popover-beforetoggle-opening-event.html

<!DOCTYPE html>
<meta charset="utf-8" />
<title>Popover beforetoggle event</title>
<link rel="author" href="mailto:[email protected]">
<link rel=help href="https://open-ui.org/components/popover.research.explainer">
<link rel=help href="https://html.spec.whatwg.org/multipage/popover.html">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<div popover></div>

<script>
test(() => {
  let frameCount = 0;
  requestAnimationFrame(() => {++frameCount;});
  const popover = document.querySelector('[popover]');
  const testText = 'Show Event Occurred';
  popover.addEventListener('beforetoggle',(e) => {
    assert_false(e.bubbles, 'beforetoggle event does not bubble');
    if (e.newState !== "open")
      return;
    popover.textContent = testText;
  })
  popover.offsetHeight;
  assert_equals(popover.textContent,"");
  assert_equals(frameCount,0);
  popover.showPopover();
  popover.offsetHeight;
  assert_equals(popover.textContent,testText);
  assert_equals(frameCount,0,'nothing should be rendered before the popover is updated');
  popover.hidePopover(); // Cleanup
},'Ensure the `beforetoggle` event can be used to populate content before the popover renders');
</script>

chromium/third_party/blink/web_tests/external/wpt/html/semantics/popovers/popover-beforetoggle-opening-event.html