mozilla-central/testing/web-platform/tests/largest-contentful-paint/web-font-styled-text-resize-swap-subnode.html

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Test Info: Warnings

<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
@font-face {
font-family: 'ADTestFaceSwapSubnode';
src: url('/fonts/AD.woff?pipe=trickle(d0.5)');
font-display: swap;
}
.test {
font-family: 'ADTestFaceSwapSubnode';
}
</style>
<!--
Web-font styled subnode text that gets resized during swap period should make
a LCP emission if the new size is larger than the existing LCP element size.
-->
<div class="test">
<span>LCP: Web Font Styled Text Resize</span>
</div>
<script>
function LCPEntryList() {
return new Promise(resolve => {
let = lcpEntries = [];
new PerformanceObserver((entryList, observer) => {
lcpEntries = lcpEntries.concat(entryList.getEntries());
if (lcpEntries.length == 2) {
resolve(lcpEntries);
observer.disconnect();
}
}).observe({ type: 'largest-contentful-paint', buffered: true });
});
}
promise_test(async t => {
await document.fonts.ready;
// Verify web font is downloaded.
assert_own_property(window, 'PerformanceResourceTiming', "ResourceTiming not supported");
let url = '/fonts/AD.woff?pipe=trickle(d0.5)';
var absoluteURL = new URL(url, location.href).href;
assert_equals(performance.getEntriesByName(absoluteURL).length, 1, 'Web font\
should be downloaded');
// Verify web font is available.
assert_true(document.fonts.check('16px ADTestFaceSwapSubnode'), 'Font should be the web font added');
let entryList = await LCPEntryList();
// Verify there are 2 LCP entries emitted.
assert_equals(entryList.length, 2, 'There should be 2 LCP entries. The 1st one corresponds to the system font and the 2nd the web font.')
// Verify the size of 2nd LCP entry is larger than that of the 1st one.
assert_greater_than(entryList[1].size, entryList[0].size, 'The size of 2nd LCP entry should be larger than that of the 1st one.');
}, "LCP should be updated if the web font styled text resizes to be larger during the swap period");
</script>