43 lines
1.7 KiB
HTML
43 lines
1.7 KiB
HTML
<!DOCTYPE html>
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<title>position:sticky elements should respect the top constraint</title>
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<link rel="help" href="https://www.w3.org/TR/css-position-3/#sticky-pos" />
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<meta name="assert" content="This test checks that position:sticky elements obey their top anchor after scrolling" />
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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/sticky-util.js"></script>
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<body></body>
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<script>
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test(() => {
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const elements = setupStickyTest('top', 50);
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elements.scroller.scrollTop = 100;
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const nonStickyTopY = elements.container.offsetTop +
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elements.filler.clientHeight;
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assert_equals(elements.sticky.offsetTop, nonStickyTopY);
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}, 'before reaching the sticking point the sticky box should not be offset');
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test(() => {
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const elements = setupStickyTest('top', 50);
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elements.scroller.scrollTop = 200;
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// This math cancels to sticky.offsetTop == (scroller.scrollTop + 50), but
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// for clarity the calculations are left explicit.
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const nonStickyTopY = elements.container.offsetTop +
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elements.filler.clientHeight;
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const targetTopY = elements.scroller.scrollTop + 50;
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const stickyOffset = targetTopY - nonStickyTopY;
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assert_equals(elements.sticky.offsetTop, nonStickyTopY + stickyOffset);
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}, 'after reaching the sticking point the sticky box should be offset');
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test(() => {
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const elements = setupStickyTest('top', 50);
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elements.scroller.scrollTop = 300;
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const maxOffsetInContainer = elements.container.offsetTop +
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elements.container.clientHeight - elements.sticky.clientHeight;
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assert_equals(elements.sticky.offsetTop, maxOffsetInContainer);
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}, 'the sticky box should not be pushed outside its containing block');
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</script>
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