[css-display-3] Define parent box by applying edits saved in a local patch file called “junk”. :/

Author: fantasai

css-display-3/Overview.bs

@@ -69,16 +69,21 @@ Introduction</h2>
 	Then, for each [=CSS/element=],
 	CSS generates zero or more <a>boxes</a>
 	as specified by that element's 'display' property.
-	Typically, an element generates a single <a>box</a>.
+	Typically, an element generates a single <a>principal box</a>,
+	which represents itself and contains its contents in the <a>box tree</a>.
 	However, some 'display' values
 	(e.g. ''display: list-item'')
 	generate more than one box
-	(e.g. a <a href="https://www.w3.org/TR/CSS2/visuren.html#principal-box">principal block box</a> and a <a href="https://www.w3.org/TR/CSS2/generate.html#lists">marker box</a>).
+	(e.g. a <a href="https://www.w3.org/TR/CSS2/visuren.html#principal-box">principal block box</a> and a child <a href="https://www.w3.org/TR/CSS2/generate.html#lists">marker box</a>).
 	And some values
 	(such as ''display/none'' or ''display/contents'')
 	cause the [=CSS/element=] and/or its descendants to not generate any <a>boxes</a> at all.
 	<a>Boxes</a> are often referred to by their 'display' type--
 	e.g. a <a>box</a> generated by an element with ''display: block'' is called a “block box” or just a “block”.
+	The <dfn export for=CSS>parent box</dfn> of an element’s <a>principal box</a>
+	is (except in the case of ''run-in'')
+	the <a>principal box</a> of its nearest ancestor element
+	that generates a <a>box</a>.
 
 	A <a>box</a> is assigned the same styles as its generating [=CSS/element=], unless otherwise indicated.
 	In general, <a>inherited properties</a> are assigned to the <a>principal box</a>,