[css-color-4] a,b,C,h powerless if L=100%, fix w3c#7924

Author: Chris Lilley

css-color-4/Overview.bs

@@ -3074,18 +3074,13 @@ Specifying Lab and LCH: the ''lab()'' and ''lch()'' functional notations</h3>
 	</wpt>
 
 	The first argument specifies the CIE Lightness.
-	This is typically a number between ''0%''
+	This is a number between ''0%''
 	(representing black)
 	and ''100%''
 	(representing white),
-	<!-- not really true, as noted above
-		similar to the lightness argument of ''hsl()''. -->
-	However, CIE Lightness <em>can</em> exceed this range on some systems,
-	with extra-bright whites using a lightness up to ''400''.
 	Values less than ''0%'' must be clamped to ''0%'' at computed-value time;
 	values greater than
-	''100%'' are permitted (for forwards compatibility with High Dynamic Range (HDR),
-	and must not be clamped.
+	''100%'' are clamped to ''100%''.
 
 	The second and third arguments are the distances along the "a" and "b" axes
 	in the Lab color space,
@@ -3100,9 +3095,9 @@ Specifying Lab and LCH: the ''lab()'' and ''lch()'' functional notations</h3>
 	representing the [=alpha component=].
 
 	If the lightness of a Lab color is ''0%'',
-	both the a and b components are [=powerless=].
-
-	Issue: Unsure about when/if a and b become powerless for Lab whites.
+	or ''100%''
+	both the a and b components are [=powerless=]
+	and the color represents black, or white, respectively.
 
 	<div class="example" id="ex-lab-samples">
 		<pre class="lang-css">
@@ -3178,10 +3173,9 @@ Specifying Lab and LCH: the ''lab()'' and ''lch()'' functional notations</h3>
 	If the chroma of an LCH color is ''0%'',
 	the hue component is [=powerless=].
 	If the lightness of an LCH color is ''0%'',
+	or ''100%'', 
 	both the hue and chroma components are [=powerless=].
 
-	Issue: Unsure about when/if hue and chroma become powerless for LCH whites.
-
 	<div class="example" id="ex-lch-samples">
 		<pre class="lang-css">
 			<span class="swatch" style="--color: rgb(49.06% 13.87% 15.9%)"></span> lch(29.2345% 44.2 27);
@@ -3239,16 +3233,14 @@ Specifying Lab and LCH: the ''lab()'' and ''lch()'' functional notations</h3>
 	</wpt>
 
 	The first argument specifies the Oklab Lightness.
-	This is typically a number between ''0%''
+	This is a number between ''0%''
 	(representing black)
 	and ''100%''
 	(representing white).
 
 	Values less than ''0%'' must be clamped to ''0%''
 	at computed-value time;
-	values greater than ''100%'' are permitted
-	for forwards compatibility,
-	and must not be clamped.
+	values greater than ''100%'' are clamped to ''100%''.
 
 	The second and third arguments are the distances along
 	the "a" and "b" axes
@@ -3264,7 +3256,9 @@ Specifying Lab and LCH: the ''lab()'' and ''lch()'' functional notations</h3>
 	representing the [=alpha component=].
 
 	If the lightness of an Oklab color is ''0%'',
-	both the a and b components are [=powerless=].
+	or ''100%'',
+	both the a and b components are [=powerless=]
+	and the color represents black, or white, respectively.
 
 	<div class="example" id="ex-oklab-samples">
 		<pre class="lang-css">
@@ -3339,6 +3333,7 @@ Specifying Lab and LCH: the ''lab()'' and ''lch()'' functional notations</h3>
 		If the chroma of an Oklch color is ''0%'',
 		the hue component is [=powerless=].
 		If the lightness of an Oklch color is ''0%'',
+		or ''100%'',
 		both the hue and chroma components are [=powerless=].