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<!DOCTYPE html><html lang=en><head>
<meta content="text/html; charset=utf-8" http-equiv=Content-Type>
<title>CSS Counter Styles Level 3</title>
<link href=../default.css rel=stylesheet type=text/css>
<link href=../csslogo.ico rel="shortcut icon" type=image/x-icon>
<link href=https://www.w3.org/StyleSheets/TR/W3C-ED rel=stylesheet type=text/css>
</head>
<body class=h-entry>
<style scoped>
pre.stylesheet { white-space: pre-wrap; }
</style>
<div class=head>
<p data-fill-with=logo><a class=logo href=http://www.w3.org/>
<img alt=W3C height=48 src=http://www.w3.org/Icons/w3c_home width=72>
</a></p>
<h1 class="p-name no-ref" id=title>CSS Counter Styles Level 3</h1>
<h2 class="no-num no-toc no-ref" id=subtitle><span class=content>Editor's Draft,
<span class=dt-updated><span class=value-title title=20130806>6 August 2013</span></span></span></h2>
<div data-fill-with=spec-metadata><dl><dt>This version:<dd><a class=u-url href=http://dev.w3.org/csswg/css-counter-styles/>http://dev.w3.org/csswg/css-counter-styles/</a><dt>Latest version:<dd><a href=http://w3.org/TR/css-counter-styles-3/>http://w3.org/TR/css-counter-styles-3/</a><dt>Editor's Draft:<dd><a href=http://dev.w3.org/csswg/css-counter-styles/>http://dev.w3.org/csswg/css-counter-styles/</a><dt>Previous Versions:<dd><a href=http://www.w3.org/TR/2012/WD-css-counter-styles-3-20121009/ rel=previous>http://www.w3.org/TR/2012/WD-css-counter-styles-3-20121009/</a>
<dt>Feedback:</dt>
<dd><a href="mailto:www-style@w3.org?subject=%5Bcss-counter-styles%5D%20feedback">www-style@w3.org</a>
with subject line
“<kbd>[css-counter-styles] <var>… message topic …</var></kbd>”
(<a href=http://lists.w3.org/Archives/Public/www-style/ rel=discussion>archives</a>)<dt>Test Suite:<dd>None Yet<dt>Editors:
<dd class="p-author h-card vcard"><a class="p-name fn u-url url" href=http://xanthir.com/contact/>Tab Atkins Jr.</a> (<span class="p-org org">Google</span>)<dt>Issue Tracking:<dd><a href="https://www.w3.org/Bugs/Public/buglist.cgi?product=CSS&component=Counter%20Styles&resolution=---">Bugzilla</a></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> © 2013 <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>), All Rights Reserved. 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" id=abstract><span class=content>Abstract</span></h2>
<p class=p-summary data-fill-with=abstract>This module introduces the <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule, which allows authors to define their own custom counter styles for use with CSS list-marker and generated-content counters <a data-biblio-type=informative data-link-type=biblio href=#css3list title=CSS3LIST>[CSS3LIST]</a>. It also predefines a set of common counter styles, including the ones present in CSS2 and CSS2.1.
<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.</p>
<h2 class="no-num no-toc no-ref" 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>
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-counter-styles%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-counter-styles” in the subject,
preferably like this:
“[css-counter-styles] <em>…summary of comment…</em>”
<p>
This document was produced by the <a href=/Style/CSS/members>CSS Working Group</a>
(part of the <a href=/Style/>Style Activity</a>).
<p>
This document was produced by a group operating under
the <a href=/Consortium/Patent-Policy-20040205/>5 February 2004 W3C Patent Policy</a>.
W3C maintains a <a href=/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=/Consortium/Patent-Policy-20040205/#def-essential>Essential Claim(s)</a>
must disclose the information in accordance with <a href=/Consortium/Patent-Policy-20040205/#sec-Disclosure>section 6 of the W3C Patent Policy</a>.</div>
<div data-fill-with=at-risk><p>The following features are at-risk, and may be dropped during the CR period:
<ul><li>the counter styles <a class=css data-link-type=maybe href=#valuedef-cjk-decimal>cjk-decimal</a>, <a class=css data-link-type=maybe href=#valuedef-hebrew>hebrew</a>, <a class=css data-link-type=maybe href=#valuedef-hiragana>hiragana</a>, <a class=css data-link-type=maybe href=#valuedef-hiragana-iroha>hiragana-iroha</a>, <a class=css data-link-type=maybe href=#valuedef-katakana>katakana</a>, <a class=css data-link-type=maybe href=#valuedef-katakana-iroha>katakana-iroha</a>, <a class=css data-link-type=maybe href=#valuedef-japanese-informal>japanese-informal</a>, <a class=css data-link-type=maybe href=#valuedef-japanese-formal>japanese-formal</a>, <a class=css data-link-type=maybe href=#valuedef-korean-hangul-formal>korean-hangul-formal</a>, <a class=css data-link-type=maybe href=#valuedef-korean-hanja-informal>korean-hanja-informal</a>, <a class=css data-link-type=maybe href=#valuedef-korean-hanja-formal>korean-hanja-formal</a>, <a class=css data-link-type=maybe href=#valuedef-simp-chinese-informal>simp-chinese-informal</a>, <a class=css data-link-type=maybe href=#valuedef-simp-chinese-formal>simp-chinese-formal</a>, <a class=css data-link-type=maybe href=#valuedef-trad-chinese-informal>trad-chinese-informal</a>, <a class=css data-link-type=maybe href=#valuedef-trad-chinese-formal>trad-chinese-formal</a>, and <a class=css data-link-type=maybe href=#valuedef-ethiopic-numeric>ethiopic-numeric</a>.</ul></div>
<h2 class="no-num no-toc no-ref" id=contents><span class=content>Table of contents</span></h2>
<div data-fill-with=table-of-contents><ul class=toc><li><a href=#intro><span class=secno>1</span>
Introduction</a><li><a href=#counter-styles><span class=secno>2</span>
Counter Styles</a><li><a href=#the-counter-style-rule><span class=secno>3</span>
Defining Custom Counter Styles: the <span class=css data-link-type=maybe>@counter-style</span> rule</a><ul class=toc><li><a href=#counter-style-system><span class=secno>3.1</span>
Counter algorithms: the <span class=property data-link-type=propdesc title=system>system</span> descriptor</a><ul class=toc><li><a href=#cyclic-system><span class=secno>3.1.1</span>
Cycling Symbols: the <span class=css data-link-type=maybe>cyclic</span> system</a><li><a href=#fixed-system><span class=secno>3.1.2</span>
Exhaustible Symbols: the <span class=css data-link-type=maybe>fixed</span> system</a><li><a href=#symbolic-system><span class=secno>3.1.3</span>
Repeating Symbols: the <span class=css data-link-type=maybe>symbolic</span> system</a><li><a href=#alphabetic-system><span class=secno>3.1.4</span>
Bijective Numerals: the <span data-link-for=system data-link-type=value>alphabetic</span> system</a><li><a href=#numeric-system><span class=secno>3.1.5</span>
Positional Numerals: the <span data-link-for=system data-link-type=value>numeric</span> system</a><li><a href=#additive-system><span class=secno>3.1.6</span>
Accumulating Numerals: the <span class=css data-link-type=maybe>additive</span> system</a><li><a href=#override-system><span class=secno>3.1.7</span>
Tweaking Existing Counter Styles: the <span class=css data-link-type=maybe>override</span> system</a></ul><li><a href=#counter-style-negative><span class=secno>3.2</span>
Formatting negative values: the <span class=property data-link-type=propdesc title=negative>negative</span> descriptor</a><li><a href=#counter-style-prefix><span class=secno>3.3</span>
Symbols before the marker: the <span class=property data-link-type=propdesc title=prefix>prefix</span> descriptor</a><li><a href=#counter-style-suffix><span class=secno>3.4</span>
Symbols after the marker: the <span class=property data-link-type=propdesc title=suffix>suffix</span> descriptor</a><li><a href=#counter-style-range><span class=secno>3.5</span>
Limiting the counter scope: the <span class=property data-link-type=propdesc title=range>range</span> descriptor</a><li><a href=#counter-style-pad><span class=secno>3.6</span>
Zero-Padding and Constant-Width Representations: the <span class=property data-link-type=propdesc title=pad>pad</span> descriptor</a><li><a href=#counter-style-fallback><span class=secno>3.7</span>
Defining fallback: the <span class=property data-link-type=propdesc title=fallback>fallback</span> descriptor</a><li><a href=#counter-style-symbols><span class=secno>3.8</span>
Marker characters: the <span class=property data-link-type=propdesc title=symbols>symbols</span> and <span class=property data-link-type=propdesc title=additive-symbols>additive-symbols</span> descriptors</a><li><a href=#counter-style-speak-as><span class=secno>3.9</span>
Speech Synthesis: the <span class=property data-link-type=propdesc title=speak-as>speak-as</span> descriptor</a></ul><li><a href=#symbols-function><span class=secno>4</span>
Defining Anonymous Counter Styles: the <span class=css data-link-type=maybe>symbols()</span> function</a><li><a href=#extending-css2><span class=secno>5</span>
Extending <span class=property data-link-type=propdesc title=list-style-type>list-style-type</span>, <span class=css data-link-type=maybe>counter()</span>, and <span class=css data-link-type=maybe>counters()</span></a><li><a href=#predefined-counters><span class=secno>6</span>
Simple Predefined Counter Styles</a><ul class=toc><li><a href=#simple-numeric><span class=secno>6.1</span>
Numeric: <span class=css data-link-type=maybe>decimal</span>, <span class=css data-link-type=maybe>decimal-leading-zero</span>, <span class=css data-link-type=maybe>cjk-decimal</span>, <span class=css data-link-type=maybe>lower-roman</span>, <span class=css data-link-type=maybe>upper-roman</span>, <span class=css data-link-type=maybe>armenian</span>, <span class=css data-link-type=maybe>georgian</span>, <span class=css data-link-type=maybe>hebrew</span></a><li><a href=#simple-alphabetic><span class=secno>6.2</span>
Alphabetic: <span class=css data-link-type=maybe>lower-alpha</span>, <span class=css data-link-type=maybe>lower-latin</span>, <span class=css data-link-type=maybe>upper-alpha</span>, <span class=css data-link-type=maybe>upper-latin</span>, <span class=css data-link-type=maybe>lower-greek</span>, <span class=css data-link-type=maybe>hiragana</span>, <span class=css data-link-type=maybe>hiragana-iroha</span>, <span class=css data-link-type=maybe>katakana</span>, <span class=css data-link-type=maybe>katakana-iroha</span></a><li><a href=#simple-symbolic><span class=secno>6.3</span>
Symbolic: <span class=css data-link-type=maybe>disc</span>, <span class=css data-link-type=maybe>circle</span>, <span class=css data-link-type=maybe>square</span>, <span class=css data-link-type=maybe>disclosure-open</span>, <span class=css data-link-type=maybe>disclosure-closed</span></a></ul><li><a href=#complex-predefined-counters><span class=secno>7</span>
Complex Predefined Counter Styles</a><ul class=toc><li><a href=#complex-cjk><span class=secno>7.1</span>
Longhand East Asian Counter Styles: <span class=css data-link-type=maybe>japanese-informal</span>, <span class=css data-link-type=maybe>japanese-formal</span>, <span class=css data-link-type=maybe>korean-hangul-formal</span>, <span class=css data-link-type=maybe>korean-hanja-informal</span>, <span class=css data-link-type=maybe>korean-hanja-formal</span>, <span class=css data-link-type=maybe>simp-chinese-informal</span>, <span class=css data-link-type=maybe>simp-chinese-formal</span>, <span class=css data-link-type=maybe>trad-chinese-informal</span>, <span class=css data-link-type=maybe>trad-chinese-formal</span></a><ul class=toc><li><a href=#limited-cjk><span class=secno>7.1.1</span>
Limited-range Implementation (required)</a><li><a href=#extended-cjk><span class=secno>7.1.2</span>
Extended Implementation (optional)</a></ul><li><a href=#ethiopic-numeric-counter-style><span class=secno>7.2</span>
Ethiopic Numeric Counter Style: <span class=css data-link-type=maybe>ethiopic-numeric</span></a></ul><li><a href=#additional-predefined><span class=secno>8</span>
Additional Predefined Counter Styles</a><li><a href=#apis><span class=secno>9</span>APIs</a><ul class=toc><li><a href=#extentions-to-cssrule-interface><span class=secno>9.1</span>
Extensions to the <code>CSSRule</code> interface</a><li><a href=#the-csscounterstylerule-interface><span class=secno>9.2</span>
The <code>CSSCounterStyleRule</code> interface</a></ul><li><a href=#ua-stylesheet><span class=secno>10</span>
Sample style sheet for HTML</a><li><a href=#changes><span class=secno></span>
Changes since the Oct 2012 Working Draft</a><li><a href=#acknowledgments><span class=secno></span>
Acknowledgments</a><li><a href=#conformance><span class=secno></span>
Conformance</a><ul class=toc><li><a href=#conventions><span class=secno></span>
Document conventions</a><li><a href=#conformance-classes><span class=secno></span>
Conformance classes</a><li><a href=#partial><span class=secno></span>
Partial implementations</a><li><a href=#experimental><span class=secno></span>
Experimental implementations</a><li><a href=#testing><span class=secno></span>
Non-experimental implementations</a></ul><li><a href=#references><span class=secno></span>
References</a><ul class=toc><li><a href=#normative><span class=secno></span>
Normative References</a><li><a href=#informative><span class=secno></span>
Informative References</a></ul><li><a href=#index><span class=secno></span>
Index</a><li><a href=#property-index><span class=secno></span>
Property index</a><ul class=toc><li><a href=#counter-style-descriptors><span class=secno></span>@counter-style Descriptors</a></ul></ul></div>
<h2 data-level=1 id=intro><span class=secno>1 </span><span class=content>
Introduction</span><a class=section-link href=#intro>§</a></h2>
<p> CSS 1 defined a handful of useful counter styles based on the styles that HTML traditionally allowed on ordered and unordered lists.
While this was expanded slightly by CSS2.1,
it doesn't address the needs of worldwide typography.
<p> This module introduces the <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule which allows CSS to address this in an open-ended manner,
by allowing the author to define their own counter styles.
These styles can then be used in the <a class=property data-link-type=propdesc href=http://dev.w3.org/csswg/css-lists-3/#list-style-type title=list-style-type>list-style-type</a> property
or in the <span class=css data-link-type=maybe>counter()</span> and <span class=css data-link-type=maybe>counters()</span> functions.
It also defines some additional predefined counter styles,
particularly ones which are common but complicated to represent with <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a>.
<h2 data-level=2 id=counter-styles><span class=secno>2 </span><span class=content>
Counter Styles</span><a class=section-link href=#counter-styles>§</a></h2>
<p> A <dfn data-dfn-type=dfn export="" id=counter-style>counter style</dfn> defines how to convert a counter value into a string.
Counter styles are composed of:
<p> <ul>
<li>
a name,
to identify the style
<li>
an algorithm,
which transforms integer counter values into a basic string representation
<li>
a negative sign,
which is prepended or appended to the representation of a negative counter value.
<li>
a prefix,
to prepend to the representation
<li>
a suffix
to append to the representation
<li>
a range,
which limits the values that a counter style handles
<li>
a spoken form,
which describes how to read out the counter style in a speech synthesizer
<li>
and a fallback style,
to render the representation with when the counter value is outside the counter style's range
or the counter style otherwise can't render the counter value
</ul>
<p> When asked to <dfn data-dfn-type=dfn export="" id=generate-a-counter-representation title="generate a counter|generate a counter representation">generate a counter representation</dfn>
using a particular counter style for a particular counter value,
follow these steps:
<ol>
<li>
If the counter value is outside the <a class=property data-link-type=propdesc href=#descdef-range title=range>range</a> of the counter style,
exit this algorithm and instead <a href=#generate-a-counter-representation>generate a counter representation</a>
using the counter style's fallback style and the same counter value.
<li>
Using the counter value and the counter algorithm for the counter style,
generate an initial representation for the counter value.
If the counter value is negative
and the counter style is <a href=#negative-capable>negative-capable</a>,
instead generate an initial representation using the absolute value of the counter value.
<li>
If the representation uses less symbols than specified in the counter style's <a class=property data-link-type=propdesc href=#descdef-pad title=pad>pad</a> descriptor,
prepend symbols to the representation as specified in the <a class=property data-link-type=propdesc href=#descdef-pad title=pad>pad</a> descriptor.
<li>
If the counter value is negative
and the counter style is <a href=#negative-capable>negative-capable</a>,
wrap the representation in the counter style's negative sign
as specified in the <a class=property data-link-type=propdesc href=#descdef-negative title=negative>negative</a> descriptor.
<li>
Return the representation.
</ol>
<p class=note> Note: the prefix and suffix don't play a part in this algorithm.
This is intentional;
the prefix and suffix aren't part of the string returned by the counter() or counters() functions.
Instead, the prefix and suffix are added by the algorithm that constructs the value of the <a data-link-spec=css-ui-3 data-link-type=property href=http://dev.w3.org/csswg/css-ui-3/#content>content</a> property for the <span class=css data-link-type=maybe>::marker</span> pseudo-element.
This also implies that the prefix and suffix always come from the specified counter-style,
even if the actual representation is constructed by a fallback style.
<h2 data-level=3 id=the-counter-style-rule><span class=secno>3 </span><span class=content>
Defining Custom Counter Styles: the <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule</span><a class=section-link href=#the-counter-style-rule>§</a></h2>
<p> The <dfn data-dfn-type=at-rule id=at-ruledef-counter-style>@counter-style</dfn> rule allows authors to define a custom <a href=#counter-style>counter style</a>.
The components of a <a href=#counter-style>counter style</a> are specified by descriptors in the <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule.
The algorithm is specified implicitly by a combination of the <span class=css data-link-type=maybe>system</span>, <span class=css data-link-type=maybe>symbols</span>, and <span class=css data-link-type=maybe>additive-symbols</span> properties.
<p> The general form of an <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule is:
<pre>@counter-style <a class=production data-link-type=type href=#typedef-counter-style-name><var><counter-style-name></var></a> { <a class=production data-link-type=type href=http://dev.w3.org/csswg/css-syntax-3/#declaration-list><var><declaration-list></var></a> }</pre>
<p> The <dfn data-dfn-type=type id=typedef-counter-style-name><counter-style-name></dfn> must be be a valid identifier
and must not be <a class=css data-link-type=maybe href=#valuedef-decimal>decimal</a> or <span class=css data-link-type=maybe>none</span>,
or else the rule is invalid.
(Note, however, that some names, like <span class=css data-link-type=maybe>inside</span> or <span class=css data-link-type=maybe>initial</span>,
might conflict with the existing values of properties like <a class=property data-link-type=propdesc href=http://dev.w3.org/csswg/css-lists-3/#list-style title=list-style>list-style</a>,
and thus won't be usable there.)
<p> Counter style names are case-sensitive.
However, the names defined in this specification are ASCII lower-cased on parse
wherever they are used as counter styles, e.g.
in the <a class=property data-link-type=propdesc href=http://dev.w3.org/csswg/css-lists-3/#list-style title=list-style>list-style</a> set of properties,
in the <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule,
and in the <span class=css data-link-type=maybe>counter()</span> functions.
<p> Each <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule specifies a value for every counter-style descriptor,
either implicitly or explicitly.
Those not given explicit value in the rule take the initial value listed with each descriptor in this specification.
These descriptors apply solely within the context of the <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule in which they are defined,
and do not apply to document language elements.
There is no notion of which elements the descriptors apply to or whether the values are inherited by child elements.
When a given descriptor occurs multiple times in a given <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule,
only the last specified value is used;
all prior values for that descriptor must be ignored.
<p> Defining a <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> makes it available to the entire document in which it is included.
If multiple <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rules are defined with the same name,
only one wins,
according to standard cascade rules.
<a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rules cascade "atomically":
if one replaces another of the same name,
it replaces it <em>entirely</em>,
rather than just replacing the specific descriptors it specifies.
<p> This at-rule conforms with the forward-compatible parsing requirement of CSS;
conformant parsers that don't understand these rules will ignore them without error.
Any descriptors that are not recognized or implemented by a given user agent must be ignored in their entirety;
they do not make the <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule invalid.
<h3 data-level=3.1 id=counter-style-system><span class=secno>3.1 </span><span class=content>
Counter algorithms: the <a class=property data-link-type=propdesc href=#descdef-system title=system>system</a> descriptor</span><a class=section-link href=#counter-style-system>§</a></h3>
<table class=descdef data-dfn-for=@counter-style><tr><th>Name:<td><dfn data-dfn-for=@counter-style data-dfn-type=descriptor id=descdef-system>system</dfn><tr><th>For:<td><a data-link-type=at-rule href=#at-ruledef-counter-style>@counter-style</a><tr><th>Value:<td>cyclic | numeric | alphabetic | symbolic | additive | <span class=nobr>[fixed <a class=production data-link-type=type href=http://dev.w3.org/csswg/css-syntax-3/#integer><var><integer></var></a>?]</span> | <span class=nobr>[ override <a class=production data-link-type=type href=#typedef-counter-style-name><var><counter-style-name></var></a> ]</span><tr><th>Initial:<td>symbolic</table>
<p> The <a class=property data-link-type=propdesc href=#descdef-system title=system>system</a> descriptor specifies which algorithm will be used to construct
the counter's representation based on the counter value. For example,
<a class=css data-link-type=maybe href=#valuedef-cyclic>cyclic</a> counter styles just cycle through their symbols repeatedly,
while <a data-link-for=system data-link-type=value href=#valuedef-numeric0>numeric</a> counter styles interpret their symbols as digits and
build their representation accordingly. The systems are defined as follows:
<h4 data-level=3.1.1 id=cyclic-system><span class=secno>3.1.1 </span><span class=content>
Cycling Symbols: the <a class=css data-link-type=maybe
23BA
href=#valuedef-cyclic>cyclic</a> system</span><a class=section-link href=#cyclic-system>§</a></h4>
<p> The <dfn data-dfn-for=@counter-style/system data-dfn-type=value id=valuedef-cyclic>cyclic</dfn> counter system cycles repeatedly through its provided symbols,
looping back to the beginning when it reaches the end of the list.
It can be used for simple bullets
(just provide a single <a href=#counter-symbol>counter symbol</a>),
or for cycling through multiple symbols.
The first <a href=#counter-symbol>counter symbol</a> is used as the representation of the value 1,
the second <a href=#counter-symbol>counter symbol</a> (if it exists) is used as the representation of the value 2, etc.
<p> If the system is <a class=css data-link-type=maybe href=#valuedef-cyclic>cyclic</a>,
the <a class=property data-link-type=propdesc href=#descdef-symbols title=symbols>symbols</a> descriptor must contain at least one <a href=#counter-symbol>counter symbol</a>,
or else the <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule is invalid.
This system is defined over all counter values.
<div class=example>
A "triangle bullet" counter style can be defined as:
<pre>@counter-style <dfn data-dfn-type=dfn id=triangle noexport="">triangle</dfn> {
system: cyclic;
symbols: ‣;
suffix: "";
}
</pre>
<p> It will then produce lists that look like:
<pre>‣ One
‣ Two
‣ Three
</pre> </div>
<p> If there are <var>N</var> <a href=#counter-symbol>counter symbols</a>
and a representation is being constructed for the integer <var>value</var>,
the representation is the <a href=#counter-symbol>counter symbol</a>
at index ( (<var>value</var>-1) mod <var>N</var>)
of the list of <a href=#counter-symbol>counter symbols</a> (0-indexed).
<h4 data-level=3.1.2 id=fixed-system><span class=secno>3.1.2 </span><span class=content>
Exhaustible Symbols: the <a class=css data-link-type=maybe href=#valuedef-fixed>fixed</a> system</span><a class=section-link href=#fixed-system>§</a></h4>
<p> The <dfn data-dfn-for=@counter-style/system data-dfn-type=value id=valuedef-fixed>fixed</dfn> counter system runs through its list of counter symbols once,
then falls back.
It is useful for representing counter styles that only have a finite number of representations.
For example, Unicode defines several limited-length runs of special characters meant for lists,
such as circled digits.
<p> If the system is <a class=css data-link-type=maybe href=#valuedef-fixed>fixed</a>,
the <a class=property data-link-type=propdesc href=#descdef-symbols title=symbols>symbols</a> descriptor must contain at least one <a href=#counter-symbol>counter symbol</a>,
or else the <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule is invalid.
This system is defined over counter values in a finite range,
starting with the <a href=#first-symbol-value>first symbol value</a> and having a length equal to the length of the list of <a href=#counter-symbol>counter symbols</a>.
<p> When this system is specified,
it may optionally have an integer provided after it,
which sets the <dfn data-dfn-type=dfn export="" id=first-symbol-value>first symbol value</dfn>.
If it is omitted, the <a href=#first-symbol-value>first symbol value</a> is 1.
<div class=example>
A "box-corner" counter style can be defined as:
<pre>@counter-style <dfn data-dfn-type=dfn id=box-corner noexport="">box-corner</dfn> {
system: fixed;
symbols: ◰ ◳ ◲ ◱;
suffix: ':';
}
</pre>
<p> It will then produce lists that look like:
<pre>◰: One
◳: Two
◲: Three
◱: Four
5: Five
6: Six
</pre> </div>
<p> The first <a href=#counter-symbol>counter symbol</a> is the representation for the <a href=#first-symbol-value>first symbol value</a>,
and subsequent counter values are represented by subsequent <a href=#counter-symbol>counter symbols</a>.
Once the list of <a href=#counter-symbol>counter symbols</a> is exhausted,
further values cannot be represented by this counter style,
and must instead be represented by the fallback counter style.
<h4 data-level=3.1.3 id=symbolic-system><span class=secno>3.1.3 </span><span class=content>
Repeating Symbols: the <a class=css data-link-type=maybe href=#valuedef-symbolic>symbolic</a> system</span><a class=section-link href=#symbolic-system>§</a></h4>
<p> The <dfn data-dfn-for='data-link-typesystem"' data-dfn-type=value id=valuedef-symbolic>symbolic</dfn> counter system cycles repeatedly through its provided symbols,
doubling, tripling, etc. the symbols on each successive pass through the list.
For example, if the original symbols were "*" and "†",
then on the second pass they would instead be "**" and "††",
while on the third they would be "***"and "†††", etc.
It can be used for footnote-style markers,
and is also sometimes used for alphabetic-style lists for a slightly different presentation than what the <a data-link-for=system data-link-type=value href=#valuedef-alphabetic0>alphabetic</a> system presents.
<p> If the system is <a class=css data-link-type=maybe href=#valuedef-symbolic>symbolic</a>,
the <a class=property data-link-type=propdesc href=#descdef-symbols title=symbols>symbols</a> descriptor must contain at least one <a href=#counter-symbol>counter symbol</a>,
or else the <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule is invalid.
This system is defined only over strictly positive counter values.
<div class=example>
An "footnote" counter style can be defined as:
<pre>@counter-style <dfn data-dfn-type=dfn id=footnote noexport="">footnote</dfn> {
system: symbolic;
symbols: '*' ⁑ † ‡;
suffix: "";
}
</pre>
<p> It will then produce lists that look like:
<pre>* One
⁑ Two
† Three
‡ Four
** Five
⁑⁑ Six
</pre> </div>
<div class=example>
Some style guides mandate a list numbering that looks similar to <a class=css data-link-type=maybe href=#valuedef-upper-alpha>upper-alpha</a>,
but repeats differently after the first 26 values,
instead going "AA", "BB", "CC", etc.
This can be achieved with the symbolic system:
<pre>@counter-style <dfn data-dfn-type=dfn id=upper-alpha-legal noexport="">upper-alpha-legal</dfn> {
system: symbolic;
symbols: A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z;
}
</pre>
<p> This style is identical to <a class=css data-link-type=maybe href=#valuedef-upper-alpha>upper-alpha</a> through the first 27 values,
but they diverge after that, with <a class=css data-link-type=maybe href=#valuedef-upper-alpha>upper-alpha</a> going "AB", "AC", "AD", etc.
Starting at the 53rd value, <a class=css data-link-type=maybe href=#valuedef-upper-alpha>upper-alpha</a> goes "BA", "BB", "BC", etc.,
while this style jumps into triple digits with "AAA", "BBB", "CCC", etc.
</div>
<p> To construct the representation, run the following algorithm:
<p> Let <var>N</var> be the length of the list of <a href=#counter-symbol>counter symbols</a>,
<var>value</var> initially be the counter value,
<var>S</var> initially be the empty string,
and <var>symbol(n)</var> be the nth <a href=#counter-symbol>counter symbol</a> in the list of <a href=#counter-symbol>counter symbols</a> (0-indexed).
<ol>
<li>Let the <var>chosen symbol</var> be <code class=inline>symbol(<var>value</var> mod <var>N</var>)</code>.
<li>Let the <var>representation length</var> be <code class=inline>floor( (<var>value</var> - 1) / <var>N</var> )</code>.
<li>Append the <var>chosen symbol</var> to <var>S</var> a number of times equal to the <var>representation length</var>.
</ol>
<p> Finally, return <var>S</var>.
<p> The <a class=css data-link-type=maybe href=#valuedef-symbolic>symbolic</a> system will produce representations with sizes that are linear in the magnitude of the counter value.
This can potentially be abused to generate excessively large representations
and consume undue amounts of the user's memory or even hang their browser.
User agents must support representations at least 20 characters long,
but they may choose to instead use the fallback style for representations that would be longer than 20 characters.
<h4 data-level=3.1.4 id=alphabetic-system><span class=secno>3.1.4 </span><span class=content>
Bijective Numerals: the <a data-link-for=system data-link-type=value href=#valuedef-alphabetic0>alphabetic</a> system</span><a class=section-link href=#alphabetic-system>§</a></h4>
<p> The <dfn data-dfn-for=@counter-style/system data-dfn-type=value id=valuedef-alphabetic0>alphabetic</dfn> counter system interprets the list of <a href=#counter-symbol>counter symbols</a> as digits to an <em>alphabetic</em> numbering system,
similar to the default <a class=css data-link-type=maybe href=#valuedef-lower-alpha>lower-alpha</a> counter style,
which wraps from "a", "b", "c", to "aa", "ab", "ac".
Alphabetic numbering systems do not contain a digit representing 0;
so the first value when a new digit is added is composed solely of the first digit.
Alphabetic numbering systems are commonly used for lists,
and also appear in many spreadsheet programs to number columns.
The first <a href=#counter-symbol>counter symbol</a> in the list is interpreted as the digit 1,
the second as the digit 2,
and so on.
<p> If the system is <a data-link-for=system data-link-type=value href=#valuedef-alphabetic0>alphabetic</a>,
the <a class=property data-link-type=propdesc href=#descdef-symbols title=symbols>symbols</a> descriptor must contain at least two <a href=#counter-symbol>counter symbols</a>,
or else the <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule is invalid.
This system is defined only over strictly positive counter values.
<div class=example>
A counter style using go stones can be defined as:
<pre>@counter-style <dfn data-dfn-type=dfn id=go noexport="">go</dfn> {
system: alphabetic;
symbols: url(white.svg) url(black.svg);
suffix: "";
}
</pre>
<p> It will then produce lists that look like:
<div class=alphabetic-example>
<span><img alt="" src=images/white.svg></span> One<br>
<span><img alt="" src=images/black.svg></span> Two<br>
<span><img alt="" src=images/white.svg><img alt="" src=images/white.svg></span> Three<br>
<span><img alt="" src=images/white.svg><img alt="" src=images/black.svg></span> Four<br>
<span><img alt="" src=images/black.svg><img alt="" src=images/white.svg></span> Five<br>
<span><img alt="" src=images/black.svg><img alt="" src=images/black.svg></span> Six<br>
<span><img alt="" src=images/white.svg><img alt="" src=images/white.svg><img alt="" src=images/white.svg></span> Seven
</div>
<p class=note> Note: This example requires support for SVG images to display correctly.
</div>
<p> If there are <var>N</var> <a href=#counter-symbol>counter symbols</a>,
the representation is a base <var>N</var> alphabetic number using the <a href=#counter-symbol>counter symbols</a> as digits.
To construct the representation, run the following algorithm:
<p> Let <var>N</var> be the length of the list of <a href=#counter-symbol>counter symbols</a>,
<var>value</var> initially be the counter value,
<var>S</var> initially be the empty string,
and <var>symbol(n)</var> be the nth <a href=#counter-symbol>counter symbol</a> in the list of <a href=#counter-symbol>counter symbols</a> (0-indexed).
<p> While <var>value</var> is not equal to 0:
<ol>
<li>Set <var>value</var> to <code><var>value</var> - 1</code>.
<li>Prepend <var>symbol( <var>value</var> mod <var>N</var> )</var>
to <var>S</var>.
<li>Set <var>value</var> to <code>floor( <var>value</var> / <var>N</var> )</code>.
</ol>
<p> Finally, return <var>S</var>.
<h4 data-level=3.1.5 id=numeric-system><span class=secno>3.1.5 </span><span class=content>
Positional Numerals: the <a data-link-for=system data-link-type=value href=#valuedef-numeric0>numeric</a> system</span><a class=section-link href=#numeric-system>§</a></h4>
<p> The <dfn data-dfn-for=@counter-style/system data-dfn-type=value id=valuedef-numeric0>numeric</dfn> counter system interprets the list of <a href=#counter-symbol>counter symbols</a>
as digits to a "place-value" numbering system,
similar to the default <a class=css data-link-type=maybe href=#valuedef-decimal>decimal</a> counter style.
The first <a href=#counter-symbol>counter symbol</a> in the list is interpreted as the digit 0,
the second as the digit 1,
and so on.
<p> If the system is <a data-link-for=system data-link-type=value href=#valuedef-numeric0>numeric</a>,
the <a class=property data-link-type=propdesc href=#descdef-symbols title=symbols>symbols</a> descriptor must contain at least two <a href=#counter-symbol>counter symbols</a>,
or else the <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule is invalid.
This system is defined over all counter values.
<div class=example>
A "trinary" counter style can be defined as:
<pre>@counter-style <dfn data-dfn-type=dfn id=trinary noexport="">trinary</dfn> {
system: numeric;
symbols: '0' '1' '2';
}
</pre>
<p> It will then produce lists that look like:
<pre>1. One
2. Two
10. Three
11. Four
12. Five
20. Six
</pre> </div>
<p> If there are <var>N</var> <a href=#counter-symbol>counter symbols</a>,
the representation is a base <var>N</var> number using the <a href=#counter-symbol>counter symbols</a> as digits.
To construct the representation, run the following algorithm:
<p> Let <var>N</var> be the length of the list of <a href=#counter-symbol>counter symbols</a>,
<var>value</var> initially be the counter value,
<var>S</var> initially be the empty string,
and <var>symbol(n)</var> be the nth <a href=#counter-symbol>counter symbol</a> in the list of <a href=#counter-symbol>counter symbols</a> (0-indexed).
<ol>
<li>If <var>value</var> is 0, append <var>symbol(0)</var> to
<var>S</var> and return <var>S</var>.
<li>While <var>value</var> is not equal to 0:
<ol>
<li>Prepend <var>symbol( <var>value</var> mod <var>N</var> )</var>
to <var>S</var>.
<li>Set <var>value</var> to <code>floor( <var>value</var> / <var>N</var> )</code>.
</ol>
<li>Return <var>S</var>.
</ol>
<h4 data-level=3.1.6 id=additive-system><span class=secno>3.1.6 </span><span class=content>
Accumulating Numerals: the <a class=css data-link-type=maybe href=#valuedef-additive>additive</a> system</span><a class=section-link href=#additive-system>§</a></h4>
<p> The <dfn data-dfn-for=@counter-style/system data-dfn-type=value id=valuedef-additive>additive</dfn> counter system is used to represent "sign-value" numbering systems,
which, rather than using reusing digits in different positions to change their value,
define additional digits with much larger values,
so that the value of the number can be obtained by adding all the digits together.
This is used in Roman numerals
and other numbering systems around the world.
<p> If the system is <a class=css data-link-type=maybe href=#valuedef-additive>additive</a>,
the <a class=property data-link-type=propdesc href=#descdef-additive-symbols title=additive-symbols>additive-symbols</a> descriptor must contain at least one <a href=#additive-tuple>additive tuple</a>,
or else the <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule is invalid.
This system is nominally defined over all counter values
(see algorithm, below, for exact details).
<div class=example>
A "dice" counter style can be defined as:
<pre>@counter-style <dfn data-dfn-type=dfn id=dice noexport="">dice</dfn> {
system: additive;
additive-symbols: 6 ⚅, 5 ⚄, 4 ⚃, 3 ⚂, 2 ⚁, 1 ⚀;
suffix: "";
}
</pre>
<p> It will then produce lists that look like:
<pre>⚀ One
⚁ Two
⚂ Three
...
⚅⚄ Eleven
⚅⚅ Twelve
⚅⚅⚀ Thirteen
</pre> </div>
<p> To construct the representation, run this algorithm:
<p> Let <var>value</var> initially be the counter value,
<var>S</var> initially be the empty string,
and <var>symbol list</var> initially be the list of <a href=#additive-tuple>additive tuples</a>.
<ol>
<li>If <var>value</var> is initially 0, and there is an <a href=#additive-tuple>additive tuple</a> with a weight of 0, append that tuple's <a href=#counter-symbol>counter symbol</a> to S and return S.
<li>While <var>value</var> is greater than 0 and there are elements left in the <var>symbol list</var>:
<ol>
<li>Pop the first <a href=#additive-tuple>additive tuple</a> from the <var>symbol list</var>.
This is the <dfn data-dfn-type=dfn id=current-tuple title="current tuple|current tuple's">current tuple</dfn>.
<li>Append the <a href=#current-tuple>current tuple</a>'s <a href=#counter-symbol>counter symbol</a> to <var>S</var>
<code>floor( <var>value</var> / <var><a href=#current-tuple>current tuple's</a> weight</var> )</code>
times (this may be 0).
<li>Decrement <var>value</var> by the <var><a href=#current-tuple>current tuple's</a></var> weight multiplied
by the number of times the <a href=#current-tuple>current tuple</a> was appended to <var>S</var>
in the previous step.
</ol>
<li>If the loop ended because <var>value</var> is 0, return S. Otherwise, the given counter value cannot be represented by this counter style, and must instead be represented by the fallback counter style.
</ol>
<p> The <a class=css data-link-type=maybe href=#valuedef-additive>additive</a> system will produce representations with sizes that are linear in the magnitude of the counter value.
This can potentially be abused to generate excessively large representations and consume undue amounts of the user's memory or even hang their browser.
User agents must support representations at least 20 characters long,
but they may choose to instead use the fallback style for representations that would be longer than 20 characters.
<p class=note> Note: All of the predefined additive <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rules in this specification
produce representations for every value in their range,
but it's possible to produce values for <span class=css data-link-type=maybe>additive-symbols</span> that will fail to find a representation
with the algorithm defined above,
even though theoretically a representation could be found.
For example, if a <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> was defined with <span class=css data-link-type=maybe>additive-symbols: 3 "a", 2 "b";</span>,
the algorithm defined above will fail to find a representation for a counter value of 4,
even though theoretically a "bb" representation would work.
While unfortunate, this is required to maintain the property that the algorithm runs in linear time
relative to the size of the counter value.
<h4 data-level=3.1.7 id=override-system><span class=secno>3.1.7 </span><span class=content>
Tweaking Existing Counter Styles: the <a class=css data-link-type=maybe href=#valuedef-override>override</a> system</span><a class=section-link href=#override-system>§</a></h4>
<p> The <dfn data-dfn-for=@counter-style/system data-dfn-type=value id=valuedef-override>override</dfn> system allows an author to use the algorithm of another counter style,
but alter other aspects,
such as the negative sign or the suffix.
If a counter style uses the <a class=css data-link-type=maybe href=#valuedef-override>override</a> system,
any unspecified descriptors must be taken from the overridden counter style specified,
rather than taking their initial values.
<p> If a @counter-style uses the <a class=css data-link-type=maybe href=#valuedef-override>override</a> system,
it must not contain a <a class=property data-link-type=propdesc href=#descdef-symbols title=symbols>symbols</a> or <a class=property data-link-type=propdesc href=#descdef-additive-symbols title=additive-symbols>additive-symbols</a> descriptor,
or else the <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule is invalid.
If the specified counter style name isn't the name of any currently-defined counter style,
it must be treated as if it was overriding the <a class=css data-link-type=maybe href=#valuedef-decimal>decimal</a> counter style.
<h3 data-level=3.2 id=counter-style-negative><span class=secno>3.2 </span><span class=content>
Formatting negative values: the <a class=property data-link-type=propdesc href=#descdef-negative title=negative>negative</a> descriptor</span><a class=section-link href=#counter-style-negative>§</a></h3>
<table class=descdef data-dfn-for=@counter-style><tr><th>Name:<td><dfn data-dfn-for=@counter-style data-dfn-type=descriptor id=descdef-negative>negative</dfn><tr><th>For:<td><a data-link-type=at-rule href=#at-ruledef-counter-style>@counter-style</a><tr><th>Value:<td><a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a> <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a>?<tr><th>Initial:<td>"\2D" ("-" hyphen-minus)</table>
<p> The <a class=property data-link-type=propdesc href=#descdef-negative title=negative>negative</a> descriptor defines how to alter the representation when
the counter value is negative.
<p> The first <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a> in the value is prepended to the representation when the
counter value is negative. The second <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a>, if specified, is appended
to the representation when the counter value is negative.
<div class=example>
For example, specifying <span class=css data-link-type=maybe>negative: "(" ")";</span> will make negative
values be wrapped in parentheses, which is sometimes used in financial
contexts, like "(2) (1) 0 1 2 3...".
</div>
<p> Not all <a class=property data-link-type=propdesc href=#descdef-system title=system>system</a> values use a negative sign.
In particular, a counter style is <dfn data-dfn-type=dfn export="" id=negative-capable>negative-capable</dfn>
is one where its <a class=property data-link-type=propdesc href=#descdef-system title=system>system</a> value is
<a class=css data-link-type=maybe href=#valuedef-symbolic>symbolic</a>,
<a data-link-for=system data-link-type=value href=#valuedef-alphabetic0>alphabetic</a>,
<a data-link-for=system data-link-type=value href=#valuedef-numeric0>numeric</a>,
<a class=css data-link-type=maybe href=#valuedef-additive>additive</a>,
or <a class=css data-link-type=maybe href=#valuedef-override>override</a> if the overridden counter style is itself <a href=#negative-capable>negative-capable</a>.
If a counter style is not <a href=#negative-capable>negative-capable</a>,
it ignores the negative sign when <a href=#generate-a-counter-representation title="generate a counter representation">generating a counter representation</a>.
<h3 data-level=3.3 id=counter-style-prefix><span class=secno>3.3 </span><span class=content>
Symbols before the marker: the <a class=property data-link-type=propdesc href=#descdef-prefix title=prefix>prefix</a> descriptor</span><a class=section-link href=#counter-style-prefix>§</a></h3>
<table class=descdef data-dfn-for=@counter-style><tr><th>Name:<td><dfn data-dfn-for=@counter-style data-dfn-type=descriptor id=descdef-prefix>prefix</dfn><tr><th>For:<td><a data-link-type=at-rule href=#at-ruledef-counter-style>@counter-style</a><tr><th>Value:<td><a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a><tr><th>Initial:<td>"" (the empty string)</table>
<p> The <a class=property data-link-type=propdesc href=#descdef-prefix title=prefix>prefix</a> descripter specifies a <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a> that is prepended to the
marker representation. Prefixes are only added by the algorithm for constructing
the default contents of the <span class=css data-link-type=maybe>::marker</span> pseudo-element; the prefix is not
added automatically when the counter() or counters() functions are used.
Prefixes come before any negative sign.
<h3 data-level=3.4 id=counter-style-suffix><span class=secno>3.4 </span><span class=content>
Symbols after the marker: the <a class=property data-link-type=propdesc href=#descdef-suffix title=suffix>suffix</a> descriptor</span><a class=section-link href=#counter-style-suffix>§</a></h3>
<table class=descdef data-dfn-for=@counter-style><tr><th>Name:<td><dfn data-dfn-for=@counter-style data-dfn-type=descriptor id=descdef-suffix>suffix</dfn><tr><th>For:<td><a data-link-type=at-rule href=#at-ruledef-counter-style>@counter-style</a><tr><th>Value:<td><a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a><tr><th>Initial:<td>"\2E" ("." full stop)</table>
<p> The <a class=property data-link-type=propdesc href=#descdef-suffix title=suffix>suffix</a> descripter specifies a <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a> that is appended to the
marker representation. Suffixes are only added by the algorithm for constructing
the default contents of the <span class=css data-link-type=maybe>::marker</span> pseudo-element; the suffix is not
added automatically when the counter() or counters() functions are used.
Suffixes are added to the representation after negative signs.
<h3 data-level=3.5 id=counter-style-range><span class=secno>3.5 </span><span class=content>
Limiting the counter scope: the <a class=property data-link-type=propdesc href=#descdef-range title=range>range</a> descriptor</span><a class=section-link href=#counter-style-range>§</a></h3>
<table class=descdef data-dfn-for=@counter-style><tr><th>Name:<td><dfn data-dfn-for=@counter-style data-dfn-type=descriptor id=descdef-range>range</dfn><tr><th>For:<td><a data-link-type=at-rule href=#at-ruledef-counter-style>@counter-style</a><tr><th>Value:<td>[ [ <a class=production data-link-type=type href=http://dev.w3.org/csswg/css-syntax-3/#integer><var><integer></var></a> | infinite ]{2} ]# | auto<tr><th>Initial:<td>auto</table>
<p> The <a class=property data-link-type=propdesc href=#descdef-range title=range>range</a> descriptor defines the ranges over which the counter style is defined.
If a counter style is used to represent a counter value outside of its ranges,
the counter style instead drops down to its fallback counter style.
<dl data-dfn-for=@counter-style/range>
<dt><dfn data-dfn-for=@counter-style/range data-dfn-type=value id=valuedef-auto0>auto</dfn>
<dd>
The range depends on the counter system.
For <a class=css data-link-type=maybe href=#valuedef-cyclic>cyclic</a>, <a data-link-for=system data-link-type=value href=#valuedef-numeric0>numeric</a>, and <a class=css data-link-type=maybe href=#valuedef-fixed>fixed</a> systems,
the range is negative infinity to positive infinity.
For <a data-link-for=system data-link-type=value href=#valuedef-alphabetic0>alphabetic</a> and <a class=css data-link-type=maybe href=#valuedef-symbolic>symbolic</a> systems,
the range is 1 to positive infinity.
For <a class=css data-link-type=maybe href=#valuedef-additive>additive</a> systems,
the range is 0 to positive infinity.
For <a class=css data-link-type=maybe href=#valuedef-override>override</a> systems,
the range is identical to the overridden system.
<dt>[ [ <a class=production data-link-type=type href=http://dev.w3.org/csswg/css-syntax-3/#integer><var><integer></var></a> | infinite ]{2} ]#
<dd>
This defines a comma-separated list of ranges.
For each individual range,
the first value is the lower bound
and the second value is the upper bound.
This range is inclusive - it contains both the lower and upper bound numbers.
If <span class=css data-link-type=maybe>infinite</span> is used as the first value in a range,
it represents negative infinity;
if used as the second value,
it represents positive infinity.
The range of the counter style is the union of all the ranges defined in the list.
<p> If the lower bound of any range is higher than the upper bound,
the entire descriptor is invalid and must be ignored.
</dl>
<p> Implementations must support ranges with a lower bound of at least -2<sup>15</sup>
and an upper bound of at least 2<sup>15</sup>-1
(the range of a signed 2-byte int).
They may support higher ranges.
If any specified bound is outside of the implementation's supported bounds,
it must be treated as the closest bound that the implementation does support.
<h3 data-level=3.6 id=counter-style-pad><span class=secno>3.6 </span><span class=content>
Zero-Padding and Constant-Width Representations: the <a class=property data-link-type=propdesc href=#descdef-pad title=pad>pad</a> descriptor</span><a class=section-link href=#counter-style-pad>§</a></h3>
<table class=descdef data-dfn-for=@counter-style><tr><th>Name:<td><dfn data-dfn-for=@counter-style data-dfn-type=descriptor id=descdef-pad>pad</dfn><tr><th>For:<td><a data-link-type=at-rule href=#at-ruledef-counter-style>@counter-style</a><tr><th>Value:<td><a class=production data-link-type=type href=http://dev.w3.org/csswg/css-syntax-3/#integer><var><integer></var></a> && <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a><tr><th>Initial:<td>0 ""</table>
<p> The <a class=property data-link-type=propdesc href=#descdef-pad title=pad>pad</a> descriptor allows an author to specify a "fixed-width" counter style,
where representations shorter than the pad value are padded with a particular <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a>.
Representations larger than the specified pad value are constructed as normal.
<dl>
<dt><a class=production data-link-type=type href=http://dev.w3.org/csswg/css-syntax-3/#integer><var><integer></var></a> && <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a>
<dd>
The <a class=production data-link-type=type href=http://dev.w3.org/csswg/css-syntax-3/#integer><var><integer></var></a> specifies a minimum number of <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a>s that all counter representations must reach.
If a counter representation would be generated using less <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a>s than the specified <a class=production data-link-type=type href=http://dev.w3.org/csswg/css-syntax-3/#integer><var><integer></var></a>
(before adding prefixes/suffixes/negatives),
prepend copies of the specified <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a> to the representation
until the number of symbols reaches the specified pad value.
<p> The <a class=production data-link-type=type href=http://dev.w3.org/csswg/css-syntax-3/#integer><var><integer></var></a> must be non-negative.
A negative value is a syntax error.
<p> If the counter value is negative
and the counter style is <a href=#negative-capable>negative-capable</a>,
treat the minimum number of <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a>s as being one or two smaller when determining how many copies to prepend,
depending on whether the <a class=property data-link-type=propdesc href=#descdef-negative title=negative>negative</a> descriptor's value is one or two <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a>s.
</dl>
<div class=example>
The most common example of "fixed-width" numbering is zero-padded decimal numbering.
If an author knows that the numbers used will be less than a thousand, for example,
it can be zero-padded with a simple <span class=css data-link-type=maybe>width: 3 "0";</span> descriptor,
ensuring that all of the representations are 3 digits wide.
<p> This will cause, for example,
1 to be represented as "001",
20 to be represented as "020",
300 to be represented as "300",
4000 to be represented as "4000",
and -5 to be represented as "-05".
</div>
<p class=note> Note: The <a class=property data-link-type=propdesc href=#descdef-pad title=pad>pad</a> descriptor counts the number of <em><a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a>s</em> used to construct the representation,
not the number of characters,
and also pads the representation with <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a>s.
For many styles, the distinction is irrelevant,
as all the <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a>s are single-chararacter,
but if a style uses multi-character <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a>s,
care must be taken not to accidentally specify <a class=property data-link-type=propdesc href=#descdef-pad title=pad>pad</a> in terms of characters.
<h3 data-level=3.7 id=counter-style-fallback><span class=secno>3.7 </span><span class=content>
Defining fallback: the <a class=property data-link-type=propdesc href=#descdef-fallback title=fallback>fallback</a> descriptor</span><a class=section-link href=#counter-style-fallback>§</a></h3>
<table class=descdef data-dfn-for=@counter-style><tr><th>Name:<td><dfn data-dfn-for=@counter-style data-dfn-type=descriptor id=descdef-fallback>fallback</dfn><tr><th>For:<td><a data-link-type=at-rule href=#at-ruledef-counter-style>@counter-style</a><tr><th>Value:<td><a class=production data-link-type=type href=#typedef-counter-style-name><var><counter-style-name></var></a><tr><th>Initial:<td>decimal</table>
<p> The <a class=property data-link-type=propdesc href=#descdef-fallback title=fallback>fallback</a> descriptor specifies a fallback counter style to be used
when the current counter style can't create a representation for a given
counter value. For example, if a counter style defined with a range of 1-10
is asked to represent a counter value of 11, the counter value's representation
is instead constructed with the fallback counter style (or possibly the
fallback style's fallback style, if the fallback style can't represent that
value, etc.).
<p> If the value of the <a class=property data-link-type=propdesc href=#descdef-fallback title=fallback>fallback</a> descriptor isn't the name of any
currently-defined counter style, the used value of the <a class=property data-link-type=propdesc href=#descdef-fallback title=fallback>fallback</a> descriptor
is <a class=css data-link-type=maybe href=#valuedef-decimal>decimal</a> instead. Similarly, while following fallbacks to find
a counter style that can render the given counter value, if a loop in the
specified fallbacks is detected, the <a class=css data-link-type=maybe href=#valuedef-decimal>decimal</a> style must be used instead.
<p class=note>Note that it is not necessarily an error to specify fallback
loops. For example, if an author desires a counter style with significantly
different representations for even and odd counter values, they may find it
easiest to define one style that can only represent odd values and one that
can only represent even values, and specify each as the fallback for the
other one. Though the fallback graph is circular, at no point do you encounter
a loop while following these fallbacks - every counter value is represented
by one or the other counter style.
<h3 data-level=3.8 id=counter-style-symbols><span class=secno>3.8 </span><span class=content>
Marker characters: the <a class=property data-link-type=propdesc href=#descdef-symbols title=symbols>symbols</a> and <a class=property data-link-type=propdesc href=#descdef-additive-symbols title=additive-symbols>additive-symbols</a> descriptors</span><a class=section-link href=#counter-style-symbols>§</a></h3>
<table class=descdef data-dfn-for=@counter-style><tr><th>Name:<td><dfn data-dfn-for=@counter-style data-dfn-type=descriptor id=descdef-symbols>symbols</dfn><tr><th>For:<td><a data-link-type=at-rule href=#at-ruledef-counter-style>@counter-style</a><tr><th>Value:<td><a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a>+<tr><th>Initial:<td>n/a</table>
<table class=descdef data-dfn-for=@counter-style><tr><th>Name:<td><dfn data-dfn-for=@counter-style data-dfn-type=descriptor id=descdef-additive-symbols>additive-symbols</dfn><tr><th>For:<td><a data-link-type=at-rule href=#at-ruledef-counter-style>@counter-style</a><tr><th>Value:<td>[ <a class=production data-link-type=type href=http://dev.w3.org/csswg/css-syntax-3/#integer><var><integer></var></a> && <a class=production data-link-type=type href=#typedef-symbol><var><symbol></var></a> ]#<tr><th>Initial:<td>n/a</table>
<pre class=prod><dfn data-dfn-type=type id=typedef-symbol><symbol></dfn> = <a class=production data-link-type=type><var><string></var></a> | <a class=production data-link-type=type href=http://dev.w3.org/csswg/css-images-3/#image-type><var>&
7B3C
;lt;image></var></a> | <a class=production data-link-type=type href=http://dev.w3.org/csswg/css-grid-1/#grid-placement-slot><var><ident></var></a></pre>
<p> The <a class=property data-link-type=propdesc href=#descdef-symbols title=symbols>symbols</a> and <a class=property data-link-type=propdesc href=#descdef-additive-symbols title=additive-symbols>additive-symbols</a> descriptors specify the symbols
used by the marker-construction algorithm specified by the <a class=property data-link-type=propdesc href=#descdef-system title=system>system</a> descriptor.
The <a class=property data-link-type=propdesc href=#descdef-symbols title=symbols>symbols</a> descriptor must be specified if the counter system is <a class=css data-link-type=maybe href=#valuedef-cyclic>cyclic</a>,
<a data-link-for=system data-link-type=value href=#valuedef-numeric0>numeric</a>, <a data-link-for=system data-link-type=value href=#valuedef-alphabetic0>alphabetic</a>, <a class=css data-link-type=maybe href=#valuedef-symbolic>symbolic</a>, or <a class=css data-link-type=maybe href=#valuedef-fixed>fixed</a>, and the
<a class=property data-link-type=propdesc href=#descdef-additive-symbols title=additive-symbols>additive-symbols</a> descriptor must be specified if the counter system is
<a class=css data-link-type=maybe href=#valuedef-additive>additive</a>; otherwise, the <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> is invalid and must be ignored.
<p> Some counter systems specify that the <a class=property data-link-type=propdesc href=#descdef-symbols title=symbols>symbols</a> descriptor must have at
least two entries. If the counter style's system is such, and the <a class=property data-link-type=propdesc href=#descdef-symbols title=symbols>symbols</a>
descriptor has only a single entry, the counter style is invalid and must
be ignored.
<p> Each entry in the <a class=property data-link-type=propdesc href=#descdef-symbols title=symbols>symbols</a> descriptor's value defines a <dfn data-dfn-type=dfn export="" id=counter-symbol>counter symbol</dfn>,
which is interpreted differently based on the counter style's system. Each
entry in the <a class=property data-link-type=propdesc href=#descdef-additive-symbols title=additive-symbols>additive-symbols</a> descriptor's value defines an <dfn data-dfn-type=dfn export="" id=additive-tuple>additive tuple</dfn>,
which consists of a <a href=#counter-symbol>counter symbol</a> and a non-negative integer weight.
Each weight must be a non-negative integer, and the <a href=#additive-tuple>additive tuples</a>
must be specified in order of descending weight; otherwise, the @counter-style
is invalid and must be ignored.
<p> <a href=#counter-symbol>Counter symbols</a> may be strings, images, or identifiers,
and the three types can be mixed in a single descriptor.
Counter representations are constructed by concatenating counter symbols together.
Identifiers are rendered as strings containing the same characters.
Images are rendered as inline replaced elements.
The <a href=http://dev.w3.org/csswg/css3-images/#default-object-size>default object size</a> of an image <a href=#counter-symbol>counter symbol</a> is a 1em by 1em square.
<p class=note> Note: If using identifiers rather than strings to define the symbols,
be aware of the syntax of identifiers.
In particular, ascii non-letters like "*" are not identifiers,
and so must be quoted in a string.
Hex escapes,
used in several of the counter styles defined in this specification,
"eat" the following space
(to allow a digit to follow a hex escape without ambiguity),
so two spaces must be put after a hex escape
to separate it from the following one,
or else they'll be considered adjacent,
and part of the same identifier.
<h3 data-level=3.9 id=counter-style-speak-as><span class=secno>3.9 </span><span class=content>
Speech Synthesis: the <a class=property data-link-type=propdesc href=#descdef-speak-as title=speak-as>speak-as</a> descriptor</span><a class=section-link href=#counter-style-speak-as>§</a></h3>
<table class=descdef data-dfn-for=@counter-style><tr><th>Name:<td><dfn data-dfn-for=@counter-style data-dfn-type=descriptor id=descdef-speak-as>speak-as</dfn><tr><th>For:<td><a data-link-type=at-rule href=#at-ruledef-counter-style>@counter-style</a><tr><th>Value:<td>auto | numeric | alphabetic | bullet | <a class=production data-link-type=type href=#typedef-counter-style-name><var><counter-style-name></var></a><tr><th>Initial:<td>auto</table>
<p> A counter style can be constructed with a meaning that is obvious visually,
but impossible to meaningfully represent via a speech synthesizer,
or possible but nonsensical when naively read out.
The <a class=property data-link-type=propdesc href=#descdef-speak-as title=speak-as>speak-as</a> descriptor describes how to synthesize the spoken form of a counter formatted with the given counter style.
Values have the following meanings:
<dl data-dfn-for=@counter-style/speak-as>
<dt><dfn data-dfn-for=@counter-style/speak-as data-dfn-type=value id=valuedef-auto>auto</dfn>
<dd>
If the counter style's <a class=property data-link-type=propdesc href=#descdef-system title=system>system</a> is <a data-link-for=system data-link-type=value href=#valuedef-alphabetic0>alphabetic</a>, this value computes to <a data-link-for=speak-as data-link-type=value href=#valuedef-alphabetic>alphabetic</a>.
If the <a class=property data-link-type=propdesc href=#descdef-system title=system>system</a> is <a class=css data-link-type=maybe href=#valuedef-cyclic>cyclic</a>, this value computes to <a class=css data-link-type=maybe href=#valuedef-bullet>bullet</a>.
Otherwise, this value computes to <a data-link-for=speak-as data-link-type=value href=#valuedef-numeric>numeric</a>.
<dt><dfn data-dfn-for=@counter-style/speak-as data-dfn-type=value id=valuedef-numeric>numeric</dfn>
<dd>
The counter's value is spoken as a number in the document language.
<dt><dfn data-dfn-for=@counter-style/speak-as data-dfn-type=value id=valuedef-alphabetic>alphabetic</dfn>
<dd>
<a href=#generate-a-counter-representation>Generate a counter representation</a> for the value as normal,
then spell it out letter-by-letter in the document language.
If the UA does not know how to pronounce the symbols,
it may handle it as <a data-link-for=speak-as data-link-type=value href=#valuedef-numeric>numeric</a>.
<p> For example, <a class=css data-link-type=maybe href=#valuedef-lower-greek>lower-greek</a> in English would be read out as "alpha", "beta", "gamma", etc.
Conversely, <a class=css data-link-type=maybe href=#valuedef-upper-latin>upper-latin</a> in French would be read out as (in phonetic notation) /a/, /be/, /se/, etc.
<dt><dfn data-dfn-for=@counter-style/speak-as data-dfn-type=value id=valuedef-bullet>bullet</dfn>
<dd>
The UA speaks a UA-defined phrase or audio cue that represents a list item being read out.
<dt><dfn data-dfn-for=@counter-style/speak-as data-dfn-type=value id=valuedef-counter-style-name><a class=production data-link-type=type href=#typedef-counter-style-name><var><counter-style-name></var></a></dfn>
<dd>
The counter's value is instead spoken out in the specific style.
If the specified style does not exist,
this value is treated as <a data-link-for=speak-as data-link-type=value href=#valuedef-auto>auto</a>.
</dl>
<div class=example>
The ability to defer pronunciation to another counter style can help when the symbols being used aren't actually letters.
For example, here's a possible definition of a <a class=css data-link-type=maybe href=#circled-lower-latin>circled-lower-latin</a> counter-style, using some special unicode characters:
<pre class=stylesheet>@counter-style <dfn data-dfn-type=dfn id=circled-lower-latin noexport="">circled-lower-latin</dfn> {
system: alphabetic;
speak-as: lower-latin;
symbols: ⓐ ⓑ ⓒ ⓓ ⓔ ⓕ ⓖ ⓗ ⓘ ⓙ ⓚ ⓛ ⓜ ⓝ ⓞ ⓟ ⓠ ⓡ ⓢ ⓣ ⓤ ⓥ ⓦ ⓧ ⓨ ⓩ;
suffix: "";
}
</pre>
<p> Setting its <a class=property data-link-type=propdesc href=#descdef-system title=system>system</a> to <a data-link-for=system data-link-type=value href=#valuedef-alphabetic0>alphabetic</a> would normally make the UA try to read out the names of the characters,
but in this case that might be something like "Circled Letter A",
which is unlikely to make sense.
Instead, explicitly setting <a class=property data-link-type=propdesc href=#descdef-speak-as title=speak-as>speak-as</a> to <a class=css data-link-type=maybe href=#valu
33B0
edef-lower-latin>lower-latin</a> ensures that they get read out as their corresponding latin letters, as intended.
</div>
<!-- ====================================================================== -->
<h2 data-level=4 id=symbols-function><span class=secno>4 </span><span class=content>
Defining Anonymous Counter Styles: the <a class=css data-link-type=maybe href=#funcdef-symbols>symbols()</a> function</span><a class=section-link href=#symbols-function>§</a></h2>
<p> The <a class=css data-link-type=maybe href=#funcdef-symbols>symbols()</a> function allows a <a href=#counter-style>counter style</a> to be defined inline in a property value,
for when a style is used only once in a stylesheet and defining a full <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule would be overkill.
It does not provide the full feature-set of the <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule,
but provides a sufficient subset to still be useful.
The syntax of the <a class=css data-link-type=maybe href=#funcdef-symbols>symbols()</a> rule is:
<pre class=prod> <dfn data-dfn-type=function id=funcdef-symbols>symbols()</dfn> = symbols( <a class=production data-link-type=type href=#typedef-symbols-type><var><symbols-type></var></a>? [ <a class=production data-link-type=type><var><string></var></a> | <a class=production data-link-type=type href=http://dev.w3.org/csswg/css-images-3/#image-type><var><image></var></a> ]+ );
<dfn data-dfn-type=type id=typedef-symbols-type><symbols-type></dfn> = cyclic | numeric | alphabetic | symbolic | fixed;
</pre>
<p> The <a class=css data-link-type=maybe href=#funcdef-symbols>symbols()</a> function defines an anonymous counter style
with no name,
a <a class=property data-link-type=propdesc href=#descdef-prefix title=prefix>prefix</a> and <a class=property data-link-type=propdesc href=#descdef-suffix title=suffix>suffix</a> of <span class=css data-link-type=maybe>""</span> (the empty string),
a <a class=property data-link-type=propdesc href=#descdef-range title=range>range</a> of <a data-link-for=range data-link-type=value href=#valuedef-auto0>auto</a>,
a <a class=property data-link-type=propdesc href=#descdef-fallback title=fallback>fallback</a> of <a class=css data-link-type=maybe href=#valuedef-decimal>decimal</a>,
and a <a class=property data-link-type=propdesc href=#descdef-negative title=negative>negative</a> of <span class=css data-link-type=maybe>"\2D"</span> ("-" hyphen-minus).
The counter style's algorithm is constructed
by consulting the previous chapter using the provided system —
or <a class=css data-link-type=maybe href=#valuedef-symbolic>symbolic</a> if the system was omitted —
and the provided <a class=production data-link-type=type><var><string></var></a>s and <a class=production data-link-type=type href=http://dev.w3.org/csswg/css-images-3/#image-type><var><image></var></a>s as the value of the <a class=property data-link-type=propdesc href=#descdef-symbols title=symbols>symbols</a> property.
If the system is <a class=css data-link-type=maybe href=#valuedef-fixed>fixed</a>, the <a href=#first-symbol-value>first symbol value</a> is <span class=css data-link-type=maybe>1</span>.
<div class=example>
This code:
<pre>ol { list-style: symbols("*" "\2020" "\2021" "\A7"); }</pre>
<p> will produce lists that look like:
<pre>* One
† Two
‡ Three
§ Four
** Five
†† Six
‡‡ Seven
</pre>
<p> On the other hand, specifying the system of counter, like so:
<pre>ol { list-style: symbols(cyclic "*" "\2020" "\2021" "\A7"); }</pre>
<p> will produce lists that look like:
<pre>* One
† Two
‡ Three
§ Four
* Five
† Six
‡ Seven
</pre> </div>
<p class=note> Note: the <a class=css data-link-type=maybe href=#funcdef-symbols>symbols()</a> function only allows strings and images,
while the <a class=property data-link-type=propdesc href=#descdef-symbols title=symbols>symbols</a> descriptor of a <a class=css data-link-type=maybe href=#at-ruledef-counter-style>@counter-style</a> rule also allows identifiers.
<h2 data-level=5 id=extending-css2><span class=secno>5 </span><span class=content>
Extending <a class=property data-link-type=propdesc href=http://dev.w3.org/csswg/css-lists-3/#list-style-type title=list-style-type>list-style-type</a>, <span class=css data-link-type=maybe>counter()</span>, and <span class=css data-link-type=maybe>counters()</span></span><a class=section-link href=#extending-css2>§</a></h2>
<p> In CSS Level 2 <a data-biblio-type=normative data-link-type=biblio href=#css21 title=CSS21>[CSS21]</a> the <a class=property data-link-type=propdesc href=http://dev.w3.org/csswg/css-lists-3/#list-style-type title=list-style-type>list-style-type</a> property and the <span class=css data-link-type=maybe>counter()</span> and <span class=css data-link-type=maybe>counters()</span> notations