57 lines
2.2 KiB
HTML
57 lines
2.2 KiB
HTML
<!DOCTYPE HTML>
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<meta charset=utf-8>
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<title>Element Timing: observe element with background image in its first letter</title>
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<body>
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<style>
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#target::first-letter {
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background-image: url('/images/black-rectangle.png');
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}
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#target {
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font-size: 12px;
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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/element-timing-helpers.js"></script>
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<script>
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let beforeRender = performance.now();
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async_test(function (t) {
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assert_implements(window.PerformanceElementTiming, "PerformanceElementTiming is not implemented");
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const div = document.getElementById('target');
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let textObserved = false;
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let imageObserved = false;
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function calculateSize(entry) {
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const ir = entry.intersectionRect;
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return (ir.right - ir.left) * (ir.bottom - ir.top);
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}
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const observer = new PerformanceObserver(
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t.step_func(function(entryList) {
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entryList.getEntries().forEach(entry => {
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if (entry.name === 'text-paint') {
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checkTextElement(entry, 'my_div', 'target', beforeRender, div);
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textObserved = true;
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const size = calculateSize(entry);
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// Assume average width is between 4px and 15px.
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// Therefore, text size must be between 12 * (35*4) and 12 * (35*15).
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assert_between_inclusive(size, 1680, 6300);
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}
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else {
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assert_equals(entry.name, 'image-paint');
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const pathname = window.location.origin + '/images/black-rectangle.png';
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checkElement(entry, pathname, 'my_div', 'target', beforeRender, div);
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checkNaturalSize(entry, 100, 50);
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imageObserved = true;
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const size = calculateSize(entry);
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// Background image size should only be approximately the size of a single letter.
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assert_between_inclusive(size, 48, 180);
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}
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});
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if (textObserved && imageObserved)
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t.done();
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})
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);
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observer.observe({entryTypes: ['element']});
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}, 'Element with elementtiming attribute and background image in first-letter is observable.');
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</script>
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<div id='target' elementtiming='my_div'>This is some text that I care about</div>
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</body>
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