observe-multiple-images.html (5004B)
1 <!DOCTYPE HTML> 2 <meta charset=utf-8> 3 <title>Element Timing: multiple images</title> 4 <body> 5 <style> 6 body { 7 margin: 0; 8 } 9 #img1 { 10 display: block; 11 margin-left: auto; 12 margin-right: auto; 13 } 14 #img2 { 15 margin-top:150px; 16 margin-left:50px; 17 } 18 </style> 19 <script src="/resources/testharness.js"></script> 20 <script src="/resources/testharnessreport.js"></script> 21 <script src="resources/element-timing-helpers.js"></script> 22 <script> 23 let beforeRender, image1Observed=0, image2Observed=0, image3Observed=0; 24 async_test(function (t) { 25 assert_implements(window.PerformanceElementTiming, "PerformanceElementTiming is not implemented"); 26 const observer = new PerformanceObserver( 27 t.step_func(function(entryList) { 28 entryList.getEntries().forEach( entry => { 29 if (entry.identifier === 'image1') { 30 if (image1Observed) { 31 assert_unreached("Observer received image1 more than once"); 32 t.done(); 33 } 34 image1Observed = 1; 35 const pathname1 = window.location.origin + '/element-timing/resources/square100.png'; 36 // The images do not contain ID, so expect an empty ID. 37 checkElement(entry, pathname1, 'image1', 'img1', beforeRender, 38 document.getElementById('img1')); 39 // This image is horizontally centered. 40 // Using abs and comparing to 1 because the viewport sizes could be odd. 41 // If a size is odd, then image cannot be in the pure center, but left 42 // and right should still be very close to their estimated coordinates. 43 assert_less_than_equal(Math.abs(entry.intersectionRect.left - 44 (document.documentElement.clientWidth / 2 - 50)), 1, 45 'left of rect for image1'); 46 assert_less_than_equal(Math.abs(entry.intersectionRect.right - 47 (document.documentElement.clientWidth / 2 + 50)), 1, 48 'right of rect for image1'); 49 assert_equals(entry.intersectionRect.top, 0, 'top of rect for image1'); 50 assert_equals(entry.intersectionRect.bottom, 51 100, 'bottom of rect for image1'); 52 checkNaturalSize(entry, 100, 100); 53 } 54 else if (entry.identifier === 'image2') { 55 if (image2Observed) { 56 assert_unreached("Observer received image2 more than once"); 57 t.done(); 58 } 59 image2Observed = 1; 60 const pathname2 = window.location.origin + '/element-timing/resources/square20.png'; 61 checkElement(entry, pathname2, 'image2', 'img2', beforeRender, 62 document.getElementById('img2')); 63 // This image should be below image 1, and should respect the margin. 64 checkRect(entry, [50, 250, 250, 450], "of image2"); 65 checkNaturalSize(entry, 20, 20); 66 } 67 else if (entry.identifier === 'image3') { 68 if (image3Observed) { 69 assert_unreached("Observer received image3 more than once"); 70 t.done(); 71 } 72 image3Observed = 1; 73 const pathname3 = window.location.origin + '/element-timing/resources/circle.svg'; 74 checkElement(entry, pathname3, 'image3', 'img3', beforeRender, 75 document.getElementById('img3')); 76 // This image is just to the right of image2. 77 checkRect(entry, [250, 450, 250, 450], "of image3"); 78 checkNaturalSize(entry, 200, 200); 79 } 80 else { 81 assert_unreached("Received an unexpected identifier."); 82 t.done(); 83 } 84 if (image1Observed && image2Observed && image3Observed) { 85 t.done(); 86 } 87 }); 88 }) 89 ); 90 observer.observe({entryTypes: ['element']}); 91 function addImage(number, source, width=0) { 92 const img = document.createElement('img'); 93 img.src = source; 94 // Set a different id and elementtiming value for each image. 95 img.id = 'img' + number; 96 img.setAttribute('elementtiming', 'image' + number); 97 if (width !== 0) 98 img.width = width; 99 document.body.appendChild(img); 100 } 101 // Add the images during onload to be sure that the observer is registered in 102 // time to observe the element timing. 103 window.onload = () => { 104 addImage(1, 'resources/square100.png'); 105 // Use requestAnimationFrame and a timeout to ensure that the images are 106 // processed in the order we want. 107 requestAnimationFrame( () => { 108 t.step_timeout( () => { 109 // Set the size equal to that of image3 to make positioning easier. 110 addImage(2, 'resources/square20.png', 200); 111 requestAnimationFrame( () => { 112 t.step_timeout( () => { 113 addImage(3, 'resources/circle.svg'); 114 }, 0); 115 }); 116 }, 0); 117 }); 118 beforeRender = performance.now(); 119 }; 120 }, 'PerformanceObserver can observe multiple image elements.'); 121 </script> 122 </body>