css-conditional/Overview.src.html

Fri, 29 Mar 2013 14:38:58 -0700

author
L. David Baron <dbaron@dbaron.org>
date
Fri, 29 Mar 2013 14:38:58 -0700
changeset 7863
b37f9017599f
parent 7862
9c11758e9fb5
child 7907
4cf8a925226d
permissions
-rw-r--r--

Fix changelog links in response to spec renaming (and don't use SHORTNAME since SHORTNAME is broken).

dbaron@2974 1 <!DOCTYPE html public '-//W3C//DTD HTML 4.01//EN'
dbaron@2974 2 'http://www.w3.org/TR/html4/strict.dtd'>
dbaron@2974 3 <html lang="en">
dbaron@2974 4 <head profile="http://www.w3.org/2006/03/hcard">
dbaron@2974 5 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
dbaron@2974 6 <title>CSS Conditional Rules Module Level 3</title>
dbaron@2974 7 <link rel="stylesheet" type="text/css" href="../default.css">
jackalmage@7274 8 <link href="../csslogo.ico" rel="shortcut icon" type="image/x-icon">
jackalmage@7274 9 <link rel="stylesheet" type="text/css" href="http://www.w3.org/StyleSheets/TR/W3C-[STATUS].css">
fantasai@7042 10 <!--
peter@6932 11 <script src="http://test.csswg.org/harness/annotate.js#CSS3-CONDITIONAL_DEV"
fantasai@7042 12 type="text/javascript" defer></script
fantasai@7042 13 -->
dbaron@2974 14 </head>
tantek@7538 15 <body class="h-entry">
dbaron@2974 16
dbaron@2974 17 <div class="head">
dbaron@2974 18 <!--logo-->
dbaron@2974 19
tantek@7538 20 <h1 class="p-name">CSS Conditional Rules Module Level 3</h1>
dbaron@2974 21
tantek@7538 22 <h2 class="no-num no-toc">[LONGSTATUS] <span class="dt-updated"><span class="value-title" title="[CDATE]">[DATE]</span></span></h2>
dbaron@2974 23 <dl>
dbaron@2974 24 <dt>This version:
tantek@7538 25 <dd><a class="u-url" href="[VERSION]">
dbaron@7372 26 http://www.w3.org/TR/[YEAR]/ED-css3-conditional-[CDATE]/</a>
dbaron@2974 27
dbaron@2974 28 <dt>Latest version:
dbaron@3241 29 <dd><a href="http://www.w3.org/TR/[SHORTNAME]/">http://www.w3.org/TR/[SHORTNAME]/</a>
dbaron@2974 30
dbaron@3245 31 <dt>Editor's draft:
bert@3404 32 <dd><a href="http://dev.w3.org/csswg/[SHORTNAME]/">http://dev.w3.org/csswg/[SHORTNAME]/</a>
dbaron@7863 33 (<a href="https://dvcs.w3.org/hg/csswg/log/tip/css-conditional/Overview.src.html">change log</a>,
dbaron@7863 34 <a href="https://dvcs.w3.org/hg/csswg/log/tip/css3-conditional/Overview.src.html">older change log</a>)
dbaron@3245 35
dbaron@2974 36 <dt>Previous version:
dbaron@7733 37 <dd><a rel="previous" href="http://www.w3.org/TR/2012/WD-css3-conditional-20121213/">http://www.w3.org/TR/2012/WD-css3-conditional-20121213/</a></dd>
dbaron@2974 38
dbaron@2974 39 <dt>Editors:
tantek@7538 40 <dd class="p-author h-card vcard"><a class="p-name fn u-url url" rel="author" href="http://dbaron.org/">L. David Baron</a>,
tantek@7538 41 <a class="p-org org h-org" href="http://www.mozilla.org/">Mozilla</a>
dbaron@3744 42
dbaron@3744 43 <dt>Issues list:
dbaron@3744 44 <dd>Maintained in document (only editor's draft is current)
dbaron@3744 45
jackalmage@7856 46 <dt>Feedback:</dt>
jackalmage@7856 47 <dd><a href="mailto:www-style@w3.org?subject=%5B[css-conditional]%5D%20feedback"
jackalmage@7856 48 >www-style@w3.org</a>
jackalmage@7856 49 with subject line &ldquo;<kbd>[css-conditional]
jackalmage@7856 50 <var>&hellip; message topic &hellip;</var></kbd>&rdquo;
jackalmage@7856 51 (<a rel="discussion" href="http://lists.w3.org/Archives/Public/www-style/"
jackalmage@7856 52 >archives</a>)
dbaron@3744 53
dbaron@3744 54 <dt>Test suite:
dbaron@7733 55 <dd><a href="https://test.csswg.org/shepherd/search/spec/css3-conditional/">submitted tests</a>,
dbaron@7733 56 <a href="https://test.csswg.org/harness/suite/CSS3-CONDITIONAL_DEV/">nightly test suite</a>
dbaron@3744 57
dbaron@2974 58 </dl>
dbaron@2974 59
dbaron@2974 60 <!--copyright-->
dbaron@2974 61
dbaron@2974 62 <hr title="Separator for header">
dbaron@2974 63 </div>
dbaron@2974 64
jackalmage@6617 65 <h2 class="no-num no-toc" id="abstract">Abstract</h2>
dbaron@2974 66
dbaron@2974 67 <p>CSS is a language for describing the rendering of structured documents
tantek@7538 68 (such as HTML and XML) on screen, on paper, in speech, etc.
tantek@7538 69 <span class="p-summary">
tantek@7538 70 This module
dbaron@2974 71 contains the features of CSS for conditional processing of parts of
dbaron@2974 72 style sheets, conditioned on capabilities of the processor or the
dbaron@2974 73 document the style sheet is being applied to.
dbaron@2974 74 It includes and extends the functionality of CSS level&nbsp;2 [[!CSS21]],
dbaron@2974 75 which builds on CSS level&nbsp;1 [[CSS1]].
dbaron@2974 76 The main extensions compared to level&nbsp;2 are
dbaron@2983 77 allowing nesting of certain at-rules inside '@media',
jackalmage@6838 78 and the addition of the '@supports'
jackalmage@6838 79 rule for conditional processing.
tantek@7538 80 </span>
dbaron@2974 81
jackalmage@6617 82 <h2 class="no-num no-toc" id="status">Status of this document</h2>
dbaron@2974 83
dbaron@2974 84 <!--status-->
dbaron@2974 85
dbaron@2974 86 <p>The following features are at risk:
dbaron@2974 87 <ul>
dbaron@2983 88 <li>The inclusion of '@font-face' rules and
dbaron@2983 89 '@keyframes' rules as allowed within all of the @-rules in
dbaron@2974 90 this specification is at risk, though only because of the relative
dbaron@2974 91 rates of advancement of specifications. If this specification is able
dbaron@2974 92 to advance faster than one or both of the specifications defining
dbaron@2974 93 those rules, then the inclusion of those rules will move from this
dbaron@2974 94 specification to the specification defining those rules.</li>
dbaron@2974 95
dbaron@2974 96 <li>The addition of support for @-rules inside of conditional grouping
dbaron@2974 97 rules is at risk; if interoperable implementations are not found, it
dbaron@2974 98 may be removed to advance the other features in this specification to
dbaron@2974 99 Proposed Recommendation.</li>
dbaron@2974 100
dbaron@2983 101 <li>The '@supports' rule is at risk; if interoperable
dbaron@2974 102 implementations are not found, it may be removed to advance the other
dbaron@2974 103 features in this specification to Proposed Recommendation.</li>
jackalmage@6838 104 </ul>
jackalmage@6837 105
jackalmage@6838 106 <!--
dbaron@2974 107
jackalmage@6838 108 Things to go in level 4:
jackalmage@6838 109
jackalmage@6838 110 * Create some way to put these new conditional things on an @import.
jackalmage@6838 111 * The @document rule (commented out, down below).
jackalmage@6838 112
jackalmage@6838 113 -->
dbaron@2974 114
jackalmage@6617 115 <h2 class="no-num no-toc" id="contents">Table of contents</h2>
dbaron@2974 116
dbaron@2974 117 <!--toc-->
dbaron@2974 118
jackalmage@6617 119 <h2 id="introduction">Introduction</h2>
dbaron@2974 120
jackalmage@6617 121 <h3 id="context">Background</h3>
dbaron@2974 122
dbaron@2974 123 <p><em>This section is not normative.</em>
dbaron@2974 124
dbaron@2974 125 <p>[[!CSS21]] defines one type of conditional group rule, the
dbaron@2983 126 '@media' rule, and allows only rulesets (not other @-rules)
dbaron@2983 127 inside of it. The '@media' rule provides the ability to
dbaron@2974 128 have media-specific style sheets, which is also provided by style
dbaron@2983 129 sheet linking features such as '@import' and
dbaron@2983 130 <code class="html">&lt;link&gt;</code>. The restrictions on the contents of
dbaron@2983 131 '@media' rules made them less useful; they have forced authors
dbaron@2974 132 using CSS features involving @-rules in media-specific style sheets to
dbaron@2974 133 use separate style sheets for each medium.</p>
dbaron@2974 134
dbaron@2974 135 <p>This specification extends the rules for the contents of
dbaron@2974 136 conditional group rules to allow other @-rules, which enables authors
dbaron@2974 137 to combine CSS features involving @-rules with media specific style
dbaron@2974 138 sheets within a single style sheet.</p>
dbaron@2974 139
jackalmage@6838 140 <p>This specification also defines an additional type of conditional
jackalmage@6838 141 group rule, '@supports', to
dbaron@2974 142 address author and user requirements.</p>
dbaron@2974 143
dbaron@2983 144 <p>The '@supports' rule allows CSS to be conditioned on
dbaron@2974 145 implementation support for CSS properties and values. This rule makes
dbaron@2974 146 it much easier for authors to use new CSS features and provide good
dbaron@2974 147 fallback for implementations that do not support those features. This
dbaron@2974 148 is particularly important for CSS features that provide new layout
dbaron@2974 149 mechanisms, and for other cases where a set of related styles needs to
dbaron@2974 150 be conditioned on property support.</p>
dbaron@2974 151
jackalmage@6617 152 <h3 id="placement">Module Interactions</h3>
dbaron@2974 153
dbaron@2983 154 <p>This module replaces and extends the '@media' rule
dbaron@2974 155 feature defined in [[!CSS21]] section <var>7.2.1</var> and
dbaron@2974 156 incorporates the modifications previously made non-normatively by
dbaron@2974 157 [[!MEDIAQ]] section <var>1</var>.</p>
dbaron@2974 158
dbaron@3462 159 <p>Its current definition depends on @-rules defined in [[!CSS3-FONTS]]
dbaron@2974 160 and [[!CSS3-ANIMATIONS]], but that dependency is only on the
dbaron@2974 161 assumption that those modules will advance ahead of this one. If this
dbaron@2974 162 module advances faster, then the dependency will be reversed.</p>
dbaron@2974 163
jackalmage@6617 164 <h3 id="conventions">Document Conventions</h3>
dbaron@2974 165
dbaron@2974 166 <p>Conformance requirements are expressed with a combination of
dbaron@2974 167 descriptive assertions and RFC 2119 terminology. The key words “MUST”,
dbaron@2974 168 “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”,
dbaron@2974 169 “RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this
dbaron@2974 170 document are to be interpreted as described in RFC 2119.
dbaron@2979 171 However, for readability, these words do not appear in all uppercase
dbaron@2979 172 letters in this specification.
dbaron@2974 173
dbaron@2974 174 <p>All of the text of this specification is normative except sections
dbaron@2974 175 explicitly marked as non-normative, examples, and notes. [[!RFC2119]]</p>
dbaron@2974 176
dbaron@2974 177 <p>Examples in this specification are introduced with the words “for example”
dbaron@2983 178 or are set apart from the normative text with
dbaron@2983 179 <code class="html">class="example"</code>, like this:
dbaron@2974 180
dbaron@2974 181 <div class="example">
dbaron@2974 182 <p>This is an example of an informative example.</p>
dbaron@2974 183 </div>
dbaron@2974 184
dbaron@2974 185 <p>Informative notes begin with the word “Note” and are set apart from the
dbaron@2983 186 normative text with <code class="html">class="note"</code>, like this:
dbaron@2974 187
dbaron@2974 188 <p class="note">Note, this is an informative note.</p>
dbaron@2974 189
jackalmage@6617 190 <h2 id="processing">Processing of conditional group rules</h2>
dbaron@2974 191
dbaron@2974 192 <p>This specification defines some CSS @-rules, called <dfn>conditional
dbaron@2974 193 group rules</dfn>, that associate a condition with a group of other
dbaron@2974 194 CSS rules. These different rules allow testing different types of
dbaron@2974 195 conditions, but share common behavior for how their contents are used
dbaron@2974 196 when the condition is true and when the condition is false.</p>
dbaron@2974 197
dbaron@2974 198 <div class="example">
dbaron@2974 199 <p>For example, this rule:</p>
dbaron@2974 200 <pre>@media print {
dbaron@7381 201 /* hide navigation controls when printing */
dbaron@2974 202 #navigation { display: none }
dbaron@2974 203 }</pre>
dbaron@2974 204 <p>causes a particular CSS rule (making elements with ID "navigation" be
dbaron@2974 205 display:none) apply only when the style sheet is used for a print
jackalmage@6838 206 medium.
dbaron@2974 207 </div>
dbaron@2974 208
dbaron@2974 209 <p>Each conditional group rule has a condition, which at any time
dbaron@2974 210 evaluates to true or false. When the condition is true, CSS processors
dbaron@2979 211 <strong>must</strong> apply the rules inside the group rule as though
dbaron@2979 212 they were at the group rule's location; when the condition is false, CSS
dbaron@3948 213 processors <strong>must not</strong> apply any of rules inside the group
dbaron@2979 214 rule. The current state of the condition does not affect the CSS object
dbaron@2979 215 model, in which the contents of the group rule always remain within the
dbaron@2979 216 group rule.</p>
dbaron@2974 217
dbaron@2974 218 <p>This means that when multiple conditional group rules are nested,
dbaron@2974 219 a rule inside of both of them applies only when all of the rules'
dbaron@2974 220 conditions are true.</p>
dbaron@2974 221
dbaron@2974 222 <div class="example">For example, with this set of nested rules:
dbaron@2974 223 <pre>@media print { // rule (1)
dbaron@7381 224 /* hide navigation controls when printing */
dbaron@2974 225 #navigation { display: none }
dbaron@2974 226 @media (max-width: 12cm) { // rule (2)
dbaron@7381 227 /* keep notes in flow when printing to narrow pages */
dbaron@2974 228 .note { float: none }
dbaron@2974 229 }
dbaron@2974 230 }</pre>
dbaron@2974 231 the condition of the rule marked (1) is true for print media, and the
dbaron@2974 232 condition of the rule marked (2) is true when the width of the display
dbaron@2974 233 area (which for print media is the page box) is less than or equal to
dbaron@2983 234 12cm. Thus the rule ''#navigation { display: none }'' applies
dbaron@2974 235 whenever this style sheet is applied to print media, and the rule
dbaron@2983 236 ''.note { float: none }'' is applied only when the style sheet
dbaron@2974 237 is applied to print media <em>and</em> the width of the page box is less
dbaron@2974 238 than or equal to 12 centimeters.</div>
dbaron@2974 239
dbaron@2979 240 <p>When the condition for a conditional group rule changes, CSS
dbaron@2979 241 processors <strong>must</strong> reflect that the rules now apply or no
dbaron@2979 242 longer apply, except for properties whose definitions define effects of
dbaron@2979 243 computed values that persist past the lifetime of that value (such as
dbaron@2979 244 for some properties in [[CSS3-TRANSITIONS]] and
dbaron@2979 245 [[!CSS3-ANIMATIONS]]).</p>
dbaron@2974 246
jackalmage@6617 247 <h2 id="contents-of">Contents of conditional group rules</h2>
dbaron@2974 248
dbaron@2974 249 <p>The syntax of each conditional group rule consists of some syntax
dbaron@2974 250 specific to the type of rule followed by a <dfn>group rule body</dfn>,
dbaron@2974 251 which is a block (pair of braces) containing a sequence of rules.</p>
dbaron@2974 252
dbaron@2974 253 <p>A group rule body is allowed to contain rulesets and any @-rules that
dbaron@2974 254 are allowed at the top level of a style sheet before and after a
dbaron@2974 255 ruleset. This means that @-rules that must occur at the beginning of
dbaron@3020 256 the style sheet (such as '@charset', '@import',
dbaron@3020 257 and '@namespace' rules) are not allowed inside of conditional group
dbaron@2974 258 rules. Conditional group rules can be nested.</p>
dbaron@2974 259
dbaron@2974 260 <p>In terms of the grammar, this specification defines the following
dbaron@2974 261 productions for use in the grammar of conditional group rules:</p>
dbaron@2974 262
dbaron@7032 263 <pre><dfn>nested_statement</dfn>
dbaron@7032 264 : ruleset | <i>media</i> | page | font_face_rule | keyframes_rule |
dbaron@7032 265 <i>supports_rule</i>
dbaron@2974 266 ;
dbaron@2974 267
dbaron@7032 268 <dfn>group_rule_body</dfn>
dbaron@7032 269 : '{' S* <i>nested_statement</i>* '}' S*
dbaron@2974 270 ;</pre>
bert@3404 271 <p>
dbaron@2974 272 in which all the productions are defined in that grammar with the
jackalmage@6839 273 exception of <code>font_face_rule</code>
dbaron@5294 274 defined in [[!CSS3-FONTS]], <code>keyframes_rule</code> defined in
jackalmage@6838 275 [[!CSS3-ANIMATIONS]], and <code>media</code> and <code>supports_rule</code>
jackalmage@6838 276 defined in this specification.</p>
dbaron@2974 277
dbaron@2974 278 <p>In general, future CSS specifications that add new @-rules that are
dbaron@2974 279 not forbidden to occur after some other types of rules should modify
dbaron@2974 280 this <code>nested_statement</code> production to keep the grammar
dbaron@2974 281 accurate.</p>
dbaron@2974 282
dbaron@2979 283 <p>Style sheets <strong>must not</strong> use rules other than the allowed ones inside
dbaron@2974 284 conditional group rules.</p>
dbaron@2974 285
dbaron@3019 286 <p>CSS processors <strong>must</strong> ignore rules that are not
dbaron@3019 287 allowed within a group rule, and <strong>must</strong> handle invalid
dbaron@3019 288 rules inside of group rules as described in <a
dbaron@3019 289 href="http://www.w3.org/TR/CSS21/syndata.html#parsing-errors">section
dbaron@3019 290 4.2 (Rules for handling parsing errors)</a>, <a
dbaron@3019 291 href="http://www.w3.org/TR/CSS21/syndata.html#at-rules">section 4.1.5
dbaron@3019 292 (At-rules)</a>, and <a
dbaron@3019 293 href="http://www.w3.org/TR/CSS21/syndata.html#rule-sets">section 4.1.7
dbaron@3019 294 (Rule sets, declaration blocks, and selectors)</a> of [[!CSS21]].</p>
dbaron@2974 295
jackalmage@6617 296 <h2 id="use">Placement of conditional group rules</h2>
dbaron@2974 297
dbaron@3019 298 <p>Conditional group rules are allowed at the top-level of a style
dbaron@3019 299 sheet, and inside other conditional group rules. CSS processors
dbaron@3019 300 <strong>must</strong> process such rules as <a
dbaron@3019 301 href="#processing">described above</a>.</p>
dbaron@3019 302
dbaron@3020 303 <p>Any rules that are not allowed after a ruleset (e.g., ''@charset'',
dbaron@3020 304 ''@import'', or ''@namespace'' rules) are also not allowed after a
dbaron@3020 305 conditional group rule. Therefore, style sheets <strong>must
dbaron@3019 306 not</strong> place such rules after a conditional group rules, and CSS
dbaron@3019 307 processors <strong>must</strong> ignore such rules.</p>
dbaron@2974 308
jackalmage@6617 309 <h2 id="at-media">Media-specific style sheets: the '@media' rule</h2>
dbaron@2974 310
dbaron@7862 311 <p>The <dfn id="atmedia-rule">'@media' rule</dfn> is a conditional group rule whose
dbaron@2974 312 condition is a media query. It consists of the at-keyword
jackalmage@6830 313 '@media' followed by a (possibly empty) media query list (as
dbaron@2974 314 defined in [[!MEDIAQ]]), followed by a group rule body. The condition
dbaron@2974 315 of the rule is the result of the media query.</p>
dbaron@2974 316
dbaron@2974 317 <div class="example">
dbaron@2983 318 <p>This '@media' rule:</p>
dbaron@7381 319 <pre>@media screen and (min-width: 35em),
dbaron@7381 320 print and (min-width: 40em) {
dbaron@7381 321 #section_navigation { float: left; width: 10em; }
dbaron@2974 322 }</pre>
dbaron@7381 323 <p>has the condition
dbaron@7381 324 ''screen and (min-width: 35em), print and (min-width: 40em)'',
dbaron@7381 325 which is true for screen displays
dbaron@7381 326 whose viewport is at least 35 times the initial font size
dbaron@7381 327 and for print displays
dbaron@7381 328 whose viewport is at least 40 times the initial font size.
dbaron@7381 329 When either of these is true,
dbaron@7381 330 the condition of the rule is true,
dbaron@7381 331 and the rule
dbaron@7381 332 ''#section_navigation { float: left; width: 10em; }''
dbaron@7381 333 is applied.</p>
dbaron@2974 334 </div>
dbaron@2974 335
dbaron@2974 336 <p>In terms of the grammar, this specification extends the
dbaron@2974 337 <code>media</code> production in the
dbaron@2974 338 <a href="http://www.w3.org/TR/CSS21/grammar.html">Grammar of CSS 2.1</a>
dbaron@2974 339 ([[!CSS21]], Appendix G) into:
dbaron@7032 340 <pre><dfn>media</dfn>
dbaron@7032 341 : MEDIA_SYM S* media_query_list <i>group_rule_body</i>
dbaron@2974 342 ;</pre>
dbaron@2974 343 <p>where the <code>group_rule_body</code> production is defined in this
dbaron@2974 344 specification, the <code>media_query_list</code> production is defined
dbaron@2974 345 in [[!MEDIAQ]], and the others are defined in the <a
dbaron@2974 346 href="http://www.w3.org/TR/CSS21/grammar.html">Grammar of CSS 2.1</a>
dbaron@2974 347 ([[!CSS21]], Appendix G).
dbaron@2974 348
jackalmage@6617 349 <h2 id="at-supports">Feature queries: the '@supports' rule</h2>
dbaron@2974 350
dbaron@7862 351 <p>The <dfn id="atsupports-rule">'@supports' rule</dfn> is a conditional group
dbaron@2974 352 rule whose condition tests whether the user agent supports CSS
dbaron@2974 353 property:value pairs. Authors can use it to write style sheets that use
dbaron@2974 354 new features when available but degrade gracefully when those features
dbaron@2974 355 are not supported. CSS has existing mechanisms for graceful
dbaron@2974 356 degradation, such as ignoring unsupported properties or values, but
dbaron@2974 357 these are not always sufficient when large groups of styles need to be
dbaron@2974 358 tied to the support for certain features, as is the case for use of new
dbaron@2974 359 layout system features.</p>
dbaron@2974 360
dbaron@2983 361 <p>The syntax of the condition in the '@supports' rule is
dbaron@2974 362 slightly more complicated than for the other conditional group rules
dbaron@2974 363 (though has some similarities to media queries) since:</p>
dbaron@2974 364 <ul>
dbaron@2974 365 <li>negation is needed so that the new-feature styles and the fallback
dbaron@2974 366 styles can be separated (within the forward-compatible grammar's rules
dbaron@2974 367 for the syntax of @-rules), and not required to override each other</li>
dbaron@2974 368 <li>conjunction (and) is needed so that multiple required features can
dbaron@2974 369 be tested</li>
dbaron@2974 370 <li>disjunction (or) is needed when there are multiple alternative
dbaron@2974 371 features for a set of styles, particularly when some of those
dbaron@2974 372 alternatives are vendor-prefixed properties or values</li>
dbaron@2974 373 </ul>
dbaron@2974 374
dbaron@2983 375 <p>Therefore, the syntax of the '@supports' rule allows
dbaron@2974 376 testing for property:value pairs, and arbitrary conjunctions (and),
dbaron@2974 377 disjunctions (or), and negations (not) of them.</p>
dbaron@2974 378
dbaron@2974 379 <p>This extends the lexical scanner in the
dbaron@2974 380 <a href="http://www.w3.org/TR/CSS21/grammar.html">Grammar of CSS 2.1</a>
dbaron@2974 381 ([[!CSS21]], Appendix G) by adding:
jackalmage@6832 382 <pre>
dbaron@7393 383 @{S}{U}{P}{P}{O}{R}{T}{S} {return <dfn>SUPPORTS_SYM</dfn>;}
dbaron@7393 384 {O}{R} {return <dfn>OR</dfn>;}
jackalmage@6832 385 </pre>
jackalmage@6943 386
dbaron@7393 387 <p>This then extends the grammar in the
dbaron@7393 388 <a href="http://www.w3.org/TR/CSS21/grammar.html">Grammar of CSS 2.1</a>,
dbaron@7393 389 using the lexical scanner there, with the additions of
dbaron@7393 390 <code><a href="http://www.w3.org/TR/css3-mediaqueries/#syntax">AND</a></code> and
dbaron@7393 391 <code><a href="http://www.w3.org/TR/css3-mediaqueries/#syntax">NOT</a></code>
dbaron@7393 392 tokens defined in the Media Queries specification [[!MEDIAQ]]
dbaron@7393 393 and the <code>OR</code> and <code>SUPPORTS_SYM</code> tokens defined above,
dbaron@7393 394 and with
dbaron@7393 395 <code><a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization">declaration</a></code>,
dbaron@7393 396 <code><a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization">any</a></code>,
dbaron@7393 397 and <code><a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization">unused</a></code>
dbaron@7393 398 productions
dbaron@7393 399 and the <code><a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization">FUNCTION</a></code> token
dbaron@7393 400 taken from the core syntax of CSS defined in
dbaron@7393 401 <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization">section 4.1.1 (Tokenization)</a> of [[!CSS21]],
dbaron@7393 402 by adding:</p>
jackalmage@6943 403
jackalmage@6315 404 <pre><dfn>supports_rule</dfn>
dbaron@7393 405 : <i>SUPPORTS_SYM</i> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <i>supports_condition</i> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <i>group_rule_body</i>
dbaron@2974 406 ;
dbaron@2974 407
jackalmage@6315 408 <dfn>supports_condition</dfn>
dbaron@7032 409 : <i>supports_negation</i> | <i>supports_conjunction</i> | <i>supports_disjunction</i> |
dbaron@7032 410 <i>supports_condition_in_parens</i>
dbaron@3957 411 ;
dbaron@3957 412
jackalmage@6315 413 <dfn>supports_condition_in_parens</dfn>
dbaron@7393 414 : ( '(' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <i>supports_condition</i> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* ')' ) | <i>supports_declaration_condition</i> |
dbaron@7032 415 <i>general_enclosed</i>
dbaron@2974 416 ;
dbaron@2974 417
jackalmage@6315 418 <dfn>supports_negation</dfn>
dbaron@7393 419 : <a href="http://www.w3.org/TR/css3-mediaqueries/#syntax"><i>NOT</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>+ <i>supports_condition_in_parens</i>
dbaron@2974 420 ;
dbaron@2974 421
jackalmage@6315 422 <dfn>supports_conjunction</dfn>
dbaron@7393 423 : <i>supports_condition_in_parens</i> ( <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>+ <a href="http://www.w3.org/TR/css3-mediaqueries/#syntax"><i>AND</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>+ <i>supports_condition_in_parens</i> )+
dbaron@2974 424 ;
dbaron@2974 425
jackalmage@6315 426 <dfn>supports_disjunction</dfn>
dbaron@7393 427 : <i>supports_condition_in_parens</i> ( <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>+ <i>OR</i> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>+ <i>supports_condition_in_parens</i> )+
dbaron@2974 428 ;
dbaron@2974 429
jackalmage@6315 430 <dfn>supports_declaration_condition</dfn>
dbaron@7393 431 : '(' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>declaration</i></a> ')'
jackalmage@6943 432 ;
jackalmage@6943 433
dbaron@7031 434 <dfn>general_enclosed</dfn>
dbaron@7393 435 : ( <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>FUNCTION</i></a> | '(' ) ( <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>any</i></a> | <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>unused</i></a> )* ')'
dbaron@7373 436 ;
dbaron@7031 437 </pre>
jackalmage@6943 438
dbaron@7031 439 <p>
dbaron@7038 440 Implementations <strong>must</strong> parse ''@supports'' rules
dbaron@7038 441 based on the above grammar,
dbaron@7038 442 and when interpreting the above grammar,
dbaron@7038 443 <strong>must</strong> match the production before an <code>|</code> operator
dbaron@7038 444 in preference to the one after it.
dbaron@7038 445 </p>
dbaron@7038 446
dbaron@7038 447 <p>
dbaron@7031 448 The above grammar is purposely very loose for forwards-compatibility reasons,
dbaron@7031 449 since the <code>general_enclosed</code> production
dbaron@7031 450 allows for substantial future extensibility.
dbaron@7033 451 Any ''@supports'' rule that does not parse according to the grammar above
dbaron@7033 452 (that is, a rule that does not match this loose grammar
dbaron@7393 453 which includes the <code>general_enclosed</code> production)
dbaron@7033 454 is invalid.
dbaron@7031 455 Style sheets <strong>must not</strong> use such a rule and
dbaron@7031 456 processors <strong>must</strong> ignore such a rule (including all of its contents).
dbaron@7031 457
dbaron@3021 458 <p>Each of these grammar terms is associated with a boolean result, as
dbaron@3021 459 follows:</p>
dbaron@2974 460 <dl>
dbaron@2974 461 <dt>supports_condition</dt>
dbaron@2974 462 <dd>
dbaron@3021 463 The result is the result of the single child term.
dbaron@2974 464 </dd>
dbaron@2974 465
dbaron@3957 466 <dt>supports_condition_in_parens</dt>
dbaron@3957 467 <dd>
dbaron@3957 468 The result is the result of the single <code>supports_condition</code>
dbaron@3957 469 or <code>supports_declaration_condition</code> child term.
dbaron@3957 470 </dd>
dbaron@3957 471
dbaron@2974 472 <dt>supports_negation</dt>
dbaron@2974 473 <dd>
dbaron@3021 474 The result is the <em>negation</em> of the result of the
dbaron@3021 475 <code>supports_condition_in_parens</code> child term.
dbaron@2974 476 </dd>
dbaron@2974 477
dbaron@2974 478 <dt>supports_conjunction</dt>
dbaron@2974 479 <dd>
dbaron@3021 480 The result is true if the result of <em>all</em> of the
dbaron@3021 481 <code>supports_condition_in_parens</code> child terms is true;
dbaron@3021 482 otherwise it is false.
dbaron@2974 483 </dd>
dbaron@2974 484
dbaron@2974 485 <dt>supports_disjunction</dt>
dbaron@2974 486 <dd>
dbaron@3021 487 The result is true if the result of <em>any</em> of the
dbaron@3021 488 <code>supports_condition_in_parens</code> child terms is true;
dbaron@3021 489 otherwise it is false.
dbaron@2974 490 </dd>
dbaron@2974 491
dbaron@2974 492 <dt>supports_declaration_condition</dt>
dbaron@2974 493 <dd>
jackalmage@6943 494 The result is whether the CSS processor <a href="#support-definition">supports</a> the declaration
fantasai@6845 495 within the parentheses.
jackalmage@6943 496 </dd>
jackalmage@6943 497
dbaron@7031 498 <dt>general_enclosed</dt>
jackalmage@6943 499 <dd>
jackalmage@6943 500 The result is always false.
dbaron@7031 501 Additionally, style sheets <strong>must not</strong>
dbaron@7031 502 write ''@supports'' rules
dbaron@7031 503 that match this grammar production.
dbaron@7031 504 (In other words, this production exists only for future extensibility,
dbaron@7031 505 and is not part of the description of a valid style sheet
dbaron@7031 506 in this level of the specification.)
dbaron@7031 507 <span class="note">Note that future levels may define functions
dbaron@7031 508 or other parenthesized expressions that can evaluate to true.</span>
dbaron@2974 509 </dd>
fantasai@7034 510 </dl>
jackalmage@6943 511
dbaron@3021 512 <p>The condition of the '@supports' rule is the result of the
dbaron@3021 513 <code>supports_condition</code> term that is a child of the
dbaron@3021 514 <code>supports_rule</code> term.</p>
dbaron@2974 515
dbaron@2982 516 <div class="example">
dbaron@2982 517 <p>For example, the following rule</p>
dbaron@2982 518 <pre>@supports ( display: flexbox ) {
dbaron@2982 519 body, #navigation, #content { display: flexbox; }
dbaron@2982 520 #navigation { background: blue; color: white; }
dbaron@2982 521 #article { background: white; color: black; }
dbaron@2982 522 }</pre>
dbaron@2983 523 <p>applies the rules inside the '@supports' rule only when
dbaron@2983 524 ''display: flexbox'' is supported.</p>
dbaron@2982 525 </div>
dbaron@2974 526
dbaron@2982 527 <div class="example">
dbaron@2982 528 <p>The following example shows an additional '@supports' rule that can
dbaron@2982 529 be used to provide an alternative for when ''display: flexbox'' is not
dbaron@2982 530 supported:</p>
dbaron@2982 531 <pre>@supports not ( display: flexbox ) {
dbaron@2982 532 body { width: 100%; height: 100%; background: white; color: black; }
dbaron@2982 533 #navigation { width: 25%; }
dbaron@2982 534 #article { width: 75%; }
dbaron@2974 535 }</pre>
dbaron@2982 536 <p>Note that the 'width' declarations may be harmful to the
dbaron@2982 537 flexbox-based layout, so it is important that they be present only in
dbaron@2982 538 the non-flexbox styles.</p>
dbaron@2982 539 </div>
dbaron@2974 540
dbaron@2982 541 <div class="example">
dbaron@2982 542 <p>The following example checks for support for the 'box-shadow'
dbaron@2982 543 property, including checking for support for vendor-prefixed versions of
dbaron@2982 544 it. When the support is present, it specifies both 'box-shadow' (with
dbaron@2982 545 the prefixed versions) and 'color' in a way what would cause the text to
dbaron@2982 546 become invisible were 'box-shadow' not supported.</p>
dbaron@2982 547 <pre>@supports ( box-shadow: 2px 2px 2px black ) or
dbaron@2982 548 ( -moz-box-shadow: 2px 2px 2px black ) or
dbaron@2974 549 ( -webkit-box-shadow: 2px 2px 2px black ) or
dbaron@2974 550 ( -o-box-shadow: 2px 2px 2px black ) {
dbaron@2982 551 .outline {
dbaron@2982 552 color: white;
dbaron@2982 553 -moz-box-shadow: 2px 2px 2px black;
dbaron@2982 554 -webkit-box-shadow: 2px 2px 2px black;
dbaron@2982 555 -o-box-shadow: 2px 2px 2px black;
dbaron@3960 556 box-shadow: 2px 2px 2px black; /* unprefixed last */
dbaron@2982 557 }
dbaron@2982 558 }</pre></div>
dbaron@2974 559
dbaron@2984 560 <p>To avoid confusion between ''and'' and ''or'', the syntax requires
dbaron@2984 561 that both ''and'' and ''or'' be specified explicitly (rather than, say,
dbaron@2984 562 using commas or spaces for one of them). Likewise, to avoid confusion
dbaron@2984 563 caused by precedence rules, the syntax does not allow ''and'', ''or'',
dbaron@2984 564 and ''not'' operators to be mixed without a layer of parentheses.</p>
dbaron@2974 565
dbaron@2984 566 <div class="example">
dbaron@2984 567 <p>For example, the following rule is not valid:
dbaron@3959 568 <pre class="illegal">@supports (transition-property: color) or
dbaron@2984 569 (animation-name: foo) and
dbaron@2984 570 (transform: rotate(10deg)) {
dbaron@2984 571 // ...
dbaron@2984 572 }</pre>
dbaron@2984 573 <p>Instead, authors must write one of the following:</p>
dbaron@2984 574 <pre>@supports ((transition-property: color) or
dbaron@2984 575 (animation-name: foo)) and
dbaron@2984 576 (transform: rotate(10deg)) {
dbaron@2984 577 // ...
dbaron@2984 578 }</pre>
dbaron@2984 579 <pre>@supports (transition-property: color) or
dbaron@3430 580 ((animation-name: foo) and
dbaron@2984 581 (transform: rotate(10deg))) {
dbaron@2984 582 // ...
dbaron@2984 583 }</pre>
dbaron@2984 584 </div>
dbaron@2974 585
dbaron@7374 586 <p>Furthermore, whitespace is required after a ''not'' and on both
dbaron@7374 587 sides of an ''and'' or ''or''.</p>
dbaron@7374 588
dbaron@3957 589 <p>The declaration being tested must always occur within parentheses,
dbaron@3957 590 when it is the only thing in the expression.<p>
dbaron@3957 591
dbaron@3957 592 <div class="example">
dbaron@3957 593 <p>For example, the following rule is not valid:
dbaron@3959 594 <pre class="illegal">@supports display: flexbox {
dbaron@3957 595 // ...
dbaron@3957 596 }</pre>
dbaron@3957 597 <p>Instead, authors must write:</p>
dbaron@3957 598 <pre>@supports (display: flexbox) {
dbaron@3957 599 // ...
dbaron@3957 600 }</pre>
dbaron@3957 601 </div>
dbaron@3957 602
dbaron@3957 603 <p>The syntax allows extra parentheses when they are not needed. This
dbaron@3957 604 flexibility is sometimes useful for authors (for example, when
dbaron@3957 605 commenting out parts of an expression) and may also be useful for
dbaron@3957 606 authoring tools.</p>
dbaron@3957 607
dbaron@3957 608 <div class="example">
dbaron@3957 609 <p>For example, authors may write:</p>
dbaron@3957 610 <pre>@supports ((display: flexbox)) {
dbaron@3957 611 // ...
dbaron@3957 612 }</pre>
dbaron@3957 613 </div>
dbaron@3957 614
jackalmage@6793 615 <p>A trailing ''!important'' on a declaration being tested is allowed,
jackalmage@6793 616 though it won't change the validity of the declaration.
jackalmage@6793 617
jackalmage@6793 618 <div class="example">
jackalmage@6793 619 <p>For example, the following rule is valid:
jackalmage@6793 620 <pre>@supports (display: flexbox !important) {
jackalmage@6793 621 // ...
jackalmage@6793 622 }</pre>
jackalmage@6793 623 </div>
dbaron@6306 624
jackalmage@6617 625 <h3 id="support-definition">Definition of support</h3>
dbaron@3021 626
dbaron@6741 627 <p>For forward-compatibility,
dbaron@6741 628 <a href="http://www.w3.org/TR/CSS21/syndata.html#declaration">section 4.1.8
dbaron@6741 629 (Declarations and properties)</a> of [[!CSS21]]
dbaron@6741 630 defines rules for handling invalid properties and values.
dbaron@6741 631 CSS processors that
dbaron@6741 632 do not implement or partially implement a specification
dbaron@6741 633 <strong>must</strong> treat any part of a value that they
dbaron@6741 634 do not implement, or
dbaron@6741 635 do not have a usable level of support for,
dbaron@6741 636 as invalid according to this rule
dbaron@6741 637 for handling invalid properties and values,
dbaron@6741 638 and therefore <strong>must</strong> discard the declaration as a parse error.</p>
dbaron@6741 639
jackalmage@6617 640 <p>A CSS processor is considered to <dfn id="dfn-support">support</dfn>
dbaron@6741 641 a declaration (consisting of a property and value) if it accepts that
dbaron@6741 642 declaration (rather than discarding it as a parse error).
dbaron@6741 643 If a processor does not implement, with a usable level of support,
dbaron@6741 644 the value given,
dbaron@6741 645 then it <strong>must not</strong>
dbaron@6741 646 accept the declaration or claim support for it.</p>
dbaron@3021 647
dbaron@7382 648 <p class="note">Note that properties or values
dbaron@7382 649 whose support is effectively disabled by user preferences
dbaron@7382 650 are still considered as supported by this definition.
dbaron@7382 651 For example, if a user has enabled a high-contrast mode
dbaron@7382 652 that causes colors to be overridden,
dbaron@7382 653 the CSS processor is still considered to support the 'color' property
dbaron@7382 654 even though declarations of the 'color' property may have no effect.
dbaron@7382 655 On the other hand, a developer-facing preference
dbaron@7382 656 whose purpose is to enable or disable support for an experimental CSS feature
dbaron@7382 657 does affect this definition of support.</p>
dbaron@7382 658
dbaron@6742 659 <p>These rules (and the equivalence between them) allow
dbaron@3021 660 authors to use fallback (either in the [[CSS1]] sense of declarations
dbaron@3021 661 that are overridden by later declarations or with the new capabilities
dbaron@3021 662 provided by the ''@supports'' rule in this specification) that works
dbaron@3021 663 correctly for the features implemented. This applies especially to
dbaron@3021 664 compound values; implementations must implement all parts of the value
dbaron@3021 665 in order to consider the declaration supported, either inside a ruleset
dbaron@3021 666 or in the declaration condition of an ''@supports'' rule.</p>
dbaron@3021 667
jackalmage@6838 668 <!--
jackalmage@6617 669 <h2 id="at-document">Document queries: the '@document' rule</h2>
dbaron@2974 670
dbaron@2983 671 <p>The <dfn>'@document' rule</dfn> is a conditional group
dbaron@3027 672 rule whose condition depends on the
dbaron@3027 673 <a href="#url-of-doc">URL of the document being styled</a>.
dbaron@2974 674 This allows style sheets, particularly user style sheets, to have styles
dbaron@2974 675 that only apply to a set of pages rather than to all pages using the
dbaron@2974 676 style sheet.</p>
dbaron@2974 677
dbaron@2974 678 <p class="issue">Given that this @-rule is intended primarily for user
dbaron@2974 679 style sheets, what should this specification say about its use in author
dbaron@2974 680 style sheets? Should it be forbidden? Should use instead be
dbaron@2974 681 discouraged? Or should this specification remain neutral on the
dbaron@2986 682 topic, since there are valid uses in author style sheets?</p>
dbaron@2974 683
jackalmage@6617 684 <p id="url-of-doc">The <dfn>URL of the document being styled</dfn> is
dbaron@3027 685 the URI at which the document is located, excluding any fragment
dbaron@3027 686 identifiers. (This means, for example, that HTTP redirects have been
dbaron@3027 687 followed.) If the styles are being applied inside a complete document
dbaron@3246 688 embedded into the presentation of another (e.g., [[HTML5]]&#39;s <code
dbaron@3027 689 class="html">iframe</code>, <code class="html">object</code>, or <code
dbaron@3027 690 class="html">img</code> elements), the relevant URI is that of the
dbaron@3027 691 frame, not of its container. However, if content from other documents
dbaron@3027 692 is mixed in via mechanisms that mix content from one document into
dbaron@3246 693 another (e.g., [[SVG11]]&#39;s <code>use</code> element), then the
dbaron@3027 694 address of the container document is used.</p>
dbaron@3027 695
dbaron@3027 696 <p class="note">Note: In [[HTML5]], this is the
fantasai@6697 697 <a href="http://dev.w3.org/html5/spec/dom.html#documents">document's address</a>
dbaron@3027 698 of a document in a
dbaron@3027 699 <a href="http://dev.w3.org/html5/spec/browsers.html#browsing-context">browsing context</a>.</p>
dbaron@3027 700
dbaron@3240 701 <div class="issue">What form of normalization is done on URLs and domains
dbaron@3240 702 before matching? In particular, this specification needs to describe:
dbaron@3240 703 <ul>
dbaron@3240 704 <li>what form is used for the <a href="#url-of-doc">URL of the document
dbaron@3240 705 being styled</a> (and what has been normalized in that form)</li>
dbaron@3240 706 <li>what normalization (if any) happens to the argument of each of the match
dbaron@3240 707 functions before the comparison that they describe and</li>
dbaron@3240 708 <li>whether the
dbaron@3240 709 comparison algorithm used is string comparison or some other URL
dbaron@3240 710 comparison algorithm.</li></ul></div>
dbaron@3027 711
dbaron@2983 712 <p>The '@document' rule's condition is written as a
dbaron@2974 713 comma-separated list of <dfn>URL matching functions</dfn>, and the
dbaron@2974 714 condition evaluates to true whenever any one of those functions
dbaron@2974 715 evaluates to true. The following URL matching functions are
dbaron@2974 716 permitted:</p>
dbaron@2974 717
dbaron@2974 718 <dl>
jackalmage@6617 719 <dt><dfn id="url-exact" title="url()|URL matching functions::exact">&lt;url&gt;</dfn></dt>
dbaron@2974 720
dbaron@2974 721 <dd>
dbaron@2983 722 <p>The 'url()' function is the <dfn>exact url matching
dbaron@3027 723 function</dfn>. It evaluates to true whenever the <a
dbaron@3027 724 href="#url-of-doc">URL of the document being styled</a> is exactly
dbaron@3027 725 the URL given.</p>
dbaron@2974 726
dbaron@2983 727 <p class="Note">The 'url()' function, since it is a core syntax
dbaron@2974 728 element in CSS, is allowed (subject to different character
dbaron@2974 729 limitations and thus escaping requirements) to contain an unquoted
dbaron@2974 730 value (in addition to the string values that are allowed as
dbaron@2974 731 arguments for all four functions).</p>
dbaron@2974 732
dbaron@2974 733 <div class="example">
dbaron@2974 734 <p>For example, this rule:</p>
dbaron@2974 735 <pre>@document url("http://www.w3.org/Style/CSS/") {
dbaron@2974 736 #summary { background: yellow; color: black}
dbaron@2974 737 }</pre>
dbaron@2983 738 <p>styles the <code class="html">summary</code> element on the page
dbaron@2974 739 <code>http://www.w3.org/Style/CSS/</code>, but not on any other
dbaron@2974 740 pages.</p>
dbaron@2974 741 </div>
dbaron@2974 742 </dd>
dbaron@2974 743
jackalmage@6617 744 <dt><dfn id="url-prefix" title="url-prefix()|URL matching functions::prefix">url-prefix(&lt;string&gt;)</dfn></dt>
dbaron@2974 745
dbaron@2974 746 <dd>
dbaron@2983 747 <p>The 'url-prefix()' function is the <dfn>url prefix
dbaron@3027 748 matching function</dfn>. It evaluates to true whenever the
dbaron@3027 749 <a href="#url-of-doc">URL of the document being styled</a>
dbaron@3027 750 has the argument to the function as an
dbaron@2974 751 initial substring (which is true when the two strings are equal).
dbaron@2974 752 When the argument is the empty string, it evaluates to true for all
dbaron@2974 753 documents.</p>
dbaron@2974 754 <div class="example">
dbaron@2974 755 <p>For example, this rule:</p>
dbaron@2974 756 <pre>@document url-prefix("http://www.w3.org/Style/CSS/") {
dbaron@2974 757 #summary { background: yellow; color: black}
dbaron@2974 758 }</pre>
dbaron@2983 759 <p>styles the <code class="html">summary</code> element on the page
dbaron@2974 760 <code>http://www.w3.org/Style/CSS/</code> and on the page
dbaron@2974 761 <code>http://www.w3.org/Style/CSS/Test</code>, but it does not
dbaron@2974 762 affect the page <code>http://www.w3.org/</code> or the page
dbaron@2974 763 <code>http://www.example.com/Style/CSS/</code>.</p>
dbaron@2974 764 </div>
dbaron@2974 765 </dd>
dbaron@2974 766
jackalmage@6617 767 <dt><dfn id="url-domain" title="domain()|URL matching functions::domain">domain(&lt;string&gt;)</dfn></dt>
dbaron@2974 768
dbaron@2974 769 <dd>
dbaron@2983 770 <p>The 'domain()' function is the <dfn>domain
dbaron@2974 771 matching function</dfn>. It evaluates to true whenever
dbaron@3027 772 the <a href="#url-of-doc">URL of the document being styled</a>
dbaron@3027 773 has a host subcomponent (as defined in [[!URI]])
dbaron@2974 774 and that host subcomponent is exactly the argument to the
dbaron@2983 775 'domain()' function or a final substring of the host
dbaron@2974 776 component is a period (U+002E) immediately followed by the argument
dbaron@2983 777 to the 'domain()' function.</p>
dbaron@2974 778 <div class="example">
dbaron@2974 779 <p>For example, this rule:</p>
dbaron@2974 780 <pre>@document domain("w3.org") {
dbaron@2974 781 body { font-size: 16px ! important }
dbaron@2974 782 }</pre>
dbaron@2974 783 <p>changes the font size of the body element for pages such as
dbaron@2974 784 <code>http://www.w3.org/Style/CSS/</code> and
dbaron@2974 785 <code>http://w3.org/Style/CSS/</code> and
dbaron@2974 786 <code>http://lists.w3.org/Archives/Public/www-style/</code>
dbaron@2974 787 but it does not affect the page
dbaron@2974 788 <code>http://www.example.com/Style/CSS/</code>.</p>
dbaron@2974 789 </div>
dbaron@2974 790 </dd>
dbaron@2974 791
jackalmage@6617 792 <dt><dfn id="url-regexp" title="regexp()|URL matching functions::regular expression">regexp(&lt;string&gt;)</dfn></dt>
dbaron@2974 793
dbaron@2974 794 <dd>
dbaron@2986 795 <p>The contents of the &lt;string&gt; argument <strong>must</strong>
dbaron@3068 796 match the JavaScript <code>Pattern</code> production
dbaron@3068 797 ([[!ECMA-262-5.1]], section 15.10.1). However,
dbaron@2986 798 failing to do so is not a CSS syntax error and does not trigger any
dbaron@2986 799 error handling for CSS syntax errors.</p>
dbaron@2986 800
dbaron@2986 801 <p>The ''regexp()'' function evaluates to true whenever the string
dbaron@2986 802 argument compiled as a JavaScript regular expression with the
dbaron@2986 803 <code>global</code>, <code>ignoreCase</code> and
dbaron@2986 804 <code>multiline</code> flags <em>disabled</em>
dbaron@3068 805 (see [[!ECMA-262-5.1]], sections 15.10.7.2 through 15.10.7.4)
dbaron@2986 806 compiles successfully and the resulting regular expression matches
dbaron@3027 807 the entirety of the
dbaron@3027 808 <a href="#url-of-doc">URL of the document being styled</a>.</p>
dbaron@2986 809
dbaron@2986 810 <p class="note">Note that regular expression must match the entire
dbaron@2986 811 URL, not just a part of it.</p>
dbaron@2974 812
dbaron@3018 813 <p class="note">Note that this definition intentionally matches the
dbaron@3018 814 behavior of the <a
dbaron@2983 815 href="http://dev.w3.org/html5/spec/common-input-element-attributes.html#attr-input-pattern"><code class="html">pattern</code>
dbaron@2983 816 attribute</a> on the <code class="html">input</code> element
dbaron@2983 817 in [[HTML5]].</p>
dbaron@2986 818
dbaron@2986 819 <div class="example">
dbaron@2986 820 <p>For example, this rule:</p>
dbaron@2986 821 <pre>@document regexp("http://www.w3.org/TR/\\d{4}/[^/]*-CSS2-\\d{8}/") {
dbaron@2986 822 body { font-size: 20px ! important }
dbaron@2986 823 }</pre>
dbaron@2986 824 <p>changes the font size of the body element for pages such as
dbaron@2986 825 <code>http://www.w3.org/TR/2011/PR-CSS2-20110412/</code>.</p>
dbaron@2986 826 <p class="note">Note that the backslashes in the regular
dbaron@2986 827 expression require CSS escaping as ''\\''.</p>
dbaron@2986 828 </div>
dbaron@2974 829 </dd>
dbaron@2974 830
dbaron@2974 831 </dl>
dbaron@2974 832
dbaron@2979 833 <p>Implementations <strong>must</strong> treat any unknown URL matching
dbaron@3045 834 functions as a syntax error, and thus ignore the '@document' rule.
dbaron@3045 835 <span class="issue">Should we instead have more complicated error
dbaron@3045 836 handling rules to make forward-compatibility work differently, or is
dbaron@3045 837 this rule the best solution for such future expansion anyway?</span></p>
dbaron@2974 838
dbaron@5293 839 <div class="issue">This syntax doesn't offer any ability to do negations,
dbaron@5293 840 which has been requested in <a
jackalmage@6617 841 href="https://bugzilla.mozilla.org/show_bug.cgi?id=349813">Mozilla bug
dbaron@5293 842 349813</a>. Use cases that people have wanted negations for
dbaron@5293 843 include:
dbaron@5293 844 <ul>
dbaron@5293 845 <li>User style sheets that want a particular rule in general, but know
dbaron@5293 846 that that rule does more harm than good on specific sites.</li>
dbaron@5293 847 <li>Authors who have a rule that they want to apply to most of their
dbaron@5293 848 pages, but wish to make a few exceptions for.</li>
dbaron@5293 849 </ul>
dbaron@5293 850 </div>
dbaron@5293 851
dbaron@2974 852 <p>This extends the lexical scanner in the
dbaron@2974 853 <a href="http://www.w3.org/TR/CSS21/grammar.html">Grammar of CSS 2.1</a>
dbaron@2974 854 ([[!CSS21]], Appendix G) by adding:
dbaron@2974 855 <pre>@{D}{O}{C}{U}{M}{E}{N}{T} {return DOCUMENT_SYM;}</pre>
dbaron@2974 856 <p>and the grammar by adding</p>
dbaron@7032 857 <pre><dfn>document_rule</dfn>
dbaron@7032 858 : DOCUMENT_SYM S+ <i>url_match_fn</i> ( "," S* <i>url_match_fn</i> )* <i>group_rule_body</i>
dbaron@2974 859 ;
dbaron@2974 860
dbaron@7032 861 <dfn>url_match_fn</dfn>
dbaron@6740 862 : (URI | FUNCTION S* STRING S* ')' ) S*
dbaron@2974 863 ;</pre>
jackalmage@6838 864 -->
jackalmage@6838 865
dbaron@2974 866
jackalmage@6617 867 <h2 id="apis">APIs</h2>
dbaron@3416 868
jackalmage@6617 869 <h3 id='extentions-to-cssrule-interface'>
jackalmage@6315 870 Extensions to the <code>CSSRule</code> interface</h3>
dbaron@3416 871
jackalmage@6315 872 <p>The <code>CSSRule</code> interface is extended as follows:
jackalmage@6315 873
jackalmage@6315 874 <pre class='idl'>partial interface CSSRule {
jackalmage@6315 875 const unsigned short SUPPORTS_RULE = 12;
jackalmage@6838 876 <!--
jackalmage@6315 877 const unsigned short DOCUMENT_RULE = 13;
jackalmage@6838 878 -->
jackalmage@6315 879 }</pre>
jackalmage@6315 880
jackalmage@6315 881
jackalmage@6655 882 <h3 id='the-cssgroupingrule-interface'>
jackalmage@6655 883 The <code>CSSGroupingRule</code> interface</h3>
jackalmage@6655 884
jackalmage@6655 885 <p>The <dfn><code>CSSGroupingRule</code></dfn> interface represents an at-rule that contains other rules nested inside itself.
jackalmage@6655 886
jackalmage@6655 887 <pre class='idl'>interface CSSGroupingRule : CSSRule {
dbaron@7102 888 readonly attribute <a href="http://www.w3.org/TR/DOM-Level-2-Style/css.html#CSS-CSSRuleList">CSSRuleList</a> cssRules;
jackalmage@6655 889 unsigned long insertRule (DOMString rule, unsigned long index);
jackalmage@6655 890 void deleteRule (unsigned long index);
jackalmage@6655 891 }</pre>
jackalmage@6655 892
jackalmage@6655 893 <dl class='idl-attributes'>
dbaron@7102 894 <dt><code>cssRules</code> of type <code><a href="http://www.w3.org/TR/DOM-Level-2-Style/css.html#CSS-CSSRuleList">CSSRuleList</a></code>, readonly
jackalmage@6655 895 <dd>The <code>cssRules</code> attribute must return a <code>CSSRuleList</code>
jackalmage@6655 896 object for the list of CSS rules nested inside the grouping rule.
jackalmage@6655 897 </dl>
jackalmage@6655 898
jackalmage@6655 899 <dl class='idl-methods'>
jackalmage@6655 900 <dt><code>insertRule(DOMString rule, unsigned long index)</code>, returns
jackalmage@6655 901 <code>unsigned long</code>
dbaron@7104 902 <dd>
dbaron@7104 903 The <code>insertRule</code> operation must
dbaron@7104 904 insert a CSS rule <var>rule</var>
dbaron@7104 905 into the CSS rule list returned by <code>cssRules</code>,
dbaron@7104 906 such that the inserted rule will be at position <var>index</var>,
dbaron@7104 907 and any rules previously at <var>index</var> or higher
dbaron@7104 908 will increase their index by one.
dbaron@7104 909 It must throw INDEX_SIZE_ERR
dbaron@7104 910 if index is greater than <code>cssRules.length</code>.
dbaron@7104 911 It must throw SYNTAX_ERR
dbaron@7104 912 if the rule has a syntax error and is unparseable;
dbaron@7104 913 this does not include syntax errors handled by error handling rules
dbaron@7412 914 for constructs inside of the rule,
dbaron@7412 915 but this does include cases where the string given
dbaron@7412 916 does not parse into a single CSS rule (such as when the string is empty)
dbaron@7412 917 or where there is anything other than whitespace or comments
dbaron@7412 918 after that single CSS rule.
dbaron@7104 919 It must throw HIERARCHY_REQUEST_ERR
dbaron@7104 920 if the rule cannot be inserted at the location specified,
dbaron@7104 921 for example, if an ''@import'' rule is inserted inside a group rule.
dbaron@7104 922
dbaron@7412 923 <p>The return value is the <var>index</var> parameter.
jackalmage@6655 924
jackalmage@6655 925 <dt><code>deleteRule (unsigned long index)</code>, return <code>void</code>
dbaron@7104 926 <dd>
dbaron@7104 927 The <code>deleteRule</code> operation must
dbaron@7104 928 remove a CSS rule from
dbaron@7104 929 the CSS rule list returned by <code>cssRules</code> at <var>index</var>.
dbaron@7104 930 It must throw INDEX_SIZE_ERR
dbaron@7104 931 if index is greater than or equal to <code>cssRules.length</code>.
jackalmage@6655 932 </dl>
jackalmage@6655 933
jackalmage@6655 934
jackalmage@6618 935 <h3 id="the-cssconditionrule-interface">
jackalmage@6618 936 The <code>CSSConditionRule</code> interface</h3>
jackalmage@6315 937
jackalmage@6620 938 <p>The <dfn><code>CSSConditionRule</code></dfn> interface represents all the "conditional" at-rules,
jackalmage@6620 939 which consist of a condition and a statement block.
dbaron@6323 940
jackalmage@6655 941 <pre class='idl'>interface CSSConditionRule : CSSGroupingRule {
dbaron@6324 942 attribute DOMString conditionText;
jackalmage@6315 943 }</pre>
jackalmage@6315 944
jackalmage@6315 945 <dl class='idl-attributes'>
dbaron@6732 946
jackalmage@6619 947 <dt><code>conditionText</code> of type <code>DOMString</code>
dbaron@6732 948 <dd>
dbaron@6732 949 <p>The <code>conditionText</code> attribute represents
dbaron@6732 950 the condition of the rule.
dbaron@6732 951 Since what this condition does
dbaron@6732 952 varies between the derived interfaces of <code>CSSConditionRule</code>,
dbaron@6732 953 those derived interfaces
dbaron@6732 954 may specify different behavior for this attribute
dbaron@6732 955 (see, for example, <code>CSSMediaRule</code> below).
dbaron@6732 956 In the absence of such rule-specific behavior,
dbaron@6732 957 the following rules apply:</p>
dbaron@6732 958
dbaron@6732 959 <p>The <code>conditionText</code> attribute, on getting, must return
jackalmage@6618 960 the result of serializing the associated condition.
jackalmage@6315 961
dbaron@6324 962 <p>On setting the <code>conditionText</code> attribute these steps
jackalmage@6315 963 must be run:
jackalmage@6315 964
jackalmage@6315 965 <ol>
jackalmage@6315 966 <li>Trim the given value of white space.
jackalmage@6315 967 <li>If the given value matches the grammar of the
jackalmage@6618 968 appropriate condition production for the given rule,
jackalmage@6618 969 replace the associated CSS condition with the given value.
jackalmage@6315 970 <li>Otherwise, do nothing.
jackalmage@6315 971 </ol>
jackalmage@6315 972 </dl>
jackalmage@6315 973
jackalmage@6618 974
jackalmage@6618 975 <h3 id="the-cssmediarule-interface">
jackalmage@6618 976 The <code>CSSMediaRule</code> interface</h3>
jackalmage@6618 977
jackalmage@6618 978 <p>The <dfn><code>CSSMediaRule</code></dfn> interface represents a ''@media'' rule:
jackalmage@6618 979
jackalmage@6618 980 <pre class='idl'>interface CSSMediaRule : CSSConditionRule {
dbaron@7102 981 readonly attribute <a href="http://www.w3.org/TR/DOM-Level-2-Style/stylesheets.html#StyleSheets-MediaList">MediaList</a> media;
jackalmage@6618 982 }</pre>
jackalmage@6618 983
jackalmage@6618 984 <dl class='idl-attributes'>
dbaron@7102 985 <dt><code>media</code> of type <code><a href="http://www.w3.org/TR/DOM-Level-2-Style/stylesheets.html#StyleSheets-MediaList">MediaList</a></code>, readonly
jackalmage@6618 986 <dd>The <code>media</code> attribute must return a <code>MediaList</code> object
jackalmage@6618 987 for the list of media queries specified with the ''@media'' rule.
jackalmage@6618 988
dbaron@7387 989 <dt><code>conditionText</code> of type <code>DOMString</code> (CSSMediaRule-specific definition for attribute on CSSConditionRule)
jackalmage@6618 990 <dd>The <code>conditionText</code> attribute (defined on the <code>CSSConditionRule</code> parent rule),
jackalmage@6618 991 on getting, must return the value of <code>media.mediaText</code> on the rule.
jackalmage@6618 992
jackalmage@6621 993 <p>Setting the <code>conditionText</code> attribute
jackalmage@6621 994 must set the <code>media.mediaText</code> attribute on the rule.
jackalmage@6621 995 </dl>
jackalmage@6618 996
jackalmage@6618 997
jackalmage@6618 998 <h3 id="the-csssupportsrule-interface">
jackalmage@6618 999 The <code>CSSSupportsRule</code> interface</h3>
jackalmage@6618 1000
jackalmage@6618 1001 <p>The <dfn><code>CSSSupportsRule</code></dfn> interface represents a ''@supports'' rule.</p>
jackalmage@6618 1002
jackalmage@6621 1003 <pre class='idl'>interface CSSSupportsRule : CSSConditionRule {
jackalmage@6618 1004 }</pre>
jackalmage@6618 1005
dbaron@7387 1006 <dl class='idl-attributes'>
dbaron@7387 1007 <dt><code>conditionText</code> of type <code>DOMString</code> (CSSSupportsRule-specific definition for attribute on CSSConditionRule)
dbaron@7387 1008 <dd>The <code>conditionText</code> attribute (defined on the <code>CSSConditionRule</code> parent rule),
dbaron@7387 1009 on getting, must return the condition that was specified,
dbaron@7387 1010 without any logical simplifications,
dbaron@7387 1011 so that the returned condition will evaluate to the same result
dbaron@7387 1012 as the specified condition
dbaron@7387 1013 in any conformant implementation of this specification
dbaron@7387 1014 (including implementations that implement future extensions
dbaron@7387 1015 allowed by the <i>general_enclosed</i> exensibility mechanism in this specification).
dbaron@7387 1016 In other words,
dbaron@7387 1017 token stream simplifications are allowed
dbaron@7387 1018 (such as reducing whitespace to a single space
dbaron@7387 1019 or omitting it in cases where it is known to be optional),
dbaron@7392 1020 but logical simplifications (such as removal of unneeded parentheses,
dbaron@7392 1021 or simplification based on evaluating results) are not allowed.
dbaron@7387 1022
dbaron@7387 1023 </dl>
dbaron@7387 1024
jackalmage@6838 1025 <!--
jackalmage@6618 1026 <h3 id="the-cssdocumentrule-interface">
jackalmage@6618 1027 The <code>CSSDocumentRule</code> interface</h3>
jackalmage@6618 1028
jackalmage@6618 1029 <p>The <dfn><code>CSSDocumentRule</code></dfn> interface represents a ''@document'' rule.</p>
jackalmage@6618 1030
jackalmage@6621 1031 <pre class='idl'>interface CSSDocumentRule : CSSConditionRule {
jackalmage@6618 1032 }</pre>
jackalmage@6838 1033 -->
jackalmage@6315 1034
jackalmage@6315 1035
jackalmage@6620 1036 <h3 id='the-css-interface'>
jackalmage@6620 1037 The <code>CSS</code> interface, and the <code title=''>supports()</code> function</h3>
jackalmage@6315 1038
jackalmage@6620 1039 <p>The <dfn id='CSS-interface'><code>CSS</code></dfn> interface holds useful CSS-related functions that do not belong elsewhere.
jackalmage@6315 1040
jackalmage@6620 1041 <pre class='idl'>interface CSS {
dbaron@7043 1042 static boolean supports(DOMString property, DOMString value);
dbaron@7105 1043 static boolean supports(DOMString conditionText);
jackalmage@6620 1044 }</pre>
jackalmage@6620 1045
jackalmage@6620 1046 <dl class='idl-methods'>
jackalmage@6620 1047 <dt><code>supports(DOMString property, DOMString value)</code>,
jackalmage@6620 1048 returns <code>boolean</code>
jackalmage@6625 1049 <dt><code>supports(DOMString conditionText)</code>,
jackalmage@6620 1050 returns <code>boolean</code>
jackalmage@6620 1051 <dd>
jackalmage@6620 1052 When the <code title=''>supports()</code> method is invoked with two arguments <var>property</var> and <var>value</var>,
jackalmage@6620 1053 it must return <code>true</code> if <var>property</var> is a literal match for the name of a CSS property that the UA supports,
jackalmage@6620 1054 and <var>value</var> would be successfully parsed as a supported value for that property.
dbaron@7390 1055 (Literal match means that no CSS escape processing is performed,
dbaron@7390 1056 and leading and trailing whitespace are not stripped,
dbaron@7390 1057 so any leading whitespace, trailing whitespace,
dbaron@7390 1058 or CSS escapes equivalent to the name of a property
dbaron@7390 1059 would cause the method to return <code>false</code>.)
jackalmage@6620 1060 Otherwise, it must return <code>false</code>.
jackalmage@6620 1061
jackalmage@6620 1062 <p>
jackalmage@6625 1063 When invoked with a single <var>conditionText</var> argument,
jackalmage@6625 1064 it must return <code>true</code> if <var>conditionText</var>,
jackalmage@6625 1065 when parsed and evaluated as a <code>supports_condition</code>,
jackalmage@6625 1066 would return true.
jackalmage@6620 1067 Otherwise, it must return <code>false</code>.
jackalmage@6620 1068 </dl>
jackalmage@6620 1069
dbaron@3417 1070
fantasai@6831 1071 <h2 class=no-num id="grammar">Grammar</h2>
fantasai@6831 1072
fantasai@6831 1073 <p>In order to allow these new @-rules in CSS style sheets, this
fantasai@6831 1074 specification modifies the <code>stylesheet</code> production in the <a
fantasai@6831 1075 href="http://www.w3.org/TR/CSS21/grammar.html">Appendix G</a> grammar of
fantasai@6831 1076 [[!CSS21]] by replacing the <code>media</code> production defined in
fantasai@6831 1077 [[!CSS21]] with the <code>media</code> production defined in this one,
jackalmage@6838 1078 and additionally inserting <code>| supports_rule</code>
fantasai@6831 1079 alongside <code>ruleset | media | page</code>.</p>
fantasai@6831 1080
fantasai@6831 1081
jackalmage@6617 1082 <h2 id="conformance">Conformance</h2>
dbaron@2974 1083
jackalmage@6617 1084 <h3 id="base-modules">Base Modules</h3>
dbaron@3022 1085
dbaron@3022 1086 <p>This specification defines conformance in terms of base modules,
dbaron@3022 1087 which are modules that this specification builds on top of. The base
dbaron@3022 1088 modules of this module are:</p>
dbaron@3022 1089
dbaron@3022 1090 <ul>
dbaron@3022 1091 <li>[[!CSS21]]</li>
dbaron@3022 1092 </ul>
dbaron@3022 1093
dbaron@3022 1094 <p>All of the conformance requirements of all base modules are
dbaron@3022 1095 incorporated as conformance requirements of this module, except where
dbaron@3022 1096 overridden by this module.</p>
dbaron@3022 1097
dbaron@3022 1098 <p>Additionally, all conformance requirements related to validity of
dbaron@3022 1099 syntax in this module and all of its base modules are to be interpreted
dbaron@3022 1100 as though all syntax in all of those modules is valid.</p>
dbaron@3022 1101
dbaron@3022 1102 <div class="example"><p>For example, this means that grammar presented
dbaron@3022 1103 in modules other than [[!CSS21]] must obey the requirements that
dbaron@3022 1104 [[!CSS21]] defines for the parsing of properties, and that requirements
dbaron@3022 1105 for handling invalid syntax in [[!CSS21]] do not treat syntax added by
dbaron@3022 1106 other modules as invalid.</p></div>
dbaron@3022 1107
dbaron@3022 1108 <p>Additionally, the set of valid syntax can be increased by the
dbaron@3022 1109 conformance of a style sheet or processor to additional modules; use of
dbaron@3022 1110 such syntax does not make a style sheet nonconformant and failure to
dbaron@3022 1111 treat such syntax as invalid does not make a processor
dbaron@3022 1112 nonconformant.</p>
dbaron@3022 1113
jackalmage@6617 1114 <h3 id="conformance-classes">Conformance Classes</h3>
dbaron@2974 1115
dbaron@2974 1116 <p>Conformance to the CSS Conditional Rules Module is defined for three
dbaron@2974 1117 conformance classes:
dbaron@2974 1118 <dl>
jackalmage@6617 1119 <dt><dfn title="conformance::style sheet" id="conform-style-sheet">style sheet</dfn>
dbaron@2974 1120 <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS
dbaron@3022 1121 style sheet</a>.</dd>
jackalmage@6617 1122 <dt><dfn title="conformance::processor" id="conform-processor">processor</dfn></dt>
dbaron@3022 1123 <dd>A tool that reads CSS style sheets: it may be a renderer or
dbaron@3022 1124 <a
dbaron@3022 1125 href="http://www.w3.org/TR/CSS21/conform.html#user-agent">user-agent</a>
dbaron@2974 1126 that interprets the semantics of a style sheet and renders
dbaron@3022 1127 documents that use style sheets, or it may be a validator that
dbaron@3022 1128 checks style sheets.</dd>
jackalmage@6617 1129 <dt><dfn title="conformance::authoring tool" id="conform-authoring-tool">authoring tool</dfn></dt>
dbaron@3022 1130 <dd>A tool that writes a style sheet.</dd>
dbaron@2974 1131 </dl>
dbaron@3022 1132
dbaron@3022 1133 <p>A style sheet is conformant to the CSS Conditional Rules Module
dbaron@3022 1134 if it meets all of the conformance requirements in the module that are
dbaron@3022 1135 described as requirements of style sheets.</p>
dbaron@3022 1136
dbaron@3022 1137 <p>A processor is conformant to the CSS Conditional Rules Module if it
dbaron@3022 1138 meets all applicable conformance requirements in the module that are
dbaron@3022 1139 described as requirements of processors. In general, all requirements
dbaron@3022 1140 are applicable to renderers. Requirements concerning a part of CSS
dbaron@3022 1141 not performed by a processor are not applicable, e.g., requirements
dbaron@3022 1142 related to rendering are not applicable to a validator. The inability
dbaron@3022 1143 of a processor to correctly render a document due to limitations of
dbaron@3022 1144 the device does not make it non-conformant. (For example, a renderer
dbaron@3022 1145 is not required to render color on a monochrome monitor.)</p>
dbaron@3022 1146
dbaron@3022 1147 <p>An authoring tool is conformant to the CSS Conditional Rules Module
dbaron@3022 1148 if it writes style sheets that conform to the module and (if it reads
dbaron@3022 1149 CSS) it is a conformant processor.</p>
dbaron@2974 1150
jackalmage@6617 1151 <h3 id="partial">
dbaron@2974 1152 Partial Implementations</h3>
dbaron@2974 1153
dbaron@2974 1154 <p>So that authors can exploit the forward-compatible parsing rules to
dbaron@2974 1155 assign fallback values, CSS renderers <strong>must</strong>
dbaron@2974 1156 treat as invalid (and <a href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignore
dbaron@2974 1157 as appropriate</a>) any at-rules, properties, property values, keywords,
dbaron@2974 1158 and other syntactic constructs for which they have no usable level of
dbaron@2974 1159 support. In particular, user agents <strong>must not</strong> selectively
dbaron@2974 1160 ignore unsupported component values and honor supported values in a single
dbaron@2974 1161 multi-value property declaration: if any value is considered invalid
dbaron@2974 1162 (as unsupported values must be), CSS requires that the entire declaration
dbaron@2974 1163 be ignored.</p>
dbaron@2974 1164
jackalmage@6617 1165 <h3 id="experimental">Experimental Implementations</h3>
dbaron@2974 1166
dbaron@2974 1167 <p>To avoid clashes with future CSS features, the CSS specifications
dbaron@2974 1168 reserve a <a href="http://www.w3.org/TR/CSS21/syndata.html#vendor-keywords">prefixed
dbaron@2974 1169 syntax</a> for proprietary property and value extensions to CSS. The CSS
dbaron@2974 1170 Working Group recommends that experimental implementations of features in
dbaron@2974 1171 CSS Working Drafts also use vendor-prefixed property or value names. This
dbaron@2974 1172 avoids any incompatibilities with future changes in the draft. Once a
dbaron@2974 1173 specification reaches the Candidate Recommendation stage, implementors
dbaron@2974 1174 should implement the non-prefixed syntax for any feature they consider to
dbaron@2974 1175 be correctly implemented according to spec.</p>
dbaron@2974 1176
jackalmage@6617 1177 <h3 id="cr-exit-criteria">CR Exit Criteria</h3>
dbaron@2974 1178
dbaron@3244 1179 <p>For this specification to be advanced to Proposed Recommendation,
dbaron@2974 1180 there must be at least two independent, interoperable implementations
dbaron@2974 1181 of each feature. Each feature may be implemented by a different set of
dbaron@2974 1182 products, there is no requirement that all features be implemented by
dbaron@2974 1183 a single product. For the purposes of this criterion, we define the
dbaron@2974 1184 following terms:
dbaron@2974 1185
dbaron@2974 1186 <dl>
dbaron@2974 1187 <dt>independent <dd>each implementation must be developed by a
dbaron@2974 1188 different party and cannot share, reuse, or derive from code
dbaron@2974 1189 used by another qualifying implementation. Sections of code that
dbaron@2974 1190 have no bearing on the implementation of this specification are
dbaron@2974 1191 exempt from this requirement.
dbaron@2974 1192
dbaron@2974 1193 <dt>interoperable <dd>passing the respective test case(s) in the
dbaron@2974 1194 official CSS test suite, or, if the implementation is not a Web
dbaron@2974 1195 browser, an equivalent test. Every relevant test in the test
dbaron@2974 1196 suite should have an equivalent test created if such a user
dbaron@2974 1197 agent (UA) is to be used to claim interoperability. In addition
dbaron@2974 1198 if such a UA is to be used to claim interoperability, then there
dbaron@2974 1199 must one or more additional UAs which can also pass those
dbaron@2974 1200 equivalent tests in the same way for the purpose of
dbaron@2974 1201 interoperability. The equivalent tests must be made publicly
dbaron@2974 1202 available for the purposes of peer review.
dbaron@2974 1203
dbaron@2974 1204 <dt>implementation <dd>a user agent which:
dbaron@2974 1205
dbaron@2974 1206 <ol class=inline>
dbaron@2974 1207 <li>implements the specification.
dbaron@2974 1208
dbaron@2974 1209 <li>is available to the general public. The implementation may
dbaron@2974 1210 be a shipping product or other publicly available version
dbaron@2974 1211 (i.e., beta version, preview release, or “nightly build”).
dbaron@2974 1212 Non-shipping product releases must have implemented the
dbaron@2974 1213 feature(s) for a period of at least one month in order to
dbaron@2974 1214 demonstrate stability.
dbaron@2974 1215
dbaron@2974 1216 <li>is not experimental (i.e., a version specifically designed
dbaron@2974 1217 to pass the test suite and is not intended for normal usage
dbaron@2974 1218 going forward).
dbaron@2974 1219 </ol>
dbaron@2974 1220 </dl>
dbaron@2974 1221
dbaron@2974 1222 <p>The specification will remain Candidate Recommendation for at least
dbaron@2974 1223 six months.
dbaron@2974 1224
fantasai@6831 1225 <h2 id="changes">
fantasai@6831 1226 Changes</h2>
dbaron@2974 1227
fantasai@6831 1228 <p>The following (non-editorial) changes were made to this specification since the
dbaron@7734 1229 <a href="http://www.w3.org/TR/2012/WD-css3-conditional-20121213/">13 December 2012 Working Draft</a>:
fantasai@6831 1230
fantasai@6831 1231 <ul>
dbaron@7734 1232 <li>Require whitespace around ''and'' and ''or'' and after ''not''.
dbaron@7734 1233 <li>Add note explaining that user preferences that effectively disable a property (e.g., high-contrast mode disabling colors) do not effect the definition of support.
dbaron@7734 1234 <li>Describe requirements for conditionText getter on CSSSupportsRule.
dbaron@7734 1235 <li>Clarify the definition of "literal match" in CSS.supports().
dbaron@7734 1236 <li>Specify behavior of CSSGroupingRule.insertRule when given an empty string or more than one syntactically valid rule.
fantasai@6831 1237 </ul>
dbaron@2974 1238
jackalmage@6617 1239 <h2 class=no-num id="acknowledgments">Acknowledgments</h2>
dbaron@2974 1240
dbaron@2974 1241 <p>
dbaron@2974 1242 Thanks to the ideas and feedback from
dbaron@3418 1243 Tab Atkins,
dbaron@7389 1244 Arthur Barstow,
dbaron@7389 1245 Ben Callahan,
dbaron@2974 1246 <span lang="tr">Tantek Çelik</span>,
dbaron@3418 1247 Alex Danilo,
dbaron@2974 1248 Elika Etemad,
dbaron@2974 1249 Pascal Germroth,
dbaron@2974 1250 <span lang="de">Björn Höhrmann</span>,
dbaron@3417 1251 Paul Irish,
dbaron@7044 1252 <span lang="nl">Anne van Kesteren</span>,
dbaron@3418 1253 Vitor Menezes,
dbaron@2977 1254 Alex Mogilevsky,
dbaron@2974 1255 Chris Moschini,
dbaron@7389 1256 James Nurthen,
dbaron@7389 1257 Simon Pieters,
dbaron@7389 1258 <span lang="fr">Florian Rivoal</span>,
dbaron@7389 1259 <span lang="fr">Simon Sapin</span>,
dbaron@7389 1260 Nicholas Shanks,
dbaron@2974 1261 Ben Ward,
dbaron@2974 1262 Zack Weinberg,
dbaron@3430 1263 Estelle Weyl,
dbaron@2974 1264 Boris Zbarsky,
dbaron@2974 1265 and all the rest of the <a href="http://lists.w3.org/Archives/Public/www-style/">www-style</a> community.
dbaron@2974 1266
dbaron@2974 1267 </p>
dbaron@2974 1268
jackalmage@6617 1269 <h2 class=no-num id="references">References</h2>
dbaron@2974 1270
dbaron@2974 1271
jackalmage@6617 1272 <h3 class="no-num" id="normative-references">Normative references</h3>
dbaron@2974 1273 <!--normative-->
dbaron@2974 1274
jackalmage@6617 1275 <h3 class="no-num" id="other-references">Other references</h3>
dbaron@2974 1276 <!--informative-->
dbaron@2974 1277
jackalmage@6617 1278 <h2 class="no-num" id="index">Index</h2>
dbaron@2974 1279 <!--index-->
dbaron@2974 1280
dbaron@2974 1281 </body>
dbaron@2974 1282 </html>
dbaron@2974 1283 <!-- Keep this comment at the end of the file
dbaron@2974 1284 Local variables:
dbaron@2974 1285 mode: sgml
dbaron@2974 1286 sgml-declaration:"~/SGML/HTML4.decl"
dbaron@2974 1287 sgml-default-doctype-name:"html"
dbaron@2974 1288 sgml-minimize-attributes:t
dbaron@2974 1289 sgml-nofill-elements:("pre" "style" "br")
dbaron@2974 1290 sgml-live-element-indicator:t
dbaron@2974 1291 sgml-omittag:nil
dbaron@2974 1292 sgml-shorttag:nil
dbaron@2974 1293 sgml-namecase-general:t
dbaron@2974 1294 sgml-general-insert-case:lower
dbaron@2974 1295 sgml-always-quote-attributes:t
dbaron@2974 1296 sgml-indent-step:nil
dbaron@2974 1297 sgml-indent-data:t
dbaron@2974 1298 sgml-parent-document:nil
dbaron@2974 1299 sgml-exposed-tags:nil
dbaron@2974 1300 sgml-local-catalogs:nil
dbaron@2974 1301 sgml-local-ecat-files:nil
dbaron@2974 1302 End:
dbaron@2974 1303 -->
dbaron@2974 1304

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