42 lines
No EOL
2 KiB
HTML
42 lines
No EOL
2 KiB
HTML
<!DOCTYPE HTML>
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<meta charset=utf-8>
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<title>Largest Contentful Paint: Progressively Loaded Image</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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<script src="/common/get-host-info.sub.js"></script>
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<script>
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promise_test(async function (t) {
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assert_implements(window.LargestContentfulPaint, "LargestContentfulPaint is not implemented");
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const beforeLoad = performance.now();
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const observer = new PerformanceObserver(
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t.step_func_done(function(entryList) {
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assert_equals(entryList.getEntries().length, 1);
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const entry = entryList.getEntries()[0];
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const imgElement = document.getElementById('image_id');
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const imageSrc = imgElement.currentSrc;
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const imageWidth = imgElement.naturalWidth;
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const imageHeight = imgElement.naturalHeight;
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const size = imageWidth * imageHeight;
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const lcpLoadTime = entry.loadTime;
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const lcpRenderTime = entry.renderTime;
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const resLoadTime = calculateResourceLoadTime(imageSrc);
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assert_greater_than_equal(lcpLoadTime,resLoadTime,'Load before LCP event fired');
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assert_greater_than_equal(lcpRenderTime,resLoadTime,'Load before LCP event rendered');
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checkImage(entry, imageSrc, 'image_id', size, beforeLoad);
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})
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);
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observer.observe({type: 'largest-contentful-paint', buffered: true})
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}, 'Ensure Progressive JPEG LCP load and render events occur after resource loading');
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function calculateResourceLoadTime(imageSrc) {
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const entries = performance.getEntriesByName(imageSrc);
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const resourceEntry = entries[0];
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assert_equals(entries.length, 1, 'No Resource timing entry found');
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return resourceEntry.responseEnd;
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}
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</script>
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<img src='/images/computer.jpg?pipe=trickle(982:d1)' id='image_id'/>
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</body>
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</html> |