transformed_scrolling_repaints_3_window.html

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<!DOCTYPE HTML>

<html style="overflow: hidden;">

<head>

  <title>Test that scaled elements with scrolled contents don't repaint unnecessarily when we scroll inside them</title>

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

</head>

<!-- Need a timeout here to allow paint unsuppression before we start the test -->

<body onload="setTimeout(startTest,0)" style="background:white;">

<iframe id="t" style="transform: scale(0.48979); transform-origin:top left; width:500px; height:600px;"

        src="transformed_scrolling_repaints_3_window_frame.html">

</iframe>

<pre id="test">

<script type="application/javascript">

var SimpleTest = window.opener.SimpleTest;

var SpecialPowers = window.opener.SpecialPowers;

var is = window.opener.is;

var smoothScrollPref = "general.smoothScroll";

function startTest() {

  SpecialPowers.pushPrefEnv({"set":[[smoothScrollPref, false]]}, runTest);

async function runTest() {

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

  let e = t.contentDocument.getElementById("e");

  t.contentWindow.scrollTo(0,0);

  let utils = SpecialPowers.getDOMWindowUtils(window);

  for (let i = 0; i < 15; i++) {

    let painted = utils.checkAndClearPaintedState(e);

    // We ignore the first few scrolls, to ensure we have triggered activity

    // heuristics.

    if (i >= 5) {

      is(painted, false,

         "Fully-visible scrolled element should not have been painted");

    t.contentWindow.scrollByLines(1);

    await promiseAllPaintsDone(null, true);

  SimpleTest.finish();

  window.close();

</script>

</pre>

</body>

</html>