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Test Info: Warnings
- This test has a WPT meta file that expects 1 subtest issues.
- This WPT test may be referenced by the following Test IDs:
- /element-timing/observe-multiple-images.html - WPT Dashboard Interop Dashboard
<!DOCTYPE HTML>
<meta charset=utf-8>
<title>Element Timing: multiple images</title>
<body>
<style>
body {
margin: 0;
}
#img1 {
display: block;
margin-left: auto;
margin-right: auto;
}
#img2 {
margin-top:150px;
margin-left:50px;
}
</style>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="resources/element-timing-helpers.js"></script>
<script>
let beforeRender, image1Observed=0, image2Observed=0, image3Observed=0;
async_test(function (t) {
assert_implements(window.PerformanceElementTiming, "PerformanceElementTiming is not implemented");
const observer = new PerformanceObserver(
t.step_func(function(entryList) {
entryList.getEntries().forEach( entry => {
if (entry.identifier === 'image1') {
if (image1Observed) {
assert_unreached("Observer received image1 more than once");
t.done();
}
image1Observed = 1;
const pathname1 = window.location.origin + '/element-timing/resources/square100.png';
// The images do not contain ID, so expect an empty ID.
checkElement(entry, pathname1, 'image1', 'img1', beforeRender,
document.getElementById('img1'));
// This image is horizontally centered.
// Using abs and comparing to 1 because the viewport sizes could be odd.
// If a size is odd, then image cannot be in the pure center, but left
// and right should still be very close to their estimated coordinates.
assert_less_than_equal(Math.abs(entry.intersectionRect.left -
(document.documentElement.clientWidth / 2 - 50)), 1,
'left of rect for image1');
assert_less_than_equal(Math.abs(entry.intersectionRect.right -
(document.documentElement.clientWidth / 2 + 50)), 1,
'right of rect for image1');
assert_equals(entry.intersectionRect.top, 0, 'top of rect for image1');
assert_equals(entry.intersectionRect.bottom,
100, 'bottom of rect for image1');
checkNaturalSize(entry, 100, 100);
}
else if (entry.identifier === 'image2') {
if (image2Observed) {
assert_unreached("Observer received image2 more than once");
t.done();
}
image2Observed = 1;
const pathname2 = window.location.origin + '/element-timing/resources/square20.png';
checkElement(entry, pathname2, 'image2', 'img2', beforeRender,
document.getElementById('img2'));
// This image should be below image 1, and should respect the margin.
checkRect(entry, [50, 250, 250, 450], "of image2");
checkNaturalSize(entry, 20, 20);
}
else if (entry.identifier === 'image3') {
if (image3Observed) {
assert_unreached("Observer received image3 more than once");
t.done();
}
image3Observed = 1;
const pathname3 = window.location.origin + '/element-timing/resources/circle.svg';
checkElement(entry, pathname3, 'image3', 'img3', beforeRender,
document.getElementById('img3'));
// This image is just to the right of image2.
checkRect(entry, [250, 450, 250, 450], "of image3");
checkNaturalSize(entry, 200, 200);
}
else {
assert_unreached("Received an unexpected identifier.");
t.done();
}
if (image1Observed && image2Observed && image3Observed) {
t.done();
}
});
})
);
observer.observe({entryTypes: ['element']});
function addImage(number, source, width=0) {
const img = document.createElement('img');
img.src = source;
// Set a different id and elementtiming value for each image.
img.id = 'img' + number;
img.setAttribute('elementtiming', 'image' + number);
if (width !== 0)
img.width = width;
document.body.appendChild(img);
}
// Add the images during onload to be sure that the observer is registered in
// time to observe the element timing.
window.onload = () => {
addImage(1, 'resources/square100.png');
// Use requestAnimationFrame and a timeout to ensure that the images are
// processed in the order we want.
requestAnimationFrame( () => {
t.step_timeout( () => {
// Set the size equal to that of image3 to make positioning easier.
addImage(2, 'resources/square20.png', 200);
requestAnimationFrame( () => {
t.step_timeout( () => {
addImage(3, 'resources/circle.svg');
}, 0);
});
}, 0);
});
beforeRender = performance.now();
};
}, 'PerformanceObserver can observe multiple image elements.');
</script>
</body>