[css-flexbox] Reword main/cross size dfns. Make it clearer that any reference to used width/height refers to the flexed size.

Author: tabatkins

css-flexbox-1/Overview.bs

@@ -473,17 +473,24 @@ Flex Layout Box Model and Terminology</h2>
 		<dt class='size'>main size
 		<dt class='size'>main size property
 		<dd>
-			The width or height of a <a>flex container</a> or <a>flex item</a>,
-			whichever is in the <a>main dimension</a>,
-			is that box’s <dfn lt="main size|main-size">main size</dfn>.
-			Its <dfn>main size property</dfn> is
-			thus either its 'width' or 'height' property,
-			whichever is in the <a>main dimension</a>.
-			Similarly, its <dfn lt="min main size property">min</dfn> and
+			The <dfn>main size</dfn> of a [=flex container=] or [=flex item=]
+			refers to its [=width=] or [=height=],
+			whichever is in the [=main dimension=].
+			Its <dfn>main size property</dfn>
+			is either its 'width' or 'height' property,
+			whichever is in the [=main dimension=].
+			Likewise, its <dfn lt="min main size property">min</dfn> and
 			<dfn lt="max main size property">max main size properties</dfn>
 			are its 'min-width'/'max-width' or 'min-height'/'max-height' properties,
-			whichever is in the <a>main dimension</a>,
+			whichever are in the <a>main dimension</a>,
 			and determine its <dfn lt="min main size">min</dfn>/<dfn>max main size</dfn>.
+
+			In [=flex layout=], the [=main size=] is controlled by the 'flex' property
+			rather than directly by the [=main size property=].
+
+			Note: This means any references to a flex item's used size in the [=main dimension=]
+			([=width=], [=height=], [=inline size=], [=block size=])
+			refers to its post-flexing [=main size=].
 	</dl>
 
 	<dl id="cross" export>
@@ -503,16 +510,16 @@ Flex Layout Box Model and Terminology</h2>
 		<dt class='size'>cross size
 		<dt class='size'>cross size property
 		<dd>
-			The width or height of a <a>flex container</a> or <a>flex item</a>,
-			whichever is in the <a>cross dimension</a>,
-			is that box’s <dfn lt="cross size | cross-size">cross size</dfn>.
-			Its <dfn>cross size property</dfn> is
-			thus either its 'width' or 'height' property,
-			whichever is in the <a>cross dimension</a>.
-			Similarly, its <dfn lt="min cross size property">min</dfn> and
+			The <dfn>cross size</dfn> of a [=flex container=] or [=flex item=]
+			refers to its [=width=] or [=height=],
+			whichever is in the [=cross dimension=].
+			Its <dfn>cross size property</dfn>
+			is either its 'width' or 'height' property,
+			whichever is in the [=cross dimension=].
+			Likewise, its <dfn lt="min cross size property">min</dfn> and
 			<dfn lt="max cross size property">max cross size properties</dfn>
 			are its 'min-width'/'max-width' or 'min-height'/'max-height' properties,
-			whichever is in the <a>cross dimension</a>,
+			whichever are in the <a>cross dimension</a>,
 			and determine its <dfn lt="min cross size">min</dfn>/<dfn>max cross size</dfn>.
 	</dl>