[css-overflow-3] Add text rendering example to ink overflow section. #8649 #10066

Author: fantasai

css-overflow-3/Overview.bs

@@ -190,11 +190,13 @@ Overflow Concepts and Terminology</h2>
 	<a href="https://www.w3.org/TR/css-ui-3/#outline-props">outlines</a>,
 	etc.
 
-	Since some effects in CSS (for example, the blurs in
-	'text-shadow' [[CSS-TEXT-3]] and 'box-shadow' [[CSS-BACKGROUNDS-3]],
-	which are theoretically infinite)
-	do not define what visual extent they cover, the extent
-	of the <a>ink overflow</a> is undefined.
+	Since some effects in CSS (for example,
+	the blurs in 'text-shadow' [[CSS-TEXT-3]] and 'box-shadow' [[CSS-BACKGROUNDS-3]],
+	which are theoretically infinite;
+	or text rendering, where shaping and rasterization can vary by platform)
+	do not precisely define what visual extent they cover,
+	the extent of the <a>ink overflow</a> is undefined,
+	and may vary across UAs.
 
 	The <dfn export lt="ink overflow region | ink overflow area">ink overflow area</dfn> is the non-rectangular area
 	occupied by the <a>ink overflow</a>