W3C

CSS Generated Content Module Level 3

Editor's Draft 3 February 2014

This version:
http://dev.w3.org/csswg/css3-content/
Latest version:
http://www.w3.org/TR/css3-content/
Previous versions:
http://www.w3.org/TR/2003/WD-css3-content-20030514/
Feedback:
www-style@w3.org with subject line “[css-content] … message topic …” (archives)
Editors:
Håkon Wium Lie, Opera Software
Elika J. Etemad, W3C Invited Expert
Ian Hickson

, Opera Software


Obsoletion Notice

This specification is not being actively maintained, and should not be used as a guide for implementations. It may be revived in the future, but for now should be considered obsolete.
If you have questions or comments on this specification, please send an email to the CSS Working Group's mailing list at www-style@w3.org. (Before sending mail for the first time, you have to subscribe at http://lists.w3.org/Archives/Public/www-style/.)

Abstract

This CSS3 Module describes how to insert and move content around a document, in order to create footnotes, running headers, and other generated content effects.

Status of this document

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.

The (archived) public mailing list www-style@w3.org (see instructions) is preferred for discussion of this specification. When sending e-mail, please put the text “css3-content” in the subject, preferably like this: “[css3-content] …summary of comment…

This document was produced by the CSS Working Group (part of the Style Activity).

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures 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 Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

Table of contents

1. Introduction

In some cases, authors may want user agents to render content that does not come from the document tree. One familiar example of this is numbered headings; the author does not want to mark the numbers up explicitly, he or she wants the user agent to generate them automatically. Counters and markers are used to achieve these effects.

INSERT EXAMPLE HERE

Similarly, authors may want the user agent to insert the word "Figure" before the caption of a figure, or "Chapter 7" on a line before the seventh chapter title.

figure > caption::before { content: "Figure: "; }
chapter:nth-child(7) > title::before { content: "Chapter 7\A"; }

The last example could also be written in a more generic way using counters:

chapter { counter-increment: chapter; }
chapter > title::before { content: "Chapter " counter(chapter) "\A"; }

Another common effect is replacing elements with images or other multimedia content. Since not all user agents support all multimedia formats, fallbacks may have to be provided.

/* Replace <logo> elements with the site's logo, using a format
 * supported by the UA */
logo { content: url(logo.mov), url(logo.mng), url(logo.png), none; }

/* Replace <figure> elements with the referenced document, or,
 * failing that, with either the contents of the alt attribute or the
 * contents of the element itself if there is no alt attribute */
figure[alt] { content: attr(href, url), attr(alt); }
figure:not([alt]) { content: attr(href, url), contents; }

Another effect commonly requested by authors is that of line numbering. This module introduces the ‘::line-marker’ pseudo-element that is attached to the front of every line box, which can be used for this purpose.

pre { counter-reset: line; }
pre::line-marker { counter-increment: line; content: counter(line) "."; }

This pseudo-element can also be used to simulate the indentation style found in e-mail communication:

blockquote { margin: 0; padding: 0 0 0 2em; } 
blockquote > blockquote { margin-left: -1em; }
blockquote::line-marker { width: 2em; text-align: left; content: ">"; }

Generated content based on the cite and datetime attributes can create introductions or citations on the fly as well.

2. Terminology

This module introduces several pseudo-elements and allows them to nest in certain predefined ways. In order to explain the relationships between these nested pseudo-elements, three new terms have been coined.

originating element
A pseudo-element's originating element is the element to which it is associated. e.g. the originating element of the pseudo-element matched by ‘::before’ is the element to which it is attached. Note that an element never has a originating element, and a pseudo-element always has exactly one. This term is sometimes shortened to "superior".

3. Pseudo-elements

At the heart of generated content lies pseudo-elements. Pseudo-elements create abstractions about the document tree beyond those specified by the document language. For instance, document languages do not offer mechanisms to access the first letter or first line of an element's content. CSS pseudo-elements allow style sheet designers to refer to this otherwise inaccessible information. Pseudo-elements also provide style sheet designers a way to assign style to content that does not exist in the source document. Pseudo elements are defined in the [SELECT] specification.

3.1. Inserting content into an element: the ‘::before’ and ‘::after’ pseudo-elements

The ‘::before’ and ‘::after’ pseudo-elements are used to insert content immediately before and immediately after the content of an element (or other pseudo-element). The ‘content’ propety is used to specify the content to insert.

For example, the following rule replaces the content of <abbr> elements with the contents of the element's title attribute:

abbr { content: attr(title); }

The following rule inserts the string "Note: " before the content of every P element whose "class" attribute has the value "note":

P.note:before { content: "Note: " }

The formatting objects (e.g., boxes) generated by an element include generated content. So, for example, changing the above style sheet to:

P.note:before { content: "Note: " }
P.note        { border: solid green }

...would cause a solid green border to be rendered around the entire paragraph, including the initial string.

The ‘::before’ and ‘::after’ pseudo-elements inherit any inheritable properties from their originating element.

For a ‘::before’ or ‘::after’ pseudo-element to be generated, the pseudo-element must not have its ‘content’ property set to ‘inhibit’ or its ‘display’ property set to ‘none’. Note that for ‘::before’ and ‘::after’ pseudo-elements, the initial value of ‘content’ computes to ‘inhibit’.

Using a ‘::before’ pseudo-element in the context of the anonymous table elements works exactly as if an actual element had been introduced. For example:

.example::before { content: "D" }
<table>
 <tr>
  <td>A</td> <td>B</td> <td>C</td>
 </tr>
 <tr class="example">
             <td>E</td> <td>F</td>
 </tr>
</table>

An anonymous table cell box is generated around the ‘::before’ content in this case, resulting in a 3×2 table.

3.2. Block markers: The ‘::marker’ pseudo-element

For a ‘::marker’ pseudo-element to be generated, its superior parent must have a computed ‘display’ value of ‘list-item’.

For further details on the rendering model for list markers, see the CSS3 Lists module.

3.3. Line markers: The ‘::line-marker’ pseudo-element

The ‘::line-marker’ pseudo-element is positioned in exactly the same way as the ‘::marker’ pseudo-element, but appears on every line, not just the first.

Line boxes are responsible for generating ‘::line-marker’ pseudo-elements. For each line, one such marker is created for every block ancestor in the current block formatting context. [!CSS21] In addition, for the ‘::line-marker’ pseudo-element to be created, its ‘content’ property must have a computed value other than ‘none’ or ‘inhibit’.

4. Specifying quotes with the quotes property

Name: quotes
Value: foo | bar
Initial: text
Applies To: all elements
Inherited: no
Percentages: N/A
Media: visual
Computed value: specified value

This property specifies quotation marks for any number of embedded quotations. Values have the following meanings:

none
The ‘open-quote’ and ‘close-quote’ values of the ‘content’ property produce no quotations marks, as if they were ‘no-open-quote’ and ‘no-close-quote’ respectively.
[ <string> <string> ]+
Values for the ‘open-quote’ and ‘close-quote’ values of the ‘content’ property are taken from this list of pairs of quotation marks (opening and closing). The first (leftmost) pair represents the outermost level of quotation, the second pair the first level of embedding, etc. The user agent must apply the appropriate pair of quotation marks according to the level of embedding.

For example, applying the following style sheet:

/* Specify pairs of quotes for two levels in two languages */
:lang(en) > q { quotes: '"' '"' "'" "'" }
:lang(no) > q { quotes: "+" ";" "<" ">" }

/* Insert quotes before and after Q element content */
q::before { content: open-quote }
q::after  { content: close-quote }

to the following HTML fragment:

<HTML lang="en">
  <HEAD>
    <TITLE>Quotes</TITLE>
  </HEAD>
  <BODY>
    <P><Q>Quote me!</Q>
  </BODY>
</HTML>

would allow a user agent to produce:

"Quote me!"

while this HTML fragment:

<HTML lang="no">
  <HEAD>
    <TITLE>Quotes</TITLE>
  </HEAD>
  <BODY>
    <P><Q>Trøndere gråter når <Q>Vinsjan på kaia</Q> blir deklamert.</Q>
  </BODY>
</HTML>

would produce:

+Trøndere gråter når <Vinsjan på kaia> blir deklamert.;

Note. While the quotation marks specified by ‘quotes’ in the previous examples are conveniently located on computer keyboards, high quality typesetting would require different ISO 10646 characters. The following informative table lists some of the ISO 10646 quotation mark characters:

Codepoint Description
" U+0022 QUOTATION MARK (the ASCII double quotation mark)
' U+0027 APOSTROPHE (the ASCII single quotation mark)
U+2039 SINGLE LEFT-POINTING ANGLE QUOTATION MARK
U+203A SINGLE RIGHT-POINTING ANGLE QUOTATION MARK
« U+00AB LEFT-POINTING DOUBLE ANGLE QUOTATION MARK
» U+00BB RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK
U+2018 LEFT SINGLE QUOTATION MARK (single high-6)
U+2019 RIGHT SINGLE QUOTATION MARK (single high-9)
U+201C LEFT DOUBLE QUOTATION MARK (double high-6)
U+201D RIGHT DOUBLE QUOTATION MARK (double high-9)
U+201E DOUBLE LOW-9 QUOTATION MARK (double low-9)

4.1. Inserting quotes with the ‘content’ property

Quotation marks are inserted in appropriate places in a document with the ‘open-quote’ and ‘close-quote’ values of the ‘content’ property. Each occurrence of ‘open-quote’ or ‘close-quote’ is replaced by one of the strings from the value of ‘quotes’, based on the depth of nesting.

Open-quote’ refers to the first of a pair of quotes, ‘close-quote’ refers to the second. Which pair of quotes is used depends on the nesting level of quotes: the number of occurrences of ‘open-quote’ in all generated text before the current occurrence, minus the number of occurrences of ‘close-quote’. If the depth is 0, the first pair is used, if the depth is 1, the second pair is used, etc. If the depth is greater than the number of pairs, the last pair is repeated.

Note that this quoting depth is independent of the nesting of the source document or the formatting structure.

Some typographic styles require open quotation marks to be repeated before every paragraph of a quote spanning several paragraphs, but only the last paragraph ends with a closing quotation mark. In CSS, this can be achieved by inserting "phantom" closing quotes. The keyword ‘no-close-quote’ decrements the quoting level, but does not insert a quotation mark.

The following style sheet puts opening quotation marks on every paragraph in a BLOCKQUOTE, and inserts a single closing quote at the end:

BLOCKQUOTE P:before     { content: open-quote }
BLOCKQUOTE P:after      { content: no-close-quote }
BLOCKQUOTE P.last:after { content: close-quote }

This relies on the last paragraph being marked with a class "last", since there are no selectors that can match the last child of an element.

For symmetry, there is also a no-open-quote keyword, which inserts nothing, but increments the quotation depth by one.

Note. If a quotation is in a different language than the surrounding text, it is customary to quote the text with the quote marks of the language of the surrounding text, not the language of the quotation itself.

For example, French inside English:

The device of the order of the garter is “Honi soit qui mal y pense.”

English inside French:

Il disait: + Il faut mettre l'action en ‹ fast forward ›.;

A style sheet like the following will set the ‘quotes’ property so that ‘open-quote’ and ‘close-quote’ will work correctly on all elements. These rules are for documents that contain only English, French, or both. One rule is needed for every additional language. Note the use of the child combinator (">") to set quotes on elements based on the language of the surrounding text:

:lang(fr) > * { quotes: "+" ";" "\2039" "\203A" }
:lang(en) > * { quotes: "\201C" "\201D" "\2018" "\2019" }

The quotation marks for English are shown here in a form that most people will be able to type. If you can type them directly, they will look like this:

:lang(fr) > * { quotes: "+" ";" "‹" "›" }
:lang(en) > * { quotes: "“" "”" "‘" "’" }

5. Automatic counters and numbering: the ‘counter-increment’ and ‘counter-reset’ properties

Automatic numbering in CSS2 is controlled with two properties, ‘counter-increment’ and ‘counter-reset’. The counters defined by these properties are used with the ‘counter()’ and ‘counters()’ functions of the the ‘content’ property.

Name: counter-increment
Value: [ <identifier> <integer>? ]+ | none
Initial: note
Applies To: all elements, ::before, ::after, ::alternate, ::marker, ::line-marker, margin areas, @footnote areas, and @page context
Inherited: no
Percentages: N/A
Media: all
Computed value: specified value
Name: counter-reset
Value: [ <identifier> <integer>? ]+ | none
Initial: note
Applies To: all elements, ::before, ::after, ::alternate, ::marker, ::line-marker, margin areas, @footnote areas, and @page context
Inherited: no
Percentages: N/A
Media: all
Computed value: specified value

The ‘counter-increment’ property accepts one or more names of counters (identifiers), each one optionally followed by an integer. The integer indicates by how much the counter is incremented for every occurrence of the element. The default increment is 1. Zero and negative integers are allowed.

The ‘counter-reset’ property also contains a list of one or more names of counters, each one optionally followed by an integer. The integer gives the value that the counter is set to on each occurrence of the element. The default is 0.

If ‘counter-increment’ refers to a counter that is not in the scope (see below) of any ‘counter-reset’, the counter is assumed to have been reset to 0 by the root element.

This example shows a way to number chapters and sections with "Chapter 1", "1.1", "1.2", etc.

H1:before {
    content: "Chapter " counter(chapter) ". ";
    counter-increment: chapter;  /* Add 1 to chapter */
    counter-reset: section;      /* Set section to 0 */
}
H2:before {
    content: counter(chapter) "." counter(section) " ";
    counter-increment: section;
}

If an element or pseudo-element resets or increments a counter and also uses it (in its ‘content’ property), the counter is used after being reset or incremented.

If an element or pseudo-element both resets and increments a counter, the counter is reset first and then incremented.

The ‘counter-reset’ property follows the cascading rules. Thus, due to cascading, the following style sheet:

H1 { counter-reset: section -1 }
H1 { counter-reset: imagenum 99 }

will only reset ‘imagenum’. To reset both counters, they have to be specified together:

H1 { counter-reset: section -1 imagenum 99 }

5.1. Nested counters and scope

Counters are "self-nesting", in the sense that re-using a counter in a child element automatically creates a new instance of the counter. This is important for situations like lists in HTML, where elements can be nested inside themselves to arbitrary depth. It would be impossible to define uniquely named counters for each level.

Thus, the following suffices to number nested list items. The result is very similar to that of setting ‘display:list-item’ and ‘list-style: inside’ on the LI element:

OL { counter-reset: item }
LI { display: block }
LI:before { content: counter(item) ". "; counter-increment: item }

The self-nesting is based on the principle that every element or pseudo-element that has a ‘counter-reset’ for a counter X, creates a fresh counter X, the scope of which is the element or pseudo-element, its following siblings, and all the descendants of the element or pseudo-element and its following siblings.

In the example above, an OL will create a counter, and all children of the OL will refer to that counter.

If we denote by item[n] the nth instance of the "item" counter, and by "(" and ")" the beginning and end of a scope, then the following HTML fragment will use the indicated counters. (We assume the style sheet as given in the example above).

<OL>               <!-- (set item[0] to 0          -->
  <LI>item         <!--  increment item[0] (= 1)   -->
  <LI>item         <!--  increment item[0] (= 2)   -->
    <OL>           <!--  (set item[1] to 0         -->
      <LI>item     <!--   increment item[1] (= 1)  -->
      <LI>item     <!--   increment item[1] (= 2)  -->
      <LI>item     <!--   increment item[1] (= 3)  -->
        <OL>       <!--   (set item[2] to 0        -->
          <LI>item <!--    increment item[2] (= 1) -->
        </OL>      <!--   )                        -->
        <OL>       <!--   (set item[3] to 0        -->
          <LI>     <!--    increment item[3] (= 1) -->
        </OL>      <!--   )                        -->
      <LI>item     <!--  increment item[0] (= 3)   -->
  <LI>item         <!--  increment item[0] (= 4)   -->
</OL>              <!-- )                          -->
<OL>               <!-- (reset item[4] to 0        -->
  <LI>item         <!--  increment item[4] (= 1)   -->
  <LI>item         <!--  increment item[4] (= 2)   -->
</OL>              <!-- )                          -->

The ‘counters()’ function generates a string composed of the values of all counters with the same name, separated by a given string.

The following style sheet numbers nested list items as "1", "1.1", "1.1.1", etc.

OL { counter-reset: item }
LI { display: block }
LI:before { content: counters(item, "."); counter-increment: item }

The above counters() example would be terribly wrong for the above above example since the last list is number 4. The examples need to reset on the :before pseudo-element for it to work right)

5.2. Counter styles

By default, counters are formatted with decimal numbers, but all the styles available for the ‘list-style-type’ property are also available for counters. The notation is:

counter(name)

for the default style, or:

counter(name, <'list-style-type'>)

All the styles are allowed, including the glyph types such as ‘disc’, ‘circle’, and ‘square’. The ‘none’ value is also allowed, and causes the counter to generate nothing.

H1:before        { content: counter(chno, upper-latin) ". " }
H2:before        { content: counter(section, upper-roman) " - " }
BLOCKQUOTE:after { content: " [" counter(bq, hebrew) "]" }
DIV.note:before  { content: counter(notecntr, disc) " " }
P:before         { content: counter(p, none) } /* inserts nothing */

5.3. Counters in elements with ‘display: none

An element that is not displayed (‘display’ set to ‘none’) cannot increment or reset a counter.

For example, with the following style sheet, H2s with class "secret" do not increment ‘count2’.

H2.secret {counter-increment: count2; display: none}

Elements with visibility set to ‘hidden’, on the other hand, do increment counters.

5.4. Reserved Counter Names

The ‘list-item’, ‘section-note’, ‘endnote’, and ‘footnote’ counters are not reserved. They are ordinary counters that happen to be incremented and used by other properties as well as the counter properties.

The ‘total-pages’ counter, however, is reserved. Resetting or increasing this counter has no effect. See the Paged Media module [CSS3PAGE] for more information on this counter.

6. Named strings

MERGE WITH GCPM

CSS3 introduces ‘named strings’, which are the textual equivalent of counters and which have a distinct namespace from counters. Named strings follow the same nesting rules as counters. The ‘string-set’ property accepts values similar to the ‘content’ property, including the extraction of the current value of counters.

Named strings are a convenient way to pull metadata out of the document for insertion into headers and footers. In HTML, for example, META elements contained in the document HEAD can set the value of named strings. In conjunction with attribute selectors, this can be a powerful mechanism:

META[author] { string-set: author attr(author); }
HEAD > TITLE { string-set: title contents; }
@page:left {
  @top {
    text-align: left;
    vertical-align: middle;
    content: string(title);
  }
}
@page:right {
  @top {
    text-align: right;
    vertical-align: middle;
    content: string(author);
  }
}

This section is missing a property definition.

This section is missing a definition of the string() function.

The following example captures the contents of H1 elements, which represent chapter names in this hypothetical document.

H1 { string-set: chapter contents; }

When an H1 element is encountered, the ‘chapter’ string is set to the element's textual contents, and the previous value of ‘chapter’, if any, is overwritten.

6.1. @counter-styles

This at-rule can be used to change the counter's default counter style. This is typicially used to change, for example, the footnote style:

@counter-styles {
   footnote: super-decimal;
}

The default list style types for counters is ‘decimal’ except for the ‘footnote’ counter which defaults to ‘footnotes’.

6.2. Determining which counter or string-set value to use: the ‘page-policy’ property

Name: page-policy
Value: start | first | last
Initial: start
Applies to: @counter and @string blocks
Inherited: N/A
Percentages: N/A
Media: paged
Computed value: specified value

page-policy’ determines which page-based occurance of a given element is applied to a counter or string value:

start
Takes the value of the counter or string at the beginning of the page (before applying style to the elements of the page, but after applying it to the @page context itself).
first
Takes the value after the first state change in the counter or string during processing of the page.
last
Takes the value following the final state change on the page.

The following example places the chapter name in the header, specifying that it is the value of the string at the end of the page. Example:

@string chapter { page-policy: last; }
@page {
  size: 21.0cm 29.7cm; /* A4 */
  @top {
    text-align: right;
    vertical-align: center;
    content: string (chapter);
  }
}

To use the chapter name as it was when the processing of the page started, the designer would specify a ‘page-policy’ of ‘start’ instead of ‘last’. Designers can also use the value of a string or counter after its first state change on a page by specifying ‘first’.

7. Inserting and replacing content with the content property

Name: content
Value: [ [ <uri> | icon ] ‘,’ ]* [ normal | none | inhibit | <content-list> ]
Initial: normal
Applies To: all elements, ::before, ::after, ::alternate, ::marker, ::line-marker, margin areas, and @footnote areas
Inherited: no
Percentages: N/A
Media: all
Computed value: The specified value with each occurrence of ‘normal’ expanded as per the prose below.

The ‘content’ property dictates what is rendered inside the element or pseudo-element. It takes a comma separated list of URIs followed by a space separated list of tokens. If there are multiple URIs provided, then each is tried in turn until a value which is both available and supported is found. The last value is used as a fallback if the others fail.

<uri>

For URIs other than URIs in the last comma separated section of the value, as those in the following example:

h1 { content: url(header/mng), url(header/png), none; }

...then if the URI is available and the format is supported, then the element or pseudo-element becomes a replaced element, otherwise, the next item in the comma separated list is used, if any. In the example above, if ‘header/mng’ wasn't in a supported format, then ‘header/png’ would have been used instead. In the example above, if ‘header/png’ wasn't available either, then the <h1> element would be empty, as the last alternative is ‘none’.

To make an element fallback on its contents, you have to explicitly give ‘contents’ as a fallback:

content: url(1), url(2), url(3), contents;

If the URI is part of the last comma separated value in the list, as the second URI in the following example:

h1 { content: url(welcome), "Welcome to: " url(logo); }

...then if the file is available and the format is supported, then an anonymous replaced inline element is inserted, otherwise the image is ignored (as if it hadn't been given at all).

When a URI is used as replaced content, it affects the generation of ‘::before’ and ‘::after’ pseudo-elements.

icon
This value is the same as the ‘<uri>’ value above, but takes the resource from the ‘icon’ property. If the ‘icon’ property has the value ‘none’ then this is equivalent to the case where the given URI is not available.
normal

For an element, this computes to ‘contents’.

For ‘::alternate’, if the originating element uses the ‘footnote’, ‘endnote’, or ‘section-note’ counter in its ‘content’ property then the computed value of ‘content’ is ‘contents’, otherwise it computes to ‘inhibit’.

For ‘::before’, ‘::after’, and ‘::line-marker’ this computes to ‘inhibit’.

For ‘::marker’, if the originating element's originating element uses ‘footnote’ in its ‘content’ property then ‘normal’ computes to the computed value of the ‘list-style-image’ property if the list-style-image is not ‘none’, otherwise ‘counter(footnote, <list-style-type>) "suffix"’ where <list-style-type> is the computed value of the ‘list-style-type’ property if that property is not ‘none’ and suffix is the suffix appropriate for that list style type, otherwise ‘inhibit’.

For ‘::marker’, if the originating element's originating element uses ‘endnote’ in its ‘content’ property then ‘normal’ computes to the computed value of the ‘list-style-image’ property if the list-style-image is not ‘none’, otherwise ‘counter(endnote, <list-style-type>) "suffix"’ where <list-style-type> is the computed value of the ‘list-style-type’ property if that property is not ‘none’ and suffix is the suffix appropriate for that list style type, otherwise ‘inhibit’.

For ‘::marker’, if the originating element's originating element uses ‘section-note’ in its ‘content’ property then ‘normal’ computes to the computed value of the ‘list-style-image’ property if the list-style-image is not ‘none’, otherwise ‘counter(section-note, <list-style-type>) "suffix"’ where <list-style-type> is the computed value of the ‘list-style-type’ property if that property is not ‘none’ and suffix is the suffix appropriate for that list style type, otherwise ‘inhibit’.

Otherwise, for ‘::marker’, if the computed value of ‘display’ for the originating element is ‘list-item’ then ‘normal’ computes to the computed value of the ‘list-style-image’ property if the list-style-image is not ‘none’, otherwise ‘counter(list-item, <list-style-type>) "suffix"’ where <list-style-type> is the computed value of the ‘list-style-type’ property if that property is not ‘none’ and suffix is the suffix appropriate for that list style type, otherwise ‘inhibit’.

For the ‘@footnote’ area, it computes to ‘pending(footnote)’.

For margin areas, it computes to ‘none’.

none

On elements, this inhibits the children of the element from being rendered as children of this element, as if the element was empty.

On pseudo-elements it causes the pseudo-element to have no content.

In neither case does it prevent any pseudo-elements which have this element or pseudo-element as a superior from being generated.

inhibit

On elements, this inhibits the children of the element from being rendered as children of this element, as if the element was empty.

On pseudo-elements, this inhibits the creation of the pseudo-element, as if ‘display’ computed to ‘none’.

In both cases, this further inhibits the creation of any pseudo-elements which have this pseudo-element as a superior.

<content-list>

[ pending(<identifier>) | <string> | contents | footnote | endnote | section-note | list-item | <counter> | <named-string> | open-quote | close-quote | no-open-quote | no-close-quote | icon | <glyph> | <uri> | <datetime> | document-url | <target> ]+

One or more of the following values, concatenated.

pending(<identifier>)

This causes all elements and pseudo-elements whose ‘move-to’ property computes to the specified identifier to be inserted as children of the current element (or pseudo-element). Note: This doesn't change the DOM, and elements and pseudo-elements that have been moved inherit from their position in the DOM, not from their new position.

This must be the case, because otherwise it would be impossible to determine the value of ‘move-to’. Unfortunately, this can cause some unfortunate discontinuities, such as adjacent footnotes using different fonts because they were moved from elements with different fonts. It is therefore important that moved content be styled with the new location in mind.

Note that only elements and pseudo-element that have not yet been reinserted into content are moved. For example:

moved { move-to: insert; }
insert { content: pending(insert); }

<root>
  <moved> A </moved>
  1
  <insert/>
  2
  <moved> B </moved>
  3
  <insert/>
</root>

...would result in "1 A 2 3 B".

If used on an element or pseudo-element (particularly ‘::alternate’) which has a ‘move-to’ property with a computed value other than ‘here’, the content pending at the pseudo-element's superior's position is inserted, not the content pending at the element or pseudo-element's insertion point. Similarly if used on a child of an element that has been moved: the ‘content’ property is evaluated before the element is inserted in its new position. This should prevent an element ever being inserted into itself or other such existential conundrums.

Counters on content that is moved in this way are evaluated at the point of origin, not the insertion point.

The identifiers ‘here’ and ‘normal’ are valid, in that they do not cause a parse error and are not ignored, but they are useless as the ‘move-to’ property cannot ever be set to an identifier with either of those values.

Need to define exactly how this interacts with ‘position:fixed’. Does ‘position:fixed’ cause multiple rendering objects to be created, one per page? If so where does ‘move-to’ on a ‘position:fixed’ element move from?

"" (the empty string)

If the element or pseudo-element's ‘display’ property computes to anything but ‘inline’ then the element or pseude-element contains an empty anonymous inline box, otherwise the element contains an empty string.

(This is a formal way of saying that an empty string is different from ‘none’ in that it forces the creation of a line box, even if the line box would be empty.)

<string>

The element or pseudo-element contains the specified string. Occurrences of line-feed or space characters in the string are handled according to the properties given in the Text module.

contents

The element's descendents. Since this can only be used once per element (you can't duplicate the children if, e.g., one is a plugin or form control), it is handled as follows:

If set on the element:

Always honoured. Note that this is the default, since the initial value of ‘content’ is ‘normal’ and ‘normal’ computes to ‘contents’ on an element.

If set on a ‘::marker’ or ‘::line-marker’ pseudo-element:

Evaluates to nothing (like ‘none’).

If set on one of the element's other pseudo-elements:

Check to see that it is not set on a "previous" pseudo-element, in the following order, depth first:

  1. the element itself
  2. ::alternate
  3. ::before
  4. ::after

If it is already used, then it evaluates to nothing (like ‘none’). Only pseudo-elements that are actually generated are checked. Thus

/* ::after(2) { content: inhibit; } /* implied by initial value */
::after(9999) { content: contents }

...would typically not change anything.

So for example, in the following case:

foo { content: none; }
foo::before { content: '[' counter(footnote) ']' contents; }
foo::alternate { content: counter(footnote) '. ' contents; }

...the ‘::before’ pseudo-element's contents would become ‘[1]’, and the footnote would contain ‘1. ’ followed by the element's contents, because the ‘::alternate’ takes priority over the ‘::before’ pseudo-element at the same depth.

However, in the following case:

/* foo { content: normal; }   /* this is the initial value */
foo::after { content: contents; }

...the element's ‘content’ property would compute to ‘contents’ and the after pseudo element would have no contents (equivalent to ‘none’) and thus would not appear.

Note that while it is useless to include ‘contents’ twice in a single ‘content’ property, that is not a parse error. The second occurrence simply has no effect, as it has already been used. It is also not a parse error to use it on a marker pseudo-element, it is only during the rendering stage that it gets treated like ‘none’.

<counter>

Counters may be specified with two different functions: ‘counter()’ or ‘counters()’. The former has two forms: ‘counter(name)’ or ‘counter(name, style)’. The generated text is the value of the named counter at this point in the formatting structure; it is formatted in the indicated style (the default is specified using ‘@counter’ rules). The latter function also has two forms: ‘counters(name, string)’ or ‘counters(name, string, style)’. The generated text is the value of all counters with the given name at this point in the formatting structure, separated by the specified string. The counters are rendered in the indicated style (the default is again specified using ‘@counter’ rules). See the section on automatic counters and numbering for more information.

To get the fixed symbols defined as counters (‘disc’, ‘circle’, ‘quare’, ‘disclosure-open’, ‘disclosure-closed’), you can write ‘content: counter(foo, disc)’, but as the counter is not important, it might be useful to allow ‘content: disc’ as well.

<named-string>

Set strings may be specified with the ‘string(name)’ expression. The generated text is the value of the named string at this point in the formatting structure. See the section on named strings for more information.

open-quote and close-quote

These values are replaced by the appropriate string from the ‘quotes’ property.

no-open-quote and no-close-quote

Inserts nothing (as in ‘none’), but increments (decrements) the level of nesting for quotes.

<glyph>

Inserts the specified symbol. The available symbols are:

box
A hollow square. (like □ U+25A1 WHITE SQUARE, ◻ U+25FB WHITE MEDIUM SQUARE, or ◽ U+25FD WHITE MEDIUM SMALL SQUARE)
check
A check mark. On interactive media, it is suggested that the same glyph which is used on the platform to render a checked menu item be used for ‘check’. (like ✓ U+2713 CHECK MARK)
circle
A hollow circle. (like ◦ U+25E6 WHITE BULLET)
diamond
A filled diamond. On interactive media, it is suggested that the same glyph which is used on the platform next to a selected menu item be used for ‘diamond’. On some platforms, this is similar to ‘disc’. (like ◆ U+25C6 BLACK DIAMOND or ♦ U+2666 BLACK DIAMOND SUIT)
disc
A filled circle. (like • U+2022 BULLET)
hyphen
A hyphen bullet. (like ⁃ U+2043 HYPHEN BULLET or – U+2013 EN DASH)
square
A filled square. (like ■ U+25A0 BLACK SQUARE, ◼ U+25FC BLACK MEDIUM SQUARE, or ◾ U+25FE BLACK MEDIUM SMALL SQUARE)

For more information on the list of symbols and their definitions, see the Lists module [CSS3LIST].

<datetime>

Dates and times can be specified with two functions, ‘date()’ and ‘time()’. See the section on dates and times for more information.

document-url

The URI of the current document. For local files, this may simply be the local file name.

<target>

Using the target expressions, authors can write cross-references. Need to write this up.

Sync with GCPM

8. Replaced content

If the computed value of the part of the ‘content’ property that ends up being used is a single URI, then the element or pseudo-element is a replaced element. The box model defines different rules for the layout of replaced elements than normal elements. Replaced elements do not have ‘::before’ and ‘::after’ pseudo-elements; the ‘content’ property in the case of replaced content replaces the entire contents of the element's box.

Acknowledgments

Stuart Ballard, David Baron, Bert Bos, and Tantek Çelı̇k provided invaluable suggestions used in this specification.

References

Normative references

[CSS3LIST]
Tab Atkins Jr. CSS Lists and Counters Module Level 3. 24 May 2011. W3C Working Draft. (Work in progress.) URL: http://www.w3.org/TR/2011/WD-css3-lists-20110524
[CSS3PAGE]
Melinda Grant; et al. CSS Paged Media Module Level 3. 14 March 2013. W3C Working Draft. (Work in progress.) URL: http://www.w3.org/TR/2013/WD-css3-page-20130314/

Other references

[SELECT]
Tantek Çelik; et al. Selectors Level 3. 29 September 2011. W3C Recommendation. URL: http://www.w3.org/TR/2011/REC-css3-selectors-20110929/

Index

Property index

Property Values Initial Applies to Inh. Percentages Media
content [ [ <uri> | icon ] ‘,’ ]* [ normal | none | inhibit | <content-list> ] normal no N/A all
counter-increment [ <identifier> <integer>? ]+ | none note no N/A all
counter-reset [ <identifier> <integer>? ]+ | none note no N/A all
page-policy start | first | last start @counter and @string blocks N/A N/A paged
quotes foo | bar text no N/A visual