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<!DOCTYPE html>
<link rel="help" href="https://drafts.csswg.org/css-scroll-snap-1/#valdef-scroll-snap-type-mandatory" />
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="./support/common.js"></script>
<style>
div {
position: absolute;
margin: 0px;
}
#scroller {
height: 500px;
width: 500px;
overflow: hidden;
}
.child {
width: 300px;
height: 300px;
background-color: blue;
}
</style>
<div id="scroller">
<div class="child" style="top: 0px; left: 0px;"></div>
<div class="child" style="top: 1000px; left: 1000px;"></div>
<div style="width: 2000px; height: 2000px;"></div>
</div>
<script>
test(() => {
scroller.style.scrollSnapType = "both mandatory";
// Scroll to where the first child is in view.
scroller.scrollTo(100, 100);
assert_equals(scroller.scrollLeft, 100);
assert_equals(scroller.scrollTop, 100);
// Scroll to where the second child is in view.
scroller.scrollTo(900, 900);
assert_equals(scroller.scrollLeft, 900);
assert_equals(scroller.scrollTop, 900);
}, "No snapping occurs if there is no valid snap position");
test(() => {
scroller.style.scrollSnapType = "x mandatory";
for (const target of document.querySelectorAll(".child")) {
target.scrollSnapAlign = "start none";
}
// Scroll to where the first child is in view.
scroller.scrollTo(100, 100);
assert_equals(scroller.scrollLeft, 100);
assert_equals(scroller.scrollTop, 100);
// Scroll to where the second child is in view.
scroller.scrollTo(900, 900);
assert_equals(scroller.scrollLeft, 900);
assert_equals(scroller.scrollTop, 900);
}, "No snapping occurs if there is no valid snap position matches scroll-snap-type");
promise_test(async t => {
// Start with valid snap positions.
scroller.style.scrollSnapType = "y mandatory";
document.querySelectorAll('.child').forEach(el => {
el.style.scrollSnapAlign = 'start';
t.add_cleanup(() => {
el.style.scrollSnapAlign = '';
});
});
scroller.scrollTo(100, 100);
await waitForNextFrame();
const scrollPosition = scroller.scrollTop;
// Elements no longer snap along the y-axis.
document.querySelectorAll('.child').forEach(el => {
el.style.scrollSnapAlign = 'none start';
// Bump the position to verify that we don't stay pinned to the same element
// after layout update.
el.style.top = `${parseInt(el.style.top) + 100}px`;
});
await waitForNextFrame();
assert_equals(scroller.scrollTop, scrollPosition);
scroller.scrollTo(900, 900);
assert_equals(scroller.scrollLeft, 900);
assert_equals(scroller.scrollTop, 900);
}, "No snapping occurs when last remaining valid snap point is no longer " +
"valid.");
</script>
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