MediaQueryList-change-event-matches-value.html

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This WPT test may be referenced by the following Test IDs:
- /css/cssom-view/MediaQueryList-change-event-matches-value.html - WPT Dashboard Interop Dashboard

<!doctype html>

<title>MediaQueryList.changed is correct for all lists in the document even during a change event handler</title>

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

<link rel="author" href="https://mozilla.org" title="Mozilla">

<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1648839">

<link rel="help" href="https://drafts.csswg.org/cssom-view/#evaluate-media-queries-and-report-changes">

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

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

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

<body>

<script>

  promise_test(async t => {

    // Create two identical media queries.

    let mql = await createMQL(t);

    let mql2 = getWindow(mql).matchMedia(mql.media);

    let changeEvents = 0;

    let check = t.step_func(function() {

      changeEvents++;

      assert_equals(mql.matches, mql2.matches, "Value of .matches should match"); // No pun intended

});

    mql.addListener(check);

    mql2.addListener(check);

    triggerMQLEvent(mql);

    await waitForChangesReported();

    assert_equals(changeEvents, 2, "Should've fired the change event in both MediaQueryLists");

});

</script>