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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html lang=en>
<head>
<title> CSS Paged Media Module Level 3</title>
<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;
}
.editorial
{
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>
<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>CSS Paged Media Module Level 3</h1>
<h2 class="no-num no-toc" id=w3c-working>Editor's Draft 21 January 2010</h2>
<dl>
<dt>This version:
<dd><a
href="http://dev.w3.org/csswg/css3-page/">http://dev.w3.org/csswg/css3-page/</a></dd>
<!-- <dd><a href="http://www.w3.org/TR/2010/ED-css3-page-20100121">http://www.w3.org/TR/2010/WD-css3-page-20100121</a></dd> -->
<dt>Latest version:
<dd><a
href="http://www.w3.org/TR/css3-page">http://www.w3.org/TR/css3-page</a>
<dt>Previous version:
<dd><a
href="http://www.w3.org/TR/2004/CR-css3-page-20040225/">http://www.w3.org/TR/2004/CR-css3-page-20040225/</a>
<dt>Editors:
<dd>Melinda Grant, Hewlett-Packard
<dd>Håkon Wium Lie, Opera Software
<dd>Elika J. Etemad, Hewlett-Packard
</dl>
<!--begin-copyright-->
<p class=copyright><a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
rel=license>Copyright</a> © 2010 <a
href="http://www.w3.org/"><acronym title="World Wide Web
Consortium">W3C</acronym></a><sup>®</sup> (<a
href="http://www.csail.mit.edu/"><acronym title="Massachusetts Institute
of Technology">MIT</acronym></a>, <a
href="http://www.ercim.eu/"><acronym title="European Research Consortium
for Informatics and Mathematics">ERCIM</acronym></a>, <a
href="http://www.keio.ac.jp/">Keio</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>This module describes the page model that partitions a flow into pages.
It builds on the <a href="/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.</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>
<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>
<p>This document was produced by the <a href="/Style/CSS/members">CSS
Working Group</a> (part of the <a href="/Style/">Style Activity</a>).
<p>This document was produced by a group operating under the <a
href="/Consortium/Patent-Policy-20040205/">5 February 2004 W3C Patent
Policy</a>. W3C maintains a <a href="/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="/Consortium/Patent-Policy-20040205/#def-essential">Essential
Claim(s)</a> must disclose the information in accordance with <a
href="/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of
the W3C Patent Policy</a>.</p>
<!--end-status-->
<p>This document contains the <abbr title="Cascading Style
Sheets">CSS3</abbr> Paged Media Module W3C Last Call <a
href="/2005/10/Process-20051014/tr.html#RecsWD">Working Draft</a> of 21
January 2010. The Last Call period ends on <span class=fudge>TBD</span>.</p>
<p>Relative to the previous Last Call Working Draft, this version
incorporates changes to the formerly named ‘<code
class=property>fit</code>’ and ‘<code
class=property>fit-position</code>’ properties; they are renamed to
‘<code class=property><a
href="#propdef-image-fit">image-fit</a></code>’ and ‘<code
class=property><a
href="#propdef-image-posn">image-position</a></code>’ and redefined
to enable additional use cases. The margin-box sizing algorithm has been
reworded to be a bit simpler, and many miscellaneous clarifications and
editorial improvements have been incorporated.</p>
<p>Features at-risk (may be removed if they lack implementor interest):</p>
<ul>
<li>image-fit
<li>image-position
<li>comma-separated page selectors
</ul>
<p>Expected next revision to this document is another LCWD, driven by the
change in definition of ‘<code class=property><a
href="#propdef-image-fit">image-fit</a></code>’ and ‘<code
class=property><a
href="#propdef-image-posn">image-position</a></code>’.</p>
<p>The <a href="lc2_issues.htm">Disposition of Comments</a> document
contains the current issues list and responses to input received during
this Last Call period.</p>
<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-box-page-rule"><span class=secno>4. </span>The Page
Model</a>
<ul class=toc>
<li><a href="#content-outside-box"><span class=secno>4.1.
</span>Content outside the page box</a>
<li><a href="#painting"><span class=secno>4.2. </span>Page Backgrounds
and Painting Order</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="#left-right-first"><span class=secno>5.2. </span>Page
pseudo-classes: :left, :right, and :first</a>
<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>Margin Boxes</a>
<ul class=toc>
<li><a href="#margin-at-rules"><span class=secno>6.1. </span>At-rules
for margin boxes</a>
<li><a href="#populating-margin-boxes"><span class=secno>6.2.
</span>Populating margin boxes</a>
<li><a href="#margin-box-dimensions"><span class=secno>6.3.
</span>Computing Margin Box Dimensions</a>
<ul class=toc>
<li><a href="#max-margin-dimension"><span class=secno>6.3.1.
</span>Margin Box Layout Terminology</a>
1DDB
<li><a href="#margin-dimension"><span class=secno>6.3.2.
</span>Margin Box Variable Dimension Computation Rules</a>
<li><a href="#margin-constraints"><span class=secno>6.3.3.
</span>Margin Box Fixed Dimension Computation Rules</a>
</ul>
<li><a href="#margin-box-ex"><span class=secno>6.4. </span>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>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="#pg-br-before-after"><span class=secno>9.1. </span>Break
before/after elements: <span class=property>‘<code
class=property>page-break-before</code>’</span>, <span
class=property>‘<code
class=property>page-break-after</code>’</span>, <span
class=property>‘<code
class=property>page-break-inside</code>’</span></a>
<li><a href="#using-named-pages"><span class=secno>9.2. </span>Using
named pages: ‘<code class=property>page</code>’</a>
<li><a href="#breaks-inside"><span class=secno>9.3. </span>Breaks
inside elements: ‘<code class=property>orphans</code>’,
‘<code class=property>widows</code>’</a>
<li><a href="#allowed-pg-brk"><span class=secno>9.4. </span>Allowed
page breaks</a>
<li><a href="#forced-pg-brk"><span class=secno>9.5. </span>Forced page
breaks</a>
<li><a href="#best-pg-brk"><span class=secno>9.6. </span>"Best" page
breaks</a>
</ul>
<li><a href="#image-properties"><span class=secno>10. </span>Image
Properties</a>
<ul class=toc>
<li><a href="#image-orientation"><span class=secno>10.1.
</span>Orienting an Image on the Page: the image-orientation
property</a>
<li><a href="#img-fit"><span class=secno>10.2. </span>The ‘<code
class=property>image-fit</code>’ Property</a>
<li><a href="#img-fit"><span class=secno>10.3. </span>The ‘<code
class=property>image-position</code>’ Property</a>
</ul>
<li class=no-num><a href="#properties-list">Appendix A: Applicable CSS2.1
Properties</a>
<ul class=toc>
<li class=no-num><a
href="#properties-that-apply-within-the-page-co">Properties that apply
within the page context</a>
<li class=no-num><a
href="#properties-that-apply-within-the-margin-">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="#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="/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:</p>
<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>
<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>
<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.</p>
</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.</p>
<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:</p>
<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 id=left-page>Left Page
<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
<span class=css>‘<code class=css>:left</code>’</span> page
selector.
<dt id=right-page>Right Page
<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
<span class=css>‘<code class=css>:right</code>’</span> page
selector.
</dl>
<h2 id=page-box-page-rule><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="/TR/CSS21/visuren.html#viewport">viewport</a>. <img alt=""
height=266 src=PageBox.png style="float: right;" width=267> As with other
CSS <a href="/TR/CSS21/box.html">boxes</a>, a page box consists of
margin, border, padding, and content areas. The containing block of the
page box is the rectangle that coincides with its margin edges.
<p>The content and margin areas of a page box have special functions:</p>
<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="/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=margin-boxes0>margin boxes</dfn>. Each margin box has its own margin,
border, padding and content areas. Margin boxes are typically used to
display running headers and footers.
</ul>
<p>The properties of a <dfn id=page-box0>page box</dfn> are determined by
properties <a href="/TR/CSS21/syndata.html#declaration">declared</a>
within the <dfn id=page-context0><a href="#page-context">page
context</a></dfn>, which is the <a
href="/TR/CSS21/syndata.html#x14">declaration block</a> of the <code><a
href="#page">@page</a></code> rule. Page boxes differ from other boxes in
that the <span class=property>‘<code
class=property>width</code>’</span> and <span
class=property>‘<code class=property>height</code>’</span>
properties do not apply to a page box. The size of the page box is
specified using the <span class=property>‘<code class=property><a
href="#size">size</a></code>’</span> property in the page context.</p>
<p>Declarations in the page context affect the page box and/or can inherit
to the margin boxes, but they do not apply to or inherit into the
document's root element or other content.</p>
<h3 id=content-outside-box><span class=secno>4.1. </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>
<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:</p>
<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 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 <span
class=css>‘<code class=property>left</code>’</span> and
<span class=css>‘<code class=property>right</code>’</span>
values for <span class=property>‘<code class=property><a
href="#page-break-before">page-break-before</a></code>’</span>
and <span class=property>‘<code class=property><a
href="#page-break-after">page-break-after</a></code>’</span>.
<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=painting><span class=secno>4.2. </span>Page Backgrounds and
Painting Order</h3>
<p>When drawing a page of content, the page background and borders are
painted first (underneath). Margin-boxes are painted over (on top of) the
page box. The root element then paints the canvas and the document
contents within the page padding box.</p>
<p>The exact painting order of margin boxes is not specified, however it
is <em class=RFC2119>recommended</em> that when margin boxes overlap,
paint order should place center/middle margin boxes on top of corner
margin boxes, which are in turn painted on top of other boxes. More
precisely, in terms of the algorithm in <a
href="http://www.w3.org/TR/CSS21/zindex.html">CSS2.1 Appendix E</a> the
exact "tree order" of margin boxes is not defined, but it is recommended
that center/middle boxes be after corner boxes, which should themselves
be after other boxes.</p>
<p>The UA may support the <code>z-index</code> property for margin boxes.
In this case the root element, together with the canvas background 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>’: the
margin boxes never interleave with parts of the document content, they
may only paint in front of or behind the document content and its canvas.
The page box itself generates a new stacking context and is treated as
the parent of all the margin boxes as well as the document content. In
other words, nothing ever paints behind the page box backgrounds or
borders. Since the <code>position</code> property does not apply to
margin boxes, <code>z-index</code> always affects margin boxes as if they
were positioned elements regardless of the <code>position</code>
property's value. <span class=issue>Mark this at-risk.</span></p>
<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
with a left-to-right page progression the first page of the document is a
right page, and vice versa.</p>
<p>The page progression direction is determined as follows:</p>
<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>block-progression</code>’ properties from the CSS 3
Text Layout Module <a href="#CSS3TEXTLAYOUT"
rel=biblioentry>[CSS3TEXTLAYOUT]<!--{{CSS3TEXTLAYOUT}}--></a>, it must
determine whether the first page is a left or right page from the values
of those properties on the root element.</p>
<p>To explicitly force a document to begin printing on a left or right
page, authors can <a href="#page-break-before">insert a page break
before</a> the first generated box. The UA must suppress the first
(empty) page(s) in this case (and the <code>:first</code> selector
applies to the first printed page).</p>
<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>The @page Rule</h3>
<p>Authors can specify various aspects of a page box, such as its
dimensions, orientation, and margins, within an <a class=css
href="#page">@page</a> rule. An <a class=css href="#page">@page</a> rule
consists of the keyword <span class=css>‘<code class=css><a
href="#page">@page</a></code>’</span>, an <em
class=RFC2119>OPTIONAL</em> page name followed with no intervening space
by an <em class=RFC2119>OPTIONAL</em> page pseudo-class, and a block of
declarations (said to be in the <dfn id=page-context>page context</dfn>).
<a href="#margin-at-rules">Margin at-rules</a> may be interleaved with
the declarations in the page context.
<p>The <em class=RFC2119>OPTIONAL</em> page name and <em
class=RFC2119>OPTIONAL</em> page pseudo-class constitute the <dfn
id=page-selector>page selector</dfn>. The page selector specifies for
which pages the declarations apply. In CSS3, page selectors can designate
the first page of a document, all left pages, all right pages, or <a
href="#using-named-pages">pages with specific names</a>. Multiple
selectors may be combined with a comma (which may be preceded and/or
followed by white space); in this case the ‘<code class=css><a
href="#page">@page</a></code>’ rule applies to pages that match any
of the page selectors. (Note: this feature is at-risk.) If no page
selector is given, then the ‘<code class=css><a
href="#page">@page</a></code>’ rule applies to all pages.</p>
<p>Properties declared within the page context apply to the page box.</p>
<p>If an error is encountered during the processing of a declaration block
within a page or a margin context, the <a
href="/TR/CSS21/syndata.html#parsing-errors">Rules for handling parsing
errors</a> apply; that is, valid declarations within the block are
applied.</p>
<h3 id=left-right-first><span class=secno>5.2. </span>Page pseudo-classes:
:left, :right, and :first</h3>
<p>When printing double-sided documents, left and right pages are often
formatted differently. This can be expressed through CSS pseudo-classes
defined in the <a href="#page-context">page context</a>.</p>
<p>All pages are automatically classified by user agents as either left
pages or right pages. The <span class=css>‘<code
class=css>:left</code>’</span> and <span class=css>‘<code
class=css>:right</code>’</span> page pseudo-classes can be used to
selectively apply rules to only the left or right pages, respectively.</p>
<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).</p>
<p>Authors can also specify style for the first page of a document with
the <span class=css>‘<code class=css>:first</code>’</span>
pseudo-class. Such style rules are applied only to the first printed page
of a document.</p>
<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>
<div class=example>
<pre>
html {page-break-before: always;}
</pre>
<p>For an XHTML document with a left-to-right page progression, the above
style rule will cause the first page of the document to print on a
‘<code class=css>:right</code>’ page</p>
</div>
<div class=note>
<p><em><strong>Note.</strong> Adding declarations to the <span
class=css>‘<code class=css>:left</code>’</span> or <span
class=css>‘<code class=css>:right</code>’</span>
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></p>
</div>
<div class=note>
<p><em><strong>Note.</strong> Future versions of CSS may include other
page pseudo-classes.</em></p>
</div>
<h3 id=syntax-page-selector><span class=secno>5.3. </span>@page rule
grammar</h3>
<p>The syntax for the @page rule is a specialization of the generic
at-rule defined by CSS 2.1. This grammar extends the at-rule syntax to
allow @page rules nested inside @media rules. User agents <em
class=RFC2119>MUST</em> adhere to the following grammar:</p>
<p>See <a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>,
Section 4.1.1 and Appendix G for the expansion of missing productions:</p>
<p id=specializatons-of-ATKEYWORD> All new lexical tokens are
specializations of the ATKEYWORD lexical token:</p>
<pre class=lexical>
PAGE_SYM ::= "@page"
TOPLEFTCORNER_SYM ::= "@top-left-corner"
TOPLEFT_SYM ::= "@top-left"
TOPCENTER_SYM ::= "@top-center"
TOPRIGHT_SYM ::= "@top-right"
TOPRIGHTCORNER_SYM ::= "@top-right-corner"
BOTTOMLEFTCORNER_SYM ::= "@bottom-left-corner"
BOTTOMLEFT_SYM ::= "@bottom-left"
BOTTOMCENTER_SYM ::= "@bottom-center"
BOTTOMRIGHT_SYM ::= "@bottom-right"
BOTTOMRIGHTCORNER_SYM ::= "@bottom-right-corner"
LEFTTOP_SYM ::= "@left-top"
LEFTMIDDLE_SYM ::= "@left-middle"
LEFTBOTTOM_SYM ::= "@left-bottom"
RIGHTTOP_SYM ::= "@right-top"
RIGHTMIDDLE_SYM ::= "@right-middle"
RIGHTBOTTOM_SYM ::= "@right-bottom"
<span id=syntax-prod-media>media</span> :
MEDIA_SYM S* medium [ COMMA S* medium ]* LBRACE S* [ page | ruleset ]* '}' S*
;
<a href="#page" id=syntax-prod-page>page</a> :
PAGE_SYM S* IDENT? S* pseudo_page? S*
'{' S* [ margin_box | ruleset ]? [ ';' S* [ margin_box | ruleset ]? ]* '}' S*
;
<span class=issue>Space should not be allowed between name and pseudo.</span>
<span id=syntax-prod-pseudo-page>pseudo_page</span> :
':' [ "left" | "right" | "first" ]
;
<span id=syntax-prod-margin>margin_box</span> :
margin_sym S* '{' ruleset* '}' S*
;
<span id=syntax-prod-margin-sym>margin_sym</span> :
TOPLEFTCORNER_SYM |
TOPLEFT_SYM |
TOPCENTER_SYM |
TOPRIGHT_SYM |
TOPRIGHTCORNER_SYM |
BOTTOMLEFTCORNER_SYM |
BOTTOMLEFT_SYM |
BOTTOMCENTER_SYM |
BOTTOMRIGHT_SYM |
BOTTOMRIGHTCORNER_SYM |
LEFTTOP_SYM |
LEFTMIDDLE_SYM |
LEFTBOTTOM_SYM |
RIGHTTOP_SYM |
RIGHTMIDDLE_SYM |
RIGHTBOTTOM_SYM
;
</pre>
<p id=page-selector-syntax-restrict> The value ‘<code
class=property>auto</code>’ is not a valid page name and must be
treated as matching nothing.
<div class=example>
<p>The following are examples of page selectors (declaration block
intentionally left blank)</p>
<pre>
@page { ... }
@page :left { ... }
@page :right { ... }
@page LandscapeTable { ... }
@page CompanyLetterHead:first { ... } /* identifier and pseudo page. */
@page:first { ... };
</pre>
<p>The following are examples of margin boxes where the declaration
blocks are intentionally left blank.</p>
<pre>
@page {
@top-left { ... /* document name */ }
@bottom-center { ... /* page number */}
}
@page :left { @left-middle { ... /* page number in left margin */ }}
@page :right{ @right-middle { ... /* page number in right margins of right pages */}}
@page :left { @bottom-left-corner { ... /* left page numbers */ }}
@page :right { @bottom-right-corner { ... /* right page numbers */ }}
@page :first { @bottom-left-corner { ... /* empty footer on 1st page */ }
@bottom-right-corner { ... /* empty footer */ } }
</pre>
</div>
<h3 id=cascading-and-page-context><span class=secno>5.4. </span>Cascading
in the page context</h3>
<p>Declarations in page and margin contexts <a
href="/TR/CSS21/cascade.html">cascade</a> just like declarations in <a
href="/TR/CSS21/syndata.html#rule-sets">rule sets</a>.</p>
<p>The specificity of page selectors is computed in a manner analogous to
the computations defined in the <a
href="/TR/CSS21/selector.html">Selectors</a> module:</p>
<ul>
<li>if the page selector has a named page, f=1; else f=0
<li>if the page selector has a ‘<code
class=css>:first</code>’ pseudo-class, g=1; else g=0
<li>if the page selector has a ‘<code class=css>:left</code>’
or ‘<code class=css>:right</code>’ pseudo-class, h=1; else
h=0
</ul>
<p>Concatenating the three numbers f-g-h gives the specificity.</p>
<p>Properties that are not explicitly set within the page or margin
context take their initial values and do not inherit from any element.</p>
<div class=example>
<p>Some page specificity calculation examples follow:</p>
<pre>
@page { } /* f=0 g=0 h=0 -> specificity = 000 */
@page :left { } /* f=0 g=0 h=1 -> specificity = 001 */
@page :first { } /* f=0 g=1 h=0 -> specificity = 010 */
@page artsy { } /* f=1 g=0 h=0 -> specificity = 100 */
@page artsy:left { } /* f=1 g=0 h=1 -> specificity = 101 */
@page artsy:first { } /* f=1 g=1 h=0 -> specificity = 110 */
</pre>
</div>
<div class=example>
<p>Consider the following usage example:</p>
<pre>
@page {
margin-left: 3cm;
}
@page :left {
margin-left: 4cm;