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Test Info:

<!DOCTYPE html>
<title>position:sticky elements should respect the left constraint</title>
<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>