<!doctype html>
<title>Test for bug 1544826</title>
<script src="/tests/SimpleTest/SimpleTest.js"></script>
<script src="/tests/SimpleTest/EventUtils.js"></script>
<div id="host"><a href="#" id="slotted">This is focusable too</a></div>
<script>
  const host = document.getElementById("host");
  const shadow = host.attachShadow({ mode: "open" });
  shadow.innerHTML = `
    <a id="shadow-1" href="#">This is focusable</a>
    <slot></slot>
    <a id="shadow-2" href="#">So is this</a>
  `;
  document.documentElement.remove();
  document.appendChild(host);

  SimpleTest.waitForExplicitFinish();
  SimpleTest.waitForFocus(async function() {
    // Enable Full Keyboard Access emulation on Mac.
    if (navigator.platform.indexOf("Mac") === 0) {
      await SpecialPowers.pushPrefEnv({"set": [["accessibility.tabfocus", 7]]});
    }

    is(document.documentElement, host, "Host is the document element");
    host.offsetTop;
    synthesizeKey("KEY_Tab");
    is(shadow.activeElement.id, "shadow-1", "First link in Shadow DOM is focused");
    synthesizeKey("KEY_Tab");
    is(document.activeElement.id, "slotted", "Slotted link is focused");
    synthesizeKey("KEY_Tab");
    is(shadow.activeElement.id, "shadow-2", "Second link in Shadow DOM is focused");

    // Now backwards.
    synthesizeKey("KEY_Tab", {shiftKey: true});
    is(document.activeElement.id, "slotted", "Backwards: Slotted link is focused");
    synthesizeKey("KEY_Tab", {shiftKey: true});
    is(shadow.activeElement.id, "shadow-1", "Backwards: First slotted link is focused");

    SimpleTest.finish();
  });
</script>
