<!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>
async function assertScrollPositionResetOnDisplayNone(scroller) {
return new Promise((resolve) => {
if (getComputedStyle(scroller)["display"] == "none") {
assert_equals(scroller.scrollTop, 0, "scrollTop is reset");
assert_equals(scroller.scrollLeft, 0, "scrollLeft is reset");
resolve();
} else {
requestAnimationFrame(async () => {
await assertScrollPositionResetOnDisplayNone(scroller);
resove();
});
}
});
}
promise_test(async (t) => {
// This tests that toggling the display of a scroller from none to block
// scroll-start does not reset the scroller's scroll position.
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;
assert_equals(scroller.scrollTop, 200,
"vertical scroll position is programmatically adjusted");
assert_equals(scroller.scrollLeft, 100,
"horizontal scroll position is programmatically adjusted");
scroller.style.display = "none";
assert_equals(getComputedStyle(scroller)["display"], "none");
await assertScrollPositionResetOnDisplayNone(scroller);
scroller.style.display = "block";
assert_equals(getComputedStyle(scroller)["display"], "block");
// Verify that we are again scrolled to the position specified by scroll-start.
assert_equals(scroller.scrollTop, 200,
"scroll-start is not applied vertically after display toggle");
assert_equals(scroller.scrollLeft, 100,
"scroll-start is not applied horizontally after display toggle");
}, "scroll-start does not interfer with recovering saved scroll position " +
"after display toggle");
</script>
</body>
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