41 lines
1.7 KiB
HTML
41 lines
1.7 KiB
HTML
<!DOCTYPE HTML>
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<meta charset=utf-8>
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<title>Layout Instability: PerformanceObserver sees entries with buffered flag</title>
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<body>
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<style>
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#myDiv { position: relative; width: 300px; height: 100px; background: blue; }
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</style>
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<div id='myDiv'></div>
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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/util.js"></script>
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<script>
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promise_test(async t => {
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assert_implements(window.LayoutShift, 'Layout Instability is not supported.');
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// Wait for the initial render to complete.
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await waitForAnimationFrames(2);
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const startTime = performance.now();
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return new Promise(resolve => {
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// First observer creates second in callback to ensure the entry has been dispatched by the time
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// the second observer begins observing.
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new PerformanceObserver(() => {
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const endTime = performance.now();
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// Second observer requires 'buffered: true' to see entries.
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new PerformanceObserver(t.step_func(list => {
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assert_equals(list.getEntries().length, 1);
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const entry = list.getEntries()[0];
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assert_equals(entry.entryType, "layout-shift");
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assert_greater_than_equal(entry.startTime, startTime);
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assert_less_than_equal(entry.startTime, endTime);
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assert_equals(entry.duration, 0.0);
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assert_equals(entry.value, computeExpectedScore(300 * (100 + 60), 60));
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resolve();
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})).observe({'type': 'layout-shift', buffered: true});
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}).observe({type: 'layout-shift'});
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// Modify the position of the div to cause a layout-shift entry.
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document.getElementById('myDiv').style = "top: 60px";
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});
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}, 'PerformanceObserver with buffered flag sees previous layout-shift entry.');
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</script>
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</body>
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