SingleFile/lib/hooks/hooks-frame.js

/*
 * Copyright 2010-2019 Gildas Lormeau
 * contact : gildas.lormeau <at> gmail.com
 * 
 * This file is part of SingleFile.
 *
 *   The code in this file is free software: you can redistribute it and/or 
 *   modify it under the terms of the GNU Affero General Public License 
 *   (GNU AGPL) as published by the Free Software Foundation, either version 3
 *   of the License, or (at your option) any later version.
 * 
 *   The code in this file is distributed in the hope that it will be useful, 
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of 
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero 
 *   General Public License for more details.
 *
 *   As additional permission under GNU AGPL version 3 section 7, you may 
 *   distribute UNMODIFIED VERSIONS OF THIS file without the copy of the GNU 
 *   AGPL normally required by section 4, provided you include this license 
 *   notice and a URL through which recipients can access the Corresponding 
 *   Source.
 */

/* global browser, window, addEventListener, dispatchEvent, CustomEvent, document, HTMLDocument, FileReader, Blob, screen, Element, UIEvent */

this.hooksFrame = this.hooksFrame || (() => {

	const LOAD_DEFERRED_IMAGES_START_EVENT = "single-file-load-deferred-images-start";
	const LOAD_DEFERRED_IMAGES_END_EVENT = "single-file-load-deferred-images-end";
	const LOAD_IMAGE_EVENT = "single-file-load-image";
	const IMAGE_LOADED_EVENT = "single-file-image-loaded";
	const NEW_FONT_FACE_EVENT = "single-file-new-font-face";
	const fontFaces = [];

	if (document instanceof HTMLDocument) {
		let scriptElement = document.createElement("script");
		scriptElement.src = browser.runtime.getURL("/lib/hooks/hooks-web.js");
		(document.documentElement || document).appendChild(scriptElement);
		scriptElement.remove();
		scriptElement = document.createElement("script");
		scriptElement.textContent = `(${hook.toString()})(${JSON.stringify({ LOAD_DEFERRED_IMAGES_START_EVENT, LOAD_DEFERRED_IMAGES_END_EVENT, NEW_FONT_FACE_EVENT })})`;
		(document.documentElement || document).appendChild(scriptElement);
		scriptElement.remove();
		addEventListener(NEW_FONT_FACE_EVENT, event => fontFaces.push(event.detail));
	}

	return {
		getFontsData: () => fontFaces,
		loadDeferredImagesStart: () => dispatchEvent(new CustomEvent(LOAD_DEFERRED_IMAGES_START_EVENT)),
		loadDeferredImagesEnd: () => dispatchEvent(new CustomEvent(LOAD_DEFERRED_IMAGES_END_EVENT)),
		LOAD_IMAGE_EVENT,
		IMAGE_LOADED_EVENT
	};

	function hook(constants) {
		const {
			LOAD_DEFERRED_IMAGES_START_EVENT,
			LOAD_DEFERRED_IMAGES_END_EVENT,
			NEW_FONT_FACE_EVENT
		} = constants;
		const FONT_STYLE_PROPERTIES = {
			family: "font-family",
			style: "font-style",
			weight: "font-weight",
			stretch: "font-stretch",
			unicodeRange: "unicode-range",
			variant: "font-variant",
			featureSettings: "font-feature-settings"
		};

		const requestAnimationFrame = window.requestAnimationFrame;
		const cancelAnimationFrame = window.cancelAnimationFrame;
		const observers = new Map();
		const observedElements = new Map();
		let loadDeferredImages;

		addEventListener(LOAD_DEFERRED_IMAGES_START_EVENT, () => {
			loadDeferredImages = true;
			const docBoundingRect = document.documentElement.getBoundingClientRect();
			Array.from(observers).forEach(([intersectionObserver, observer]) => {
				const rootBoundingRect = observer.options.root && observer.options.root.getBoundingClientRect();
				observer.callback(observedElements.get(intersectionObserver).map(target => {
					const boundingClientRect = target.getBoundingClientRect();
					const isIntersecting = true;
					const intersectionRatio = 1;
					const rootBounds = observer.options && observer.options.root ? rootBoundingRect : docBoundingRect;
					const time = 0;
					return { target, intersectionRatio, boundingClientRect, intersectionRect: boundingClientRect, isIntersecting, rootBounds, time };
				}), intersectionObserver);
			});
			if (pendingRequestAnimationFrameCalls.size) {
				Array.from(pendingRequestAnimationFrameCalls).forEach(([id, callback]) => {
					cancelAnimationFrame(id);
					callback();
				});
			}
		});

		addEventListener(LOAD_DEFERRED_IMAGES_END_EVENT, () => {
			loadDeferredImages = false;
		});

		let warningRequestAnimationFrameDisplayed;
		const pendingRequestAnimationFrameCalls = new Map();
		let lastTimestamp = 0;
		let errorDetected;
		window.requestAnimationFrame = function (callback) {
			if (!warningRequestAnimationFrameDisplayed) {
				console.warn("SingleFile is hooking the requestAnimationFrame and cancelAnimationFrame functions to load deferred images."); // eslint-disable-line no-console
				warningRequestAnimationFrameDisplayed = true;
			}
			let requestId;
			if (loadDeferredImages && !errorDetected) {
				try {
					requestId = 0;
					callback(lastTimestamp);
				} catch (error) {
					errorDetected = true;
					requestId = requestAnimationFrame(timestamp => {
						lastTimestamp = timestamp;
						callback(timestamp);
					});
				}
			} else {
				if (!loadDeferredImages) {
					errorDetected = false;
				}
				requestId = requestAnimationFrame(timestamp => {
					pendingRequestAnimationFrameCalls.delete(requestId);
					lastTimestamp = timestamp;
					callback(timestamp);
				});
				pendingRequestAnimationFrameCalls.set(requestId, callback);
			}
			return requestId;
		};
		window.requestAnimationFrame.toString = function () { return "requestAnimationFrame() { [native code] }"; };

		window.cancelAnimationFrame = function (requestId) {
			pendingRequestAnimationFrameCalls.delete(requestId);
			return cancelAnimationFrame(requestId);
		};
		window.cancelAnimationFrame.toString = function () { return "cancelAnimationFrame() { [native code] }"; };

		if (window.FontFace) {
			const FontFace = window.FontFace;
			let warningFontFaceDisplayed;
			window.FontFace = function () {
				if (!warningFontFaceDisplayed) {
					console.warn("SingleFile is hooking the FontFace constructor to get font URLs."); // eslint-disable-line no-console
					warningFontFaceDisplayed = true;
				}
				const detail = {};
				detail["font-family"] = arguments[0];
				detail.src = arguments[1];
				const descriptors = arguments[2];
				if (descriptors) {
					Object.keys(descriptors).forEach(descriptor => {
						if (FONT_STYLE_PROPERTIES[descriptor]) {
							detail[FONT_STYLE_PROPERTIES[descriptor]] = descriptors[descriptor];
						}
					});
				}
				if (detail.src instanceof ArrayBuffer) {
					const reader = new FileReader();
					reader.readAsDataURL(new Blob([detail.src]));
					reader.addEventListener("load", () => {
						detail.src = "url(" + reader.result + ")";
						dispatchEvent(new CustomEvent(NEW_FONT_FACE_EVENT, { detail }));
					});
				} else {
					dispatchEvent(new CustomEvent(NEW_FONT_FACE_EVENT, { detail }));
				}
				return new FontFace(...arguments);
			};
			window.FontFace.toString = function () { return "function FontFace() { [native code]"; };
		}

		if (window.IntersectionObserver) {
			const IntersectionObserver = window.IntersectionObserver;
			const observeIntersection = IntersectionObserver.prototype.observe;
			const unobserveIntersection = IntersectionObserver.prototype.unobserve;
			let warningIntersectionObserverDisplayed;
			window.IntersectionObserver = function () {
				if (!warningIntersectionObserverDisplayed) {
					console.warn("SingleFile is hooking the IntersectionObserver API to detect and load deferred images."); // eslint-disable-line no-console
					warningIntersectionObserverDisplayed = true;
				}
				const intersectionObserver = new IntersectionObserver(...arguments);
				const callback = arguments[0];
				const options = arguments[1];
				intersectionObserver.observe = function (targetElement) {
					let targetElements = observedElements.get(intersectionObserver);
					if (!targetElements) {
						targetElements = [];
						observedElements.set(intersectionObserver, targetElements);
					}
					targetElements.push(targetElement);
					return observeIntersection.call(intersectionObserver, targetElement);
				};
				intersectionObserver.unobserve = function (targetElement) {
					let targetElements = observedElements.get(intersectionObserver);
					if (targetElements) {
						targetElements = targetElements.filter(element => element <= targetElement);
						if (targetElements.length) {
							observedElements.set(intersectionObserver, targetElements);
						} else {
							observedElements.delete(intersectionObserver);
						}
					}
					return unobserveIntersection.call(intersectionObserver, targetElement);
				};
				observers.set(intersectionObserver, { callback, options });
				return intersectionObserver;
			};
			window.IntersectionObserver.toString = function () { return "function IntersectionObserver() { [native code]"; };
		}
	}

})();