Firefox Hide Scrollbars

Hide Scrollbars in Firefox
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// ==UserScript==
// @name         Firefox Hide Scrollbars
// @namespace    http://qashto.com/
// @version      2.1.8
// @description  Hide Scrollbars in Firefox
// @author       qashto
// @match        *://*/*
// @exclude      *://accounts.google.com/*
// @run-at       document-start
// @grant        GM_addStyle
// ==/UserScript==

console.log('hiding scrollbars...');

// if used as userscript add style with GM_addStyle
if (typeof GM_addStyle !== 'undefined') {
	GM_addStyle(`
    :root {
      --scrollbar-height: 0;
      --scrollbar-width: 0;
      height: 100vh !important;
      overflow: hidden !important;
      position: relative !important;
      width: 100vw !important;
    }

    :root,
    body {
      max-height: initial !important;
      max-width: initial !important;
      min-height: initial !important;
      min-width: initial !important;
      position: relative;
    }

    body {
      height: calc(100vh + var(--scrollbar-height)) !important;
      overflow: auto !important;
      width: calc(100vw + var(--scrollbar-width)) !important;
    }
  `);
}

/**
 * Compatibility with userscripts. Userscripts run in a different context to
 * content scripts and don't need to make structured clones to pass objects
 * to page scripts.
 */
if (!exportFunction && !cloneInto) {
	function exportFunction(func, targetScope, options = {}) {
		if (options.defineAs) {
			targetScope[options.defineAs] = func;
		}

		return func;
	}

	function cloneInto(obj) {
		return obj;
	}

	window.wrappedJSObject = window;


	// Userscript-specific definition of document getters/setters
	let documentScrollHandler;
	Object.defineProperties(Document.prototype, {
		scrollingElement: {
			get() {
				return document.body;
			}
		},
		onscroll: {
			get() {
				return documentScrollHandler;
			},
			set(listener) {
				if (documentScrollHandler) {
					document.body.removeEventListener("scroll", documentScrollHandler);
				}
				if (listener) {
					documentScrollHandler = listener;
					document.body.addEventListener('scroll', documentScrollHandler);
				}
			}
		}
	});
} else if (browser && browser.runtime && browser.runtime.id) {
	/**
	 * getters/setters cannot be passed via structured clone, so we have to inject
	 * a script into the page context.
	 */
	const scriptElement = document.createElement("script");
	scriptElement.src = browser.runtime.getURL("js/pageContext.js");
	scriptElement.addEventListener("load", () => {
		scriptElement.remove();
	});

	document.documentElement.appendChild(scriptElement);
}

function getScrollbarSize() {
	const div = document.createElement('div');
	div.style.visibility = 'hidden';
	div.style.overflow = 'scroll';
	document.documentElement.appendChild(div);

	const scrollbarHeight = div.offsetHeight - div.clientHeight;
	const scrollbarWidth = div.offsetWidth - div.clientWidth;

	div.remove();

	return [
		scrollbarWidth,
		scrollbarHeight
	];
}

document.addEventListener('DOMContentLoaded', () => {
	const [scrollbarWidth, scrollbarHeight] = getScrollbarSize();

	document.body.style.setProperty(
		'--scrollbar-height', `${scrollbarHeight}px`);
	document.body.style.setProperty(
		'--scrollbar-width', `${scrollbarWidth}px`);


	document.body.addEventListener('scroll', ev => {
		const scrollLeft = cloneInto(document.body.scrollLeft, window);
		const scrollTop = cloneInto(document.body.scrollTop, window);

		window.wrappedJSObject.scrollX = scrollLeft;
		window.wrappedJSObject.pageXOffset = scrollLeft;
		window.wrappedJSObject.scrollY = scrollTop;
		window.wrappedJSObject.pageYOffset = scrollTop;
	});

	exportFunction(document.body.scroll.bind(document.body), window, {
		defineAs: 'scroll'
	});
	exportFunction(document.body.scrollTo.bind(document.body), window, {
		defineAs: 'scrollTo'
	});
	exportFunction(document.body.scrollBy.bind(document.body), window, {
		defineAs: 'scrollBy'
	});
});

function handleAddScrollEvent() {
	if (arguments[0] === 'scroll') {
		document.body.addEventListener(...arguments);
		return;
	}
}

function handleRemoveScrollEvent() {
	if (arguments[0] === 'scroll') {
		document.body.removeEventListener(...arguments);
		return;
	}
}


const initial_windowAddEventListener = Window.prototype.addEventListener;
const initial_windowRemoveEventListener = Window.prototype.removeEventListener;
const initial_documentAddEventListener = Document.prototype.addEventListener;
const initial_documentRemoveEventListener = Document.prototype.removeEventListener;

function windowAddEventListener() {
	handleAddScrollEvent(...arguments);
	initial_windowAddEventListener.apply(this, arguments);
}

function windowRemoveEventListener() {
	handleRemoveScrollEvent(...arguments);
	initial_windowRemoveEventListener.apply(this, arguments);
}

function documentAddEventListener() {
	handleAddScrollEvent(...arguments);
	initial_documentAddEventListener.apply(this, arguments);
}

function documentRemoveEventListener() {
	handleRemoveScrollEvent(...arguments);
	initial_documentRemoveEventListener.apply(this, arguments);
}

exportFunction(windowAddEventListener, Window.prototype, {
	defineAs: 'addEventListener'
});
exportFunction(windowRemoveEventListener, Window.prototype, {
	defineAs: 'removeEventListener'
});
exportFunction(documentAddEventListener, Document.prototype, {
	defineAs: 'addEventListener'
});
exportFunction(documentRemoveEventListener, Document.prototype, {
	defineAs: 'removeEventListener'
});

console.log('scrollbars hidden!');