| <!DOCTYPE HTML> |
| <meta charset=utf-8> |
| <title>Largest Contentful Paint: size when image overflows</title> |
| <body> |
| <style> |
| body { |
| /* Preventing a scrollbar from showing and removing any margins simplifies |
| the calculations below. */ |
| overflow: hidden; |
| margin: 0px; |
| } |
| </style> |
| <script src="/resources/testharness.js"></script> |
| <script src="/resources/testharnessreport.js"></script> |
| <script src="resources/largest-contentful-paint-helpers.js"></script> |
| <script> |
| let beforeRender; |
| const viewportWidth = document.documentElement.clientWidth; |
| const viewportHeight = document.documentElement.clientHeight; |
| const imgWidth = 100; |
| const imgHeight = 50; |
| async_test(function (t) { |
| assert_implements(window.LargestContentfulPaint, "LargestContentfulPaint is not implemented"); |
| const beforeLoad = performance.now(); |
| new PerformanceObserver( |
| t.step_func_done(function(entryList) { |
| assert_equals(entryList.getEntries().length, 1); |
| const entry = entryList.getEntries()[0]; |
| const url = window.location.origin + '/images/green-100x50.png'; |
| // To compute the size, compute the percentage of the image visible and |
| // scale by its natural dimensions. In this test, the image is expanded to twice its size |
| // but place towards the bottom right corner of the viewport, so it is |
| // effectively clipped to 50% by 50% of its display size. Scaling by |
| // its natural width and height of 100px and 50px respectively, leads |
| // to a weighted size of 50 by 25. |
| const truncatedWidth = imgWidth / 2; |
| const truncatedHeight = imgHeight / 2; |
| const weightedSize = truncatedWidth * truncatedHeight; |
| checkImage(entry, url, 'image_id', weightedSize, beforeLoad); |
| }) |
| ).observe({type: 'largest-contentful-paint', buffered: true}); |
| // Add an image, setting width and height equal to viewport. |
| img = document.createElement('img'); |
| img.src = '/images/green-100x50.png'; |
| img.id = 'image_id'; |
| img.width = imgWidth * 2; |
| img.height = imgHeight * 2; |
| img.style.position = 'absolute'; |
| img.style.left = viewportWidth - imgWidth + 'px'; |
| img.style.top = viewportHeight - imgHeight + 'px'; |
| document.body.appendChild(img); |
| }, 'The intersectionRect of an img element overflowing is computed correctly'); |
| </script> |
| </body> |