[mediaqueries-5] Remove prefers-contrast:forced

See #5433

Author: frivoal

mediaqueries-5/Overview.bs

@@ -2633,12 +2633,12 @@ Detecting the desire for reduced transparency on the page: the 'prefers-reduced-
 	ISSUE: How does this interact with preferences around e.g. pattern fills and backgrounds?
 	They're not about transparency, but they also interfere with shape recognition.
 
-<h3 id="prefers-contrast" oldids="forced-colors">
+<h3 id="prefers-contrast">
 Detecting the desire for increased or decreased color contrast from elements on the page: the 'prefers-contrast' feature</h3>
 
 	<pre class='descdef mq'>
 	Name: prefers-contrast
-	Value: no-preference | less | more | forced
+	Value: no-preference | less | more
 	For: @media
 	Type: discrete
 	</pre>
@@ -2666,37 +2666,6 @@ Detecting the desire for increased or decreased color contrast from elements on
 		<dd>
 			Indicates that user has notified the system that they
 			prefer an interface that has a higher level of contrast.
-
-		<dt><dfn>forced</dfn>
-		<dd>
-			Indicates that <a>forced colors mode</a> is active:
-			the user agent enforces a user-chosen limited color palette on the page,
-			in effect also implying a strong preference for the associated contrast.
-			The UA will provide the color palette to authors
-			through the CSS system color keywords.
-			See [[css-color-adjust-1#forced]] for details.
-
-			<div class=advisement>
-				This does <em>not</em> necessarily indicate
-				a preference for more contrast.
-				The colors have been forcibly adjusted
-				to match the preference of the user,
-				but that preference can be for less or more contrast,
-				or some other arrangement that is neither particularly low or high contrast.
-			</div>
-
-			Additionally, when the user agent can determine
-			whether the forced color palette chosen by the user
-			has a high or low contrast,
-			one of ''prefers-contrast: more'' or ''prefers-contrast: less'' must match
-			in addition to ''prefers-contrast: forced''.
-
-			Note:
-			Similarly,
-			if the forced color palette chosen by the user
-			fits within one of the color schemes described by 'prefers-color-scheme',
-			the corresponding value will also match.
-			See [[css-color-adjust-1#forced]] for details.
 	</dl>
 
 	<div class=note>
@@ -2715,11 +2684,7 @@ Detecting the desire for increased or decreased color contrast from elements on
 		to do things like replacing background images with plain colors,
 		turning off decorative gradients,
 		or replacing border images or box shadows with simple solid borders.
-		As ''prefers-contrast/forced'', like ''prefers-contrast/more'' or ''prefers-contrast/less'',
-		evaluates to true in a [=boolean context=],
-		this syntax also benefits users of <a>forced colors mode</a>,
-		even when it isn't know whether their colors of choice
-		result in a high or low contrast (or something else).
+		See also [[#forced-colors]].
 	</div>
 
 	<div class=example>
@@ -2753,8 +2718,8 @@ Detecting the desire for increased or decreased color contrast from elements on
 		Issue: This list should be refined and expanded.
 	</div>
 
-	For compatibility with legacy content,
-	the following syntax is also supported:
+<h3 id="forced-colors">
+Detecting Forced Colors Mode: the 'forced-colors' feature</h3>
 
 	<pre class='descdef mq'>
 	Name: forced-colors
@@ -2763,9 +2728,60 @@ Detecting the desire for increased or decreased color contrast from elements on
 	Type: discrete
 	</pre>
 
-	<dfn type=value dfn-for="@media/prefers-color-scheme" export>active</dfn> matches
-	when ''prefers-contrast: forced'' matches,
-	otherwise <dfn type=value dfn-for="@media/prefers-color-scheme" export>none</dfn> matches.
+	<dl dfn-type=value dfn-for="@media/forced-colors">
+		<dt><dfn>active</dfn>
+		<dd>
+			Indicates that <a>forced colors mode</a> is active:
+			the user agent enforces a user-chosen limited color palette on the page,
+			The UA will provide the color palette to authors
+			through the CSS system color keywords.
+			See [[css-color-adjust-1#forced]] for details.
+
+			<div class=advisement>
+				This does <em>not</em> necessarily indicate
+				a preference for more contrast.
+				The colors have been forcibly adjusted
+				to match the preference of the user,
+				but that preference can be for less or more contrast,
+				or some other arrangement that is neither particularly low or high contrast.
+			</div>
+
+			Additionally, when the user agent can determine
+			whether the forced color palette chosen by the user
+			has a high or low contrast,
+			one of ''prefers-contrast: more'' or ''prefers-contrast: less'' must match
+			in addition to ''forced-colors: active''.
+
+			Similarly,
+			if the forced color palette chosen by the user
+			fits within one of the color schemes described by 'prefers-color-scheme',
+			the corresponding value must also match.
+			See [[css-color-adjust-1#forced]] for details.
+
+		<dt><dfn>none</dfn>
+		<dd>
+			[=Forced colors mode=] is not active.
+	</dl>
+
+	<div class=example>
+		When [=forced colors mode=] is active,
+		the only colors that are available to the author are [=system colors=].
+		The user agent will enforce this limited palette automatically,
+		but the author may choose a different way of using these colors,
+		using the ''forced-colors'' media feature to detect when it is appropriate to do so.
+	</div>
+
+	<div class=example>
+		The reduced palette enforeced by [=forced colors mode=]
+		can call for some visual simplification of the page.
+		''@media (forced-colors) or (prefers-contrast) { … }''
+		can thus be a useful query to conditionally apply styles that reduce visual clutter,
+		catching all users of forced colors and all users with contrast preferences.
+		''@media (prefers-contrast) { … }'' would leave how forced-colors users
+		with a color scheme that is neither particularly hight nor low contrast.
+		while ''@media (forced-colors) { … }'' would instead leave out users with contrast preferences
+		that do not come from usage of [=forced colors mode=].
+	</div>
 
 <h3 id="prefers-color-scheme">
 Detecting the desire for light or dark color schemes: the 'prefers-color-scheme' feature</h3>