position-sticky-nested-bottom.html

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This WPT test may be referenced by the following Test IDs:
- /css/css-position/sticky/position-sticky-nested-bottom.html - WPT Dashboard Interop Dashboard

<!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>