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<!DOCTYPE html>
<title>Nested top-constrainted position:sticky elements should render correctly</title>
<link rel="help" href="https://www.w3.org/TR/css-position-3/#sticky-pos" />
<meta name="assert" content="This test checks that nested position:sticky elements with a top constraint render correctly" />
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="resources/sticky-util.js"></script>
<body></body>
<script>
test(() => {
const elements = setupNestedStickyTest('top', 50, 60);
elements.scroller.scrollTop = 100;
const nonStickyTopY = elements.container.offsetTop +
elements.filler.clientHeight;
assert_equals(elements.sticky.offsetTop, nonStickyTopY);
// The inner sticky should not be offset from the outer.
assert_equals(elements.innerSticky.offsetTop, 0);
}, 'before reaching the sticking point, neither sticky box should be offset');
test(() => {
const elements = setupNestedStickyTest('top', 50, 60);
elements.scroller.scrollTop = 145;
const nonStickyTopY = elements.container.offsetTop +
elements.filler.clientHeight;
assert_equals(elements.sticky.offsetTop, nonStickyTopY);
assert_equals(elements.innerSticky.offsetTop, 5);
}, 'the inner sticky can stick before the outer one if necessary');
test(() => {
const elements = setupNestedStickyTest('top', 50, 60);
elements.scroller.scrollTop = 200;
// This math cancels to sticky.offsetTop == (scroller.scrollTop + 50), but
// for clarity the calculations are left explicit.
const nonStickyTopY = elements.container.offsetTop +
elements.filler.clientHeight;
const targetTopY = elements.scroller.scrollTop + 50;
const stickyOffset = targetTopY - nonStickyTopY;
assert_equals(elements.sticky.offsetTop, nonStickyTopY + stickyOffset);
// The inner sticky has similar math, but its offsetTop is relative to the
// sticky element and in this test is the difference between the top values.
assert_equals(elements.innerSticky.offsetTop, 10);
}, 'both sticky boxes can be stuck at the same time');
test(() => {
const elements = setupNestedStickyTest('top', 50, 60);
elements.scroller.scrollTop = 300;
const maxOffsetInContainer = elements.container.offsetTop +
elements.container.clientHeight - elements.sticky.clientHeight;
assert_equals(elements.sticky.offsetTop, maxOffsetInContainer);
const maxOffsetInOuterSticky = elements.sticky.clientHeight -
elements.innerSticky.clientHeight;
assert_equals(elements.innerSticky.offsetTop, maxOffsetInOuterSticky);
}, 'neither sticky can escape their containing block');
test(() => {
const elements = setupNestedStickyTest('top', 50, 300);
elements.scroller.scrollTop = 100;
// The outer sticky has not stuck yet.
const nonStickyTopY = elements.container.offsetTop +
elements.filler.clientHeight;
assert_equals(elements.sticky.offsetTop, nonStickyTopY);
// But the inner sticky still cannot escape the outer sticky (as it is the
// containing block).
const maxOffsetInOuterSticky = elements.sticky.clientHeight -
elements.innerSticky.clientHeight;
assert_equals(elements.innerSticky.offsetTop, maxOffsetInOuterSticky);
}, 'the inner sticky cannot be pushed outside the outer sticky');
</script>
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