W3C

CSS Generated Content for Paged Media Module

Editor's Draft 10 October 2011

This version:
http://www.w3.org/TR/2011/ED-css3-gcpm-20111010
Latest version:
http://www.w3.org/TR/css3-gcpm
Previous version:
http://www.w3.org/TR/2007/WD-css3-gcpm-20070205
Editor:
Håkon Wium Lie, Opera Software, howcome@opera.com

Abstract

This module describes features often used in printed publications. Most of the specified functionality involves some sort of generated content where content from the document is adorned, replicated, or moved in the final presentation of the document. Along with two other CSS3 modules – multi-column layout and paged media – this module offers advanced functionality for presenting structured documents on paged media. This specification only applies to the ‘print’ media type.

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-gcpm” in the subject, preferably like this: “[css3-gcpm] …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.

This functionality described in this WD is scaled down compared to earlier versions. The remaining functionality is considered to be useful, to fit well into the CSS framework, and to be within reach of implementations. Indeed, significant parts of the draft has already been implemented.

Table of contents

1. Introduction

(This section is not normative.)

This specification describes features often used in printed publications. Some of the proposed functionality (e.g., hyphenation, the new list style types, and border segments) may also used with other media types. However, this specification is only concerned with the ‘print’ media type.

2. Running headers and footers

To aid navigation in printed material, headers and footers are often printed in the page margins. [CSS3PAGE] describes how to place headers and footers on a page, but not how to fetch headers and footers from elements in the document. This specification offers two ways to achieve this. The first mechanism is named strings which copies the text (without style, structure, or replaced content) from one element for later reuse in margin boxes. The second mechanism is running elements which moves elements (with style, structure, and replaced content) into a margin box.

2.1. Named strings

Named strings can be thought of as variables that can hold one string of text each. Named strings are created with the ‘string-set’ property which copies a string of text into the named string. Only text is copied; not style, structure, or replaced content.

Consider this code:

h1 { string-set: title content() }

Whenever an h1 element is encountered, its textual content is copied into a named string called title. Its content can be retrieved in the ‘content’ property:

@page :right { @top-right { content: string(title) }}

2.1.1. Setting named strings: the ‘string-set’ property

Name: string-set
Value: [[ <identifier> <content-list>] [, <identifier> <content-list>]* ] | none
Initial: none
Applies to: all elements
Inherited: no
Percentages: N/A
Media: all
Computed value: as specified value

The ‘string-set’ property accepts a comma-separated list of named strings. Each named string is followed by a content list that specifies which text to copy into the named string. Whenever an element with value of ‘string-set’ different from ‘none’ is encountered, the named strings are assigned their respective value.

For the ‘string-set’ property, <content-list> expands to one or more of these values, in any order:

<string>
a string, e.g. "foo"
<counter>
the counter() or counters() function, as per CSS 2.1 section 4.3.5
<content>
the ‘content()’ function returns the content of elements and pseudo-elements. The functional notation accepts an optional argument:
content()
Without any arguments, the function returns the textual content of the element, not including the content of its ::before and ::after pseudo-element. The content of the element's descendants, including their respective ::before and ::after pseudo-elements, are included in the returned content.
content(before)
The function returns the textual content of the ::before pseudo-element the content of the element.
content(after)
The function returns the textual content of the ::after pseudo-element the content of the element.
content(first-letter)
The function returns the first letter of the content of the element. The definition of a letter is the same as for :first-letter pseudo-elements.

The expected use for ‘content(first-letter)’ is to create one-letter headers, e.g., in dictionaries.

env()
This function returns data from the local environment of the user at the time of formatting. The function accepts one of these keywords:
  • env(url): returns the URL of the document
  • env(date): returns the date on the user's system at the time of formatting
  • env(time): returns the time on the user's system at the time of formatting
  • env(date-time): returns the date and time on the user's system at the time of formatting

Information about date and time is formatted according to the locale of the user's system.

Or, should there be a way to specify the locale? Or should we simply format all in ISO format (e.g., 2010-03-30)?

On many systems, preformatted strings in the user's locale can be found through the strftime function. The date, time and date-time strings can be found by using the "%x", "%X" and "%c" conversion strings, respectively.

@page {
  @top-right { content: env(url) }
  @bottom-right { content: env(date-time) }
}

Named strings can only hold the result of one assignment; whenever a new assignment is made to a named string, its old value is replaced.

User agents, however, must be able to remember the result of more than one assignment as the ‘string()’ functional value (described below) can refer to different assignments.

The scope of a named string is the page of the element to which the ‘string-set’ property is attached and subsequent pages.

The name space of named strings is different from other sets of names in CSS.

The ‘string-set’ property copies text as well as white-space into the named string.

h2 { 
  string-set: header "Chapter " counter(header) ": " content();
  counter-increment: header;
}

Note that the string called "header" is different from the counter with the same name. The above code may result in header being set to "Chapter 2: Europa".

This example results in the same value being assigned to header as in the previous example.

h2:before { content: "Chapter " counter(header) } 
h2 { 
  string-set: header content(before) content();
  counter-increment: header } 
dt { string-set: index content(first-letter) }

The content is copied regardless of other settings on the element. In this example, H1 elements are not displayed, but their content is copied into the named string.

h1 { 
  display: none;
  string-set: header content();
}

2.1.2. Using named strings

The content of named strings can be recalled by using the ‘string()’ value on the ‘content’ property. The ‘string()’ value has one required argument, namely the name of the string.

@page { @top-center { content: string(header) }}
@page { @right-middle { content: string(index) }}
@page { @top-left { content: string(entry) }}
h1 { string-set: header "Chapter " counter(chapter) content() }
dt { string-set: index content(first-letter), entry content() }

If the value of the named string is changed by an element on a certain page, the named string may have several values on that page. In order to specify which of these values should be used, an optional argument is accepted on the ‘string()’ value. This argument can have one of four keywords:

In this example, the first term on the page will be shown in the top left corner and the last term on the page will be shown in the top right corner. In top center of the page, the first letter of first term will be shown.

@page { @top-left { content: string(term, first) }}
@page { @top-right { content: string(term, last) }}
@page { @top-center { content: string(index, first) }}
dt { string-set: index content(first-letter), term content() }

In this example, the header in the top center will be blank on pages where ‘h1’ elements appear. On other pages, the string of the previous ‘h1’ element will be shown.

@page { @top-center { content: string(chapter, first-except) }}
h1 { string-set: chapter content() }

If the named string referred to in a ‘string()’ value has not been assigned a value, the empty string is used.

2.2. Running elements

Named strings, as described above, can only hold textual content; any style, structure or replaced content associated with the element is ignored. To overcome this limitation, a way of moving elements into running headers and footers is introduced.

Elements that are moved into headers and footers are repeated on several pages; they are said to be running elements. To support running elements, a new value – running() – is introduced on the ‘position’ property. It has one required argument: the name by which the running element can be referred to. A running element is not shown in its natural place; there it is treated as if ‘display: none’ had been set. Instead, the running element may be displayed in a margin box.

Like counters and named strings, the name of a running element is chosen by the style sheet author, and the names have a separate name space. A running element can hold one element, including its pseudo-elements and its descendants. Whenever a new element is assigned to a running element, the old element is lost.

User agents, however, must be able to remember the result of more than one assignment as the ‘element()’ value (described below) can refer to different assignments.

Running elements inherit through their normal place in the structure of the document.

title { position: running(header) }
@page { @top-center {
  content: element(header) }
}

Like the ‘string()’ value, the ‘element()’ value accepts an optional second argument:

start
first
last
first-except

The keywords have the same meaning as for the ‘string()’ value.

The ‘element()’ value cannot be combined with any other values.

In this example, the header is hidden from view in all media types except print. On printed pages, the header is displayed top center on all pages, except where h1 elements appear.

<style>
  div.header { display: none }
  @media print {
  div.header {
    display: block;
    position: running(header);
  }
  @page { @top-center { content: element(header, first-except) }}
</style>
...
<div class="header">Introduction</div>
<h1 class="chapter">An introduction</div>

This code illustrates how to change the running header on one page in the middle of a run of pages:

...
<style>
@page { @top-center {
  content: element(header, first) }}
.header { position: running(header) }
.once { font-weight: bold }
</style>
...
<div class="header">Not now</div>
<p>Da di ha di da di ...
  <span class="header once">NOW!</span>
  <span class="header">Not now</span>
  ... da di ha di hum.</p>
...
The header is "Not now" from the outset, due to the "div" element. The first "span" element changes it to "NOW!" on the page where the "span" element would have appeared. The second "span" element, which would have appeared on the same page as the first is not used because the ‘first’ keyword has been specified. However, the second "span" element still sets the exit value for "header" and this value is used on subsequent pages.

3. Leaders

A leader is a visual pattern that guides the eye. Typically, leaders are used to visually connect an entry in a list with a corresponding code. For example, there are often leaders between titles and page numbers in a table of contents (TOC). Another example is the phone book where there are leaders between a name and a telephone number.

In CSS3, a leader is composed of series of glyphs through the ‘leader()’ value on the ‘content’ property. The functional notation accepts one value which describes the glyph pattern that make up the leader. These values are allowed:

Using the keyword values is equivalent to setting a string value. The table below shows the equivalents:

Keyword String Unicode characters
leader(dotted) leader(‘. ’) \002E \0020
leader(solid) leader(‘_’) \005F
leader(space) leader(‘ ’) \0020

The string inside the parenthesis is called the leader string.

In its simplest form, the ‘content’ property only takes one ‘leader()’ value:

heading::after { content: leader(dotted) }

The leader string must be shown in full at least once and this establishes the minimum length of the leader. To fill the available space, the leader string is repeated as many times as possible in the writing direction. At the end of the leader, a partial string pattern may be shown. White space in leaders is collapsed according to the values on white-space properties.

These properties influence the appearance of leaders: all font properties, text properties, ‘letter-spacing’, white-space properties, background properties, and ‘color’.

User Agents should attempt to align corresponding glyphs from the leader pattern between consecutive lines.

In a more complex example, the ‘leader’ value is combined with other values on the ‘content’ property:

ul.toc a::after {
  content: leader(". . . ") target-counter(attr(href, url), page);
}

If the content connected by a leader end up on different lines, the leader will be present on all lines. Each leader fragment honors the minimum length of the leader.

Consider this code:

<style>
.name::after { content: leader(dotted) }
</style>
<div class="entry">
<span class="name">John Doe</span>
<span class="number">123456789</span>
</div>

If the name and number end up on different lines (e.g., in a narrow column), it may be formatted like this:

John Doe....
...123456789

To determine the length of the leaders, user agents must do the following for each line:

  1. Lay out the content with leaders of minimum lengths
  2. Determine the empty space left on the line.
  3. Distribute the empty space between the leaders on the line. Glyphs must not be shown partially. All leaders on the line should, to the extent possible, have the same length. This may not always be possible as the minimum leader length must be honored.
  4. Fill the empty space with the specified leader pattern.

Consider this code:

<style>
cite::before { content: leader('  ') }
</style>
<blockquote>
  Bla great bla bla world bla bla
  empire bla bla color bla bla
  history bla bla forever.
    <cite>John Johnson</cite>
</blockquote>

Depending on the width of the containing block, this may be rendered as:

  Bla great bla bla world bla bla
  empire bla bla color bla bla
  history bla bla forever.   John 
  Johnson

However, this rendering is preferable:

  Bla great bla bla world bla bla
  empire bla bla color bla bla
  history bla bla forever.
                     John Johnson

To indicate that John Johnson should be kept on one line, this rule can be added to the style sheet:

cite { text-wrap: suppress }

Until ‘text-wrap’ is widely supported, this rule can also be used:

cite { white-space: nowrap }

If the containing element is wider, this may be the resultant presentation:

  Bla great bla bla world bla bla empire
  bla bla color bla bla history bla bla 
  forever.                  John Johnson

4. Cross-references

It is common to refer to other parts of a document by way of a section number (e.g., "See section 3.4.1"), a page number (e.g., "See discussion on page 72"), or a string (e.g., "See the chapter on Europe"). Being able to resolve these cross-references automatically saves time and reduces the number of errors.

4.1. The ‘target-counter’ and ‘target-counters’ values

Numerical cross-references are generated by ‘target-counter()’ and ‘target-counters()’ values that fetch the value of a counter at the target end of the link. These functions are similar to the ‘counter()’ and ‘counters()’ functions, except that they fetch counter values from remote elements. ‘target-counter()’ has two required arguments: the url of the link, and the name of a counter. ‘target-counters()’ has three required arguments: the url of the link, the name of a counter, and a separator string. Both functions accepts an optional argument at the end that describes which list style type to use when presenting the resulting number; ‘decimal’ being the default.

This style sheet specifies that a string like " (see page 72)" is added after a link:

a::after { content: "(see page " target-counter(attr(href, url), page, decimal) ")" }

This style sheet specifies that a string like " (see section 1.3.5)" is added after a link:

a::after { content: "(see section " target-counters(attr(href, url), section, ".", decimal) ")" }

4.2. The ‘target-text’ value

Textual cross-references are generated by ‘target-text()’ which fetches the textual content from the target end of the link. Only text is copied; not style, structure, or replaced content. ‘target-text()’ has one required argument: the url of the link. An optional second argument specifies exactly which content is fetched. There are four possible values:

content()
refers to the textual content of the element, not including the content of its ::before and ::after pseudo-element. The content of the element's descendants, including their respective ::before and ::after pseudo-elements, are included in the returned content.
content(before)
refers to the content of the element's ::before pseudo-element. This is the default value.
content(after)
refers to the content of the element's ::after pseudo-element
content(first-letter)
refers to the first letter of the textual content of the element, not including the content of its ::before and ::after pseudo-element.

To generate this text

See Chapter 3 ("A better way") on page 31 for an in-depth evaluation.

from this markup:
<p>See <a href="#chx">this chapter</a> for an in-depth evaluation.
...
<h2 id="chx">A better way</h2>
this CSS code can be used:
h2 { counter-increment: chapter }
a { content: "Chapter " target-counter(attr(href, url), chapter) 
   ' ("'  target-text(attr(href), content()) '") on page '
   target-counter(attr(href, url), page);

5. Footnotes

A footnote is a note typically placed at the bottom of a page that comments on or cites a reference. References to footnotes are marked with a note-call in the main text. The rendering of footnotes is complex. As far as possible, footnotes try to reuse other parts of CSS. However, due to the typographic traditions of footnotes, some new functionality is required to support footnotes in CSS:

In order to support footnotes in CSS, the following functionality is added:

In its simplest form, making a footnote is simple.

<style>
.footnote { float: footnote }
</style>

<p>A sentence consists of words. <span class="footnote">Most often.</span>.

In this example, the text Most often. will be placed in a footnote. A note-call will be left behind in the main text and a corresponding marker will be shown next to the footnote. Here is one possible rendering:

A sentence consists of words. ¹

¹ Most often.

To support legacy browsers, it is often better to make a link to the note rather than including the text inline. This example shows how to fetch the content of a note and place it in a footnote.

<style>
@media print {
  .footnote { 
    float: footnote;
    content: target-pull(attr(href, url)) }
  .call { display: none }
}
</style>
...
<p>A sentence consists of words<a class="footnote" href="#words"> [3]</a>.
...
<p id=words><span class="call">[3]</span> Most often.

When shown in a legacy browser, the content of the element will be shown as a clickable link to an endnote. When printed according to this specification, there will be a footnote:

A sentence consists of words¹.

¹ Most often.
Consider this markup:
<p>Sorry, <span title="This is, of course, a lie.">we're closing for lunch</span>.

The content of the "title" attribute can be turned into a footnote with this code:

span[title]::after { 
  content: attr(title);
  float: footnote;
}

5.1. Turning elements into footnotes

An element with ‘float: footnote’ (called a footnote element) is moved to the footnote area and a footnote-call pseudo-element is put in its original place.

span.footnote { 
  float: footnote;
}

Footnote elements are presented inside the footnote area, but they inherit through their normal place in the structure of the document.

The ‘display’ property on footnote elements is ignored. Instead, the value of the ‘display’ property in the @footnote context determines if footnotes are block or inline elements.

In this example, the footnotes are displayed inline:

@footnote { 
  display: inline;
}
span.footnote { 
  float: footnote;
}

Here is one possible presentation of inline footnotes:

¹ The first footnote. º The second footnote. 

For each new footnote element, the ‘footnote’ counter is automatically incremented.

5.2. The footnote area

All elements with ‘float: footnote’ are moved to the footnote area. The footnote area is described by an @footnote-rule inside the @page-rule. By default, the footnote area appears at the bottom of the page, but it can be positioned in other places.

Should the footnote are be positioned using page floats or (fixed?) absolute positioning? Or both?

These rules place the footnote area at the bottom of the page, spanning all columns:

@page {
  @footnote { 
    float: bottom;
    column-span: all;
    width: 100%;
  }
}

These rules place the footnote area at the bottom of the first column:

@page {
  @footnote { 
    float: bottom;
    width: 100%;
  }
}

This code places the footnote area at the bottom of the right column:

@page {
  @footnote { 
    float: bottom-corner;
    width: 100%;
  }
}

The content of the footnote area is considered to come before other content which may compete for the same space on the same page.

@page { @footnote { float: bottom page}}
div.figure { float: bottom page }

If figures and footnotes are on the same page, the footnotes will appear below the figures as they are floated to the bottom before the figures.

Potentially, every page has a footnote area. If there are no footnotes on the page, the footnote area will not take up any space. If there are footnotes on a page, the layout of the footnote area will be determined by the properties/values set on it, and by the footnote elements elements inside it.

These properties apply to the footnote area: ‘content’, ‘border’, ‘padding’, ‘margin’, ‘height’, ‘width’, ‘max-height’, ‘max-width’, ‘min-height’, ‘min-width’, the background properties.

This example uses some of the applicable properties on @footnote:

@footnote {
  margin-top: 0.5em;
  border-top: thin solid black;
  border-clip: 4em;
  padding-top: 0.5em;
}

The result of this code is a footnote area separated from other content above it by margin, border and padding. Only 4em of the border is visible due to the ‘border-clip’ property, which is defined in CSS Backgrounds and Borders Module Level 4. .

5.3. Footnote calls

When an element is moved to the footnote area, a footnote-call is left behind. By default, User Agents must behave as if this code is part of the default style sheet:

::footnote-call {
  content: counter(footnote, super-decimal);
}

The resulting note call is a super-script decimal number.

5.4. Footnote markers

A ::footnote-marker pseudo-element is added to each footnote element, in the same place, and replacing, the ::before pseudo-element. User agents must, by default, show the "footnote" counter in the footnote-marker.

User Agents may display footnote-calls and footnote-markers this way by default:

::footnote-call {
  content: counter(footnote, super-decimal);
}
::footnote-marker {
  content: counter(footnote, super-decimal);
}

Marker elements are discussed in more detail in the CSS Lists module [CSS3LIST]. One suggested change to that module is to honor the value of ‘list-style-position’ on the ::footnote-marker pseudo-element itself rather than the corresponding list-item element. Further, one clarification to the horizontal placement of the marker is suggested: the margin box of the marker box is horizontally aligned with the start of the line box.

5.5. Counting footnotes

The "footnote" counter is automatically incremented each time a footnote is generated. That is, the "footnote" counter is incremented by one each time an element with ‘float: footnote’ appears.

The footnote counter can be reset with the ‘counter-reset’ property.

This code resets the "footnote" counter on a per-page page basis:
@page { counter-reset: footnote }

Should one also be able to manually increment the "footnote" counter?

5.6. Laying out footnotes

Footnotes must appear as early as possible under the following constraints:

  1. A footnote marker may not appear on an earlier page than the footnote call.
  2. Footnotes may not appear out of document order.
  3. The footnote area is limited in size by ‘max-height’, unless the page contains only footnotes. (E.g., if at the end of the document there are still footnotes unprinted, the User Agent can use the whole page to display footnotes.)
  4. If there is a footnote call on a page, the footnote area may not be empty, unless its ‘max-height’ is too small.

5.7. Footnote magic

When an element is turned into a footnote, certain magical things happen. The element is moved to the footnote area, a footnote call is left behind in its place, a footnote marker is displayed before the element, and the footnote counter is incremented.

When rendering footnotes, User Agents may apply certain heuristics to improve the presentation. For example, the space between a footnote-call and surrounding text may be adjusted. Another example is the height of the footnote area; it may be heuristically constrained to limit the area that is used for footnotes.

6. Hyphenation

Hyphenation means splitting words to improve the layout of paragraphs. This specifications does not define the exact rules for hyphenation, but describes six properties that influence hyphenation.

6.1. The ‘hyphens’ property

Name: hyphens
Value: none | manual | auto | all
Initial: manual
Applies to: all elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value

Values are:

none
Words are not broken at line breaks, even if characters inside the word suggest line break points.
manual
Words are only broken at line breaks where there are characters inside the word that suggest line break opportunities. Characters can be explicit or conditional.

In Unicode, U+00AD is a conditional "soft hyphen" and U+2010 is an explicit hyphen. Unicode Standard Annex #14 describes the role of soft hyphens in the Unicode Line breaking algorithm.

In HTML, &shy; represents the soft hyphen character which suggests a line break opportunity.

ex&shy;ample.
auto
Words can be broken at appropriate hyphenation points, as determined by characters inside the word, resources listed in ‘hyphenate-resource’, or other UA-dependent resources. Characters inside the word take priority over hyphenation points determined by other resources.
all
All possible hyphenation points, as determined by characters inside the word, resources listed in ‘hyphenate-resource’, or other UA-dependent resources, are marked. The visual appearance of the mark is UA-dependent.

6.2. The ‘hyphenate-resource’ property

Name: hyphenate-resource
Value: none | <uri> [, <uri> ]*
Initial: none
Applies to: all elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value

This property specifies a comma-separated list of external resources that can help the UA determine hyphenation points. If more than one resource is specified, the UA should consult each resource – in turn, from the beginning – until it finds one that is able to determine hyphenation points in a word. The ‘none’ value indicates that no external resources are available. In any case, the UA can also use local resources not listed on this property.

Often, finding the right hyphenate resource is based on knowing the language of the text. The lang attribute is recommended for encoding the language, and the corresponding selector is used in this example:

:lang(dk) { hyphenate-resource: url("hyph_da_DK.dic"), url("hyph_da_NO.dic") }

6.3. The ‘hyphenate-before’ and ‘hyphenate-after’ properties

Name: hyphenate-before
Value: <integer> | auto
Initial: auto
Applies to: all elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value

This property specifies the minimum number of characters in a hyphenated word before the hyphenation character. The ‘auto’ value means that the UA chooses a value that adapts to the current layout.

Unless the UA is able to calculate a better value, it is suggested that ‘auto’ means 2.

Name: hyphenate-after
Value: <integer> | auto
Initial: auto
Applies to: all elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value

This property specifies the minimum number of characters in a hyphenated word after the hyphenation character. The ‘auto’ value means that the UA chooses a value that adapts to the current layout.

Unless the UA is able to calculate a better value, it is suggested that ‘auto’ means 2.

6.4. The ‘hyphenate-lines’ property

Name: hyphenate-lines
Value: no-limit | <integer>
Initial: no-limit
Applies to: all elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value

This property indicates the maximum number of successive hyphenated lines in an element. In some cases, user agents may not be able to honor the specified value. The ‘no-limit’ value means that there is no limit.

6.5. The ‘hyphenate-character’ property

Name: hyphenate-character
Value: auto | <string>
Initial: auto
Applies to: all elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value

This property specifies strings that are shown between parts of hyphenated words. The ‘auto’ value means that the user agent should find an appropriate value.

In Latin scripts, the hyphen character (U+2010) is often used to indicate that a word has been split. Normally, it will not be necessary to set it explicitly. However, this can easily be done:

article { hyphenate-character: "\2010" }

6.6. The ‘hyphenate-last-line-avoid’ property

Name: hyphenate-last-line-avoid
Value: auto | always | column | page | spread
Initial: auto
Applies to: block-level elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value

This property indicates hyphenation behavior at the end of elements, column, pages and spreads. A spread is a set of two pages that are visible to the reader at the same time. Values are:

auto
no restrictions imposed
always
the last full line of the element, or the last line before any column, page, or spread break inside the element should not be hyphenated.
column
the last line before any column, page, or spread break inside the element should not be hyphenated
page
the last line before page or spread break inside the element should not be hyphenated
spread
the last line before any spread break inside the element should not be hyphenated.
p { hyphenate-last-line-avoid: always }
div.chapter {  hyphenate-last-line-avoid: spread }

A paragraph may be formatted like this when ‘hyphenate: auto’ is set:

   This is just a
   simple example
   to show Antar-
   ctica.

With ‘hyphenate-last-line-avoid: always’ one would get:

   This is just a
   simple example
   to        show 
   Antarctica.

   

7. New counter styles

7.1. The ‘super-decimal’ list-style-type

This section will be moved to css3-lists (minutes)

A new list-style-type, ‘super-decimal’, is introduced to better support footnotes. Small, super-script footnote calls are common; the first three numbers have code points in Latin-1 and some font families have even more super-script glyphs. The ‘super-decimal’ keyword allow these font resources to be used and replaces the use of ‘font-size’ and ‘vertical-align’ (which prohibit the use of special-purpose glyphs).

This example specifies that footnote markers should consist of super-script decimal numbers.
::footnote-marker { content: counter(footnote, super-decimal) }

Using super-script glyphs is optional; UAs may also scale and position other glyphs for use in footnote calls.

7.2. Named counter styles

CSS defines a number of predefined list style types for the ‘list-style-type’ property and other places where a list-style-type value is accepted. Some styles repeat the same glyph (e.g., ‘disc’ and ‘circle’) while others have lists of glyphs (e.g., ‘decimal’, and ‘lower-roman’). To increase the range of lists that can be achieved through CSS without adding many new keywords, @counter-style rules are introduced. By using @counter-style, a style sheet can name new counter styles.

An @counter-style rule consists of the keyword ‘@counter-style’, followed by the name of the symbol counter style, followed by a space-separated list of strings.

@counter-style daggers "*" "\2020" "\2021" "\A7" "#";
ol { list-style-type: daggers }
@counter-style ordinal "1st" "2nd" "3rd" "4th";
h1:before { content: counter(chapter, ordinal) " chapter" }

The first string in the list represents number one, the second string represents number two, etc. Outside the range of specified values, the rendering will be as if the ‘decimal’ list style type had been specified.

Consider this example:

@counter-style ordinal "1st" "2nd" "3rd" "4th";
ordered-list { counter-reset: items -1 }
list-item { counter-increment: items 2 }

For a series of list-item elements inside an ordered-list element, the value of the items counter will be -1, 1, 3, 5, 7 etc. Given that the ordinal counter style only defines a counter style for 1, 2, 3, and 4, the list will be numbered "-1", "1st", "3rd", "5", "7" etc.

Named counter styles can be imported through @import statements.

@import url(http://www.example.com/armenian-counters.css); /* defines 'armenian' */
ol { list-style-type: armenian }

7.3. The ‘symbols()’ list-style-type

A new list-style-type with a functional notation is introduced to avoid the indirection of having to name counter styles. The ‘symbols()’ value takes a comma-separated list of strings as arguments.

::footnote-call {
    content: counter(footnote, symbols('*', '+', '!'))
}

Outside the range of specified values, the rendering will be as if the ‘decimal’ list style type had been specified.

This code:
ol { list-style: symbols("*", "\2020", "\2021", "\A7", "#") }
will result in these list-items markers: * † ‡ § # 6 7 8 ...

8. Image resolution

Image resolution, as the term is used in this document, means pixels per physical length, e.g., pixels per inch. Some image formats can record information about the resolution of images. This information can be helpful when determining the actual size of the image in the formatting process. However, the information can also be wrong, in which case it should be ignored. The ‘image-resolution’ and ‘background-image-resolution’ properties are introduced to determine the correct resolution of images.

Name: image-resolution
Value: normal | [ from-image || <dpi> ]
Initial: normal
Applies to: replaced elements and background images?
Inherited: yes
Percentages: N/A
Media: visual
Computed value: as specified value (or, should it be only one value?)

The values are:

normal
The resolution of the image is unknown, and UAs should not use the resolution found in the image. Instead, the image resolution will be found by converting the dimension of the image into CSS pixels.
from-image
The UA must look for the resolution in the image itself. If the image does not have a resolution, the specified <dpi> value is used. If no <dpi> value is specified, the behavior is as if ‘normal’ had been specified.
<dpi>
The value consists of a number with a ‘dpi’ unit identifier. The <dpi> value sets the resolution of the image. In combination with ‘from-image’, the specified dpi is only used if the image does not have a resolution.

This rule specifies that the UA should use the image resolution found in the image itself.

img { image-resolution: from-image }

Using this rule, the image resolution is set to 300dpi and the resolution in the image, if any, is ignored.

img { image-resolution: 300dpi }

These rules both specify that the UA should use the image resolution found in the image itself. If the image has no resolution, the resolution is set to 300dpi.

img { image-resolution: from-image 300dpi }
img { image-resolution: 300dpi from-image }

9. Page marks and bleed area

The ‘marks’ property from [CSS2] is part of this specification.

Name: marks
Value: [ crop || cross ] | none
Initial: none
Applies to: page context
Inherited: no
Percentages: N/A
Media: visual, paged
Computed value: specified value

This property adds crop and/or cross marks to the document. Crop marks indicate where the page should be cut. Cross marks are used to align sheets.

Crop marks and cross marks are printed outside the page box. To have room to show crop and cross marks, the final pages will have to be somewhat bigger than the page box.

To set crop and cross marks on a document, this code can be used:

@page { marks: crop cross }
Name: bleed
Value: <length>
Initial: 6pt
Applies to: page context
Inherited: no
Percentages: refer to width of page box
Media: visual
Computed value: as specified value

This property specifies the extent of the page bleed area outside the page box. This property only has effect if crop marks are enabled.

10. Bookmarks

Some document formats have the capability of holding bookmarks. Bookmarks are typically shown outside the document itself, often a tree-structured and clickable table of contents to help navigate in the electronic version of the document. To generate bookmarks, these properties are defined:

Name: bookmark-level
Value: none | <integer>
Initial: none
Applies to: all elements
Inherited: no
Percentages: N/A
Media: all
Computed value: specified value

This property describes what level a certain bookmark has in a hierarchical bookmark structure. The highest level is ‘1’, then ‘2’, ‘3’ etc.

h1 { bookmark-level: 1 }
h2 { bookmark-level: 2 }
h3 { bookmark-level: 3 }
Name: bookmark-label
Value: content() | attr() | <string>
Initial: content()
Applies to: all elements
Inherited: no
Percentages: N/A
Media: all
Computed value: specified value

This property specifies the label of the bookmark, i.e., the text that will represent the bookmark in the bookmark structure.

a { bookmark-label: attr(title, string) }
h1 { bookmark-label: content() }
h2 { bookmark-label: content(before) }
#frog { bookmark-label: "The green frog" }
Name: bookmark-target
Value: none | <uri> | <attr>
Initial: none
Applies to: all elements
Inherited: no
Percentages: N/A
Media: all
Computed value: For URI values, the absolute URI; for attr() values, the resulting URI or string; for other keywords, as specified.

This property specifies the target of the bookmark link.

.bookmark {
   bookmark-label: attr(title, string);
   bookmark-target: attr(href, url);
}
...
<a class="bookmark" title="The green pear" href="#pears"/>
.exable { bookmark-label: url(http://www.example.com) }
Name: bookmark-state
Value: open | closed
Initial: open
Applies to: block-level elements
Inherited: no
Percentages: N/A
Media: all
Computed value: specified value

This property describes the initial state of a bookmark.

* { bookmark-state: closed }
#open { bookmark-state: open }

11. CMYK colors

Printers do not use RGB colors, they (often) use CMYK: cyan, magenta, yellow and black. The ‘device-cmyk()’ functional value allows style sheets to express device-dependent CMYK colors.

h3 { color: device-cmyk(0.8, 0.5, 0.0, 0.3) }

The values representing the colors are between ‘0’ and ‘1’. Values outside this range are clipped.

It is not expected that screen-centric user agents support CMYK colors and it is therefore important that existing CSS color values can be combined with CMYK colors.

h3 {
  color: red;
  color: device-cmyk(0.5, 0.1, 0.0, 0.2);
}

User Agents that do not understand the device-cmyk() value, will use the first color (red). User agents that understand device-cmyk() will use the second color (which is bluish).

12. Styling blank pages

Blank pages that appear as a result of forced page breaks can be styled with the :blank pseudo-class.

In this example, forced page break may occur before h1 elements.

h1 { page-break-before: left }

@page :blank {
  @top-center { content: "This page is intentionally left blank" }
}

The :blank pseudo-class has the same specificity as the :first pseudo-class. A page matched by :blank will still be matched by other page selectors.

If headers have been specified on all right pages, a blank right page will be matched by both :blank and :right. Therefore, margin boxes set on right pages will have to be removed unless they are wanted on blank pages. Here is an example where the top center header is removed from blank pages, while the page number remains:

h1 { page-break-before: left }

@page :blank {
  @top-center { content: none }
}

@page :right {
  @top-center { content: "Preliminary edition" }
  @bottom-center { content: counter(page) }
}

Due to the higher specificity of :blank over :right, the top center header is removed even if content: none comes before content: "Preliminary edition".

13. Paged presentations

Printed publications are paged, while screen-based presentations of web pages are most often presented in a continous manner with a scrollbar on the side. There are reasons to believe that screen-based presentations also could benefit from using paged presentations. There is nothing in web specifications that prevent browsers from adding a page-based mode today. However, most web content is authored and styled with a continous presentation in mind. This could change if it becomes possible to describe paged presentations in style sheets. This section is an attempt to do so.

To support paged presentations, four new values are added to the ‘overflow’ property:

paged-x
overflow content is paged, and the pages are laid out along the x axis, in the x axis component of the writing direction
paged-y
overflow content is paged, and the pages are laid out along the y axis, in the the y axis component of the writing direction
paged-x-controls
as ‘paged-x’, but with added UA-specific controls to change pages
paged-y-controls
as ‘paged-y’, but with added UA-specific controls to change pages

In this example, the root element is constrained to have the same height as the initial containing block. Overflow content will be laid out on subsequent pages along the x axis. In LTR languages, this means right; in RTL languages this means left; in vertical-rl this means right.

  html { 
    overflow: paged-x;
    height: 100%;
  }

In this example, one element within the document is paged, and controls are added so that users can navigate from one page to the next. As such, the controls have the same effect as scrollbars in continous presentations.

  #content { 
    overflow: paged-x-controls;
    height: 400px;
  }

Paged navigation within a page (as described above), can also be naturally extended to navigation between web documents. To support this, a new @-rule is proposed: @navigation. The purpose of @navigation is to describe which documents the user can navigate to by moving up, right, down, or left from the current document.

Four new properties are allowed inside @navigation: nav-up, nav-right, nav-bottom, nav-right.

The name of the properties inside @navigation are borrowed from CSS3 Basic User Interface Module.

The properties accept these values:

link-rel()
the function takes one argument, which refers to the rel attribute of the link element
<link rel=index href="../index.html">
<link rel=previous href=g3.html>
<link rel=next href=g1.html>
...
@-o-navigation {
  nav-up: link-rel(index); 
  nav-left: link-rel(previous); 
  nav-right: link-rel(next); 
}

The "link-rel" name is a bit academic, perhaps the "go()" name can be used instead?

go()
The function takes one argument: back, which takes the user one step back in history.
@navigation {
  nav-left: go(back); 
}
url-doc()
The funcation takes one argument: a URL. Relative URLs are relative to the document, not to the style sheet.
@navigation {
  nav-up: url-doc(..);
  nav-down: url-doc(a1.html);
}
url()
The funcation takes one argument: a URL. Relative URLs are relative to the style sheet.
@navigation {
  nav-up: url(..);
  nav-down: url(a1.html);
}

Combined with the @document-rule, navigation maps can be described:

@document url("http://example.com/foo") {
  @navigation {
    nav-right: link-rel(next);
  }
}

@document url("http://example.com/bar") {
  @navigation {
    nav-upt: link-rel(next);
  }
}

14.1. Page shift effects

To describe page shift effects, four new properties inside @navigation are proposed: nav-up-shift, nav-right-shift, nav-down-shift, nav-left-shift. These properties take one of several keyword values:

pan
pans to the new page; this is the initial value
turn
turns the page, like soft book pages do
flip
flips the page, like stiff cardbord
fold
the old page folds, like an accordion

The proposed keyword values are loosely described. Are there better ways to describe transitions?

@navigation {
   nav-up-shift: pan;
   nav-down-shift: flip;
}

15. Page floats

Images and figures are sometimes displayed at the top or bottom of pages and columns. This specificaton adds new keywords on the ‘float’ property which, in combination with integer values on ‘column-span’ and the new ‘float-modifier’, provides support for common paper-based layouts.

Four new keywords on ‘float’ have been added:

top
the box is floated to the top of the natural column
bottom
the box is floated to the bottom of the natural column
top-corner
the box is floated to the top of the last column (in the inline direction) that fits inside the multicol element on the same page.
bottom-corner
similar to ‘top-corner’, exept the box is floated to the bottom
snap
same as ‘top’ if the box is naturally near the top; same as ‘bottom’ if the box is naturally near the bottom. The ‘widows’/‘orphans’ properties may be consulted to determine if the box is near the top/bottom.

These new keywords only apply in paged media; in continous media declarations with these keywords are ignored.

Float figure to top of natural column:

.figure { float: top; display: block; }
.figure { float: top; width: 50% }

Float figure to top of the natural column, spanning all columns:

.figure { float: top; column-span: all }

Float figure to top/bottom of the last column of the multicol element on that page:

.figure { float: top-corner }

The ‘column-span’ property is extended with integer values so that elements can span several columns. If the specified integer value is equal to, or larger than the number of columns in the multicol element, the number of columns spanned will be the same as if ‘column-span: all’ had been specified.

In combination with ‘column-span’, the figure is floated to the top corner of the multicol element on that page:

.figure { float: top-corner; column-span: 2; width: 100% }
body { columns: 3 }
img.A { column-span: 2; width: 100% }
.one { column-span: 2 }

15.1. Float modifiers

These new values on ‘float’ can be combined with the other values:

next-page
In paged media, float box to the next page. The first column of the multicol element on the next page is considered to be the natural column for boxes affected by this value.
next-column
In paged media, float box to the next column.
unless-room
Only float the box if it otherwise would have lead to a column or page break

Can this value be combined with all other values? E.g., does "left unless-room" make sense?

intrude
The element may intrude neighboring columns; if the element is not in a multi-column element, this keyword has no effect.
.figure { float: top next-column }
.figure { float: top unless-room }
.figure { float: top-corner next-page }
img { float: left intrude; width: 120%;  }

In this example, the image is wider than the column and will therefore intrude into the neighboring column. At the bottom of the middle column is a long word that is clipped in the middle of the column gap.

Would it be better to have these modifiers on a new property, e.g. ‘float-adjust’. This way, the ‘float’ property would only need to take one value.

15.2. Floating inside and outside pages

Two allow content to flow to the inside and outside of a page, these keywords are added to the ‘float’ property:

inside
On a right page, this value is synonymous with ‘left’. On a left page, this value is synonymous with ‘right’.
outside
On a left page, this value is synonymous with ‘left’, On a right page, this value is synonymous with ‘right’.
.figure { float: outside }

16. Aligning baselines in multi-column layouts

In multi-column layouts, baselines are typically aligned between adjacent columns. This gives the presentation a visual rythm, and text in the end of the columns will be alignend. To support this, a new value on the line-box-contain property is defined: ‘line-grid’ (or, perhaps, ‘gap’, ‘crack’, ‘snap’, ‘snap-gap’, ‘void’, ‘grid’, ‘snap-to-grid’).

The value means that the height of the line in which the element occurs should be rounded up to the smallest multiple of the used ‘line-height’ value on the containing block.

In this example, the stacking height of div.figure would be 30px (2 * 15px)

div.multicol { line-height: 15px }
div.figure { height: 20px; line-box-contain: block inline replaced line-grid }

The line-box-contain property is defined in CSS3 module: line.

A similar idea — ‘line-stacking-strategy: grid-height’ — was proposed in a previous version of the CSS3 line module. The ‘line-stacking-strategy’ property is used in XSL.

17. Page selection: nth()

In CSS 2.0, first, left and right pages can be selected. This specification adds support for selecting the nth page in the document, or the nth named page.

This example sets the background color of the second page in the document:

@page :nth(2) { 
  background: green;
}

   

This example sets the background color of the second page of all chapters in a document:

@page chapter {
  background: yellow;
}
@page chapter:nth(2) { 
  background: green;
}
div.chapter {
  page: chapter;
}

   

The arguments to the nth() functional notation is the same as for the nth-child() pseudo-class.

@page chapter:nth(2n+1) { 
  background: green;
}

Even when a named page is not defined through an @page name { .. } construct, the name can still be used with :nth().

Even when the first line is commented out, the second page of all chapters in the document will be green.

/* @page chapter { ... } */

@page chapter:nth(2) {
  background: green;
}

div.chapter { page: chapter }

18. Conformance

19. Appendix A: Default style sheet

@page {
  counter-reset: footnote;
  @footnote {
    counter-increment: footnote;
    float: page bottom;
    width: 100%;
    height: auto;
  }
}

::footnote-call {
  counter-increment: footnote;
  content: counter(footnote, super-decimal); 
}
::footnote-marker {
  content: counter(footnote, super-decimal); 
}


h1 { bookmark-level: 1 }
h2 { bookmark-level: 2 }
h3 { bookmark-level: 3 }
h4 { bookmark-level: 4 }
h5 { bookmark-level: 5 }
h6 { bookmark-level: 6 }

Acknowledgments

This document has been improved by Bert Bos, Michael Day, Melinda Grant, David Baron, Markus Mielke, Steve Zilles, Ian Hickson, Elika Etemad, Laurens Holst, Mike Bremford, Allan Sandfeld Jensen, Kelly Miller, Werner Donné, Tarquin (Mark) Wilton-Jones, Michel Fortin, Christian Roth, Brady Duga, Del Merritt, Ladd Van Tol, Tab Atkins Jr., Jacob Grundtvig Refstrup, James Elmore, Ian Tindale, Murakami Shinyu, Paul E. Merrell, Philip Taylor.

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

Other references

[CSS2]
Ian Jacobs; et al. Cascading Style Sheets, level 2 (CSS2) Specification. 11 April 2008. W3C Recommendation. URL: http://www.w3.org/TR/2008/REC-CSS2-20080411
[CSS3PAGE]
Håkon Wium Lie; Melinda Grant. CSS3 Module: Paged Media. 10 October 2006. W3C Working Draft. (Work in progress.) URL: http://www.w3.org/TR/2006/WD-css3-page-20061010

Index

Property index

Property Values Initial Applies to Inh. Percentages Media
bleed <length> 6pt page context no refer to width of page box visual
bookmark-label content() | attr() | <string> content() all elements no N/A all
bookmark-level none | <integer> none all elements no N/A all
bookmark-state open | closed open block-level elements no N/A all
bookmark-target none | <uri> | <attr> none all elements no N/A all
hyphenate-after <integer> | auto auto all elements yes N/A visual
hyphenate-before <integer> | auto auto all elements yes N/A visual
hyphenate-character auto | <string> auto all elements yes N/A visual
hyphenate-last-line-avoid auto | always | column | page | spread auto block-level elements yes N/A visual
hyphenate-lines no-limit | <integer> no-limit all elements yes N/A visual
hyphenate-resource none | <uri> [, <uri> ]* none all elements yes N/A visual
hyphens none | manual | auto | all manual all elements yes N/A visual
image-resolution normal | [ from-image || <dpi> ] normal replaced elements and background images? yes N/A visual
marks [ crop || cross ] | none none page context no N/A visual, paged
string-set [[ <identifier> <content-list>] [, <identifier> <content-list>]* ] | none none all elements no N/A all