[css-anchor-position-1] Fallbacks are based only on changes in base style (ignoring animations/transitions). #13048

Author: tabatkins

css-anchor-position-1/Overview.bs

@@ -1936,7 +1936,8 @@ This limit must be <em>at least</em> five.
 <div algorithm="determine position fallback styles">
 	To <dfn>determine position fallback styles</dfn> for an element |abspos|:
 
-	1. Let |current styles| be the current used styles of |abspos|
+	1. Let |current styles| be the current used styles of |abspos|,
+		as derived from the [=computed base style=]
 		(which might be the result of earlier fallback).
 
 	2. [=list/For each=] |option| in the [=position options list=]:
@@ -2014,6 +2015,10 @@ and thus trigger special behavior. These <dfn>fallback-sensitive changes</dfn> i
 	* Any of the ''@position-try'' rules referenced by it
 		have been added, removed, or mutated.
 
+	For this purpose, only changes to the <dfn>computed base style</dfn> are considered,
+	i.e. the [=computed style=] ignoring any declarations originating
+	from the Transitions or Animations [=cascade origins=].
+
 <h5 id="last-successful-recording">
 Recording the [=last successful position option=]</h5>
 
@@ -2042,33 +2047,6 @@ which is determined as follows:
 	is intentionally identical to the treatment of [=last remembered sizes=].
 </div>
 
-ISSUE(13048): The following sections attempt to clarify the interaction with transitions and animations.
-
-<h5 id="suspending-fallback-transitions">
-Suspending Fallback During Transitions</h5>
-
-The UA must [=determine position fallback styles=]
-for both the start and end states of a [=transition=]
-(see [[CSS-TRANSITIONS-1]])
-that includes properties that could cause a [=fallback-sensitive change=].
-
-During a [=transition=] for properties that could cause a [=fallback-sensitive change=], however,
-[=determining position fallback styles=] and
-[=recording the last successful position option=] are suspended.
-
-<h5 id="suspending-fallback-animations">
-Suspending Fallback During Animations</h5>
-
-If an [=animation=] (see [[CSS-ANIMATIONS-1]] and [[WEB-ANIMATIONS-1]])
-affects any properties that could cause a [=fallback-sensitive change=],
-then the UA must [=determine position fallback styles=]
-for the keyframes that contain those properties (only).
-As fallback determination is order-sensitive,
-later keyframes must take into account the result of earlier keyframes.
-
-While animating between these keyframes, however,
-[=determining position fallback styles=] and
-[=recording the last successful position option=] are suspended.
 
 <h4 id="applying-options">
 Applying Position Options</h4>