lazy load doesnt work with hidden elements - image

Question

this is my simple test code for lazy load
http://codepen.io/kevkev/pen/bVVGdE
it works so far .. but the thing is that hidden images in an onclick function for buttons etc. doesnt work!
(watch through my code and scroll to end and push the button)
you can see in the network feedback that it already had load the images.
i could figure out that the problem is "display:none"
.pop {
display:none;
z-index:99;
position:absolute;
width:100%;
height:auto;
background:inherit;
}

Answer 1

Because display: none; elements are unknown in position. And the lazyloader doesn't know, when and if you change this. Therefore it decides to eager load it. If you want a lazyloader that automatically detects this use https://github.com/aFarkas/lazysizes/.

Answer 2

As alternative I would recommend justlazy, because it's more lightweight and don't uses jQuery.
1. Define placeholder (similar to that what you have done):
<span data-src="path/to/image" data-alt="alt" data-title="title"
class="placeholder">
</span>
2. Initialize lazy loading after your button click:
$(document).ready(function () {
$("#art").click(function () {
$("#art_pop").fadeIn(300);
Justlazy.registerLazyLoadByClass("placeholder", {
// image will be loaded if it is 300 pixels
// below the lower display border
threshold: 300
});
});
// other code ..
});

Answer 3

thanks guys! but I also got a working solution on this:
http://codepen.io/kevkev/full/meebpQ/
$(document).ready(function () {
$("#art").click(function () {
$("#art_pop").fadeIn(300);
});
$(".pop > span, .pop").click(function () {
$(".pop").fadeOut(600);
});
});
;(function($) {
$.fn.unveil = function(threshold, callback) {
var $w = $(window),
th = threshold || 0,
retina = window.devicePixelRatio > 1,
attrib = retina? "data-src-retina" : "data-src",
images = this,
loaded;
this.one("unveil", function() {
var source = this.getAttribute(attrib);
source = source || this.getAttribute("data-src");
if (source) {
this.setAttribute("src", source);
if (typeof callback === "function") callback.call(this);
}
});
function unveil() {
var inview = images.filter(function() {
var $e = $(this);
if ($e.is(":hidden")) return;
var wt = $w.scrollTop(),
wb = wt + $w.height(),
et = $e.offset().top,
eb = et + $e.height();
return eb >= wt - th && et <= wb + th;
});
loaded = inview.trigger("unveil");
images = images.not(loaded);
}
$w.on("scroll.unveil resize.unveil lookup.unveil", unveil);
unveil();
return this;
};
})(window.jQuery || window.Zepto);
/* OWN JAVASCRIPT */
$(document).ready(function() {
$("img").unveil(200, function() {
$(this).load(function() {
this.style.opacity = 1;
});
});
});