[css-color-4] Add new set of CSS system colors (addresses #3804)

Author: Melanie Richards

css-color-4/Overview.bs

@@ -129,7 +129,7 @@ Representing sRGB Colors: the <<color>> type</h2>
 	<dfn>&lt;color></dfn> = <<rgb()>> | <<rgba()>> | <<hsl()>> | <<hsla()>> |
 	          <<hwb()>> | <<gray()>> | <<device-cmyk()>> |
 	          <<hex-color>> | <<named-color>> | currentcolor |
-	          <<deprecated-system-color>>
+	          <<system-color>>
 	</pre>
 
 	Some operations work differently on <dfn export>achromatic</dfn> colors.
@@ -209,7 +209,7 @@ Resolving Color values</h2>
 
 		<li>
 		The computed value and used value of
-		<a>named colors</a> (including <<deprecated-system-color>> colors),
+		<a>named colors</a> (including <<system-color>> colors),
 		3 and 6 digits <a>hex colors</a>,
 		4 and 8 digits <a>hex colors</a> with an explicitly opaque alpha channel,
 		comma separated ''rgb()'' colors without an alpha channel,
@@ -704,6 +704,57 @@ Named Colors</h2>
 	Note: this list of colors and their definitions is a superset of the list of <a href="https://www.w3.org/TR/SVG/types.html#ColorKeywords">named colors defined by SVG 1.1</a>.
 For historical reasons, this is also referred to as the X11 color set.
 
+
+<h3 id="css-system-colors">
+CSS System Colors</h3>
+
+	In addition to being able to assign color keyword values to text, backgrounds, etc., 
+	CSS defines a set of <dfn id="system-color" lt="system colors" export>&lt;system color></dfn> values, 
+	to allow authors to specify colors in a manner that integrate them into the user's graphic environment.
+
+	<<system-color>>s incur some privacy and security risk, as detailed in [[#priv-sec]].
+
+	For systems that do not have a corresponding value, 
+	the specified value should be mapped to the nearest system color value, 
+	or to a default color. 
+	Note that some profiles of CSS may not support System Colors at all.
+
+	The following lists the additional values for color-related CSS values and their general meaning. 
+	Any color property can take one of the following names. 
+	These names are case-insensitive and shown here with mixed capitalization for legibility.
+
+	<dl id="system-color-values" data-dfn-type="value" dfn-for="<system-color>" export>
+		<dt><dfn>ActiveText</dfn>
+		<dd>Text in active links.
+		<dt><dfn>ButtonFace</dfn>
+		<dd>The face background color for push buttons.
+		<dt><dfn>ButtonText</dfn>
+		<dd>Text on push buttons.
+		<dt><dfn>Canvas</dfn>
+		<dd>Background of application content or documents.
+		<dt><dfn>Field</dfn>
+		<dd>Background of input fields.
+		<dt><dfn>FieldText</dfn>
+		<dd>Text in input fields.
+		<dt><dfn>GrayText</dfn>
+		<dd>Grayed (disabled) text. This color is set to #000 if the current display driver does not support a solid gray color.
+		<dt><dfn>Highlight</dfn>
+		<dd>Background of item(s) selected in a control.
+		<dt><dfn>HighlightText</dfn>
+		<dd>Text of item(s) selected in a control.
+		<dt><dfn>LinkText</dfn>
+		<dd>Text in non-active, non-visited links.
+		<dt><dfn>Text</dfn>
+		<dd>Text in application content or documents.
+		<dt><dfn>VisitedText</dfn>
+		<dd>Text in visited links.
+	</dl>
+
+	Earlier versions of CSS defined additional <<system color>>s,
+	which have since been deprecated.
+	These are documented in [[#deprecated-system-colors]].
+
+
 <h3 id='transparent-color'>
 The ''transparent'' keyword</h3>
 
@@ -2759,12 +2810,10 @@ Default Style Rules</h2>
 
 </pre>
 
-<h2 id="system-colors" class="no-num">
+<h2 id="deprecated-system-colors" class="no-num">
 Appendix A: Deprecated CSS System Colors</h2>
 
-	Earlier versions of CSS defined several additional named color keywords,
-	the <dfn>&lt;deprecated-system-color></dfn>s,
-	which were meant to take their value from operating system themes.
+	Earlier versions of CSS defined several additional <<system-color>>s.
 	These color names have been <strong>deprecated</strong>, however,
 	as they are insufficient for their original purpose
 	(making website elements look like their native OS counterparts),
@@ -2790,10 +2839,6 @@ Appendix A: Deprecated CSS System Colors</h2>
 		<dt><dfn>Background</dfn>
 		<dd>Desktop background.
 
-		<dt><dfn>ButtonFace</dfn>
-		<dd>The face background color for 3-D elements that appear 3-D due to
-		one layer of surrounding border.
-
 		<dt><dfn>ButtonHighlight</dfn>
 		<dd>The color of the border facing the light source for 3-D elements
 		that appear 3-D due to one layer of surrounding border.
@@ -2802,22 +2847,9 @@ Appendix A: Deprecated CSS System Colors</h2>
 		<dd>The color of the border away from the light source for 3-D elements
 		that appear 3-D due to one layer of surrounding border.
 
-		<dt><dfn>ButtonText</dfn>
-		<dd>Text on push buttons.
-
 		<dt><dfn>CaptionText</dfn>
 		<dd>Text in caption, size box, and scrollbar arrow box.
 
-		<dt><dfn>GrayText</dfn>
-		<dd>Grayed (disabled) text. This color is set to #000 if
-		the current display driver does not support a solid gray color.
-
-		<dt><dfn>Highlight</dfn>
-		<dd>Item(s) selected in a control.
-
-		<dt><dfn>HighlightText</dfn>
-		<dd>Text of item(s) selected in a control.
-
 		<dt><dfn>InactiveBorder</dfn>
 		<dd>Inactive window border.
 
@@ -2891,6 +2923,7 @@ Changes</h2>
 <h3 id="changes-from-20160705" class='no-num'>Changes since <a href="http://www.w3.org/TR/2016/WD-css-color-4-20160705/">Working Draft of 05 July 2016</a></h3>
 
 <ul>
+	<li>Add new list of CSS system colors</li>
 	<li>Initial value of the "color" property is now black</li>
 	<li>Clarify hue in LCH is modulo 360deg</li>
 	<li>Clarify allowed range of L in LCH and Lab, and meaning of L=100</li>
@@ -2968,13 +3001,11 @@ Security and Privacy Considerations {#priv-sec}
 This specification defines "system" colors,
 which theoretically can expose details of the user's OS settings,
 which is a fingerprinting risk.
-However, these values are now defined to be settings-neutral,
-and should be implemented in a generic way that does not actually expose system colors.
 
 The system colors,
 if they actually correspond to the user's system colors,
 also pose a security risk,
 as they make it easier for a malware site
-to create a dialog that appears to be a system dialog.
-However, as they are now defined to be "generic",
-this risk should be eliminated.
+to create user interfaces that appear to be from the system.
+However, as several system colors are now defined to be "generic", 
+this risk should be mitigated.