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