Clarifications to orthogonal flows mappings

Author: fantasai

css3-writing-modes/Overview.html

@@ -30,15 +30,15 @@
 
    <h1>CSS Writing Modes Module Level 3</h1>
 
-   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 19 May 2011</h2>
+   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 20 May 2011</h2>
 
    <dl>
     <dt>This version:
 
     <dd><a
      href="http://dev.w3.org/csswg/css3-writing-modes/">http://dev.w3.org/csswg/css3-writing-modes/</a>
      <!--
-    <dd><a href="http://www.w3.org/TR/2011/WD-css3-writing-modes-20110519">http://www.w3.org/TR/2011/ED-css3-writing-modes-20110519/</a>
+    <dd><a href="http://www.w3.org/TR/2011/WD-css3-writing-modes-20110520">http://www.w3.org/TR/2011/ED-css3-writing-modes-20110520/</a>
 -->
 
 
@@ -2331,49 +2331,55 @@ <h3 id=orthogonal-flows><span class=secno>7.3. </span> Orthogonal Flows</h3>
     href="#vertical-rl"><code class=css>vertical-rl</code></a>&rsquo;).
   </ul>
 
-  <p>To handle the second case, for the purposes of calculating the layout of
-   the box, the physical dimensions corresponding to the extent and measure
-   of the containing block are determined using the writing mode of the box
-   under consideration, not the writing mode of the element associated with
-   the containing block.
+  <p>To handle the second case, CSS layout calculations are divided into two
+   phases: sizing a box, and positioning the box within its flow. In the
+   sizing phase&#8212;calculating the width and height of the box&#8212;the
+   dimensions of the box and the containing block are mapped to the measure
+   and extent and calculations performed accordingly using the writing mode
+   of the element. In the positioning phase&#8212;calculating the positioning
+   offsets, margins, borders, and padding&#8212;the dimensions of the box and
+   its containing block are mapped to the measure and extent and calculations
+   performed according to the writing mode of the containing block.
 
   <p>For example, if a vertical block is placed inside a horizontal block,
    then when calculating the physical height (which is the measure) of the
    child block the physical height of the parent block is used to calculate
    the measure of the child's containing block, even though the physical
    height is the extent, not the measure, of the parent block.
 
+  <p>Since auto auto margins are resolved consistent with the containing
+   block's writing mode, a box establishing an orthogonal flow, can, once
+   sized, be aligned or centered within its containing block just like other
+   block-level elements by using auto margins.
+
   <p>It is common in CSS for a containing block to have a defined measure,
    but not a defined extent. This typically happens in CSS2.1 when a
    containing block has an &lsquo;<a href="#auto"><code
    class=css>auto</code></a>&rsquo; height, for example: its width is given
    by the calculations in <a
    href="http://www.w3.org/TR/CSS21/visudet.html#blockwidth">10.3.3</a>, but
-   its extent depends on its contents. In such cases the <i>available
-   measure</i> is defined, but the <i>available extent</i> is infinite.
-
-  <p>Orthogonal flows allow the opposite to happen: for the <i>available
-   extent</i> to be defined, but the <i>available measure</i> to be infinite.
-   In such cases a percentage of the containing block measure cannot be
-   defined, and thus the initial containing block's measure is used to
-   calculate such percentages instead. <span class=issue>Is this definition
-   of percentages a good idea?</span>
+   its extent depends on its contents. In such cases the <dfn
+   id=available-measure>available measure</dfn> is defined as the measure of
+   the containing block; but the <dfn id=available-extent>available
+   extent</dfn>, which would otherwise be the extent of the containing block,
+   is infinite.
+
+  <p>Orthogonal flows allow the opposite to happen: for the <a
+   href="#available-extent"><i>available extent</i></a> to be defined, but
+   the <a href="#available-measure"><i>available measure</i></a> to be
+   infinite. In such cases a percentage of the containing block measure
+   cannot be defined, and thus the initial containing block's measure is used
+   instead as a <a href="#fallback-measure"><i>fallback measure</i></a> to
+   calculate such percentages.
 
   <h4 id=orthogonal-auto><span class=secno>7.3.1. </span> Auto-sizing in
    Orthogonal Flows</h4>
 
   <p>If the computed measure of an element establishing an orthogonal flow is
    &lsquo;<a href="#auto"><code class=css>auto</code></a>&rsquo;, then the
-   used measure is calculated as the shrink-to-fit (<a
-   href="#fit-content"><i>fit-content</i></a>) value using the initial
-   containing block's measure as the available size in the shrink-to-fit
-   algorithm.
-
-  <p class=note>As with other shrink-to-fit boxes, the width and height
-   calculations occur before auto margin calculations in the inline
-   dimension, and therefore a block box establishing an orthogonal flow, once
-   sized, can be aligned or centered within its containing block just like
-   other block-level elements by using auto margins.
+   used measure is calculated as the <a
+   href="#fit-content"><i>fit-content</i></a> (shrink-to-fit) size using the
+   initial containing block's measure as the available measure.
 
   <h4 id=orthogonal-multicol><span class=secno>7.3.2. </span> Multi-column
    Layout in Orthogonal Flows</h4>
@@ -3064,9 +3070,10 @@ <h2 class=no-num id=intrinsic-sizing>Appendix D: Intrinsic Dimensions</h2>
     href="http://www.w3.org/TR/CSS21/visudet.html#blockwidth">CSS2.1&sect;10.3.3</a>,
     the <dfn id=fill-available-measure>fill-available measure</dfn> is
     calculated by subtracting out the element's margins, borders, and padding
-    from the <i>available measure</i> and flooring the result at zero. If the
-    available measure is infinite, then a <dfn id=fallback-measure>fallback
-    measure</dfn> is used in place of the <i>available measure</i> in this
+    from the <a href="#available-measure"><i>available measure</i></a> and
+    flooring the result at zero. If the available measure is infinite, then a
+    <dfn id=fallback-measure>fallback measure</dfn> is used in place of the
+    <a href="#available-measure"><i>available measure</i></a> in this
     calculation. (In the case of orthogonal flows, this is the measure of the
     initial containing block.) The <dfn
     id=fill-available-extent>fill-available extent</dfn> is similarly

css3-writing-modes/Overview.src.html

@@ -1698,50 +1698,55 @@ <h3 id="orthogonal-flows">
       example, ''horizontal-tb'' and ''vertical-rl'').</li>
   </ul>
 
-  <p>To handle the second case, for the purposes of calculating the
-    layout of the box, the physical dimensions corresponding to the
-    extent and measure of the containing block are determined
-    using the writing mode of the box under consideration, not the
-    writing mode of the element associated with the containing block.
-    
+  <p>To handle the second case, CSS layout calculations are divided into
+    two phases: sizing a box, and positioning the box within its flow.
+    In the sizing phase&#8212;calculating the width and height of the
+    box&#8212;the dimensions of the box and the containing block
+    are mapped to the measure and extent and calculations performed
+    accordingly using the writing mode of the element.
+    In the positioning phase&#8212;calculating the positioning offsets,
+    margins, borders, and padding&#8212;the dimensions of the box and
+    its containing block are mapped to the measure and extent and
+    calculations performed according to the writing mode of the
+    containing block.
+
   <p>For example, if a vertical block is placed inside a horizontal
     block, then when calculating the physical height (which is the
     measure) of the child block the physical height of the parent
     block is used to calculate the measure of the child's containing
     block, even though the physical height is the extent, not the
     measure, of the parent block.</p>
 
+  <p>Since auto auto margins are resolved consistent with the containing
+    block's writing mode, a box establishing an orthogonal flow, can,
+    once sized, be aligned or centered within its containing block just
+    like other block-level elements by using auto margins.
+
   <p>It is common in CSS for a containing block to have a defined
     measure, but not a defined extent. This typically happens in
     CSS2.1 when a containing block has an ''auto'' height, for
     example: its width is given by the calculations in
     <a href="http://www.w3.org/TR/CSS21/visudet.html#blockwidth">10.3.3</a>,
     but its extent depends on its contents. In such cases the
-    <i>available measure</i> is defined, but the <i>available extent</i>
-    is infinite.
+    <dfn>available measure</dfn> is defined as the measure of the
+    containing block; but the <dfn>available extent</dfn>, which
+    would otherwise be the extent of the containing block, is
+    infinite.
 
   <p>Orthogonal flows allow the opposite to happen: for the
     <i>available extent</i> to be defined, but the <i>available
     measure</i> to be infinite. In such cases a percentage of the
     containing block measure cannot be defined, and thus the
-    initial containing block's measure is used to calculate such
-    percentages instead. <span class="issue">Is this definition
-    of percentages a good idea?</span>
+    initial containing block's measure is used instead as a
+    <i>fallback measure</i> to calculate such percentages.
 
 <h4 id="orthogonal-auto">
 Auto-sizing in Orthogonal Flows</h4>
 
   <p>If the computed measure of an element establishing an orthogonal
     flow is ''auto'', then the used measure is calculated as the
-    shrink-to-fit (<i>fit-content</i>) value using the initial containing
-    block's measure as the available size in the shrink-to-fit algorithm.
-
-  <p class="note">As with other shrink-to-fit boxes, the width and
-    height calculations occur before auto margin calculations in the
-    inline dimension, and therefore a block box establishing an
-    orthogonal flow, once sized, can be aligned or centered within
-    its containing block just like other block-level elements by
-    using auto margins.
+    <i>fit-content</i> (shrink-to-fit) size using the initial containing
+    block's measure as the available measure.
 
 <h4 id="orthogonal-multicol">
 Multi-column Layout in Orthogonal Flows</h4>