<!doctype html>
<title>Text fragment navigation helper.</title>

<script src="/scroll-to-text-fragment/stash.js"></script>
<script>
function isInView(element) {
  let rect = element.getBoundingClientRect();
  return rect.top >= 0 && rect.top <= window.innerHeight
      && rect.left >= 0 && rect.left <= window.innerWidth;
}
function checkScroll() {
  let position = 'unknown';
  if (window.scrollY == 0)
    position = 'top';
  else if(isInView(document.getElementById("text")))
    position = 'text';
  else if(isInView(document.getElementById("text2")))
    position = 'text2';
  else if(isInView(document.getElementById("text3")))
    position = 'text3';

  const target = document.querySelector(":target");
  let results = {
    scrollPosition: position,
    href: window.location.href,
    target: target ? target.id : 'undefined'
  };
  let key = (new URL(document.location)).searchParams.get("key");
  stashResultsThenClose(key, results);
}
function doubleRafCheckScroll() {
  requestAnimationFrame(() => {
    requestAnimationFrame(() => {
      checkScroll();
    });
  });
}
</script>

<style>
.spacer {
  height: 10000px;
}
.auto {
  content-visibility: auto;
}
</style>

<body onload="doubleRafCheckScroll()">
<div class=spacer></div>
<div class=auto>
  <div id=text>hiddentext</div>
</div>
<div class=spacer></div>
<div id=text2and3ancestor>
  <div class=auto>
    <div id=text2>start</div>
  </div>
  <div class=spacer></div>
  <div class=auto>
    <div id=text3>end</div>
  </div>
</div>
</body>
