75 lines
2.4 KiB
HTML
75 lines
2.4 KiB
HTML
<!DOCTYPE HTML>
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<meta charset=utf-8>
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<title>Largest Contentful Paint: src change triggers new entry.</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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<img src='' id='image_id' />
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<script>
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setup({ "hide_test_state": true });
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let first_image_src = '/images/black-rectangle.png';
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let second_image_src = '/images/blue.png';
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let image_id = 'image_id';
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// Add listener for load event that is fired when image is loaded.
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const 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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// Create a promise that resolves when an LCP is observed.
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const lcp_observation_promise = image_src => {
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return new Promise(resolve => {
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new PerformanceObserver((entryList) => {
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let lcpEntry = entryList.getEntries().find(e => e.url.includes(image_src));
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if (lcpEntry) {
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resolve(lcpEntry);
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}
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}).observe({ type: 'largest-contentful-paint' });
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});
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}
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const loadImageAndGetLCPEntry = async image_src => {
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let LCPObserverPromise = lcp_observation_promise(image_src);
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let image_element = document.getElementById(image_id);
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let promise = image_load_promise(image_element);
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image_element.src = image_src;
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await promise;
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return await LCPObserverPromise;
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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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// Load first image.
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let beforeLoad = performance.now();
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let first_LCP = await loadImageAndGetLCPEntry(first_image_src);
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// Verify first LCP entry correctness. The black-rectangle.png is 100 x 50.
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checkImage(first_LCP, window.location.origin + first_image_src, image_id, 100 * 50, beforeLoad);
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// Load second image.
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beforeLoad = performance.now();
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let second_LCP = await loadImageAndGetLCPEntry(second_image_src);
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// Verify second LCP entry correctness. The blue.png is 133 by 106.
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checkImage(second_LCP, window.location.origin + second_image_src, image_id, 133 * 106, beforeLoad);
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}, 'Largest Contentful Paint: changing src causes a new entry to be dispatched.');
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</script>
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</body>
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