[css-contain] Clarify behavior of style contaiment on counters

Closes w3c#2483

Author: frivoal

css-contain-1/Overview.bs

@@ -19,6 +19,9 @@ Link Defaults: css-lists-3 (property) counter-increment
 spec: css2; urlPrefix: https://www.w3.org/TR/CSS2/
 	type: property; url: generate.html#propdef-content; text: content
 	type: value; for: content; url: generate.html#value-def-open-quote; text: open-quote
+	type: value; for: content; url: generate.html#value-def-close-quote; text: close-quote
+	type: value; for: content; url: generate.html#value-def-no-open-quote; text: no-open-quote
+	type: value; for: content; url: generate.html#value-def-no-close-quote; text: no-close-quote
 	type: dfn; url: box.html#padding-edge; text: padding edge
 
 spec: css-backgrounds-3;
@@ -268,9 +271,19 @@ Style Containment</h3>
 
 	Giving an element <dfn export>style containment</dfn> has the following effect:
 
-	1. The 'counter-increment', 'counter-set', and <a property spec=css2>content</a> (for the purpose of ''content/open-quote''/etc values) properties
+	1. The 'counter-increment' and 'counter-set' properties
+	    must be <a for=property>scoped</a> to the element's sub-tree
+	    and create a new counter.
+
+	2. The effects of the 'content' property's
+	    ''content/open-quote'', ''content/close-quote'', ''content/no-open-quote'' and ''content/no-close-quote''
 	    must be <a for=property>scoped</a> to the element's sub-tree.
 
+	    Note: This implies that the depth of quote nesting in the subtree
+	    is unchanged and starts at the value that its context normally implies,
+	    but that changes to the depth of quote nesting by these values inside the subtree
+	    do not affect the depth of quote nesting outside the subtree.
+
 	Note: [[CSS-REGIONS-1]] has normative requirements on how <a>style containment</a> affects regions.
 
 	A <dfn export for=property lt="scoped | scoped property | scoped properties">scoped property</dfn> has its effects scoped to a particular element or subtree.
@@ -289,22 +302,26 @@ Style Containment</h3>
 	When scoped, the 'counter-set' and 'counter-increment' <a spec=css-lists-3>create a new counter</a>.
 
 	<div class=example>
-	If 'counter-increment' is scoped to an element's subtree,
+	As 'counter-increment' is scoped to an element's subtree,
 	the first use of it within the subtree acts as if the named counter were set to 0 at the scoping element,
 	regardless of whether the counter had been used outside the scoping element.
 	Any increments made within the subtree have no effect on counters of the same name outside the scoping element.
-	Therefore, the following code results in <code>1.2</code> being displayed:
+	However, the ''content/counter()'' and ''content/counters()'' value of the 'content' property is not itself scoped,
+	and can refer to counters established outside of the subtree.
+	Therefore, the following code results in <q><samp>1 1.2</samp></q> being displayed:
 	<pre><code highlight=markup>
 	&lt;div>&lt;/div>
 	</code></pre>
 	<pre><code highlight=css>
 	div {
 		contain: style;
-		counter-increment: n;
+		 counter-increment: n;
+	}
+	div::before, div::after {
+		content: counters(n, '.') " ";
 	}
-	div::before {
+	div::after {
 		counter-increment: n 2;
-		content: counters(n, '.');
 	}
 	</code></pre>
 	</div>
@@ -457,6 +474,7 @@ This appendix is <em>informative</em>.
 	<li>Elements with size containment are monolithic
 	<li>Forced breaks area allowed in elements with layout containments, but do not propagate
 	<li>Clarify the effects of scoping to a subtree
+	<li>Clarify the effects of scoping on counters
 </ul>
 
 <h3 id="2017-04-19-changes">Changes from the

css-contain-1/issues-2017-cr.html

@@ -97,14 +97,15 @@ <h1>CSS Contain Level 1 Disposition of Comments for 2017-02-21 WD</h1>
 Response: <a href='https://github.com/w3c/csswg-drafts/issues/1887#issuecomment-342335347'>https://github.com/w3c/csswg-drafts/issues/1887#issuecomment-342335347</a>
 Closed:   Accepted
 Resolved: <a href='https://github.com/w3c/csswg-drafts/issues/1887#issuecomment-342335347'>https://github.com/w3c/csswg-drafts/issues/1887#issuecomment-342335347</a></pre>
-<pre class=' open' id='issue-8'>
+<pre class='a' id='issue-8'>
 Issue 8. <a href='#issue-8'>#</a>
 Summary:  Scoping of the content property unclear
 From:     Oriol Brufau
 Comment:  <a href='https://github.com/w3c/csswg-drafts/issues/2483'>https://github.com/w3c/csswg-drafts/issues/2483</a>
 Comment:  <a href='https://github.com/w3c/csswg-drafts/issues/2483#issuecomment-377214307'>https://github.com/w3c/csswg-drafts/issues/2483#issuecomment-377214307</a>
 Response: <a href='https://github.com/w3c/csswg-drafts/issues/2483#issuecomment-379124749'>https://github.com/w3c/csswg-drafts/issues/2483#issuecomment-379124749</a>
-Open</pre>
+Closed:   Accepted
+Resolved: <a href='https://github.com/w3c/csswg-drafts/issues/2483#issuecomment-380360855'>https://github.com/w3c/csswg-drafts/issues/2483#issuecomment-380360855</a></pre>
 <pre class='a' id='issue-9'>
 Issue 9. <a href='#issue-9'>#</a>
 Summary:  Clarify style containment property scopment

css-contain-1/issues-2017-cr.txt

@@ -74,7 +74,8 @@ From:     Oriol Brufau
 Comment:  https://github.com/w3c/csswg-drafts/issues/2483
 Comment:  https://github.com/w3c/csswg-drafts/issues/2483#issuecomment-377214307
 Response: https://github.com/w3c/csswg-drafts/issues/2483#issuecomment-379124749
-Open
+Closed:   Accepted
+Resolved: https://github.com/w3c/csswg-drafts/issues/2483#issuecomment-380360855
 ----
 Issue 9.
 Summary:  Clarify style containment property scopment