test_flushing_frame.html

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<!doctype html>

<meta charset="utf-8">

<title>

  Test for bug 1545516: We don't flush layout unnecessarily on the parent

  document when the frame is already disconnected.

</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 iframe = document.createElement("iframe");

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

  const parentUtils = SpecialPowers.getDOMWindowUtils(window);

  iframe.onload = function() {

    const win = iframe.contentWindow;

    iframe.offsetTop; // flush layout

    content.style.display = "inline"; // Dirty style with something that will reframe.

    const previousConstructCount = parentUtils.framesConstructed;

    let pagehideRan = false;

    win.addEventListener("pagehide", function() {

      pagehideRan = true;

      win.foo = win.innerWidth;

      is(parentUtils.framesConstructed, previousConstructCount, "innerWidth shouldn't have flushed parent document layout")

      win.bar = win.document.documentElement.offsetHeight;

      is(parentUtils.framesConstructed, previousConstructCount, "offsetHeight shouldn't have flushed parent document layout")

      win.baz = win.getComputedStyle(win.document.documentElement).color;

      is(parentUtils.framesConstructed, previousConstructCount, "getComputedStyle shouldn't have flushed parent document layout")

});

    iframe.remove(); // Remove the iframe

    is(pagehideRan, true, "pagehide handler should've ran");

    is(parentUtils.framesConstructed, previousConstructCount, "Nothing should've flushed the parent document layout yet");

    content.offsetTop;

    isnot(parentUtils.framesConstructed, previousConstructCount, "We should've flushed layout now");

    SimpleTest.finish();

};

  document.body.appendChild(iframe);

</script>