test_webkit_device_pixel_ratio.html

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<!DOCTYPE HTML>

<html>

<!--

https://bugzilla.mozilla.org/show_bug.cgi?id=1176968

-->

<head>

  <title>Test for Bug 1176968</title>

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

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

  <style>.zoom-test { visibility: hidden; }</style>

  <style><!-- placeholder for dynamic additions --></style>

</head>

<body onload="run()">

<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1176968">Mozilla Bug 1176968</a>

<div id="content" style="display: none">

</div>

<script type="text/javascript">

</script>

<pre id="test">

<div id="zoom1" class="zoom-test"></div>

<div id="zoom2" class="zoom-test"></div>

<div id="zoom3" class="zoom-test"></div>

<script class="testbody" type="application/javascript">

/** Test for Bug 1176968 **/

SimpleTest.waitForExplicitFinish();

function run() {

  function zoom(factor) {

    var previous = SpecialPowers.getFullZoom(window);

    SpecialPowers.setFullZoom(window, factor);

    return previous;

  function isVisible(divName) {

    return window.getComputedStyle(document.getElementById(divName)).visibility == "visible";

  var screenPixelsPerCSSPixel = window.devicePixelRatio;

  var baseRatio = 1.0 * screenPixelsPerCSSPixel;

  var doubleRatio = 2.0 * screenPixelsPerCSSPixel;

  var halfRatio = 0.5 * screenPixelsPerCSSPixel;

  var styleElem = document.getElementsByTagName("style")[1];

  styleElem.textContent =

      ["@media all and (-webkit-device-pixel-ratio: " + baseRatio + ") {",

         "#zoom1 { visibility: visible; }",

       "}",

       "@media all and (-webkit-device-pixel-ratio: " + doubleRatio + ") {",

         "#zoom2 { visibility: visible; }",

       "}",

       "@media all and (-webkit-device-pixel-ratio: " + halfRatio + ") {",

         "#zoom3 { visibility: visible; }",

"}"

      ].join("\n");

  ok(isVisible("zoom1"), "Base ratio rule should apply at base zoom level");

  ok(!isVisible("zoom2") && !isVisible("zoom3"), "no other rules should apply");

  var origZoom = zoom(2);

  ok(isVisible("zoom2"), "Double ratio rule should apply at double zoom level");

  ok(!isVisible("zoom1") && !isVisible("zoom3"), "no other rules should apply");

  zoom(0.5);

  ok(isVisible("zoom3"), "Half ratio rule should apply at half zoom level");

  ok(!isVisible("zoom1") && !isVisible("zoom2"), "no other rules should apply");

  zoom(origZoom);

  SimpleTest.finish();

</script>

</pre>

</body>

</html>