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<!DOCTYPE html>
<link rel="help" href="https://drafts.csswg.org/css-scroll-snap/#scroll-snap-stop" />
<meta name="viewport" content="width=device-width,initial-scale=1,minimum-scale=1">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
div, html, body {
margin: 0;
padding: 0;
}
html {
scroll-snap-type: x mandatory;
overflow: scroll;
}
#scroller {
scroll-snap-type: x mandatory;
overflow: scroll;
height: 400px;
width: 400px;
}
.large_space {
width: 2000px;
height: 2000px;
}
.snap_area {
scroll-snap-align: none start;
width: 100px;
height: 100px;
background-color: blue;
}
.snap_area:nth-child(1) {
margin-left: 0;
}
.snap_area:nth-child(2) {
margin-left: 100px;
}
.snap_area:nth-child(3) {
margin-left: 300px;
}
.snap_area:nth-child(4) {
margin-left: 500px;
}
</style>
<!-- Add snap area to the root scroller -->
<div class="snap_area"></div>
<div class="snap_area"></div>
<div class="snap_area"></div>
<div class="snap_area"></div>
<div id="scroller">
<div class="snap_area"></div>
<div class="snap_area"></div>
<div class="snap_area"></div>
<div class="snap_area"></div>
<div class="large_space"></div>
</div>
<div class="large_space"></div>
<script>
const scrollers = [document.scrollingElement, document.getElementById("scroller")];
for (const scroller of scrollers) {
test(_ => {
assert_equals(scroller.scrollLeft, 0); // sanity check
scroller.querySelectorAll('.snap_area').forEach(area => area.style.scrollSnapStop = 'always');
scroller.scrollBy(500, 0);
assert_equals(scroller.scrollLeft, 100, "scrollBy should not skip area with stop always");
scroller.querySelectorAll('.snap_area').forEach(area => area.style.scrollSnapStop = 'normal');
scroller.scrollBy(500, 0);
assert_equals(scroller.scrollLeft, 500, "scrollBy should skip secon area with stop normal");
// When snap type is changed back to mandatory, scrolling should snap.
scroller.querySelectorAll('.snap_area').forEach(area => area.style.scrollSnapStop = 'always');
scroller.scrollBy(-500, 0);
assert_equals(scroller.scrollLeft, 300, "scrollBy should not skip area with stop always");
}, `scroll-snap-stop for areas on ${scroller.nodeName} should control snapping behavior and changing it takes effect`);
}
</script>
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