drafts: css3-multicol/Overview.src.html@34298d3d5627 (annotated)

css3-multicol/Overview.src.html@34298d3d5627 (annotated)

css3-multicol/Overview.src.html

Thu, 07 Feb 2013 22:43:19 -0800

author: L. David Baron <dbaron@dbaron.org>
date: Thu, 07 Feb 2013 22:43:19 -0800
changeset 7398: 34298d3d5627
parent 6240: c685227b6e8a
permissions: -rw-r--r--

[css3-multicol] Add "Animatable:" lines to propdef tables.

This is as resolved in Tucson face-to-face at
2013-02-04 11:40:47 -0700, and edited by me per discussion starting at
2013-02-05 11:11:38 -0700.

 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
 <html lang="en">
 <head>
 <title>CSS Multi-column Layout Module</title>
 <link rel="stylesheet" type="text/css" href="../default.css">
 <link href="http://www.w3.org/StyleSheets/TR/W3C-[STATUS].css" rel=stylesheet type="text/css">
 <style type="text/css">
 .cols { width: 500px; height: 200px; background: #fff; position: relative; border: solid 5px blue; margin: 0.5em 2em 1em 0; font: bold 14px/19px Arial, sans-serif }
 .cols p { padding: 3px; margin: 0 }
 .col { position: absolute; left: 0px; top: 0; z-index: 6; width: 170px }
 .gap { position: absolute; background: green; width: 5px; bottom: 0px; top: 0px; border: 10px solid yellow; border-top-width: 0; border-bottom-width: 0;  }
 .rep { position: absolute; top: 45px; background: black; height: 110px; width: 100px;  color: white; z-index: 4 }
 table.breaks { border-collapse: collapse; margin: 1em 0 }
 table.breaks td, table.breaks th { border: thin solid black; padding: 0.1em 0.2em }
 div.example:before { width: 9em }
 </style>
 </head>
 <body>
 <div class="head">
 <!--logo-->
 <h1>CSS Multi-column Layout Module</h1>
 <h2 class="no-num no-toc" id="w3c-working">[LONGSTATUS] [DATE]</h2>
 <dl>
 <dt>This version:</dt>
 <dd>
 <!--<a href="http://www.w3.org/TR/[YEAR]/CR-[SHORTNAME]-[CDATE]">[VERSION]</a>-->
 <a href="http://dev.w3.org/csswg/css3-multicol/">http://dev.w3.org/csswg/css3-multicol/</a>
 <dt>Latest version:
 <dd><a href="http://www.w3.org/TR/css3-multicol">
 http://www.w3.org/TR/css3-multicol</a>
 <dt>Previous version:
 <dd><a href="http://www.w3.org/TR/2009/CR-css3-multicol-20091217/">http://www.w3.org/TR/2009/CR-css3-multicol-20091217/</a>
 <dt>Editors:
 <dd>H&aring;kon Wium Lie, Opera Software, howcome@opera.com
 </dl>
 <!--begin-copyright-->
 <p>[If you keep the &lt;!--comment-->, the copyright will be included
 here automatically]</p>
 <!--end-copyright-->
 <hr title="Separator for header">
 </div>
 <h2 class="no-num no-toc" id=abstract>Abstract</h2>
 <p>This specification describes multi-column layouts in CSS, a style
 sheet language for the web. Using functionality described in the
 specification, content can be flowed into multiple columns with a gap
 and a rule between them.
 <h2 class="no-num no-toc">Status of this document</h2>
 <!--begin-status-->
 <p>[If you keep the &lt;!--comment-->, the status boilerplate will be
 included here automatically.]</p>
 <!--end-status-->
 <p>This document has been a Working Draft in the CSS Working Group for
 several years. Multi-column layouts are traditionally used in print.
 On screen, multi-column layouts have been considered experimental, and
 implementation and use experience was deemed necessary in order to
 proceed. Several implementations have occurred over the past years, and
 this specification incorporates useful feedback from implementors as well as
 authors and users.
 <p>The specification was updated in April 2011 to correct a
 contradiction between the text and the pseudo-algorithm in
 section&nbsp;3.4. The pseudo-algorithm was corrected and also made
 easier to read. The wording of a few other sections was improved in
 places, without changes to the functionality. In January, 2012, some
 examples and the description of the 'column-fill' property was
 revised.
 <p>This document will remain Candidate Recommendation at least until
 May 2011. See the <a href="#cr-exit-criteria">CR exit
 criteria.</a>
 <h2 class="no-num no-toc"><a name="contents">Table of contents</a></h2>
 <!--begin-toc-->
 <p>[If you keep the &lt;!--comment--> the table of contents will be
 included here automatically.]</p>
 <!--end-toc-->
 <h2>Introduction</h2>
 <p>(This section is not normative.)
 <p>This module describes multi-column layout in CSS. By using
 functionality described in this document, style sheets can declare
 that the content of an element is to be laid out in multiple
 columns.
 <p>On the Web, tables have also been used to describe multi-column
 layouts. The main benefit of using CSS-based columns is flexibility;
 content can flow from one column to another, and the number of columns
 can vary depending on the size of the viewport. Removing presentation
 table markup from documents allows them to more easily be presented on
 various output devices including speech synthesizers and small mobile
 devices.
 <p>Multi-column layouts are easy to describe in CSS. Here is a simple example:
 <div class=example>
 <pre>body { column-width: 12em }</pre>
 <p>In this example, the <code class=html>body</code> element is
 set to have columns at least ''12em'' wide. The exact number of
 columns will depend on the available space.
 </div>
 <p>The number of columns can also be set explicitly in the style sheet:
 <div class=example>
 <pre>body { column-count: 2 }</pre>
 <p>In this case, the number of columns is fixed and the column widths
 will vary depending on the available width.
 </div>
 <p>The shorthand 'columns' property can be used to set either,
 or both, properties in one declaration.
 <div class=example>
 <p>In these examples, the number of columns, the width of columns, and
 both the number and width are set, respectively:
 <pre>
 body { columns: 2 }
 body { columns: 12em }
 body { columns: 2 12em }
 </pre>
 <p>However, as described below, setting both the width and number of
 columns rarely makes sense.
 </div>
 <p>Another group of properties introduced in this module describe
 gaps and rules between columns.
 <div class=example>
 <pre>
 body {
   column-gap: 1em;
   column-rule: thin solid black;
 }
 </pre>
 <p>The first declaration in the example above sets the gap between two
 adjacent columns to be 1em. Column gaps are similar to padding areas.
 In the middle of the gap there will be a rule which is described by
 the 'column-rule' property.
 </div>
 <p>The values of the 'column-rule' property are similar to those of
 the CSS border properties. Like 'border', 'column-rule' is a
 shorthand property.
 <div class=example>
 <p>In this example, the shorthand 'column-rule' declaration from the
 above example has been expanded:
 <pre>
 body {
   column-gap: 1em;
   column-rule-width: thin;
   column-rule-style: solid;
   column-rule-color: black;
 }
 </pre>
 </div>
 <p>The 'column-fill' and 'column-span' properties give style sheets a
 wider range of visual expressions in multi-column layouts.
 <div class=example>
 <p>In this example, columns are set to be balanced, i.e., to have
 approximately the same length. Also, <code>h2</code> elements are set
 to span across all columns.
 <pre>
 div { column-fill: balance }
 h2 { column-span: all }
 </pre>
 </div>
 <p>This specification introduces ten new properties, all of which
 are used in the examples above.
 <p>To indicate where column breaks should (or should not) appear, new
 keyword values are introduced.
 <div class=example>
 <p>In this example, <code>h1</code> elements will always have a column
 break before them, but the formatter will try to avoid column breaks
 inside and after the element.
 <pre>
 h1 {
   break-before: column;
   break-inside: avoid-column;
   break-after: avoid-column;
 }
 </pre>
 <!--<p>The properties and values used in this example are formally defined in [!CSS3PAGE]].-->
 </div>
 <p>If all column properties have their initial value, the layout of
 an element will be identical to a multi-column layout with only one
 column.
 <h2>The multi-column model</h2>
 <p>A <dfn>multi-column element</dfn> (or <em>multicol element</em>
 for short) is an element whose 'column-width' or 'column-count'
 property is not ''auto'' and therefore acts as a container for
 multi-column layout.
 <p>In the traditional CSS box model, the content of an element is
 flowed into the content box of the corresponding element. Multi-column
 layout introduces a new type of container between the content box and
 the content, namely the <dfn>column box</dfn> (or <em>column</em> for
 short). The content of a multicol element is flowed into its column
 boxes.
 <p>Column boxes in a multi-column element are arranged
 into <em>rows</em>. Like table cells, the column boxes in a row are
 ordered in the inline direction of the multicol element. The
 <em>column width</em> is the length of the column box in the inline
 direction. The <em>column height</em> is the length of the column box
 in the block direction. All column boxes in a row have the same column width, and all
 column boxes in a row have the same column height. Within each row in the multi-column element,
 adjacent column boxes are separated by a <em>column gap</em>, which
 may contain a <em>column rule</em>. All column gaps in the same row
 are equal. All column rules in the same row are also equal, if they
 appear; column rules only appear between columns that both have
 content.
 <p>In the simplest case a multicol element will contain only one row
 of columns, and the height of each column will be equivalent to the
 used height of the multi-column element's content box. If the
 multi-column element is paginated, the height of each row is
 constrained by the page and the content continues in a new row of
 column boxes on the next page; a column box never splits across pages.
 The same effect occurs when a <em>spanning element</em> divides the
 multi-column element: the columns before the spanning element are
 balanced and shortened to fit their content. Content after the
 spanning element then flows into a new row of column boxes.
 <p>It is not possible to set properties/values on column boxes. For
 example, the background of a certain column box cannot be set and a
 column box has no concept of padding, margin or borders.
 <p class="note">Future specifications may add additional
 functionality. For example, columns of different widths and different
 backgrounds may be supported.</p>
 <div class="example">
 <p>Column gaps (yellow) and column rules (green) are shown in this
 sample rendition of a multi-column element with padding (blue). The
 blue and yellow is present for illustrational purposes only. In actual
 implementations these areas will be determined by the background.
 <div class=cols>
 <div class="col" style="">
 <p>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs
 </div>
 <div class="col" style="left: 175px">
 <p>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 </div>
 <div class="col" style="left: 350px">
 <p>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 Pqr stu vw xyz.
 </div>
 <div class=gap style="left: 150px"></div>
 <div class=gap style="left: 325px"></div>
 </div>
 <p>To illustrate the effects of the various properties described in
 this specification, variations on a sample document will be used. Here
 is the source code of the sample document:
 <pre class="html">
 &lt;html>
 &lt;style type="text/css">
 div {
   column-width: 15em;
   column-gap: 2em;   /* shown in yellow */
   column-rule: 4px solid green;
   padding: 5px;      /* shown in blue */
 }
 p { margin: 0; padding: 0 }
 img { display: none }
 &lt;/style>
 &lt;body>
 &lt;div>
 &lt;p&gt;Ab cde fgh i jkl. Mno
 pqr stu vw xyz. A bc
 &lt;img src=...>
 def g hij
 ...
 &lt;/div>
 &lt;/body>
 &lt;/html>
 </pre>
 <p>The nonsensical text in the example is the English alphabet which
 shows how text flows from one column to another. To simplify the
 visualization, the textual content of the different examples vary
 slightly.
 </div>
 <p>Column boxes are block container boxes. That
 is, column boxes behave like block-level, table cell, and inline-block
 boxes as per CSS 2.1, section 10.1, item 2 [[!CSS21]]. However, column
 boxes do not establish block container boxes for elements with ''position:
 fixed'' or ''position: absolute''.
 <div class=example>
 <p>In this example, the width of the image is set with these rules:
 <pre class=css>
 img { display: block; width: 100% }
 </pre>
 <p>Given that the width is calculated relative to the column box, the
 image will be as wide as the column box:
 <div class=cols>
 <p>Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 <br><br><br><br><br><br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 <div class="col" style="left: 175px">
 <p>hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 </div>
 <div class="col" style="left: 350px">
 <p>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz.
 </div>
 <div class=rep style="width: 150px"></div>
 <div class=gap style="left: 150px"></div>
 <div class=gap style="left: 325px"></div>
 </div>
 </div>
 <p>Floats that appear inside multi-column layouts are positioned with
 regard to the column box where the float appears.
 <div class="example">
 <p>In this example, this CSS fragment describes the presentation of the image:
 <pre class="css">
 img { display: block; float: right }
 </pre>
 <div class=cols>
 <div class="col" style="">
 <p>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g<br>
 hij klm<br>
 nopq<br>
 rs tuv<br>
 wxy x<br>
 yz. Ab <br>
 cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc
 </div>
 <div class="col" style="left: 175px">
 <p>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 </div>
 <div class="col" style="left: 350px">
 <p>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 </div>
 <div class=rep style="left: 50px"></div>
 <div class=gap style="left: 150px"></div>
 <div class=gap style="left: 325px"></div>
 </div>
 <p>The black box represents the image.
 </div>
 <p>A multi-column element establishes a new block formatting context,
 as per CSS 2.1 section 9.4.1.
 <div class="example">
 <p>A top margin set on the first child element of a multicol element will not collapse with the margins of the multicol element.
 </div>
 <p>Nested multi-column elements are allowed, but there may be
 implementation-specific limits.
 <h2>The number and width of columns</h2>
 <p>Finding the number and width of columns is fundamental when
 laying out multi-column content. When the block direction
 is unconstrained and no column breaks are added through style sheets,
 these two properties determine the outcome:
 <ul>
 <li>'column-count'
 <li>'column-width'
 </ul>
 <p>A third property, 'columns', is a shorthand property which sets both
 'column-width' and 'column-count'.
 <h3 id='cw'>'column-width'</h3>
 <table class=propdef>
     <tr>
       <td><em>Name:</em>
       <td><dfn>column-width</dfn>
     <tr>
       <td><em>Value:</em>
       <td>&lt;length&gt; | auto
     <tr>
       <td><em>Initial:</em>
       <td>auto
     <tr>
       <td><em>Applies to:</em>
       <td>non-replaced block-level elements (except table elements), table cells, and inline-block elements
     <tr>
       <td><em>Inherited:</em>
       <td>no
     <tr>
       <td><em>Percentages:</em>
       <td>N/A
     <tr>
       <td><em>Media:</em>
       <td>visual
     <tr>
       <td><em>Computed&nbsp;value:</em>
       <td>the absolute length, zero or larger
     <tr>
       <td><em>Animatable:</em>
       <td>as <a href="http://dev.w3.org/csswg/css3-transitions/#animtype-length">length</a>
 </table>
 <p>This property describes the width of columns in multicol elements.
 <dl>
 <dt>auto
 <dd>means that the column width will be determined by other properties
 (e.g., 'column-count', if it has a non-auto value).
 <dt>&lt;length>
 <dd>describes the optimal column width. The actual column width may be
 wider (to fill the available space), or narrower (only if the
 available space is smaller than the specified column width). Specified values
 must be greater than 0.
 </dl>
 <div class=example>
 <p>For example, consider this style sheet:</p>
 <pre>
 div {
   width: 100px;
   column-width: 45px;
   column-gap: 0;
   column-rule: none;
 }
 </pre>
 <p>There is room for two 45px wide columns inside the 100px wide element. In
 order to fill the available space the actual column width will be
 increased to 50px.</p>
 </div>
 <div class=example>
 <p>Also, consider this style sheet:</p>
 <pre>
 div {
   width: 40px;
   column-width: 45px;
   column-gap: 0;
   column-rule: none;
 }
 </pre>
 <p>The available space is smaller than the specified column width and
 the actual column width will therefore be decreased.</p>
 </div>
 <p>To ensure that 'column-width' can be used with vertical text,
 column width means the length of the line boxes inside the columns.
 <p class=note>The reason for making 'column-width' somewhat flexible
 is to achieve scalable designs that can fit many screen sizes. To set
 an exact column width, all length values (in horizontal text these
 are: 'width', 'column-width', 'column-gap', and 'column-rule-width')
 must be specified.</p>
 <h3 id='cc'>'column-count'</h3>
 <table class=propdef>
     <tr>
       <td><em>Name:</em>
       <td><dfn>column-count</dfn>
     <tr>
       <td><em>Value:</em>
       <td>&lt;integer&gt; | auto
     <tr>
       <td><em>Initial:</em>
       <td>auto
     <tr>
       <td><em>Applies to:</em>
       <td>non-replaced block-level elements (except table elements), table cells, and inline-block elements
     <tr>
       <td><em>Inherited:</em>
       <td>no
     <tr>
       <td><em>Percentages:</em>
       <td>N/A
     <tr>
       <td><em>Media:</em>
       <td>visual
     <tr>
       <td><em>Computed&nbsp;value:</em>
       <td>specified value
     <tr>
       <td><em>Animatable:</em>
       <td>as <a href="http://dev.w3.org/csswg/css3-transitions/#animtype-integer">integer</a>
 </table>
 <p>This property describes the number of columns of a multicol element.
 <dl>
 <dt>auto
 <dd>means that the number of columns will be determined by other properties
 (e.g., 'column-width', if it has a non-auto value).
 <dt>&lt;integer>
 <dd>describes the optimal number of columns into which the content of
 the element will be flowed. Values must be greater than 0. If both
 'column-width' and 'column-count' have non-auto values, the integer
 value describes the maximum number of columns.
 </dl>
 <div class=example>
 <p>Example:</p>
 <pre>body { column-count: 3 }</pre>
 </div>
 <h3>'columns'</h3>
 <table class=propdef>
     <tr>
       <td><em>Name:</em>
       <td><dfn>columns</dfn>
     <tr>
       <td><em>Value:</em>
       <td><a href='#cw'>&lt;'column-width'></a> || <a href='#cc'>&lt;'column-count'></a>
     <tr>
       <td><em>Initial:</em>
       <td>see individual properties
     <tr>
       <td><em>Applies to:</em>
       <td>non-replaced block-level elements (except table elements), table cells, and inline-block elements
     <tr>
       <td><em>Inherited:</em>
       <td>no
     <tr>
       <td><em>Percentages:</em>
       <td>N/A
     <tr>
       <td><em>Media:</em>
       <td>visual
     <tr>
       <td><em>Computed&nbsp;value:</em>
       <td>see individual properties
     <tr>
       <td><em>Animatable:</em>
       <td>see individual properties
 </table>
 <p>This is a shorthand property for setting 'column-width' and
 'column-count'. Omitted values are set to their initial values.
 <div class="example">
 <p>Here are some valid declarations using the 'columns' property:
 <pre>
 columns: 12em;      /* column-width: 12em; column-count: auto */
 columns: auto 12em; /* column-width: 12em; column-count: auto */
 columns: 2;         /* column-width: auto; column-count: 2 */
 columns: 2 auto;    /* column-width: auto; column-count: 2 */
 columns: auto;      /* column-width: auto; column-count: auto */
 columns: auto auto; /* column-width: auto; column-count: auto */
 </pre>
 </div>
 <h3>Pseudo-algorithm</h3>
 <P>The pseudo-algorithm below determines the used values for
 'column-count' (N) and 'column-width' (W). There are two other
 variables in the pseudo-algorithm:
 <ul>
 <li><code>available-width</code>: if the used width of the
 multi-column element has not been determined when the 'column-count'
 and 'column-width' must be determined (e.g., if it is floating with a
 'width' of 'auto' as per CSS 2.1 section 10.3.5) this variable is
 <code>unknown</code>, otherwise it is the same as the used width of
 the multi-column element. In vertical text, the used height replaces used width in this calculation.
 <li><code>shrink-to-fit</code>: this variable represents the result of
 a <em>shrink-to-fit</em> computation. CSS does not define the exact
 algorithm.
 </ul>
 <p>Two assumptions are being made by the pseudo-algorithm:
 <ul>
 <li>that the block direction is unconstrained
 <li>that no column breaks are added through style sheets
 </ul>
 <p>The <code>floor()</code> function rounds a number to the next smaller integer.
 <!--
 <pre>
 (01)  if ((column-width = auto) and (column-count = auto)) or
 (02)     ((available-width = unknown) and (column-count = auto)) then
 (03)    exit; /* no columns */
 (04)  fi
 (05)
 (06)  if (available-width = unknown) and (column-count != auto) and (column-width != auto) then
 (07)    N := column-count;
 (08)    W := column-width;
 (09)    exit;
 (10)  fi
 (11)
 (12)  if (available-width = unknown) then
 (13)    available-width := shrink-to-fit;
 (14)  fi
 (15)
 (16)  if (column-width = auto) then
 (18)    N := column-count;
 (19)    W := max(0, (available-width - ((N - 1) * column-gap))/N);
 (27)  elsif (column-count = auto) then
 (28)    if (column-width >= available-width) then
 (29)      N := 1
 (30)      W := available-width;
 (31)    else
 (32)      N := floor((available-width + column-gap) / (column-width + column-gap));
 (33)      W := ((available-width + column-gap) / N) - column-gap;
 (34)    fi
 (35)  elsif (column-width >= available-width) then
 (36)    N := 1
 (37)    W := available-width;
 (38)  else
 (39)    N := min(column-count, floor((available-width + column-gap) / (column-width + column-gap)))
 (40)    W := ((available-width + column-gap) / N) - column-gap;
 (41)  fi
 </pre>
 <p><span class=issue>Alternative encoding of pseudo-algorithm:
 -->
 <pre>
 (01)  if ((column-width = auto) and (column-count = auto)) then
 (02)        exit; /* not a multicol element */
 (03)  if ((available-width = unknown) and (column-count = auto)) then
 (04)    exit; /* no columns */
 (05)  if (available-width = unknown) and (column-count != auto) and (column-width != auto) then
 (06)    N := column-count;
 (07)    W := column-width;
 (08)  exit;
 (09)  if (available-width = unknown) then
 (10)    available-width := shrink-to-fit;
 (11)  if (column-width = auto) and (column-count != auto) then
 (12)    N := column-count;
 (13)    W := max(0, (available-width - ((N - 1) * column-gap)) / N);
 (14)  exit;
 (15)  if (column-width != auto) and (column-count = auto) then
 (16)    N := max(1, floor((available-width + column-gap) / (column-width + column-gap)));
 (17)    W := ((available-width + column-gap) / N) - column-gap;
 (18)  exit;
 (19)  if (column-width != auto) and (column-count != auto) then
 (20)    N := min(column-count, floor((available-width + column-gap) / (column-width + column-gap)))
 (21)    N := max(1, N);
 (22)    W := ((available-width + column-gap) / N) - column-gap;
 (23)  exit
 </pre>
 <p>In paged media, user agents may perform this calculation on a
 per-page basis.
 <p class=note>Note that, in most cases, only one of 'column-width' and
 'column-count' affect the layout. If 'column-width' has a value other
 than ''auto'', 'column-count' indicates the maximum number of columns.
 However, both 'column-width' and 'column-count' are honored when the
 width of the element has not been determined. This can, e.g., be the
 case for table cells and floats.
 <h3>Stacking context</h3>
 <p>All column boxes in a multi-column element are in the same stacking
 context and the drawing order of their contents is as specified in
 CSS 2.1. Column boxes do not establish new stacking contexts.
 <h2>Column gaps and rules</h2>
 <p>Column gaps and rules are placed between columns in the same
 multicol element. The length of the column gaps and column rules
 is equal to the length of the columns. Column gaps take up space. That
 is, column gaps will push apart content in adjacent columns (within
 the same multicol element).
 <p>A column rule is drawn in the middle of the column gap with the
 endpoints at opposing content edges of the multicol element. Column
 rules do not take up space. That is, the presence or thickness of a
 column rule will not alter the placement of anything else. If a column
 rule is wider than its gap, the adjacent column boxes will overlap the
 rule, and the rule may possibly extend outside the box of the multicol
 element. Column rules are painted just above the background of the
 multicol element. Column rules are only drawn between two columns that
 both have content.
 <h3>'column-gap'</h3>
 <table class=propdef>
     <tr>
       <td><em>Name:</em>
       <td><dfn>column-gap</dfn>
     <tr>
       <td><em>Value:</em>
       <td>&lt;length&gt; | normal
     <tr>
       <td><em>Initial:</em>
       <td>normal
     <tr>
       <td><em>Applies to:</em>
       <td>multicol elements
     <tr>
       <td><em>Inherited:</em>
       <td>no
     <tr>
       <td><em>Percentages:</em>
       <td>N/A
     <tr>
       <td><em>Media:</em>
       <td>visual
     <tr>
       <td><em>Computed&nbsp;value:</em>
       <td>absolute length or 'normal'
     <tr>
       <td><em>Animatable:</em>
       <td>as <a href="http://dev.w3.org/csswg/css3-transitions/#animtype-length">length</a>
 </table>
 <p>The 'column-gap' property sets the gap between columns. If there is
 a column rule between columns, it will appear in the middle of the
 gap.
 <p>The ''normal'' value is UA-specific. A value of ''1em'' is suggested.
 <p>Column gaps cannot be negative.
 <h3 id='crc'>'column-rule-color'</h3>
 <table class=propdef>
     <tr>
       <td><em>Name:</em>
       <td><dfn>column-rule-color</dfn>
     <tr>
       <td><em>Value:</em>
       <td>&lt;color&gt;
     <tr>
       <td><em>Initial:</em>
       <td><a href="http://www.w3.org/TR/css3-color/#currentcolor">currentColor</a>
 <!--      <td>same as for 'color' property [[!CSS21]]-->
     <tr>
       <td><em>Applies to:</em>
       <td>multicol elements
     <tr>
       <td><em>Inherited:</em>
       <td>no
     <tr>
       <td><em>Percentages:</em>
       <td>N/A
     <tr>
       <td><em>Media:</em>
       <td>visual
     <tr>
       <td><em>Computed&nbsp;value:</em>
       <td>the same as the computed value for the 'color' property [[!CSS21]]
     <tr>
       <td><em>Animatable:</em>
       <td>as <a href="http://dev.w3.org/csswg/css3-transitions/#animtype-color">color</a>
 </table>
 <p>This property sets the color of the column rule. The &lt;color&gt;
 values are defined in [[!CSS21]].
 <h3 id='crs'>'column-rule-style'</h3>
 <table class=propdef>
     <tr>
       <td><em>Name:</em>
       <td><dfn>column-rule-style</dfn>
     <tr>
       <td><em>Value:</em>
       <td><a href="http://www.w3.org/TR/CSS2/tables.html#table-border-styles">&lt;border-style&gt;</a>
 <!--http://www.w3.org/TR/CSS21/box.html#value-def-border-style-->
     <tr>
       <td><em>Initial:</em>
       <td>none
     <tr>
       <td><em>Applies to:</em>
       <td>multicol elements
     <tr>
       <td><em>Inherited:</em>
       <td>no
     <tr>
       <td><em>Percentages:</em>
       <td>N/A
     <tr>
       <td><em>Media:</em>
       <td>visual
     <tr>
       <td><em>Computed&nbsp;value:</em>
       <td>specified value
     <tr>
       <td><em>Animatable:</em>
       <td>no
 </table>
 <p>The 'column-rule-style' property sets the style of the rule between columns of an element. The &lt;border-style&gt; values are defined in [[!CSS21]] and the values are interpreted as in the <a href="http://www.w3.org/TR/CSS2/tables.html#collapsing-borders">the collapsing border model</a>.
 <p>The 'none' value forces the computed value of <span class="property">'column-rule-width'</span> to be '0'.
 <h3 id='crw'>'column-rule-width'</h3>
 <table class=propdef>
     <tr>
       <td><em>Name:</em>
       <td><dfn>column-rule-width</dfn>
     <tr>
       <td><em>Value:</em>
       <td><a href="http://www.w3.org/TR/CSS21/box.html#value-def-border-width">&lt;border-width&gt;</a>
     <tr>
       <td><em>Initial:</em>
       <td>medium
     <tr>
       <td><em>Applies to:</em>
       <td>multicol elements
     <tr>
       <td><em>Inherited:</em>
       <td>no
     <tr>
       <td><em>Percentages:</em>
       <td>N/A
     <tr>
       <td><em>Media:</em>
       <td>visual
     <tr>
       <td><em>Computed&nbsp;value:</em>
       <td>absolute length; '0' if the column rule style is 'none' or 'hidden'
     <tr>
       <td><em>Animatable:</em>
       <td>as <a href="http://dev.w3.org/csswg/css3-transitions/#animtype-length">length</a>
 </table>
 <p>This property sets the width of the rule between columns. Negative values are not allowed.
 <h3>'column-rule'</h3>
 <table class=propdef>
     <tr>
       <td><em>Name:</em>
       <td><dfn>column-rule</dfn>
     <tr>
       <td><em>Value:</em>
       <td><a href='#crw'>&lt;'column-rule-width'&gt;</a> || <a href='#crs'>&lt;'column-rule-style'&gt;</a> || [ <a href='#crc'>&lt;'column-rule-color'&gt;</a> | transparent ]
     <tr>
       <td><em>Initial:</em>
       <td>see individual properties
     <tr>
       <td><em>Applies to:</em>
       <td>multicol elements
     <tr>
       <td><em>Inherited:</em>
       <td>no
     <tr>
       <td><em>Percentages:</em>
       <td>N/A
     <tr>
       <td><em>Media:</em>
       <td>visual
     <tr>
       <td><em>Computed&nbsp;value:</em>
       <td>see individual properties
     <tr>
       <td><em>Animatable:</em>
       <td>see individual properties
 </table>
 <p>This property is a shorthand for setting
 'column-rule-width', 'column-rule-style', and 'column-rule-color' at
 the same place in the style sheet. Omitted values are set to their
 initial values.
 <div class=example>
 <p>In this example, the column rule and the column gap have the same
 width. Therefore, they will occupy exactly the same space.
 <pre>
 body {
   column-gap: 1em;
   column-rule-width: 1em;
   column-rule-style: solid;
   column-rule-color: black;
 }
 </pre>
 </div>
 <div class=example>
 <p>If a tall image is moved to a column on the next page to find room
 for it, its natural column may be left empty. If so, the column is is
 still considered to have content for the purpose of deciding if the
 column rule should be drawn.
 </div>
 <h2>Column breaks</h2>
 <p>When content is laid out in multiple columns, the user agent must
 determine where column breaks are placed. The problem of breaking
 content into columns is similar to breaking content into pages, which
 is described in CSS 2.1, section 13.3.3 [[!CSS21]].
 <p>Three new properties are introduced to allow column breaks to be
 described in the same properties as page breaks: 'break-before',
 'break-after', and 'break-inside'. These properties take the same
 values as 'page-break-before', 'page-break-after', and
 'page-break-inside'  [[!CSS21]]. In addition, some new keyword values
 are added.
 <h3>'break-before', 'break-after', 'break-inside'</h3>
 <table class=propdef>
     <tr>
       <td><em>Name:</em>
       <td><dfn>break-before</dfn>
     <tr>
       <td><em>Value:</em>
       <td>auto | always | avoid | left | right | page | column | avoid-page | avoid-column
     <tr>
       <td><em>Initial:</em>
       <td>auto
     <tr>
       <td><em>Applies to:</em>
       <td>block-level elements
     <tr>
       <td><em>Inherited:</em>
       <td>no
     <tr>
       <td><em>Percentages:</em>
       <td>N/A
     <tr>
       <td><em>Media:</em>
       <td>paged
     <tr>
       <td><em>Computed&nbsp;value:</em>
       <td>specified value
     <tr>
       <td><em>Animatable:</em>
       <td>no
 </table>
 <table class=propdef>
     <tr>
       <td><em>Name:</em>
       <td><dfn>break-after</dfn>
     <tr>
       <td><em>Value:</em>
       <td>auto | always | avoid | left | right | page | column | avoid-page | avoid-column
     <tr>
       <td><em>Initial:</em>
       <td>auto
     <tr>
       <td><em>Applies to:</em>
       <td>block-level elements
     <tr>
       <td><em>Inherited:</em>
       <td>no
     <tr>
       <td><em>Percentages:</em>
       <td>N/A
     <tr>
       <td><em>Media:</em>
       <td>paged
     <tr>
       <td><em>Computed&nbsp;value:</em>
       <td>specified value
     <tr>
       <td><em>Animatable:</em>
       <td>no
 </table>
 <table class=propdef>
     <tr>
       <td><em>Name:</em>
       <td><dfn>break-inside</dfn>
     <tr>
       <td><em>Value:</em>
       <td>auto | avoid | avoid-page | avoid-column
     <tr>
       <td><em>Initial:</em>
       <td>auto
     <tr>
       <td><em>Applies to:</em>
       <td>block-level elements
     <tr>
       <td><em>Inherited:</em>
       <td>no
     <tr>
       <td><em>Percentages:</em>
       <td>N/A
     <tr>
       <td><em>Media:</em>
       <td>paged
     <tr>
       <td><em>Computed&nbsp;value:</em>
       <td>specified value
     <tr>
       <td><em>Animatable:</em>
       <td>no
 </table>
 <p>These properties describe page/column break behavior before/after/inside the generated box. These values are normatively defined in [[!CSS21]]:
 <dl>
 <dt>auto
 <dd>Neither force nor forbid a page/column break before (after, inside) the generated box.
 <dt>always
 <dd>Always force a page break before (after) the generated box.
 <dt>avoid
 <dd>Avoid a page/column break before (after, inside) the generated box.
 <dt>left
 <dd>Force one or two page breaks before (after) the generated box so that the next page is formatted as a left page.
 <dt>right
 <dd>Force one or two page breaks before (after) the generated box so that the next page is formatted as a right page.
 </dl>
 <p>This specification adds the following new values:
 <dl>
 <dt>page
   <dd>Always force a page break before (after) the generated box.
 <dt>column
   <dd>Always force a column break before (after) the generated box.
 <dt>avoid-page
   <dd>Avoid a page break before (after, inside) the generated box.
 <dt>avoid-column
   <dd>Avoid a column break before (after, inside) the generated box.
 </dl>
 <p>When a page or column break splits a box, the box's margins,
 borders, and padding have no visual effect where the split occurs.
 However, the margin immediately after a forced page/column break will
 be preserved. A forced page/column break is a break that does not occur
 naturally.
 <p class=note>In the future, new properties may describe alternate
 ways to handle margins, borders and padding around page/column breaks.
 <div class="example">
 <p>In this example, forced column breaks appear before <code>h2</code>
 elements and after <code>img</code> elements:
 <pre>
 .multicol { column-width: 8em }
 .multicol h2 { break-before: column; margin-top: 2em }
 .multicol img { break-after: column }
 </pre>
 <p>The top margin of <code>h2</code> elements will be preserved since the column break is forced.
 </div>
 <div class="example">
 <p>In this example, the formatter will try avoid column breaks inside <code>p</code> elements:
 <pre>
 p { break-inside: avoid-column }
 </pre>
 </div>
 <h2>Spanning columns</h2>
 <p>The 'column-span' property makes it possible for an element to span
 across several columns.
 <h3>'column-span'</h3>
 <table class=propdef>
     <tr>
       <td><em>Name:</em>
       <td><dfn>column-span</dfn>
     <tr>
       <td><em>Value:</em>
       <td>none | all
     <tr>
       <td><em>Initial:</em>
       <td>none
     <tr>
       <td><em>Applies to:</em>
       <td>in-flow block-level elements
     <tr>
       <td><em>Inherited:</em>
       <td>no
     <tr>
       <td><em>Percentages:</em>
       <td>N/A
     <tr>
       <td><em>Media:</em>
       <td>visual
     <tr>
       <td><em>Computed&nbsp;value:</em>
       <td>specified value
     <tr>
       <td><em>Animatable:</em>
       <td>no
 </table>
 <p>This property describes how many columns an element spans across. Values are:
 <dl>
 <dt>none
 <dd>The element does not span multiple columns.
 <dt>all
 <dd>The element spans across all columns of the nearest multicol
 ancestor in the same block formatting context. The element spans
 across all columns. Content in the normal flow that appears before the
 element is automatically balanced across all columns before the
 element appears. The element establishes a new block formatting
 context.
 </dl>
 <p>An element that spans more than one column is called a
 <dfn>spanning element</dfn> and the box it creates is called a <dfn>spanner</dfn>.
 <!--
 <p>This property has no effect on elements that do not fit entirely
 within the multicol element. Also, if a setting on this property pushes the
 element outside a multicol element, this property will have no effect.
 -->
 <div class="example">
 <p>In this example, an <code>h2</code> element has been added to the
 sample document after the sixth sentence (i.e., after the word "jkl."). This styling applies:
 <pre class="css">
 h2 { column-span: all; background: silver }
 img { display: none }
 </pre>
 <p>By setting 'column-span' to ''all'', all content that appear before
 the <code>h2</code> element is shown before the <code>h2</code>
 element.
 <div class=cols>
 <p>Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 <br><br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 <div class="col" style="left: 175px">
 <p>def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 <br><br>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 </div>
 <div class="col" style="left: 350px">
 <p>
 hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 <br><br>
 hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz.
 </div>
 <div class=rep style="width: 490px; height: 20px; background: silver; font-size: 1.5em; padding: 5px">An H2 element</div>
 <div class=gap style="left: 150px"></div>
 <div class=gap style="left: 325px"></div>
 </div>
 </div>
 <p>A spanning element takes up more space than the element would take
 up otherwise. When space is limited, it may be impossible to find room
 for the spanning element. In these cases, user agents may treat the
 element as if 'none' had been specified on this property.
 <div class="example">
 <p>In this example, the
 H2 element appears later in the content, and the height of the
 multicol element is constrained. Therefore, the H2 element appears in
 the overflow and there is not room to make the element spanning.
 As a result, the element appears as if 'column-span: none' was
 specified.
 <div class=cols style="height: 100px">
 <div class="col" style="">
 <p>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 </div>
 <div class="col" style="left: 175px">
 <p>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs
 </div>
 <div class="col" style="left: 350px">
 <p>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 </div>
 <div class="col" style="left: 525px">
 <p>pqr stu vw xyz.
 <div class=rep style="width: 140px; height: 40px; background: silver; font-size: 1.5em; padding: 5px; margin: 0; position: static">An H2 element</div>
 A bc def g hij klm
 </div>
 <div class="col" style="left: 700px">
 nopqrs tuv wxy z.
 </div>
 <div class=gap style="left: 150px"></div>
 <div class=gap style="left: 325px"></div>
 <div class=gap style="left: 500px"></div>
 <div class=gap style="left: 675px"></div>
 </div>
 </div>
 <div class="example">
 <p>This example is similar to the previous example, except that the H2 element appears naturally in the last column. Still, there is not enough room to make the element spanning.
 <div class=cols style="height: 100px">
 <div class="col" style="">
 <p>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 </div>
 <div class="col" style="left: 175px">
 <p>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs
 </div>
 <div class="col" style="left: 350px">
 <p>
 tuv wxy z. Abc de fg<br>
 hi jklmno.
 <div class=rep style="width: 140px; height: 40px; background: silver; font-size: 1.5em; padding: 5px; margin: 0; position: static">An H2 element</div>
 </div>
 <div class="col" style="left: 525px">
 <p>A bc def g hij klm<br>
 nop w rstu vw xyz.
 </div>
 <div class=gap style="left: 150px"></div>
 <div class=gap style="left: 325px"></div>
 <div class=gap style="left: 500px"></div>
 </div>
 </div>
 <div class="example">
 <p>In paged media spanning elements are honored on all pages. In this example, the first three paragraphs have column breaks after them. An spanning <code>H2</code> element appears after the fourth paragraph. This would appear on the first page:
 <div class=cols style="height: 80px; border-bottom: none">
 <div class="col" style="">
 <p>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz.
 </div>
 <div class="col" style="left: 175px">
 <p>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z.
 </div>
 <div class="col" style="left: 350px">
 <p>
 Ab cde fgh i jkl mno.<br>
 Pq rstu vwxyz.
 </div>
 <div class=gap style="left: 150px"></div>
 <div class=gap style="left: 325px"></div>
 </div>
 <p>This would appear on the second page:
 <div class=cols style="height: 200px; border-top: none">
 <p>Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 <br><br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 <div class="col" style="left: 175px">
 <p>def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 <br><br>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 </div>
 <div class="col" style="left: 350px">
 <p>
 hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 <br><br>
 hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz.
 </div>
 <div class=rep style="width: 490px; height: 20px; background: silver; font-size: 1.5em; padding: 5px">An H2 element</div>
 <div class=gap style="left: 150px"></div>
 <div class=gap style="left: 325px"></div>
 </div>
 </div>
 <h2>Filling columns</h2>
 <p>There are two strategies for filling columns: columns can either be
 balanced, or not. If columns are balanced, user agents should try to
 fill all columns in a row so that the columns appear to have the same
 amount of content, while also trying to minimize the overflow content.
 If columns are not balanced, they are filled sequentially; some
 columns may end up partially filled, or with no content at all. In any
 case, user agents must honor forced page breaks and should try to
 honor 'widows', 'orphans' and other properties that may affect column
 lengths.
 <h3 id='cf'>'column-fill'</h3>
 <table class=propdef>
     <tr>
       <td><em>Name:</em>
       <td><dfn>column-fill</dfn>
     <tr>
       <td><em>Value:</em>
       <td>auto | balance
     <tr>
       <td><em>Initial:</em>
       <td>balance
     <tr>
       <td><em>Applies to:</em>
       <td>multicol elements
     <tr>
       <td><em>Inherited:</em>
       <td>no
     <tr>
       <td><em>Percentages:</em>
       <td>N/A
     <tr>
       <td><em>Media:</em>
       <td>see below
     <tr>
       <td><em>Computed&nbsp;value:</em>
       <td>specified value
     <tr>
       <td><em>Animatable:</em>
       <td>no
 </table>
 <p>The values are:
 <dl>
 <dt>balance
 <dd>Balance content equally between columns, if possible.
 <dt>auto
 <dd>Fills columns sequentially.
 </dl>
 <!--
 <p>In continuous media, this property will only be consulted if the
 length of columns has been constrained. Otherwise, columns will
 automatically be balanced.
 -->
 <p>In continuous media, this property does not have any effect in
 overflow columns (see below).
 <!--
 <p>In paged media, this property will only have
 effect on the last page the multicol element appears on.
 -->
 <h2>Overflow</h2>
 <h3>Overflow inside multicol elements</h3>
 <p>Content in the normal flow that extends into column gaps (e.g.,
 long words or images) is clipped in the middle of the column gap.
 <div class=example>
 <p>In this example, the black image is wider than the column, and is
 therefore clipped.
 <div class=cols>
 <p>Lorem ipsum dolor<br>sit amet. Nam at jus.
 <br><br><br><br><br><br><br>
 Sed imp er di et ris.<br>Cur abi tur et sapen.
 <div style="position: absolute; left: 175px; top: 0; z-index: 6;">
 <p>Lorem ipsum dolor<br>sit amet. Nam at jus.<br>
 Sed imp er di et ris.<br>Cur abi tur et sapen.<br>
 Vivamus a metus.<br> Aenean at risus<br> pharetra ante
 luctu<br> feugiat quis enim.<br> Cum sociis natoque<br>
 penatibus et magni.</div>
 <div style="position: absolute; left: 350px; top: 0; z-index: 6;">
 <p>Lorem ipsum dolor<br>sit amet. Nam at jus.<br>
 Sed imp er di et ris.<br>Cur abi tur et sapen.<br>
 Vivamus a metus.<br> Aenean at risus<br> pharetra ante
 luctu<br> feugiat quis enim.<br> Cum sociis natoque<br>
 penatibus et magni.</div>
 <div class=rep style="width: 163px"></div>
 <div class=gap style="left: 150px"></div>
 <div class=gap style="left: 325px"></div>
 </div>
 </div>
 <h3>Pagination and overflow outside multicol elements</h3>
 <p>Content and column rules that extend outside column boxes at
 the edges of the multi-column element are clipped according to the
 'overflow' property.
 <p>A multicol element can have more columns than it has room for due to:
 <ul>
 <li>a declaration that constrains the column height (e.g., using
      'height' or 'max-height'). In this case, additional column boxes
      are created in the inline direction
 <li>the size of the page. In this case, additional column boxes are
      moved to the next page(s).
 <li>explicit column breaks. In this case, additional column boxes are
      created in the inline direction for continuous media, and
      additional column boxes are moved to the next page(s) for paged
      media.
 </ul>
 <p>Columns that appear outside the multicol element in continuous media
 are called <dfn>overflow columns</dfn>.
 <div class="example">
 <p>In this example, the height of the multi-column element has been
 constrained to a maximum height. Also, the style sheet specifies that
 overflowing content should be visible:
 <pre class=css>
 div {
   max-height: 5em;
   overflow: visible;
 }
 </pre>
 <p>As a result, the number of columns is increased.
 <div class=cols style="height: 100px">
 <div class="col" style="">
 <p>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 </div>
 <div class="col" style="left: 175px">
 <p>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs
 </div>
 <div class="col" style="left: 350px">
 <p>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 </div>
 <div class="col" style="left: 525px">
 <p>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 </div>
 <div class=gap style="left: 150px"></div>
 <div class=gap style="left: 325px"></div>
 <div class=gap style="left: 500px"></div>
 </div>
 </div>
 <div class="example">
 <p>In paged media, the overflow content goes into column on subsequent pages. Given the same content as in the previous example and a page box that only has room for five lines of formatted text, this would appear on the first page:
 <div class=cols style="height: 100px; border-bottom: none">
 <div class="col" style="">
 <p>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 </div>
 <div class="col" style="left: 175px">
 <p>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs
 </div>
 <div class="col" style="left: 350px">
 <p>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 x yz. Abc def ghi jkl.<br>
 M nop qrst uv wx yz.<br>
 Ab cde fgh i jkl. Mno<br>
 </div>
 <div class=gap style="left: 150px"></div>
 <div class=gap style="left: 325px"></div>
 </div>
 <p>Assuming column balancing, this would appear on the second page:
 <div class=cols style="height: 45px; border-top: none">
 <div class="col" style="">
 <p>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 </div>
 <div class="col" style="left: 175px">
 <p>
 tuv wxy z. Abc de fg<br>
 hi jklmno. Pqrstu vw<br>
 </div>
 <div class="col" style="left: 350px">
 <p>
 x yz. Abc def ghi jkl.<br>
 </div>
 <div class=gap style="left: 150px"></div>
 <div class=gap style="left: 325px"></div>
 </div>
 </div>
 <div class="example">
 <p>In this example, explicit column breaks are generated after paragraphs:
 <pre class=css>
 p {
   break-after: column;
 }
 </pre>
 <p>As a result, the number of columns increases and the extra columns
 are added in the inline direction:
 <div class=cols style="height: 100px">
 <div class="col" style="">
 <p>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz.
 </div>
 <div class="col" style="left: 175px">
 <p>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxyz. Abc defghi<br>
 jklmno pqrstu vwxyz.
 </div>
 <div class="col" style="left: 350px">
 <p>
 Ab cde fgh i jkl mno.<br>
 </div>
 <div class="col" style="left: 525px">
 <p>
 Pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxy z.
 </div>
 <div class=gap style="left: 150px"></div>
 <div class=gap style="left: 325px"></div>
 <div class=gap style="left: 500px"></div>
 </div>
 </div>
 <div class="example">
 <p>In paged media, extra columns are shown on the next page. Given the
 same code as the previous example, the last paragraph appears on the second page. This would appear on the first page:
 <div class=cols style="height: 100px; border-bottom: none">
 <div class="col" style="">
 <p>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz.
 </div>
 <div class="col" style="left: 175px">
 <p>
 Ab cde fgh i jkl. Mno<br>
 pqr stu vw xyz. A bc<br>
 def g hij klm nopqrs<br>
 tuv wxyz. Abc defghi<br>
 jklmno pqrstu vwxyz.
 </div>
 <div class="col" style="left: 350px">
 <p>
 Ab cde fgh i jkl mno.<br>
 </div>
 <div class=gap style="left: 150px"></div>
 <div class=gap style="left: 325px"></div>
 </div>
 <p>This would appear on the second page:
 <div class=cols style="height: 23px; border-top: none">
 <div class="col" style="">
 <p>
 Pqr stu vw xyz. A bc
 </div>
 <div class="col" style="left: 175px">
 <p>
 def g hij klm nopqrs
 </div>
 <div class="col" style="left: 350px">
 <p>
 tuv wxy z.
 </div>
 <div class=gap style="left: 150px"></div>
 <div class=gap style="left: 325px"></div>
 </div>
 Due to column balancing, the last paragraph is split across three columns.
 </div>
 <h2>Conformance</h2>
 <p>Conforming UAs must flow the content of an element into several
 columns according to this specification.
 <p>The 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. All of the text of this specification is
     normative except sections explicitly marked as non-normative, examples,
     and notes. [[!RFC2119]]</p>
 <h3 id=cr-exit-criteria>CR exit criteria</h3>
 <p>As described in the W3C process document, a <a
 href="http://www.w3.org/2005/10/Process-20051014/tr.html#cfi">Candidate
 Recommendation</a> (CR) is a specification that W3C recommends for use
 on the Web. The next stage is <em>Recommendation</em>, when the
 specification is sufficiently implemented.
 <p>For this specification to be proposed as a W3C Recommendation, the
 following conditions shall be met. There must be at least two
 independent, interoperable implementations of each feature. Each
 feature may be implemented by a different set of products, there is no
 requirement that all features be implemented by a single product. For
 the purposes of this criterion, we define the following terms:
 <dl>
   <dt>independent <dd>each implementation must be developed by a
   different party and cannot share, reuse, or derive from code
   used by another qualifying implementation. Sections of code that
   have no bearing on the implementation of this specification are
   exempt from this requirement.
   <dt>interoperable <dd>passing the respective test case(s) in the
   official CSS test suite, or, if the implementation is not a Web
   browser, an equivalent test. Every relevant test in the test
   suite should have an equivalent test created if such a user
   agent (UA) is to be used to claim interoperability. In addition
   if such a UA is to be used to claim interoperability, then there
   must one or more additional UAs which can also pass those
   equivalent tests in the same way for the purpose of
   interoperability. The equivalent tests must be made publicly
   available for the purposes of peer review.
   <dt>implementation <dd>a user agent which:
   <ol class="inline">
     <li>implements the specification.
     <li>is available to the general public. The implementation may
     be a shipping product or other publicly available version
     (i.e., beta version, preview release, or <em>nightly build</em>).
     Non-shipping product releases must have implemented the
     feature(s) for a period of at least one month in order to
     demonstrate stability.
     <li>is not experimental (i.e., a version specifically designed
     to pass the test suite and is not intended for normal usage
     going forward).
   </ol>
 </dl>
 <p>A minimum of sixth months of the CR period must have elapsed. This
 is to ensure that enough time is given for any remaining major errors
 to be caught.
 <p>Features will be dropped if two or more interoperable
 implementations are not found by the end of the CR period.
 <p>Features may/will also be dropped if adequate/sufficient (by
 judgment of CSS WG) tests have not been produced for those feature(s)
 by the end of the CR period.
 <h2 class=no-num id=acknowledgments>Acknowledgments</h2>
 <p>This document is based on several older proposals and comments on
 older proposals. Contributors include
 Øyvind Stenhaug,
 Sylvain Galineau,
 Giovanni Campagna,
 David Hyatt,
 David Singer,
 David Woolley,
 Elika Etemad,
 Bj&ouml;rn H&ouml;hrmann,
 Joost de Valk,
 Peter-Paul Koch,
 Shelby Moore,
 Till Halbach,
 C&eacute;dric Savarese,
 Andy Clarke,
 Robert O'Callahan,
 Markus Mielke,
 Alex Mogilevsky,
 Sergey Genkin,
 Michael Day,
 Melinda Grant,
 Kevin Lawver,
 Anton Prowse,
 L. David Baron,
 Bert Bos,
 Dave Raggett,
 Chris Wilson,
 Robert Stevahn,
 Peter Linss,
 Chris Lilley,
 Steve Zilles,
 Tantek &Ccedil;elik,
 Daniel Glazman and
 Ian Hickson.</p>
 <h2 class=no-num id=references>References</h2>
 <h3 class="no-num" id="normative-references">Normative references</h3>
 <!--begin-normative-->
 <p>[Here will be inserted the file "normative.inc"]</p>
 <!--end-normative-->
 <h3 class="no-num" id="other-references">Other references</h3>
 <!--begin-informative-->
 <p>[Here will be inserted the file "informative.inc"]</p>
 <!--end-informative-->
 <h2 class="no-num" id="index">Index</h2>
 <!--index-->
 <h2 class="no-num" id="property-index">Property index</h2>
 <!-- properties -->
 </body>
 </html>
 <!-- Keep this comment at the end of the file
 Local variables:
 mode: sgml
 sgml-declaration:"~/SGML/HTML4.decl"
 sgml-default-doctype-name:"html"
 sgml-minimize-attributes:t
 sgml-nofill-elements:("pre" "style" "br")
 sgml-live-element-indicator:t
 sgml-omittag:nil
 sgml-shorttag:nil
 sgml-namecase-general:t
 sgml-general-insert-case:lower
 sgml-always-quote-attributes:t
 sgml-indent-step:nil
 sgml-indent-data:t
 sgml-parent-document:nil
 sgml-exposed-tags:nil
 sgml-local-catalogs:nil
 sgml-local-ecat-files:nil
 End:
 -->

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