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Rossen Atanassov
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[css-break] Addressing transformed overflow fragmentation issue.
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‎css-break/Overview.html

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@@ -12,11 +12,11 @@
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rel=dcterms.rights>
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<meta content="CSS Fragmentation Module Level 3" name=dcterms.title>
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<meta content=text name=dcterms.type>
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<meta content=2014-01-15 name=dcterms.date>
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<meta content=2014-10-28 name=dcterms.date>
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<meta content="Rossen Atanassov" name=dcterms.creator>
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<meta content="Microsoft Corporation" name=dcterms.creator>
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<meta
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content="<a class=&quot;fn&quot; href=&quot;http://fantasai.inkedblade.net/contact&quot;>Elika J. Etemad</a>"
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content="&#60;a class=&quot;fn&quot; href=&quot;http://fantasai.inkedblade.net/contact&quot;&#62;Elika J. Etemad&#60;/a&#62;"
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name=dcterms.creator>
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<meta content="Mozilla Corporation" name=dcterms.creator>
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<meta content=W3C name=dcterms.publisher>
@@ -36,7 +36,7 @@ <h1 id=css-fragmentation-module>CSS Fragmentation Module Level 3</h1>
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<h2 class="no-num no-toc" id=subtitle>Breaking the Web, one fragment at a
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time</h2>
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<h2 class="no-num no-toc">Editor's Draft 15 January 2014</h2>
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<h2 class="no-num no-toc">Editor's Draft 28 October 2014</h2>
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<dl>
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<dt>This version:
@@ -368,6 +368,7 @@ <h2 id=fragmentation-model><span class=secno>2. </span> Fragmentation Model
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a <a href="http://www.w3.org/TR/css3-page/">paged media display</a>. A
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given fragmentation context can only have one block flow direction across
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all its <a href="#fragmentainer"><i>fragmentainers</i></a>.
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<!-- XXX clarify that multiple writing modes are allowed, just fragmentationis in one direction -->
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<dt><dfn id=fragmented-flow>fragmented flow</dfn>
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@@ -422,8 +423,8 @@ <h2 id=fragmentation-model><span class=secno>2. </span> Fragmentation Model
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boxes</a> across <a
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href="http://www.w3.org/TR/CSS21/visuren.html#line-box">line boxes</a>.
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However, inline breaking is not covered here; see <a href="#ref-CSS21"
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rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>/<a href="#ref-CSS3TEXT"
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rel=biblioentry>[CSS3TEXT]<!--{{CSS3TEXT}}--></a>.
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rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>/<a href="#ref-CSS-TEXT-3"
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rel=biblioentry>[CSS-TEXT-3]<!--{{CSS-TEXT-3}}--></a>.
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<h3 id=parallel-flows><span class=secno>2.1. </span> Parallel Fragmentation
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Flows</h3>
@@ -457,6 +458,7 @@ <h3 id=parallel-flows><span class=secno>2.1. </span> Parallel Fragmentation
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within the context of the box's <a href="#fragmented-flow"><i>fragmented
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flow</i></a> following normal fragmentation rules, increasing the length
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of the <a href="#fragmented-flow"><i>fragmented flow</i></a> as necessary.
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<!-- XXX this paragraph is generally confusing -->
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<h3 id=nested-flows><span class=secno>2.2. </span> Nested Fragmentation
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Flows</h3>
@@ -921,8 +923,9 @@ <h3 id=possible-breaks><span class=secno>4.1. </span> Possible Break Points</h3>
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<dd> When the block flow direction of the siblings' containing block is
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parallel to that of the fragmentation context: in-flow block-level
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boxes, a float and an immediately-adjacent in-flow or floated box,
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table row group boxes, table row boxes, multi-column column row boxes.
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boxes, <!-- XXX linkify in-flow --> a float and an immediately-adjacent
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in-flow or floated box, table row group boxes, table row boxes,
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multi-column column row boxes.
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<dt>Block-perpendicular Fragmentation
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@@ -940,7 +943,7 @@ <h3 id=possible-breaks><span class=secno>4.1. </span> Possible Break Points</h3>
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<dd> Between the content edge of a block container box and the outer edges
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of its child content (margin edges of block-level children or line box
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edges for inline-level children) <em>if</em> there is a (non-zero) gap
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between them.
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between them. <!-- XXX add example -->
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</dl>
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<p class=note> There is no inherent prioritization among these classes of
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<p> When paginating, if there are no possible break points below the top of
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the page, and not all the content fits, the UA may break anywhere in order
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to avoid losing content off the edge of the page.
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to avoid losing content off the edge of the page. <span class=issue>Should
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this be generalized to fragmentainer?</span>
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<p class=note> Other layout models may add breakpoints to the above
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classes. For example, <a href="#ref-CSS3-FLEXBOX"
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break</dfn>, which is a break between two <a
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href="http://www.w3.org/TR/CSS21/visuren.html#line-box">line boxes</a>.
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These are not covered in this specification; see <a href="#ref-CSS21"
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rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> <a href="#ref-CSS3TEXT"
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rel=biblioentry>[CSS3TEXT]<!--{{CSS3TEXT}}--></a>.
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rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> <a href="#ref-CSS-TEXT-3"
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rel=biblioentry>[CSS-TEXT-3]<!--{{CSS-TEXT-3}}--></a>.
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<h3 id=forced-breaks><span class=secno>4.3. </span> Forced Breaks</h3>
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@@ -1101,6 +1105,11 @@ <h3 id=unforced-breaks><span class=secno>4.4. </span> Unforced Breaks</h3>
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<p> If that still does not lead to sufficient break points, rule 3 is
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dropped as well, to find still more break points.
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<p class="note issue">This means that ‘<a href="#widows"><code
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class=property>widows</code></a>’ and ‘<a href="#orphans"><code
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class=property>orphans</code></a>’ restrictions are given priority over
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the ‘<code class=css>break-*</code>’ controls.
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<h3 id=best-breaks><span class=secno>4.5. </span> Optimizing Unforced
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Breaks</h3>
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@@ -1171,7 +1180,8 @@ <h3 id=varying-size-boxes><span class=secno>5.1. </span> Breaking into
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Varying-size Fragmentainers</h3>
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<p> When a flow is fragmented into varying-size fragmentainers, the
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following rules are observed for adapting layout:
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following rules are observed for adapting layout:</p>
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<!-- try to make this clearer. Steve suggests swapping first two points, maybe break it up more? -->
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<ul>
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<li> Intrinsic sizes are calculated and maintained across the entire
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edge. (Note in particular that neither the element's own ‘<code
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class=property>direction</code>’ nor its containing block's ‘<code
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class=property>direction</code>’ is used.) See <a
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href="#ref-CSS3-WRITING-MODES"
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rel=biblioentry>[CSS3-WRITING-MODES]<!--{{CSS3-WRITING-MODES}}--></a>.
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href="#ref-CSS-WRITING-MODES-3"
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rel=biblioentry>[CSS-WRITING-MODES-3]<!--{{CSS-WRITING-MODES-3}}--></a>.
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<h4 id=joining-boxes><span class=secno>5.4.1. </span> Joining Boxes for
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‘<a href="#slice"><code class=css>slice</code></a>’</h4>
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other graphical effects. Such effects are applied per fragment: for
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example, rotation applied to a fragmented box will calculate a rotation
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origin for each fragment and independently rotate that fragment around its
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origin. However, the separation and transfer of page boxes <em>should</em>
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occur last; thus a transformed fragment that spans pages <em>should</em>
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be sliced at the page breaks and print in its entirety rather than being
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clipped by its originating page.
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origin. The origin of an overflow-only fragment is determined as if that
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content were overflowing an empty box with zero margins/borders/padding at
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the start of the fragmentainer (see ) However, the separation and transfer
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of page boxes <em>should</em> occur last; thus a transformed fragment that
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spans pages <em>should</em> be sliced at the page breaks and print in its
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entirety rather than being clipped by its originating page.
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<div class=figure>
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<p><img alt="Illustration: Transformed overflow fragmentation"
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src=fragmented-transforms.png>
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<p class=issue> There's an issue of how to handle fragments consisting
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entirely of overflowing content. See <a
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href="http://lists.w3.org/Archives/Public/www-style/2013Dec/0471.html">discussion</a>.
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<p class=caption>A fixed-height box spanning 2.5 pages with overflow
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content spanning to a total of 4 pages. The transform origin of each
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fragment is the center of its border box; the fragment without a border
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box assumes a zero-height box at the start of the overflow.
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</div>
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<p> Absolute positioning affects layout and thus interacts with
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fragmentation. Both the coordinate system and absolutely-positioned boxes
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<dt id=ref-CSS3-REGIONS>[CSS3-REGIONS]
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<dd>Vincent Hardy; Rossen Atanassov; Alan Stearns. <a
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href="http://www.w3.org/TR/2013/WD-css3-regions-20130528/"><cite>CSS
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Regions Module Level 1.</cite></a> 28 May 2013. W3C Working Draft. (Work
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in progress.) URL: <a
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href="http://www.w3.org/TR/2013/WD-css3-regions-20130528/">http://www.w3.org/TR/2013/WD-css3-regions-20130528/</a>
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<dd>Rossen Atanassov; Alan Stearns. <a
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href="http://www.w3.org/TR/2014/WD-css3-regions-20140218/"><cite>CSS
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Regions Module Level 1.</cite></a> 18 February 2014. W3C Working Draft.
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(Work in progress.) URL: <a
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href="http://www.w3.org/TR/2014/WD-css3-regions-20140218/">http://www.w3.org/TR/2014/WD-css3-regions-20140218/</a>
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</dd>
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<!---->
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<dt id=ref-CSS3BG>[CSS3BG]
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<dd>Bert Bos; Elika J. Etemad; Brad Kemper. <a
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href="http://www.w3.org/TR/2012/CR-css3-background-20120724/"><cite>CSS
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Backgrounds and Borders Module Level 3.</cite></a> 24 July 2012. W3C
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href="http://www.w3.org/TR/2014/CR-css3-background-20140909/"><cite>CSS
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Backgrounds and Borders Module Level 3.</cite></a> 9 September 2014. W3C
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Candidate Recommendation. (Work in progress.) URL: <a
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href="http://www.w3.org/TR/2012/CR-css3-background-20120724/">http://www.w3.org/TR/2012/CR-css3-background-20120724/</a>
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href="http://www.w3.org/TR/2014/CR-css3-background-20140909/">http://www.w3.org/TR/2014/CR-css3-background-20140909/</a>
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</dd>
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<!---->
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<dt id=ref-RFC2119>[RFC2119]
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<dd>S. Bradner. <a href="http://www.ietf.org/rfc/rfc2119.txt"><cite>Key
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words for use in RFCs to Indicate Requirement Levels.</cite></a> Internet
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RFC 2119. URL: <a
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words for use in RFCs to Indicate Requirement Levels.</cite></a> RFC
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2119. URL: <a
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href="http://www.ietf.org/rfc/rfc2119.txt">http://www.ietf.org/rfc/rfc2119.txt</a>
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</dd>
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<dd style="display: none"><!-- keeps the doc valid if the DL is empty -->
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<!---->
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<dt id=ref-CSS3-FLEXBOX>[CSS3-FLEXBOX]
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<dt id=ref-CSS-TEXT-3>[CSS-TEXT-3]
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<dd>Tab Atkins Jr.; Elika J. Etemad; Alex Mogilevsky. <a
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href="http://www.w3.org/TR/2012/CR-css3-flexbox-20120918/"><cite>CSS
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Flexible Box Layout Module.</cite></a> 18 September 2012. W3C Candidate
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Recommendation. (Work in progress.) URL: <a
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href="http://www.w3.org/TR/2012/CR-css3-flexbox-20120918/">http://www.w3.org/TR/2012/CR-css3-flexbox-20120918/</a>
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<dd>Elika J. Etemad; Koji Ishii. <a
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href="http://www.w3.org/TR/2013/WD-css-text-3-20131010/"><cite>CSS Text
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Module Level 3.</cite></a> 10 October 2013. W3C Last Call Working Draft.
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(Work in progress.) URL: <a
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href="http://www.w3.org/TR/2013/WD-css-text-3-20131010/">http://www.w3.org/TR/2013/WD-css-text-3-20131010/</a>
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</dd>
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<dt id=ref-CSS3-SIZING>[CSS3-SIZING]
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<dt id=ref-CSS-WRITING-MODES-3>[CSS-WRITING-MODES-3]
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<dd>Tab Atkins Jr.; Elika J. Etemad. <a
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href="http://www.w3.org/TR/2012/WD-css3-sizing-20120927/"><cite>CSS
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Intrinsic &amp; Extrinsic Sizing Module Level 3.</cite></a> 27 September
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2012. W3C Working Draft. (Work in progress.) URL: <a
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href="http://www.w3.org/TR/2012/WD-css3-sizing-20120927/">http://www.w3.org/TR/2012/WD-css3-sizing-20120927/</a>
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<dd>fantasai; Koji Ishii. <a
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href="http://www.w3.org/TR/2014/CR-css-writing-modes-3-20140320/"><cite>CSS
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Writing Modes Level 3.</cite></a> 20 March 2014. W3C Candidate
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Recommendation. (Work in progress.) URL: <a
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href="http://www.w3.org/TR/2014/CR-css-writing-modes-3-20140320/">http://www.w3.org/TR/2014/CR-css-writing-modes-3-20140320/</a>
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</dd>
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<!---->
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<dt id=ref-CSS3-WRITING-MODES>[CSS3-WRITING-MODES]
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<dt id=ref-CSS3-FLEXBOX>[CSS3-FLEXBOX]
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<dd>Elika J. Etemad; Koji Ishii. <a
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href="http://www.w3.org/TR/2012/WD-css3-writing-modes-20121115/"><cite>CSS
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Writing Modes Module Level 3.</cite></a> 15 November 2012. W3C Working
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Draft. (Work in progress.) URL: <a
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href="http://www.w3.org/TR/2012/WD-css3-writing-modes-20121115/">http://www.w3.org/TR/2012/WD-css3-writing-modes-20121115/</a>
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<dd>Tab Atkins Jr.; fantasai; Rossen Atanassov. <a
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href="http://www.w3.org/TR/2014/WD-css-flexbox-1-20140325/"><cite>CSS
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Flexible Box Layout Module Level 1.</cite></a> 25 March 2014. W3C Last
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Call Working Draft. (Work in progress.) URL: <a
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href="http://www.w3.org/TR/2014/WD-css-flexbox-1-20140325/">http://www.w3.org/TR/2014/WD-css-flexbox-1-20140325/</a>
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</dd>
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<dt id=ref-CSS3TEXT>[CSS3TEXT]
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<dt id=ref-CSS3-SIZING>[CSS3-SIZING]
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<dd>Elika J. Etemad; Koji Ishii. <a
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href="http://www.w3.org/TR/2012/WD-css3-text-20121113/"><cite>CSS Text
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Module Level 3.</cite></a> 13 November 2012. W3C Working Draft. (Work in
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progress.) URL: <a
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href="http://www.w3.org/TR/2012/WD-css3-text-20121113/">http://www.w3.org/TR/2012/WD-css3-text-20121113/</a>
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<dd>Tab Atkins Jr.; Elika J. Etemad. <a
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href="http://www.w3.org/TR/2012/WD-css3-sizing-20120927/"><cite>CSS
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Intrinsic &amp; Extrinsic Sizing Module Level 3.</cite></a> 27 September
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2012. W3C Working Draft. (Work in progress.) URL: <a
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href="http://www.w3.org/TR/2012/WD-css3-sizing-20120927/">http://www.w3.org/TR/2012/WD-css3-sizing-20120927/</a>
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</dd>
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<!---->
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‎css-break/Overview.src.html

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@@ -1203,16 +1203,22 @@ <h3 id="transforms">
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for example, rotation applied to a fragmented box
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will calculate a rotation origin for each fragment
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and independently rotate that fragment around its origin.
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(The origin of an overflow-only fragment is determined
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as if that content were overflowing an empty box with zero margins/borders/padding at the start of the fragmentainer.)
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The origin of an overflow-only fragment is determined
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as if that content were overflowing an empty box with zero margins/borders/padding
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at the start of the fragmentainer (see )
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However, the separation and transfer of page boxes <em>should</em> occur last;
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thus a transformed fragment that spans pages <em>should</em>
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be sliced at the page breaks and print in its entirety
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rather than being clipped by its originating page.
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<p class="issue">
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There's an issue of how to handle fragments consisting entirely of overflowing content.
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See <a href="http://lists.w3.org/Archives/Public/www-style/2013Dec/0471.html">discussion</a>.
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<div class="figure">
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<p><img alt="Illustration: Transformed overflow fragmentation"
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src="fragmented-transforms.png">
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<p class=caption>A fixed-height box spanning 2.5 pages with overflow content spanning
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to a total of 4 pages.
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The transform origin of each fragment is the center of its border box;
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the fragment without a border box assumes a zero-height box at the start of the overflow.
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</div>
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<p>
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Absolute positioning affects layout and thus interacts with fragmentation.

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