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<!doctype html>
<html lang="en">
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
<title>CSS Pseudo-Elements Module Level 4</title>
<link href="../default.css" rel="stylesheet" type="text/css">
<link href="../csslogo.ico" rel="shortcut icon" type="image/x-icon">
<link href="http://www.w3.org/StyleSheets/TR/W3C-WD" rel="stylesheet" type="text/css">
<meta content="Bikeshed 1.0.0" name="generator">
</head>
<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/Icons/w3c_home" width="72">
</a>
</p>
<h1 class="p-name no-ref" id="title">CSS Pseudo-Elements Module Level 4</h1>
<h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="content">W3C First Public Working Draft,
<time class="dt-updated" datetime="2015-01-15">15 January 2015</time></span></h2>
<div data-fill-with="spec-metadata">
<dl>
<dt>This version:
<dd><a class="u-url" href="http://www.w3.org/TR/2015/WD-css-pseudo-4-20150115/">http://www.w3.org/TR/2015/WD-css-pseudo-4-20150115/</a>
<dt>Latest version:
<dd><a href="http://www.w3.org/TR/css-pseudo-4/">http://www.w3.org/TR/css-pseudo-4/</a>
<dt>Editor's Draft:
<dd><a href="http://dev.w3.org/csswg/css-pseudo-4/">http://dev.w3.org/csswg/css-pseudo-4/</a>
<dt>Feedback:
<dd><span><a href="mailto:www-style@w3.org?subject=%5Bcss-pseudo%5D%20feedback">www-style@w3.org</a> with subject line “<kbd>[css-pseudo] <var>… message topic …</var></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">Editors:
<dd class="editor p-author h-card vcard"><span class="p-name fn">Daniel Glazman</span> (<span class="p-org org">Disruptive Innovations</span>)
<dd class="editor p-author h-card vcard"><a class="p-name fn u-url url" href="http://fantasai.inkedblade.net/contact">fantasai</a> (<span class="p-org org">Invited Expert</span>)
<dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:stearns@adobe.com">Alan Stearns</a> (<span class="p-org org">Adobe Systems Inc.</span>)
<dt>Issues List:
<dd><span><a href="http://dev.w3.org/csswg/css-pseudo/#issues-index">Tracked in Editor’s Draft</a></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> © 2015 <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 CSS module defines pseudo-elements, abstract elements that represent portions of the CSS render tree that can be selected and styled.</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><em>This section describes the status of this document at the time of
its publication. Other documents may supersede this document. A list of
current W3C publications and the latest revision of this technical report
can be found in the <a href="http://www.w3.org/TR/">W3C technical reports
index at http://www.w3.org/TR/.</a></em>
</p>
<p>This document is a <b>First Public Working Draft</b>.
</p>
<p>Publication as a First Public Working Draft does not imply endorsement by the W3C
Membership. This is a draft document and may be updated, replaced or
obsoleted by other documents at any time. It is inappropriate to cite this
document as other than 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">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-pseudo” in the subject, preferably like this:
“[css-pseudo] <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/2014/Process-20140801/" id="w3c_process_revision">1 August 2014 W3C Process Document</a>.
</p>
<p>
</p></div>
<div data-fill-with="at-risk"></div>
<h2 class="no-num no-toc no-ref heading settled" id="contents"><span class="content">Table of Contents</span></h2>
<div data-fill-with="table-of-contents" role="navigation">
<ul class="toc" role="directory">
<li><a href="#intro"><span class="secno">1</span> <span class="content">Introduction</span></a>
<li><a href="#typographic-pseudos"><span class="secno">2</span> <span class="content">
Typographic Pseudo-elements</span></a>
<ul class="toc">
<li><a href="#first-line-pseudo"><span class="secno">2.1</span> <span class="content">
The ::first-line pseudo-element</span></a>
<ul class="toc">
<li><a href="#first-text-line"><span class="secno">2.1.1</span> <span class="content">
Finding the First Formatted Line</span></a>
<li><a href="#first-line-styling"><span class="secno">2.1.2</span> <span class="content">
Styling the First Line Pseudo-element</span></a>
<li><a href="#first-line-inheritance"><span class="secno">2.1.3</span> <span class="content">
Inheritance and the <span class="css">::first-line</span> Pseudo-element</span></a>
</ul>
<li><a href="#first-letter-pseudo"><span class="secno">2.2</span> <span class="content">
The ::first-letter pseudo-element</span></a>
<ul class="toc">
<li><a href="#application-in-css"><span class="secno">2.2.1</span> <span class="content">
Finding the First Letter</span></a>
<li><a href="#first-letter-styling"><span class="secno">2.2.2</span> <span class="content">
Styling the <span class="css">::first-letter</span> Pseudo-element</span></a>
</ul>
</ul>
<li><a href="#highlight-pseudos"><span class="secno">3</span> <span class="content">
Highlight Pseudo-elements</span></a>
<ul class="toc">
<li><a href="#highlight-selectors"><span class="secno">3.1</span> <span class="content">
Selecting Highlighted Content: the <span class="css">::selection</span>, <span class="css">::spelling-error</span>, and <span class="css">::grammar-error</span> pseudo-elements</span></a>
<li><a href="#highlight-styling"><span class="secno">3.2</span> <span class="content">
Styling Highlights</span></a>
<li><a href="#highlight-bounds"><span class="secno">3.3</span> <span class="content">
Area of a Highlight</span></a>
<li><a href="#highlight-cascade"><span class="secno">3.4</span> <span class="content">
Cascading and Per-Element Highlight Styles</span></a>
<li><a href="#highlight-painting"><span class="secno">3.5</span> <span class="content">
Painting the Highlight</span></a>
<li><a href="#highlight-security"><span class="secno">3.6</span> <span class="content">
Security Considerations</span></a>
</ul>
<li><a href="#treelike"><span class="secno">4</span> <span class="content">
Tree-Abiding Pseudo-elements</span></a>
<ul class="toc">
<li><a href="#generated-content"><span class="secno">4.1</span> <span class="content">
Generated Content Pseudo-elements: <span class="css">::before</span> and <span class="css">::after</span></span></a>
<li><a href="#marker-pseudo"><span class="secno">4.2</span> <span class="content">
List Markers: the <span class="css">::marker</span> pseudo-element</span></a>
<li><a href="#placeholder-pseudo"><span class="secno">4.3</span> <span class="content">
Placeholder Input: the <span class="css">::placeholder</span> pseudo-element</span></a>
</ul>
<li><a href="#interactions"><span class="secno">5</span> <span class="content">
Overlapping Pseudo-element Interactions</span></a>
<li><a href="#cssom"><span class="secno">6</span> <span class="content">
Additions to the CSS Object Model</span></a>
<ul class="toc">
<li><a href="#CSSPseudoElement-interface"><span class="secno">6.1</span> <span class="content">
Interface CSSPseudoElement</span></a>
<li><a href="#CSSPseudoElementList-interface"><span class="secno">6.2</span> <span class="content">
Interface CSSPseudoElementList</span></a>
<li><a href="#window-interface"><span class="secno">6.3</span> <span class="content">
Addition to the <code>window</code> interface</span></a>
</ul>
<li><a href="#acknowledgements"><span class="secno"></span> <span class="content">
Acknowledgements</span></a>
<li><a href="#conformance"><span class="secno"></span> <span class="content">
Conformance</span></a>
<ul class="toc">
<li><a href="#conventions"><span class="secno"></span> <span class="content">
Document conventions</span></a>
<li><a href="#conformance-classes"><span class="secno"></span> <span class="content">
Conformance classes</span></a>
<li><a href="#partial"><span class="secno"></span> <span class="content">
Partial implementations</span></a>
<li><a href="#experimental"><span class="secno"></span> <span class="content">
Experimental implementations</span></a>
<li><a href="#testing"><span class="secno"></span> <span class="content">
Non-experimental implementations</span></a>
</ul>
<li><a href="#index"><span class="secno"></span> <span class="content">Index</span></a>
<ul 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>
</ul>
<li><a href="#references"><span class="secno"></span> <span class="content">References</span></a>
<ul 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>
</ul>
<li><a href="#idl-index"><span class="secno"></span> <span class="content">IDL Index</span></a>
<li><a href="#issues-index"><span class="secno"></span> <span class="content">Issues Index</span></a>
</ul></div>
<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><em>This section is informative.</em></p>
<p><i>Pseudo-elements</i> represent abstract elements of the document
beyond those elements explicitly created by the document language.
Since they are not restricted to fitting into the document tree,
the can be used the select and style portions of the document
that do not necessarily map to the document’s tree structure.
For instance, the <a class="css" data-link-type="maybe" href="#selectordef-first-line">::first-line</a> pseudo-element can
select content on the first formatted line of an element
<em>after</em> text wrapping,
allowing just that line to be styled differently
from the rest of the paragraph.</p>
<p>Each pseudo-element is associated with an <i>originating element</i>
and has syntax of the form <span class="css">::name-of-pseudo</span>.
This module defines the pseudo-elements that exist in CSS
and how they can be styled.
For more information on pseudo-elements in general,
and on their syntax and interaction with other <i>selectors</i>,
see <a data-link-type="biblio" href="#biblio-selectors4">[SELECTORS4]</a>.</p>
<h2 class="heading settled" data-level="2" id="typographic-pseudos"><span class="secno">2. </span><span class="content">
Typographic Pseudo-elements</span><a class="self-link" href="#typographic-pseudos"></a></h2>
<h3 class="heading settled" data-level="2.1" id="first-line-pseudo"><span class="secno">2.1. </span><span class="content">
The ::first-line pseudo-element</span><a class="self-link" href="#first-line-pseudo"></a></h3>
<p>The <dfn class="css" data-dfn-type="selector" data-export="" id="selectordef-first-line">::first-line<a class="self-link" href="#selectordef-first-line"></a></dfn> pseudo-element describes the contents of
the <i>first formatted line</i> of its <i>originating element</i>.</p>
<div class="example" id="example-209e7dc9"><a class="self-link" href="#example-209e7dc9"></a>
The rule below means
“change the letters of the first line of every <code>p</code> element to uppercase”:
<pre>p::first-line { text-transform: uppercase }</pre>
<p>The selector <span class="css">p::first-line</span>
does not match any real document element.
It does match a pseudo-element that conforming user agents
will insert at the beginning of every <code>p</code> element.</p>
</div>
<p class="note" role="note">Note: Note that the length of the first line depends on a number of factors,
including the width of the page, the font size, etc.</p>
<div class="example" id="example-a0a743c3"><a class="self-link" href="#example-a0a743c3"></a>
For example, given an ordinary HTML <a data-link-type="biblio" href="#biblio-html5">[HTML5]</a> paragraph such as:
<pre><P>This is a somewhat long HTML
paragraph that will be broken into several
lines. The first line will be identified
by a fictional tag sequence. The other lines
will be treated as ordinary lines in the
paragraph.</P>
</pre>
<p>The lines might be broken as follows:</p>
<pre>THIS IS A SOMEWHAT LONG HTML PARAGRAPH THAT
will be broken into several lines. The first
line will be identified by a fictional tag
sequence. The other lines will be treated as
ordinary lines in the paragraph.
</pre>
<p>This paragraph might be “rewritten” by user agents
to include a <dfn data-dfn-type="dfn" data-noexport="" id="fictional-tag-sequence">fictional tag sequence<a class="self-link" href="#fictional-tag-sequence"></a></dfn> to represent <a class="css" data-link-type="maybe" href="#selectordef-first-line">::first-line</a>.
This <i>fictional tag sequence</i> helps to show how properties are inherited.</p>
<pre><P><b><P::first-line></b> This is a somewhat long HTML
paragraph that <b></P::first-line></b> will be broken into several
lines. The first line will be identified
by a fictional tag sequence. The other lines
will be treated as ordinary lines in the
paragraph.</P>
</pre>
</div>
<p>If a pseudo-element breaks up a real element,
the desired effect can often be described by a <i>fictional tag sequence</i>
that closes and then re-opens the element.</p>
<div class="example" id="example-bac4a557"><a class="self-link" href="#example-bac4a557"></a>
Thus, if we mark up the previous paragraph with a <code>span</code>
element encompassing the first sentence:
<pre><P><b><SPAN class="test"></b> This is a somewhat long HTML
paragraph that will be broken into several
lines.<b></SPAN></b> The first line will be identified
by a fictional tag sequence. The other lines
will be treated as ordinary lines in the
paragraph.</P>
</pre>
<p>the user agent could simulate start and end tags for <code>span</code>
when inserting the <i>fictional tag sequence</i> for <a class="css" data-link-type="maybe" href="#selectordef-first-line">::first-line</a>
to get the correct inheritance behavior.</p>
<pre><P><P::first-line><b><SPAN class="test"></b> This is a somewhat long HTML
paragraph that will <b></SPAN></b></P::first-line><b><SPAN class="test"></b> be broken into several
lines.<b></SPAN></b> The first line will be identified
by a fictional tag sequence. The other lines
will be treated as ordinary lines in the
paragraph.</P>
</pre>
</div>
<h4 class="heading settled" data-level="2.1.1" id="first-text-line"><span class="secno">2.1.1. </span><span class="content">
Finding the First Formatted Line</span><a class="self-link" href="#first-text-line"></a></h4>
<p>In CSS, the <a class="css" data-link-type="maybe" href="#selectordef-first-line">::first-line</a> pseudo-element
can only have an effect when attached to a <i>block container</i>.
The <dfn data-dfn-type="dfn" data-noexport="" id="first-formatted-line">first formatted line<a class="self-link" href="#first-formatted-line"></a></dfn> of an element
must occur inside a block-level descendant in the same flow
(i.e., a block-level descendant that is not out-of-flow due to floating or positioning).</p>
<div class="example" id="example-7018f958"><a class="self-link" href="#example-7018f958"></a>
For example, the first line of the <code>DIV</code> in <code><DIV><P>This line...</P></DIV></code>
is the first line of the <code>P</code>
(assuming that both <code>P</code> and <code>DIV</code> are blocks).
</div>
<p>The first line of a table-cell or inline-block
cannot be the first formatted line of an ancestor element.
Thus, in <code><DIV><P STYLE="display: inline-block">Hello<BR>Goodbye</P> etcetera</DIV></code>
the first formatted line of the <code>DIV</code> is not the line "Hello".</p>
<p class="note" role="note">Note: Note that the first line of the <code>p</code> in this fragment:
<code><p><br>First...</code>
doesn’t contain any letters (assuming the default style for <code>br</code>).
The word "First" is not on the first formatted line.</p>
<p>A user agent must act as if the fictional start tags of a <a class="css" data-link-type="maybe" href="#selectordef-first-line">::first-line</a> pseudo-element
were nested just inside the innermost enclosing block-level element.</p>
<div class="example" id="example-8dd21d66"><a class="self-link" href="#example-8dd21d66"></a>
For example, the <i>fictional tag sequence</i> for
<pre><DIV>
<P>First paragraph</P>
<P>Second paragraph</P>
</DIV>
</pre>
<p>is</p>
<pre><DIV>
<P><DIV::first-line><P::first-line>First paragraph</P::first-line></DIV::first-line></P>
<P><P::first-line>Second paragraph</P::first-line></P>
</DIV>
</pre>
</div>
<h4 class="heading settled" data-level="2.1.2" id="first-line-styling"><span class="secno">2.1.2. </span><span class="content">
Styling the First Line Pseudo-element</span><a class="self-link" href="#first-line-styling"></a></h4>
<p>The <a class="css" data-link-type="maybe" href="#selectordef-first-line">::first-line</a> pseudo-element’s generated box
behaves similar to that of an inline-level element, but with certain restrictions.
The following CSS properties apply to a <a class="css" data-link-type="maybe" href="#selectordef-first-line">::first-line</a> pseudo-element:</p>
<ul>
<li>all font properties (see <a data-link-type="biblio" href="#biblio-css3-fonts">[CSS3-FONTS]</a>)
<li>the <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-color/#color0">color</a> and <a class="property" data-link-type="propdesc" href="http://dev.w3.org/csswg/css-color-4/#propdef-opacity">opacity</a> properties (see <a data-link-type="biblio" href="#biblio-css3color">[CSS3COLOR]</a>)
<li>all background properties (see <a data-link-type="biblio" href="#biblio-css3bg">[CSS3BG]</a>)
<li>any typesetting properties that apply to inline elements (see <a data-link-type="biblio" href="#biblio-css3text">[CSS3TEXT]</a>)
<li>all text decoration properties (see <a data-link-type="biblio" href="#biblio-css3-text-decor">[CSS3-TEXT-DECOR]</a>)
<li>any inline layout properties that apply to inline elements (see <a data-link-type="biblio" href="#biblio-css3line">[CSS3LINE]</a>)
<li>any other properties defined to apply to <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a>
by their respective specifications
</ul>
User agents may apply other properties as well.
<h4 class="heading settled" data-level="2.1.3" id="first-line-inheritance"><span class="secno">2.1.3. </span><span class="content">
Inheritance and the <a class="css" data-link-type="maybe" href="#selectordef-first-line">::first-line</a> Pseudo-element</span><a class="self-link" href="#first-line-inheritance"></a></h4>
<p>During CSS inheritance, the portion of a child element that occurs on the first line
only inherits properties applicable to the <a class="css" data-link-type="maybe" href="#selectordef-first-line">::first-line</a> pseudo-element
from the <a class="css" data-link-type="maybe" href="#selectordef-first-line">::first-line</a> pseudo-element.
For all other properties inheritence is
from the non-pseudo-element parent of the first line pseudo element.
(The portion of a child element that does not occur on the first line
always inherits from the parent of that child.)</p>
<h3 class="heading settled" data-level="2.2" id="first-letter-pseudo"><span class="secno">2.2. </span><span class="content">
The ::first-letter pseudo-element</span><a class="self-link" href="#first-letter-pseudo"></a></h3>
<p>The <dfn class="css" data-dfn-type="selector" data-export="" id="selectordef-first-letter">::first-letter<a class="self-link" href="#selectordef-first-letter"></a></dfn> pseudo-element represents
the first <i>typographic letter unit</i> <a data-link-type="biblio" href="#biblio-css3text">[CSS3TEXT]</a>
on the <i>first formatted line</i> of its <i>originating element</i>,
if it is not preceded by any other content
(such as images or inline tables) on its line.
The <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a> pseudo-element can be used
to create “initial caps” and “drop caps”,
which are common typographic effects.</p>
<div class="example" id="example-e0bd2aa2"><a class="self-link" href="#example-e0bd2aa2"></a>
For example, the following rule creates a 2-line drop-letter
on every paragraph following a level-2 header,
using the <a class="property" data-link-type="propdesc">initial-letter</a> property defined in <a data-link-type="biblio" href="#biblio-css3line">[CSS3LINE]</a>:
<pre>h2 + p::first-letter { initial-letter: 2; }
</pre>
</div>
<p>Punctuation (i.e, characters that belong to the Punctuation (<code>P*</code>) <i>Unicode general category</i> <a data-link-type="biblio" href="#biblio-uax44">[UAX44]</a>)
that precedes or follows the first <i>typographic letter unit</i> must also be included
in the <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a> pseudo-element.</p>
<div class="figure">
<img alt="Quotes that precede the first letter should be included." src="http://www.w3.org/TR/selectors/first-letter2.png">
</div>
<p>As explained in <a data-link-type="biblio" href="#biblio-css3text">[CSS3TEXT]</a>,
a <i>typographic letter unit</i> can include more than one Unicode codepoint.
For example, combining characters must be kept with their base character.
Also, languages may have additional rules
about how to treat certain letter combinations.
In Dutch, for example, if the letter combination "ij" appears at the beginning of an element,
both letters should be considered within the <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a> pseudo-element. <a data-link-type="biblio" href="#biblio-uax29">[UAX29]</a>
The UA should tailor its definition of <i>typographic letter unit</i>
to reflect the first-letter traditions of the <i>originating element</i>’s content language.</p>
<p class="issue" id="issue-703eb1d7"><a class="self-link" href="#issue-703eb1d7"></a>This is actually a problem in cases where the originating element is an ancestor
with a different content. What <em>should</em> we say here?</p>
<p class="note" role="note">Note: Note that the first <i>typographic letter unit</i> may in fact
be a digit, e.g., the “6” in “67 million dollars is a lot of money.”</p>
<p>If the characters that would form the <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a>
are not in the same element, such as "‘<code class="css">T" in <code><p>'<em>T...</code>,
the user agent may create a <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a> pseudo-element
from one of the elements, both elements, or simply not create a pseudo-element.</code>
Additionally, if the first letter(s) of the block
are not at the start of the line (for example due to bidirectional reordering),
then the user agent need not create the pseudo-element(s).</p>
<p>The <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a> pseudo-element is contained within any <a class="css" data-link-type="maybe" href="#selectordef-first-line">::first-line</a>
pseudo-elements, and thus inherits from <a class="css" data-link-type="maybe" href="#selectordef-first-line">::first-line</a>.</p>
<h4 class="heading settled" data-level="2.2.1" id="application-in-css"><span class="secno">2.2.1. </span><span class="content">
Finding the First Letter</span><a class="self-link" href="#application-in-css"></a></h4>
<p>The first letter must occur on the <i>first formatted line</i>.
For example, in this HTML fragment: <code><p><br>First...</code>
the first line doesn’t contain any letters
and <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a> doesn’t match anything.
In particular, it does not match the “F” of “First”.</p>
<p>In CSS, the <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a> pseudo-element
only applies to block containers.
<span class="note" role="note">A future version of this specification
may allow this pseudo-element to apply to more display types.</span>
The <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a> pseudo-element can be used
with all such elements that contain text,
or that have a descendant in the same flow that contains text.
A user agent should act as if the fictional start tag
of the ::first-letter pseudo-element
is just before the first text of the element,
even if that first text is in a descendant.</p>
<div class="example" id="example-7f507aaf"><a class="self-link" href="#example-7f507aaf"></a>
Example:
The <i>fictional tag sequence</i> for this HTML fragment:
<pre><div>
<p>The first text.
</pre>
<p>is:</p>
<pre><div>
<p><div::first-letter><p::first-letter>T</...></...>he first text.
</pre>
</div>
<p>In CSS the first letter of a table-cell or inline-block
cannot be the first letter of an ancestor element.
Thus, in <code><DIV><P STYLE="display: inline-block">Hello<BR>Goodbye</P> etcetera</DIV></code>
the first letter of the <code>DIV</code> is not the letter "H".
In fact, the <code>DIV</code> doesn’t have a first letter.
If an element is a list item (<a class="css" data-link-type="propdesc" href="http://www.w3.org/TR/CSS21/visuren.html#propdef-display">display: list-item</a>),
the <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a> applies
to the first letter in the principal box <em>after</em> the marker.
User-Agents may ignore <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a>
on list items with <a class="css" data-link-type="propdesc" href="http://www.w3.org/TR/css3-lists/#propdef-list-style-position">list-style-position: inside</a>.
If an element has <a class="css" data-link-type="maybe" href="#selectordef-before">::before</a> or <a class="css" data-link-type="maybe" href="#selectordef-after">::after</a> content,
the <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a> applies to the first letter of the
element <em>including</em> that content.</p>
<div class="example" id="example-c5754cfa"><a class="self-link" href="#example-c5754cfa"></a>
Example:
After the rule <span class="css">p::before {content: "Note: "}</span>, the
selector <span class="css">p::first-letter</span> matches the "N" of "Note".
</div>
<h4 class="heading settled" data-level="2.2.2" id="first-letter-styling"><span class="secno">2.2.2. </span><span class="content">
Styling the <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a> Pseudo-element</span><a class="self-link" href="#first-letter-styling"></a></h4>
<p>In CSS a ::first-letter pseudo-element is similar to an inline-level element
if its <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/CSS21/visuren.html#propdef-float">float</a> property is <a class="css" data-link-type="maybe" href="http://dev.w3.org/csswg/css-page-floats/#valdef-float-none">none</a>;
otherwise, it is similar to a floated element.
The following properties that apply to <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a> pseudo-elements:</p>
<ul>
<li>all font properties (see <a data-link-type="biblio" href="#biblio-css3-fonts">[CSS3-FONTS]</a>)
<li>the <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-color/#color0">color</a> and <a class="property" data-link-type="propdesc" href="http://dev.w3.org/csswg/css-color-4/#propdef-opacity">opacity</a> properties (see <a data-link-type="biblio" href="#biblio-css3color">[CSS3COLOR]</a>)
<li>all background properties (see <a data-link-type="biblio" href="#biblio-css3bg">[CSS3BG]</a>)
<li>any typesetting properties that apply to inline elements (see <a data-link-type="biblio" href="#biblio-css3text">[CSS3TEXT]</a>)
<li>all text decoration properties (see <a data-link-type="biblio" href="#biblio-css3-text-decor">[CSS3-TEXT-DECOR]</a>)
<li>any inline layout properties that apply to inline elements (see <a data-link-type="biblio" href="#biblio-css3line">[CSS3LINE]</a>)
<li>margin and padding properties (see <a data-link-type="biblio" href="#biblio-css21">[CSS21]</a>)
<li>border properties and <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-background/#box-shadow">box-shadow</a> (see <a data-link-type="biblio" href="#biblio-css3bg">[CSS3BG]</a>)
<li>any other properties defined to apply to <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a>
by their respective specifications
</ul>
<p>User agents may apply other properties as well.</p>
<p class="note" role="note">Note: In previous levels of CSS,
User Agents were allowed to choose a line height, width and height based on the shape of the letter,
approximate font sizes,
or to take the glyph outline into account when formatting.
This possibility has been intentionally removed,
as it proved to be a poor solution for the intended use case (Drop Caps),
yet caused interoperability problems.</p>
<div class="example" id="example-845918ec"><a class="self-link" href="#example-845918ec"></a>
Example:
This CSS and HTML example shows a possible rendering of an initial cap.
Note that the fictional start tag of the first letter
is inside the <span>span</span>,
and thus the font weight of the first letter is normal,
not bold as the <span>span</span>:
<pre>p { line-height: 1.1 }
p::first-letter { font-size: 3em; font-weight: normal }
span { font-weight: bold }
...
<p><span>Het hemelsche</span> gerecht heeft zich ten lange lesten<br>
Erbarremt over my en mijn benaeuwde vesten<br>
En arme burgery, en op mijn volcx gebed<br>
En dagelix geschrey de bange stad ontzet.
</pre>
<div class="figure">
<img alt="Image illustrating the ::first-letter pseudo-element" src="http://www.w3.org/TR/selectors/initial-cap.png">
</div>
</div>
<div class="example" id="example-e4341976"><a class="self-link" href="#example-e4341976"></a>
The following CSS will make a drop cap initial letter span about two lines:
<pre><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
<HEAD>
<TITLE>Drop cap initial letter</TITLE>
<STYLE type="text/css">
P { font-size: 12pt; line-height: 1.2 }
P::first-letter { font-size: 200%; font-weight: bold; float: left }
SPAN { text-transform: uppercase }
</STYLE>
</HEAD>
<BODY>
<P><SPAN>The first</SPAN> few words of an article
in The Economist.</P>
</BODY>
</HTML>
</pre>
<p>This example might be formatted as follows:</p>
<div class="figure">
<img alt="Image illustrating the combined effect of the ::first-letter
and ::first-line pseudo-elements" src="http://www.w3.org/TR/selectors/first-letter.png">
</div>
<p>The <i>fictional tag sequence</i> is:</p>
<pre><P>
<SPAN>
<P::first-letter>
T
</P::first-letter>he first
</SPAN>
few words of an article in the Economist.
</P>
</pre>
<p>Note that the <a class="css" data-link-type="maybe" href="#selectordef-first-letter">::first-letter</a> pseudo-element tags abut the
content (i.e., the initial character), while the ::first-line
pseudo-element start tag is inserted right after the start tag of the
block element.</p>
</div>
<h2 class="heading settled" data-level="3" id="highlight-pseudos"><span class="secno">3. </span><span class="content">
Highlight Pseudo-elements</span><a class="self-link" href="#highlight-pseudos"></a></h2>
<h3 class="heading settled" data-level="3.1" id="highlight-selectors"><span class="secno">3.1. </span><span class="content">
Selecting Highlighted Content: the <a class="css" data-link-type="maybe" href="#selectordef-selection">::selection</a>, <a class="css" data-link-type="maybe" href="#selectordef-spelling-error">::spelling-error</a>, and <a class="css" data-link-type="maybe" href="#selectordef-grammar-error">::grammar-error</a> pseudo-elements</span><a class="self-link" href="#highlight-selectors"></a></h3>
<p>The <dfn data-dfn-type="dfn" data-noexport="" id="highlight-pseudo_elements">highlight pseudo-elements<a class="self-link" href="#highlight-pseudo_elements"></a></dfn>
represent portions of a document that have been highlighted in some way.</p>
<dl>
<dt><dfn class="css" data-dfn-type="selector" data-export="" id="selectordef-selection">::selection<a class="self-link" href="#selectordef-selection"></a></dfn>
<dd>
The <a class="css" data-link-type="selector" href="#selectordef-selection">::selection</a> pseudo-element represents
the portion of a document that has been highlighted by the user.
This also applies, for example, to selected text within an editable text field.
<p class="issue" id="issue-43364a12"><a class="self-link" href="#issue-43364a12"></a>Active vs. inactive selections are often styled differently. Currently no way to distinguish.</p>
<dt><dfn class="css" data-dfn-type="selector" data-export="" id="selectordef-spelling-error">::spelling-error<a class="self-link" href="#selectordef-spelling-error"></a></dfn>
<dd>
The <a class="css" data-link-type="selector" href="#selectordef-spelling-error">::spelling-error</a> pseudo-element represents
a portion of text that has been flagged by the user agent as misspelled.
<dt><dfn class="css" data-dfn-type="selector" data-export="" id="selectordef-grammar-error">::grammar-error<a class="self-link" href="#selectordef-grammar-error"></a></dfn>
<dd>
The <a class="css" data-link-type="selector" href="#selectordef-grammar-error">::grammar-error</a> pseudo-element represents
a portion of text that has been flagged by the user agent as grammatically incorrect.
</dl>
<p class="note" role="note">Note: A future level of CSS may introduce ways to create
custom highlight pseudo-elements.</p>
<h3 class="heading settled" data-level="3.2" id="highlight-styling"><span class="secno">3.2. </span><span class="content">
Styling Highlights</span><a class="self-link" href="#highlight-styling"></a></h3>
<p>The following properties apply to the <a data-link-type="dfn" href="#highlight-pseudo_elements">highlight pseudo-elements</a>:</p>
<ul>
<li><a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-color/#color0">color</a>
<li><a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-background/#background-color">background-color</a>
<li><a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-ui/#propdef-cursor">cursor</a>
<li><a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-ui/#propdef-outline">outline</a> and its longhands
<li><a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css-text-decor-3/#text-decoration">text-decoration</a> and its associated properties
<li><a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css-text-decor-3/#text-emphasis-color">text-emphasis-color</a>
<li><a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css-text-decor-3/#text-shadow">text-shadow</a>
</ul>
<p class="issue" id="issue-7be57116"><a class="self-link" href="#issue-7be57116"></a>Are there any other properties that should be included here?
[Caret-color should be added once we have it.]</p>
<p class="note" role="note">Note: Historically (and at the time of writing)
only <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-color/#color0">color</a> and <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-background/#background-color">background-color</a> have been interoperably supported.</p>
<p>If <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-color/#color0">color</a> is not specified, the text (and text decoration)'s
unselected color must be used for the highlight.
(As usual, the initial <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-background/#background-color">background-color</a> is <a class="css" data-link-type="maybe" href="http://dev.w3.org/csswg/css-color-4/#valdef-color-transparent">transparent</a>.)
Issue: Can we reuse <span class="css">currentColor</span> for this, now that it computes to itself?</p>
<p>The UA should use the OS-default highlight colors
when neither <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-color/#color0">color</a> nor <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-background/#background-color">background-color</a> has been specified by the author.</p>
<p class="note" role="note">Note: This paired-cascading behavior
does not allow <a href="http://lists.w3.org/Archives/Public/www-style/2008Oct/0268.html">using the normal cascade</a>
to represent the OS default selection colors.
However it has been interoperably implemented in browsers
and is thus probably a Web-compatibility requirement.</p>
<p>The <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-color/#color0">color</a> property specifies the color of both the text
and all line decorations (underline, overline, line-through)
applied to the text.
Note: Because <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css-text-decor-3/#text-emphasis-color">text-emphasis-color</a> defaults to <span class="css">currrentColor</span>,
it will by default also set the color of the the emphasis marks.</p>
<h3 class="heading settled" data-level="3.3" id="highlight-bounds"><span class="secno">3.3. </span><span class="content">
Area of a Highlight</span><a class="self-link" href="#highlight-bounds"></a></h3>
<p>For each instance of highlighting
there exists a <dfn data-dfn-type="dfn" data-noexport="" id="root-highlight-overlay">root highlight overlay<a class="self-link" href="#root-highlight-overlay"></a></dfn>
which is a tesselated overlay
over the entire tree,
the actively-highlighted portions of which are represented
by the corresponding <a data-link-type="dfn" href="#highlight-pseudo_elements">highlight pseudo-element</a>.
The <a class="css" data-link-type="maybe" href="#selectordef-selection">::selection</a> overlay is drawn
over the <a class="css" data-link-type="maybe" href="#selectordef-spelling-error">::spelling-error</a> overlay
which is drawn over the <a class="css" data-link-type="maybe" href="#selectordef-grammar-error">::grammar-error</a> overlay.
</p>
<p>Each box owns a piece of the overlay corresponding to any text or replaced content
directly contained by the box.</p>
<ul>
<li>
For text, the corresponding overlay must cover at least the entire em box
and may extend further above/below the em box to the line box edges.
Spacing between two characters may also be part of the overlay,
in which case it belongs to the innermost element that contains both characters
and is selected when both characters are selected.
<li>
For replaced content, the associated overlay must cover at least the entire replaced object,
and may extend outward to include the element’s entire content box.
<li>
The overlay may also include other other areas within the border-box of an element;
in this case, those areas belong to the innermost such element that contains the area.
</ul>
<p class="issue" id="issue-b6466947"><a class="self-link" href="#issue-b6466947"></a>See
<a href="http://lists.w3.org/Archives/Public/www-style/2008Nov/0022.html">F2F minutes</a>,
<a href="http://lists.w3.org/Archives/Public/www-style/2008Oct/0268.html">dbaron’s message</a>,
<a href="http://lists.w3.org/Archives/Public/www-style/2010May/0247.html">Daniel’s thread</a>,
<a href="http://lists.w3.org/Archives/Public/www-style/2010May/0261.html">Gecko notes</a>,
<a href="http://lists.w3.org/Archives/Public/www-style/2010May/0366.html">Opera notes</a>,
<a href="http://lists.w3.org/Archives/Public/www-style/2010May/0280.html">Webkit notes</a></p>
<p class="issue" id="issue-271a1b90"><a class="self-link" href="#issue-271a1b90"></a>Not sure if this is the correct way of describing the way things work.</p>
<h3 class="heading settled" data-level="3.4" id="highlight-cascade"><span class="secno">3.4. </span><span class="content">
Cascading and Per-Element Highlight Styles</span><a class="self-link" href="#highlight-cascade"></a></h3>
<p>Each element draws its own portion of the <a data-link-type="dfn" href="#root-highlight-overlay">root highlight overlay</a>,
which receives the styles specified by the <a data-link-type="dfn" href="#highlight-pseudo_elements">highlight pseudo-element</a> styles
for which it or one of its ancestors is the <i>originating element</i>.
When multiple styles conflict,
the winning style is the one belonging to the innermost element
after cascading.</p>
<div class="example" id="example-7d56356a"><a class="self-link" href="#example-7d56356a"></a>
For example, if the following rules were applied:
<pre>p::selection { background: green; color: yellow; }
em::selection { color: orange; }
</pre>
<p>to the following markup:</p>
<pre><p>Highlight this <em>and this</em>.</p>
</pre>
<p>The highlight would be green throughout,
with a yellow text outside the <code><em></code> element
and a orange text inside it.</p>
</div>
<p class="issue" id="issue-ff621186"><a class="self-link" href="#issue-ff621186"></a>This could alternately be described in terms of inheritance.
The observable differences would be in how <a class="css" data-link-type="maybe" href="http://www.w3.org/TR/css-cascade-3/#valdef-all-inherit">inherit</a> and <a class="css" data-link-type="maybe" href="http://dev.w3.org/csswg/css-cascade-4/#valdef-all-unset">unset</a> behave.
Should it inherit from the parent <a class="css" data-link-type="maybe" href="#selectordef-selection">::selection</a>
or the <i>originating element</i>?
Opera does the former, Gecko/Blink the latter.</p>
<p class="advisement">
Authors wanting multiple selections styles should use
<strong><span class="css">:root::selection</span></strong>
for their document-wide selection style,
since this will allow clean overriding in descendants.
(<a class="css" data-link-type="maybe" href="#selectordef-selection">::selection</a> alone would apply to every element in the tree,
overriding the more specific styles of any ancestors.)
</p>
<h3 class="heading settled" data-level="3.5" id="highlight-painting"><span class="secno">3.5. </span><span class="content">
Painting the Highlight</span><a class="self-link" href="#highlight-painting"></a></h3>
<p>The <a class="css" data-link-type="maybe" href="#selectordef-selection">::selection</a> pseudo element draws its background
over the selected portion of the element,
immediately below any positioned descendants
(i.e. just before step 8 in <a href="http://www.w3.org/TR/CSS21/zindex.html">CSS2.1§E.2</a>).
It also suppresses the drawing of any selected text
(and any text decorations applied to that text)
and instead redraws that text
(and its decorations)
over that background
using the specified <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-color/#color0">color</a>.</p>
<p class="issue" id="issue-b85c3e18"><a class="self-link" href="#issue-b85c3e18"></a>What should happen with text shadows?
Drawing them in their original color is disconcerting if that color is not a shade of gray.</p>
<p>For non-replaced content, the UA must honor the <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-color/#color0">color</a> and <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-background/#background-color">background-color</a>
(including their alpha channels) as specified.
However, for replaced content, the UA should create a semi-transparent wash
to coat the content so that it can show through the selection.
This wash should be of the specified <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-background/#background-color">background-color</a> if that is not <a class="css" data-link-type="maybe" href="http://dev.w3.org/csswg/css-color-4/#valdef-color-transparent">transparent</a>,
else the specified <a class="property" data-link-type="propdesc" href="http://www.w3.org/TR/css3-color/#color0">color</a>;
however the UA may adjust the alpha channel if it is opaque.</p>
<h3 class="heading settled" data-level="3.6" id="highlight-security"><span class="secno">3.6. </span><span class="content">
Security Considerations</span><a class="self-link" href="#highlight-security"></a></h3>
<p>Because the styling of spelling and grammar errors
can leak information about the contents of a user’s dictionary
(which can include the user’s name and even includes the contents of his/her address book!)
UAs that implement <a class="css" data-link-type="maybe" href="#selectordef-spelling-error">::spelling-error</a> and <a class="css" data-link-type="maybe" href="#selectordef-grammar-error">::grammar-error</a>
must prevent pages from being able to read
the styling of such highlighted segments.</p>
<h2 class="heading settled" data-level="4" id="treelike"><span class="secno">4. </span><span class="content">
Tree-Abiding Pseudo-elements</span><a class="self-link" href="#treelike"></a></h2>
<p>These pseudo-elements always fit within the box tree.</p>
<h3 class="heading settled" data-level="4.1" id="generated-content"><span class="secno">4.1. </span><span class="content">
Generated Content Pseudo-elements: <a class="css" data-link-type="maybe" href="#selectordef-before">::before</a> and <a class="css" data-link-type="maybe" href="#selectordef-after">::after</a></span><a class="self-link" href="#generated-content"></a></h3>
<p>When their computed <a class="property" data-link-type="propdesc" href="http://dev.w3.org/csswg/css-content-3/#propdef-content">content</a> value is not <a class="css" data-link-type="maybe" href="http://dev.w3.org/csswg/css-content-3/#valdef-content-none">none</a>,
these pseudo-elements generate boxes