<!DOCTYPE html>
<title>
  Not re-snap once after a scroll operation has finished without snapping
  because the scroll destination was outside of the snap proximity threshold.
</title>
<!-- This test assumes that all major browsers' default scroll-snap proximity
     thresholds are greater than 200px. -->
<link rel="help" href="https://drafts.csswg.org/css-scroll-snap/#re-snap" />
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1780154">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
div {
  position: absolute;
  margin: 0;
}

#scroller {
  height: 600px;
  width: 600px;
  overflow: hidden;
  scroll-snap-type: y proximity;
}

.snap {
  width: 300px;
  height: 300px;
  background-color: green;
  scroll-snap-align: start;
}

.area {
  width: 2000px;
  height: 2000px;
}
</style>

<div id="scroller">
  <div class="area"></div>
  <div class="snap" style="top: 0px;"></div>
  <div class="snap" style="top: 500px;"></div>
</div>

<script>
test(() => {
  // The initial snap position is at (0, 0).
  assert_equals(scroller.scrollTop, 0);
  assert_equals(scroller.scrollLeft, 0);

  // Scroll to a position where it's outside of the scroll-snap proximity
  // threshold, so that it won't trigger snapping.
  scroller.scrollTo(0, 250);

  assert_equals(scroller.scrollTop, 250);
  assert_equals(scroller.scrollLeft, 0);

  // Changing the initial snap target position, but still it's outside of the
  // threshold.
  document.querySelectorAll(".snap")[0].style.top = "10px";

  // Not re-snap to the last snap point.
  assert_equals(scroller.scrollTop, 250);
  assert_equals(scroller.scrollLeft, 0);
}, "Not re-snap once after a scroll operation has finished without snapping " +
   "because the scroll destination was outside of the snap proximity threshold.");
</script>
