snap-to-different-targets.html | Explore in Territory

<!DOCTYPE html>
<title>
  The scroller should try to resnap to targets for both axes if possible.
</title>
<link rel="help" href="https://drafts.csswg.org/css-scroll-snap/#re-snap" />
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
div {
  position: absolute;
  margin: 0;
}

#scroller {
  height: 500px;
  width: 500px;
  overflow: hidden;
  scroll-snap-type: both mandatory;
}

#x-axis-target {
  scroll-snap-align: none start;
  background-color: blue;
  width: 100px;
  height: 100px;
  top: 400px;
  left: 200px;
}

#y-axis-target {
  scroll-snap-align: start none;
  background-color: green;
  width: 100px;
  height: 100px;
  top: 200px;
  left: 400px;
}

#far-x-axis-target {
  scroll-snap-align: none start;
  background-color: blue;
  width: 100px;
  height: 100px;
  top: 1200px;
  left: 300px;
}

#far-y-axis-target {
  scroll-snap-align: start none;
  background-color: green;
  width: 100px;
  height: 100px;
  top: 300px;
  left: 1200px;
}

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

<div id="scroller">
  <div class="area"></div>
  <div id="x-axis-target"></div>
  <div id="y-axis-target"></div>
  <div id="far-x-axis-target"></div>
  <div id="far-y-axis-target"></div>
</div>

<script>

const x_target = document.getElementById("x-axis-target");
const y_target = document.getElementById("y-axis-target");
const scroller = document.getElementById("scroller");

test(t => {
  // The scroller should be snapped to the two closest points on first layout.
  assert_equals(scroller.scrollTop, 200);
  assert_equals(scroller.scrollLeft, 200);
  x_target.style.setProperty("left", "1000px");
  y_target.style.setProperty("top", "1000px");

  // The style change makes it impossible for the scroller to snap to both
  // targets, but at least one of the targets should be preserved. The scroller
  // should then re-evaluate the snap point for the other axis.
  const snapped_to_x = scroller.scrollLeft == 1000 && scroller.scrollTop == 300;
  const snapped_to_y = scroller.scrollTop == 1000 && scroller.scrollLeft == 300;
  assert_true(snapped_to_x || snapped_to_y);
}, "Scroller should snap to at least one of the targets if unable to snap to both after a layout change.");
</script>
chromium/third_party/blink/web_tests/external/wpt/css/css-scroll-snap/snap-after-relayout/snap-to-different-targets.html
