[css-writing-modes-3] Define automatic sizing of orthogonal flows. (Definition was lost in 88d115f) Fixes #4220.

Author: fantasai

css-writing-modes-3/Overview.bs

@@ -1999,7 +1999,7 @@ Orthogonal Flows</h3>
   </div>
 
 <h4 id="orthogonal-auto">
-Available Space in Orthogonal Flows</h4>
+Available Space of Orthogonal Flows</h4>
 
   <p>It is common in CSS for a containing block to have a definite <a>inline size</a>,
     but not a definite <a>block size</a>.
@@ -2020,10 +2020,10 @@ Available Space in Orthogonal Flows</h4>
     In such cases a percentage of the containing block’s <a>inline size</a> cannot be defined,
     and <a>inline axis</a> computations cannot be resolved.
     In these cases,
-    an additional constraint is used as a <a>fallback</a>
+    an additional [=fallback size=] is used
     in place of the <a>available inline space</a>
-    for calculations that require a definite <a>available inline space</a>--
-    the smallest of
+    for calculations that require a definite <a>available inline space</a>:
+    this size is the smallest of
     <ul>
       <li>the size represented by
           the containing block’s inner <a>max size</a> (if that is fixed)
@@ -2036,6 +2036,21 @@ Available Space in Orthogonal Flows</h4>
 
   <p>See [[!CSS3-SIZING]] for further details on CSS sizing terminology and concepts.
 
+<h4 id="orthogonal-layout">
+Auto-sizing Orthogonal Flow Roots</h4>
+
+  The [=automatic size=] of an [=orthogonal flow=]
+  (i.e. the size used when its [=preferred size property=] is ''width/auto'')
+  is calculating as its [=fit-content size=], i.e.
+  <code>min([=max-content size=], max([=min-content size=], [=stretch-fit size=])</code>,
+  where the [=available space=] is
+  either the corresponding size of the [=containing block=] if that is [=definite=],
+  or else the [=fallback size=] as defined [[#orthogonal-auto|above]].
+
+  The [=automatic sizing=] of orthogonal [=multi-column containers=]
+  is undefined in this level;
+  see <a href="https://www.w3.org/TR/css-writing-modes-4/#auto-multicol">CSS Writing Modes Level 4</a>.
+
 <h4 id="orthogonal-pagination">
 Fragmenting Orthogonal Flows</h4>
 
@@ -2485,6 +2500,16 @@ Privacy and Security Considerations {#priv-sec}
 
 <h2 class="no-num" id="changes">Changes</h2>
 
+  <h3 class="no-num" id="changes-20190730">
+  Changes since the <a href="https://www.w3.org/TR/2019/CR-css-writing-modes-3-20190730/">July
+  2091 CSS Writing Modes Module Level 3 Candidate Recommendation</a></h3>
+
+  <ul>
+    <li>Added back accidentally-dropped rules for sizing [=orthogonal flows=].
+      Updated wording to use current [[css-sizing-3] terminology.
+      (<a href="https://github.com/w3c/csswg-drafts/issues/4220">Issue 4220</a>)
+  </ul>
+
   <h3 class="no-num" id="changes-201805">
   Changes since the <a href="https://www.w3.org/TR/2018/CR-css-writing-modes-3-20180524/">May
   2018 CSS Writing Modes Module Level 3 Candidate Recommendation</a></h3>