[css-scroll-snap] Fold in scope-snapping-to-visible-area section per WG resolution. Tweak wording to try to make it clearer.

Author: fantasai

css-scroll-snap/Overview.bs

@@ -498,18 +498,15 @@ Scroll Snapping Alignment: the 'scroll-snap-align' property {#scroll-snap-align}
 <h4 id="snap-scope">
 Scoping Valid Snap Positions to Visible Boxes</h4>
 
-<div class="issue">
-    <strong>Need to define that a box is not <a>snapped</a> if it is off-screen,
-    even if its snap alignment is satisfied in the other axis.</strong>
-
     Since the purpose of scroll snapping is to align content within the viewport
-    for optimal viewing:
-    in all cases, the specified alignment creates a valid <a>snap position</a>
-    only if at least part of the <a>snap area</a> is within the <a>snapport</a>.
+    for optimal viewing,
+    a <a>scroll container</a> cannot be <a>snapped</a> to a <a>snap area</a>
+    if no part of it is within the <a>snapport</a>.
     For example, a <a>snap area</a> is top-aligned to the <a>snapport</a>
     if its top edge is coincident with the <a>snapport</a>’s top edge;
-    however, this alignment is nonetheless not a valid <a>snap position</a>
-    if the entire <a>snap area</a> is outside the <a>snapport</a>.
+    however, this scroll position is nonetheless not a valid <a>snap position</a>
+    if the entire <a>snap area</a> is outside the <a>snapport</a>
+    (because the required alignment, though satisfied, would not be relevant to the viewer).
 
     <figure>
         <pre class="ascii-art">
@@ -536,7 +533,7 @@ Scoping Valid Snap Positions to Visible Boxes</h4>
         with on-screen elements.
         (If this requirement is onerous for implementers however,
         we can default to a gridded behavior
-        and introduce a switch to get smarter behavior.)
+        and introduce a switch to get smarter behavior later.)
     </details>
 </div>