<!DOCTYPE HTML>
<meta charset=utf-8>
<title>Element Timing: observe element with background image in its first letter</title>
<body>
<style>
#target::first-letter {
background-image: url('/images/black-rectangle.png');
}
#target {
font-size: 12px;
}
</style>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="resources/element-timing-helpers.js"></script>
<script>
let beforeRender = performance.now();
async_test(function (t) {
assert_implements(window.PerformanceElementTiming, "PerformanceElementTiming is not implemented");
const div = document.getElementById('target');
let textObserved = false;
let imageObserved = false;
function calculateSize(entry) {
const ir = entry.intersectionRect;
return (ir.right - ir.left) * (ir.bottom - ir.top);
}
const observer = new PerformanceObserver(
t.step_func(function(entryList) {
entryList.getEntries().forEach(entry => {
if (entry.name === 'text-paint') {
checkTextElement(entry, 'my_div', 'target', beforeRender, div);
textObserved = true;
const size = calculateSize(entry);
// Assume average width is between 4px and 15px.
// Therefore, text size must be between 12 * (35*4) and 12 * (35*15).
assert_between_inclusive(size, 1680, 6300);
}
else {
assert_equals(entry.name, 'image-paint');
const pathname = window.location.origin + '/images/black-rectangle.png';
checkElement(entry, pathname, 'my_div', 'target', beforeRender, div);
checkNaturalSize(entry, 100, 50);
imageObserved = true;
const size = calculateSize(entry);
// Background image size should only be approximately the size of a single letter.
assert_between_inclusive(size, 48, 180);
}
});
if (textObserved && imageObserved)
t.done();
})
);
observer.observe({entryTypes: ['element']});
}, 'Element with elementtiming attribute and background image in first-letter is observable.');
</script>
<div id='target' elementtiming='my_div'>This is some text that I care about</div>
</body>
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