57 lines
2.1 KiB
HTML
57 lines
2.1 KiB
HTML
<!DOCTYPE HTML>
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<meta charset=utf-8>
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<title>Largest Contentful Paint: largest image is reported.</title>
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<body>
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<script src="/resources/testharness.js"></script>
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<script src="/resources/testharnessreport.js"></script>
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<script src="resources/largest-contentful-paint-helpers.js"></script>
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<!-- There is some text and some images. We care about lcp-133x106.png being reported, as it is the largest. -->
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<p>This is some text! :)</p>
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<img src='' id='lcp1' />
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<img src='' id='lcp2' />
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<img src='' id='lcp3' />
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<p>More text!</p>
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<script>
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// Add listener for load event that is fired when image is loaded.
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function image_load_promise(image_element) {
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return new Promise(resolve => {
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image_element.addEventListener('load', resolve);
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});
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}
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promise_test(async (t) => {
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assert_implements(window.LargestContentfulPaint, "LargestContentfulPaint is not implemented");
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let promise = image_load_promise(document.getElementById('lcp1'));
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document.getElementById('lcp1').src = '/images/lcp-100x50.png';
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await promise;
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const beforeLoad = performance.now();
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promise = image_load_promise(document.getElementById('lcp2'));
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document.getElementById('lcp2').src = '/images/lcp-133x106.png';
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await promise;
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promise = image_load_promise(document.getElementById('lcp3'));
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document.getElementById('lcp3').src = '/images/lcp-100x50-alt.png';
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await promise;
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const observer = new PerformanceObserver(
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t.step_func(entryList => {
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entryList.getEntries().forEach(entry => {
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// The text or other image could be reported as LCP if it is rendered before the larger image.
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if (entry.id !== 'lcp2')
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return;
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const url = window.location.origin + '/images/lcp-133x106.png';
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const size = 133 * 106;
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checkImage(entry, url, 'lcp2', size, beforeLoad);
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t.done();
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})
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})
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);
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observer.observe({ type: 'largest-contentful-paint', buffered: true });
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}, 'Largest Contentful Paint: largest image is reported.');
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</script>
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</body>
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