[css-flexbox] Expand issue discussion wrt flex-basis: auto

--HG--
extra : rebase_source : 5e00f3cb2b82e57fc36734bdb8a8feef14369adb

Author: fantasai

css-flexbox/Overview.bs

@@ -1698,8 +1698,32 @@ The 'flex-basis' property</h4>
 		The <dfn value for=flex-basis>main-size</dfn> keyword, when specified on a <i>flex item</i>,
 		retrieves the value of the <i>main size property</i>.
 
-	Issue: This value was originally named "auto",
-	but that was confusing
+	<div class="issue">
+		This value was originally named ''auto'',
+		but that was problematic because it left us with no keyword to represent an automatic flex basis.
+		There were two options for fixing this:
+
+		<dl>
+			<dt>''auto'' for automatic sizing; ''main-axis'' for size lookup
+			<dd>
+				The advantage of this is primarily that ''auto'' means “automatic”
+				both when it is specified for 'flex-basis' and when it is pulled in from 'width'/'height'.
+				It has the disadvantage (due to back-compat concerns) that the 'flex' shorthand had to be tweaked
+				to expand ''flex: auto'' to ''flex: auto main-size'' rather than to ''flex: 1 auto''.
+				It is the currently-implemented option, but may be unshippable due to back-compat constraints.
+			<dt>''auto'' for size lookup; ''content''<sup>1</sup> for automatic sizing
+			<dd>
+				The advantage of this is that it will not break existing content:
+				a 'flex-basis' keyword for automatic sizing did not exist in the original CR,
+				so this option adds a new keyword but does not rename existing functionality.
+				It therefore avoids the ''flex: auto'' &ne; ''flex: 1 auto'' inequality.
+		</dl>
+
+		The CSSWG is waiting for feedback from implementers on this issue.
+		
+		<small><sup>1</sup> Alternate keyword suggestions welcome.</small>
+		<small><sup>1</sup> Alternate keyword suggestions welcome.</small>
+	</div>
 
 	<p>
 		The <i>flex basis</i> is resolved the same way as 'width' in horizontal writing modes [[!CSS21]]:
@@ -3266,8 +3290,15 @@ Changes since the 25 March 2014 LCWD</h3>
 	<a href="http://www.w3.org/TR/2014/WD-css-flexbox-1-20140325/">25 March 2014 Last Call Working Draft</a>:
 
 	<ul>
+		<li id="change-201403-flex-basis-auto">
+			Introduced extra ''main-size'' keyword to 'flex-basis'
+			so that “lookup from main-size property” and “automatic sizing” behaviors
+			could each be explicitly specified.
+			(Issue <a href="http://dev.w3.org/csswg/css-flexbox-1/issues-lc-20140325#issue-20">20</a>)
+
 		<li id="change-201403-min-auto-not">
 			Fixed error in definition of ''min-height/min-width: auto''.
+			(Issue <a href="http://dev.w3.org/csswg/css-flexbox-1/issues-lc-20140325#issue-11">11</a>)
 
 			<blockquote>
 				On a <a>flex item</a> whose 'overflow' is <del>not</del> ''overflow/visible'',