[css-break-3] Clarify that margins adjoining Class C breaks are also truncated. #3073

Author: fantasai

css-break-3/Overview.bs

@@ -941,14 +941,16 @@ Breaking into Varying-size Fragmentainers</h3>
 Adjoining Margins at Breaks</h3>
 
   <p>
-    When an unforced break occurs between block-level boxes,
-    any margins adjoining the break truncate to the <a>remaining fragmentainer extent</a> before the break,
-    and are truncated to zero after the break.
+    When an unforced break occurs before or after a block-level box,
+    any margins adjoining the break are truncated to zero.
     When a forced break occurs there, adjoining margins before the break are truncated,
     but margins after the break are preserved.
-    <a href="#valdef-box-decoration-break-clone">Cloned margins</a> are always truncated to zero on block-level margins.
+    <a href="#valdef-box-decoration-break-clone">Cloned margins</a> are always
+    truncated to zero on block-level boxes.
   </p>
 
+  Note: CSS Fragmentation Level 4 will introduce control over margin truncation at breaks.
+
 <h3 id="box-splitting">
 Splitting Boxes</h3>
 
@@ -1177,6 +1179,7 @@ Changes</h2>
       <blockquote>
         <p>by treating the 'page-break-*' properties as <del>shorthands</del> <ins>[=legacy shorthands=]</ins> for the 'break-*' properties
       </blockquote>
+
     <li id="change-2017-propagation">
       Clarified that break propagation does not affect computed values
       and that other layout modes (e.g. flex and grid) make adjustments
@@ -1193,6 +1196,18 @@ Changes</h2>
         <p>Applies to: block containers <ins>that establish a new inline formatting context</ins>
       </blockquote>
 
+    <li id="change-2018-truncate-margins">
+      Clarified that margins adjoining a Class C break are also truncated
+      in the same way as margins between siblings (Class A).
+      (<a href="https://github.com/w3c/csswg-drafts/issues/3073">Issue 3073</a>)
+      <blockquote>
+        <p>
+          When an unforced break occurs <del>between</del> <ins>before or after a</a> block-level box<del>es</del>,
+          any margins adjoining the break <del>truncate to the <a>remaining fragmentainer extent</a> before the break,
+          and</del> are truncated to zero <del>after the break</del>.
+        </p>
+      </blockquote>
+
     <li id="change-2017-inline-block-fragmentation">
       Clarified what it means if a UA chooses not to treat atomic inlines as not <a>monolithic</a>.
       (<a href="https://github.com/w3c/csswg-drafts/issues/1111">Issue 1111</a>)