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<title>CSS Round Display Level 1</title>
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<h1 class="p-name no-ref" id="title">CSS Round Display Level 1</h1>
<h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="content">Editor’s Draft,
<time class="dt-updated" datetime="2015-03-08">8 March 2015</time></span></h2>
<div data-fill-with="spec-metadata">
<dl>
<dt>This version:
<dd><a class="u-url" href="N/A">N/A</a>
<dt>Feedback:
<dd><span><a href="mailto:www-style@w3.org?subject=%5Bround-display%5D%20feedback">www-style@w3.org</a> with subject line “<kbd>[round-display] <var>… message topic …</var></kbd>” (<a href="http://lists.w3.org/Archives/Public/www-style/" rel="discussion">archives</a>)</span>
<dt>Issue Tracking:
<dd><a href="#issues-index">Inline In Spec</a>
<dt class="editor">Editors:
<dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:hyojin22.song@lge.com">Hyojin Song</a> (<span class="p-org org">LG Electronics</span>)
<dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:soonbo.han@lge.com">Soonbo Han</a> (<span class="p-org org">LG Electronics</span>)
</dl>
</div>
<div data-fill-with="warning"></div>
<p class="copyright" data-fill-with="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2015 <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>). 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>
<hr title="Separator for header">
</div>
<h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2>
<div class="p-summary" data-fill-with="abstract">
<p>This document proposes CSS extensions to support a round display. It extends existing CSS features including Media Queries<a data-link-type="biblio" href="#biblio-mediaq">[MEDIAQ]</a>, CSS Shapes<a data-link-type="biblio" href="#biblio-css-shapes-1">[CSS-SHAPES-1]</a>, Borders<a data-link-type="biblio" href="#biblio-css3-border">[CSS3-BORDER]</a>, and Positioned Layout<a data-link-type="biblio" href="#biblio-css3-positioning">[CSS3-POSITIONING]</a>. The extensions will help web authors to build a web page suitable for a round display.</p>
<a href="http://www.w3.org/TR/CSS/">CSS</a> is a language for describing the rendering of structured documents
(such as HTML and XML)
on screen, on paper, in speech, etc.</div>
<h2 class="no-num no-toc no-ref heading settled" id="status"><span class="content">Status of this document</span></h2>
<div data-fill-with="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=%5Bround-display%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 “round-display” in the subject,
preferably like this:
“[round-display] <em>…summary of comment…</em>”
</p>
<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>
<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>
<p>
This document is governed by the <a href="http://www.w3.org/2014/Process-20140801/" id="w3c_process_revision">1 August 2014 W3C Process Document</a>.
</p>
<p>
</p></div>
<div data-fill-with="at-risk"></div>
<h2 class="no-num no-toc no-ref heading settled" id="contents"><span class="content">Table of Contents</span></h2>
<div data-fill-with="table-of-contents" role="navigation">
<ul class="toc" role="directory">
<li><a href="#introduction"><span class="secno">1</span> <span class="content">Introduction</span></a>
<li><a href="#terminology"><span class="secno">2</span> <span class="content">Terminology</span></a>
<li><a href="#extending-media-queries-for-a-round-display"><span class="secno">3</span> <span class="content">Extending Media Queries for a round display</span></a>
<ul class="toc">
<li><a href="#the-device_radius-media-feature"><span class="secno">3.1</span> <span class="content">The <span class="property">device-radius</span> media feature</span></a>
</ul>
<li><a href="#aligning-content-along-the-display-border"><span class="secno">4</span> <span class="content">Aligning content along the display border</span></a>
<ul class="toc">
<li><a href="#the-shape_inside-property"><span class="secno">4.1</span> <span class="content">The <span class="property">shape-inside</span> property</span></a>
</ul>
<li><a href="#drawing-borders-around-the-display-border"><span class="secno">5</span> <span class="content">Drawing borders around the display border</span></a>
<ul class="toc">
<li><a href="#the-border_boundary-property"><span class="secno">5.1</span> <span class="content">The <span class="property">border-boundary</span> property</span></a>
</ul>
<li><a href="#positioning-content-by-using-the-polar-coordinate-system"><span class="secno">6</span> <span class="content">Positioning content by using the polar coordinate system</span></a>
<ul class="toc">
<li><a href="#the-position-property"><span class="secno">6.1</span> <span class="content">The <span class="property">position</span> property</span></a>
<li><a href="#the-polar_angle-property"><span class="secno">6.2</span> <span class="content">The <span class="property">polar-angle</span> property</span></a>
<li><a href="#the-polar_distance-property"><span class="secno">6.3</span> <span class="content">The <span class="property">polar-distance</span> property</span></a>
</ul>
<li><a href="#conformance"><span class="secno"></span> <span class="content">
Conformance</span></a>
<ul class="toc">
<li><a href="#conventions"><span class="secno"></span> <span class="content">
Document conventions</span></a>
<li><a href="#conformance-classes"><span class="secno"></span> <span class="content">
Conformance classes</span></a>
<li><a href="#partial"><span class="secno"></span> <span class="content">
Partial implementations</span></a>
<li><a href="#experimental"><span class="secno"></span> <span class="content">
Experimental implementations</span></a>
<li><a href="#testing"><span class="secno"></span> <span class="content">
Non-experimental implementations</span></a>
</ul>
<li><a href="#index"><span class="secno"></span> <span class="content">Index</span></a>
<ul class="toc">
<li><a href="#index-defined-here"><span class="secno"></span> <span class="content">Terms defined by this specification</span></a>
<li><a href="#index-defined-elsewhere"><span class="secno"></span> <span class="content">Terms defined by reference</span></a>
</ul>
<li><a href="#references"><span class="secno"></span> <span class="content">References</span></a>
<ul class="toc">
<li><a href="#normative"><span class="secno"></span> <span class="content">Normative References</span></a>
<li><a href="#informative"><span class="secno"></span> <span class="content">Informative References</span></a>
</ul>
<li><a href="#property-index"><span class="secno"></span> <span class="content">Property Index</span></a>
<ul class="toc">
<li><a href="#media-descriptor-table"><span class="secno"></span> <span class="content"><span>@media</span> Descriptors</span></a>
</ul>
<li><a href="#issues-index"><span class="secno"></span> <span class="content">Issues Index</span></a>
</ul></div>
<main>
<h2 class="heading settled" data-level="1" id="introduction"><span class="secno">1. </span><span class="content">Introduction</span><a class="self-link" href="#introduction"></a></h2>
<p>
Everything on the web is a rectangle. For example, the window content area in a web browser is a rectangle. Each HTML element follows the W3C box model and thus is also a rectangle. New devices with a round display are now emerging. The current web standards lack some features to support the devices as follows:
</p>
<ol>
<li>Lack of the capability to detect a round display
<li>Lack of layout mechanisms suitable for a round display
</ol>
In order to facilitate the use of the web on a round display, we need to rethink existing CSS features.
<p></p>
<p>
Current user agents are not capable of detecting the shape of a display so that authors cannot apply a different layout for a round display. To resolve the issue, we propose to add the <a class="property" data-link-type="propdesc" href="#descdef-media-device-radius">device-radius</a> media feature to Media Queries. The feature informs the web page of the property regarding the shape of the display.
</p>
<p>
To apply the shape of a display to content area, we propose to extend the <a class="property" data-link-type="propdesc" href="#propdef-shape-inside">shape-inside</a> property of CSS Shapes. We also propose to add the <a class="property" data-link-type="propdesc" href="#propdef-border-boundary">border-boundary</a> property to CSS Borders and introduce polar positioning for a better web design suitable for a round display.
</p>
<h2 class="heading settled" data-level="2" id="terminology"><span class="secno">2. </span><span class="content">Terminology</span><a class="self-link" href="#terminology"></a></h2>
This specification follows the CSS property definition conventions from <a data-link-type="biblio" href="#biblio-css21">[CSS21]</a>. <br>
The detailed description of Media Queries is defined in <a data-link-type="biblio" href="#biblio-mediaq">[MEDIAQ]</a><br>
The detailed description of CSS Shapes is defined in <a data-link-type="biblio" href="#biblio-css-shapes-1">[CSS-SHAPES-1]</a><br>
The detailed description of Borders is defined in <a data-link-type="biblio" href="#biblio-css3-border">[CSS3-BORDER]</a><br>
The detailed description of Positioned Layout is defined in <a data-link-type="biblio" href="#biblio-css3-positioning">[CSS3-POSITIONING]</a><br>
<h2 class="heading settled" data-level="3" id="extending-media-queries-for-a-round-display"><span class="secno">3. </span><span class="content">Extending Media Queries for a round display</span><a class="self-link" href="#extending-media-queries-for-a-round-display"></a></h2>
<p>
Media Queries <a data-link-type="biblio" href="#biblio-mediaq">[MEDIAQ]</a> define mechanisms to support media-dependent style sheets, tailored for different media types. We propose to extend Media Queries by adding the <a class="property" data-link-type="propdesc" href="#descdef-media-device-radius">device-radius</a> media feature to support a round display. This will allow web authors to apply different styles to a web page on the rounded display.
</p>
<section>
<h3 class="heading settled" data-level="3.1" id="the-device_radius-media-feature"><span class="secno">3.1. </span><span class="content">The <a class="property" data-link-type="propdesc" href="#descdef-media-device-radius">device-radius</a> media feature</span><a class="self-link" href="#the-device_radius-media-feature"></a></h3>
To use different style sheets for a rectangle display and for a round display, media queries should support some properties to identify the display shape. The <a class="property" data-link-type="propdesc" href="#descdef-media-device-radius">device-radius</a> media feature describes the property of rounded borders of a display.
<div class="example">
This media query indicates that different style sheets will be applied depending on the display shape.
<pre>&lt;link media="screen and (max-device-radius: 49%)" rel="stylesheet" href="rectangle.css" />
&lt;link media="screen and (min-device-radius: 50%)" rel="stylesheet" href="round.css" /></pre>
</div>
<p>
This media feature accepts optional '<code>min-</code>' or '<code>max-</code>' prefixes to express 'greater or equal to' and 'smaller or equal to' contstriants. By the mechanism of media queries, if the value of the <a class="property" data-link-type="propdesc" href="#descdef-media-device-radius">device-radius</a> media feature is less than or equal to 49%, '<code>rectangle-clock.css</code>' is applied. If it is 50%, '<code>round-clock.css</code>' is applied.
</p>
<p>As in the '<code>border-radius</code>' property, the <a class="property" data-link-type="propdesc" href="#descdef-media-device-radius">device-radius</a> media feature can describe various round shapes of displays, such as rectangle, regular circle, ellipse, and rectangle with round corners.
</p>
<table class="definition descdef">
<tbody>
<tr>
<th>Name:
<td><dfn class="css" data-dfn-for="@media" data-dfn-type="descriptor" data-export="" id="descdef-media-device-radius">device-radius<a class="self-link" href="#descdef-media-device-radius"></a></dfn>
<tr>
<th>For:
<td><a class="css" data-link-type="at-rule" href="http://dev.w3.org/csswg/css-conditional-3/#at-ruledef-media">@media</a>
<tr>
<th>Value:
<td class="prod">[ <a class="production css" data-link-type="type" href="http://dev.w3.org/csswg/css-values-3/#length-value">&lt;length></a> <a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#comb-one">|</a> <a class="production css" data-link-type="type" href="http://dev.w3.org/csswg/css-values-3/#percentage-value">&lt;percentage></a> ]
<tr>
<th>Initial:
<td>0
<tr>
<th>Percentage:
<td>Refer to corresponding dimension of the display
<tr>
<th>Type:
<td>range</table>
<p>
The example below shows how a web page looks in the different shape of displays.
</p>
<div class="example">
Here is an example of a simple clock written in HTML (without <a class="property" data-link-type="propdesc" href="#descdef-media-device-radius">device-radius</a>):
<pre>&lt;!DOCTYPE html>
&lt;html>
&lt;head>
&lt;link rel="stylesheet" href="rectangle.css" />
&lt;/head>
&lt;body>
&lt;div id="clockLayer">
&lt;div id="clockLayer">
&lt;div id="date">2015/02/28 (SAT)&lt;/div>
&lt;div id="time">10:11&lt;/div>
&lt;div id="weather">&lt;img src="cloudy.png" />&lt;/div>
&lt;/div>
&lt;/div>
&lt;/body>
&lt;/html>
</pre>
</div>
<div style="width: 700px; height: 380px; text-align:center">
<div style="float: left; width: 350px;">
<img src="images/clock_a.png">
<p>(A) Rectangle Display</p>
</div>
<div style="float: left; ">
<img src="images/clock_c.png">
<p>(B) Round Display</p>
</div>
</div>
<div style="width: 700px">
<p class="caption">Devices where the <a class="property" data-link-type="propdesc" href="#descdef-media-device-radius">device-radius</a> media feature is not applicable</p>
</div>
<p>On the other hand, the example below shows how the <a class="property" data-link-type="propdesc" href="#descdef-media-device-radius">device-radius</a> media feature works in the different shape of displays.</p>
<div class="example">
The HTML code of this example is the same as that of EXAMPLE 2 except of media queries usage. The <a class="property" data-link-type="propdesc" href="#descdef-media-device-radius">device-radius</a> property can be used as follows:
<pre>&lt;!-- index.html -->
&lt;head>
&lt;link media="screen and (max-device-radius: 49%)" rel="stylesheet" href="rectangle.css" />
&lt;link media="screen and (min-device-radius: 50%)" rel="stylesheet" href="round.css" />
&lt;/head>
</pre>
<p>If this example code is loaded in a regular round display, '<code>round.css</code>' will be applied by the media queries mechanism. To render the clock properly, '<code>round.css</code>' could be written as follows.</p>
<pre>#clockLayer {
border-radius: 50%;
}
#clockInset {
border-radius: 50%;
}
#date {
text-align: center;
}
...
</pre>
</div>
<div style="width: 700px; height: 380px; text-align:center">
<div style="float: left; width: 350px;">
<img src="images/clock_a.png">
<p>(A) Rectangle Display<br>(w/ <code>device-radius: 0%</code>)</p>
</div>
<div style="float: left; ">
<img src="images/clock_b.png">
<p>(B) Round Display<br>(w/ <code>device-radius: 50%</code>)</p>
</div>
</div>
<div style="width: 700px">
<p class="caption">Devices where the <a class="property" data-link-type="propdesc" href="#descdef-media-device-radius">device-radius</a> media feature is applicable</p>
A933
</div>
<p class="note" role="note">If the shapes of displays are various, such as polygons, we need to extend the media features more with additional parameters. The current features have limitations to support the diversity beyond round shapes. How can we express star-shaped polygons? (E.g., SVG syntax, etc.) Of course, there is a trade-off between simplicity and expressiveness.
</p>
<p class="issue" id="issue-b9e1e387"><a class="self-link" href="#issue-b9e1e387"></a>
Using <a class="property" data-link-type="propdesc" href="#descdef-media-device-radius">device-radius</a> with just a single value (e.g., device-radius: 50%) is enough (for simplicity)? Otherwise, do we need to support all possible values the same as <a class="property" data-link-type="propdesc" href="http://dev.w3.org/csswg/css-backgrounds-3/#border-radius">border-radius</a>?
</p>
<h2 class="heading settled" data-level="4" id="aligning-content-along-the-display-border"><span class="secno">4. </span><span class="content">Aligning content along the display border</span><a class="self-link" href="#aligning-content-along-the-display-border"></a></h2>
<h3 class="heading settled" data-level="4.1" id="the-shape_inside-property"><span class="secno">4.1. </span><span class="content">The <a class="property" data-link-type="propdesc" href="#propdef-shape-inside">shape-inside</a> property</span><a class="self-link" href="#the-shape_inside-property"></a></h3>
<p>
CSS Shapes <a data-link-type="biblio" href="#biblio-css-shapes">[CSS-SHAPES]</a> define the <a class="property" data-link-type="propdesc" href="#propdef-shape-inside">shape-inside</a> property that aligns contents along a possibly non-rectangular wrapping area. Web authors may use this feature to fit contents inside a round display. However, it could sometimes be hard to specify the wrapping area identical to the shape of a display. Thus, we propose to add a new value '<code>display</code>' to the <a class="property" data-link-type="propdesc" href="#propdef-shape-inside">shape-inside</a> property to facilitate it. When the <a class="property" data-link-type="propdesc" href="#propdef-shape-inside">shape-inside</a> property on an element is set to '<code>display</code>', its content (or contained element) is aligned along the display border automatically.
</p>
<table class="definition propdef">
<tbody>
<tr>
<th>Name:
<td><dfn class="css" data-dfn-type="property" data-export="" id="propdef-shape-inside">shape-inside<a class="self-link" href="#propdef-shape-inside"></a></dfn>
<tr>
<th>Value:
<td class="prod">auto <a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#comb-one">|</a> outside-shape <a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#comb-one">|</a> [ <a class="production css" data-link-type="type" href="http://dev.w3.org/csswg/css-shapes-2/#typedef-basic-shape">&lt;basic-shape></a> <a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#comb-any">||</a> shape-box ] <a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#comb-one">|</a> <a class="production css" data-link-type="type" href="http://dev.w3.org/csswg/css-images-3/#typedef-image">&lt;image></a> <a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#comb-one">|</a> <code>display</code>
<tr>
<th>Initial:
<td>auto
<tr>
<th>Applies to:
<td>block-level elements
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>n/a
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed value:
<td>computed lengths for <a class="production css" data-link-type="type" href="http://dev.w3.org/csswg/css-shapes-2/#typedef-basic-shape" title="Expands to: ">&lt;basic-shape></a>, the absolute URI for <a class="production css" data-link-type="type" href="http://dev.w3.org/csswg/css-shapes-2/#typedef-uri">&lt;uri></a>, otherwise as specified
<tr>
<th>Animatable:
<td>as specified for <a class="production css" data-link-type="type" href="http://dev.w3.org/csswg/css-shapes-2/#typedef-basic-shape" title="Expands to: ">&lt;basic-shape></a>, otherwise no</table>
<p>The example below shows how the <a class="property" data-link-type="propdesc" href="#propdef-shape-inside">shape-inside</a> property works when it is set to '<code>display</code>'.</p>
<div class="example">
<pre>&lt;style>
#container {
#shape-inside: display;
// the same as circle(50% at 50%, 50%) in a regular round display
}
#green-box { float: left; }
#blue-box { float: right; }
&lt;/style>
&lt;div id="container">
&lt;p>
Some inline content
&lt;img id="green-box" src="green-box.jpg" />
with a float left and float right, in a
&lt;img id="blue-box" src="blue-box.jpg" />
simple box with a circle #shape-inside.
&lt;/p>
&lt;/div>
</pre>
</div>
<div style="width: 500px; height: 380px; text-align:center">
<div style="float: left; width: 250px;">
<img src="images/watch_b.png" style="width: 250px">
<p>(A) Without '<code>shape-inside</code>'</p>
</div>
<div style="float: left; width: 250px;">
<img src="images/watch_c.png" style="width: 250px">
<p>(B) With '<code>shape-inside: display</code>'</p>
</div>
</div>
<div style="width: 500px">
<p class="caption">Align the content along the display border</p>
</div>
<div style="width: 500px;">
<img src="images/ex3.png" style="width: 500px">
<p class="caption">Align a part of the content along the display border</p>
</div>
<p class="issue" id="issue-8d78506c"><a class="self-link" href="#issue-8d78506c"></a>
What if content overflows? Clipping or scrolling?
</p>
<h2 class="heading settled" data-level="5" id="drawing-borders-around-the-display-border"><span class="secno">5. </span><span class="content">Drawing borders around the display border</span><a class="self-link" href="#drawing-borders-around-the-display-border"></a></h2>
<h3 class="heading settled" data-level="5.1" id="the-border_boundary-property"><span class="secno">5.1. </span><span class="content">The <a class="property" data-link-type="propdesc" href="#propdef-border-boundary">border-boundary</a> property</span><a class="self-link" href="#the-border_boundary-property"></a></h3>
<p>
We propose the <a class="property" data-link-type="propdesc" href="#propdef-border-boundary">border-boundary</a> property to set a boundary constraint that affects the borders of an element.
</p>
<table class="definition propdef">
<tbody>
<tr>
<th>Name:
<td><dfn class="css" data-dfn-type="property" data-export="" id="propdef-border-boundary">border-boundary<a class="self-link" href="#propdef-border-boundary"></a></dfn>
<tr>
<th>Value:
<td class="prod">none <a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#comb-one">|</a> parent <a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#comb-one">|</a> <code>display</code>
<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
<tr>
<th>Animatable:
<td>no</table>
<p>
When the <a class="property" data-link-type="propdesc" href="#propdef-border-boundary">border-boundary</a> property on an element is set to '<code>parent</code>', additional borders of the element could be drawn where the element’s area and the borders of its parent are met. When it is set to '<code>display</code>', additional borders could be drawn where the element’s area and the borders of screen are met. The default value is '<code>none</code>', imposing no boundary constraint on the borders.
</p>
<div class="example">
The example below shows how the <a class="property" data-link-type="propdesc" href="#propdef-border-boundary">border-boundary</a> property works on drawing borders. The result is shown in Figure 5B.
<pre>&lt;style>
#container {
border-boundary: display;
}
#redBox {
border: 5px red solid;
}
#greenBox {
border: 5px green solid;
}
#blueBox {
border: 5px blue solid;
}
&lt;/style>
&lt;div id="container">
&lt;div id="redBox">&lt;/div>
&lt;div id="greenBox">&lt;/div>
&lt;div id="blueBox">&lt;/div>
&lt;/div>
</pre>
</div>
<div style="width: 600px; text-align:center">
<div style="float: left; width: 300px;">
<img src="images/border_b.png" style="width: 200px">
<p>(A) Without '<code>border-boundary</code>'</p>
</div>
<div style="float: left; width: 300px; ">
<img src="images/border_c.png" style="width: 200px">
<p>(B) With '<code>border-boundary: display</code>'</p>
</div>
</div>
<div style="width: 600px">
<p class="caption">Align the content along the display border</p>
</div>
<h2 class="heading settled" data-level="6" id="positioning-content-by-using-the-polar-coordinate-system"><span class="secno">6. </span><span class="content">Positioning content by using the polar coordinate system</span><a class="self-link" href="#positioning-content-by-using-the-polar-coordinate-system"></a></h2>
<p>
Elements are often placed along a circle or concentric circles, and polar coordinates are useful to handle such cases. This section introduces polar positioning to support layout of elements in the polar coordinate system where the position of an element is determined by a distance from a fixed point within the containing element and an angle from a fixed direction. We propose to add '<code>polar</code>' to the value of the <a class="property" data-link-type="propdesc" href="#propdef-position">position</a> property to support the polar coordinates of the children of an element. The <a class="property" data-link-type="propdesc" href="#propdef-polar-angle">polar-angle</a> and <a class="property" data-link-type="propdesc" href="#propdef-polar-distance">polar-distance</a> properties specify the position of an element (or a child).
</p>
<h3 class="heading settled" data-level="6.1" id="the-position-property"><span class="secno">6.1. </span><span class="content">The <a class="property" data-link-type="propdesc" href="#propdef-position">position</a> property</span><a class="self-link" href="#the-position-property"></a></h3>
When the <a class="property" data-link-type="propdesc" href="#propdef-position">position</a> property on an element is set to '<code>polar</code>', its children use the polar coordinates.
<table class="definition propdef">
<tbody>
<tr>
<th>Name:
<td><dfn class="css" data-dfn-type="property" data-export="" id="propdef-position">position<a class="self-link" href="#propdef-position"></a></dfn>
<tr>
<th>Value:
<td class="prod">static <a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#comb-one">|</a> relative <a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#comb-one">|</a> absolute <a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#comb-one">|</a> fixed <a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#comb-one">|</a> inherit <a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#comb-one">|</a> <code>polar</code>
<tr>
<th>Initial:
<td>static
<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
<tr>
<th>Animatable:
<td>no</table>
<h3 class="heading settled" data-level="6.2" id="the-polar_angle-property"><span class="secno">6.2. </span><span class="content">The <a class="property" data-link-type="propdesc" href="#propdef-polar-angle">polar-angle</a> property</span><a class="self-link" href="#the-polar_angle-property"></a></h3>
The <a class="property" data-link-type="propdesc" href="#propdef-polar-angle">polar-angle</a> property specifies the angle from the X-axis (or a fixed direction).
<table class="definition propdef">
<tbody>
<tr>
<th>Name:
<td><dfn class="css" data-dfn-type="property" data-export="" id="propdef-polar-angle">polar-angle<a class="self-link" href="#propdef-polar-angle"></a></dfn>
<tr>
<th>Value:
<td class="prod">[ <a class="production css" data-link-type="type" href="http://dev.w3.org/csswg/css-values-3/#length-value" title="Expands to: ">&lt;length></a> <a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#comb-one">|</a> <a class="production css" data-link-type="type" href="http://dev.w3.org/csswg/css-values-3/#percentage-value" title="Expands to: ">&lt;percentage></a> ]<a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#mult-opt">?</a>
<tr>
<th>Initial:
<td>0
<tr>
<th>Applies to:
<td>all elements (parents should have 'position: polar' property)
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>relative to radius of circle
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed value:
<td>as specified
<tr>
<th>Animatable:
<td>no
<tr>
<th>For:
<td>@media</table>
<h3 class="heading settled" data-level="6.3" id="the-polar_distance-property"><span class="secno">6.3. </span><span class="content">The <a class="property" data-link-type="propdesc" href="#propdef-polar-distance">polar-distance</a> property</span><a class="self-link" href="#the-polar_distance-property"></a></h3>
The <a class="property" data-link-type="propdesc" href="#propdef-polar-distance">polar-distance</a> property specifies the distance from the center of the parent (or a fixed point).
<table class="definition propdef">
<tbody>
<tr>
<th>Name:
<td><dfn class="css" data-dfn-type="property" data-export="" id="propdef-polar-distance">polar-distance<a class="self-link" href="#propdef-polar-distance"></a></dfn>
<tr>
<th>Value:
<td class="prod">[ <a class="production css" data-link-type="type" href="http://dev.w3.org/csswg/css-values-3/#length-value" title="Expands to: ">&lt;length></a> <a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#comb-one">|</a> <a class="production css" data-link-type="type" href="http://dev.w3.org/csswg/css-values-3/#percentage-value" title="Expands to: ">&lt;percentage></a> ]<a data-link-type="grammar" href="http://dev.w3.org/csswg/css-values-3/#mult-opt">?</a>
<tr>
<th>Initial:
<td>0
<tr>
<th>Applies to:
<td>all elements (parents should have 'position: polar' property)
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>relative to radius of circle
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed value:
<td>as specified
<tr>
<th>Animatable:
<td>no
<tr>
<th>For:
<td>@media</table>
<div class="example">
This example shows a way to align elements within the polar coordinates system.
<pre>&lt;body style="position: polar;">
&lt;div id="circle1" style="polar-angle: 0deg; polar-distance: 20%">&lt;/div>
&lt;div id="circle2" style="polar-angle: 90deg; polar-distance: 50%">&lt;/div>
&lt;div id="circle3" style="polar-angle: 225deg; polar-distance: 100%">&lt;/div>
&lt;/body>
</pre>
</div>
<div style="width: 400px; text-align: center">
<img src="images/polar.png" style="width: 200px; border: 1px #AAA solid; text-align: center">
<p class="caption">An example of polar positioning</p>
</div>
<p class="issue" id="issue-8cbcc1b5"><a class="self-link" href="#issue-8cbcc1b5"></a>
By default, the <a class="property" data-link-type="propdesc" href="#propdef-polar-distance">polar-distance</a> property specifies the distance from the origin (or the center) of the containing element to that of the contained element. The <a class="property" data-link-type="propdesc" href="#propdef-polar-angle">polar-angle</a> property specifies the angle from the X-axis to the center of the contained element.
</p>
<p class="issue" id="issue-d86b8048"><a class="self-link" href="#issue-d86b8048"></a>
What value does the percentage value of the <a class="property" data-link-type="propdesc" href="#propdef-polar-distance">polar-distance</a> property refer to? The width of the containing element, or what? One feasible solution is to use the distance between the origin and the point on the border at the angle given by the <a class="property" data-link-type="propdesc" href="#propdef-polar-angle">polar-angle</a> property from the X-axis.
</p>
<p class="issue" id="issue-09c5924d"><a class="self-link" href="#issue-09c5924d"></a>
Will an element (or a child) itself be rotated through the <a class="property" data-link-type="propdesc" href="#propdef-polar-angle">polar-angle</a> property?
</p>
</section></main>
< 289D div id="LC749" class="react-file-line html-div" data-testid="code-cell" data-line-number="749" style="position:relative"> <h2 class="no-ref no-num heading settled" id="conformance"><span class="content">
Conformance</span><a class="self-link" href="#conformance"></a></h2>
<h3 class="no-ref heading settled" id="conventions"><span class="content">
Document conventions</span><a class="self-link" href="#conventions"></a></h3>
<p>Conformance requirements are expressed with a combination of
descriptive assertions and RFC 2119 terminology. The key words "MUST",
"MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" in the normative parts of this
document are to be interpreted as described in RFC 2119.
However, for readability, these words do not appear in all uppercase
letters in this specification.
</p>
<p>All of the text of this specification is normative except sections
explicitly marked as non-normative, examples, and notes. <a data-link-type="biblio" href="#biblio-rfc2119">[RFC2119]</a></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:
</p>
<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>
<p class="note" role="note">Note, this is an informative note.</p>
<p>Advisements are normative sections styled to evoke special attention and are
set apart from other normative text with <code>&lt;strong class="advisement"></code>, like
this:
<strong class="advisement">
UAs MUST provide an accessible alternative.
</strong>
</p>
<h3 class="no-ref heading settled" id="conformance-classes"><span class="content">
Conformance classes</span><a class="self-link" href="#conformance-classes"></a></h3>
<p>Conformance to this specification
is defined for three conformance classes:
</p>
<dl>
<dt>style sheet
<dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS
style sheet</a>.
<dt>renderer
<dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
that interprets the semantics of a style sheet and renders
documents that use them.
<dt>authoring tool
<dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
that writes a style sheet.
</dl>
<p>A style sheet is conformant to this specification
if all of its statements that use syntax defined in this module are valid
according to the generic CSS grammar and the individual grammars of each
feature defined in this module.
</p>
<p>A renderer is conformant to this specification
if, in addition to interpreting the style sheet as defined by the
appropriate specifications, it supports all the features defined
by this specification by parsing them correctly
and rendering the document accordingly. However, the inability of a
UA to correctly render a document due to limitations of the device
does not make the UA non-conformant. (For example, a UA is not
required to render color on a monochrome monitor.)
</p>
<p>An authoring tool is conformant to this specification
if it writes style sheets that are syntactically correct according to the
generic CSS grammar and the individual grammars of each feature in
this module, and meet all other conformance requirements of style sheets
as described in this module.
</p>
<h3 class="no-ref heading settled" id="partial"><span class="content">
Partial implementations</span><a class="self-link" href="#partial"></a></h3>
<p>So that authors can exploit the forward-compatible parsing rules to
assign fallback values, CSS renderers <strong>must</strong>
treat as invalid (and <a href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignore
as appropriate</a>) any at-rules, properties, property values, keywords,
and other syntactic constructs for which they have no usable level of
support. In particular, user agents <strong>must not</strong> selectively
ignore unsupported component values and honor supported values in a single
multi-value property declaration: if any value is considered invalid
(as unsupported values must be), CSS requires that the entire declaration
be ignored.</p>
<h3 class="no-ref heading settled" id="experimental"><span class="content">
Experimental implementations</span><a class="self-link" href="#experimental"></a></h3>
<p>To avoid clashes with future CSS features, the CSS2.1 specification
reserves a <a href="http://www.w3.org/TR/CSS21/syndata.html#vendor-keywords">prefixed
syntax</a> for proprietary and experimental extensions to CSS.
</p>
<p>Prior to a specification reaching the Candidate Recommendation stage
in the W3C process, all implementations of a CSS feature are considered
experimental. The CSS Working Group recommends that implementations
use a vendor-prefixed syntax for such features, including those in
W3C Working Drafts. This avoids incompatibilities with future changes
in the draft.
</p>
<h3 class="no-ref heading settled" id="testing"><span class="content">
Non-experimental implementations</span><a class="self-link" href="#testing"></a></h3>
<p>Once a specification reaches the Candidate Recommendation stage,
non-experimental implementations are possible, and implementors should
release an unprefixed implementation of any CR-level feature they
can demonstrate to be correctly implemented according to spec.
</p>
<p>To establish and maintain the interoperability of CSS across
implementations, the CSS Working Group requests that non-experimental
CSS renderers submit an implementation report (and, if necessary, the
testcases used for that implementation report) to the W3C before
releasing an unprefixed implementation of any CSS features. Testcases
submitted to W3C are subject to review and correction by the CSS
Working Group.
</p>
<p>Further information on submitting testcases and implementation reports
can be found from on the CSS Working Group’s website at
<a href="http://www.w3.org/Style/CSS/Test/">http://www.w3.org/Style/CSS/Test/</a>.
Questions should be directed to the
<a href="http://lists.w3.org/Archives/Public/public-css-testsuite">public-css-testsuite@w3.org</a>
mailing list.
</p>
<h2 class="no-num heading settled" id="index"><span class="content">Index</span><a class="self-link" href="#index"></a></h2>
<h3 class="no-num heading settled" id="index-defined-here"><span class="content">Terms defined by this specification</span><a class="self-link" href="#index-defined-here"></a></h3>
<ul class="indexlist">
<li>border-boundary, <a href="#propdef-border-boundary">5.1</a>
<li>device-radius, <a href="#descdef-media-device-radius">3.1</a>
<li>polar-angle, <a href="#propdef-polar-angle">6.2</a>
<li>polar-distance, <a href="#propdef-polar-distance">6.3</a>
<li>position, <a href="#propdef-position">6.1</a>
<li>shape-inside, <a href="#propdef-shape-inside">4.1</a>
</ul>
<h3 class="no-num heading settled" id="index-defined-elsewhere"><span class="content">Terms defined by reference</span><a class="self-link" href="#index-defined-elsewhere"></a></h3>
<ul class="indexlist">
<li><a data-link-type="biblio" href="#biblio-css-backgrounds-3">[css-backgrounds-3]</a> defines the following terms:
<ul>
<li><a href="http://dev.w3.org/csswg/css-backgrounds-3/#border-radius">border-radius</a>
</ul>
<li><a data-link-type="biblio" href="#biblio-css-conditional-3">[css-conditional-3]</a> defines the following terms:
<ul>
<li><a href="http://dev.w3.org/csswg/css-conditional-3/#at-ruledef-media">@media</a>
</ul>
<li><a data-link-type="biblio" href="#biblio-css-images-3">[css-images-3]</a> defines the following terms:
<ul>
<li><a href="http://dev.w3.org/csswg/css-images-3/#typedef-image">&lt;image></a>
</ul>
<li><a data-link-type="biblio" href="#biblio-css-shapes-2">[css-shapes-2]</a> defines the following terms:
<ul>
<li><a href="http://dev.w3.org/csswg/css-shapes-2/#typedef-basic-shape">&lt;basic-shape></a>
<li><a href="http://dev.w3.org/csswg/css-shapes-2/#typedef-uri">&lt;uri></a>
</ul>
<li><a data-link-type="biblio" href="#biblio-css-values-3">[css-values-3]</a> defines the following terms:
<ul>
<li><a href="http://dev.w3.org/csswg/css-values-3/#length-value">&lt;length></a>
<li><a href="http://dev.w3.org/csswg/css-values-3/#percentage-value">&lt;percentage></a>
<li><a href="http://dev.w3.org/csswg/css-values-3/#mult-opt">?</a>
<li><a href="http://dev.w3.org/csswg/css-values-3/#comb-one">|</a>
<li><a href="http://dev.w3.org/csswg/css-values-3/#comb-any">||</a>
</ul>
</ul>
<h2 class="no-num heading settled" id="references"><span class="content">References</span><a class="self-link" href="#references"></a></h2>
<h3 class="no-num heading settled" id="normative"><span class="content">Normative References</span><a class="self-link" href="#normative"></a></h3>
<dl>
<dt id="biblio-css21"><a class="self-link" href="#biblio-css21"></a>[CSS21]
<dd>Bert Bos; et al. <a href="http://www.w3.org/TR/2011/REC-CSS2-20110607">Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification</a>. 7 June 2011. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2011/REC-CSS2-20110607">http://www.w3.org/TR/2011/REC-CSS2-20110607</a>
<dt id="biblio-mediaq"><a class="self-link" href="#biblio-mediaq"></a>[MEDIAQ]
<dd>Florian Rivoal. <a href="http://www.w3.org/TR/2012/REC-css3-mediaqueries-20120619/">Media Queries</a>. 19 June 2012. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2012/REC-css3-mediaqueries-20120619/">http://www.w3.org/TR/2012/REC-css3-mediaqueries-20120619/</a>
<dt id="biblio-css-backgrounds-3"><a class="self-link" href="#biblio-css-backgrounds-3"></a>[CSS-BACKGROUNDS-3]
<dd>CSS Backgrounds and Borders Module Level 3 URL: <a href="http://www.w3.org/TR/css3-background/">http://www.w3.org/TR/css3-background/</a>
<dt id="biblio-css-conditional-3"><a class="self-link" href="#biblio-css-conditional-3"></a>[CSS-CONDITIONAL-3]
<dd>CSS Conditional Rules Module Level 3 URL: <a href="http://www.w3.org/TR/css3-conditional/">http://www.w3.org/TR/css3-conditional/</a>
<dt id="biblio-css-images-3"><a class="self-link" href="#biblio-css-images-3"></a>[CSS-IMAGES-3]
<dd>CSS Image Values and Replaced Content Module Level 3 URL: <a href="http://www.w3.org/TR/css3-images/">http://www.w3.org/TR/css3-images/</a>
<dt id="biblio-css-shapes-2"><a class="self-link" href="#biblio-css-shapes-2"></a>[CSS-SHAPES-2]
<dd>CSS Shapes Module Level 2 URL: <a href="http://dev.w3.org/csswg/css-shapes-2/">http://dev.w3.org/csswg/css-shapes-2/</a>
<dt id="biblio-css-values-3"><a class="self-link" href="#biblio-css-values-3"></a>[CSS-VALUES-3]
<dd>CSS Values and Units Module Level 3 URL: <a href="http://www.w3.org/TR/css3-values/">http://www.w3.org/TR/css3-values/</a>
<dt id="biblio-rfc2119"><a class="self-link" href="#biblio-rfc2119"></a>[RFC2119]
<dd>S. Bradner. <a href="https://tools.ietf.org/html/rfc2119">Key words for use in RFCs to Indicate Requirement Levels</a>. March 1997. Best Current Practice. URL: <a href="https://tools.ietf.org/html/rfc2119">https://tools.ietf.org/html/rfc2119</a>
</dl>
<h3 class="no-num heading settled" id="informative"><span class="content">Informative References</span><a class="self-link" href="#informative"></a></h3>
<dl>
<dt id="biblio-css-shapes"><a class="self-link" href="#biblio-css-shapes"></a>[CSS-SHAPES]
<dd>Vincent Hardy; Rossen Atanassov; Alan Stearns. <a href="http://www.w3.org/TR/2013/WD-css-shapes-1-20130620/">CSS Shapes Module Level 1</a>. 20 June 2013. W3C Working Draft. URL: <a href="http://www.w3.org/TR/2013/WD-css-shapes-1-20130620/">http://www.w3.org/TR/2013/WD-css-shapes-1-20130620/</a>
<dt id="biblio-css-shapes-1"><a class="self-link" href="#biblio-css-shapes-1"></a>[CSS-SHAPES-1]
<dd>Vincent Hardy; Rossen Atanassov; Alan Stearns. <a href="http://www.w3.org/TR/css-shapes-1/">CSS Shapes Module Level 1</a>. 20 March 2014. CR. URL: <a href="http://www.w3.org/TR/css-shapes-1/">http://www.w3.org/TR/css-shapes-1/</a>
<dt id="biblio-css3-border"><a class="self-link" href="#biblio-css3-border"></a>[CSS3-BORDER]
<dd>Tapas Roy. <a href="http://www.w3.org/TR/css3-border">CSS3 module: Border</a>. 7 November 2002. WD. URL: <a href="http://www.w3.org/TR/css3-border">http://www.w3.org/TR/css3-border</a>
<dt id="biblio-css3-positioning"><a class="self-link" href="#biblio-css3-positioning"></a>[CSS3-POSITIONING]
<dd>Rossen Atanassov; Arron Eicholz. <a href="http://www.w3.org/TR/css3-positioning/">CSS Positioned Layout Module Level 3</a>. 3 February 2015. WD. URL: <a href="http://www.w3.org/TR/css3-positioning/">http://www.w3.org/TR/css3-positioning/</a>
</dl>
<h2 class="no-num heading settled" id="property-index"><span class="content">Property Index</span><a class="self-link" href="#property-index"></a></h2>
<table class="proptable data">
<thead>
<tr>
<th scope="col">Name
<th scope="col">Value
<th scope="col">Initial
<th scope="col">Applies to
<th scope="col">Inh.
<th scope="col">%ages
<th scope="col">Media
<th scope="col">Animatable
<th scope="col">Computed value
<th scope="col">For
<tbody>
<tr>
<th scope="row"><a class="css" data-link-type="property" href="#propdef-shape-inside">shape-inside</a>
<td>auto | outside-shape | [ &lt;basic-shape> || shape-box ] | &lt;image> | display
<td>auto
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