[css-position-3] Merge fixedpos containing block definitions. #5028

Author: fantasai

css-position-3/Overview.bs

@@ -340,15 +340,32 @@ Containing Blocks of Positioned Boxes</h3>
 			with the bounds of the [=containing block=]
 			determined identically to the [=absolute positioning containing block=].
 
-			If no ancestor establishes one,
-			the [=fixed positioning containing block=] is
-			the [=viewport=] in the case of [=continuous media=],
-			or the [=page area=] in the case of [=paged media=].
-			See [[#fixpos-insets]].
-
 			Note: Properties that can cause a box to establish
-			an [=fixed positioning containing block=] include
-			 'transform', 'will-change', 'contain'&hellip;
+			a [=fixed positioning containing block=] include
+			'transform', 'will-change', 'contain'&hellip;
+
+			If no ancestor establishes one,
+			the [=fixed positioning containing block=] is:
+
+			* in <a href="https://www.w3.org/TR/CSS2/media.html#continuous-media-group">continuous media</a>,
+				the <a>viewport</a>;
+				as a result, [=fixed=] boxes do not move when the document is scrolled.
+
+				Note: In this respect, they are similar to
+				[[css-backgrounds-3#the-background-attachment|fixed background images]]
+				(''background-attachment: fixed'').
+
+			* in <a href="https://www.w3.org/TR/CSS2/media.html#paged-media-group">paged media</a>,
+				the [=page area=] of each page;
+				[=fixed positioned=] [=boxes=] are thus replicated on every page.
+				(They are fixed with respect to the page box only,
+				and are not affected by being seen through a [=viewport=];
+				as in the case of print preview, for example.)
+
+			Note: As a result, parts of [=fixed-positioned boxes=]
+			that extend outside the [=initial containing block=]/[=page area=]
+			cannot be scrolled to
+			and will not print.
 	</dl>
 
 <div class="example">
@@ -658,8 +675,8 @@ Scroll Position of Sticky-Positioned Boxes</h4>
 	</div>
 
 
-<h3 id="abspos-insets" oldids="abs-pos">
-Absolute Positioning</h3>
+<h3 id="abspos-insets" oldids="abs-pos,fixed-pos">
+Absolute (and Fixed) Positioning</h3>
 
 	For an [=absolutely positioned=] box,
 	the [=inset properties=] effectively reduce the [=containing block=]
@@ -812,34 +829,6 @@ Fragmenting Absolutely-positioned Elements</h4>
 	Note: User agents might print invisible content in other ways.
 	See [[CSS-PAGE-3#content-outside-box]].
 
-
-<h3 id="fixpos-insets" oldids="fixed-pos">
-Fixed positioning</h3>
-
-	[=Fixed positioning=] is similar to absolute positioning.
-	The only difference is that for a [=fixed positioned=] [=box=],
-	the <a>containing block</a> is:
-
-	* in <a href="https://www.w3.org/TR/CSS2/media.html#continuous-media-group">continuous media</a>,
-		the <a>viewport</a>;
-		as a result, [=fixed=] boxes do not move when the document is scrolled.
-
-		Note: In this respect, they are similar to
-		<a href="https://www.w3.org/TR/CSS2/colors.html#background-properties">fixed background images</a>.
-
-	* in <a href="https://www.w3.org/TR/CSS2/media.html#paged-media-group">paged media</a>,
-		the [=page area=] of each page;
-		[=fixed positioned=] [=boxes=] are thus replicated on every page.
-		(They are fixed with respect to the page box only,
-		and are not affected by being seen through a [=viewport=];
-		as in the case of print preview, for example.)
-
-	As a result, parts of [=fixed-positioned boxes=]
-	that extend outside the <a>initial containing block</a>
-	cannot be scrolled to
-	and will not print.
-
-
 <h2 id="abspos-layout">
 Absolute Positioning Layout Model</h2>