test_rem_unit.html

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<!--

https://bugzilla.mozilla.org/show_bug.cgi?id=478321

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<head>

  <title>Test for CSS 'rem' unit</title>

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

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

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<body>

<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=478321">Mozilla Bug 478321</a>

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<p id="display2"></p>

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<pre id="test">

<script type="application/javascript">

/** Test for CSS 'rem' unit **/

function px_to_num(str)

    return Number(String(str).match(/^([\d.]+)px$/)[1]);

function fs(elt)

    return px_to_num(getComputedStyle(elt, "").fontSize);

var html = document.documentElement;

var body = document.body;

var p = document.getElementById("display");

var p2 = document.getElementById("display2");

html.style.font = "initial";

var defaultFontSize = fs(html);

// NOTE:  This test assumes that the default font size is an

// integral number of pixels (which is always the case at present).

// If that ever becomes false, the calls to "is" may need to be replaced by

// calls to "isapprox" that allows errors of up to some small fraction

// of a pixel.

html.style.fontSize = "3rem";

is(fs(html), 3 * defaultFontSize,

   "3rem on root should triple root's font size");

body.style.font = "initial";

is(fs(body), defaultFontSize,

   "initial should produce initial font size");

body.style.fontSize = "1em";

is(fs(body), 3 * defaultFontSize, "1em should inherit from parent");

body.style.fontSize = "200%";

is(fs(body), 6 * defaultFontSize, "200% should double parent");

body.style.fontSize = "2rem";

is(fs(body), 6 * defaultFontSize, "2rem should double root");

p.style.font = "inherit";

is(fs(p), 6 * defaultFontSize, "inherit should inherit from parent");

p2.style.fontSize = "2rem";

is(fs(p2), 6 * defaultFontSize, "2rem should double root");

body.style.font = "initial";

is(fs(p), defaultFontSize, "inherit should inherit from parent");

is(fs(p2), 6 * defaultFontSize, "2rem should double root");

body.style.fontSize = "5em";

html.style.fontSize = "200%";

is(fs(p), 10 * defaultFontSize, "inherit should inherit from parent");

is(fs(p2), 4 * defaultFontSize, "2rem should double root");

// Make things readable again.

html.style.fontSize = "1em";

body.style.fontSize = "1em";

</script>

</pre>

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