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                <h1>Late-load an animated gif and provide a pause button</h1>

<p>Improves initial page-load performance, and helps meet <abbr title="Web Content Accessibility Guidelines">WCAG</abbr> 2 level AA.</p>

<div class=container>
  <img class=img
       alt="Tesco's Bake Off Challenge - Challah bread">

<p>Initially load a static image (.jpg) then once the page has fully loaded, swap it out for the (much) larger animated gif.</p>
<p>A pause control is added which flips between the static image and the animation to meet WCAG 2 level AA. Which states a pause control is a requirement on animations which last longer than 5 seconds.</p>
<p>The animated gif is preloaded into memory then displayed preventing flashes of white occuring.</p>

<p>Sent for accessibility testing to the <a href="">Digital Accessibility Centre</a>. Tested as fully compliant 23/09/2016.</p>

<p>Code repo available on <a href="">GitHub</a>.</p>

<p class=smaller><a href="">Pens by Mike Foskett</a> &mdash; <a href="">webSemantics</a></p>

<svg style="display:none">
    <symbol viewBox="0 0 34 34" id="icon-play">
      <path d="M25 17.2l-14 7v-14l14 7z"></path>
    <symbol viewBox="0 0 34 34" id="icon-pause">
      <path d="M20 11h2v12h-2V11zm-8 0h2v12h-2V11z"></path>


                /* template override only */
button:focus {
  background-color: transparent;

/* Gif control */
.container {
.img {
  display: block;
  width: 100%;
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(1px, 1px, 1px, 1px);
.btn-anim {
  position: absolute;
  width: 36px;
  height: 36px;
  bottom: 12px;
  right: 12px;
  overflow: visible;

  cursor: pointer;
  padding: 0;
  border: 0 solid #fff;
  border-radius: 100%;

  /* IE10 - transparent background not allowed */
  background-color: rgba(255,255,255,.1);
.btn-anim:focus {
  outline: 0 solid;

.svg-pausePlay {
  pointer-events: none;
  width: 36px;
  height: 36px;
  border-radius: 100%;
  xxxoverflow: hidden;
  color: blue;
  background-color: #fff;
  fill: currentColor;
  -webkit-transition: all .3s ease-out;
  transition: all .3s ease-out;
.btn-anim:hover .svg-pausePlay,
.btn-anim:focus .svg-pausePlay {
  color: red;
  box-shadow: 0 0 0 4px red;


                var Gif_Load_Control = (function (window, d) {

    "use strict";

    // Wait until load event fires then go fetch large gifs.
    // On gif load replace the static jpg and add a pause button.
    // v1.2  - 27/09/2016
    //    To optimise verbalisation:
    //    Replaced ARIA and SVG titles with visually hidden text. 

    var dataAttr = "data-gif";

    var btnClass = "btn-anim";
    var btnOnClass = "btn-anim-on";

    var svgPlayIcon = "icon-play";
    var svgPauseIcon = "icon-pause";
    var svgClass = "svg-pausePlay";

    var txtPlay = "Play animation";
    var txtPause = "Pause animation";

    var _getSVG = function (icon, clss) {

        var svg = d.createElementNS("", "svg");

        svg.setAttribute("class", clss); // IE9 and Edge supported

        // Prevent IE focusing on SVG
        svg.setAttribute("focusable", "false");

        // Prevent "Graphic" from being spoken aloud by screen-reader
        svg.setAttribute("role", "presentational");

        var use = d.createElementNS("", "use");
        use.setAttributeNS("", "href", "#" + icon);
        return svg;
    var _getSpan = function (txt, clss) {
        var span = d.createElement("span");
        span.setAttribute("class", clss); // IE9 and Edge supported
        span.textContent = txt;
        return span;

    var _displayImage = function (newImg, origImg) {

        // Comment out requestAnimationFrame for IE9 support
        window.requestAnimationFrame(function () {
            origImg.src = newImg.src;


    var _toggleAnimation = function (e) {

        var target =;
        var origImg =;

        // Comment out requestAnimationFrame for IE9 support
        window.requestAnimationFrame(function () {

            if (origImg.src === origImg.staticSrc) {

                origImg.src = origImg.animatedSrc;
                // IE9+ support
                target.setAttribute("class", target.className + " " + btnOnClass);
                target.textContent = "";
                target.appendChild(_getSVG(svgPauseIcon, svgClass));
                target.appendChild(_getSpan(txtPause, "visually-hidden"));

            } else {

                origImg.src = origImg.staticSrc;

                // IE9+ support
                target.setAttribute("class", target.className.replace(" " + btnOnClass, ""));

                target.textContent = "";
                target.appendChild(_getSVG(svgPlayIcon, svgClass));
                target.appendChild(_getSpan(txtPlay, "visually-hidden"));

    var _addPauseBtn = function (origImg) {

        var parentObj = origImg.parentElement;
        var btn = d.createElement("button");

        btn.origImg = origImg;
        // IE9+ support
        btn.setAttribute("class", btnClass + " " + btnOnClass);
        // Some screen-readers have issue reading the SVG title - don't use.
        btn.appendChild(_getSVG(svgPauseIcon, svgClass));

        // An aria-title doesn't work in all scenarios - don't use.
        // Instead use a visually-hidden span to contain play/pause text
        btn.appendChild(_getSpan(txtPause, "visually-hidden"));

        btn.addEventListener("click", _toggleAnimation, false);


    var _requestImage = function (src, origImg) {

        var newImg = new Image();

        origImg.staticSrc = origImg.src;
        origImg.animatedSrc = src;

        newImg.addEventListener("load", function () {

            _displayImage(newImg, origImg);

        }, false);

        newImg.src = src;

    var initialise = function () {

        var imgs = d.querySelectorAll("[" + dataAttr + "]");
        var i = imgs.length;
        while (i--) {
            _requestImage(imgs[i].getAttribute(dataAttr), imgs[i]);

    // Just run initialise() if this script is post-loaded.
    window.addEventListener("load", initialise, false);

}(window, document));