[css3-grid-layout] Draft ideas for abspos grid children.

Author: tabatkins

css3-grid-layout/Overview.html

@@ -1140,6 +1140,50 @@ <h3 id=non-children-grid-items><span class=secno>4.1. </span>Non-children
   <h3 id=absolutely-positioned-grid-children><span class=secno>4.2.
    </span>Absolutely Positioned Grid Children</h3>
 
+  <p> An absolutely-positioned child element of a <a
+   href="#grid-container"><i>grid container</i></a> does not participate
+   directly in grid layout. Its static position is ???
+
+  <div class=issue>
+   <ul>
+    <li>The before/start corner of the grid container? (In this case, should
+     we adjust Flexbox to match?)
+
+    <li>The before/start edge of the cell it would be placed in, if it were a
+     1x1 auto-placed grid item? (Don't let it generate new rows/columns,
+     though, which complicates things.) (This is closer to Flexbox's current
+     behavior.)
+   </ul>
+  </div>
+
+  <p class=issue> Below is a proposal for how to deal with abspos in grid
+   containers. It gives us many of the capabilities of [[CSS3-GRID]].
+
+  <p> If an absolutely positioned element's <i>containing block</i> is
+   generated by a <a href="#grid-container"><i>grid container</i></a>, the <a
+   href="#grid-placement-properties"><i>grid-placement properties</i></a> can
+   be used to constrain it to a particular <a href="#grid-area"><i>grid
+   area</i></a>, similar to how they affect regular <a
+   href="#grid-item"><i>grid items</i></a>. In this case, an ‘<a
+   href="#track-size-auto"><code class=css>auto</code></a>’ value for a <a
+   href="#grid-placement-properties"><i>grid-placement property</i></a>
+   indicates ...
+
+  <div class=issue>
+   <ul>
+    <li>the padding edge of the <a href="#grid-container"><i>grid
+     container</i></a> (as normal for abspos)
+
+    <li>the next/previous grid line (as normal for grid items with one ‘<a
+     href="#track-size-auto"><code class=css>auto</code></a>’ value in a
+     dimension, as it resolves to ‘<code class=css>span 1</code>’)
+   </ul>
+  </div>
+
+  <p class=note> This can allow an abspos to "skip past" intervening grid
+   containers, and resolve its grid-placement properties against a grid
+   container other than its closest ancestor.
+
   <h3 id=collapsed-grid-items><span class=secno>4.3. </span>Collapsed Grid
    Items</h3>
 

css3-grid-layout/Overview.src.html

@@ -807,6 +807,43 @@ <h3>Non-children Grid Items</h3>
 
 <h3>Absolutely Positioned Grid Children</h3>
 
+	<p>
+		An absolutely-positioned child element of a <i>grid container</i> does not participate directly in grid layout.
+		Its static position is ???
+
+	<div class='issue'>
+		<ul>
+			<li>The before/start corner of the grid container?
+				(In this case, should we adjust Flexbox to match?)
+			<li>The before/start edge of the cell it would be placed in, if it were a 1x1 auto-placed grid item? 
+				(Don't let it generate new rows/columns, though, which complicates things.)
+				(This is closer to Flexbox's current behavior.)
+		</ul>
+	</div>
+
+	<p class='issue'>
+		Below is a proposal for how to deal with abspos in grid containers.
+		It gives us many of the capabilities of [[CSS3-GRID]].
+
+	<p>
+		If an absolutely positioned element's <i>containing block</i>
+		is generated by a <i>grid container</i>,
+		the <i>grid-placement properties</i> can be used to constrain it to a particular <i>grid area</i>,
+		similar to how they affect regular <i>grid items</i>.
+		In this case, an ''auto'' value for a <i>grid-placement property</i> indicates ...
+
+	<div class="issue">
+		<ul>
+			<li>the padding edge of the <i>grid container</i> (as normal for abspos)
+			<li>the next/previous grid line (as normal for grid items with one ''auto'' value in a dimension, as it resolves to 'span 1')
+		</ul>
+	</div>
+
+	<p class='note'>
+		This can allow an abspos to "skip past" intervening grid containers,
+		and resolve its grid-placement properties against a grid container
+		other than its closest ancestor.
+
 <h3>Collapsed Grid Items</h3>
 
 	<p class='issue'>