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Diffstat (limited to 'plugins/jetpack/modules/lazy-images/js/lazy-images.js')
| -rw-r--r-- | plugins/jetpack/modules/lazy-images/js/lazy-images.js | 870 |
1 files changed, 870 insertions, 0 deletions
diff --git a/plugins/jetpack/modules/lazy-images/js/lazy-images.js b/plugins/jetpack/modules/lazy-images/js/lazy-images.js new file mode 100644 index 00000000..31286bd3 --- /dev/null +++ b/plugins/jetpack/modules/lazy-images/js/lazy-images.js @@ -0,0 +1,870 @@ +/* globals IntersectionObserver, jQuery */ + +var jetpackLazyImagesModule = function( $ ) { + var images, + config = { + // If the image gets within 200px in the Y axis, start the download. + rootMargin: '200px 0px', + threshold: 0.01 + }, + imageCount = 0, + observer, + image, + i; + + $( document ).ready( function() { + lazy_load_init(); + + // Lazy load images that are brought in from Infinite Scroll + $( 'body' ).bind( 'post-load', lazy_load_init ); + + // Add event to provide optional compatibility for other code. + $( 'body' ).bind( 'jetpack-lazy-images-load', lazy_load_init ); + } ); + + function lazy_load_init() { + images = document.querySelectorAll( 'img.jetpack-lazy-image:not(.jetpack-lazy-image--handled)' ); + imageCount = images.length; + + // If initialized, then disconnect the observer + if ( observer ) { + observer.disconnect(); + } + + // If we don't have support for intersection observer, loads the images immediately + if ( ! ( 'IntersectionObserver' in window ) ) { + loadImagesImmediately( images ); + } else { + // It is supported, load the images + observer = new IntersectionObserver( onIntersection, config ); + + // foreach() is not supported in IE + for ( i = 0; i < images.length; i++ ) { + image = images[ i ]; + if ( image.getAttribute( 'data-lazy-loaded' ) ) { + continue; + } + + observer.observe( image ); + } + } + } + + /** + * Load all of the images immediately + * @param {NodeListOf<Element>} immediateImages List of lazy-loaded images to load immediately. + */ + function loadImagesImmediately( immediateImages ) { + var i; + + // foreach() is not supported in IE + for ( i = 0; i < immediateImages.length; i++ ) { + var image = immediateImages[ i ]; + applyImage( image ); + } + } + + /** + * On intersection + * @param {array} entries List of elements being observed. + */ + function onIntersection( entries ) { + var i; + + // Disconnect if we've already loaded all of the images + if ( imageCount === 0 ) { + observer.disconnect(); + } + + // Loop through the entries + for ( i = 0; i < entries.length; i++ ) { + var entry = entries[ i ]; + + // Are we in viewport? + if ( entry.intersectionRatio > 0 ) { + imageCount--; + + // Stop watching and load the image + observer.unobserve( entry.target ); + applyImage( entry.target ); + } + } + } + + /** + * Apply the image + * @param {object} image The image object. + */ + function applyImage( image ) { + var theImage = $( image ), + srcset, + sizes, + theClone; + + if ( ! theImage.length ) { + return; + } + + srcset = theImage.attr( 'data-lazy-srcset' ); + sizes = theImage.attr( 'data-lazy-sizes' ); + theClone = theImage.clone(); + + // Remove lazy attributes from the clone. + theClone.removeAttr( 'data-lazy-srcset' ), + theClone.removeAttr( 'data-lazy-sizes' ); + theClone.removeAttr( 'data-lazy-src' ); + + // Add the attributes we want on the finished image. + theClone.addClass( 'jetpack-lazy-image--handled' ); + theClone.attr( 'data-lazy-loaded', 1 ); + if ( ! srcset ) { + theClone.removeAttr( 'srcset' ); + } else { + theClone.attr( 'srcset', srcset ); + } + if ( sizes ) { + theClone.attr( 'sizes', sizes ); + } + + theImage.replaceWith( theClone ); + + // Fire an event so that third-party code can perform actions after an image is loaded. + theClone.trigger( 'jetpack-lazy-loaded-image' ); + } +}; + +/** + * The following is an Intersection observer polyfill which is licensed under + * the W3C SOFTWARE AND DOCUMENT NOTICE AND LICENSE and can be found at: + * https://github.com/w3c/IntersectionObserver/tree/master/polyfill + */ + +/* jshint ignore:start */ +/** + * Copyright 2016 Google Inc. All Rights Reserved. + * + * Licensed under the W3C SOFTWARE AND DOCUMENT NOTICE AND LICENSE. + * + * https://www.w3.org/Consortium/Legal/2015/copyright-software-and-document + * + */ + +(function(window, document) { + 'use strict'; + + + // Exits early if all IntersectionObserver and IntersectionObserverEntry + // features are natively supported. + if ('IntersectionObserver' in window && + 'IntersectionObserverEntry' in window && + 'intersectionRatio' in window.IntersectionObserverEntry.prototype) { + + // Minimal polyfill for Edge 15's lack of `isIntersecting` + // See: https://github.com/w3c/IntersectionObserver/issues/211 + if (!('isIntersecting' in window.IntersectionObserverEntry.prototype)) { + Object.defineProperty(window.IntersectionObserverEntry.prototype, + 'isIntersecting', { + get: function () { + return this.intersectionRatio > 0; + } + }); + } + return; + } + + + /** + * An IntersectionObserver registry. This registry exists to hold a strong + * reference to IntersectionObserver instances currently observering a target + * element. Without this registry, instances without another reference may be + * garbage collected. + */ + var registry = []; + + + /** + * Creates the global IntersectionObserverEntry constructor. + * https://w3c.github.io/IntersectionObserver/#intersection-observer-entry + * @param {Object} entry A dictionary of instance properties. + * @constructor + */ + function IntersectionObserverEntry(entry) { + this.time = entry.time; + this.target = entry.target; + this.rootBounds = entry.rootBounds; + this.boundingClientRect = entry.boundingClientRect; + this.intersectionRect = entry.intersectionRect || getEmptyRect(); + this.isIntersecting = !!entry.intersectionRect; + + // Calculates the intersection ratio. + var targetRect = this.boundingClientRect; + var targetArea = targetRect.width * targetRect.height; + var intersectionRect = this.intersectionRect; + var intersectionArea = intersectionRect.width * intersectionRect.height; + + // Sets intersection ratio. + if (targetArea) { + this.intersectionRatio = intersectionArea / targetArea; + } else { + // If area is zero and is intersecting, sets to 1, otherwise to 0 + this.intersectionRatio = this.isIntersecting ? 1 : 0; + } + } + + + /** + * Creates the global IntersectionObserver constructor. + * https://w3c.github.io/IntersectionObserver/#intersection-observer-interface + * @param {Function} callback The function to be invoked after intersection + * changes have queued. The function is not invoked if the queue has + * been emptied by calling the `takeRecords` method. + * @param {Object=} opt_options Optional configuration options. + * @constructor + */ + function IntersectionObserver(callback, opt_options) { + + var options = opt_options || {}; + + if (typeof callback != 'function') { + throw new Error('callback must be a function'); + } + + if (options.root && options.root.nodeType != 1) { + throw new Error('root must be an Element'); + } + + // Binds and throttles `this._checkForIntersections`. + this._checkForIntersections = throttle( + this._checkForIntersections.bind(this), this.THROTTLE_TIMEOUT); + + // Private properties. + this._callback = callback; + this._observationTargets = []; + this._queuedEntries = []; + this._rootMarginValues = this._parseRootMargin(options.rootMargin); + + // Public properties. + this.thresholds = this._initThresholds(options.threshold); + this.root = options.root || null; + this.rootMargin = this._rootMarginValues.map(function(margin) { + return margin.value + margin.unit; + }).join(' '); + } + + + /** + * The minimum interval within which the document will be checked for + * intersection changes. + */ + IntersectionObserver.prototype.THROTTLE_TIMEOUT = 100; + + + /** + * The frequency in which the polyfill polls for intersection changes. + * this can be updated on a per instance basis and must be set prior to + * calling `observe` on the first target. + */ + IntersectionObserver.prototype.POLL_INTERVAL = null; + + /** + * Use a mutation observer on the root element + * to detect intersection changes. + */ + IntersectionObserver.prototype.USE_MUTATION_OBSERVER = true; + + + /** + * Starts observing a target element for intersection changes based on + * the thresholds values. + * @param {Element} target The DOM element to observe. + */ + IntersectionObserver.prototype.observe = function(target) { + var isTargetAlreadyObserved = this._observationTargets.some(function(item) { + return item.element == target; + }); + + if (isTargetAlreadyObserved) { + return; + } + + if (!(target && target.nodeType == 1)) { + throw new Error('target must be an Element'); + } + + this._registerInstance(); + this._observationTargets.push({element: target, entry: null}); + this._monitorIntersections(); + this._checkForIntersections(); + }; + + + /** + * Stops observing a target element for intersection changes. + * @param {Element} target The DOM element to observe. + */ + IntersectionObserver.prototype.unobserve = function(target) { + this._observationTargets = + this._observationTargets.filter(function(item) { + + return item.element != target; + }); + if (!this._observationTargets.length) { + this._unmonitorIntersections(); + this._unregisterInstance(); + } + }; + + + /** + * Stops observing all target elements for intersection changes. + */ + IntersectionObserver.prototype.disconnect = function() { + this._observationTargets = []; + this._unmonitorIntersections(); + this._unregisterInstance(); + }; + + + /** + * Returns any queue entries that have not yet been reported to the + * callback and clears the queue. This can be used in conjunction with the + * callback to obtain the absolute most up-to-date intersection information. + * @return {Array} The currently queued entries. + */ + IntersectionObserver.prototype.takeRecords = function() { + var records = this._queuedEntries.slice(); + this._queuedEntries = []; + return records; + }; + + + /** + * Accepts the threshold value from the user configuration object and + * returns a sorted array of unique threshold values. If a value is not + * between 0 and 1 and error is thrown. + * @private + * @param {Array|number=} opt_threshold An optional threshold value or + * a list of threshold values, defaulting to [0]. + * @return {Array} A sorted list of unique and valid threshold values. + */ + IntersectionObserver.prototype._initThresholds = function(opt_threshold) { + var threshold = opt_threshold || [0]; + if (!Array.isArray(threshold)) threshold = [threshold]; + + return threshold.sort().filter(function(t, i, a) { + if (typeof t != 'number' || isNaN(t) || t < 0 || t > 1) { + throw new Error('threshold must be a number between 0 and 1 inclusively'); + } + return t !== a[i - 1]; + }); + }; + + + /** + * Accepts the rootMargin value from the user configuration object + * and returns an array of the four margin values as an object containing + * the value and unit properties. If any of the values are not properly + * formatted or use a unit other than px or %, and error is thrown. + * @private + * @param {string=} opt_rootMargin An optional rootMargin value, + * defaulting to '0px'. + * @return {Array<Object>} An array of margin objects with the keys + * value and unit. + */ + IntersectionObserver.prototype._parseRootMargin = function(opt_rootMargin) { + var marginString = opt_rootMargin || '0px'; + var margins = marginString.split(/\s+/).map(function(margin) { + var parts = /^(-?\d*\.?\d+)(px|%)$/.exec(margin); + if (!parts) { + throw new Error('rootMargin must be specified in pixels or percent'); + } + return {value: parseFloat(parts[1]), unit: parts[2]}; + }); + + // Handles shorthand. + margins[1] = margins[1] || margins[0]; + margins[2] = margins[2] || margins[0]; + margins[3] = margins[3] || margins[1]; + + return margins; + }; + + + /** + * Starts polling for intersection changes if the polling is not already + * happening, and if the page's visibilty state is visible. + * @private + */ + IntersectionObserver.prototype._monitorIntersections = function() { + if (!this._monitoringIntersections) { + this._monitoringIntersections = true; + + // If a poll interval is set, use polling instead of listening to + // resize and scroll events or DOM mutations. + if (this.POLL_INTERVAL) { + this._monitoringInterval = setInterval( + this._checkForIntersections, this.POLL_INTERVAL); + } + else { + addEvent(window, 'resize', this._checkForIntersections, true); + addEvent(document, 'scroll', this._checkForIntersections, true); + + if (this.USE_MUTATION_OBSERVER && 'MutationObserver' in window) { + this._domObserver = new MutationObserver(this._checkForIntersections); + this._domObserver.observe(document, { + attributes: true, + childList: true, + characterData: true, + subtree: true + }); + } + } + } + }; + + + /** + * Stops polling for intersection changes. + * @private + */ + IntersectionObserver.prototype._unmonitorIntersections = function() { + if (this._monitoringIntersections) { + this._monitoringIntersections = false; + + clearInterval(this._monitoringInterval); + this._monitoringInterval = null; + + removeEvent(window, 'resize', this._checkForIntersections, true); + removeEvent(document, 'scroll', this._checkForIntersections, true); + + if (this._domObserver) { + this._domObserver.disconnect(); + this._domObserver = null; + } + } + }; + + + /** + * Scans each observation target for intersection changes and adds them + * to the internal entries queue. If new entries are found, it + * schedules the callback to be invoked. + * @private + */ + IntersectionObserver.prototype._checkForIntersections = function() { + var rootIsInDom = this._rootIsInDom(); + var rootRect = rootIsInDom ? this._getRootRect() : getEmptyRect(); + + this._observationTargets.forEach(function(item) { + var target = item.element; + var targetRect = getBoundingClientRect(target); + var rootContainsTarget = this._rootContainsTarget(target); + var oldEntry = item.entry; + var intersectionRect = rootIsInDom && rootContainsTarget && + this._computeTargetAndRootIntersection(target, rootRect); + + var newEntry = item.entry = new IntersectionObserverEntry({ + time: now(), + target: target, + boundingClientRect: targetRect, + rootBounds: rootRect, + intersectionRect: intersectionRect + }); + + if (!oldEntry) { + this._queuedEntries.push(newEntry); + } else if (rootIsInDom && rootContainsTarget) { + // If the new entry intersection ratio has crossed any of the + // thresholds, add a new entry. + if (this._hasCrossedThreshold(oldEntry, newEntry)) { + this._queuedEntries.push(newEntry); + } + } else { + // If the root is not in the DOM or target is not contained within + // root but the previous entry for this target had an intersection, + // add a new record indicating removal. + if (oldEntry && oldEntry.isIntersecting) { + this._queuedEntries.push(newEntry); + } + } + }, this); + + if (this._queuedEntries.length) { + this._callback(this.takeRecords(), this); + } + }; + + + /** + * Accepts a target and root rect computes the intersection between then + * following the algorithm in the spec. + * TODO(philipwalton): at this time clip-path is not considered. + * https://w3c.github.io/IntersectionObserver/#calculate-intersection-rect-algo + * @param {Element} target The target DOM element + * @param {Object} rootRect The bounding rect of the root after being + * expanded by the rootMargin value. + * @return {?Object} The final intersection rect object or undefined if no + * intersection is found. + * @private + */ + IntersectionObserver.prototype._computeTargetAndRootIntersection = + function(target, rootRect) { + + // If the element isn't displayed, an intersection can't happen. + if (window.getComputedStyle(target).display == 'none') return; + + var targetRect = getBoundingClientRect(target); + var intersectionRect = targetRect; + var parent = getParentNode(target); + var atRoot = false; + + while (!atRoot) { + var parentRect = null; + var parentComputedStyle = parent.nodeType == 1 ? + window.getComputedStyle(parent) : {}; + + // If the parent isn't displayed, an intersection can't happen. + if (parentComputedStyle.display == 'none') return; + + if (parent == this.root || parent == document) { + atRoot = true; + parentRect = rootRect; + } else { + // If the element has a non-visible overflow, and it's not the <body> + // or <html> element, update the intersection rect. + // Note: <body> and <html> cannot be clipped to a rect that's not also + // the document rect, so no need to compute a new intersection. + if (parent != document.body && + parent != document.documentElement && + parentComputedStyle.overflow != 'visible') { + parentRect = getBoundingClientRect(parent); + } + } + + // If either of the above conditionals set a new parentRect, + // calculate new intersection data. + if (parentRect) { + intersectionRect = computeRectIntersection(parentRect, intersectionRect); + + if (!intersectionRect) break; + } + parent = getParentNode(parent); + } + return intersectionRect; + }; + + + /** + * Returns the root rect after being expanded by the rootMargin value. + * @return {Object} The expanded root rect. + * @private + */ + IntersectionObserver.prototype._getRootRect = function() { + var rootRect; + if (this.root) { + rootRect = getBoundingClientRect(this.root); + } else { + // Use <html>/<body> instead of window since scroll bars affect size. + var html = document.documentElement; + var body = document.body; + rootRect = { + top: 0, + left: 0, + right: html.clientWidth || body.clientWidth, + width: html.clientWidth || body.clientWidth, + bottom: html.clientHeight || body.clientHeight, + height: html.clientHeight || body.clientHeight + }; + } + return this._expandRectByRootMargin(rootRect); + }; + + + /** + * Accepts a rect and expands it by the rootMargin value. + * @param {Object} rect The rect object to expand. + * @return {Object} The expanded rect. + * @private + */ + IntersectionObserver.prototype._expandRectByRootMargin = function(rect) { + var margins = this._rootMarginValues.map(function(margin, i) { + return margin.unit == 'px' ? margin.value : + margin.value * (i % 2 ? rect.width : rect.height) / 100; + }); + var newRect = { + top: rect.top - margins[0], + right: rect.right + margins[1], + bottom: rect.bottom + margins[2], + left: rect.left - margins[3] + }; + newRect.width = newRect.right - newRect.left; + newRect.height = newRect.bottom - newRect.top; + + return newRect; + }; + + + /** + * Accepts an old and new entry and returns true if at least one of the + * threshold values has been crossed. + * @param {?IntersectionObserverEntry} oldEntry The previous entry for a + * particular target element or null if no previous entry exists. + * @param {IntersectionObserverEntry} newEntry The current entry for a + * particular target element. + * @return {boolean} Returns true if a any threshold has been crossed. + * @private + */ + IntersectionObserver.prototype._hasCrossedThreshold = + function(oldEntry, newEntry) { + + // To make comparing easier, an entry that has a ratio of 0 + // but does not actually intersect is given a value of -1 + var oldRatio = oldEntry && oldEntry.isIntersecting ? + oldEntry.intersectionRatio || 0 : -1; + var newRatio = newEntry.isIntersecting ? + newEntry.intersectionRatio || 0 : -1; + + // Ignore unchanged ratios + if (oldRatio === newRatio) return; + + for (var i = 0; i < this.thresholds.length; i++) { + var threshold = this.thresholds[i]; + + // Return true if an entry matches a threshold or if the new ratio + // and the old ratio are on the opposite sides of a threshold. + if (threshold == oldRatio || threshold == newRatio || + threshold < oldRatio !== threshold < newRatio) { + return true; + } + } + }; + + + /** + * Returns whether or not the root element is an element and is in the DOM. + * @return {boolean} True if the root element is an element and is in the DOM. + * @private + */ + IntersectionObserver.prototype._rootIsInDom = function() { + return !this.root || containsDeep(document, this.root); + }; + + + /** + * Returns whether or not the target element is a child of root. + * @param {Element} target The target element to check. + * @return {boolean} True if the target element is a child of root. + * @private + */ + IntersectionObserver.prototype._rootContainsTarget = function(target) { + return containsDeep(this.root || document, target); + }; + + + /** + * Adds the instance to the global IntersectionObserver registry if it isn't + * already present. + * @private + */ + IntersectionObserver.prototype._registerInstance = function() { + if (registry.indexOf(this) < 0) { + registry.push(this); + } + }; + + + /** + * Removes the instance from the global IntersectionObserver registry. + * @private + */ + IntersectionObserver.prototype._unregisterInstance = function() { + var index = registry.indexOf(this); + if (index != -1) registry.splice(index, 1); + }; + + + /** + * Returns the result of the performance.now() method or null in browsers + * that don't support the API. + * @return {number} The elapsed time since the page was requested. + */ + function now() { + return window.performance && performance.now && performance.now(); + } + + + /** + * Throttles a function and delays its executiong, so it's only called at most + * once within a given time period. + * @param {Function} fn The function to throttle. + * @param {number} timeout The amount of time that must pass before the + * function can be called again. + * @return {Function} The throttled function. + */ + function throttle(fn, timeout) { + var timer = null; + return function () { + if (!timer) { + timer = setTimeout(function() { + fn(); + timer = null; + }, timeout); + } + }; + } + + + /** + * Adds an event handler to a DOM node ensuring cross-browser compatibility. + * @param {Node} node The DOM node to add the event handler to. + * @param {string} event The event name. + * @param {Function} fn The event handler to add. + * @param {boolean} opt_useCapture Optionally adds the even to the capture + * phase. Note: this only works in modern browsers. + */ + function addEvent(node, event, fn, opt_useCapture) { + if (typeof node.addEventListener == 'function') { + node.addEventListener(event, fn, opt_useCapture || false); + } + else if (typeof node.attachEvent == 'function') { + node.attachEvent('on' + event, fn); + } + } + + + /** + * Removes a previously added event handler from a DOM node. + * @param {Node} node The DOM node to remove the event handler from. + * @param {string} event The event name. + * @param {Function} fn The event handler to remove. + * @param {boolean} opt_useCapture If the event handler was added with this + * flag set to true, it should be set to true here in order to remove it. + */ + function removeEvent(node, event, fn, opt_useCapture) { + if (typeof node.removeEventListener == 'function') { + node.removeEventListener(event, fn, opt_useCapture || false); + } + else if (typeof node.detatchEvent == 'function') { + node.detatchEvent('on' + event, fn); + } + } + + + /** + * Returns the intersection between two rect objects. + * @param {Object} rect1 The first rect. + * @param {Object} rect2 The second rect. + * @return {?Object} The intersection rect or undefined if no intersection + * is found. + */ + function computeRectIntersection(rect1, rect2) { + var top = Math.max(rect1.top, rect2.top); + var bottom = Math.min(rect1.bottom, rect2.bottom); + var left = Math.max(rect1.left, rect2.left); + var right = Math.min(rect1.right, rect2.right); + var width = right - left; + var height = bottom - top; + + return (width >= 0 && height >= 0) && { + top: top, + bottom: bottom, + left: left, + right: right, + width: width, + height: height + }; + } + + + /** + * Shims the native getBoundingClientRect for compatibility with older IE. + * @param {Element} el The element whose bounding rect to get. + * @return {Object} The (possibly shimmed) rect of the element. + */ + function getBoundingClientRect(el) { + var rect; + + try { + rect = el.getBoundingClientRect(); + } catch (err) { + // Ignore Windows 7 IE11 "Unspecified error" + // https://github.com/w3c/IntersectionObserver/pull/205 + } + + if (!rect) return getEmptyRect(); + + // Older IE + if (!(rect.width && rect.height)) { + rect = { + top: rect.top, + right: rect.right, + bottom: rect.bottom, + left: rect.left, + width: rect.right - rect.left, + height: rect.bottom - rect.top + }; + } + return rect; + } + + + /** + * Returns an empty rect object. An empty rect is returned when an element + * is not in the DOM. + * @return {Object} The empty rect. + */ + function getEmptyRect() { + return { + top: 0, + bottom: 0, + left: 0, + right: 0, + width: 0, + height: 0 + }; + } + + /** + * Checks to see if a parent element contains a child elemnt (including inside + * shadow DOM). + * @param {Node} parent The parent element. + * @param {Node} child The child element. + * @return {boolean} True if the parent node contains the child node. + */ + function containsDeep(parent, child) { + var node = child; + while (node) { + if (node == parent) return true; + + node = getParentNode(node); + } + return false; + } + + + /** + * Gets the parent node of an element or its host element if the parent node + * is a shadow root. + * @param {Node} node The node whose parent to get. + * @return {Node|null} The parent node or null if no parent exists. + */ + function getParentNode(node) { + var parent = node.parentNode; + + if (parent && parent.nodeType == 11 && parent.host) { + // If the parent is a shadow root, return the host element. + return parent.host; + } + return parent; + } + + + // Exposes the constructors globally. + window.IntersectionObserver = IntersectionObserver; + window.IntersectionObserverEntry = IntersectionObserverEntry; + + }(window, document)); +/* jshint ignore:end */ + +// Let's kick things off now +jetpackLazyImagesModule( jQuery ); |