mozilla-release/layout/style/test/test_computed_style_prefs.html

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  <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.touch_action.enabled": ["touch-action"],
  "svg.transform-box.enabled": ["transform-box"]
};

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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