[css4-images] Add some issues to element().

Author: tabatkins

css4-images/Overview.html

@@ -918,6 +918,9 @@ <h3 id=element-notation><span class=secno>3.4. </span> Using Elements as
    as a background-image on the element or in a pseudo-element. This needs to
    be specially-handled to avoid triggering the cycle-detection.
 
+  <p class=issue> When we have overflow:paged, how can we address a single
+   page in the view?
+
   <p> The ‘<code class=css>element()</code>’ function references the
    element matched by its argument. If multiple elements are matched, the
    function references the first such element.
@@ -958,6 +961,12 @@ <h3 id=element-notation><span class=secno>3.4. </span> Using Elements as
      so that the edges of the <a href="#decorated-bounding-box"><i>decorated
      bounding box</i></a> are flush with the edges of the image.
 
+    <p class=issue> Requiring some degree of stacking context on the element
+     appears to be required for an efficient implementation. Do we need a
+     full stacking context, or just a pseudo-stacking context? Should it need
+     to be a stacking context normally, or can we just render it as a
+     stacking context when rendering it to element()?
+
     <p> If the referenced element has a transform applied to it or an
      ancestor, the transform must be ignored when rendering the element as an
      image. [[!CSS-TRANSFORMS]]

css4-images/Overview.src.html

@@ -648,6 +648,10 @@ <h3 id='element-notation'>
 		either as a background-image on the element or in a pseudo-element.
 		This needs to be specially-handled to avoid triggering the cycle-detection.
 
+	<p class='issue'>
+		When we have overflow:paged,
+		how can we address a single page in the view?
+
 	<p>
 		The ''element()'' function references the element matched by its argument.  
 		If multiple elements are matched, 
@@ -685,6 +689,12 @@ <h3 id='element-notation'>
 				over an infinite ''transparent'' canvas, 
 				positioned so that the edges of the <i>decorated bounding box</i> are flush with the edges of the image.
 
+			<p class='issue'>
+				Requiring some degree of stacking context on the element appears to be required for an efficient implementation.
+				Do we need a full stacking context, or just a pseudo-stacking context?
+				Should it need to be a stacking context normally,
+				or can we just render it as a stacking context when rendering it to element()?
+
 			<p>
 				If the referenced element has a transform applied to it or an ancestor, 
 				the transform must be ignored when rendering the element as an image.  [[!CSS-TRANSFORMS]]