<!DOCTYPE html>
<title>Layout Instability: shift in pointerdown becoming scroll</title>
<link rel="help" href="https://wicg.github.io/layout-instability/" />
<style>
body { margin: 0; height: 2000px; }
#box {
left: 0px;
top: 0px;
width: 400px;
height: 500px;
background: yellow;
position: relative;
}
</style>
<div id="box"></div>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/testdriver.js"></script>
<script src="/resources/testdriver-actions.js"></script>
<script src="/resources/testdriver-vendor.js"></script>
<script src="resources/util.js"></script>
<script>
const box = document.querySelector("#box");
box.addEventListener("pointerdown", (e) => {
// Generate a layout shift before we know what type of input this pointer
// event sequence will become.
box.style.top = "100px";
e.preventDefault();
});
generateScrollSequence = () => new test_driver.Actions()
.addPointer("tp1", "touch")
.pointerMove(0, 100, {sourceName: "tp1"})
.pointerDown({sourceName: "tp1"})
.pointerMove(0, 0, {sourceName: "tp1"})
.pause(100)
.pointerUp({sourceName: "tp1"})
.pause(100);
promise_test(async () => {
const watcher = new ScoreWatcher;
// Wait for the initial render to complete.
await waitForAnimationFrames(2);
// Send pointer events for a touch scroll.
await generateScrollSequence().send();
// The box is 400 x 500 and moves by 100px.
const expectedScore = computeExpectedScore(400 * (500 + 100), 100);
// Both scores should increase (scroll doesn't count as input for the purpose
// of the LayoutShift.hadRecentInput bit).
assert_equals(watcher.score, expectedScore);
assert_equals(watcher.scoreWithInputExclusion, expectedScore);
}, "Shift in pointerdown reported when it becomes a scroll.");
</script>
Codebase Browser
chromium