testing/web-platform/tests/css/css-scroll-snap/no-snap-position.html
author Hiroyuki Ikezoe <hikezoe@mozilla.com>
Fri, 17 May 2019 20:50:24 +0000
changeset 533278 ef3c6d8bb498bfdae4c53cc9eec12f70bb9284ed
permissions -rw-r--r--
Bug 1551806 - Don't try to snap if there is no valid snap positions for the scroll-snap v1 implementation. r=botond From the spec [1]; If a valid snap position exists then the scroll container must snap at the termination of a scroll (if none exist then no snapping occurs). Both of test cases in this commit fail without this change. [1] https://drafts.csswg.org/css-scroll-snap-1/#valdef-scroll-snap-type-mandatory Differential Revision: https://phabricator.services.mozilla.com/D31409

<!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>
<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.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.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");
</script>