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Overview.html
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<!doctype html><html lang="en">
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
<title>CSS High Contrast</title>
<meta content="width=device-width, initial-scale=1, shrink-to-fit=no" name="viewport">
<meta content="exploring" name="csswg-work-status">
<meta content="UD" name="w3c-status">
<meta content="<a>High Contrast</a> allows authors to detect and participate in high contrast mode changes." name="abstract">
<link href="https://drafts.csswg.org/default.css" rel="stylesheet" type="text/css">
<link href="https://drafts.csswg.org/csslogo.ico" rel="shortcut icon" type="image/x-icon">
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</style>
<body class="h-entry">
<div class="head">
<p data-fill-with="logo"><a class="logo" href="https://www.w3.org/"> <img alt="W3C" height="48" src="https://www.w3.org/StyleSheets/TR/2016/logos/W3C" width="72"> </a> </p>
<h1 class="p-name no-ref" id="title">CSS High Contrast</h1>
<h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="content">Unofficial Proposal Draft, <time class="dt-updated" datetime="2019-04-02">2 April 2019</time></span></h2>
<div data-fill-with="spec-metadata">
<dl>
<dt>Previous Versions:
<dd><a href rel="prev"></a>
<dt>Issue Tracking:
<dd><a href="#issues-index">Inline In Spec</a>
<dd><a href="https://github.com/w3c/csswg-drafts/labels/high-contrast-1">GitHub Issues</a>
<dt class="editor">Editors:
<dd class="editor p-author h-card vcard" data-editor-id="49885"><a class="p-name fn u-email email" href="mailto:ratan@microsoft.com">Rossen Atanassov</a> (<span class="p-org org">Microsoft</span>)
<dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:mrichards@microsoft.com">Melanie Richards</a> (<span class="p-org org">Microsoft</span>)
<dt>Suggest an Edit for this Spec:
<dd><a href="https://github.com/w3c/csswg-drafts/blob/master/high-contrast-1/Overview.bs">GitHub Editor</a>
</dl>
</div>
<div data-fill-with="warning"></div>
<p class="copyright" data-fill-with="copyright"><a href="https://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2019 <a href="https://www.w3.org/"><abbr title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> (<a href="https://www.csail.mit.edu/"><abbr title="Massachusetts Institute of Technology">MIT</abbr></a>, <a href="https://www.ercim.eu/"><abbr title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href="https://www.keio.ac.jp/">Keio</a>, <a href="https://ev.buaa.edu.cn/">Beihang</a>). W3C <a href="https://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>, <a href="https://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and <a href="https://www.w3.org/Consortium/Legal/2015/copyright-software-and-document">permissive document license</a> rules apply. </p>
<hr title="Separator for header">
</div>
<div class="p-summary" data-fill-with="abstract">
<h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2>
<p><a data-link-type="dfn">High Contrast</a> allows authors to detect and participate in high contrast mode changes.</p>
<a href="https://www.w3.org/TR/CSS/">CSS</a> is a language for describing the rendering of structured documents
(such as HTML and XML)
on screen, on paper, etc.
</div>
<h2 class="no-num no-toc no-ref heading settled" id="status"><span class="content">Status of this document</span></h2>
<div data-fill-with="status">
<p></p>
<p>Once complete, this specification will include and extend <cite>Media Queries Level 4.</cite> <a data-link-type="biblio" href="#biblio-mediaqueries-4">[MEDIAQUERIES-4]</a></p>
</div>
<div data-fill-with="at-risk"></div>
<nav data-fill-with="table-of-contents" id="toc">
<h2 class="no-num no-toc no-ref" id="contents">Table of Contents</h2>
<ol class="toc" role="directory">
<li><a href="#intro"><span class="secno">1</span> <span class="content"> Introduction</span></a>
<li>
<a href="#nc-mediaquery"><span class="secno">2</span> <span class="content"> Media Query</span></a>
<ol class="toc">
<li><a href="#high-contrast"><span class="secno">2.1</span> <span class="content"> Detecting the high contrast color mode: the <span class="property">high-contrast</span> feature</span></a>
</ol>
<li>
<a href="#hc-adjust"><span class="secno">3</span> <span class="content"> High Contrast Adjust</span></a>
<ol class="toc">
<li><a href="#high-contrast-adjust"><span class="secno">3.1</span> <span class="content"> Overriding the high contrast color mode: the <span class="property">high-contrast-adjust</span> property</span></a>
</ol>
<li><a href="#hc-cascade"><span class="secno">4</span> <span class="content"> Cascade Order</span></a>
<li><a href="#acknowledgments"><span class="secno"></span> <span class="content"> Acknowledgments</span></a>
<li>
<a href="#conformance"><span class="secno"></span> <span class="content"> Conformance</span></a>
<ol class="toc">
<li><a href="#document-conventions"><span class="secno"></span> <span class="content"> Document conventions</span></a>
<li><a href="#conform-classes"><span class="secno"></span> <span class="content"> Conformance classes</span></a>
<li>
<a href="#conform-responsible"><span class="secno"></span> <span class="content"> Requirements for Responsible Implementation of CSS</span></a>
<ol class="toc">
<li><a href="#conform-partial"><span class="secno"></span> <span class="content"> Partial Implementations</span></a>
<li><a href="#conform-future-proofing"><span class="secno"></span> <span class="content"> Implementations of Unstable and Proprietary Features</span></a>
<li><a href="#conform-testing"><span class="secno"></span> <span class="content"> Implementations of CR-level Features</span></a>
</ol>
</ol>
<li>
<a href="#index"><span class="secno"></span> <span class="content">Index</span></a>
<ol class="toc">
<li><a href="#index-defined-here"><span class="secno"></span> <span class="content">Terms defined by this specification</span></a>
<li><a href="#index-defined-elsewhere"><span class="secno"></span> <span class="content">Terms defined by reference</span></a>
</ol>
<li>
<a href="#references"><span class="secno"></span> <span class="content">References</span></a>
<ol class="toc">
<li><a href="#normative"><span class="secno"></span> <span class="content">Normative References</span></a>
<li><a href="#informative"><span class="secno"></span> <span class="content">Informative References</span></a>
</ol>
<li>
<a href="#property-index"><span class="secno"></span> <span class="content">Property Index</span></a>
<ol class="toc">
<li><a href="#media-descriptor-table"><span class="secno"></span> <span class="content"><span>@media</span> Descriptors</span></a>
</ol>
<li><a href="#issues-index"><span class="secno"></span> <span class="content">Issues Index</span></a>
</ol>
</nav>
<main>
<h2 class="heading settled" data-level="1" id="intro"><span class="secno">1. </span><span class="content"> Introduction</span><a class="self-link" href="#intro"></a></h2>
<p>High contrast is an accessibility feature intended to increase the readability of text while
reducing cognitive load. The OS platform feature works by enabling the user to select theme colors
for a scoped number of semantic elements. This scheme can then be applied to user interfaces (UI)
and app content, reducing the visual complexity of the UI while guaranteeing the user’s preferred
contrast level. Many people may find it more comfortable to read digital text consistently tailored
to their theme. To honor this strong user preference, this color mode is typically automatically
applied to web content.</p>
<h2 class="heading settled" data-level="2" id="nc-mediaquery"><span class="secno">2. </span><span class="content"> Media Query</span><a class="self-link" href="#nc-mediaquery"></a></h2>
<p>To allow developers to make style adjustments when high contrast styles are applied, a media query
type called <a class="property" data-link-type="propdesc" href="#descdef-media-high-contrast" id="ref-for-descdef-media-high-contrast">high-contrast</a> would be added. If a high-contrast media query evaluates to true, any
styles defined within that media query will be used when in high contrast, and will not be overridden
by the high contrast feature.</p>
<h3 class="heading settled" data-level="2.1" id="high-contrast"><span class="secno">2.1. </span><span class="content"> Detecting the high contrast color mode: the <a class="property" data-link-type="propdesc" href="#descdef-media-high-contrast" id="ref-for-descdef-media-high-contrast①">high-contrast</a> feature</span><a class="self-link" href="#high-contrast"></a></h3>
<table class="def descdef mq">
<tbody>
<tr>
<th>Name:
<td><dfn class="dfn-paneled css" data-dfn-for="@media" data-dfn-type="descriptor" data-export id="descdef-media-high-contrast">high-contrast</dfn>
<tr>
<th>For:
<td><a class="css" data-link-type="at-rule" href="https://drafts.csswg.org/css-conditional-3/#at-ruledef-media" id="ref-for-at-ruledef-media">@media</a>
<tr>
<th>Value:
<td class="prod">active <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-4/#comb-one" id="ref-for-comb-one">|</a> black-on-white <span id="ref-for-comb-one①">|</span> white-on-black
<tr>
<th>Type:
<td>discrete
</table>
<p>The <a class="property" data-link-type="propdesc" href="#descdef-media-high-contrast" id="ref-for-descdef-media-high-contrast②">high-contrast</a> media feature is used to query about the presence of the high contrast color
mode on the system, to allow the author to adjust style of the document in response. The following
values are valid:</p>
<dl>
<dt><dfn class="css" data-dfn-for="@media/high-contrast" data-dfn-type="value" data-export id="valdef-media-high-contrast-active">active<a class="self-link" href="#valdef-media-high-contrast-active"></a></dfn>
<dd> The device is used in a high contrast environment, where color mode is used to improve the
contrast between foregrounds and backrounds. Evaluates to true regardless of whether the
particular scheme is black-on-white, white-on-black, or other.
<dt><dfn class="css" data-dfn-for="@media/high-contrast" data-dfn-type="value" data-export id="valdef-media-high-contrast-black-on-white">black-on-white<a class="self-link" href="#valdef-media-high-contrast-black-on-white"></a></dfn>
<dd> Evaluates to true when high contrast is enabled under the black-on-white color theme.
<dt><dfn class="css" data-dfn-for="@media/high-contrast" data-dfn-type="value" data-export id="valdef-media-high-contrast-white-on-black">white-on-black<a class="self-link" href="#valdef-media-high-contrast-white-on-black"></a></dfn>
<dd> Evaluates to true when high contrast is enabled under the white-on-black color theme.
</dl>
<div class="example" id="example-9ea87a54">
<a class="self-link" href="#example-9ea87a54"></a>
<pre class="lang-css highlight"><c- c>/**</c->
<c- c> * Author’s icons are typically presented in a brand color; author wishes to match these</c->
<c- c> * to the contextual text color in any high contrast scheme.</c->
<c- c> */</c->
<c- n>@media</c-> <c- p>(</c->high-contrast<c- f>: active) </c-><c- p>{</c->
.icon path {
stroke: currentColor;
}
}
</pre>
</div>
<div class="example" id="example-d9ff6ebf">
<a class="self-link" href="#example-d9ff6ebf"></a>
<pre class="lang-css highlight"><c- c>/**</c->
<c- c> * Author wishes to add a subtle background effect in high contrast environments where </c->
<c- c> * the general theme is known.</c->
<c- c> */</c->
<c- n>@media</c-> <c- p>(</c->high-contrast<c- f>: black-on-white) </c-><c- p>{</c->
header {
background: linear-gradient(#dedede, #fff 2em);
}
}
@media (high-contrast: white-on-black) {
header {
background: linear-gradient(#333, #000 2em);
}
}
</pre>
</div>
<p class="issue" id="issue-c500cd70"><a class="self-link" href="#issue-c500cd70"></a> The naming of <a class="property" data-link-type="propdesc" href="#descdef-media-high-contrast" id="ref-for-descdef-media-high-contrast③">high-contrast</a> comes from the Windows theming feature, and a more general
name can be considered (e.g. <code>user-color-mode</code>) to provide for future color modes. In such a case,
a general <span class="property" id="ref-for-descdef-media-high-contrast④">high-contrast</span> value keyword may be added to distinguish from activation of <strong>any</strong> color mode.</p>
<h2 class="heading settled" data-level="3" id="hc-adjust"><span class="secno">3. </span><span class="content"> High Contrast Adjust</span><a class="self-link" href="#hc-adjust"></a></h2>
<p>In some cases, it may be appropriate to override high contrast styles applied by the user agent: for
example if the color is important to consuming the content, or the author wishes to apply high contrast
colors in a manner different to the user agent stylesheet. A <a class="property" data-link-type="propdesc" href="#propdef-high-contrast-adjust" id="ref-for-propdef-high-contrast-adjust">high-contrast-adjust</a> property would
enable the author to prevent the high contrast mode from adjusting styles.</p>
<h3 class="heading settled" data-level="3.1" id="high-contrast-adjust"><span class="secno">3.1. </span><span class="content"> Overriding the high contrast color mode: the <a class="property" data-link-type="propdesc" href="#propdef-high-contrast-adjust" id="ref-for-propdef-high-contrast-adjust①">high-contrast-adjust</a> property</span><a class="self-link" href="#high-contrast-adjust"></a></h3>
<table class="def propdef" data-link-for-hint="high-contrast-adjust">
<tbody>
<tr>
<th>Name:
<td><dfn class="dfn-paneled css" data-dfn-type="property" data-export id="propdef-high-contrast-adjust">high-contrast-adjust</dfn>
<tr class="value">
<th><a href="https://drafts.csswg.org/css-values/#value-defs">Value:</a>
<td class="prod">auto <a data-link-type="grammar" href="https://drafts.csswg.org/css-values-4/#comb-one" id="ref-for-comb-one②">|</a> none
<tr>
<th><a href="https://drafts.csswg.org/css-cascade/#initial-values">Initial:</a>
<td>auto
<tr>
<th>Applies to:
<td><a href="https://drafts.csswg.org/css-pseudo/#generated-content" title="Includes ::before and ::after pseudo-elements.">all elements</a>
<tr>
<th><a href="https://drafts.csswg.org/css-cascade/#inherited-property">Inherited:</a>
<td>no
<tr>
<th><a href="https://drafts.csswg.org/css-values/#percentages">Percentages:</a>
<td>n/a
<tr>
<th><a href="https://drafts.csswg.org/css-cascade/#computed">Computed value:</a>
<td>specified keyword
<tr>
<th>Canonical order:
<td>per grammar
<tr>
<th><a href="https://drafts.csswg.org/web-animations/#animation-type">Animation type:</a>
<td>not animatable
</table>
<dl>
<dt><dfn class="css" data-dfn-for="high-contrast-override" data-dfn-type="value" data-export id="valdef-high-contrast-override-auto">auto<a class="self-link" href="#valdef-high-contrast-override-auto"></a></dfn>
<dd> Indicates the applicable CSS properties will be adjusted as expected when the system is in high
contrast mode.
<dt><dfn class="css" data-dfn-for="high-contrast-override" data-dfn-type="value" data-export id="valdef-high-contrast-override-none">none<a class="self-link" href="#valdef-high-contrast-override-none"></a></dfn>
<dd> Indicates the applicable CSS properties will not be adjusted when the system is in high contrast
mode. Applies to the given element and its subtree.
</dl>
<div class="example" id="example-c7300467">
<a class="self-link" href="#example-c7300467"></a>
<pre class="lang-css highlight"><c- c>/**</c->
<c- c>* Author preserves brand colors in a style guide</c->
<c- c>*/</c->
<c- n>@media</c-> <c- p>(</c->high-contrast<c- f>: active) </c-><c- p>{</c->
.color-swatch {
high-contrast-adjust: none;
}
}
</pre>
</div>
<div class="example" id="example-7517ff3d">
<a class="self-link" href="#example-7517ff3d"></a>
<pre class="lang-css highlight"><c- c>/**</c->
<c- c>* Author wishes to style popular highlights in an article, which may contain links</c->
<c- c>*/</c->
<c- n>@media</c-> <c- p>(</c->high-contrast<c- f>: active) </c-><c- p>{</c->
.highlight {
high-contrast-adjust: none;
color: Window;
background: WindowText;
}
.highlight a:link,
.highlight a:visited {
border-bottom: 2px solid;
color: Window;
}
}
</pre>
</div>
<p class="note" role="note"><span>Note:</span> The example uses CSS System Colors to set content to abstracted user colors. This could be
alternatively achieved by extending the available environment variables accessed via <code>env()</code>.</p>
<h2 class="heading settled" data-level="4" id="hc-cascade"><span class="secno">4. </span><span class="content"> Cascade Order</span><a class="self-link" href="#hc-cascade"></a></h2>
<p>High contrast color schemes work by overriding user defined styles for various
CSS properties in order to ensure readability. The process model for such high contrast overrides is
as follows:</p>
<p>Given an element and a declaration from a CSS rule whose selector matches that element, the application
of that declaration will be suppressed if all of the following conditions are met:</p>
<ol>
<li data-md>
<p>The declaration is for a CSS property in the set of properties that are adjusted for high contrast
(as defined by the user agent style sheet)</p>
<li data-md>
<p>High contrast mode is enabled in the host environment</p>
<li data-md>
<p>The computed value of <a class="property" data-link-type="propdesc" href="#propdef-high-contrast-adjust" id="ref-for-propdef-high-contrast-adjust②">high-contrast-adjust</a> on the element or its ancestor is <code>auto</code></p>
<li data-md>
<p>The rule is not contained (directly or indirectly) inside an <code>@media</code> block matching the <a class="property" data-link-type="propdesc" href="#descdef-media-high-contrast" id="ref-for-descdef-media-high-contrast⑤">high-contrast</a> media feature</p>
<li data-md>
<p>The rule is not defined in the default user agent style sheet</p>
</ol>
<p>If all of the above conditions are met, the computed color value of the CSS property is overridden by
a system color value.</p>
<h2 class="no-num heading settled" id="acknowledgments"><span class="content"> Acknowledgments</span><a class="self-link" href="#acknowledgments"></a></h2>
<p>This specification is the product of the W3C Working Group on Cascading Style Sheets.</p>
</main>
<h2 class="no-ref no-num heading settled" id="conformance"><span class="content"> Conformance</span><a class="self-link" href="#conformance"></a></h2>
<h3 class="heading settled" id="document-conventions"><span class="content"> Document conventions</span><a class="self-link" href="#document-conventions"></a></h3>
<p>Conformance requirements are expressed with a combination of
descriptive assertions and RFC 2119 terminology. The key words “MUST”,
“MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”,
“RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this
document are to be interpreted as described in RFC 2119.
However, for readability, these words do not appear in all uppercase
letters in this specification. </p>
<p>All of the text of this specification is normative except sections
explicitly marked as non-normative, examples, and notes. <a data-link-type="biblio" href="#biblio-rfc2119">[RFC2119]</a> </p>
<p>Examples in this specification are introduced with the words “for example”
or are set apart from the normative text with <code>class="example"</code>,
like this: </p>
<div class="example" id="example-ae2b6bc0">
<a class="self-link" href="#example-ae2b6bc0"></a>
<p>This is an example of an informative example. </p>
</div>
<p>Informative notes begin with the word “Note” and are set apart from the
normative text with <code>class="note"</code>, like this: </p>
<p class="note" role="note">Note, this is an informative note. </p>
<p>Advisements are normative sections styled to evoke special attention and are
set apart from other normative text with <code><strong class="advisement"></code>, like
this: <strong class="advisement"> UAs MUST provide an accessible alternative. </strong> </p>
<h3 class="heading settled" id="conform-classes"><span class="content"> Conformance classes</span><a class="self-link" href="#conform-classes"></a></h3>
<p>Conformance to this specification
is defined for three conformance classes: </p>
<dl>
<dt>style sheet
<dd>A <a href="http://www.w3.org/TR/CSS2/conform.html#style-sheet">CSS
style sheet</a>.
<dt>renderer
<dd>A <a href="http://www.w3.org/TR/CSS2/conform.html#user-agent">UA</a> that interprets the semantics of a style sheet and renders
documents that use them.
<dt>authoring tool
<dd>A <a href="http://www.w3.org/TR/CSS2/conform.html#user-agent">UA</a> that writes a style sheet.
</dl>
<p>A style sheet is conformant to this specification
if all of its statements that use syntax defined in this module are valid
according to the generic CSS grammar and the individual grammars of each
feature defined in this module. </p>
<p>A renderer is conformant to this specification
if, in addition to interpreting the style sheet as defined by the
appropriate specifications, it supports all the features defined
by this specification by parsing them correctly
and rendering the document accordingly. However, the inability of a
UA to correctly render a document due to limitations of the device
does not make the UA non-conformant. (For example, a UA is not
required to render color on a monochrome monitor.) </p>
<p>An authoring tool is conformant to this specification
if it writes style sheets that are syntactically correct according to the
generic CSS grammar and the individual grammars of each feature in
this module, and meet all other conformance requirements of style sheets
as described in this module. </p>
<h3 class="heading settled" id="conform-responsible"><span class="content"> Requirements for Responsible Implementation of CSS</span><a class="self-link" href="#conform-responsible"></a></h3>
<p>The following sections define several conformance requirements
for implementing CSS responsibly,
in a way that promotes interoperability in the present and future. </p>
<h4 class="heading settled" id="conform-partial"><span class="content"> Partial Implementations</span><a class="self-link" href="#conform-partial"></a></h4>
<p>So that authors can exploit the forward-compatible parsing rules to assign fallback values, <strong>CSS renderers <em>must</em> treat as invalid
(and <a href="http://www.w3.org/TR/CSS2/conform.html#ignore">ignore as appropriate</a>)
any at-rules, properties, property values, keywords, and other syntactic constructs
for which they have no usable level of support</strong>.
In particular, user agents <em>must not</em> selectively ignore
unsupported property values and honor supported values in a single multi-value property declaration:
if any value is considered invalid (as unsupported values must be),
CSS requires that the entire declaration be ignored. </p>
<h4 class="heading settled" id="conform-future-proofing"><span class="content"> Implementations of Unstable and Proprietary Features</span><a class="self-link" href="#conform-future-proofing"></a></h4>
<p>To avoid clashes with future stable CSS features,
the CSSWG recommends <a href="http://www.w3.org/TR/CSS/#future-proofing">following best practices</a> for the implementation of <a href="http://www.w3.org/TR/CSS/#unstable">unstable</a> features and <a href="http://www.w3.org/TR/CSS/#proprietary-extension">proprietary extensions</a> to CSS. </p>
<h4 class="heading settled" id="conform-testing"><span class="content"> Implementations of CR-level Features</span><a class="self-link" href="#conform-testing"></a></h4>
<p>Once a specification reaches the Candidate Recommendation stage,
implementers should release an <a data-link-type="dfn" href="http://www.w3.org/TR/CSS/#vendor-prefix">unprefixed</a> implementation
of any CR-level feature they can demonstrate
to be correctly implemented according to spec,
and should avoid exposing a prefixed variant of that feature. </p>
<p>To establish and maintain the interoperability of CSS across
implementations, the CSS Working Group requests that non-experimental
CSS renderers submit an implementation report (and, if necessary, the
testcases used for that implementation report) to the W3C before
releasing an unprefixed implementation of any CSS features. Testcases
submitted to W3C are subject to review and correction by the CSS
Working Group. </p>
<p>
Further information on submitting testcases and implementation reports
can be found from on the CSS Working Group’s website at <a href="http://www.w3.org/Style/CSS/Test/">http://www.w3.org/Style/CSS/Test/</a>.
Questions should be directed to the <a href="http://lists.w3.org/Archives/Public/public-css-testsuite">public-css-testsuite@w3.org</a> mailing list.
<script src="https://www.w3.org/scripts/TR/2016/fixup.js"></script>
</p>
<h2 class="no-num no-ref heading settled" id="index"><span class="content">Index</span><a class="self-link" href="#index"></a></h2>
<h3 class="no-num no-ref heading settled" id="index-defined-here"><span class="content">Terms defined by this specification</span><a class="self-link" href="#index-defined-here"></a></h3>
<ul class="index">
<li><a href="#valdef-media-high-contrast-active">active</a><span>, in §2.1</span>
<li><a href="#valdef-high-contrast-override-auto">auto</a><span>, in §3.1</span>
<li><a href="#valdef-media-high-contrast-black-on-white">black-on-white</a><span>, in §2.1</span>
<li><a href="#descdef-media-high-contrast">high-contrast</a><span>, in §2.1</span>
<li><a href="#propdef-high-contrast-adjust">high-contrast-adjust</a><span>, in §3.1</span>
<li><a href="#valdef-high-contrast-override-none">none</a><span>, in §3.1</span>
<li><a href="#valdef-media-high-contrast-white-on-black">white-on-black</a><span>, in §2.1</span>
</ul>
<aside class="dfn-panel" data-for="term-for-at-ruledef-media">
<a href="https://drafts.csswg.org/css-conditional-3/#at-ruledef-media">https://drafts.csswg.org/css-conditional-3/#at-ruledef-media</a><b>Referenced in:</b>
<ul>
<li><a href="#ref-for-at-ruledef-media">2.1.
Detecting the high contrast color mode: the high-contrast feature</a>
</ul>
</aside>
<aside class="dfn-panel" data-for="term-for-comb-one">
<a href="https://drafts.csswg.org/css-values-4/#comb-one">https://drafts.csswg.org/css-values-4/#comb-one</a><b>Referenced in:</b>
<ul>
<li><a href="#ref-for-comb-one">2.1.
Detecting the high contrast color mode: the high-contrast feature</a> <a href="#ref-for-comb-one①">(2)</a>
<li><a href="#ref-for-comb-one②">3.1.
Overriding the high contrast color mode: the high-contrast-adjust property</a>
</ul>
</aside>
<h3 class="no-num no-ref heading settled" id="index-defined-elsewhere"><span class="content">Terms defined by reference</span><a class="self-link" href="#index-defined-elsewhere"></a></h3>
<ul class="index">
<li>
<a data-link-type="biblio">[css-conditional-3]</a> defines the following terms:
<ul>
<li><span class="dfn-paneled" id="term-for-at-ruledef-media" style="color:initial">@media</span>
</ul>
<li>
<a data-link-type="biblio">[css-values-4]</a> defines the following terms:
<ul>
<li><span class="dfn-paneled" id="term-for-comb-one" style="color:initial">|</span>
</ul>
</ul>
<h2 class="no-num no-ref heading settled" id="references"><span class="content">References</span><a class="self-link" href="#references"></a></h2>
<h3 class="no-num no-ref heading settled" id="normative"><span class="content">Normative References</span><a class="self-link" href="#normative"></a></h3>
<dl>
<dt id="biblio-css-conditional-3">[CSS-CONDITIONAL-3]
<dd>CSS Conditional Rules Module Level 3 URL: <a href="https://www.w3.org/TR/css3-conditional/">https://www.w3.org/TR/css3-conditional/</a>
<dt id="biblio-css-values-4">[CSS-VALUES-4]
<dd>Tab Atkins Jr.; Elika Etemad. <a href="https://www.w3.org/TR/css-values-4/">CSS Values and Units Module Level 4</a>. 31 January 2019. WD. URL: <a href="https://www.w3.org/TR/css-values-4/">https://www.w3.org/TR/css-values-4/</a>
<dt id="biblio-rfc2119">[RFC2119]
<dd>S. Bradner. <a href="https://tools.ietf.org/html/rfc2119">Key words for use in RFCs to Indicate Requirement Levels</a>. March 1997. Best Current Practice. URL: <a href="https://tools.ietf.org/html/rfc2119">https://tools.ietf.org/html/rfc2119</a>
</dl>
<h3 class="no-num no-ref heading settled" id="informative"><span class="content">Informative References</span><a class="self-link" href="#informative"></a></h3>
<dl>
<dt id="biblio-mediaqueries-4">[MEDIAQUERIES-4]
<dd>Florian Rivoal; Tab Atkins Jr.. <a href="https://www.w3.org/TR/mediaqueries-4/">Media Queries Level 4</a>. 5 September 2017. CR. URL: <a href="https://www.w3.org/TR/mediaqueries-4/">https://www.w3.org/TR/mediaqueries-4/</a>
</dl>
<h2 class="no-num no-ref heading settled" id="property-index"><span class="content">Property Index</span><a class="self-link" href="#property-index"></a></h2>
<div class="big-element-wrapper">
<table class="index">
<thead>
<tr>
<th scope="col">Name
<th scope="col">Value
<th scope="col">Initial
<th scope="col">Applies to
<th scope="col">Inh.
<th scope="col">%ages
<th scope="col">Animation type
<th scope="col">Canonical order
<th scope="col">Computed value
<tbody>
<tr>
<th scope="row"><a class="css" data-link-type="property" href="#propdef-high-contrast-adjust" id="ref-for-propdef-high-contrast-adjust③">high-contrast-adjust</a>
<td>auto | none
<td>auto
<td>all elements
<td>no
<td>n/a
<td>not animatable
<td>per grammar
<td>specified keyword
</table>
</div>
<h3 class="no-num no-ref heading settled" id="media-descriptor-table"><span class="content"><a class="css" data-link-type="at-rule" href="https://drafts.csswg.org/css-conditional-3/#at-ruledef-media" id="ref-for-at-ruledef-media①">@media</a> Descriptors</span><a class="self-link" href="#media-descriptor-table"></a></h3>
<div class="big-element-wrapper">
<table class="index">
<thead>
<tr>
<th scope="col">Name
<th scope="col">Value
<th scope="col">Initial
<th scope="col">Type
<tbody>
<tr>
<th scope="row"><a class="css" data-link-type="descriptor" href="#descdef-media-high-contrast" id="ref-for-descdef-media-high-contrast⑥">high-contrast</a>
<td>active | black-on-white | white-on-black
<td>
<td>discrete
</table>
</div>
<h2 class="no-num no-ref heading settled" id="issues-index"><span class="content">Issues Index</span><a class="self-link" href="#issues-index"></a></h2>
<div style="counter-reset:issue">
<div class="issue"> The naming of <a class="property" data-link-type="propdesc" href="#descdef-media-high-contrast">high-contrast</a> comes from the Windows theming feature, and a more general
name can be considered (e.g. <code>user-color-mode</code>) to provide for future color modes. In such a case,
a general <span class="property">high-contrast</span> value keyword may be added to distinguish from activation of <strong>any</strong> color mode.<a href="#issue-c500cd70"> ↵ </a></div>
</div>
<aside class="dfn-panel" data-for="descdef-media-high-contrast">
<b><a href="#descdef-media-high-contrast">#descdef-media-high-contrast</a></b><b>Referenced in:</b>
<ul>
<li><a href="#ref-for-descdef-media-high-contrast">2.
Media Query</a>
<li><a href="#ref-for-descdef-media-high-contrast①">2.1.
Detecting the high contrast color mode: the high-contrast feature</a> <a href="#ref-for-descdef-media-high-contrast②">(2)</a> <a href="#ref-for-descdef-media-high-contrast③">(3)</a> <a href="#ref-for-descdef-media-high-contrast④">(4)</a>
<li><a href="#ref-for-descdef-media-high-contrast⑤">4.
Cascade Order</a>
</ul>
</aside>
<aside class="dfn-panel" data-for="propdef-high-contrast-adjust">
<b><a href="#propdef-high-contrast-adjust">#propdef-high-contrast-adjust</a></b><b>Referenced in:</b>
<ul>
<li><a href="#ref-for-propdef-high-contrast-adjust">3.
High Contrast Adjust</a>
<li><a href="#ref-for-propdef-high-contrast-adjust①">3.1.
Overriding the high contrast color mode: the high-contrast-adjust property</a>
<li><a href="#ref-for-propdef-high-contrast-adjust②">4.
Cascade Order</a>
</ul>
</aside>
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