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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title> CSS Scroll Snap 2 Test: scroll-start-*</title>
<link rel="help" href="https://drafts.csswg.org/css-scroll-snap-2/#scroll-start">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
</head>
<body>
<style>
#scroller {
height: 100px;
width: 100px;
scroll-start: 100px 200px;
border: solid 1px black;
overflow: scroll;
}
.spacer {
width: 200vw;
height: 200vh;
border: solid 1px green;
}
</style>
<div id="scroller">
<div class="spacer"></div>
</div>
<script>
promise_test(async (t) => {
// This tests that toggling the overflow of a scroller from visible to
// scroll doesn't change the scroll position to scroll-start (since
// overflow:visible to overflow:scroll doesn't cause the scroller to be laid
// out again.)
assert_equals(scroller.scrollTop, 100,
"scroll-start: <length> sets initial vertical scroll position");
assert_equals(scroller.scrollLeft, 200,
"scroll-start: <length> sets initial horizontal scroll position");
// Scroll to somewhere other than scroll-start position.
scroller.scrollTop = 200;
scroller.scrollLeft = 100;
// Allow for an animation frame that might be needed for the update to take
// place.
await requestAnimationFrame(() => { });
assert_equals(scroller.scrollTop, 200,
"vertical scroll position is programmatically adjusted");
assert_equals(scroller.scrollLeft, 100,
"horizontal scroll position is programmatically adjusted");
scroller.style.overflow = "visible";
assert_equals(getComputedStyle(scroller)["overflow"], "visible");
scroller.style.overflow = "scroll";
assert_equals(getComputedStyle(scroller)["overflow"], "scroll");
// Verify that the scroll position is not changed.
assert_equals(scroller.scrollTop, 200,
"scroll-start does not reset vertical scroll position on overflow " +
"toggle.");
assert_equals(scroller.scrollLeft, 100,
"scroll-start does not reset vertical scroll position on overflow " +
"toggle.");
}, "scroll-start sets scroller position if overflow is not visible");
</script>
</body>
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