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<!DOCTYPE html>
<title>Nested bottom-constrained 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 bottom 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('bottom', 25, 35);
elements.scroller.scrollTop = 300;
const nonStickyTopY = elements.container.offsetTop +
elements.filler.clientHeight;
assert_equals(elements.sticky.offsetTop, nonStickyTopY);
// The inner sticky should not be offset from the outer.
const nonStickyInnerTopY = elements.sticky.clientHeight -
elements.innerSticky.clientHeight;
assert_equals(elements.innerSticky.offsetTop, nonStickyInnerTopY);
}, 'before reaching the sticking point, neither sticky box should be offset');
test(() => {
const elements = setupNestedStickyTest('bottom', 25, 50);
elements.scroller.scrollTop = 150;
const nonStickyTopY = elements.container.offsetTop +
elements.filler.clientHeight;
assert_equals(elements.sticky.offsetTop, nonStickyTopY);
assert_equals(elements.innerSticky.offsetTop, 50);
}, 'the inner sticky can stick before the outer one if necessary');
test(() => {
const elements = setupNestedStickyTest('bottom', 25, 35);
elements.scroller.scrollTop = 100;
const nonStickyTopY = elements.container.offsetTop +
elements.filler.clientHeight;
const nonStickyBottomY = nonStickyTopY + elements.sticky.clientHeight;
const targetBottomY = elements.scroller.clientHeight +
elements.scroller.scrollTop - 25;
const stickyOffset = nonStickyBottomY - targetBottomY;
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 (height - the difference between the
// top values).
assert_equals(elements.innerSticky.offsetTop, 40);
}, 'both sticky boxes can be stuck at the same time');
test(() => {
const elements = setupNestedStickyTest('bottom', 25, 75);
elements.scroller.scrollTop = 0;
assert_equals(elements.sticky.offsetTop, elements.container.offsetTop);
assert_equals(elements.innerSticky.offsetTop, 0);
}, 'neither sticky can escape their containing block');
test(() => {
const elements = setupNestedStickyTest('bottom', 25, 300);
elements.scroller.scrollTop = 200;
// It doesn't matter how big the inner sticky offset is, it cannot escape its
// containing block (the outer sticky).
assert_equals(elements.innerSticky.offsetTop, 0);
}, 'the inner sticky cannot be pushed outside the outer sticky');
</script>
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