test_scrollframe_abspos_interrupt.html

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<!doctype html>

<title>Test for bug 1526609</title>

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

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

<style>

  body {

    margin: 0;

  .scroller {

    overflow-y: auto;

    position: relative;

    width: 500px;

    height: 300px;

  .kid {

    position: absolute;

    width: 100%;

    background: linear-gradient(to bottom, red, green);

    line-height: 100px;

</style>

<div class="scroller" id="scroller">

  <div class="kid"></div>

</div>

<script>

  let text = " foo bar ";

  for (let i = 0; i < 16; ++i)

    text = text + text;

  document.querySelector(".kid").innerText = text;

SimpleTest.waitForExplicitFinish();

const scroller = document.querySelector("#scroller");

is(scroller.scrollTop, 0, "Initial scroll position");

ok(scroller.scrollTopMax > 0, "Should be able to scroll down");

scroller.scrollTop = scroller.scrollTopMax;

is(scroller.scrollTop, scroller.scrollTopMax, "Should've scrolled");

const origWidth = scroller.offsetWidth;

const utils = SpecialPowers.DOMWindowUtils;

// Take control of the refresh driver

utils.advanceTimeAndRefresh(0);

// Force the next reflow to get interrupted

utils.forceReflowInterrupt();

scroller.style.width = "300px";

utils.advanceTimeAndRefresh(0);

isnot(scroller.scrollTop, 0, "Shouldn't have lost scroll position");

isnot(scroller.offsetWidth, origWidth, "Should've had to reflow");

utils.restoreNormalRefresh();

SimpleTest.finish();

</script>