<!DOCTYPE HTML> <meta charset=utf-8> <title>Element Timing: observe element with buffered flag</title> <body> <style> body { margin: 0; } </style> <script src="/resources/testharness.js"></script> <script src="/resources/testharnessreport.js"></script> <script src="resources/element-timing-helpers.js"></script> <script> async_test(t => { assert_implements(window.PerformanceElementTiming, "PerformanceElementTiming is not implemented"); const beforeRender = performance.now(); const img = document.createElement('img'); // Initial observer used to know when entry has been dispatched new PerformanceObserver(() => { // Second observer should require buffered flag to receive the already-dispatched entry. new PerformanceObserver(t.step_func_done(entryList => { assert_equals(entryList.getEntries().length, 1); const entry = entryList.getEntries()[0]; const pathname = window.location.origin + '/images/black-rectangle.png'; checkElement(entry, pathname, 'my_image', 'my_id', beforeRender, document.getElementById('my_id')); // Test that viewport size is at least 100, so element is fully visible. assert_greater_than_equal(document.documentElement.clientWidth, 100, 'Width should be >= 100'); assert_greater_than_equal(document.documentElement.clientHeight, 100, 'Height should be >= 100'); checkRect(entry, [0, 100, 0, 50]); checkNaturalSize(entry, 100, 50); })).observe({type: 'element', buffered: true}); }).observe({type: 'element'}); img.src = '/images/black-rectangle.png'; img.setAttribute('elementtiming', 'my_image'); img.setAttribute('id', 'my_id'); document.body.appendChild(img); }, 'Element Timing entries are observable via buffered flag.'); </script> </body>