[css-inline-3] Define that initial letters are extracted from their parents, geometrically-speaking. #2184

Author: fantasai

css-inline-3/Overview.bs

@@ -1188,6 +1188,19 @@ Edge Effects: Indentation and Hanging Punctuation</h4>
 		<figcaption>Initial letter with text indent. </figcaption>
 	</figure>b
 
+<h4 id="initial-letter-ancestors">
+Ancestor Inlines</h4>
+
+	If the <a>initial letter box</a> is contained by <a>inline box</a> ancestors,
+	the boundaries of those <a>inline boxes</a> are drawn
+	to exclude the <a>initial letter box</a>,
+	as if it were outside their startmost <a>margin edge</a>.
+	This is a purely geometric operation:
+	it does not affect e.g.
+	property inheritance or
+	the effective 'letter-spacing' between the <a>initial letter box</a>
+	and subsequent content.
+
 <h4 id="initial-letter-multi-line">
 Multi-line Initial Letters</h4