<!DOCTYPE html>
<title>
Snap to an area where the element's scroll-margin is visible but not the
element itself (using both axes snap type)
</title>
<link rel="help" href="https://drafts.csswg.org/css-scroll-snap-1/#snap-scope"/>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
div {
position: absolute;
margin: 0px;
}
#scroller {
height: 600px;
width: 600px;
overflow: scroll;
scroll-snap-type: both mandatory;
}
#space {
width: 2000px;
height: 2000px;
}
.snap {
width: 200px;
height: 200px;
background-color: blue;
scroll-snap-align: start;
}
#left-top {
left: 0px;
top: 0px;
}
#left-bottom {
left: 0px;
top: 800px;
/* 800px scroll-margin makes the snap area span to the right end of the
right-top area */
scroll-margin-right: 800px;
}
#right-top {
left: 800px;
top: 0px;
/* 800px scroll-margin makes the snap area span to the bottom end of the
left-bottom area */
scroll-margin-bottom: 800px;
}
</style>
<div id="scroller">
<div id="space"></div>
<div id="left-top" class="snap"></div>
<div id="left-bottom" class="snap"></div>
<div id="right-top" class="snap"></div>
</div>
<script>
test(() => {
const scroller = document.getElementById("scroller");
scroller.scrollTo(0, 0);
assert_equals(scroller.scrollLeft, 0);
assert_equals(scroller.scrollTop, 0);
// 750 and 650 are picked as those are closer to top left of the intersection
// (800, 800) of the snap areas where the browser should snap. This makes the
// intersection a closer snap option than a covering option that the browser
// might choose where the snapport is aligned on the bottom and right.
scroller.scrollTo(650, 750);
assert_equals(scroller.scrollLeft, 800);
assert_equals(scroller.scrollTop, 800);
scroller.scrollTo(750, 650);
assert_equals(scroller.scrollLeft, 800);
assert_equals(scroller.scrollTop, 800);
}, 'Snap to area such that only the scroll margin from both axes\' areas are \
visible');
</script>
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