getComputedStyle-display-none-shadow-invalidation.html

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This WPT test may be referenced by the following Test IDs:
- /css/cssom/getComputedStyle-display-none-shadow-invalidation.html - WPT Dashboard Interop Dashboard

<!doctype html>

<meta charset="utf-8">

<title>CSSOM: getComputedStyle gets invalidated inside shadow trees of a display: none host</title>

<link rel="help" href="https://drafts.csswg.org/cssom/#dom-window-getcomputedstyle">

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<style>

#slotHost, #nestedHost {

  display: none;

  color: red;

</style>

<div id="slotHost"><div id="slotted"></div></div>

<div id="nestedHost"></div>

<script>

  test(function() {

    slotHost.attachShadow({ mode: 'open' }).innerHTML = `

      <div><slot></slot></div>

`;

    // Read before mutating so there is a cached computed style that can go stale.

    let slotted_style = getComputedStyle(slotted);

    assert_equals(slotted_style.color, "rgb(255, 0, 0)");

    slotHost.style.color = "green";

    // Force a style update: a stale cache is only observable once the host itself has been

    // re-resolved, which is what drops the invalidation flag the lookup would otherwise use.

    document.body.offsetHeight;

    assert_equals(slotted_style.color, "rgb(0, 128, 0)");

    assert_equals(getComputedStyle(slotted).color, "rgb(0, 128, 0)");

  }, "getComputedStyle gets invalidated for slotted content of a display: none shadow host");

  test(function() {

    nestedHost.attachShadow({ mode: 'open' }).innerHTML = `

      <div id="inner"></div>

`;

    let inner = nestedHost.shadowRoot.getElementById("inner");

    inner.attachShadow({ mode: 'open' }).innerHTML = `

      <div></div>

`;

    let innermost = inner.shadowRoot.firstElementChild;

    let inner_style = getComputedStyle(inner);

    let innermost_style = getComputedStyle(innermost);

    assert_equals(inner_style.color, "rgb(255, 0, 0)");

    assert_equals(innermost_style.color, "rgb(255, 0, 0)");

    nestedHost.style.color = "green";

    document.body.offsetHeight;

    assert_equals(inner_style.color, "rgb(0, 128, 0)");

    assert_equals(innermost_style.color, "rgb(0, 128, 0)");

    assert_equals(getComputedStyle(innermost).color, "rgb(0, 128, 0)");

  }, "getComputedStyle gets invalidated in nested shadow trees of a display: none shadow host");

</script>