test_reframe_cb.html

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<!doctype html>

<meta charset="utf-8">

<title>

  Test for bug 1519371: We don't reframe for changes that affect our containing

  block status unless whether we're a containing block really changed.

</title>

<link rel="author" href="mailto:emilio@crisal.io" title="Emilio Cobos Álvarez">

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

<div id="content"></div>

<script>

SimpleTest.waitForExplicitFinish();

const utils = SpecialPowers.getDOMWindowUtils(window);

function expectReframe(shouldHaveReframed, callback) {

  document.documentElement.offsetTop;

  const previousConstructCount = utils.framesConstructed;

  const previousRestyleGeneration = utils.restyleGeneration;

  callback();

  document.documentElement.offsetTop;

  isnot(previousRestyleGeneration, utils.restyleGeneration,

        "We should have restyled");

  (shouldHaveReframed ? isnot : is)(previousConstructCount,

                                    utils.framesConstructed,

    `We should ${shouldHaveReframed ? "" : "not"} have reframed`);

const content = document.getElementById("content");

// Without fixed-pos descendants, we should not reframe.

expectReframe(false, () => {

  content.style.transform = "scale(1)";

});

content.style.transform = "";

content.innerHTML = `<div style="position: fixed"></div>`;

// With fixed-pos descendants, got to reframe.

expectReframe(true, () => {

  content.style.transform = "scale(1)";

});

// If our containing-block-ness didn't change, we should not need to reframe.

expectReframe(false, () => {

  content.style.willChange = "transform";

});

// If it does change, we need to reframe.

expectReframe(true, () => {

  content.style.willChange = "";

  content.style.transform = "";

});

SimpleTest.finish();

</script>