<!DOCTYPE html> <script src="/resources/testharness.js"></script> <script src="/resources/testharnessreport.js"></script> <style> @font-face { font-family: 'TestFaceSmaller'; src: url('/fonts/CSSTest/csstest-basic-regular.ttf?pipe=trickle(d0.5)'); size-adjust: 30%; font-display: swap; } .test { font-family: 'TestFaceSmaller'; } </style> <!-- Web-font styled text that gets resized during swap period should not make a LCP emission if the new size is smaller than the current LCP element size. --> <div class="test">LCP: Web Font Styled Text Resize</div> <script> 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; // Verify web font is loaded. assert_own_property(window, 'PerformanceResourceTiming', "ResourceTiming not supported"); let url = '/fonts/CSSTest/csstest-basic-regular.ttf?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('10px TestFaceSmaller'), 'Font should be the web font added'); // Verify there is only one LCP entry. let entryList = await LCPEntryList(t); assert_equals(entryList.length, 1, 'Web font styled text resize that occurs during swap period but is smaller should not make a new LCP emission.') }, "LCP should be not updated if the web font styled text resizes to be smaller during the swap period"); </script>