Source code
Revision control
Copy as Markdown
Other Tools
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:
- /largest-contentful-paint/web-font-styled-text-resize-swap.html - WPT Dashboard Interop Dashboard
<!doctype html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
@font-face {
font-family: "ADTestFaceSwap";
src: url("/fonts/AD.woff?pipe=trickle(d0.5)");
font-display: swap;
}
.test {
font-family: "ADTestFaceSwap";
}
</style>
<!--
Web-font styled 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">LCP: Web Font Styled Text Resize</div>
<script>
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 ADTestFaceSwap"), "Font should be the web font added");
let lcpEntries = [];
await Promise.race([
new Promise((resolve, reject) => {
t.step_timeout(() => {
resolve(lcpEntries);
}, 3000);
}),
new Promise((resolve, reject) => {
new PerformanceObserver((list, observer) => {
lcpEntries.push(...list.getEntries());
if (lcpEntries.length >= 2) {
resolve();
observer.disconnect();
}
}).observe({ type: "largest-contentful-paint", buffered: true });
}),
]);
// Verify there are 2 LCP entries emitted.
assert_equals(
lcpEntries.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(
lcpEntries[1].size,
lcpEntries[0].size,
"The size of 2ndLCP 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>