test_bug1151421.html

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<html>

<!--

https://bugzilla.mozilla.org/show_bug.cgi?id=1151421

-->

<head>

  <title>Test for Bug 1151421</title>

  <script src="/tests/SimpleTest/SimpleTest.js"></script>

  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>

</head>

<body>

<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1151421">Mozilla Bug 1151421</a>

<script type="application/javascript">

/** Test for Bug 1151421 */

SimpleTest.waitForExplicitFinish();

function childLoad() {

  // Spin the event loop so we leave the onload handler.

  SimpleTest.executeSoon(childLoad2);

function childLoad2() {

  let iframe = document.getElementById("iframe");

  let cw = iframe.contentWindow;

  let content = cw.document.getElementById("content");

  // Create a function to calculate an invariant.

  let topPlusOffset = function() {

    return Math.round(content.getBoundingClientRect().top + cw.pageYOffset);

};

  let initialTPO = topPlusOffset();

  // Scroll the iframe to various positions, and check the TPO.

  // Scrolling down to the bottom will adjust the page offset by a fractional amount.

  let positions = [-100, 0.17, 0, 1.5, 10.41, 1e6, 12.1];

  // Run some tests with scrollTo() and ensure we have the same invariant after scrolling.

  positions.forEach(function(pos) {

    cw.scrollTo(0, pos);

    is(topPlusOffset(), initialTPO, "Top plus offset should remain invariant across scrolling.");

});

  positions.reverse().forEach(function(pos) {

    cw.scrollTo(0, pos);

    is(topPlusOffset(), initialTPO, "(reverse) Top plus offset should remain invariant across scrolling.");

});

  SimpleTest.finish();

</script>

<!-- When the iframe loads, it calls childLoad(). -->

<br>

<iframe height='100px' id='iframe' src='file_bug1151421.html'></iframe>

</body>

</html>