49 lines
1.6 KiB
HTML
49 lines
1.6 KiB
HTML
<!DOCTYPE html>
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<title>Layout Instability: layout shift when content expanded above the viewport</title>
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<link rel="help" href="https://wicg.github.io/layout-instability/" />
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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/test-adapter.js"></script>
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<script src="resources/util.js"></script>
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<style>
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body {
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margin: 0;
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/* To avoid browser automatic scroll offset adjustment for the expansion. */
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overflow-anchor: none;
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}
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</style>
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<div id="expander" style="height: 50vh"></div>
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<div id="shifted" style="width: 300px; height: 300vh; background: blue"></div>
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<script>
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promise_test(async () => {
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const watcher = new ScoreWatcher;
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// Wait for the initial render to complete.
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await waitForAnimationFrames(2);
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const viewHeight = document.documentElement.clientHeight;
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window.scrollTo(0, viewHeight);
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await waitForAnimationFrames(2);
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// Expander expands to push |shifted| down.
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expander.style.height = '150vh';
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const expectedScore1 = computeExpectedScore(300 * viewHeight, viewHeight);
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// Observer fires after the frame is painted.
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cls_expect(watcher, {score: 0});
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await watcher.promise;
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cls_expect(watcher, {score: expectedScore1});
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// Expander expands to push |shifted| out of viewport.
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expander.style.height = '200vh';
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const expectedScore2 = expectedScore1 +
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computeExpectedScore(0.5 * 300 * viewHeight, 0.5 * viewHeight);
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await watcher.promise;
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cls_expect(watcher, {score: expectedScore2});
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}, "Layout shift when content expanded above the viewport");
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</script>
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