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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html lang=en>
<head profile="http://dublincore.org/documents/2008/08/04/dc-html/ ">
<title> CSS Paged Media Module Level 3</title>
<link href="http://purl.org/dc/terms/" rel=schema.dc>
<link href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
rel=dc.rights>
<meta content=" CSS Paged Media Module Level 3" name=dc.title>
<meta content=text name=dc.type>
<meta content=2013-03-20 name=dc.date>
<meta content="Melinda Grant" name=dc.creator>
<meta content="Håkon Wium Lie" name=dc.creator>
<meta content="Elika J. Etemad" name=dc.creator>
<meta content="Simon Sapin" name=dc.creator>
<meta content=W3C name=dc.publisher>
<meta content="http://dev.w3.org/csswg/css3-page/" name=dc.identifier>
<meta content="text/html; charset=utf-8" http-equiv=Content-Type>
<link href="../default.css" rel=stylesheet type="text/css">
<link href="http://www.w3.org/StyleSheets/TR/W3C-ED.css" rel=stylesheet
type="text/css">
<style type="text/css">
.keyword { font-weight:bold }
.equation { padding: 2% }
table.equation {text-align:center}
td, th { vertical-align: top }
pre { font-size: 1em; }
#margin-values { border-collapse: collapse; }
#margin-values td,
#margin-values th
{
padding: 0.2em;
border: thin solid black;
}
.property-list
{
border: 1px solid black;
padding: .2em;
margin-top: 2em;
}
.property-list td
{
border: 1px solid black;
padding: .1em;
}
.e
133E
ditorial
{
display: block;
font-family: arial, helvetica, sans-serif;
font-size: 80%;
margin-left: .5in;
margin-right: 1in ;
padding: 0.125in;
background: #FFFFDD ;
}
.editorial:after { content: "Ed."}
.RFC2119
{
text-transform: lowercase;
font-style: italic
}
em em.RFC2119
{
text-transform: lowercase;
font-style: normal
}
table.page-sizes
{
border: thin solid;
margin-top: 1.5em;
}
table.page-sizes td
{
border: thin solid;
padding: .5em;
}
table.page-sizes th
{
border: thin solid;
padding: .5em;
background: #ffffaa;
}
</style>
<body class=h-entry>
<div>
<div class=head> <!--begin-logo-->
<p><a href="http://www.w3.org/"><img alt=W3C height=48
src="http://www.w3.org/Icons/w3c_home" width=72></a> <!--end-logo-->
<h1 class=p-name>CSS Paged Media Module Level 3</h1>
<h2 class="no-num no-toc" id=w3c-working>Editor's Draft <span
class=dt-updated><span class=value-title title=20130320>20 March
2013</span></span></h2>
<dl>
<dt>This version:
<dd><a class=u-url
href="http://dev.w3.org/csswg/css3-page/">http://dev.w3.org/csswg/css3-page/</a></dd>
<!-- <dd><a class="u-url" href="http://dev.w3.org/csswg/css3-page/">http://www.w3.org/TR/2013/WD-css3-page-20130320</a></dd> -->
<dt>Latest version:
<dd><a
href="http://www.w3.org/TR/css3-page/">http://www.w3.org/TR/css3-page/</a>
<dt>Editor’s Draft:
<dd><a
href="http://dev.w3.org/csswg/css3-page/">http://dev.w3.org/csswg/css3-page/</a>
<dt>Previous version:
<dd><a href="http://www.w3.org/TR/2013/WD-css3-page-20130314/"
rel=previous>http://www.w3.org/TR/2013/WD-css3-page-20130314/</a>
<dt>Issue Tracking:
<dd><a href="http://www.w3.org/Style/CSS/Tracker/products/13"
rel=issues>http://www.w3.org/Style/CSS/Tracker/products/13</a>
<dt>Feedback:
<dd><a
href="mailto:www-style@w3.org?subject=%5Bcss3-page%5D%20feedback">www-style@w3.org</a>
with subject line “<kbd>[css3-page] <var>… message topic
…</var></kbd>” (<a
href="http://lists.w3.org/Archives/Public/www-style/"
rel=discussion>archives</a>)
<dt>Editors:
<dd class="p-author h-card vcard"> <span class="p-name fn">Melinda
Grant</span>, <span class="p-org org">Hewlett-Packard</span>
<dd class="p-author h-card vcard"> <span class="p-name fn">Håkon Wium
Lie</span>, <span class="p-org org">Opera Software</span>
<dd class="p-author h-card vcard"> <span class="p-name fn">Elika J.
Etemad</span>, <span class="p-org org">Mozilla</span>
<dd class="p-author h-card vcard"> <span class="p-name fn">Simon
Sapin</span>, <span class="p-org org">Kozea</span>
</dl>
<!--begin-copyright-->
<p class=copyright><a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
rel=license>Copyright</a> © 2013 <a href="http://www.w3.org/"><abbr
title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> (<a
href="http://www.csail.mit.edu/"><abbr
title="Massachusetts Institute of Technology">MIT</abbr></a>, <a
href="http://www.ercim.eu/"><abbr
title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>,
<a href="http://www.keio.ac.jp/">Keio</a>, <a
href="http://ev.buaa.edu.cn/">Beihang</a>), All Rights Reserved. W3C <a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
<a
href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
and <a
href="http://www.w3.org/Consortium/Legal/copyright-documents">document
use</a> rules apply.</p>
<!--end-copyright--></div>
<hr title="Separator for header">
<h2 class="no-num no-toc" id=abstract>Abstract</h2>
<p> <span class=p-summary> This module describes the page model that
partitions a flow into pages. It builds on the <a
href="http://www.w3.org/TR/CSS21/box.html">Box model module</a> and
introduces and defines the page model and paged media. It adds
functionality for pagination, page margins, page size and orientation,
headers and footers, widows and orphans, and image orientation. Finally
it extends generated content to enable page numbering and running headers
/ footers. </span></p>
<!-- "Status of this document" -->
<h2 class="no-num no-toc" id=status>Status of this Document</h2>
<!--begin-status-->
<p>This is a public copy of the editors' draft. It is provided for
discussion only and may change at any moment. Its publication here does
not imply endorsement of its contents by W3C. Don't cite this document
other than as work in progress.
<p>The (<a
href="http://lists.w3.org/Archives/Public/www-style/">archived</a>)
public mailing list <a
href="mailto:www-style@w3.org?Subject=%5Bcss3-page%5D%20PUT%20SUBJECT%20HERE">
www-style@w3.org</a> (see <a
href="http://www.w3.org/Mail/Request">instructions</a>) is preferred for
discussion of this specification. When sending e-mail, please put the
text “css3-page” in the subject, preferably like this:
“[<!---->css3-page<!---->] <em>…summary of comment…</em>”
<p>This document was produced by the <a
href="http://www.w3.org/Style/CSS/members">CSS Working Group</a> (part of
the <a href="http://www.w3.org/Style/">Style Activity</a>).
<p>This document was produced by a group operating under the <a
href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February
2004 W3C Patent Policy</a>. W3C maintains a <a
href="http://www.w3.org/2004/01/pp-impl/32061/status"
rel=disclosure>public list of any patent disclosures</a> made in
connection with the deliverables of the group; that page also includes
instructions for disclosing a patent. An individual who has actual
knowledge of a patent which the individual believes contains <a
href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
Claim(s)</a> must disclose the information in accordance with <a
href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
6 of the W3C Patent Policy</a>.</p>
<!--end-status-->
<h2 class="no-num no-toc" id=contents>Table of Contents</h2>
<!--begin-toc-->
<ul class=toc>
<li><a href="#intro"><span class=secno>1. </span>Introduction</a>
<li><a href="#conformance"><span class=secno>2. </span>Conformance</a>
<li><a href="#page-terms"><span class=secno>3. </span>Page
Terminology</a>
<li><a href="#page-model"><span class=secno>4. </span>The Page Model</a>
<ul class=toc>
<li><a href="#painting"><span class=secno>4.1. </span> Page Backgrounds
and Painting Order</a>
<li><a href="#content-outside-box"><span class=secno>4.2.
</span>Content outside the page box</a>
<li><a href="#progression"><span class=secno>4.3. </span>Page
Progression</a>
</ul>
<li><a href="#page-selector-and-context"><span class=secno>5. </span>
Page Selectors and the Page Context</a>
<ul class=toc>
<li><a href="#at-page-rule"><span class=secno>5.1. </span> The @page
Rule</a>
<li><a href="#page-selectors"><span class=secno>5.2. </span>Page
selectors</a>
<ul class=toc>
<li><a href="#spread-pseudos"><span class=secno>5.2.1. </span> Spread
pseudo-classes: ‘<code class=css>:left</code>’, ‘<code
class=css>:right</code>’</a>
<li><a href="#first-pseudo"><span class=secno>5.2.2. </span>
First-page pseudo-class: ‘<code class=css>:first</code>’</a>
<li><a href="#blank-pseudo"><span class=secno>5.2.3. </span>
Blank-page pseudo-class: ‘<code class=css>:blank</code>’</a>
</ul>
<li><a href="#syntax-page-selector"><span class=secno>5.3. </span>@page
rule grammar</a>
<li><a href="#cascading-and-page-context"><span class=secno>5.4.
</span>Cascading in the page context</a>
</ul>
<li><a href="#margin-boxes"><span class=secno>6. </span>Page-Margin
Boxes</a>
<ul class=toc>
<li><a href="#margin-at-rules"><span class=secno>6.1. </span>At-rules
for page-margin boxes</a>
<li><a href="#populating-margin-boxes"><span class=secno>6.2.
</span>Populating page-margin boxes</a>
<li><a href="#margin-dimension"><span class=secno>6.3. </span>Computing
Page-margin Box Dimensions</a>
<ul class=toc>
<li><a href="#margin-box-terms"><span class=secno>6.3.1.
</span>Page-Margin Box Layout Terminology</a>
<li><a href="#variable-sizing"><span class=secno>6.3.2. </span>
Page-Margin Box Variable Dimension Computation Rules</a>
<ul class=toc>
<li><a href="#variable-auto-margins"><span class=secno>6.3.2.1.
</span>Margins</a>
<li><a href="#variable-auto-sizing"><span class=secno>6.3.2.2.
</span>Resolving ‘<code class=css>auto</code>’ widths</a>
<li><a href="#variable-minmax"><span class=secno>6.3.2.3.
</span>Handling ‘<code class=property>min-width</code>’ and
‘<code class=property>max-width</code>’</a>
<li><a href="#variable-position"><span class=secno>6.3.2.4.
</span>Positioning</a>
<li><a href="#variable-mapping"><span class=secno>6.3.2.5.
</span>Boxes on other sides</a>
</ul>
<li><a href="#fixed-sizing"><span class=secno>6.3.3.
</span>Page-Margin Box Fixed Dimension Computation Rules</a>
</ul>
<li><a href="#margin-box-ex"><span class=secno>6.4. </span>Page-margin
box examples</a>
</ul>
<li><a href="#page-properties"><span class=secno>7. </span>Page
Properties</a>
<ul class=toc>
<li><a href="#page-based-counters"><span class=secno>7.1.
</span>Page-based counters</a>
<li><a href="#margin-text-alignment"><span class=secno>7.2.
</span>Page-margin boxes and default values</a>
</ul>
<li><a href="#page-size"><span class=secno>8. </span>Page Size</a>
<ul class=toc>
<li><a href="#page-size-prop"><span class=secno>8.1. </span>Page size:
the ‘<code class=property>size</code>’ property</a>
<ul class=toc>
<li><a href="#some-examples"><span class=secno>8.1.1. </span>Some
examples:</a>
<li><a href="#page-size-media-query"><span class=secno>8.1.2.
</span>Media Queries</a>
</ul>
<li><a href="#renderingpages"><span class=secno>8.2. </span>Rendering
page boxes that do not fit a page sheet</a>
<li><a href="#positioning-page-box"><span class=secno>8.3.
</span>Positioning the page box on the sheet</a>
</ul>
<li><a href="#page-breaks"><span class=secno>9. </span> Page Breaks </a>
<ul class=toc>
<li><a href="#using-named-pages"><span class=secno>9.1. </span>Using
named pages: ‘<code class=property>page</code>’</a>
</ul>
<li><a href="#image-properties"><span class=secno>10. </span>Image
Properties</a>
<li class=no-num><a href="#properties-list">Appendix A: Applicable CSS2.1
Properties</a>
<ul class=toc>
<li class=no-num><a href="#page-property-list"> CSS 2.1 Properties that
apply within the page context</a>
<li class=no-num><a href="#margin-property-list"> CSS 2.1 properties
that apply within the margin contexts</a>
</ul>
<li class=no-num><a href="#transfer-possibilities">Appendix B: Transfer
Possibilities</a>
<li class=no-num><a href="#changes">Changes</a>
<li class=no-num><a href="#references">References</a>
<ul class=toc>
<li class=no-num><a href="#normative-references">Normative
References</a>
<li class=no-num><a href="#informative-references">Informative
References</a>
</ul>
</ul>
<!--end-toc--> <!-- "Introduction" -->
<h2 id=intro><span class=secno>1. </span>Introduction</h2>
<p>Paged media (e.g., paper, transparencies, photo album pages, pages
displayed on computer screens as printed output simulations) differ from
<a
href="http://www.w3.org/TR/CSS2/media.html#continuous-media-group">continuous
media</a> in that the content of the document is split into one or more
discrete static display surfaces. To handle pages, CSS3 Paged Media
describes how:
<ul>
<li><a href="#page-breaks">page breaks</a> are created and avoided;
<li>the page properties such as size, orientation, margins, border, and
padding are specified;
<li>headers and footers are established within the page margins;
<li>content such as page counters are placed in the headers and footers;
and
<li>orphans and widows can be controlled.
</ul>
<p>This module defines a <a href="#page-model">page model</a> that
specifies how a document is formatted within a rectangular area, called
the <a href="#page-box-page-rule">page box</a>, that has finite width and
height.
<p>Although CSS3 does not specify how user agents transfer page boxes to
sheets, it does include certain mechanisms for telling user agents about
the intended page sheet <a href="#page-size">size and orientation</a>. In
the general case, CSS3 assumes that one page box will be transferred to
one surface of similar size.
<p>All properties defined in this specification also accept the <a
href="http://www.w3.org/TR/CSS21/cascade.html#value-def-inherit">inherit</a>
keyword as their value, but for readability it has not been listed
explicitly.
<h2 id=conformance><span class=secno>2. </span>Conformance</h2>
<p>All of the text in this specification is normative except sections
explicitly marked as non-normative, examples, and notes. The keywords
"<em class=RFC2119>MUST</em>", "<em class=RFC2119>SHALL</em>", "<em
class=RFC2119>MUST NOT</em>", "<em class=RFC2119>SHALL NOT</em>", "<em
class=RFC2119>REQUIRED</em>", "<em class=RFC2119>SHOULD</em>", "<em
class=RFC2119>SHOULD NOT</em>", "<em class=RFC2119>RECOMMENDED</em>",
"<em class=RFC2119>MAY</em>", and "<em class=RFC2119>OPTIONAL</em>" when
used in this document are to be interpreted as described in <cite>RFC
2119</cite> <a href="#RFC2119"
rel=biblioentry>[RFC2119]<!--{{!RFC2119}}--></a>. However, for
readability, these words do not appear in all uppercase letters in this
specification.
<p>Examples in this specification are introduced with the words "for
example" or are set apart from the normative text with
<code>class="example"</code>, like this:
<div class=example>
<p>This is an example of an informative example.
</div>
<p>Informative notes begin with the word "Note" and are set apart from the
normative text with <code>class="note"</code>, like this:
<p class=note>Note, this is an informative note.
<h2 id=page-terms><span class=secno>3. </span>Page Terminology</h2>
<p>The following terminology and accompanying diagrams help to describe
the page model:
<dl>
<dt id=page-sheet>Page sheet
<dd><img
alt="The corner of a page sheet with the non-printable area at the edge and printable area inside it"
height=148 src=PageSheet.png style="float: right;" width=194>The page
sheet is one surface of the physical medium. The illustration to the
right shows a representation of the upper-left corner of a page sheet.
<dt id=printable-area>Printable and non-printable areas
<dd>The non-printable area is the area of a page sheet that a physical
device such as a printer is not capable of marking reliably, usually due
to the printer's paper handling mechanism. This value is printer
dependent and is usually a small region along each edge of the page
sheet. The printable area is the area of page sheet that a printer
<em>is</em> capable of marking reliably. The size of the printable area
is the size of the page sheet reduced by the size of the non-printable
area. A user agent may not know the dimensions of this area for a
particular printing device; but when its dimensions are known, user
agents <em class=RFC2119>MAY</em> adjust the formatting of the document
so that content falls within the printable area. How this adjustment is
accomplished is device dependent within the constraints expressed in the
sections <a href="#renderingpages">Rendering page boxes that do not fit
a page sheet</a> and <a href="#content-outside-box">Content outside the
page box</a>.
<dt id=page-orientation>Page Orientation
<dd>The page orientation is defined by comparing the length of the edges
of a <a href="#page-box">page box</a>. The page box is a rectangle with
two perpendicular edges called the long edge and the short edge. The
length of the long edge is always greater than or equal to the length of
the short edge. When the page box is square, the two edges are of the
same length and either can be used as the long edge with the other being
the short edge. This specification defines page orientations of ‘<code
class=property>portrait</code>’ and ‘<code
class=property>landscape</code>’.
<dt id=portrait>Portrait Orientation
<dd>A portrait page's height is greater than or equal to its width.
Horizontal elements are parallel to the short edge and vertical elements
to the long edge.
<dt id=landscape>Landscape Orientation
<dd>A landscape page's width is greater than or equal to its height.
Horizontal elements are parallel to the long edge and vertical elements
to the short edge. <span class=note>Note that CSS3 makes no distinction
between landscape and reverse-landscape orientations. However, future
versions of CSS may do so. UAs should consider, when formatting for
duplexed printing, the binding edge, page progression, and ease of
reading when choosing between landscape and reverse-landscape
renderings.</span>
<dt id=duplex-printing>Duplex Printing
<dd>Duplex printing prints one page box per side of a page sheet and uses
both sides of the page sheet. This module provides no ability to specify
whether a document is duplex printed, but the concept of left and right
pages is based on the assumption that the document is duplex printed,
regardless of whether or not it actually is.
<dt id=binding-edge>Binding Edge
<dd>The binding edge is the edge of the page box that is toward the
binding if the material is bound. The binding edge often has a larger
margin than the opposite edge to provide for the space used by the
binding. The binding edge can be any of the four edges. However, page
sheets are customarily bound so that the binding edge of page boxes with
portrait orientation is vertical. This module provides no method to
specify the binding edge. In duplex printing, the binding edge is on
opposite sides of the page box for the left and right pages.
<dt id=facing-pages>Facing Pages
<dd>Facing pages are two sequential pages such that when the document is
duplex printed they are on separate sheets of paper. Typically, the
earlier page will be the back side of one sheet and the later page will
be the front side of another. They are usually laid out so that the
binding edges of facing pages are vertical and adjacent when the pages
are placed in their normal reading orientation.
<dt><dfn id=left-page>Left Page</dfn>
<dd>A page that would be on the left if it is part of a pair of facing
pages as typically laid out. Page layouts for documents using a
left-to-right page progression have the earlier of the facing pages on
the left. Rules specific to the left page can be specified using the
‘<a href="#left"><code class=css>:left</code></a>’ <a
href="#page-selector"><i>page selector</i></a>.
<dt><dfn id=right-page>Right Page</dfn>
<dd>A page that would be on the right if it is part of a pair of facing
pages as typically laid out. Page layouts for documents using a
right-to-left page progression have the earlier of the facing pages on
the right. Rules specific to the right page can be specified using the
‘<a href="#right"><code class=css>:right</code></a>’ <a
href="#page-selector"><i>page selector</i></a>.
</dl>
<h2 id=page-model><span class=secno>4. </span>The Page Model</h2>
<p>In the paged media formatting model, the document is transferred into
one or more page boxes. The <dfn id=page-box>page box</dfn> is a
specialized CSS box that maps to a rectangular print media surface, such
as a page of paper. It is roughly analogous to the <a
href="http://www.w3.org/TR/CSS21/visuren.html#viewport">viewport</a>.
<img alt="" height=266 src=PageBox.png style="float: right;" width=267>
<p>As with other CSS <a
href="http://www.w3.org/TR/CSS21/box.html">boxes</a>, a page box consists
of margin, border, padding, and content areas. The content and margin
areas of a page box have special functions:
<p class=issue> In CSS 2.1, both the page box and page area are simple
rectangles. Neither is a CSS box with margins, borders, and padding. This
CSS box should be distinct from the page box and page area, which would
be its margin area and content area, respectively. Naming ideas?
<ul>
<li>The content area of a page box is called the <dfn id=page-area>page
area</dfn>. The content of the document is flowed into one or more page
boxes. The page area acts as a container for all the boxes generated by
the root element and its descendants that are laid out within a given
page box. The edges of the page area on the first page establish the
rectangle that is the initial <a
href="http://www.w3.org/TR/CSS21/visudet.html#containing-block-details">containing
block</a> of the document.
<li>The margin area of a page box is divided into 16 <dfn
id=page-margin-boxes>page-margin boxes</dfn>. Each page-margin box has
its own margin, border, padding and content areas. Page-margin boxes are
typically used to display running headers and footers.
</ul>
<p>The properties of a <a href="#page-box"><i>page box</i></a> are
determined by properties <a
href="http://www.w3.org/TR/CSS21/syndata.html#declaration">declared</a>
within the <a href="#page-context"><i>page context</i></a>, which is the
<a href="http://www.w3.org/TR/CSS21/syndata.html#x14">declaration
block</a> of the <code>@page</code> rule. Similarly the properties of a
<i>page-margin box</i> are determined by properties declared within its
<a href="#margin-context"><i>margin context</i></a>. Declarations in the
page context can affect the page box and/or inherit to the page-margin
boxes, but they do not apply to or inherit into the document's root
element or other content.
<p>The <a href="#containing-block0"><i>containing block</i></a> of the
page box is specified using the ‘<a href="#size"><code
class=property>size</code></a>’ property in the <a
href="#page-context"><i>page context</i></a>. The width and horizontal
margins of the page box are then calculated exactly as for a <a
href="http://www.w3.org/TR/CSS21/visudet.html#blockwidth">non-replaced
block element in normal flow</a>. <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> The height and vertical
margins of the page box are calculated analogously (instead of using the
block height formulas). In both cases if the values are over-constrained,
instead of ignoring any margins, the containing block is resized to
coincide with the margin edges of the page box.
<h3 id=painting><span class=secno>4.1. </span> Page Backgrounds and
Painting Order</h3>
<p>When drawing a page of content, the page layers are painted in the
following painting order (bottommost first):
<ol>
<li>page background
<li>document canvas
<li>page borders
<li>document contents
<li>page-margin boxes
</ol>
<p>In the page model, the page background behaves similar to the root
background: its <a
href="http://www.w3.org/TR/css3-background/#background-painting-area"><i>background
painting area</i></a> is the entire page box, including its margins
(regardless of ‘<code class=property>background-clip</code>’). Page
backgrounds are anchored within the page box's padding area by default
(and honor ‘<code class=property>background-origin</code>’ if the UA
supports <a href="#CSS3BG"
rel=biblioentry>[CSS3BG]<!--{{!CSS3BG}}--></a>). However if ‘<code
class=property>background-attachment</code>’ is ‘<code
class=css>fixed</code>’ then the image is positioned relative to the
page box including its margins (i.e. the <a
href="http://www.w3.org/TR/css3-background/#background-positioning-area"><i>background
positioning area</i></a>, like the <i>background painting area</i>, is
the page's margin box).
<p>The document canvas background is drawn as the page box's background:
by default its <i>background painting area</i> covers the page box's
border box, and for UAs that support <a href="#CSS3BG"
rel=biblioentry>[CSS3BG]<!--{{!CSS3BG}}--></a>, follows the ‘<code
class=property>background-clip</code>’ value specified on the root
element. It remains, however, positioned with respect to the root element
or page area as usual.
<p> With respect to the page-margin boxes, the document canvas, page
borders, and all of the document contents are treated as a single element
with a <code>z-index</code> value of ‘<code class=css>0</code>’ that
establishes a <a
href="http://www.w3.org/TR/CSS21/visuren.html#x43">stacking context</a>
<a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>: the
page-margin boxes never interleave with parts of the document content or
between the content and the canvas. They may only paint in front of the
document content or behind the document canvas. The page background is
always painted underneath everything else.
<p>The ‘<code class=property>z-index</code>’ property applies to
page-margin boxes. Since the ‘<code class=property>position</code>’
property does not apply to page-margin boxes, ‘<code
class=property>z-index</code>’ always affects page-margin boxes as if
they were positioned elements regardless of the ‘<code
class=property>position</code>’ property's value. Each page-margin
boxes always establishes a stacking context.
<p>The default painting order, or <a
href="http://www.w3.org/TR/CSS21/zindex.html">CSS2.1 Appendix E</a> "tree
order", of page-margin boxes with respect to each other is as follows:
<ol>
<li>‘<code class=css>@top-left-corner</code>’
<li>‘<code class=css>@top-left</code>’
<li>‘<code class=css>@top-center</code>’
<li>‘<code class=css>@top-right</code>’
<li>‘<code class=css>@top-right-corner</code>’
<li>‘<code class=css>@right-top</code>’
<li>‘<code class=css>@right-middle</code>’
<li>‘<code class=css>@right-bottom</code>’
<li>‘<code class=css>@bottom-right-corner</code>’
<li>‘<code class=css>@bottom-right</code>’
<li>‘<code class=css>@bottom-center</code>’
<li>‘<code class=css>@bottom-left</code>’
<li>‘<code class=css>@bottom-left-corner</code>’
<li>‘<code class=css>@left-bottom</code>’
<li>‘<code class=css>@left-middle</code>’
<li>‘<code class=css>@left-top</code>’
</ol>
<p class=note> Start with ‘<code class=css>@top-left-corner</code>’,
then go clockwise. This order is arbitrary but can be overridden with
‘<code class=property>z-index</code>’. It only has a visible effect
when page-margin boxes overlap, which should not happen in most cases.
<h3 id=content-outside-box><span class=secno>4.2. </span>Content outside
the page box</h3>
<p>When formatting content in the page model, some content may end up
outside the page box. For example, an element whose ‘<code
class=property>white-space</code>’ property has the value ‘<code
class=property>pre</code>’ can generate a box that is wider than the
page box. As another example, when boxes are positioned absolutely or
relatively, they may end up in "inconvenient" locations. For example,
images may be placed on the edge of the page box or 100,000 meters below
the page box.
<p>A specification for the exact formatting of such elements lies outside
the scope of this document. However, it is recommended that authors and
user agents observe the following general principles concerning content
outside the page box:
<ul>
<li>
<p>Content should be allowed slightly beyond the page box to allow pages
to "bleed".
<li>
<p>User agents <em class=RFC2119>SHOULD</em> avoid generating a large
number of content-empty pages to honor the positioning of elements
(e.g., printing 100 blank pages is probably neither the author's nor
the user's intent). A <dfn id=content-empty>Content-empty page</dfn> is
a page box whose page area contains no printable content other than
backgrounds and/or borders. A page box whose page area contains
generated content, or content whose visibility is ‘<code
class=property>hidden</code>’, or invisible content such as a
zero-width space is not a content-empty page. On the other hand, a page
containing only a background and/or borders and/or page-margin box
content <em>is</em> a content-empty page.
<p class=note>Note, however, that generating a small number of empty
page boxes is sometimes necessary to honor the forced-break values for
‘<code class=property>page-break-before</code>’/‘<code
class=property>break-before</code>’ and ‘<code
class=property>page-break-after</code>’/‘<code
class=property>break-after</code>’. <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> <a href="#CSS3-BREAK"
rel=biblioentry>[CSS3-BREAK]<!--{{!CSS3-BREAK}}--></a>
<li>
<p>Authors <em class=RFC2119>SHOULD NOT</em> position elements in
inconvenient locations just to avoid rendering them. Instead:
<ul>
<li>To suppress box generation entirely, set the <span
class=property>‘<code class=property>display</code>’</span>
property to <span class=css>‘<code
class=property>none</code>’</span>.
<li>To make a box invisible, set the <span class=property>‘<code
class=property>visibility</code>’</span> property.
</ul>
<li>
<p>This specification does not define how boxes positioned outside the
page box are handled. Possibilities include discarding them or creating
page boxes for them at the end of the document.
</ul>
<h3 id=progression><span class=secno>4.3. </span>Page Progression</h3>
<p>CSS distinguishes between left pages and right pages on all documents,
whether they are printed duplex or not. Each left page is followed by a
right page and vice versa. Left and right pages can be styled differently
with the <a href="#left-right-first"><code>:left</code> and
<code>:right</code> pseudo-classes</a>.
<p>Whether the first page of a document is a left page or a right page
depends on the page progression of the document. The <dfn
id=page-progression>page progression</dfn> is the direction in which the
printed pages of a document would be sequenced when laid out
side-to-side. For example, English and horizontally-set Japanese
typically progress from left to right, whereas Arabic and vertically-set
Japanese pages typically progress from right to left. In documents with a
left-to-right page progression the first page of the document is a right
page, and vice versa.
<p>The page progression direction is determined as follows:
<ul>
<li>If text is laid out in horizontal lines, the page progression is the
same as the inline progression.
<li>If text is laid out in vertical lines, the page progression is the
same as the block progression.
</ul>
<p>If the UA supports the ‘<code class=property>direction</code>’ and
‘<code class=property>writing-mode</code>’ properties from the CSS 3
Writing Modes Module <a href="#CSS3-WRITING-MODES"
rel=biblioentry>[CSS3-WRITING-MODES]<!--{{CSS3-WRITING-MODES}}--></a>, it
must <a
href="http://www.w3.org/TR/css3-writing-modes/#page-direction">determine</a>
whether the first page is a left or right page from the values of those
properties on the root element.
<p> To explicitly force a document to begin printing on a left or right
page, authors can specify a <a
href="http://www.w3.org/TR/css3-break/#break-before">‘<code
class=property>break-before</code>’</a> value that that propagates a
page break to the root. <a href="#CSS3-BREAK"
rel=biblioentry>[CSS3-BREAK]<!--{{!CSS3-BREAK}}--></a> The UA must
suppress the first (empty) page(s) in this case (and the <a
href="#first"><code>:first</code></a> pseudo-class matches the first
printed page).
<div class=example>
<pre>
html { break-before: always }
</pre>
<p> For an HTML document with a left-to-right page progression, the above
style rule will cause the first page of the document to print on a ‘<a
href="#left"><code class=css>:left</code></a>’ page
<pre>
html { break-before: left }
</pre>
<p> For an HTML document, the above style rule will cause the first page
of the document to print on a ‘<a href="#left"><code
class=css>:left</code></a>’ page, regardless of the page progression.
</div>
<h2 id=page-selector-and-context><span class=secno>5. </span> Page
Selectors and the Page Context</h2>
<h3 id=at-page-rule><span class=secno>5.1. </span><a
id=page-box-page-rule></a> The @page Rule</h3>
<p>Authors can specify various aspects of a page box, such as its
dimensions, orientation, and margins, within an ‘<code
class=css>@page</code>’ rule. ‘<code class=css>@page</code>’ rules
are allowed wherever <a
href="http://www.w3.org/TR/CSS21/syndata.html#rule-sets">rule-sets</a>
are allowed. An ‘<code class=css>@page</code>’ rule consists of the
keyword ‘<code class=css>@page</code>’, an <em
class=RFC2119>OPTIONAL</em> comma-separated list of <a
href="#page-selectors">page selectors</a> and a block of declarations
(said to be in the <dfn id=page-context>page context</dfn>). An ‘<code
class=css>@page</code>’ rule can also contain other at-rules,
interleaved between declarations. The current level of this specification
only allows <a href="#margin-at-rules">margin at-rules</a> inside
‘<code class=css>@page</code>’.
<p>‘<code class=css>@page</code>’ rules without a selector list apply
to every page. Other ‘<code class=css>@page</code>’ rules apply to
pages that <a href="#match"><i>match</i></a> at least one of their
selectors. Properties declared within the page context apply to the page
box.
<p>If an error is encountered during the processing of a declaration block
within a page or a margin context, the <a
href="http://www.w3.org/TR/CSS21/syndata.html#parsing-errors">Rules for
handling parsing errors</a> apply; that is, valid declarations within the
block are applied.
<h3 id=page-selectors><span class=secno>5.2. </span>Page selectors</h3>
<p>A <dfn id=page-selector>page selector</dfn> is made of either a <a
href="#page-type-selector"><i>page type selector</i></a> or a <a
href="#page-pseudo-class"><i>page pseudo-class</i></a>, followed by zero
or more additional <a href="#page-pseudo-class"><i>page
pseudo-classes</i></a>. No whitespace is allowed between components of a
selector. The <a href="#page_selector"><i title="page_selector">page
selector grammar</i></a> and examples can be found below.
<p>A <a href="#page-selector"><i>page selector</i></a> is said to <dfn
id=match>match</dfn> a given page if and only if all of its components
match the page.
<p>A <dfn id=page-type-selector>page type selector</dfn> is a
case-sensitive <a
href="http://www.w3.org/TR/CSS21/syndata.html#value-def-identifier">CSS
identifier</a> <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>. It <a
href="#match"><i>matches</i></a> pages of the <a
href="#using-named-pages">named page type</a> generated by the ‘<a
href="#page"><code class=property>page</code></a>’ property. <span
id=page-selector-syntax-restrict> A page type name of ‘<code
class=css>auto</code>’ (<a
href="http://www.w3.org/TR/CSS21/syndata.html#characters">ASCII
case-insensitive</a>) does not make the rule invalid, but <em
class=RFC2119>MUST</em> never match. </span>
<p>A <dfn id=page-pseudo-class>page pseudo-class</dfn> is <a
href="http://www.w3.org/TR/CSS21/syndata.html#characters">ASCII
case-insensitive</a> and has the same syntax as <a
href="http://www.w3.org/TR/selectors/#pseudo-classes">pseudo-classes</a>
in regular Selectors. <a href="#SELECT"
rel=biblioentry>[SELECT]<!--{{!SELECT}}--></a> The various <a
href="#page-pseudo-class"><i>page pseudo-classes</i></a> are defined
below.
<h4 id=spread-pseudos><span class=secno>5.2.1. </span><a
id=left-right-first></a> Spread pseudo-classes: ‘<a href="#left"><code
class=css>:left</code></a>’, ‘<a href="#right"><code
class=css>:right</code></a>’</h4>
<p>When printing double-sided documents, left and right pages are often
formatted differently. This can be expressed by using the ‘<a
href="#left"><code class=css>:left</code></a>’ and ‘<a
href="#right"><code class=css>:right</code></a>’ page pseudo-classes.
<p>All pages are automatically classified by user agents as either left
pages or right pages, based on <a href="#progression">page
progression</a>. The <dfn id=left>‘<code
class=css>:left</code>’</dfn> and <dfn id=right>‘<code
class=css>:right</code>’</dfn> pseudo-classes only <a
href="#match"><i>match</i></a> <a href="#left-page"><i
title="left page">left</i></a> or <a href="#right-page"><i
title="right page">right pages</i></a>, respectively.
<div class=example> The following example creates left and right binding
edges using these pseudo-classes:
<pre>
@page :left {
margin-left: 3cm;
margin-right: 4cm;
}
@page :right {
margin-left: 4cm;
margin-right: 3cm;
}
</pre>
</div>
<p>If different declarations have been given for left and right pages, the
user agent <em class=RFC2119>MUST</em> honor these declarations even if
the user agent does not transfer the page boxes to left and right sheets
(i.e., a printer that only prints on one side of the medium must
nevertheless produce correctly formatted output).
<div class=note>
<p> <em><strong>Note.</strong> Adding declarations to the ‘<a
href="#left"><code class=css>:left</code></a>’ or ‘<a
href="#right"><code class=css>:right</code></a>’ pseudo-class does not
necessarily influence whether the document comes out of the printer
double- or single-sided (which is outside the scope of this
specification).</em>
</div>
<h4 id=first-pseudo><span class=secno>5.2.2. </span> First-page
pseudo-class: ‘<a href="#first"><code class=css>:first</code></a>’</h4>
<p>The <dfn id=first>‘<code class=css>:first</code>’</dfn>
pseudo-class <a href="#match"><i title=match>matches</i></a> the first
printed page of a document.
<div class=example>
<pre>
@page { margin: 2cm } /* All margins set to 2cm */
@page :first {
margin-top: 10cm /* Top margin on first page 10cm */
}
</pre>
</div>
<h4 id=blank-pseudo><span class=secno>5.2.3. </span> Blank-page
pseudo-class: ‘<a href="#blank"><code class=css>:blank</code></a>’</h4>
<p>The <dfn id=blank>‘<code class=css>:blank</code>’</dfn>
pseudo-class <a href="#match"><i title=match>matches</i></a> <a
href="#content-empty"><i title="content-empty page">content-empty
pages</i></a> that appear as a result of <a
href="http://www.w3.org/TR/css3-break/#forced-breaks">forced page
breaks</a>.
<div class=note>
<p>Only the ‘<a href="#left"><code class=css>left</code></a>’, ‘<a
href="#right"><code class=css>right</code></a>’, ‘<code
class=css>recto</code>’ and ‘<code class=css>verso</code>’ values
of the ‘<code class=property>break-before</code>’ and ‘<code
class=property>break-after</code>’ properties can generate pages that
match ‘<a href="#blank"><code class=css>:blank</code></a>’.
</div>