49 lines
1.9 KiB
HTML
49 lines
1.9 KiB
HTML
<!DOCTYPE html>
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<html class="hide">
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<head>
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<title>Performance Paint Timing Test: Image FCP due to the documentElement's opacity</title>
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<style>
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html {
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will-change: opacity;
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}
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.hide {
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opacity: 0;
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}
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</style>
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</head>
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<body>
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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/utils.js"></script>
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<div id="main"></div>
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<script>
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// Load the image, add it to the DOM and make sure it's decoded.
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const load_image = () => {
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const img = document.createElement("img");
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img.src = "../resources/circles.png";
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document.body.appendChild(img);
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return img.decode();
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};
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const change_opacity = () => {
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document.documentElement.className = "";
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}
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promise_test(async t => {
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assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
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await load_image();
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await assertNoFirstContentfulPaint(t);
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change_opacity();
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await waitForAnimationFrames(3);
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const fcp_entries = performance.getEntriesByName('first-contentful-paint');
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assert_equals(fcp_entries.length, 1, "Got an FCP entry");
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const lcp_entries = await new Promise(resolve => {new PerformanceObserver((list) => resolve(list.getEntries())).observe({type: 'largest-contentful-paint', buffered: true})});
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assert_equals(lcp_entries.length, 1, "Got an LCP entry");
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// TODO: Rewrite this assertion after the FCP and LCP precision alignment CL is landed. Currently FCP start time has a higher precision than that of LCP. That means, even if the two are intrinsically the same, FCP.startTime will be larger as it has more fractional digits.
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isLess = fcp_entries[0].startTime < lcp_entries[0].startTime;
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isEqualToMicrosecond = Math.abs(fcp_entries[0].startTime - lcp_entries[0].startTime) < 0.001;
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assert_true(isLess || isEqualToMicrosecond, "FCP should be smaller than FCP.");
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}, "Test that FCP after opacity change is not a larger value than LCP");
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</script>
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</body>
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</html>
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