[css-text-decor-4] Split out wording on font metrics in auto position/thickness to appropriate sections.

Author: fantasai

css-text-decor-4/Overview.bs

@@ -325,7 +325,11 @@ Text Decoration Line Thickness: the 'text-decoration-thickness' property</h3>
 <h4 id="text-decoration-thickness">
 Automatic Thickness of Text Decoration Lines</h4>
 
-	Issue: Insert L3 text here.
+	Some font formats (such as OpenType) can offer information
+	about the appropriate thickness of a line decoration.
+	The UA should use such font-based information
+	when choosing ''text-decoration-thickness/auto'' line thicknesses
+	wherever appropriate.
 
 <h3 id="line-position">
 Determining the Position and Thickness of Line Decorations</h3>
@@ -625,6 +629,13 @@ Text Underline Offset: the 'text-underline-offset' property</h3>
 			so that the offset scales with the font.
 	</dl>
 
+	When the value of the 'text-decoration-line' property is either
+	''spelling-error'' or ''grammar-error'',
+	the UA may ignore the value of 'text-underline-position'.
+
+<h4 id="line-offset-zero">
+Underline Offset Origin (Zero Position)</h4>
+
 	The initial position of the underline depends on the value of 'text-underline-position'
 	as detailed below.
 
@@ -660,9 +671,22 @@ Text Underline Offset: the 'text-underline-offset' property</h3>
 			<span class="issue">Should this be removed?</span>
 	</ul>
 
-	When the value of the 'text-decoration-line' property is either
-	''spelling-error'' or ''grammar-error'',
-	the UA may ignore the value of 'text-underline-position'.
+<h4 id="line-auto-offset">
+Using Font Metrics for Automatic Positioning</h4>
+
+	Some font formats (such as OpenType) can offer information
+	about the appropriate position of a line decoration.
+	The UA should use such font-based information
+	in its choice of ''text-underline-offset/auto'' offset
+	wherever appropriate.
+
+	Note: Typically, OpenType font metrics give the position
+	of an ''text-underline-position/alphabetic'' underline;
+	in some cases (especially in CJK fonts),
+	it gives the position of a ''under left'' underline.
+	(In this case, the font's underline metrics typically
+	touch the bottom edge of the em box).
+	The UA may but is not required to correct for incorrect font metrics.
 
 <h3 id="text-line-constancy">
 Text Decoration Line Uniformity</h3>
@@ -738,21 +762,6 @@ Text Decoration Line Uniformity</h3>
 		-->
 	</div>
 
-	Some font formats (such as OpenType) can offer information
-	about the appropriate position of a line decoration.
-	The UA should use such information
-	(such as the underline thickness,
-	or appropriate alphabetic underline position)
-	from the font wherever appropriate.
-
-	Note: Typically, OpenType font metrics give the position
-	of an ''text-underline-position/alphabetic'' underline;
-	in some cases (especially in CJK fonts),
-	it gives the position of a ''under left'' underline.
-	(In this case, the font's underline metrics typically
-	touch the bottom edge of the em box).
-	The UA may but is not required to correct for incorrect font metrics.
-
 <h3 id="text-decoration-skipping">
 Text Decoration Line Continuity</h3>