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<!doctype html><html lang="en">
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
<title>CSS Step Sizing</title>
<meta content="width=device-width, initial-scale=1, shrink-to-fit=no" name="viewport">
<meta content="exploring" name="csswg-work-status">
<meta content="ED" name="w3c-status">
<link href="../default.css" rel="stylesheet" type="text/css">
<link href="../csslogo.ico" rel="shortcut icon" type="image/x-icon">
<style>
body {
background-image: url("https://www.w3.org/StyleSheets/TR/logo-ED");
};
</style>
<meta content="Bikeshed 1.0.0" name="generator">
<style>
.example .figure img {
background-color: white;
padding: 20px;
margin: 20px;
}
</style>
<style>/* style-md-lists */
/* This is a weird hack for me not yet following the commonmark spec
regarding paragraph and lists. */
[data-md] > :first-child {
margin-top: 0;
}
[data-md] > :last-child {
margin-bottom: 0;
}</style>
<style>/* style-selflinks */
.heading, .issue, .note, .example, li, dt {
position: relative;
}
a.self-link {
position: absolute;
top: 0;
left: calc(-1 * (3.5rem - 26px));
width: calc(3.5rem - 26px);
height: 2em;
text-align: center;
border: none;
transition: opacity .2s;
opacity: .5;
}
a.self-link:hover {
opacity: 1;
}
.heading > a.self-link {
font-size: 83%;
}
li > a.self-link {
left: calc(-1 * (3.5rem - 26px) - 2em);
}
dfn > a.self-link {
top: auto;
left: auto;
opacity: 0;
width: 1.5em;
height: 1.5em;
background: gray;
color: white;
font-style: normal;
transition: opacity .2s, background-color .2s, color .2s;
}
dfn:hover > a.self-link {
opacity: 1;
}
dfn > a.self-link:hover {
color: black;
}
a.self-link::before { content: "¶"; }
.heading > a.self-link::before { content: "§"; }
dfn > a.self-link::before { content: "#"; }</style>
<style>/* style-counters */
.issue:not(.no-marker)::before {
content: "Issue " counter(issue);
}
.example:not(.no-marker)::before {
content: "Example";
content: "Example " counter(example);
}
.invalid.example:not(.no-marker)::before,
.illegal.example:not(.no-marker)::before {
content: "Invalid Example";
content: "Invalid Example" counter(example);
}</style>
<style>/* style-autolinks */
.css.css, .property.property, .descriptor.descriptor {
color: #005a9c;
font-size: inherit;
font-family: inherit;
}
.css::before, .property::before, .descriptor::before {
content: "‘";
}
.css::after, .property::after, .descriptor::after {
content: "’";
}
.property, .descriptor {
/* Don't wrap property and descriptor names */
white-space: nowrap;
}
.type { /* CSS value <type> */
font-style: italic;
}
pre .property::before, pre .property::after {
content: "";
}
[data-link-type="property"]::before,
[data-link-type="propdesc"]::before,
[data-link-type="descriptor"]::before,
[data-link-type="value"]::before,
[data-link-type="function"]::before,
[data-link-type="at-rule"]::before,
[data-link-type="selector"]::before,
[data-link-type="maybe"]::before {
content: "‘";
}
[data-link-type="property"]::after,
[data-link-type="propdesc"]::after,
[data-link-type="descriptor"]::after,
[data-link-type="value"]::after,
[data-link-type="function"]::after,
[data-link-type="at-rule"]::after,
[data-link-type="selector"]::after,
[data-link-type="maybe"]::after {
content: "’";
}
[data-link-type].production::before,
[data-link-type].production::after,
.prod [data-link-type]::before,
.prod [data-link-type]::after {
content: "";
}
[data-link-type=element],
[data-link-type=element-attr] {
font-family: Menlo, Consolas, "DejaVu Sans Mono", monospace;
font-size: .9em;
}
[data-link-type=element]::before { content: "<" }
[data-link-type=element]::after { content: ">" }
[data-link-type=biblio] {
white-space: pre;
}</style>
<style>/* style-dfn-panel */
.dfn-panel {
display: inline-block;
position: absolute;
z-index: 35;
height: auto;
width: -webkit-fit-content;
max-width: 300px;
max-height: 500px;
overflow: auto;
padding: 0.5em 0.75em;
font: small Helvetica Neue, sans-serif, Droid Sans Fallback;
background: #DDDDDD;
color: black;
border: outset 0.2em;
}
.dfn-panel:not(.on) { display: none; }
.dfn-panel * { margin: 0; padding: 0; text-indent: 0; }
.dfn-panel > b { display: block; }
.dfn-panel a { color: black; }
.dfn-panel a:not(:hover) { text-decoration: none !important; border-bottom: none !important; }
.dfn-panel > b + b { margin-top: 0.25em; }
.dfn-panel > span { display: list-item; list-style: inside; }
.dfn-panel.activated {
display: inline-block;
position: fixed;
left: .5em;
bottom: .5em;
margin: 0 auto;
max-width: calc(100vw - 1.5em - .4em - .5em);
max-height: 30vh;
}
.dfn-paneled { cursor: pointer; }
</style>
<style>/* style-syntax-highlighting */
.highlight .hll { background-color: #ffffcc }
.highlight { background: #ffffff; }
.highlight .c { color: #708090 } /* Comment */
.highlight .k { color: #990055 } /* Keyword */
.highlight .l { color: #000000 } /* Literal */
.highlight .n { color: #0077aa } /* Name */
.highlight .o { color: #999999 } /* Operator */
.highlight .p { color: #999999 } /* Punctuation */
.highlight .ch { color: #708090 } /* Comment.Hashbang */
.highlight .cm { color: #708090 } /* Comment.Multiline */
.highlight .cp { color: #708090 } /* Comment.Preproc */
.highlight .cpf { color: #708090 } /* Comment.PreprocFile */
.highlight .c1 { color: #708090 } /* Comment.Single */
.highlight .cs { color: #708090 } /* Comment.Special */
.highlight .kc { color: #990055 } /* Keyword.Constant */
.highlight .kd { color: #990055 } /* Keyword.Declaration */
.highlight .kn { color: #990055 } /* Keyword.Namespace */
.highlight .kp { color: #990055 } /* Keyword.Pseudo */
.highlight .kr { color: #990055 } /* Keyword.Reserved */
.highlight .kt { color: #990055 } /* Keyword.Type */
.highlight .ld { color: #000000 } /* Literal.Date */
.highlight .m { color: #000000 } /* Literal.Number */
.highlight .s { color: #a67f59 } /* Literal.String */
.highlight .na { color: #0077aa } /* Name.Attribute */
.highlight .nc { color: #0077aa } /* Name.Class */
.highlight .no { color: #0077aa } /* Name.Constant */
.highlight .nd { color: #0077aa } /* Name.Decorator */
.highlight .ni { color: #0077aa } /* Name.Entity */
.highlight .ne { color: #0077aa } /* Name.Exception */
.highlight .nf { color: #0077aa } /* Name.Function */
.highlight .nl { color: #0077aa } /* Name.Label */
.highlight .nn { color: #0077aa } /* Name.Namespace */
.highlight .py { color: #0077aa } /* Name.Property */
.highlight .nt { color: #669900 } /* Name.Tag */
.highlight .nv { color: #0077aa } /* Name.Variable */
.highlight .ow { color: #999999 } /* Operator.Word */
.highlight .mb { color: #000000 } /* Literal.Number.Bin */
.highlight .mf { color: #000000 } /* Literal.Number.Float */
.highlight .mh { color: #000000 } /* Literal.Number.Hex */
.highlight .mi { color: #000000 } /* Literal.Number.Integer */
.highlight .mo { color: #000000 } /* Literal.Number.Oct */
.highlight .sb { color: #a67f59 } /* Literal.String.Backtick */
.highlight .sc { color: #a67f59 } /* Literal.String.Char */
.highlight .sd { color: #a67f59 } /* Literal.String.Doc */
.highlight .s2 { color: #a67f59 } /* Literal.String.Double */
.highlight .se { color: #a67f59 } /* Literal.String.Escape */
.highlight .sh { color: #a67f59 } /* Literal.String.Heredoc */
.highlight .si { color: #a67f59 } /* Literal.String.Interpol */
.highlight .sx { color: #a67f59 } /* Literal.String.Other */
.highlight .sr { color: #a67f59 } /* Literal.String.Regex */
.highlight .s1 { color: #a67f59 } /* Literal.String.Single */
.highlight .ss { color: #a67f59 } /* Literal.String.Symbol */
.highlight .vc { color: #0077aa } /* Name.Variable.Class */
.highlight .vg { color: #0077aa } /* Name.Variable.Global */
.highlight .vi { color: #0077aa } /* Name.Variable.Instance */
.highlight .il { color: #000000 } /* Literal.Number.Integer.Long */
.highlight { background: hsl(24, 20%, 95%); }
code.highlight { padding: .1em; border-radius: .3em; }
pre.highlight, pre > code.highlight { display: block; padding: 1em; margin: .5em 0; overflow: auto; border-radius: 0; }
</style>
<body class="h-entry">
<div class="head">
<p data-fill-with="logo"><a class="logo" href="http://www.w3.org/"> <img alt="W3C" height="48" src="https://www.w3.org/StyleSheets/TR/2016/logos/W3C" width="72"> </a> </p>
<h1 class="p-name no-ref" id="title">CSS Step Sizing</h1>
<h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="content">Editor’s Draft, <time class="dt-updated" datetime="2016-05-11">11 May 2016</time></span></h2>
<div data-fill-with="spec-metadata">
<dl>
<dt>This version:
<dd><a class="u-url" href="https://drafts.csswg.org/css-step-sizing/">https://drafts.csswg.org/css-step-sizing/</a>
<dt>Feedback:
<dd><span><a href="mailto:www-style@w3.org?subject=%5Bcss-step-sizing%5D%20YOUR%20TOPIC%20HERE">www-style@w3.org</a> with subject line “<kbd>[css-step-sizing] <i data-lt="">… message topic …</i></kbd>” (<a href="http://lists.w3.org/Archives/Public/www-style/" rel="discussion">archives</a>)</span>
<dt>Issue Tracking:
<dd><a href="#issues-index">Inline In Spec</a>
<dt class="editor">Editor:
<dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:kojiishi@gmail.com">Koji Ishii</a> (<span class="p-org org">Google</span>)
</dl>
</div>
<div data-fill-with="warning"></div>
<p class="copyright" data-fill-with="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2016 <a href="http://www.w3.org/"><abbr title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts Institute of Technology">MIT</abbr></a>, <a href="http://www.ercim.eu/"><abbr title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>, <a href="http://ev.buaa.edu.cn/">Beihang</a>). W3C <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>, <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a> rules apply. </p>
<hr title="Separator for header">
</div>
<h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2>
<div class="p-summary" data-fill-with="abstract">
<p>This module contains CSS features for aligning content size
to multiple of unit size.</p>
<a href="http://www.w3.org/TR/CSS/">CSS</a> is a language for describing the rendering of structured documents
(such as HTML and XML)
on screen, on paper, in speech, etc.
</div>
<h2 class="no-num no-toc no-ref heading settled" id="status"><span class="content">Status of this document</span></h2>
<div data-fill-with="status">
<p> This is a public copy of the editors’ draft.
It is provided for discussion only and may change at any moment.
Its publication here does not imply endorsement of its contents by W3C.
Don’t cite this document other than as work in progress. </p>
<p> The (<a href="http://lists.w3.org/Archives/Public/www-style/">archived</a>) public mailing list <a href="mailto:www-style@w3.org?Subject=%5Bcss-step-sizing%5D%20PUT%20SUBJECT%20HERE">www-style@w3.org</a> (see <a href="http://www.w3.org/Mail/Request">instructions</a>)
is preferred for discussion of this specification.
When sending e-mail,
please put the text “css-step-sizing” in the subject,
preferably like this:
“[css-step-sizing] <em>…summary of comment…</em>” </p>
<p> This document was produced by the <a href="http://www.w3.org/Style/CSS/members">CSS Working Group</a> (part of the <a href="http://www.w3.org/Style/">Style Activity</a>). </p>
<p> This document was produced by a group operating under
the <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February 2004 W3C Patent Policy</a>.
W3C maintains a <a href="http://www.w3.org/2004/01/pp-impl/32061/status" rel="disclosure">public list of any patent disclosures</a> made in connection with the deliverables of the group;
that page also includes instructions for disclosing a patent.
An individual who has actual knowledge of a patent which the individual believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential Claim(s)</a> must disclose the information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the W3C Patent Policy</a>. </p>
<p> This document is governed by the <a href="http://www.w3.org/2015/Process-20150901/" id="w3c_process_revision">1 September 2015 W3C Process Document</a>. </p>
<p></p>
</div>
<div data-fill-with="at-risk"></div>
<nav data-fill-with="table-of-contents" id="toc">
<h2 class="no-num no-toc no-ref" id="contents">Table of Contents</h2>
<ol class="toc" role="directory">
<li><a href="#intro"><span class="secno">1</span> <span class="content">Introduction</span></a>
<li>
<a href="#line-height-step"><span class="secno">2</span> <span class="content">Adjusting Line Box Heights: the <span class="property">line-height-step</span> property</span></a>
<ol class="toc">
<li><a href="#height"><span class="secno">2.1</span> <span class="content">Stepping Line Box Heights</span></a>
<li><a href="#baseline"><span class="secno">2.2</span> <span class="content">Aligning Baselines</span></a>
<li><a href="#block-height"><span class="secno">2.3</span> <span class="content">Notes on Block-level Boxes</span></a>
</ol>
<li><a href="#width"><span class="secno">3</span> <span class="content">Stepping Widths: the <span class="property">inline-size-step</span> property</span></a>
<li><a href="#priv-sec"><span class="secno">4</span> <span class="content">Privacy and Security Considerations</span></a>
<li><a href="#acks"><span class="secno">5</span> <span class="content">Acknowledgments</span></a>
<li>
<a href="#conformance"><span class="secno"></span> <span class="content"> Conformance</span></a>
<ol class="toc">
<li><a href="#document-conventions"><span class="secno"></span> <span class="content"> Document conventions</span></a>
<li><a href="#conform-classes"><span class="secno"></span> <span class="content"> Conformance classes</span></a>
<li>
<a href="#conform-responsible"><span class="secno"></span> <span class="content"> Requirements for Responsible Implementation of CSS</span></a>
<ol class="toc">
<li><a href="#conform-partial"><span class="secno"></span> <span class="content"> Partial Implementations</span></a>
<li><a href="#conform-future-proofing"><span class="secno"></span> <span class="content"> Implementations of Unstable and Proprietary Features</span></a>
<li><a href="#conform-testing"><span class="secno"></span> <span class="content"> Implementations of CR-level Features</span></a>
</ol>
</ol>
<li>
<a href="#index"><span class="secno"></span> <span class="content">Index</span></a>
<ol class="toc">
<li><a href="#index-defined-here"><span class="secno"></span> <span class="content">Terms defined by this specification</span></a>
<li><a href="#index-defined-elsewhere"><span class="secno"></span> <span class="content">Terms defined by reference</span></a>
</ol>
<li>
<a href="#references"><span class="secno"></span> <span class="content">References</span></a>
<ol class="toc">
<li><a href="#normative"><span class="secno"></span> <span class="content">Normative References</span></a>
<li><a href="#informative"><span class="secno"></span> <span class="content">Informative References</span></a>
</ol>
<li><a href="#property-index"><span class="secno"></span> <span class="content">Property Index</span></a>
<li><a href="#issues-index"><span class="secno"></span> <span class="content">Issues Index</span></a>
</ol>
</nav>
<main>
<h2 class="heading settled" data-level="1" id="intro"><span class="secno">1. </span><span class="content">Introduction</span><a class="self-link" href="#intro"></a></h2>
<p>This specification provides features to control sizes of CSS objects
according to the rules desired by use cases.</p>
<p>Controlling sizes of CSS objects to be multiple of a unit
is desired in many cases.
This level of the specification focuses on following cases.</p>
<ul>
<li data-md="">
<p>Adjust heights of line boxes to the multiple of the specified unit.</p>
<li data-md="">
<p>Adjust widths of block-level boxes to the multiple of the specified unit.</p>
</ul>
<p>By controlling heights of line boxes,
lines of text in different fonts can create consistent visuals
to help readability.</p>
<p>Also by stacking such line boxes,
authors can align lines across columns,
pages, scroll-snapped blocks, or multiple blocks placed absolutely,
to produce vertical rhythm.</p>
<div class="figure">
<a href="examples/snap-height.html"> <img src="images/snap-height-sample.png"></a>
<p class="caption">Vertical rhythm kept through pictures and different size of text in a multi-column document. </p>
</div>
<p>Controlling widths of block-level boxes to the multiple of the specified unit
gives the ability to control a block
so that it can fit mono-space characters
without remainders.
One of the use cases this feature addresses is
better readability of East Asian documents.
In Han ideographic-based scripts such as Chinese or Japanese,
most characters have 1em advance,
and due to that nature, most such documents are justified.</p>
<p>Adjusting widths of block-level boxes to the multiple of 1em helps to
minimize cases where justification needs to expand spacing.</p>
<h2 class="heading settled" data-level="2" id="line-height-step"><span class="secno">2. </span><span class="content">Adjusting Line Box Heights: the <a class="property" data-link-type="propdesc" href="#propdef-line-height-step" id="ref-for-propdef-line-height-step-1">line-height-step</a> property</span><a class="self-link" href="#line-height-step"></a></h2>
<table class="def propdef" data-link-for-hint="line-height-step">
<tbody>
<tr>
<th>Name:
<td><dfn class="dfn-paneled css" data-dfn-type="property" data-export="" data-lt="line-height-step" id="propdef-line-height-step">line-height-step<span class="dfn-panel" data-deco=""><b><a href="#propdef-line-height-step">#propdef-line-height-step</a></b><b>Referenced in:</b><span><a href="#ref-for-propdef-line-height-step-1">2. Adjusting Line Box Heights: the line-height-step property</a></span></span></dfn>
<tr class="value">
<th>Value:
<td class="prod"><a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#length-value" title="Expands to: em | advance measure | ch | vmin | cm | pc | pixel unit | in | rem | q | vh | ex | pt | vw | vmax | mm"><length></a> <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#integer-value"><integer></a><a data-link-type="grammar" href="https://drafts.csswg.org/css-values-3/#mult-opt">?</a>
<tr>
<th>Initial:
<td>0px
<tr>
<th>Applies to:
<td>block containers
<tr>
<th>Inherited:
<td>yes
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed value:
<td>the absolute length for length, others as specified
<tr>
<th>Animatable:
<td>no
</table>
<p>Values have the following meanings:</p>
<dl>
<dt><a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#length-value" title="Expands to: em | advance measure | ch | vmin | cm | pc | pixel unit | in | rem | q | vh | ex | pt | vw | vmax | mm"><length></a>
<dd> This value defines the <dfn class="dfn-paneled" data-dfn-for="line-height-step" data-dfn-type="dfn" data-lt="step unit" data-noexport="" id="line-height-step-step-unit">step unit<span class="dfn-panel" data-deco=""><b><a href="#line-height-step-step-unit">#line-height-step-step-unit</a></b><b>Referenced in:</b><span><a href="#ref-for-line-height-step-step-unit-1">2. Adjusting Line Box Heights: the line-height-step property</a></span><span><a href="#ref-for-line-height-step-step-unit-2">2.1. Stepping Line Box Heights</a> <a href="#ref-for-line-height-step-step-unit-3">(2)</a> <a href="#ref-for-line-height-step-step-unit-4">(3)</a> <a href="#ref-for-line-height-step-step-unit-5">(4)</a> <a href="#ref-for-line-height-step-step-unit-6">(5)</a> <a href="#ref-for-line-height-step-step-unit-7">(6)</a> <a href="#ref-for-line-height-step-step-unit-8">(7)</a> <a href="#ref-for-line-height-step-step-unit-9">(8)</a></span><span><a href="#ref-for-line-height-step-step-unit-10">2.2. Aligning Baselines</a> <a href="#ref-for-line-height-step-step-unit-11">(2)</a> <a href="#ref-for-line-height-step-step-unit-12">(3)</a> <a href="#ref-for-line-height-step-step-unit-13">(4)</a></span></span></dfn> for line box heights.
Non-negative <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#length-value" title="Expands to: em | advance measure | ch | vmin | cm | pc | pixel unit | in | rem | q | vh | ex | pt | vw | vmax | mm"><length></a>s are valid.
<dt><a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#integer-value"><integer></a>
<dd> This value defines the <dfn class="dfn-paneled" data-dfn-for="line-height-step" data-dfn-type="dfn" data-lt="step baseline position" data-noexport="" id="line-height-step-step-baseline-position">step baseline position<span class="dfn-panel" data-deco=""><b><a href="#line-height-step-step-baseline-position">#line-height-step-step-baseline-position</a></b><b>Referenced in:</b><span><a href="#ref-for-line-height-step-step-baseline-position-1">2.1. Stepping Line Box Heights</a></span><span><a href="#ref-for-line-height-step-step-baseline-position-2">2.2. Aligning Baselines</a> <a href="#ref-for-line-height-step-step-baseline-position-3">(2)</a> <a href="#ref-for-line-height-step-step-baseline-position-4">(3)</a> <a href="#ref-for-line-height-step-step-baseline-position-5">(4)</a> <a href="#ref-for-line-height-step-step-baseline-position-6">(5)</a> <a href="#ref-for-line-height-step-step-baseline-position-7">(6)</a> <a href="#ref-for-line-height-step-step-baseline-position-8">(7)</a> <a href="#ref-for-line-height-step-step-baseline-position-9">(8)</a></span></span></dfn> within the <a data-link-type="dfn" href="#line-height-step-step-unit" id="ref-for-line-height-step-step-unit-1">step unit</a>.
Values between 1 and 100 (inclusive) are valid.
</dl>
<p class="issue" id="issue-d3c63632"><a class="self-link" href="#issue-d3c63632"></a> Naming under discussion.</p>
<p class="issue" id="issue-1c78e071"><a class="self-link" href="#issue-1c78e071"></a> Should the step baseline position be percent?
Not much precision is needed, but
there was one feedback that percent is easier to use.</p>
<h3 class="heading settled" data-level="2.1" id="height"><span class="secno">2.1. </span><span class="content">Stepping Line Box Heights</span><a class="self-link" href="#height"></a></h3>
<p>When the <a data-link-type="dfn" href="#line-height-step-step-unit" id="ref-for-line-height-step-step-unit-2">step unit</a> is set to a positive <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#length-value" title="Expands to: em | advance measure | ch | vmin | cm | pc | pixel unit | in | rem | q | vh | ex | pt | vw | vmax | mm"><length></a>,
the line box heights are rounded <i>up</i> to
the multiple of the unit.</p>
<p><a data-link-type="biblio" href="#biblio-css21">[CSS21]</a> <a href="https://drafts.csswg.org/css2/visudet.html#line-height">§10.8 Line height calculations</a> defines how to compute the line box height
after the line box was constructed from inline-level boxes.
The rounding is applied to the computed line box height
by assuming that there is an inline-level box that has adjusted A' and D'
in the line box.</p>
<div class="figure">
<img src="images/adjust-line-height.svg">
<p class="caption">Rounding up the computed line box height. </p>
</div>
<p>The <a data-link-type="dfn" href="#line-height-step-step-baseline-position" id="ref-for-line-height-step-step-baseline-position-1">step baseline position</a> determines
how the additional spaces are distributed.</p>
<ul>
<li data-md="">
<p>When it is not set,
the height is rounded up to the closest multiple of the <a data-link-type="dfn" href="#line-height-step-step-unit" id="ref-for-line-height-step-step-unit-3">step unit</a>, and
the space is distributed to <a data-link-type="dfn" href="https://drafts.csswg.org/css-writing-modes-3/#over">over</a>-side (T) and <a data-link-type="dfn" href="https://drafts.csswg.org/css-writing-modes-3/#under">under</a>-side (B) equally,
so that the original line box appears at the center of the
multiple of <a data-link-type="dfn" href="#line-height-step-step-unit" id="ref-for-line-height-step-step-unit-4">step unit</a>.</p>
<li data-md="">
<p>When it is set,
refer to the <a href="#baseline">baseline</a> section below.</p>
</ul>
<div class="example" id="example-10c8dad9">
<a class="self-link" href="#example-10c8dad9"></a>
<div class="figure" style="float:right"> <img src="images/line-grid-center.svg" style="height: 300px"> </div>
<p>In the following example,
the height of line box in each paragraph is rounded up to the <a data-link-type="dfn" href="#line-height-step-step-unit" id="ref-for-line-height-step-step-unit-5">step unit</a>.</p>
<pre class="lang-css highlight"><span></span><span class="nt">:root </span><span class="p">{</span>
<span class="k">font-size</span><span class="p">:</span> <span class="m">12</span><span class="l">pt</span><span class="p">;</span>
<span class="k">--my-grid</span><span class="p">:</span> <span class="m">18</span><span class="l">pt</span><span class="p">;</span>
<span class="k">line-height-step</span><span class="p">:</span> <span class="nf">var</span><span class="p">(</span>--my-grid<span class="p">);</span>
<span class="p">}</span>
<span class="nt">h1 </span><span class="p">{</span>
<span class="k">font-size</span><span class="p">:</span> <span class="m">20</span><span class="l">pt</span><span class="p">;</span>
<span class="k">margin-top</span><span class="p">:</span> <span class="nf">calc</span><span class="p">(</span><span class="m">2</span> * var(--my-grid));
}
p {
margin: 0;
}</pre>
<p>The line box in <code><h1></code> does not fit into one <a data-link-type="dfn" href="#line-height-step-step-unit" id="ref-for-line-height-step-step-unit-6">step unit</a> and thus occupies two,
but it is still centered within the two <a data-link-type="dfn" href="#line-height-step-step-unit" id="ref-for-line-height-step-step-unit-7">step unit</a>.</p>
</div>
<div class="example" id="example-f68847c9">
<a class="self-link" href="#example-f68847c9"></a> Authors can keep margins or other properties to be multiple of <a data-link-type="dfn" href="#line-height-step-step-unit" id="ref-for-line-height-step-step-unit-8">step unit</a> using <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-variables-1/#funcdef-var">var()</a> and <a class="css" data-link-type="maybe" href="https://drafts.csswg.org/css-values-3/#funcdef-calc">calc()</a> as in the example above.
<p>If author prefers,
tools like Sass can make such declarations shorter.</p>
<pre class="lang-css highlight"><span></span><span class="nt">$gu: 18px;</span>
<span class="nt">@function gu($n) </span><span class="p">{</span>
<span class="n">@return</span> $n * $gu;
}
h1 {
font-size: 20pt;
margin: gu(1.2) auto gu(1.8);
}</pre>
</div>
<div class="note" role="note"> It is usually recommended to set the <a class="property" data-link-type="propdesc" href="https://drafts.csswg.org/css2/visudet.html#propdef-line-height">line-height</a> lower than
the <a data-link-type="dfn" href="#line-height-step-step-unit" id="ref-for-line-height-step-step-unit-9">step unit</a>.
The used line height can increase due to several factors such as
the use of <a class="property" data-link-type="propdesc" href="https://drafts.csswg.org/css2/visudet.html#propdef-vertical-align">vertical-align</a> or font fallback. </div>
<h3 class="heading settled" data-level="2.2" id="baseline"><span class="secno">2.2. </span><span class="content">Aligning Baselines</span><a class="self-link" href="#baseline"></a></h3>
<div class="figure" style="float:right"> <img src="images/line-grid-baseline.svg"> </div>
<p>When the <a data-link-type="dfn" href="#line-height-step-step-baseline-position" id="ref-for-line-height-step-step-baseline-position-2">step baseline position</a> is set,
the additional spaces are distributed using the following formula:</p>
<ul>
<li data-md="">
<p>space-over = P - T % U, add U if the result is negative</p>
<li data-md="">
<p>space-under = U - (space-over + T + B) % U</p>
</ul>
<p>Given:</p>
<ul>
<li data-md="">
<p>U: the <a data-link-type="dfn" href="#line-height-step-step-unit" id="ref-for-line-height-step-step-unit-10">step unit</a>.</p>
<li data-md="">
<p>P: the <a data-link-type="dfn" href="#line-height-step-step-baseline-position" id="ref-for-line-height-step-step-baseline-position-3">step baseline position</a> × U / 100.</p>
<li data-md="">
<p>T: the distance between the top of the line box and the baseline.</p>
<li data-md="">
<p>B: the distance between the bottom of the line box and the baseline.</p>
</ul>
<p>This formula pushes the baseline of the line box
down to the closest <a data-link-type="dfn" href="#line-height-step-step-baseline-position" id="ref-for-line-height-step-step-baseline-position-4">step baseline position</a>,
and the bottom to the next <a data-link-type="dfn" href="#line-height-step-step-unit" id="ref-for-line-height-step-step-unit-11">step unit</a>.</p>
<div class="example" id="example-8ee4d579">
<a class="self-link" href="#example-8ee4d579"></a>
<div class="figure" style="float:right"> <img src="images/line-grid-baseline-multicol.svg"> </div>
<p>The following CSS sets the <a data-link-type="dfn" href="#line-height-step-step-baseline-position" id="ref-for-line-height-step-step-baseline-position-5">step baseline position</a> to 14pt (20pt × 0.70) within each <a data-link-type="dfn" href="#line-height-step-step-unit" id="ref-for-line-height-step-step-unit-12">step unit</a>.</p>
<pre class="lang-css highlight"><span></span><span class="nt">:root </span><span class="p">{</span>
<span class="k">line-height-step</span><span class="p">:</span> <span class="m">20</span><span class="l">pt</span> <span class="m">7</span><span class="l">0</span><span class="p">;</span>
<span class="p">}</span></pre>
<p>The baseline of the line box is pushed down
to the closest <a data-link-type="dfn" href="#line-height-step-step-baseline-position" id="ref-for-line-height-step-step-baseline-position-6">step baseline position</a> by adding the space-over.</p>
<p><code><h1></code> is as tall as
its baseline being lower than the second <a data-link-type="dfn" href="#line-height-step-step-baseline-position" id="ref-for-line-height-step-step-baseline-position-7">step baseline position</a> that it is pushed down to the third <a data-link-type="dfn" href="#line-height-step-step-baseline-position" id="ref-for-line-height-step-step-baseline-position-8">step baseline position</a>.</p>
</div>
<div class="note" role="note"> Since the bottom of the line box is rounded to the closest <a data-link-type="dfn" href="#line-height-step-step-unit" id="ref-for-line-height-step-step-unit-13">step unit</a> next to the descenders of the line box,
large descenders may result in unintended spaces under the line box.
Oftentimes changing <a data-link-type="dfn" href="#line-height-step-step-baseline-position" id="ref-for-line-height-step-step-baseline-position-9">step baseline position</a> can control such situations. </div>
<h3 class="heading settled" data-level="2.3" id="block-height"><span class="secno">2.3. </span><span class="content">Notes on Block-level Boxes</span><a class="self-link" href="#block-height"></a></h3>
<p><i>This section is not normative.</i></p>
<p>This level of the specification does not provide features
to adjust heights of block-level boxes.</p>
<div class="example" id="example-a7e98509">
<a class="self-link" href="#example-a7e98509"></a> The following CSS turns <code><h2></code> to inline-blocks.
<pre class="lang-css highlight"><span></span><span class="nt">:root </span><span class="p">{</span>
<span class="k">line-height-step</span><span class="p">:</span> <span class="m">18</span><span class="l">pt</span><span class="p">;</span>
<span class="p">}</span>
<span class="nt">h2 </span><span class="p">{</span>
<span class="k">display</span><span class="p">:</span> inline-block<span class="p">;</span>
<span class="k">width</span><span class="p">:</span> <span class="m">10</span><span class="l">0</span>%;
line-height-step: 0;
line-height: 1.2;
}</pre>
<p>When an <code><h2></code> is long enough to wrap,
text inside the <code><h2></code> uses <a class="css" data-link-type="propdesc" href="https://drafts.csswg.org/css2/visudet.html#propdef-line-height">line-height: 1.2</a>, while
the height of the <code><h2></code> block is rounded up
to the multiple of <span class="css">18pt</span>.
See <a href="examples/line-height-step.html">a sample in action</a>.</p>
</div>
<h2 class="heading settled" data-level="3" id="width"><span class="secno">3. </span><span class="content">Stepping Widths: the <a class="property" data-link-type="propdesc" href="#propdef-inline-size-step" id="ref-for-propdef-inline-size-step-1">inline-size-step</a> property</span><a class="self-link" href="#width"></a></h2>
<table class="def propdef" data-link-for-hint="inline-size-step">
<tbody>
<tr>
<th>Name:
<td><dfn class="dfn-paneled css" data-dfn-type="property" data-export="" data-lt="inline-size-step" id="propdef-inline-size-step">inline-size-step<span class="dfn-panel" data-deco=""><b><a href="#propdef-inline-size-step">#propdef-inline-size-step</a></b><b>Referenced in:</b><span><a href="#ref-for-propdef-inline-size-step-1">3. Stepping Widths: the inline-size-step property</a></span></span></dfn>
<tr class="value">
<th>Value:
<td class="prod"><a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#length-value" title="Expands to: em | advance measure | ch | vmin | cm | pc | pixel unit | in | rem | q | vh | ex | pt | vw | vmax | mm"><length></a>
<tr>
<th>Initial:
<td>0px
<tr>
<th>Applies to:
<td>all elements but non-replaced inline elements, table rows, and row groups
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed value:
<td>the absolute length
<tr>
<th>Animatable:
<td>no
</table>
<p>Non-negative <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#length-value" title="Expands to: em | advance measure | ch | vmin | cm | pc | pixel unit | in | rem | q | vh | ex | pt | vw | vmax | mm"><length></a>s are valid.</p>
<p>When this property is set to a positive <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#length-value" title="Expands to: em | advance measure | ch | vmin | cm | pc | pixel unit | in | rem | q | vh | ex | pt | vw | vmax | mm"><length></a> and the <a data-link-type="dfn" href="https://drafts.csswg.org/css-sizing-4/#available">available inline size</a> is <a data-link-type="dfn" href="https://drafts.csswg.org/css-sizing-4/#definite">definite</a>,
the <a data-link-type="dfn" href="https://drafts.csswg.org/css-sizing-4/#available">available inline size</a> of the element is rounded <em>down</em> to the closest multiple of the specified <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#length-value" title="Expands to: em | advance measure | ch | vmin | cm | pc | pixel unit | in | rem | q | vh | ex | pt | vw | vmax | mm"><length></a> before it is used.</p>
<div class="note" role="note"> Since this property only adjusts <a data-link-type="dfn" href="https://drafts.csswg.org/css-sizing-4/#available">available inline size</a>,
it does not guarantee that the <a data-link-type="dfn" href="https://drafts.csswg.org/css-writing-modes-3/#inline-size">inline size</a> of child boxes
are the multiple of the specified <a class="production css" data-link-type="type" href="https://drafts.csswg.org/css-values-3/#length-value" title="Expands to: em | advance measure | ch | vmin | cm | pc | pixel unit | in | rem | q | vh | ex | pt | vw | vmax | mm"><length></a> if there were other constraints. </div>
<p>When this property is applied to a multi-column element,
the <a data-link-type="dfn" href="https://drafts.csswg.org/css-sizing-4/#available">available inline size</a> of the content box is not rounded but
the <a data-link-type="dfn" href="https://drafts.csswg.org/css-sizing-4/#available">available inline size</a> of the <a data-link-type="dfn">column box</a> is rounded.</p>
<div class="note" role="note">
When using this property with CSS layout features such as tables or flexbox,
authors are expected to apply this property to
item boxes rather than container boxes;
e.g., table cells rather than tables, or
flex-items rather than flex-containers.
<p>However, the special case above is needed because
authors cannot style <a data-link-type="dfn">column boxes</a>.</p>
</div>
<div class="example" id="example-419f908b">
<a class="self-link" href="#example-419f908b"></a> This property improves the justification
for Han ideograph-based scripts such as Chinese or Japanese.
<p>With the following CSS,
the <code><article></code> elements
and blocks with <code>bodytext</code> class
are justified,
but the expansion occurs
only when there are non-CJK characters in the line
because their logical widths are
adjusted to the multiple of 1em.</p>
<pre class="lang-css highlight"><span></span><span class="nt">article, .bodytext </span><span class="p">{</span>
<span class="k">font-size</span><span class="p">:</span> <span class="m">12</span><span class="l">pt</span><span class="p">;</span>
<span class="k">text-align</span><span class="p">:</span> justify<span class="p">;</span>
<span class="k">inline-size-step</span><span class="p">:</span> <span class="m">1</span><span class="l">em</span><span class="p">;</span>
<span class="p">}</span></pre>
</div>
<h2 class="heading settled" data-level="4" id="priv-sec"><span class="secno">4. </span><span class="content">Privacy and Security Considerations</span><a class="self-link" href="#priv-sec"></a></h2>
<p>This specification introduces no new privacy leaks,
or security considerations beyond "implement it correctly".</p>
<h2 class="heading settled" data-level="5" id="acks"><span class="secno">5. </span><span class="content">Acknowledgments</span><a class="self-link" href="#acks"></a></h2>
This specification would not have been possible without the help from:
Takao Baba,
Chris Eppstein,
Shinyu Murakami,
Tsutomu Nanjo,
Charlie Neely,
Florian Rivoal,
Hiroshi Sakakibara,
Alan Stearns,
and the CSS Working Group members.
</main>
<h2 class="no-ref no-num heading settled" id="conformance"><span class="content"> Conformance</span><a class="self-link" href="#conformance"></a></h2>
<h3 class="heading settled" id="document-conventions"><span class="content"> Document conventions</span><a class="self-link" href="#document-conventions"></a></h3>
<p>Conformance requirements are expressed with a combination of
descriptive assertions and RFC 2119 terminology. The key words “MUST”,
“MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”,
“RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this
document are to be interpreted as described in RFC 2119.
However, for readability, these words do not appear in all uppercase
letters in this specification. </p>
<p>All of the text of this specification is normative except sections
explicitly marked as non-normative, examples, and notes. <a data-link-type="biblio" href="#biblio-rfc2119">[RFC2119]</a> </p>
<p>Examples in this specification are introduced with the words “for example”
or are set apart from the normative text with <code>class="example"</code>,
like this: </p>
<div class="example" id="example-52448c84">
<a class="self-link" href="#example-52448c84"></a>
<p>This is an example of an informative example. </p>
</div>
<p>Informative notes begin with the word “Note” and are set apart from the
normative text with <code>class="note"</code>, like this: </p>
<p class="note" role="note">Note, this is an informative note. </p>
<p>Advisements are normative sections styled to evoke special attention and are
set apart from other normative text with <code><strong class="advisement"></code>, like
this: <strong class="advisement"> UAs MUST provide an accessible alternative. </strong> </p>
<h3 class="heading settled" id="conform-classes"><span class="content"> Conformance classes</span><a class="self-link" href="#conform-classes"></a></h3>
<p>Conformance to this specification
is defined for three conformance classes: </p>
<dl>
<dt>style sheet
<dd>A <a href="http://www.w3.org/TR/CSS2/conform.html#style-sheet">CSS
style sheet</a>.
<dt>renderer
<dd>A <a href="http://www.w3.org/TR/CSS2/conform.html#user-agent">UA</a> that interprets the semantics of a style sheet and renders
documents that use them.
<dt>authoring tool
<dd>A <a href="http://www.w3.org/TR/CSS2/conform.html#user-agent">UA</a> that writes a style sheet.
</dl>
<p>A style sheet is conformant to this specification
if all of its statements that use syntax defined in this module are valid
according to the generic CSS grammar and the individual grammars of each
feature defined in this module. </p>
<p>A renderer is conformant to this specification
if, in addition to interpreting the style sheet as defined by the
appropriate specifications, it supports all the features defined
by this specification by parsing them correctly
and rendering the document accordingly. However, the inability of a
UA to correctly render a document due to limitations of the device
does not make the UA non-conformant. (For example, a UA is not
required to render color on a monochrome monitor.) </p>
<p>An authoring tool is conformant to this specification
if it writes style sheets that are syntactically correct according to the
generic CSS grammar and the individual grammars of each feature in
this module, and meet all other conformance requirements of style sheets
as described in this module. </p>
<h3 class="heading settled" id="conform-responsible"><span class="content"> Requirements for Responsible Implementation of CSS</span><a class="self-link" href="#conform-responsible"></a></h3>
<p>The following sections define several conformance requirements
for implementing CSS responsibly,
in a way that promotes interoperability in the present and future. </p>
<h4 class="heading settled" id="conform-partial"><span class="content"> Partial Implementations</span><a class="self-link" href="#conform-partial"></a></h4>
<p>So that authors can exploit the forward-compatible parsing rules to assign fallback values, <strong>CSS renderers <em>must</em> treat as invalid
(and <a href="http://www.w3.org/TR/CSS2/conform.html#ignore">ignore as appropriate</a>)
any at-rules, properties, property values, keywords, and other syntactic constructs
for which they have no usable level of support</strong>.
In particular, user agents <em>must not</em> selectively ignore
unsupported property values and honor supported values in a single multi-value property declaration:
if any value is considered invalid (as unsupported values must be),
CSS requires that the entire declaration be ignored. </p>
<h4 class="heading settled" id="conform-future-proofing"><span class="content"> Implementations of Unstable and Proprietary Features</span><a class="self-link" href="#conform-future-proofing"></a></h4>
<p>To avoid clashes with future stable CSS features,
the CSSWG recommends <a href="http://www.w3.org/TR/CSS/#future-proofing">following best practices</a> for the implementation of <a href="http://www.w3.org/TR/CSS/#unstable">unstable</a> features and <a href="http://www.w3.org/TR/CSS/#proprietary-extension">proprietary extensions</a> to CSS. </p>
<h4 class="heading settled" id="conform-testing"><span class="content"> Implementations of CR-level Features</span><a class="self-link" href="#conform-testing"></a></h4>
<p>Once a specification reaches the Candidate Recommendation stage,
implementers should release an <a data-link-type="dfn" href="http://www.w3.org/TR/CSS/#vendor-prefix">unprefixed</a> implementation
of any CR-level feature they can demonstrate
to be correctly implemented according to spec,
and should avoid exposing a prefixed variant of that feature. </p>
<p>To establish and maintain the interoperability of CSS across
implementations, the CSS Working Group requests that non-experimental
CSS renderers submit an implementation report (and, if necessary, the
testcases used for that implementation report) to the W3C before
releasing an unprefixed implementation of any CSS features. Testcases
submitted to W3C are subject to review and correction by the CSS
Working Group. </p>
<p>
Further information on submitting testcases and implementation reports
can be found from on the CSS Working Group’s website at <a href="http://www.w3.org/Style/CSS/Test/">http://www.w3.org/Style/CSS/Test/</a>.
Questions should be directed to the <a href="http://lists.w3.org/Archives/Public/public-css-testsuite">public-css-testsuite@w3.org</a> mailing list.
<script src="https://www.w3.org/scripts/TR/2016/fixup.js"></script>
</p>
<h2 class="no-num no-ref heading settled" id="index"><span class="content">Index</span><a class="self-link" href="#index"></a></h2>
<h3 class="no-num no-ref heading settled" id="index-defined-here"><span class="content">Terms defined by this specification</span><a class="self-link" href="#index-defined-here"></a></h3>
<ul class="index">
<li><a href="#propdef-inline-size-step">inline-size-step</a><span>, in §3</span>
<li><a href="#propdef-line-height-step">line-height-step</a><span>, in §2</span>
<li><a href="#line-height-step-step-baseline-position">step baseline position</a><span>, in §2</span>
<li><a href="#line-height-step-step-unit">step unit</a><span>, in §2</span>
</ul>
<h3 class="no-num no-ref heading settled" id="index-defined-elsewhere"><span class="content">Terms defined by reference</span><a class="self-link" href="#index-defined-elsewhere"></a></h3>
<ul class="index">
<li>
<a data-link-type="biblio">[css-sizing-4]</a> defines the following terms:
<ul>
<li><a href="https://drafts.csswg.org/css-sizing-4/#available">available inline size</a>
<li><a href="https://drafts.csswg.org/css-sizing-4/#definite">definite</a>
</ul>
<li>
<a data-link-type="biblio">[css-values]</a> defines the following terms:
<ul>
<li><a href="https://drafts.csswg.org/css-values-3/#integer-value"><integer></a>
<li><a href="https://drafts.csswg.org/css-values-3/#length-value"><length></a>
<li><a href="https://drafts.csswg.org/css-values-3/#mult-opt">?</a>
<li><a href="https://drafts.csswg.org/css-values-3/#funcdef-calc">calc()</a>
</ul>
<li>
<a data-link-type="biblio">[css-variables-1]</a> defines the following terms:
<ul>
<li><a href="https://drafts.csswg.org/css-variables-1/#funcdef-var">var()</a>
</ul>
<li>
<a data-link-type="biblio">[css-writing-modes-3]</a> defines the following terms:
<ul>
<li><a href="https://drafts.csswg.org/css-writing-modes-3/#inline-size">inline size</a>
<li><a href="https://drafts.csswg.org/css-writing-modes-3/#over">over</a>
<li><a href="https://drafts.csswg.org/css-writing-modes-3/#under">under</a>
</ul>
<li>
<a data-link-type="biblio">[CSS21]</a> defines the following terms:
<ul>
<li><a href="https://drafts.csswg.org/css2/visudet.html#propdef-line-height">line-height</a>
<li><a href="https://drafts.csswg.org/css2/visudet.html#propdef-vertical-align">vertical-align</a>
</ul>
</ul>
<h2 class="no-num no-ref heading settled" id="references"><span class="content">References</span><a class="self-link" href="#references"></a></h2>
<h3 class="no-num no-ref heading settled" id="normative"><span class="content">Normative References</span><a class="self-link" href="#normative"></a></h3>
<dl>
<dt id="biblio-css-sizing-4">[CSS-SIZING-4]
<dd>CSS Intrinsic & Extrinsic Sizing Module Level 4 URL: <a href="https://drafts.csswg.org/css-sizing-4/">https://drafts.csswg.org/css-sizing-4/</a>
<dt id="biblio-css-values">[CSS-VALUES]
<dd>Tab Atkins Jr.; Elika Etemad. <a href="http://dev.w3.org/csswg/css-values/">CSS Values and Units Module Level 3</a>. 11 June 2015. CR. URL: <a href="http://dev.w3.org/csswg/css-values/">http://dev.w3.org/csswg/css-values/</a>
<dt id="biblio-css-writing-modes-3">[CSS-WRITING-MODES-3]
<dd>Elika Etemad; Koji Ishii. <a href="http://dev.w3.org/csswg/css-writing-modes-3/">CSS Writing Modes Level 3</a>. 15 December 2015. CR. URL: <a href="http://dev.w3.org/csswg/css-writing-modes-3/">http://dev.w3.org/csswg/css-writing-modes-3/</a>
<dt id="biblio-css21">[CSS21]
<dd>Bert Bos; et al. <a href="http://www.w3.org/TR/CSS2">Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification</a>. 7 June 2011. REC. URL: <a href="http://www.w3.org/TR/CSS2">http://www.w3.org/TR/CSS2</a>
<dt id="biblio-rfc2119">[RFC2119]
<dd>S. Bradner. <a href="https://tools.ietf.org/html/rfc2119">Key words for use in RFCs to Indicate Requirement Levels</a>. March 1997. Best Current Practice. URL: <a href="https://tools.ietf.org/html/rfc2119">https://tools.ietf.org/html/rfc2119</a>
</dl>
<h3 class="no-num no-ref heading settled" id="informative"><span class="content">Informative References</span><a class="self-link" href="#informative"></a></h3>
<dl>
<dt id="biblio-css-variables-1">[CSS-VARIABLES-1]
<dd>Tab Atkins Jr.. <a href="http://dev.w3.org/csswg/css-variables/">CSS Custom Properties for Cascading Variables Module Level 1</a>. 3 December 2015. CR. URL: <a href="http://dev.w3.org/csswg/css-variables/">http://dev.w3.org/csswg/css-variables/</a>
</dl>
<h2 class="no-num no-ref heading settled" id="property-index"><span class="content">Property Index</span><a class="self-link" href="#property-index"></a></h2>
<div class="big-element-wrapper">
<table class="index">
<thead>
<tr>
<th scope="col">Name
<th scope="col">Value
<th scope="col">Initial
<th scope="col">Applies to
<th scope="col">Inh.
<th scope="col">%ages
<th scope="col">Media
<th scope="col">Animatable
<th scope="col">Computed value
<tbody>
<tr>
<th scope="row"><a class="css" data-link-type="property" href="#propdef-line-height-step">line-height-step</a>
<td><length> <integer>?
<td>0px
<td>block containers
<td>yes
<td>N/A
<td>visual
<td>no
<td>the absolute length for length, others as specified
<tr>
<th scope="row"><a class="css" data-link-type="property" href="#propdef-inline-size-step">inline-size-step</a>
<td><length>
<td>0px
<td>all elements but non-replaced inline elements, table rows, and row groups
<td>no
<td>N/A
<td>visual
<td>no
<td>the absolute length
</table>
</div>
<h2 class="no-num no-ref heading settled" id="issues-index"><span class="content">Issues Index</span><a class="self-link" href="#issues-index"></a></h2>
<div style="counter-reset:issue">
<div class="issue"> Naming under discussion.<a href="#issue-d3c63632"> ↵ </a></div>
<div class="issue"> Should the step baseline position be percent?
Not much precision is needed, but
there was one feedback that percent is easier to use.<a href="#issue-1c78e071"> ↵ </a></div>
</div>
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