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[css-color-4] Add new set of CSS system colors (addresses w3c#3804)
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Melanie Richards committed Jul 5, 2019
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Expand Up @@ -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.
Expand Down Expand Up @@ -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,
Expand Down Expand Up @@ -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>

Expand Down Expand Up @@ -2332,6 +2383,7 @@ Converting Between Uncalibrated CMYK and RGB-Based Colors</h3>
<li>fallback color must be set to the input color
</ul>


<h2 id="transparency">
Transparency: the 'opacity' property</h2>

Expand Down Expand Up @@ -2759,12 +2811,10 @@ 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),
Expand All @@ -2790,10 +2840,6 @@ 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.
Expand All @@ -2802,22 +2848,9 @@ 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.

Expand Down Expand Up @@ -2891,6 +2924,7 @@ 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>
Expand Down Expand Up @@ -2968,13 +3002,9 @@ 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 UI that appears to be from the system.

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