[css-containment] Interaction between containment and fragmentation

Closes w3c#2527

Author: frivoal

css-contain-1/Overview.bs

@@ -180,6 +180,7 @@ Size Containment</h3>
 		its contents must then be laid out into the containing element's resolved size.
 
 		<a>Replaced elements</a> must be treated as having an intrinsic width and height of 0.
+	2. Elements with <a>size containment</a> are <a spec=css-break-3>monolithic</a> (See [[CSS-BREAK-3#possible-breaks]]).
 
 	By itself, <a>size containment</a> does not offer much optimization opportunity.
 	Its primary benefit on its own is that tools which want to lay out the containing element's contents
@@ -239,6 +240,12 @@ Layout Containment</h3>
 
 	4. The element acts as a containing block for absolutely positioned and fixed positioned descendants.
 
+	5. [=Forced breaks=] are allowed within elements with [=layout containment=],
+		but do not propagate to the parent as otherwise described in [[CSS-BREAK-3#break-between]].
+
+		Note: This introduces the previously non-existent possibility that [=forced breaks=]]
+		may occur between a box and its container (See [[CSS-BREAK-3#possible-breaks]].
+
 	Possible optimizations that can be enabled by <a>layout containment</a> include (but are not limited to):
 
 	1. When laying out the page,
@@ -444,6 +451,8 @@ This appendix is <em>informative</em>.
 	<li>Size layout and paint containment don't apply to internal ruby elements
 	<li>Size containment does not apply to non-atomic inlines
 	<li>Align paint containment's behavior with overflow:clip
+	<li>Elements with size containment are monolithic
+	<li>Forced breaks area allowed in elements with layout containments, but do not propagate
 </ul>
 
 <h3 id="2017-04-19-changes">Changes from the

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

@@ -169,13 +169,14 @@ <h1>CSS Contain Level 1 Disposition of Comments for 2017-02-21 WD</h1>
 Comment:  <a href='https://github.com/w3c/csswg-drafts/issues/1758'>https://github.com/w3c/csswg-drafts/issues/1758</a>
 Closed:   Accepted
 Resolved: Editorial</pre>
-<pre class=' open' id='issue-16'>
+<pre class='a' id='issue-16'>
 Issue 16. <a href='#issue-16'>#</a>
 Summary:  Interaction between containment and fragmentation
 From:     David Baron
 Comment:  <a href='https://github.com/w3c/csswg-drafts/issues/2527'>https://github.com/w3c/csswg-drafts/issues/2527</a>
 Response: <a href='https://github.com/w3c/csswg-drafts/issues/2527#issuecomment-380379157'>https://github.com/w3c/csswg-drafts/issues/2527#issuecomment-380379157</a>
-Open</pre>
+Closed: Accepted
+Resolved: <a href='https://github.com/w3c/csswg-drafts/issues/2527#issuecomment-380827863'>https://github.com/w3c/csswg-drafts/issues/2527#issuecomment-380827863</a></pre>
 <script>
 (function () {
     var sheet = document.styleSheets[0];

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

@@ -145,4 +145,5 @@ Summary:  Interaction between containment and fragmentation
 From:     David Baron
 Comment:  https://github.com/w3c/csswg-drafts/issues/2527
 Response: https://github.com/w3c/csswg-drafts/issues/2527#issuecomment-380379157
-Open
+Closed: Accepted
+Resolved: https://github.com/w3c/csswg-drafts/issues/2527#issuecomment-380827863