content-visibility-auto-state-changed-first-observation.html

<!doctype HTML>
<html>
<meta charset="utf8">
<title>Content Visibility: ContentVisibilityAutoStateChange event.</title>
<link rel="author" title="Vladimir Levin" href="mailto:[email protected]">
<link rel="help" href="https://drafts.csswg.org/css-contain/#content-visibility">
<meta name="assert" content="ContentVisibilityAutoStateChange fires once when element is inserted">

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<style>
.spacer {
  height: 10000px;
}
</style>

<div id=topdiv></div>
<div class=spacer></div>
<div id=bottomdiv></div>

<script>
promise_test(t => new Promise(async (resolve, reject) => {
  await new Promise((waited, _) => {
    requestAnimationFrame(() => requestAnimationFrame(waited));
  });

  let observed = false;
  let div = document.createElement("div");
  div.addEventListener("contentvisibilityautostatechange", (e) => {
    if (observed)
      reject("already observed");
    if (e.skipped)
      reject("unexpected skipped");
    observed = true;
    // Wait a couple of frames to ensure no other signal comes in
    requestAnimationFrame(() => requestAnimationFrame(resolve));
  });

  div.style.contentVisibility = "auto";
  topdiv.appendChild(div);
}), "ContentVisibilityAutoStateChange fires once when added (not skipped)");

promise_test(t => new Promise(async (resolve, reject) => {
  await new Promise((waited, _) => {
    requestAnimationFrame(() => requestAnimationFrame(waited));
  });

  let observed = false;
  let div = document.createElement("div");
  div.addEventListener("contentvisibilityautostatechange", (e) => {
    if (observed)
      reject("already observed");
    if (!e.skipped)
      reject("unexpected not skipped");
    observed = true;
    // Wait a couple of frames to ensure no other signal comes in
    requestAnimationFrame(() => requestAnimationFrame(resolve));
  });

  div.style.contentVisibility = "auto";
  bottomdiv.appendChild(div);
}), "ContentVisibilityAutoStateChange fires once when added (skipped)");
</script>
chromium/third_party/blink/web_tests/external/wpt/css/css-contain/content-visibility/content-visibility-auto-state-changed-first-observation.html
