[css-overflow-3] Clarify that we mean the padding box (including the content area, not the actual box contents) in point 1.

Author: fantasai

css-backgrounds-3/Overview.bs

@@ -1,16 +1,16 @@
 <pre class='metadata'>
 Title: CSS Backgrounds and Borders Module Level 3
-Status: CR
-Date: 2020-12-22
-Deadline: 2021-02-22
-Prepare for TR: yes
+Status: CRD
+Date: 2021-07-26
+Deadline: 2021-08-22
 Implementation Report: https://test.csswg.org/harness/results/css-backgrounds-3_dev/grouped/
 Work Status: Testing
 Shortname: css-backgrounds
 Level: 3
 Group: csswg
 ED: https://drafts.csswg.org/css-backgrounds/
 TR: https://www.w3.org/TR/css-backgrounds-3/
+Previous Version: https://www.w3.org/TR/2020/CR-css-backgrounds-3-20201222/
 Previous Version: https://www.w3.org/TR/2017/CR-css-backgrounds-3-20171017/
 Previous version: https://www.w3.org/TR/2014/CR-css3-background-20140909/
 Editor: Bert Bos, W3C, bert@w3.org, w3cid 3343
@@ -3051,6 +3051,7 @@ Changes since the 22 December 2020 Candidate Recommendation Snapshot</h3>
     when it doesn't generate boxes only applies to ''display: none'',
     not ''display: contents''.
     (<a href="https://github.com/w3c/csswg-drafts/issues/3779">Issue 3779</a>)
+  <li>Minor editorial improvements.
 </ul>
 
 <h3 id="changes-2017-10">

css-overflow-3/Overview.bs

@@ -206,7 +206,7 @@ Scrollable Overflow</h3>
 	The <a>scrollable overflow area</a> is the union of:
 	<ul>
 		<li>
-			the box’s own content and padding areas
+			the box’s own [=padding box=]
 
 			<div class=issue>
 				There's disagreement on the scrolling model.
@@ -490,14 +490,68 @@ Scrollbars and Layout</h3>
 	For the purpose of the [=background positioning area=] and [=background painting area=], however,
 	this reserved space is considered to be part of the [=padding box=].
 
+	<div class="example">
+		In the following document fragment,
+		both an absolutely-positioned element
+		and a background image
+		are positioned to the top right of the box.
+
+		<xmp highlight=html>
+			<style>
+			  article { background: top right no-repeat url(circle.png); }
+			  aside { position: absolute; top: 0; right: 0; }
+			</style>
+			<article>
+			  <aside>×</aside>
+			</section>
+		</xmp>
+
+		If no scrollbars are present on <code>&lt;article></code>,
+		they will both coincide in the top right padding edge corner.
+		However, if scrollbars are present
+		then <code>&lt;aside></code> will be completely visible,
+		on the right padding-box edge adjacent to the scrollbars;
+		whereas the background image will be tucked underneath the scrollbars,
+		in the top right corner of the scrollbar-extended [=background positioning area=].
+	</div>
+
 	When the box is sized to fit its contents,
 	this reserved space is added to the size of its contents.
 	It is otherwise subtracted from space alotted to the [=content area=].
 	To the extent that the presence of scrollbars can affect sizing,
 	UAs must start with the assumption that no scrollbars are needed,
 	and recalculate sizes if it turns out they are.
 
-	Issue: import examples from [[CSS3-BOX]].
+	<div class="example">
+		In the following document fragment,
+		the outer <code>&lt;article></code> has ''height: auto'', but ''max-height: 5em''.
+		The inner <code>&lt;section></code> has large margins and would normally just fit:
+
+		<xmp highlight=html>
+			...
+			    article { overflow: auto; max-height: 5em;  width: max-content; }
+			    section { margin: 2em; line-height: 1 }
+			...
+			<article>
+			  <section>
+			    This section has big margins.
+			  </section>
+			</section>
+		</xmp>
+
+		If we assumed that <code>&lt;article></code> needed scrollbars,
+		then the height of <code>&lt;section></code>,
+		including the single line of text and twice 2em of margins,
+		adds up to 5em plus a scrollbar.
+		Since that is greater than 5em, the maximum allowed height,
+		it seems we made the right assumption and d1 indeed needs scrollbars.
+
+		However, we should have started by assuming that no scrollbars are needed.
+		In that case the content height of <code>&lt;article></code>
+		is exactly the maximum height of 5em,
+		proving that the assumption was correct
+		and <code>&lt;article></code> indeed should not have scrollbars.
+	</div>
 
 <h3 id="scrolling-direction">
 Scrolling Origin, Direction, and Restriction</h3>