[scroll-animations-1] Define 'animation-range' defaulting. #8438

Author: fantasai

scroll-animations-1/Overview.bs

@@ -936,11 +936,41 @@ spec: cssom-view-1; type: dfn;
 	The 'animation-range' property is a [=shorthand property|shorthand=]
 	that sets 'animation-range-start' and 'animation-range-end'
 	together in a single declaration.
-	If a <<timeline-range-name>> alone is specified,
-	'animation-range-start' is set to that name plus ''0%''
-	and 'animation-range-end' is set to that name plus ''100%''.
-	Otherwise, if the <<'animation-range-end'>> value is omitted,
-	it is set to ''animation-range-end/normal''.
+
+	If <<'animation-range-end'>> is omitted
+	and <<'animation-range-start'>> includes a <<timeline-range-name>> component,
+	then 'animation-range-end' is set to that same <<timeline-range-name>> and ''100%''.
+	Otherwise, any omitted [=longhand=] is set to its [=initial value=].
+
+	<div class="example">
+		The following sets of declarations show an 'animation-range' [=shorthand=] declaration
+		followed by its equivalent 'animation-range-start' and 'animation-range-end' declarations:
+		<pre style="columns: 40ch">
+			animation-range: entry 10% exit 90%;
+			animation-range-start: entry 10%;
+			animation-range-end: exit 90%;
+
+			animation-range: entry;
+			animation-range-start: entry 0%;
+			animation-range-end: exit 100%;
+
+			animation-range: 10%;
+			animation-range-start: 10%;
+			animation-range-end: normal;
+
+			animation-range: entry 10% exit;
+			animation-range-start: entry 10%;
+			animation-range-end: exit 100%;
+
+			animation-range: 10% exit 90%;
+			animation-range-start: 10%;
+			animation-range-end: exit 90%;
+
+			animation-range: entry 10% 90%;
+			animation-range-start: entry 10%;
+			animation-range-end: 90%;
+		</pre>
+	</div>
 
 	ISSUE(8438): What's the best way to handle defaulting of omitted values here?
 
@@ -981,6 +1011,8 @@ spec: cssom-view-1; type: dfn;
 			at the specified point on the [=timeline=]
 			measuring from the start of the specified [=named timeline range=],
 			plus any applicable [=start delay=].
+			If the <<length-percentage>> is omitted,
+			it defaults to 0%.
 	</dl>
 
 ### Specifying an Animation’s Timeline Range End: the 'animation-range-end' property ### {#animation-range-end}
@@ -1020,6 +1052,8 @@ spec: cssom-view-1; type: dfn;
 			at the specified point on the [=timeline=]
 			measuring from the start of the specified [=named timeline range=],
 			minus any applicable [=end delay=].
+			If the <<length-percentage>> is omitted,
+			it defaults to 100%.
 	</dl>
 
 ## Reporting Timeline Range Progress: the ''getCurrentTime()'' method ## {#named-range-get-time}