CSS Generated Content for Paged Media Module

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. Paged media can be printed, or presented on screens.

Status of this document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

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 WD contains functionality that the CSS WG finds interesting and useful. In general, the earlier a feature appears in this draft, the more stable it is. Significant changes in functionality and syntax must be expected from paged presentations and onwards. Also, functionality described in this module may be moved to other modules. Since the previous WD, hyphenation has been moved to css3-text and the super-decimal list-style-type value has been moved to css3-lists. Named counter styles and the symbols() list-style-type value should also appear in a future css3-lists WD.

Table of contents

• 1. Introduction
• 2. Running headers and footers
  • 2.1. Named strings
    • 2.1.1. Setting named strings: the ‘string-set’ property
    • 2.1.2. Using named strings
  • 2.2. Running elements
• 3. Leaders
• 4. Cross-references
  • 4.1. The ‘target-counter’ and ‘target-counters’ values
  • 4.2. The ‘target-text’ value
• 5. Footnotes
  • 5.1. Turning elements into footnotes
  • 5.2. The footnote area
  • 5.3. Footnote calls
  • 5.4. Footnote markers
  • 5.5. Counting footnotes
  • 5.6. Laying out footnotes
  • 5.7. Footnote magic
• 6. Page marks and bleed area
• 7. Bookmarks
• 8. CMYK colors
• 9. Styling blank pages
• 10. Paged presentations
• 11. Navigation between pages
  • 11.1. Page shift effects
• 12. Page floats
  • 12.1. Float modifiers
  • 12.2. Floating inside and outside pages
  • 12.3. Multi-column float intrusion
  • 12.4. The ‘float-offset’ property
• 13. The ‘first-page’ pseudo-element
• 14. Selecting columns and pages
• 15. Conformance
• 16. Appendix A: Default style sheet
• Acknowledgments
• References
  • Normative references
  • Other references
• Index
• Property index

1. Introduction

(This section is not normative.)

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

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.

h1 { string-set: title content() }

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

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

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;
}

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

dt { string-set: index content(first-letter) }

title { 
  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:

• ‘start’: the named string's entry value for that page is used.
• ‘first’: the value of the first assignment is used. If there is no assignment on the page, the start value is used. ‘first’ is the default value.
• ‘last’: the named string's exit value for that page is used
• ‘first-except’: similar to ‘first’, except on the page where the value was assigned. On that page, the empty string is used.

The assignment is considered to take place on the first page where a content box representing the element occurs. If the element does not have any content boxes (e.g., if ‘display: none’ is set), the assignment is considered to take place on the page where the first content box would have occured if the element had been in the normal flow.

@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() }

@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, and the place of the assignments are the same.

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

<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>

...
<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>
...

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 two values. The first describes the glyph pattern that makes up the leader. These values are allowed:

• leader(dotted)
• leader(solid)
• leader(space)
• leader(<string>)

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

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’.

The second value describes the alignment of the leader. These values are allowed:

align

attempt to align corresponding glyphs from the leader pattern between consecutive lines. This is the default value.

start

align leader string with the start

end

align leader string with the end

center

center leader string

string-space

add space between strings to take up all available space

letter-space

add space between letters (both inside the string, and at the start/end of the string) to take up all available space

heading::after { content: leader(dotted, align) }
heading::after { content: leader(dotted, start) }
heading::after { content: leader(dotted, end) }
heading::after { content: leader(dotted, center) }
heading::after { content: leader(dotted, string-space) }
heading::after { content: leader(dotted, letter-space) }

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.

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

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.

<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>

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

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

cite { text-wrap: suppress }

cite { white-space: nowrap }

  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.

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

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.

<p>See <a href="#chx">this chapter</a> for an in-depth evaluation.
...
<h2 id="chx">A better way</h2>

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:

• one new value on the ‘float’ property: ‘footnote’
• one new page area: ‘@footnote’
• two new pseudo-elements: ‘::footnote-call’ and ‘::footnote-marker’
• one predefined counter: ‘footnote’
• one new value on the ‘content’ property: ‘target-pull()’
• border segments

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

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

A sentence consists of words. ¹

¹ Most often.

<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.

A sentence consists of words¹.

¹ Most often.

<p>Sorry, <span title="This is, of course, a lie.">we're closing for lunch</span>.

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.

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

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?

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

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

@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 }

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.

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

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.

::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.

@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. Page marks and bleed area

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

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.

@page { marks: crop cross }

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

7. 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:

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 }

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" }

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"/>

This property describes the initial state of a bookmark.

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

8. 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);
}

9. Styling blank pages

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

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.

h1 { page-break-before: left }

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

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

10. 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-style’ 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

Is "paginated" a better word?

Should controls be specified on a separate property, or on an attribute (like HTML's video element)?

Should the axis (x/y) be specified on a separate property?

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

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

A paged container cannot be split over multiple columns.

11. Navigation between pages

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); 
}

This functionality relies on semantics in HTML and CSS. Other languages may have other other ways to describe such semantics. One possible solution for other languages is "link[rel=index] { nav-up: attr(href) }"

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);
}

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

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

11.1. 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;
}

12. 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% }

.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 }

12.1. Float modifiers

These values on ‘float’ can be combined with one of ‘top’/‘bottom’/‘top-corner’/‘bottom-corner’ 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.

.figure { float: top-corner next-page }

next-column

In paged media, float box to the next column.

.figure { float: top next-column }
.figure { float: next-column top }

unless-room

Only float the box if it otherwise would have lead to a column or page break.

.figure { float: top unless-room }

left/right

‘left’/‘right’ can be used in combination with ‘top’/‘bottom’/‘top-corner’/‘bottom-corner’ to allow other content to flow around the box.

.figure { float: top right; width: 60% }

12.2. 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 }

12.3. Multi-column float intrusion

A new value on ‘float’ is introduced to support intrusion in columns:

intrude

The element may intrude neighboring columns; if the element is not in a multi-column element, this keyword has no effect.

The ‘intrude’ value only works in combination with one of these keywords: ‘left’/‘right’/‘top’/‘bottom’/‘top-corner’/‘bottom-corner’.

img { float: left intrude; width: 120%;  }

12.4. The ‘float-offset’ property

This property pushes a float in opposite direction of the where it has been floated with ‘float’. If one value is specified, it is the horizontal offset. If two values are specified, the first is the horizontal and the second is the vertical offset. If no vertical value has been specified, the vertical offset is set to zero.

Negative values are allowed; a negative values will push the float in the same direction as it has been floated with ‘float’

The float will never be pushed outside the content edges of the multicol element due to a setting on ‘float-offset’.

Percentage values refer to the width/height of the float plus a fraction of the column gap.

Floats that are moved into other columns with this property intrudes.

img { 
  float: top right;
  float-offset: -50% 3em;
  width: 120%;
}

img {
  float: top right;
  float-offset: -80% 2em;
  width: 100%;
}

Would it make more sense to not specify the opposite direction, but the "forward" direction?

13. The ‘first-page’ pseudo-element

The ‘first-page’ pseudo-element is used to apply styling to the part of an element that ends up on the starting page for that element. If the whole element appears on the starting page, ‘first-page’ applies to the whole element. The following properties apply to :first-page pseudo-elements: column properties, background properties, margin properties, border properties, and padding properties. UAs may apply other properties as well.

  div.chapter { columns: 2 }
  div.chapter::first-page { columns: 1 }

  div.chapter { break-before: left }
  div.chapter::first-page { padding-left: 4em }

14. Selecting columns and pages

This is sketchy.

Pseudo-elements are introduced to apply styling to the part of an element that ends up on a certain page of column of that element. The ‘column(n)’ pseudo-element selects columns, and the ‘page(n)’ psedo-element select columns.

div.chapter::column(3)           /* the third column of the element */
div.chapter::column(2n)          /* all even columns of the element */
div.chapter::page(2)             /* second page of the element */
div.chapter::page-column(2,2)    /* second column on second page */
div.chapter::page(2)::column(2)  /* second column, but only if it appears on the second page */

15. Conformance

TBD

16. 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, Brad Kemper, Peter Linss, Daniel Glazman, Tantek Çelik, Florian Rivoal, Alex Mogilevsky.

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

• bleed, 6.
• bookmark-label, 7.
• bookmark-level, 7.
• bookmark-state, 7.
• bookmark-target, 7.
• float-offset, 12.4.
• marks, 6.
• named strings, 2.
• running elements, 2.
• string-set, 2.1.1.

Property index