba(255, 255, 255, 0.5)',
        backgroundPosition : 'center center',
        backgroundRepeat   : 'no-repeat',
        backgroundSize     : 'cover',
        backgroundImage    : 'url(###)'
    }
};


(function() {


    addEvent(window, 'load', function() {
        var
            body       = document.querySelector('body'),
            curtain    = document.createElement('div'),
            preloadImg = document.createElement('img'),
            i;

        preloadImg.style.position = 'absolute';
        preloadImg.style.top      = '-100000px';
        preloadImg.style.left     = '-100000px';
        preloadImg.src            = curtainConfig.image;
        body.appendChild(preloadImg);
        for (i in curtainConfig.style) {
            if (i == 'backgroundImage') {
                curtain.style[i] = curtainConfig.style[i]
                    .replace(/###/, curtainConfig.image);
            } else {
                curtain.style[i] = curtainConfig.style[i];
            }
        }
        curtain._hasVisible   = false;
        curtain.style.display = 'none';
        body.appendChild(curtain);
        addEvent(window, 'keydown', function(e) {
            if (e.keyCode == curtainConfig.key) {
                curtain._hasVisible = !curtain._hasVisible;
                if (curtain._hasVisible) {
                    curtain.style.display = 'block';
                } else {
                    curtain.style.display = 'none';
                }
            }
        });
    });


    function addEvent(elem, type, fn, params)
    {
        var callback = function(e) {
            fn(e || window.event, params);
        };
        if (elem.addEventListener) {
            elem.addEventListener(type, callback, false);
        } else if (elem.attachEvent) {
            elem.attachEvent('on' + type, callback);
        }
    }


}());

image : '//herogamesworld.com/images/my%20little%20pony%20games.jpg',