[web-animations-1] Add pseudoElement to getAnimations options (#11050)

* Add pseudoElement to getAnimations, #9908

Author: vmpstr

web-animations-1/Overview.bs

@@ -5631,27 +5631,33 @@ The {{KeyframeEffect}} interface {#the-keyframeeffect-interface}
 
       On setting,
       sets the [=target pseudo-selector=] of the [=animation effect=]
-      to the provided value
-      after applying the following exceptions:
-
-      * If the provided value is not `null`
-          and is an [=invalid selector|invalid=] <<pseudo-element-selector>>,
-          the user agent must [=throw=] a {{DOMException}}
-          with error name "{{SyntaxError}}" and leave the
-          [=target pseudo-selector=] of this [=animation effect=] unchanged.
-
-          Note: Invalid in this context follows the definition of
-          an [=invalid selector=] defined in [[!SELECTORS-4]]
-          such that syntactically invalid pseudo-elements
-          as well as pseudo-elements for which the user agent
-          has no usable level of support
-          are both deemed invalid.
-
-      * If one of the legacy Selectors Level 2 single-colon selectors
-          (':before', ':after', ':first-letter', or ':first-line')
-          is specified,
-          the [=target pseudo-selector=] must be set
-          to the equivalent two-colon selector (e.g. '::before').
+      to the result of <dfn>pseudo-element parsing</dfn> on the provided value,
+      defined as the following:
+
+        1. Given the value |value|, perform the following steps:
+          1. If |value| is not `null`
+               and is an [=invalid selector|invalid=] <<pseudo-element-selector>>,
+
+              1. [=Throw=] a {{DOMException}}
+                  with error name "{{SyntaxError}}".
+
+              1. Abort.
+
+                  Note: In effect, this means that if the result of this algorithm is
+                  used to set a variable, then that variable remains unchanged.
+
+               Note: Invalid in this context follows the definition of
+               an [=invalid selector=] defined in [[!SELECTORS-4]]
+               such that syntactically invalid pseudo-elements
+               as well as pseudo-elements for which the user agent
+               has no usable level of support
+               are both deemed invalid.
+
+          1. If |value| is one of the legacy Selectors Level 2 single-colon selectors
+              (':before', ':after', ':first-letter', or ':first-line'), then
+              return the equivalent two-colon selector (e.g. '::before').
+
+          1. Otherwise, return |value|.
 
   : <dfn>composite</dfn>
   ::
@@ -6652,6 +6658,7 @@ The <code>Animatable</code> interface mixin {#the-animatable-interface-mixin}
 
     dictionary GetAnimationsOptions {
         boolean subtree = false;
+        CSSOMString? pseudoElement = null;
     };
   </xmp>
 
@@ -6733,12 +6740,24 @@ The <code>Animatable</code> interface mixin {#the-animatable-interface-mixin}
 
   : <dfn lt="getAnimations(options)">sequence<Animation> getAnimations(|options|)</dfn>
   ::
-      Returns the set of [=relevant animations=] for this object,
-      or, if an {{Animatable/getAnimations(options)/options}} parameter
-      is passed with {{GetAnimationsOptions/subtree}} set to true,
-      returns the set of [=relevant animations for a subtree=] for this object.
+      1. Let |object| be the object on which this method was called.
+
+      1. Let |pseudoElement| be the result of {{KeyframeEffect/pseudo-element parsing}}
+          applied to {{GetAnimationsOptions/pseudoElement}} of {{Animatable/getAnimations(options)/options}},
+          or `null` if {{Animatable/getAnimations(options)/options}} is not passed.
+
+      1. If |pseudoElement| is not `null`,
+          then let |target| be the [=pseudo-element=]
+          identified by |pseudoElement|
+          with |object| as the originating element.
+          Otherwise, let |target| be |object|.
 
-      The returned list is sorted using
+      1. If {{Animatable/getAnimations(options)/options}} is passed
+          with {{GetAnimationsOptions/subtree}} set to true,
+          then return the set of [=relevant animations for a subtree=] of |target|.
+          Otherwise, return the set of [=relevant animations=] for |target|.
+
+      The list returned by the above algorithm is sorted using
       the composite order described for the associated [=animations=]
       of effects in [[#the-effect-stack]].
 
@@ -6782,6 +6801,12 @@ The <code>Animatable</code> interface mixin {#the-animatable-interface-mixin}
       on which {{Animatable/getAnimations()}} is called
       should also be included in the result.
 
+  : <dfn for=GetAnimationsOptions>pseudoElement</dfn>
+  ::
+      If set, indicates that the target of the operation is the [=pseudo-element=]
+      identified by this pseudo selector (e.g. `::before`)
+      with the originating element being the object on which the function is called.
+
   </div>
 
 Extensions to the {{Document}} interface {#extensions-to-the-document-interface}
@@ -7268,4 +7293,4 @@ Animation of 'box-shadow' and 'text-shadow' {#animating-shadow-lists}
   follows the matching rules for interpolation above,
   performing addition on each component according to its type,
   or falling back to [=discrete=] animation
-  if the ''shadow/inset'' values do not match.
+  if the ''shadow/inset'' values do not match.