layout/style/test/test_webkit_device_pixel_ratio.html

<!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>