snap-to-visible-areas.html
<!DOCTYPE html>
<link rel="help" href="https://drafts.csswg.org/css-scroll-snap-1" />
<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;
}
#right-top {
left: 800px;
top: 0px;
}
#left-bottom {
left: 0px;
top: 800px;
}
</style>
<div id="scroller">
<div id="space"></div>
<div id="left-top" class="snap"></div>
<div id="right-top" class="snap"></div>
<div id="left-bottom" class="snap"></div>
</div>
<script>
var scroller = document.getElementById("scroller");
test(() => {
scroller.scrollTo(0, 0);
assert_equals(scroller.scrollLeft, 0);
assert_equals(scroller.scrollTop, 0);
scroller.scrollTo(300, 0);
assert_equals(scroller.scrollLeft, 800);
assert_equals(scroller.scrollTop, 0);
}, 'Only snap to visible area on X axis, even when the non-visible ones are closer');
test(() => {
scroller.scrollTo(0, 0);
assert_equals(scroller.scrollLeft, 0);
assert_equals(scroller.scrollTop, 0);
scroller.scrollTo(0, 300);
assert_equals(scroller.scrollLeft, 0);
assert_equals(scroller.scrollTop, 800);
}, 'Only snap to visible area on Y axis, even when the non-visible ones are closer');
</script>