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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html lang=en>
<head profile="http://dublincore.org/documents/2008/08/04/dc-html/ ">
<title>CSS Backgrounds and Borders Module Level 4</title>
<link href="http://purl.org/dc/terms/" rel=schema.dcterms>
<link href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
rel=dcterms.rights>
<meta content="CSS Backgrounds and Borders Module Level 4"
name=dcterms.title>
<meta content=text name=dcterms.type>
<meta content=2012-11-14 name=dcterms.issued>
<meta content="Bert Bos" name=dcterms.creator>
<meta content="Elika J. Etemad" nam
133E
e=dcterms.creator>
<meta content="Brad Kemper" name=dcterms.creator>
<meta content="Lea Verou" name=dcterms.creator>
<meta content=W3C name=dcterms.publisher>
<meta content="http://www.w3.org/TR/2012/ED-css4-background-20121114/"
name=dcterms.identifier>
<link href="../default.css" rel=stylesheet type="text/css">
<style type="text/css">
.prod { font-family: inherit; font-size: inherit }
pre.prod { white-space: pre-wrap; margin: 1em 0 1em 2em }
code { font-size: inherit; }
#box-shadow-samples td { background: white; color: black; }
</style>
<link href="http://www.w3.org/StyleSheets/TR/W3C-ED.css" rel=stylesheet
type="text/css">
<body>
<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 Backgrounds and Borders Module Level 4</h1>
<h2 class="no-num no-toc" id='longstatus-date'>Editor's Draft 14 November
2012</h2>
<dl>
<dt>This version:
<dd><!-- <a href="http://www.w3.org/TR/2012/CR-css4-background-20121114">http://www.w3.org/TR/2012/ED-css4-background-20121114/</a> -->
<a
href="http://dev.w3.org/csswg/css4-background">http://dev.w3.org/csswg/css4-background</a>
<dt>Latest version:
<dd><a
href="http://www.w3.org/TR/css4-background">http://www.w3.org/TR/css4-background/</a>
<dt>Feedback:</dt>
<dd><a href="mailto:www-style@w3.org?subject=%5Bcss-backgrounds%5D%20feedback"
>www-style@w3.org</a>
with subject line “<kbd>[css-backgrounds]
<var>… message topic …</var></kbd>”
(<a rel="discussion" href="http://lists.w3.org/Archives/Public/www-style/"
>archives</a>)
<dt id=editors-list>Editors:
<dd><a href="mailto:bert@w3.org">Bert Bos</a> (<a
href="http://www.w3.org/">W3C</a>)
<dd><a href="http://fantasai.inkedblade.net/contact">Elika J. Etemad</a>
(Invited Expert)
<dd><a href="mailto:brad.kemper@gmail.com">Brad Kemper</a> (Invited
Expert)
<dd><a href="mailto:lea@w3.org">Lea Verou</a> (<a
href="http://www.w3.org/">W3C</a>)
</dl>
<!--copyright-->
<hr title="Separator for header">
</div>
<details class=obsolete open=open> <summary>Not Ready For
Implementation</summary>
<p> This spec is not yet ready for implementation. It exists in this
repository to record the ideas and promote discussion.
<p> Before attempting to implement this spec, please contact the CSSWG at
www-style@w3.org.
</details>
<h2 class="no-num no-toc" id=abstract> Abstract</h2>
<p>CSS is a language for describing the rendering of structured documents
(such as HTML and XML) on screen, on paper, in speech, etc. This draft
contains the features of CSS relating to the borders and backgrounds of
boxes on the page. It includes and extends the functionality of CSS
Backgrounds and Borders Level 3. [[CSS3BACKGROUND]] The main extensions
compared to level 3 are shaping (‘<code
class=property>corner-shape</code>’) and clipping borders (‘<a
href="#border-clip"><code class=property>border-clip</code></a>’),
logical background positions (‘<a href="#background-position"><code
class=property>background-position</code></a>’), and the ‘<code
class=css>extend</code>’ ability of ‘<a
href="#background-repeat"><code
class=property>background-repeat</code></a>’.
<h2 class="no-num no-toc" id=status> Status of this document</h2>
<p style="color: red; background: yellow; border: solid thick;">
<strong>This draft is not actively-maintained at the moment. Comments are
welcome, but please refer to <a
href="http://www.w3.org/TR/css3-background/">CSS3 Backgrounds and
Borders</a> if you are implementing something.</strong>
<!--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=%5Bcss4-background%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
“css4-background” in the subject, preferably like this:
“[<!---->css4-background<!---->] <em>…summary of comment…</em>”
<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-->
<h2 class="no-num no-toc" id=contents>Table of contents</h2>
<!--begin-toc-->
<ul class=toc>
<li><a href="#introduction"><span class=secno>1. </span> Introduction</a>
<li><a href="#values"><span class=secno>2. </span> Values</a>
<li><a href="#backgrounds"><span class=secno>3. </span> Background
properties</a>
<ul class=toc>
<li><a href="#layering"><span class=secno>3.1. </span> Layering multiple
background images</a>
<li><a href="#the-background-color"><span class=secno>3.2. </span> The
‘<code class=property>background-color</code>’ property</a>
<li><a href="#the-background-image"><span class=secno>3.3. </span> The
‘<code class=property>background-image</code>’ property</a>
<li><a href="#the-background-repeat"><span class=secno>3.4. </span> The
‘<code class=property>background-repeat</code>’ property</a>
<li><a href="#the-background-attachment"><span class=secno>3.5. </span>
The ‘<code class=property>background-attachment</code>’
property</a>
<li><a href="#the-background-position"><span class=secno>3.6. </span>
The ‘<code class=property>background-position</code>’ property</a>
<li><a href="#the-background-clip"><span class=secno>3.7. </span> The
‘<code class=property>background-clip</code>’ property</a>
<li><a href="#the-background-origin"><span class=secno>3.8. </span> The
‘<code class=property>background-origin</code>’ property</a>
<li><a href="#the-background-size"><span class=secno>3.9. </span> The
‘<code class=property>background-size</code>’ property</a>
<li><a href="#the-background"><span class=secno>3.10. </span> The
‘<code class=property>background</code>’ shorthand property</a>
<li><a href="#special-backgrounds"><span class=secno>3.11. </span> The
backgrounds of special elements</a>
</ul>
<li><a href="#borders"><span class=secno>4. </span> Border properties</a>
<ul class=toc>
<li><a href="#the-border-color"><span class=secno>4.1. </span> The
‘<code class=property>border-color</code>’ properties</a>
<li><a href="#the-border-style"><span class=secno>4.2. </span> The
‘<code class=property>border-style</code>’ properties</a>
<li><a href="#the-border-width"><span class=secno>4.3. </span> The
‘<code class=property>border-width</code>’ properties</a>
<li><a href="#the-border-shorthands"><span class=secno>4.4. </span>The
border shorthand properties</a>
</ul>
<li><a href="#corners"><span class=secno>5. </span> Shaped Corners</a>
<ul class=toc>
<li><a href="#the-border-radius"><span class=secno>5.1. </span> The
‘<code class=property>border-radius</code>’ properties </a>
<li><a href="#corner-shaping"><span class=secno>5.2. </span> Corner
Shaping</a>
<li><a href="#corner-clipping"><span class=secno>5.3. </span> Corner
Clipping</a>
<li><a href="#corner-transitions"><span class=secno>5.4. </span> Color
and Style Transitions</a>
<li><a href="#corner-overlap"><span class=secno>5.5. </span> Overlapping
Curves</a>
<li><a href="#border-radius-tables"><span class=secno>5.6. </span>
Effect on Tables</a>
<li><a href="#border-corner-shape"><span class=secno>5.7. </span> The
‘<code class=property>border-corner-shape</code>’ property</a>
</ul>
<li><a href="#border-images"><span class=secno>6. </span> Border
Images</a>
<ul class=toc>
<li><a href="#the-border-image-source"><span class=secno>6.1. </span>
The ‘<code class=property>border-image-source</code>’ property</a>
<li><a href="#the-border-image-slice"><span class=secno>6.2. </span> The
‘<code class=property>border-image-slice</code>’ property</a>
<li><a href="#the-border-image-width"><span class=secno>6.3. </span> The
‘<code class=property>border-image-width</code>’ property</a>
<li><a href="#the-border-image-outset"><span class=secno>6.4. </span>
The ‘<code class=property>border-image-outset</code>’ property</a>
<li><a href="#the-border-image-repeat"><span class=secno>6.5. </span>
The ‘<code class=property>border-image-repeat</code>’ property</a>
<li><a href="#border-image-process"><span class=secno>6.6. </span>
Border-image drawing process</a>
<li><a href="#the-border-image"><span class=secno>6.7. </span>The
‘<code class=property>border-image</code>’ shorthand</a>
</ul>
<li><a href="#misc"><span class=secno>7. </span>Miscellaneous Effects</a>
<ul class=toc>
<li><a href="#the-box-decoration-break"><span class=secno>7.1.
</span>The ‘<code class=property>box-decoration-break</code>’
property</a>
<li><a href="#the-box-shadow"><span class=secno>7.2. </span>The ‘<code
class=property>box-shadow</code>’ property</a>
</ul>
<li><a href="#clipping-borders"><span class=secno>8. </span>Clipping
borders</a>
<ul class=toc>
<li><a href="#the-border-clip-properties"><span class=secno>8.1.
</span>The ‘<code class=property>border-clip</code>’ properties</a>
</ul>
<li><a href="#acknowledgments"><span class=secno>9.
</span>Acknowledgments</a>
<li><a href="#references"><span class=secno>10. </span>References</a>
<ul class=toc>
<li class=no-num><a href="#normative-references">Normative
references</a>
<li class=no-num><a href="#other-references">Other references</a>
</ul>
<li class=no-num><a href="#property-index">Property index</a>
<li class=no-num><a href="#index">Index</a>
</ul>
<!--end-toc-->
<h2 id=introduction><span class=secno>1. </span> Introduction</h2>
<p><em>This section is not normative.</em>
<p>When elements are rendered according to the <a
href="http://www.w3.org/TR/CSS21/box.html">CSS box model</a> <a
href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>, each element
is either not displayed at all, or formatted as one or more rectangular
boxes. Each box has a rectangular content area, a band of padding around
the content, a border around the padding, and a margin outside the border.
(The margin may actually be negative, but margins have no influence on the
background and border.)
<div class=figure>
<p><img
alt="Diagram of a typical box, showing the content, padding, border and margin areas"
src=box>
<p class=caption>The various areas and edges of a typical box. (This
diagram is explained in the CSS2.1 Box Model chapter <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>.)
</div>
<p>The properties of this module deal with the decoration of the border
area and with the background of the content, padding and border areas.
Additionally the box may be given a "drop-shadow" effect with the ‘<a
href="#box-shadow"><code class=property>box-shadow</code></a>’ property.
<p>If an element is broken into multiple boxes, ‘<a
href="#box-decoration-break"><code
class=property>box-decoration-break</code></a>’ defines how the borders
and background are divided over the various boxes. (An element can result
in more than one box if it is broken at the end of a line, at the end of a
column or at the end of a page; and continued in the next line, column or
page.)
<p>The relative stacking order of backgrounds, borders, and shadows is
given in this module. For how these layers interact with other rendered
content, see Appendix E “Elaborate description of Stacking Contexts”
in <a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>.
<h2 id=values><span class=secno>2. </span> Values</h2>
<p>This specification follows the <a
href="http://www.w3.org/TR/CSS21/about.html#property-defs">CSS property
definition conventions</a> from <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> and the value type
definitions from CSS Values and Units Level 3 [[!CSS3VALUES]].
<h2 id=backgrounds><span class=secno>3. </span> Background properties</h2>
<p>Each box has a background layer that may be fully transparent (the
default), or filled with a color and/or one or more images. The background
properties specify what color (‘<a href="#background-color"><code
class=property>background-color</code></a>’) and images (‘<a
href="#background-image"><code
class=property>background-image</code></a>’) to use, and how they are
sized, positioned, tiled, etc.
<p>The background properties are not inherited, but the parent box's
background will shine through by default because of the initial ‘<code
class=property>transparent</code>’ value on ‘<a
href="#background-color"><code
class=property>background-color</code></a>’.
<h3 id=layering><span class=secno>3.1. </span> Layering multiple background
images</h3>
<p>The background of a box can have multiple <span class=index
id=layers>layers</span>. The number of layers is determined by the number
of comma-separated values in the ‘<a href="#background-image"><code
class=property>background-image</code></a>’ property. Note that a value
of ‘<code class=property>none</code>’ still creates layer.
<p>Each of the images is sized, positioned, and tiled according to the
corresponding value in the other background properties. The lists are
matched up from the first value: excess values at the end are not used. If
a property doesn't have enough comma-separated values to match the number
of layers, the <span>UA</span> must calculate its used value by repeating
the list of values until there are enough.
<div class=example>
<p>For example, this set of declarations:
<pre>
<!-- -->background-image: url(flower.png), url(ball.png), url(grass.png);
<!-- -->background-position: center center, 20% 80%, top left, bottom right;
<!-- -->background-origin: border-box, content-box;
<!-- -->background-repeat: no-repeat;
</pre>
<p>has exactly the same effect as this set with the extra position dropped
and the missing values for ‘<a href="#background-origin"><code
class=property>background-origin</code></a>’ and ‘<a
href="#background-repeat"><code
class=property>background-repeat</code></a>’ filled in (emphasized for
clarity):
<pre>
<!-- -->background-image: url(flower.png), url(ball.png), url(grass1.png);
<!-- -->background-position: center center, 20% 80%, top left;
<!-- -->background-origin: border-box, content-box<strong>, border-box</strong>;
<!-- -->background-repeat: no-repeat<strong>, no-repeat, no-repeat</strong>;
</pre>
</div>
<p>The first image in the list is the layer closest to the user, the next
one is painted behind the first, and so on. The background color, if
present, is painted below all of the other layers.
<p class=note>Note that the <a href="#border-images">border-image
properties</a> can also define a background image, which, if present, is
painted on top of the background created by the background properties.
<h3 id=the-background-color><span class=secno>3.2. </span> The ‘<a
href="#background-color"><code
class=property>background-color</code></a>’ property</h3>
<table class=propdef>
<tbody>
<tr>
<th>Name:
<td><dfn id=background-color>background-color</dfn>
<tr>
<th>Value:
<td><var><color></var>
<tr>
<th>Initial:
<td>transparent
<tr>
<th>Applies to:
<td>all elements
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed value:
<td>the computed color(s)
</table>
<p>This property sets the <span class=index id=background-color0
title="color!!background">background color</span> of an element. The color
is drawn behind any background images.
<div class=example>
<p>Example:
<pre>h1 { background-color: #F00 } /* Sets background to red. */</pre>
</div>
<p>The background color is clipped according to the ‘<a
href="#background-clip"><code class=property>background-clip</code></a>’
value associated with the bottom-most background image.
<h3 id=the-background-image><span class=secno>3.3. </span> The ‘<a
href="#background-image"><code
class=property>background-image</code></a>’ property</h3>
<table class=propdef>
<tbody>
<tr>
<th>Name:
<td><dfn id=background-image>background-image</dfn>
<tr>
<th>Value:
<td><a href="#ltbg-imagegt"><var><bg-image></var></a> [ , <a
href="#ltbg-imagegt"><var><bg-image></var></a> ]*
<tr>
<th>Initial:
<td>none
<tr>
<th>Applies to:
<td>all elements
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed value:
<td>as specified, but with URIs made absolute
</table>
<p>This property sets the background image(s) of an element. Images are
drawn with the first specified one on top (closest to the user) and each
subsequent image behind the previous one. Where
<pre class=prod><dfn
id=ltbg-im
1DDA
agegt><var><bg-image></var></dfn> = <var><image></var> | none</pre>
<p>A value of <dfn id=none
title="''none''!!'background-image' value">‘<code
class=css>none</code>’</dfn> counts as an image layer but draws nothing.
An image that is empty (zero width or zero height), that fails to
download, or that cannot be displayed (e.g., because it is not in a
supported image format) likewise counts as a layer but draws nothing.
<p>See the section <a href="#layering">“Layering multiple background
images”</a> for how ‘<a href="#background-image"><code
class=property>background-image</code></a>’ interacts with other
comma-separated background properties to form each background image layer.
<p>When setting a background image, authors should also specify a ‘<a
href="#background-color"><code class=css>background-color</code></a>’
that will preserve contrast with the text for when the image is
unavailable.
<p>For accessibility reasons, authors should not use background images as
the sole method of conveying important information. See <a
href="http://www.w3.org/TR/2008/NOTE-WCAG20-TECHS-20081211/F3">Web Content
Accessibility Guideline F3</a> <a href="#WCAG20"
rel=biblioentry>[WCAG20]<!--{{WCAG20}}--></a>. Images are not accessible
in non-graphical presentations, and background images specifically might
be turned off in high-contrast display modes.
<p class=note>Note that stylistic foreground images can be provided in CSS
with the <a
href="http://www.w3.org/TR/CSS21/generate.html#content">content</a>
property. (Semantically-important foreground images should be provided in
the document markup, e.g. with the <img> tag in HTML.)
<p class=note><a
href="http://www.w3.org/TR/media-frags/#naming-space">Media fragments</a>
can be used to display a portion of an image. The <a
href="http://www.w3.org/TR/css3-images/">CSS Images</a> module will
provide fallback syntax for image formats and include additional controls
for image display.
<div class=example>
<p>Some examples specifying background images:
<pre>
<!-- -->body { background-image: url("marble.svg") }
<!-- -->p { background-image: none }
<!-- -->div { background-image: url(tl.png), url(tr.png) }</pre>
</div>
<p class=note>Implementations may optimize by not downloading and drawing
images that are not visible (e.g., because they are behind other, fully
opaque images).
<h3 id=the-background-repeat><span class=secno>3.4. </span> The ‘<a
href="#background-repeat"><code
class=property>background-repeat</code></a>’ property</h3>
<table class=propdef>
<tbody>
<tr>
<th>Name:
<td><dfn id=background-repeat>background-repeat</dfn>
<tr>
<th>Value:
<td><a href="#ltrepeat-stylegt"><var><repeat-style></var></a> [ ,
<a href="#ltrepeat-stylegt"><var><repeat-style></var></a> ]*
<tr>
<th>Initial:
<td>repeat
<tr>
<th>Applies to:
<td>all elements
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed value:
<td>A list, each item consisting of: two keywords, one per dimension
</table>
<p>Specifies how background images are tiled after they have been <a
href="#the-background-size">sized</a> and <a
href="#the-background-position">positioned</a>. Where
<pre class=prod><dfn
id=ltrepeat-stylegt><var><repeat-style></var></dfn> = repeat-x | repeat-y | [repeat | space | round | no-repeat]{1,2}</pre>
<p>Single values for <a
href="#ltrepeat-stylegt"><var><repeat-style></var></a> have the
following meanings:
<dl>
<dt><dfn id=repeat-x>‘<code class=css>repeat-x</code>’</dfn>
<dd>Equivalent to ‘<code class=css>repeat no-repeat</code>’.
<dt><dfn id=repeat-y>‘<code class=css>repeat-y</code>’</dfn>
<dd>Equivalent to ‘<code class=css>no-repeat repeat</code>’.
<dt>‘<code class=css>repeat</code>’
<dd>Equivalent to ‘<code class=css>repeat repeat</code>’.
<dt>‘<code class=css>space</code>’
<dd>Equivalent to ‘<code class=css>space space</code>’
<dt>‘<code class=css>round</code>’
<dd>Equivalent to ‘<code class=css>round round</code>’
<dt>‘<code class=css>no-repeat</code>’
<dd>Equivalent to ‘<code class=css>no-repeat no-repeat</code>’
</dl>
<p>If a <a href="#ltrepeat-stylegt"><var><repeat-style></var></a>
value has two keywords, the first one is for the horizontal direction, the
second for the vertical one, as follows:
<dl>
<dt><dfn id=repeat title="''repeat''!!'background-repeat' value">‘<code
class=css>repeat</code>’</dfn>
<dd>The image is repeated in this direction as often as needed to cover
the <a class=index href="#background-painting-area"
id=background-painting-area0>background painting area</a>.
<dt><dfn id=space title="''space''!!'background-repeat' value">‘<code
class=css>space</code>’</dfn>
<dd>The image is repeated as often as will fit within the <a class=index
href="#background-positioning-area"
id=background-positioning-area0>background positioning area</a> without
being clipped and then the images are spaced out to fill the area. The
first and last images touch the edges of the area. If the <a class=index
href="#background-painting-area" id=background-painting-area1>background
painting area</a> is larger than the background positioning area, then
the pattern repeats to fill the background painting area. The value of
‘<a href="#background-position"><code
class=property>background-position</code></a>’ for this direction is
ignored, unless there is not enough space for two copies of the image in
this direction, in which case only one image is placed and ‘<a
href="#background-position"><code
class=property>background-position</code></a>’ determines its position
in this direction.
<dt><dfn id=round title="''round''!!'background-repeat' value">‘<code
class=css>round</code>’</dfn>
<dd>The image is repeated as often as will fit within the <a class=index
href="#background-positioning-area"
id=background-positioning-area.>background positioning area.</a> If it
doesn't fit a whole number of times, it is rescaled so that it does. See
the formula under ‘<a href="#background-size"><code
class=property>background-size</code></a>’. If the <a class=index
href="#background-painting-area" id=background-painting-area2>background
painting area</a> is larger than the background positioning area, then
the pattern repeats to fill the background painting area.
<dt><dfn id=no-repeat
title="''no-repeat''!!'background-repeat' value">‘<code
class=css>no-repeat</code>’</dfn>
<dd>The image is placed once and not repeated in this direction.
</dl>
<p>Unless one of the two keywords is ‘<code
class=css>no-repeat</code>’, the whole background painting area will be
tiled, i.e., not just one vertical strip and one horizontal strip.
<div class=example>
<pre>
<!-- -->body {
<!-- --> background: white url("pendant.png");
<!-- --> background-repeat: repeat-y;
<!-- --> background-position: center;
<!-- -->}</pre>
<div class=figure>
<p><img
alt="A centered background image, with copies repeated up and down the border, padding and content areas."
src=bg-repeat><!--<SPAN class="dlink"> <A
name="img-bg-repeat" href="images/longdesc/bg-repeat-desc.html"
title="Long description for background pattern">[D]</A></SPAN>-->
<p class=caption>The effect of ‘<a href="#repeat-y"><code
class=css>repeat-y</code></a>’: One copy of the background image is
centered, and other copies are put above and below it to make a vertical
band behind the element.
</div>
</div>
<div class=example>
<pre>
<!-- -->body {
<!-- --> background-image: url(dot.png) white;
<!-- --> background-repeat: space
<!-- -->}
<!-- --></pre>
<div class=figure>
<p><img alt="Image of an element with a dotted background" src=bg-space>
<p class=caption>The effect of ‘<code class=property>space</code>’:
the image of a dot is tiled to cover the whole background and the images
are equally spaced.
</div>
</div>
<p>See the section <a href="#layering">“Layering multiple background
images”</a> for how ‘<a href="#background-repeat"><code
class=property>background-repeat</code></a>’ interacts with other
comma-separated background properties to form each background image layer.
<h3 id=the-background-attachment><span class=secno>3.5. </span> The ‘<a
href="#background-attachment"><code
class=property>background-attachment</code></a>’ property</h3>
<table class=propdef>
<tbody>
<tr>
<th>Name:
<td><dfn id=background-attachment>background-attachment</dfn>
<tr>
<th>Value:
<td><a href="#ltattachmentgt"><var><attachment></var></a> [ , <a
href="#ltattachmentgt"><var><attachment></var></a> ]*
<tr>
<th>Initial:
<td>scroll
<tr>
<th>Applies to:
<td>all elements
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed value:
<td>as specified
</table>
<p>If background images are specified, this property specifies whether they
are fixed with regard to the <em class=index id=viewport>viewport</em>
(<dfn id=fixed>‘<code class=css>fixed</code>’</dfn>) or scroll along
with the element (<dfn id=scroll>‘<code
class=css>scroll</code>’</dfn>) or its contents (<dfn id=local>‘<code
class=css>local</code>’</dfn>). The property's value is given as a
comma-separated list of <attachment> keywords where
<pre class=prod><dfn
id=ltattachmentgt><var><attachment></var></dfn> = scroll | fixed | local</pre>
<dl>
<dt><dfn id=fixed0>‘<code class=css>fixed</code>’</dfn>
<dd>The background is fixed with regard to the viewport. In paged media
where there is no viewport, a ‘<a href="#fixed0"><code
class=css>fixed</code></a>’ background is fixed with respect to the <a
href="http://www.w3.org/TR/CSS21/page.html#page-box">page box</a> and
therefore replicated on every page. <span class=note>Note that there is
only one viewport per view. Even if an element has a scrolling mechanism
(see the ‘<code class=property>overflow</code>’ property <a
href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>), a ‘<a
href="#fixed0"><code class=css>fixed</code></a>’ background doesn't
move with the element.</span>
<dt><dfn id=local0>‘<code class=css>local</code>’</dfn>
<dd>The background is fixed with regard to the element's contents: if the
element has a scrolling mechanism, the background scrolls with the
element's contents. In this case, the background behind the element's
border (if any) scrolls as well, even though the border itself does not
scroll with the contents. The UA may, however, treat the ‘<code
class=css>border-box</code>’ value of ‘<a
href="#background-clip"><code
class=property>background-clip</code></a>’ as ‘<code
class=css>padding-box</code>’ in cases where ‘<a
href="#background-attachment"><code
class=property>background-attachment</code></a>’ is ‘<a
href="#local0"><code class=css>local</code></a>’ and the contents of
the element scroll.
<dt><dfn id=scroll0>‘<code class=css>scroll</code>’</dfn>
<dd>The background is fixed with regard to the element itself and does not
scroll with its contents. (It is effectively attached to the element's
border.)
</dl>
<p>Even if the image is fixed, it is still only visible when it is in the
<a href="#background-painting-area"><em class=index
id=background-painting-area3>background painting area</em></a> of the
element or otherwise unclipped. (See <a href="#special-backgrounds">
“The backgrounds of special elements”</a> for the cases when
background images are not clipped.) Thus, unless the image is tiled, it
may be invisible.
<div class=example>
<p>This example creates an infinite vertical band that remains “glued”
to the viewport when the element is scrolled.
<pre>
<!-- -->body {
<!-- --> background: red url("pendant.gif");
<!-- --> background-repeat: repeat-y;
<!-- --> background-attachment: fixed;
<!-- -->}</pre>
</div>
<p>User agents that do not support ‘<a href="#fixed0"><code
class=css>fixed</code></a>’ backgrounds (for example due to limitations
of the hardware platform) should ignore declarations with the keyword
‘<a href="#fixed0"><code class=css>fixed</code></a>’. For example:
<pre class=example>
<!-- -->body {
<!-- --> /* For all UAs: */
<!-- --> background: white url(paper.png) scroll;
<!-- --> /* For UAs that do fixed backgrounds: */
<!-- --> background: white url(ledger.png) fixed;
<!-- -->}
<!-- -->h1 {
<!-- --> /* For all UAs: */
<!-- --> background: silver;
<!-- --> /* For UAs that do fixed backgrounds: */
<!-- --> background: url(stripe.png) fixed, white url(ledger.png) fixed;
<!-- -->}</pre>
<p>See the section <a href="#layering">“Layering multiple background
images”</a> for how ‘<a href="#background-attachment"><code
class=property>background-attachment</code></a>’ interacts with other
comma-separated background properties to form each background image layer.
<h3 id=the-background-position><span class=secno>3.6. </span> The ‘<a
href="#background-position"><code
class=property>background-position</code></a>’ property</h3>
<table class=propdef>
<tbody>
<tr>
<th>Name:
<td><dfn id=background-position>background-position</dfn>
<tr>
<th>Value:
<td><a href="#ltpositiongt"><var><position></var></a> [ , <a
href="#ltpositiongt"><var><position></var></a> ]*
<tr>
<th>Initial:
<td>0% 0%
<tr>
<th>Applies to:
<td>all elements
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>refer to size of <a class=index href="#background-positioning-area"
id=background-positioning-area1>background positioning area</a>
<em>minus</em> size of background image; see text
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed value:
<td>A list, each item consisting of: two keywords representing the
origin and two offsets from that origin, each given as an absolute
length (if given a <length>), otherwise as a percentage.
</table>
<p>If background images have been specified, this property specifies their
initial position (after any <a href="#the-background-size">resizing</a>)
within their corresponding <a
href="#background-positioning-area"><i>background positioning
area</i></a>.
<p>Where
<pre class=prod><dfn id=ltpositiongt><var><position></var></dfn> = [
<!-- --> [ top | bottom ]
<!-- -->|
<!-- --> [ <var><percentage></var> | <var><length></var> | left | center | right ]
<!-- --> [ <var><percentage></var> | <var><length></var> | top | center | bottom ]?
<!-- -->|
<!-- --> [ center | [ left | right ] [ <var><percentage></var> | <var><length></var> ]? ] &&
<!-- --> [ center | [ top | bottom ] [ <var><percentage></var> | <var><length></var> ]? ]
<!-- -->]</pre>
<p>If only one value is specified, the second value is assumed to be
‘<code class=property>center</code>’. If two values are given and at
least one value is not a keyword, then the first value represents the
horizontal position (or offset) and the second represents the vertical
position (or offset). <var><percentage></var> and
<var><length></var> values here represent an offset of the top left
corner of the background image from the top left corner of the background
positioning area.
<p>If three or four values are given, then each
<var><percentage></var> or<var><length></var> represents an
offset and must be preceded by a keyword, which specifies from which edge
the offset is given. For example, ‘<code class=css>background-position:
bottom 10px right 20px</code>’ represents a ‘<code
class=css>10px</code>’ vertical offset up from the bottom edge and a
‘<code class=css>20px</code>’ horizontal offset leftward from the
right edge. If three values are given, the missing offset is assumed to be
zero.
<p>Positive values represent an offset <em>inward</em> from the edge of the
background positioning area. Negative values represent an offset
<em>outward</em> from the edge of the background positioning area.
<div class=example>
<p>The following declarations give the stated (horizontal, vertical)
offsets from the top left corner:
<pre>
<!-- -->background-position: left 10px top 15px; /* 10px, 15px */
<!-- -->background-position: left top ; /* 0px, 0px */
<!-- -->background-position: 10px 15px; /* 10px, 15px */
<!-- -->background-position: left 15px; /* 0px, 15px */
<!-- -->background-position: 10px top ; /* 10px, 0px */
<!-- -->background-position: left top 15px; /* 0px, 15px */
<!-- -->background-position: left 10px top ; /* 10px, 0px */</pre>
</div>
<dl>
<dt><var><percentage></var>