test_invalidation_basic.html

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<!doctype html>

<meta charset="utf-8">

<title>

  Test for bug 1368240: We only invalidate style as little as needed

</title>

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

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

<style>

.foo .bar {

  color: red;

#container ~ .bar {

  color: green;

</style>

<div id="container">

  <div></div>

  <div></div>

  <div></div>

</div>

<div></div>

<div></div>

<script>

SimpleTest.waitForExplicitFinish();

const utils = SpecialPowers.getDOMWindowUtils(window);

// TODO(emilio): Add an API to get the ComputedStyles we've recreated, to make

// more elaborated tests.

document.documentElement.offsetTop;

const initialRestyleGeneration = utils.restyleGeneration;

// Normally we'd restyle the whole subtree in this case, but we should go down

// the tree invalidating as little as needed (nothing in this case).

container.classList.add("foo");

document.documentElement.offsetTop;

is(utils.restyleGeneration, initialRestyleGeneration,

   "Shouldn't have restyled any descendant");

container.setAttribute("id", "");

document.documentElement.offsetTop;

is(utils.restyleGeneration, initialRestyleGeneration,

   "Shouldn't have restyled any sibling");

SimpleTest.finish();

</script>