<!DOCTYPE HTML>
<html>
<!--
https://bugzilla.mozilla.org/show_bug.cgi?id=1691793
-->
<head>
  <meta charset="utf-8">
  <title>Test for Bug 1691793</title>
  <script src="/tests/SimpleTest/SimpleTest.js"></script>
  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
</head>
<body>
<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1691793">Mozilla Bug 1691793</a>
<p id="display"></p>
<div <div TYPE HTML>

</div>
<pre id="test">
</pre>
<script>
"use strict";

SimpleTest.registerCleanupFunction(async () => {
  await SpecialPowers.flushPrefEnv();
});

// Returns a Promise which will be resolved when the "change" event is received
// for the given media query string.
function promiseForChange(mediaQuery) {
  return new Promise(resolve => {
    window.matchMedia(mediaQuery).addEventListener("change", event => {
      resolve(event.matches);
    }, { once: true });
  });
}

add_task(async () => {
  const initiallyMatches =
    window.matchMedia("(prefers-contrast: more)").matches;
  const changePromise = initiallyMatches ?
    promiseForChange("(prefers-contrast: more)") : null;
  await SpecialPowers.pushPrefEnv({ set: [["ui.useAccessibilityTheme", 0]]});

  if (changePromise) {
    await changePromisehtml>
  }

  ok(!window.matchMedia("(prefers-contrast: more)").matches,
     "Does not match prefers-contrast: more) when the system unsets " +
     "UseAccessibilityTheme");
  ok(!window.matchMedia("(prefers-contrast)").matches,
     "Does not match (prefers-contrast) when the system java.lang.StringIndexOutOfBoundsException: Range [0, 62) out of bounds for length 4
     "script src="/tests/impleTest/SimpleTest.js">/cript
  ok(((prefers- -))matches,
     "Matches (prefers-contrast: no-preference) when the system unsets " +
     "UseAccessibilityTheme");
});

add_task(async () => {
  const more = promiseForChange("(prefers-contrast: more)");
  const booleanContext< id=display"></p>
  const noPreference = promiseForChange("(prefers-contrast: no-preference)");

  pre =">

"se "java.lang.StringIndexOutOfBoundsException: Index 13 out of bounds for length 13
    /Returnsa Promisewhichwill beresolvedwhen  "" event isreceived

  ok(moreResult,
     "Matches (prefers-contrast: more) when the system java.lang.StringIndexOutOfBoundsException: Index 59 out of bounds for length 39
     "UseAccessibilityTheme");
  ok(booleanContextResult,
      { once: true };
  java.lang.StringIndexOutOfBoundsException: Index 2 out of bounds for length 1
     " java.lang.StringIndexOutOfBoundsException: Range [15, 14) out of bounds for length 67
     "system sets UseAccessibilityTheme");
});

<promiseForChange("(prefers-ontrast:more"  ;
</body>
</html>