<!DOCTYPEHTML>
<head>
<meta charset=utf-8>
<title>Element Timing: observe an image rendering an alternate picture source</title>
<style> body {
margin: 20px;
}
#square20 {
width: 80px;
height: 40px;
}
</style>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="resources/element-timing-helpers.js"></script>
<script>
async_test(function (t) {
let beforeRender;
let img;
assert_implements(window.PerformanceElementTiming, "PerformanceElementTiming is not implemented");
const observer = new PerformanceObserver(
t.step_func_done(function(entryList) {
assert_equals(entryList.getEntries().length, 1);
const entry = entryList.getEntries()[0];
// The reported element is the image node, but the image is the
// alternate source.
const pathname = window.location.origin + '/images/green-100x50.png';
checkElement(entry, pathname, 'my_image', 'square20', beforeRender, img);
// As we use a smaller viewport, the intersection size is smaller
checkRect(entry, [20, 100, 20, 60]);
checkNaturalSize(entry, 100, 50);
})
);
observer.observe({entryTypes: ['element']});
// We add the image during onload to be sure that the observer is registered
// in time for it to observe the element timing.
window.onload = () => {
// Add image of width equal to 100 and height equal to 50. Use a different
// color to verify the painted image is the alternate one.
picture = document.createElement('picture');
picture.id = 'rectangle';
picture.setAttribute('elementtiming', 'my_picture');
document.body.appendChild(picture);
beforeRender = performance.now();
};
}, 'Element with a rectangular image and an alternate picture image with precedence reports the correct image.');
</script>
</head>
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