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<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src=/resources/testdriver.js></script>
<script src=/resources/testdriver-actions.js></script>
<script src=/resources/testdriver-vendor.js></script>
<style></style>
<!--
Web-font styled text that gets resized after an interaction stops LCP
observation should not make a new LCP emission.
-->
<textarea id='input'></textarea>
<div class="test">LCP: Web Font Styled Text Resize</div>
<script>
function addCSSRules() {
styleSheet = document.styleSheets[0];
fontRuleSet = "@font-face {\
font-family: 'ADTestFaceInteraction';\
src: url('/fonts/AD.woff');\
font-display: swap;\
}";
fontAtRule = ".test {\
font-family: 'ADTestFaceInteraction';\
} ";
styleSheet.insertRule(fontRuleSet);
styleSheet.insertRule(fontAtRule);
}
function LCPEntryList(t) {
return new Promise(resolve => {
let = lcpEntries = [];
new PerformanceObserver((entryList, observer) => {
lcpEntries = lcpEntries.concat(entryList.getEntries());
if (lcpEntries) {
// Adding timeout to wait a bit more so that if there are more than
// expected LCP entries emitted, they can be observed.
t.step_timeout(() => {
resolve(lcpEntries);
observer.disconnect();
}, 200);
}
}).observe({ type: 'largest-contentful-paint', buffered: true });
});
}
promise_test(async t => {
await document.fonts.ready;
let system_font_size = document.getElementsByClassName('test')[0].offsetHeight;
// Verify an LCP entry is emitted.
let entryList = await LCPEntryList(t);
assert_equals(entryList.length, 1, 'Text with system font should make a LCP emission.');
let lcpEntryBeforeInteraction = entryList[0];
// Add event listener so that CSS rule would be added after there's an
// input.
let inputElement = document.getElementById('input');
inputElement.addEventListener('keydown', addCSSRules);
// Send key as input.
await test_driver.send_keys(inputElement, 'k');
// Wait for web font to load.
await document.fonts.ready;
// Verify web font is downloaded.
assert_own_property(window, 'PerformanceResourceTiming', "ResourceTiming not supported");
let url = '/fonts/AD.woff';
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 ADTestFaceInteraction'), 'Font should be the web font added');
// Verify web font is applied.
let web_font_size = document.getElementsByClassName('test')[0].offsetHeight;
assert_not_equals(web_font_size, system_font_size, 'Web font swap should happen');
// Assert there is only 1 LCP entry, which verifies the added web font does
// not make a new LCP entry after an input.
entryList = await LCPEntryList(t);
assert_equals(entryList.length, 1, 'Text with system font should not make a LCP emission.');
// Verify the LCP entry is the same one emitted before interaction by
// asserting the size is the same.
assert_equals(lcpEntryBeforeInteraction.size, entryList[0].size, 'There should be only 1 LCP entry emitted.');
}, "LCP should be not updated if the web font styled text resize occurs after an interaction happens");
</script>
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