56 lines
2.4 KiB
HTML
56 lines
2.4 KiB
HTML
<!DOCTYPE HTML>
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<meta charset=utf-8>
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<meta name="viewport" content="width=device-width, minimum-scale=1">
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<title>Largest Contentful Paint: size when image overflows</title>
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<body>
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<style>
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body {
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/* Preventing a scrollbar from showing and removing any margins simplifies
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the calculations below. */
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overflow: hidden;
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margin: 0px;
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}
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</style>
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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>
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setup({"hide_test_state": true});
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let beforeRender;
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const viewportWidth = document.documentElement.clientWidth;
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const viewportHeight = document.documentElement.clientHeight;
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const imgWidth = 100;
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const imgHeight = 50;
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async_test(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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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 url = window.location.origin + '/images/lcp-100x50.png';
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// To compute the size, compute the percentage of the image visible and
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// scale by its natural dimensions. In this test, the image is expanded to twice its size
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// but place towards the bottom right corner of the viewport, so it is
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// effectively clipped to 50% by 50% of its display size. Scaling by
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// its natural width and height of 100px and 50px respectively, leads
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// to a weighted size of 50 by 25.
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const truncatedWidth = imgWidth / 2;
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const truncatedHeight = imgHeight / 2;
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const weightedSize = truncatedWidth * truncatedHeight;
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checkImage(entry, url, 'image_id', weightedSize, beforeLoad);
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})
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).observe({type: 'largest-contentful-paint', buffered: true});
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// Add an image, setting width and height equal to viewport.
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img = document.createElement('img');
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img.src = '/images/lcp-100x50.png';
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img.id = 'image_id';
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img.width = imgWidth * 2;
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img.height = imgHeight * 2;
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img.style.position = 'absolute';
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img.style.left = viewportWidth - imgWidth + 'px';
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img.style.top = viewportHeight - imgHeight + 'px';
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document.body.appendChild(img);
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}, 'The intersectionRect of an img element overflowing is computed correctly');
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</script>
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</body>
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