<!doctype html>
<title>Test for bug 1617342</title>
<script src="/tests/SimpleTest/SimpleTest.js"></script>
<script src="/tests/SimpleTest/EventUtils.js"></script>
<style>
  :root {
    scroll-padding: 100px 0;
  }
  body {
    margin: 0;
  }
  #fixed-footer {
    height: 100px;
    position: fixed;
    bottom: 0;
    left: 0;
    width: 100%;
    background: green;
  }
  #fixed-header {
    height: 100px;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    background: green;
  }
  .almost-full-padding {
    height: calc(100vh - 200px);
  }
  .padding {
    height: 100vh;
  }
</style>
<div id="fixed-header"></div>
<div class="padding"></div>
<input>
<div class="almost-full-padding"></div>
<input>
<div class="padding"></div>
<input id="end">
<div class="padding"></div>
<div id="fixed-footer"></div>
<script>
  SimpleTest.waitForExplicitFinish();
  SimpleTest.waitForFocus(async function() {
    let stack = [];
    let end = document.getElementById("end");

    let lastActiveElement = document.activeElement;

    do {
      synthesizeKey("KEY_Tab");
      is(document.activeElement.tagName, "INPUT", "Should focus inputs only, there's nothing else");
      isnot(document.activeElement, lastActiveElement, "Focus should've moved once per tab keypress");
      let rect = document.activeElement.getBoundingClientRect();
      ok(rect.top >= 100, "Should not be covered by top bar");
      ok(rect.bottom >= 100, "Should not be covered by bottom bar");
      lastActiveElement = document.activeElement;
      stack.push(lastActiveElement);
    } while (document.activeElement != end)

    do {
      let previous = stack.pop();
      let rect = document.activeElement.getBoundingClientRect();
      ok(rect.top >= 100, "Should not be covered by top bar");
      ok(rect.bottom >= 100, "Should not be covered by bottom bar");
      is(document.activeElement, previous, "Focus should've moved backwards as expected");
      synthesizeKey("KEY_Tab", {shiftKey: true});
    } while (stack.length);

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