<!DOCTYPE html>
<title>position:sticky elements should respect the left constraint</title>
<link rel="help" href="https://www.w3.org/TR/css-position-3/#sticky-pos" />
<meta name="assert" content="This test checks that position:sticky elements obey their left anchor after scrolling" />

<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 = setupStickyTest('left', 50);
  elements.scroller.scrollLeft = 100;
  const nonStickyLeftX = elements.container.offsetLeft +
      elements.filler.clientWidth;
  assert_equals(elements.sticky.offsetLeft, nonStickyLeftX);
}, 'before reaching the sticking point the sticky box should not be offset');

test(() => {
  const elements = setupStickyTest('left', 50);
  elements.scroller.scrollLeft = 200;

  // This math actually cancels to sticky.offsetLeft == (scroller.scrollLeft + 50),
  // but for clarity the calculations are left explicit.
  const nonStickyLeftX = elements.container.offsetLeft +
      elements.filler.clientWidth;
  const targetLeftX = elements.scroller.scrollLeft + 50;
  const stickyOffset = targetLeftX - nonStickyLeftX;

  assert_equals(elements.sticky.offsetLeft, nonStickyLeftX + stickyOffset);
}, 'after reaching the sticking point the sticky box should be offset');

test(() => {
  const elements = setupStickyTest('left', 50);
  elements.scroller.scrollLeft = 300;
  const maxOffsetInContainer = elements.container.offsetLeft +
      elements.container.clientWidth - elements.sticky.clientWidth;
  assert_equals(elements.sticky.offsetLeft, maxOffsetInContainer);
}, 'the sticky box should not be pushed outside its containing block');
</script>
