<!DOCTYPE html>
<title>Moving fullscreen document's body into a fullscreen iframe</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/testdriver.js"></script>
<script src="/resources/testdriver-vendor.js"></script>
<script src="../trusted-click.js"></script>
<iframe allowfullscreen></iframe>
<script>
  promise_test(async (t) => {
    t.add_cleanup(() => {
      if (document.fullscreenElement) {
        return document.exitFullscreen();
      }
    });
    const iframe = document.querySelector("iframe");
    await new Promise((resolve) => {
      iframe.onload = resolve;
      iframe.src = "about:blank";
    });
    const iframeDoc = iframe.contentDocument;

    // Enter fullscreen for the iframe's body element.
    await Promise.all([
      trusted_request(iframeDoc.body, iframeDoc.body),
      fullScreenChange(),
    ]);

    assert_equals(
      document.fullscreenElement,
      iframe,
      "document's initial fullscreen element"
    );
    assert_equals(
      iframeDoc.fullscreenElement,
      iframeDoc.body,
      "iframe's initial fullscreen element"
    );

    // Then, move the outer document's body into the iframe. This is an unusual
    // thing to do, but means that the iframe is removed from its document and
    // should trigger fullscreen exit.
    iframeDoc.documentElement.appendChild(document.body);

    // If we exit in an orderly fashion, that's all one can ask for.
    await fullScreenChange();
    assert_equals(
      document.fullscreenElement,
      null,
      "document's final fullscreen element"
    );

    // Because the iframe was removed, its browsing context was discarded and
    // its contentDocument has become null. Because that browsing context was
    // neither a descendant browsing context nor had an active document,
    // nothing at all was done with it in the exit fullscreen algorithm, so
    // its fullscreenElement is unchanged.
    assert_equals(iframe.contentDocument, null, "iframe's content document");
    assert_equals(
      iframeDoc.fullscreenElement,
      iframeDoc.body,
      "iframe's final fullscreen element"
    );
  });
</script>
