test_computed_style_prefs.html

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<head>

  <title>Test that preffed off properties do not appear in computed style</title>

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

  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>

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<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=919594">Mozilla Bug 919594</a>

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<pre id="test">

<script type="application/javascript">

/** Test that preffed off properties do not appear in computed style **/

function testWithAllPrefsDisabled() {

  let exposedProperties = Object.keys(gCS).map(i => gCS[i]);

  // Store the number of properties for later tests to use.

  gLengthWithAllPrefsDisabled = gCS.length;

  // Check that all of the properties behind the prefs are not exposed.

  for (let pref in gProps) {

    for (let prop of gProps[pref]) {

      ok(!exposedProperties.includes(prop), prop + " not exposed when prefs are false");

function testWithOnePrefEnabled(aPref) {

  let exposedProperties = Object.keys(gCS).map(i => gCS[i]);

  // Check that the number of properties on the object is as expected.

  is(gCS.length, gLengthWithAllPrefsDisabled + gProps[aPref].length, "length when " + aPref + " is true");

  // Check that the properties corresponding to aPref are exposed.

  for (let prop of gProps[aPref]) {

    ok(exposedProperties.includes(prop), prop + " exposed when " + aPref + " is true");

function step() {

  if (gTestIndex == gTests.length) {

    // Reached the end of the tests.

    SimpleTest.finish();

    return;

  if (gPrefsPushed) {

    // We've just finished running one tests.  Pop the prefs and go on to

    // the next test.

    gTestIndex++;

    gPrefsPushed = false;

    SpecialPowers.popPrefEnv(step);

    return;

  // About to run one test.  Push the prefs and run it.

  let fn = gTests[gTestIndex].fn;

  gPrefsPushed = true;

  SpecialPowers.pushPrefEnv(gTests[gTestIndex].settings,

                            function() { fn(); SimpleTest.executeSoon(step); });

// ----

var gProps = {

  "layout.css.backdrop-filter.enabled": ["backdrop-filter"],

};

var gCS = getComputedStyle(document.body, "");

var gLengthWithAllPrefsDisabled;

var gTestIndex = 0;

var gPrefsPushed = false;

var gTests = [

  // First, test when all of the prefs are disabled.

  { settings: { set: Object.keys(gProps).map(x => [x, false]) },

    fn:       testWithAllPrefsDisabled },

  // Then, test each pref enabled individually.

  ...Object.keys(gProps).map(p =>

    ({ settings: { set: Object.keys(gProps).map(x => [x, x == p]) },

       fn:       testWithOnePrefEnabled.bind(null, p) }))

];

SimpleTest.waitForExplicitFinish();

step();

</script>

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