<!DOCTYPE html>
<title>`intended direction` scroll snaps only at points ahead of the scroll direction</title>
<link rel="help" href="https://drafts.csswg.org/css-scroll-snap-1/#scroll-snap-type" />
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1766805">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
div {
  position: absolute;
  margin: 0px;
}
#scroller {
  width: 200px;
  height: 100px;
  overflow: scroll;
  scroll-snap-type: x mandatory;
}
.snap {
  scroll-snap-align: start;
  background: green;
}
</style>

<div id="scroller">
  <div style="width: 2000px; height: 100px;"></div>
  <div class="snap" style="left:   0px; width: 20px; height: 100px;">1</div>
  <div class="snap" style="left: 100px; width: 20px; height: 100px;">2</div>
  <div class="snap" style="left: 120px; width: 20px; height: 100px;">3</div>
  <div class="snap" style="left: 300px; width: 20px; height: 100px;">4</div>
  <div class="snap" style="left: 400px; width: 20px; height: 100px;">5</div>
</div>

<script>
test(() => {
  scroller.scrollBy(10, 0);
  assert_equals(scroller.scrollLeft, 100);

  scroller.scrollBy(10, 0);
  assert_equals(scroller.scrollLeft, 120);

  scroller.scrollBy(10, 0);
  // Snaps to the next snap point even if the previous snap point is closer to
  // the current position.
  assert_equals(scroller.scrollLeft, 300);
}, "`intended direction` scroll snaps only at points ahead of the scroll " +
   "direction");

</script>
