css3-conditional/Overview.src.html

Thu, 06 Dec 2012 18:31:02 -0800

author
L. David Baron <dbaron@dbaron.org>
date
Thu, 06 Dec 2012 18:31:02 -0800
changeset 7104
11b7f2371aa3
parent 7102
a639091a0368
child 7105
4f6f1a7462fc
permissions
-rw-r--r--

[css3-conditional] define insertRule and deleteRule more precisely

This should address feedback in
http://lists.w3.org/Archives/Public/www-style/2012Nov/0330.html

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">
dbaron@2974 8 <link rel="stylesheet" type="text/css"
dbaron@2974 9 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>
dbaron@2974 15
dbaron@2974 16 <div class="head">
dbaron@2974 17 <!--logo-->
dbaron@2974 18
dbaron@2974 19 <h1>CSS Conditional Rules Module Level 3</h1>
dbaron@2974 20
dbaron@2974 21 <h2 class="no-num no-toc">[LONGSTATUS] [DATE]</h2>
dbaron@2974 22 <dl>
dbaron@2974 23 <dt>This version:
dbaron@2974 24 <dd><a href="[VERSION]">
fantasai@7042 25 http://www.w3.org/TR/[YEAR]/WD-css3-conditional-[CDATE]/</a>
dbaron@2974 26
dbaron@2974 27 <dt>Latest version:
dbaron@3241 28 <dd><a href="http://www.w3.org/TR/[SHORTNAME]/">http://www.w3.org/TR/[SHORTNAME]/</a>
dbaron@2974 29
dbaron@3245 30 <dt>Editor's draft:
bert@3404 31 <dd><a href="http://dev.w3.org/csswg/[SHORTNAME]/">http://dev.w3.org/csswg/[SHORTNAME]/</a>
dbaron@3245 32
dbaron@2974 33 <dt>Previous version:
fantasai@6831 34 <dd><a href="http://www.w3.org/TR/2012/WD-css3-conditional-20120911/">http://www.w3.org/TR/2012/WD-css3-conditional-20120911/</a></dd>
dbaron@2974 35
dbaron@2974 36 <dt>Editors:
dbaron@2974 37 <dd class=vcard><a class=fn href="http://dbaron.org/">L. David Baron</a>,
dbaron@6308 38 <a class=org href="http://www.mozilla.org/">Mozilla</a>
dbaron@3744 39
dbaron@3744 40 <dt>Issues list:
dbaron@3744 41 <dd>Maintained in document (only editor's draft is current)
dbaron@3744 42
fantasai@6697 43 <dt>Feedback:
fantasai@6697 44
fantasai@6697 45 <dd><a
fantasai@6697 46 href="http://lists.w3.org/Archives/Public/www-style/">www-style@w3.org</a>
dbaron@6738 47 with subject line “<kbd>&#x5b;[SHORTNAME]&#x5d; <var>… message topic
fantasai@6697 48 …</var></kbd>”
dbaron@3744 49
dbaron@3744 50 <dt>Test suite:
dbaron@6115 51 <dd><a href="https://test.csswg.org/shepherd/search/spec/css3-conditional/">submitted tests</a>; no built test suite yet
dbaron@3744 52
dbaron@2974 53 </dl>
dbaron@2974 54
dbaron@2974 55 <!--copyright-->
dbaron@2974 56
dbaron@2974 57 <hr title="Separator for header">
dbaron@2974 58 </div>
dbaron@2974 59
jackalmage@6617 60 <h2 class="no-num no-toc" id="abstract">Abstract</h2>
dbaron@2974 61
dbaron@2974 62 <p>CSS is a language for describing the rendering of structured documents
dbaron@2974 63 (such as HTML and XML) on screen, on paper, in speech, etc. This module
dbaron@2974 64 contains the features of CSS for conditional processing of parts of
dbaron@2974 65 style sheets, conditioned on capabilities of the processor or the
dbaron@2974 66 document the style sheet is being applied to.
dbaron@2974 67 It includes and extends the functionality of CSS level&nbsp;2 [[!CSS21]],
dbaron@2974 68 which builds on CSS level&nbsp;1 [[CSS1]].
dbaron@2974 69 The main extensions compared to level&nbsp;2 are
dbaron@2983 70 allowing nesting of certain at-rules inside '@media',
jackalmage@6838 71 and the addition of the '@supports'
jackalmage@6838 72 rule for conditional processing.
dbaron@2974 73
jackalmage@6617 74 <h2 class="no-num no-toc" id="status">Status of this document</h2>
dbaron@2974 75
dbaron@2974 76 <!--status-->
dbaron@2974 77
dbaron@2974 78 <p>The following features are at risk:
dbaron@2974 79 <ul>
dbaron@2983 80 <li>The inclusion of '@font-face' rules and
dbaron@2983 81 '@keyframes' rules as allowed within all of the @-rules in
dbaron@2974 82 this specification is at risk, though only because of the relative
dbaron@2974 83 rates of advancement of specifications. If this specification is able
dbaron@2974 84 to advance faster than one or both of the specifications defining
dbaron@2974 85 those rules, then the inclusion of those rules will move from this
dbaron@2974 86 specification to the specification defining those rules.</li>
dbaron@2974 87
dbaron@2974 88 <li>The addition of support for @-rules inside of conditional grouping
dbaron@2974 89 rules is at risk; if interoperable implementations are not found, it
dbaron@2974 90 may be removed to advance the other features in this specification to
dbaron@2974 91 Proposed Recommendation.</li>
dbaron@2974 92
dbaron@2983 93 <li>The '@supports' rule is at risk; if interoperable
dbaron@2974 94 implementations are not found, it may be removed to advance the other
dbaron@2974 95 features in this specification to Proposed Recommendation.</li>
jackalmage@6838 96 </ul>
jackalmage@6837 97
fantasai@7042 98 <p>This is a <strong>Last Call Working Draft</strong>.
fantasai@7042 99 The deadline for comments is <strong>18 December 2012</strong>.
fantasai@7042 100
jackalmage@6838 101 <!--
dbaron@2974 102
jackalmage@6838 103 Things to go in level 4:
jackalmage@6838 104
jackalmage@6838 105 * Create some way to put these new conditional things on an @import.
jackalmage@6838 106 * The @document rule (commented out, down below).
jackalmage@6838 107
jackalmage@6838 108 -->
dbaron@2974 109
jackalmage@6617 110 <h2 class="no-num no-toc" id="contents">Table of contents</h2>
dbaron@2974 111
dbaron@2974 112 <!--toc-->
dbaron@2974 113
jackalmage@6617 114 <h2 id="introduction">Introduction</h2>
dbaron@2974 115
jackalmage@6617 116 <h3 id="context">Background</h3>
dbaron@2974 117
dbaron@2974 118 <p><em>This section is not normative.</em>
dbaron@2974 119
dbaron@2974 120 <p>[[!CSS21]] defines one type of conditional group rule, the
dbaron@2983 121 '@media' rule, and allows only rulesets (not other @-rules)
dbaron@2983 122 inside of it. The '@media' rule provides the ability to
dbaron@2974 123 have media-specific style sheets, which is also provided by style
dbaron@2983 124 sheet linking features such as '@import' and
dbaron@2983 125 <code class="html">&lt;link&gt;</code>. The restrictions on the contents of
dbaron@2983 126 '@media' rules made them less useful; they have forced authors
dbaron@2974 127 using CSS features involving @-rules in media-specific style sheets to
dbaron@2974 128 use separate style sheets for each medium.</p>
dbaron@2974 129
dbaron@2974 130 <p>This specification extends the rules for the contents of
dbaron@2974 131 conditional group rules to allow other @-rules, which enables authors
dbaron@2974 132 to combine CSS features involving @-rules with media specific style
dbaron@2974 133 sheets within a single style sheet.</p>
dbaron@2974 134
jackalmage@6838 135 <p>This specification also defines an additional type of conditional
jackalmage@6838 136 group rule, '@supports', to
dbaron@2974 137 address author and user requirements.</p>
dbaron@2974 138
dbaron@2983 139 <p>The '@supports' rule allows CSS to be conditioned on
dbaron@2974 140 implementation support for CSS properties and values. This rule makes
dbaron@2974 141 it much easier for authors to use new CSS features and provide good
dbaron@2974 142 fallback for implementations that do not support those features. This
dbaron@2974 143 is particularly important for CSS features that provide new layout
dbaron@2974 144 mechanisms, and for other cases where a set of related styles needs to
dbaron@2974 145 be conditioned on property support.</p>
dbaron@2974 146
jackalmage@6617 147 <h3 id="placement">Module Interactions</h3>
dbaron@2974 148
dbaron@2983 149 <p>This module replaces and extends the '@media' rule
dbaron@2974 150 feature defined in [[!CSS21]] section <var>7.2.1</var> and
dbaron@2974 151 incorporates the modifications previously made non-normatively by
dbaron@2974 152 [[!MEDIAQ]] section <var>1</var>.</p>
dbaron@2974 153
dbaron@3462 154 <p>Its current definition depends on @-rules defined in [[!CSS3-FONTS]]
dbaron@2974 155 and [[!CSS3-ANIMATIONS]], but that dependency is only on the
dbaron@2974 156 assumption that those modules will advance ahead of this one. If this
dbaron@2974 157 module advances faster, then the dependency will be reversed.</p>
dbaron@2974 158
jackalmage@6617 159 <h3 id="conventions">Document Conventions</h3>
dbaron@2974 160
dbaron@2974 161 <p>Conformance requirements are expressed with a combination of
dbaron@2974 162 descriptive assertions and RFC 2119 terminology. The key words “MUST”,
dbaron@2974 163 “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”,
dbaron@2974 164 “RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this
dbaron@2974 165 document are to be interpreted as described in RFC 2119.
dbaron@2979 166 However, for readability, these words do not appear in all uppercase
dbaron@2979 167 letters in this specification.
dbaron@2974 168
dbaron@2974 169 <p>All of the text of this specification is normative except sections
dbaron@2974 170 explicitly marked as non-normative, examples, and notes. [[!RFC2119]]</p>
dbaron@2974 171
dbaron@2974 172 <p>Examples in this specification are introduced with the words “for example”
dbaron@2983 173 or are set apart from the normative text with
dbaron@2983 174 <code class="html">class="example"</code>, like this:
dbaron@2974 175
dbaron@2974 176 <div class="example">
dbaron@2974 177 <p>This is an example of an informative example.</p>
dbaron@2974 178 </div>
dbaron@2974 179
dbaron@2974 180 <p>Informative notes begin with the word “Note” and are set apart from the
dbaron@2983 181 normative text with <code class="html">class="note"</code>, like this:
dbaron@2974 182
dbaron@2974 183 <p class="note">Note, this is an informative note.</p>
dbaron@2974 184
jackalmage@6617 185 <h2 id="processing">Processing of conditional group rules</h2>
dbaron@2974 186
dbaron@2974 187 <p>This specification defines some CSS @-rules, called <dfn>conditional
dbaron@2974 188 group rules</dfn>, that associate a condition with a group of other
dbaron@2974 189 CSS rules. These different rules allow testing different types of
dbaron@2974 190 conditions, but share common behavior for how their contents are used
dbaron@2974 191 when the condition is true and when the condition is false.</p>
dbaron@2974 192
dbaron@2974 193 <div class="example">
dbaron@2974 194 <p>For example, this rule:</p>
dbaron@2974 195 <pre>@media print {
dbaron@2974 196 #navigation { display: none }
dbaron@2974 197 }</pre>
dbaron@2974 198 <p>causes a particular CSS rule (making elements with ID "navigation" be
dbaron@2974 199 display:none) apply only when the style sheet is used for a print
jackalmage@6838 200 medium.
dbaron@2974 201 </div>
dbaron@2974 202
dbaron@2974 203 <p>Each conditional group rule has a condition, which at any time
dbaron@2974 204 evaluates to true or false. When the condition is true, CSS processors
dbaron@2979 205 <strong>must</strong> apply the rules inside the group rule as though
dbaron@2979 206 they were at the group rule's location; when the condition is false, CSS
dbaron@3948 207 processors <strong>must not</strong> apply any of rules inside the group
dbaron@2979 208 rule. The current state of the condition does not affect the CSS object
dbaron@2979 209 model, in which the contents of the group rule always remain within the
dbaron@2979 210 group rule.</p>
dbaron@2974 211
dbaron@2974 212 <p>This means that when multiple conditional group rules are nested,
dbaron@2974 213 a rule inside of both of them applies only when all of the rules'
dbaron@2974 214 conditions are true.</p>
dbaron@2974 215
dbaron@2974 216 <div class="example">For example, with this set of nested rules:
dbaron@2974 217 <pre>@media print { // rule (1)
dbaron@2974 218 #navigation { display: none }
dbaron@2974 219 @media (max-width: 12cm) { // rule (2)
dbaron@2974 220 .note { float: none }
dbaron@2974 221 }
dbaron@2974 222 }</pre>
dbaron@2974 223 the condition of the rule marked (1) is true for print media, and the
dbaron@2974 224 condition of the rule marked (2) is true when the width of the display
dbaron@2974 225 area (which for print media is the page box) is less than or equal to
dbaron@2983 226 12cm. Thus the rule ''#navigation { display: none }'' applies
dbaron@2974 227 whenever this style sheet is applied to print media, and the rule
dbaron@2983 228 ''.note { float: none }'' is applied only when the style sheet
dbaron@2974 229 is applied to print media <em>and</em> the width of the page box is less
dbaron@2974 230 than or equal to 12 centimeters.</div>
dbaron@2974 231
dbaron@2979 232 <p>When the condition for a conditional group rule changes, CSS
dbaron@2979 233 processors <strong>must</strong> reflect that the rules now apply or no
dbaron@2979 234 longer apply, except for properties whose definitions define effects of
dbaron@2979 235 computed values that persist past the lifetime of that value (such as
dbaron@2979 236 for some properties in [[CSS3-TRANSITIONS]] and
dbaron@2979 237 [[!CSS3-ANIMATIONS]]).</p>
dbaron@2974 238
jackalmage@6617 239 <h2 id="contents-of">Contents of conditional group rules</h2>
dbaron@2974 240
dbaron@2974 241 <p>The syntax of each conditional group rule consists of some syntax
dbaron@2974 242 specific to the type of rule followed by a <dfn>group rule body</dfn>,
dbaron@2974 243 which is a block (pair of braces) containing a sequence of rules.</p>
dbaron@2974 244
dbaron@2974 245 <p>A group rule body is allowed to contain rulesets and any @-rules that
dbaron@2974 246 are allowed at the top level of a style sheet before and after a
dbaron@2974 247 ruleset. This means that @-rules that must occur at the beginning of
dbaron@3020 248 the style sheet (such as '@charset', '@import',
dbaron@3020 249 and '@namespace' rules) are not allowed inside of conditional group
dbaron@2974 250 rules. Conditional group rules can be nested.</p>
dbaron@2974 251
dbaron@2974 252 <p>In terms of the grammar, this specification defines the following
dbaron@2974 253 productions for use in the grammar of conditional group rules:</p>
dbaron@2974 254
dbaron@7032 255 <pre><dfn>nested_statement</dfn>
dbaron@7032 256 : ruleset | <i>media</i> | page | font_face_rule | keyframes_rule |
dbaron@7032 257 <i>supports_rule</i>
dbaron@2974 258 ;
dbaron@2974 259
dbaron@7032 260 <dfn>group_rule_body</dfn>
dbaron@7032 261 : '{' S* <i>nested_statement</i>* '}' S*
dbaron@2974 262 ;</pre>
bert@3404 263 <p>
dbaron@2974 264 in which all the productions are defined in that grammar with the
jackalmage@6839 265 exception of <code>font_face_rule</code>
dbaron@5294 266 defined in [[!CSS3-FONTS]], <code>keyframes_rule</code> defined in
jackalmage@6838 267 [[!CSS3-ANIMATIONS]], and <code>media</code> and <code>supports_rule</code>
jackalmage@6838 268 defined in this specification.</p>
dbaron@2974 269
dbaron@2974 270 <p>In general, future CSS specifications that add new @-rules that are
dbaron@2974 271 not forbidden to occur after some other types of rules should modify
dbaron@2974 272 this <code>nested_statement</code> production to keep the grammar
dbaron@2974 273 accurate.</p>
dbaron@2974 274
dbaron@2979 275 <p>Style sheets <strong>must not</strong> use rules other than the allowed ones inside
dbaron@2974 276 conditional group rules.</p>
dbaron@2974 277
dbaron@3019 278 <p>CSS processors <strong>must</strong> ignore rules that are not
dbaron@3019 279 allowed within a group rule, and <strong>must</strong> handle invalid
dbaron@3019 280 rules inside of group rules as described in <a
dbaron@3019 281 href="http://www.w3.org/TR/CSS21/syndata.html#parsing-errors">section
dbaron@3019 282 4.2 (Rules for handling parsing errors)</a>, <a
dbaron@3019 283 href="http://www.w3.org/TR/CSS21/syndata.html#at-rules">section 4.1.5
dbaron@3019 284 (At-rules)</a>, and <a
dbaron@3019 285 href="http://www.w3.org/TR/CSS21/syndata.html#rule-sets">section 4.1.7
dbaron@3019 286 (Rule sets, declaration blocks, and selectors)</a> of [[!CSS21]].</p>
dbaron@2974 287
jackalmage@6617 288 <h2 id="use">Placement of conditional group rules</h2>
dbaron@2974 289
dbaron@3019 290 <p>Conditional group rules are allowed at the top-level of a style
dbaron@3019 291 sheet, and inside other conditional group rules. CSS processors
dbaron@3019 292 <strong>must</strong> process such rules as <a
dbaron@3019 293 href="#processing">described above</a>.</p>
dbaron@3019 294
dbaron@3020 295 <p>Any rules that are not allowed after a ruleset (e.g., ''@charset'',
dbaron@3020 296 ''@import'', or ''@namespace'' rules) are also not allowed after a
dbaron@3020 297 conditional group rule. Therefore, style sheets <strong>must
dbaron@3019 298 not</strong> place such rules after a conditional group rules, and CSS
dbaron@3019 299 processors <strong>must</strong> ignore such rules.</p>
dbaron@2974 300
jackalmage@6617 301 <h2 id="at-media">Media-specific style sheets: the '@media' rule</h2>
dbaron@2974 302
dbaron@2983 303 <p>The <dfn>'@media' rule</dfn> is a conditional group rule whose
dbaron@2974 304 condition is a media query. It consists of the at-keyword
jackalmage@6830 305 '@media' followed by a (possibly empty) media query list (as
dbaron@2974 306 defined in [[!MEDIAQ]]), followed by a group rule body. The condition
dbaron@2974 307 of the rule is the result of the media query.</p>
dbaron@2974 308
dbaron@2974 309 <div class="example">
dbaron@2983 310 <p>This '@media' rule:</p>
dbaron@2974 311 <pre>@media print, (max-width: 600px) {
dbaron@2974 312 #extra_navigation { display: none }
dbaron@2974 313 }</pre>
dbaron@2983 314 <p>has the condition ''print, (max-width: 600px)'', which is
dbaron@2974 315 true for print media and for devices whose width is at most 600px. When
dbaron@2979 316 either of these is true, the condition of the rule is true, and the rule
dbaron@2983 317 ''#extra_navigation { display: none }'' is applied.
dbaron@2974 318 </div>
dbaron@2974 319
dbaron@2974 320 <p>In terms of the grammar, this specification extends the
dbaron@2974 321 <code>media</code> production in the
dbaron@2974 322 <a href="http://www.w3.org/TR/CSS21/grammar.html">Grammar of CSS 2.1</a>
dbaron@2974 323 ([[!CSS21]], Appendix G) into:
dbaron@7032 324 <pre><dfn>media</dfn>
dbaron@7032 325 : MEDIA_SYM S* media_query_list <i>group_rule_body</i>
dbaron@2974 326 ;</pre>
dbaron@2974 327 <p>where the <code>group_rule_body</code> production is defined in this
dbaron@2974 328 specification, the <code>media_query_list</code> production is defined
dbaron@2974 329 in [[!MEDIAQ]], and the others are defined in the <a
dbaron@2974 330 href="http://www.w3.org/TR/CSS21/grammar.html">Grammar of CSS 2.1</a>
dbaron@2974 331 ([[!CSS21]], Appendix G).
dbaron@2974 332
jackalmage@6617 333 <h2 id="at-supports">Feature queries: the '@supports' rule</h2>
dbaron@2974 334
dbaron@2983 335 <p>The <dfn>'@supports' rule</dfn> is a conditional group
dbaron@2974 336 rule whose condition tests whether the user agent supports CSS
dbaron@2974 337 property:value pairs. Authors can use it to write style sheets that use
dbaron@2974 338 new features when available but degrade gracefully when those features
dbaron@2974 339 are not supported. CSS has existing mechanisms for graceful
dbaron@2974 340 degradation, such as ignoring unsupported properties or values, but
dbaron@2974 341 these are not always sufficient when large groups of styles need to be
dbaron@2974 342 tied to the support for certain features, as is the case for use of new
dbaron@2974 343 layout system features.</p>
dbaron@2974 344
dbaron@2983 345 <p>The syntax of the condition in the '@supports' rule is
dbaron@2974 346 slightly more complicated than for the other conditional group rules
dbaron@2974 347 (though has some similarities to media queries) since:</p>
dbaron@2974 348 <ul>
dbaron@2974 349 <li>negation is needed so that the new-feature styles and the fallback
dbaron@2974 350 styles can be separated (within the forward-compatible grammar's rules
dbaron@2974 351 for the syntax of @-rules), and not required to override each other</li>
dbaron@2974 352 <li>conjunction (and) is needed so that multiple required features can
dbaron@2974 353 be tested</li>
dbaron@2974 354 <li>disjunction (or) is needed when there are multiple alternative
dbaron@2974 355 features for a set of styles, particularly when some of those
dbaron@2974 356 alternatives are vendor-prefixed properties or values</li>
dbaron@2974 357 </ul>
dbaron@2974 358
dbaron@2983 359 <p>Therefore, the syntax of the '@supports' rule allows
dbaron@2974 360 testing for property:value pairs, and arbitrary conjunctions (and),
dbaron@2974 361 disjunctions (or), and negations (not) of them.</p>
dbaron@2974 362
dbaron@2974 363 <p>This extends the lexical scanner in the
dbaron@2974 364 <a href="http://www.w3.org/TR/CSS21/grammar.html">Grammar of CSS 2.1</a>
dbaron@2974 365 ([[!CSS21]], Appendix G) by adding:
jackalmage@6832 366 <pre>
jackalmage@6832 367 @{S}{U}{P}{P}{O}{R}{T}{S} {return SUPPORTS_SYM;}
jackalmage@6832 368 {O}{R} {return OR;}
jackalmage@6832 369 </pre>
jackalmage@6943 370
dbaron@2974 371 <p>and the grammar by adding</p>
jackalmage@6943 372
jackalmage@6315 373 <pre><dfn>supports_rule</dfn>
dbaron@7032 374 : SUPPORTS_SYM S* <i>supports_condition</i> <i>group_rule_body</i>
dbaron@2974 375 ;
dbaron@2974 376
jackalmage@6315 377 <dfn>supports_condition</dfn>
dbaron@7032 378 : <i>supports_negation</i> | <i>supports_conjunction</i> | <i>supports_disjunction</i> |
dbaron@7032 379 <i>supports_condition_in_parens</i>
dbaron@3957 380 ;
dbaron@3957 381
jackalmage@6315 382 <dfn>supports_condition_in_parens</dfn>
dbaron@7032 383 : ( '(' S* <i>supports_condition</i> ')' S* ) | <i>supports_declaration_condition</i> |
dbaron@7032 384 <i>general_enclosed</i>
dbaron@2974 385 ;
dbaron@2974 386
jackalmage@6315 387 <dfn>supports_negation</dfn>
dbaron@7032 388 : NOT S* <i>supports_condition_in_parens</i>
dbaron@2974 389 ;
dbaron@2974 390
jackalmage@6315 391 <dfn>supports_conjunction</dfn>
dbaron@7032 392 : <i>supports_condition_in_parens</i> ( AND S* <i>supports_condition_in_parens</i> )+
dbaron@2974 393 ;
dbaron@2974 394
jackalmage@6315 395 <dfn>supports_disjunction</dfn>
dbaron@7032 396 : <i>supports_condition_in_parens</i> ( OR S* <i>supports_condition_in_parens</i> )+
dbaron@2974 397 ;
dbaron@2974 398
jackalmage@6315 399 <dfn>supports_declaration_condition</dfn>
dbaron@7031 400 : '(' S* declaration ')' S*
jackalmage@6943 401 ;
jackalmage@6943 402
dbaron@7031 403 <dfn>general_enclosed</dfn>
dbaron@7031 404 : ( FUNCTION | '(' ) (any|unused)* ')' S*
dbaron@7031 405 </pre>
jackalmage@6943 406
dbaron@7031 407 <p>in which <code>declaration</code>, <code>any</code>, and
dbaron@7031 408 <code>unused</code> are the productions in the core syntax of CSS
dbaron@7031 409 defined in <a
dbaron@3024 410 href="http://www.w3.org/TR/CSS21/syndata.html#tokenization">section
jackalmage@6832 411 4.1.1 (Tokenization)</a> of [[!CSS21]],
jackalmage@6832 412 and the <code>AND</code> and <code>NOT</code> tokens are defined in
jackalmage@6832 413 the Media Queries specification [[!MEDIAQ]].</p>
dbaron@3024 414
dbaron@7031 415 <p>
dbaron@7038 416 Implementations <strong>must</strong> parse ''@supports'' rules
dbaron@7038 417 based on the above grammar,
dbaron@7038 418 and when interpreting the above grammar,
dbaron@7038 419 <strong>must</strong> match the production before an <code>|</code> operator
dbaron@7038 420 in preference to the one after it.
dbaron@7038 421 </p>
dbaron@7038 422
dbaron@7038 423 <p>
dbaron@7031 424 The above grammar is purposely very loose for forwards-compatibility reasons,
dbaron@7031 425 since the <code>general_enclosed</code> production
dbaron@7031 426 allows for substantial future extensibility.
dbaron@7033 427 Any ''@supports'' rule that does not parse according to the grammar above
dbaron@7033 428 (that is, a rule that does not match this loose grammar
dbaron@7033 429 which includes the general_enclosed production)
dbaron@7033 430 is invalid.
dbaron@7031 431 Style sheets <strong>must not</strong> use such a rule and
dbaron@7031 432 processors <strong>must</strong> ignore such a rule (including all of its contents).
dbaron@7031 433
dbaron@3021 434 <p>Each of these grammar terms is associated with a boolean result, as
dbaron@3021 435 follows:</p>
dbaron@2974 436 <dl>
dbaron@2974 437 <dt>supports_condition</dt>
dbaron@2974 438 <dd>
dbaron@3021 439 The result is the result of the single child term.
dbaron@2974 440 </dd>
dbaron@2974 441
dbaron@3957 442 <dt>supports_condition_in_parens</dt>
dbaron@3957 443 <dd>
dbaron@3957 444 The result is the result of the single <code>supports_condition</code>
dbaron@3957 445 or <code>supports_declaration_condition</code> child term.
dbaron@3957 446 </dd>
dbaron@3957 447
dbaron@2974 448 <dt>supports_negation</dt>
dbaron@2974 449 <dd>
dbaron@3021 450 The result is the <em>negation</em> of the result of the
dbaron@3021 451 <code>supports_condition_in_parens</code> child term.
dbaron@2974 452 </dd>
dbaron@2974 453
dbaron@2974 454 <dt>supports_conjunction</dt>
dbaron@2974 455 <dd>
dbaron@3021 456 The result is true if the result of <em>all</em> of the
dbaron@3021 457 <code>supports_condition_in_parens</code> child terms is true;
dbaron@3021 458 otherwise it is false.
dbaron@2974 459 </dd>
dbaron@2974 460
dbaron@2974 461 <dt>supports_disjunction</dt>
dbaron@2974 462 <dd>
dbaron@3021 463 The result is true if the result of <em>any</em> of the
dbaron@3021 464 <code>supports_condition_in_parens</code> child terms is true;
dbaron@3021 465 otherwise it is false.
dbaron@2974 466 </dd>
dbaron@2974 467
dbaron@2974 468 <dt>supports_declaration_condition</dt>
dbaron@2974 469 <dd>
jackalmage@6943 470 The result is whether the CSS processor <a href="#support-definition">supports</a> the declaration
fantasai@6845 471 within the parentheses.
jackalmage@6943 472 </dd>
jackalmage@6943 473
dbaron@7031 474 <dt>general_enclosed</dt>
jackalmage@6943 475 <dd>
jackalmage@6943 476 The result is always false.
dbaron@7031 477 Additionally, style sheets <strong>must not</strong>
dbaron@7031 478 write ''@supports'' rules
dbaron@7031 479 that match this grammar production.
dbaron@7031 480 (In other words, this production exists only for future extensibility,
dbaron@7031 481 and is not part of the description of a valid style sheet
dbaron@7031 482 in this level of the specification.)
dbaron@7031 483 <span class="note">Note that future levels may define functions
dbaron@7031 484 or other parenthesized expressions that can evaluate to true.</span>
dbaron@2974 485 </dd>
fantasai@7034 486 </dl>
jackalmage@6943 487
dbaron@3021 488 <p>The condition of the '@supports' rule is the result of the
dbaron@3021 489 <code>supports_condition</code> term that is a child of the
dbaron@3021 490 <code>supports_rule</code> term.</p>
dbaron@2974 491
dbaron@2982 492 <div class="example">
dbaron@2982 493 <p>For example, the following rule</p>
dbaron@2982 494 <pre>@supports ( display: flexbox ) {
dbaron@2982 495 body, #navigation, #content { display: flexbox; }
dbaron@2982 496 #navigation { background: blue; color: white; }
dbaron@2982 497 #article { background: white; color: black; }
dbaron@2982 498 }</pre>
dbaron@2983 499 <p>applies the rules inside the '@supports' rule only when
dbaron@2983 500 ''display: flexbox'' is supported.</p>
dbaron@2982 501 </div>
dbaron@2974 502
dbaron@2982 503 <div class="example">
dbaron@2982 504 <p>The following example shows an additional '@supports' rule that can
dbaron@2982 505 be used to provide an alternative for when ''display: flexbox'' is not
dbaron@2982 506 supported:</p>
dbaron@2982 507 <pre>@supports not ( display: flexbox ) {
dbaron@2982 508 body { width: 100%; height: 100%; background: white; color: black; }
dbaron@2982 509 #navigation { width: 25%; }
dbaron@2982 510 #article { width: 75%; }
dbaron@2974 511 }</pre>
dbaron@2982 512 <p>Note that the 'width' declarations may be harmful to the
dbaron@2982 513 flexbox-based layout, so it is important that they be present only in
dbaron@2982 514 the non-flexbox styles.</p>
dbaron@2982 515 </div>
dbaron@2974 516
dbaron@2982 517 <div class="example">
dbaron@2982 518 <p>The following example checks for support for the 'box-shadow'
dbaron@2982 519 property, including checking for support for vendor-prefixed versions of
dbaron@2982 520 it. When the support is present, it specifies both 'box-shadow' (with
dbaron@2982 521 the prefixed versions) and 'color' in a way what would cause the text to
dbaron@2982 522 become invisible were 'box-shadow' not supported.</p>
dbaron@2982 523 <pre>@supports ( box-shadow: 2px 2px 2px black ) or
dbaron@2982 524 ( -moz-box-shadow: 2px 2px 2px black ) or
dbaron@2974 525 ( -webkit-box-shadow: 2px 2px 2px black ) or
dbaron@2974 526 ( -o-box-shadow: 2px 2px 2px black ) {
dbaron@2982 527 .outline {
dbaron@2982 528 color: white;
dbaron@2982 529 -moz-box-shadow: 2px 2px 2px black;
dbaron@2982 530 -webkit-box-shadow: 2px 2px 2px black;
dbaron@2982 531 -o-box-shadow: 2px 2px 2px black;
dbaron@3960 532 box-shadow: 2px 2px 2px black; /* unprefixed last */
dbaron@2982 533 }
dbaron@2982 534 }</pre></div>
dbaron@2974 535
dbaron@2984 536 <p>To avoid confusion between ''and'' and ''or'', the syntax requires
dbaron@2984 537 that both ''and'' and ''or'' be specified explicitly (rather than, say,
dbaron@2984 538 using commas or spaces for one of them). Likewise, to avoid confusion
dbaron@2984 539 caused by precedence rules, the syntax does not allow ''and'', ''or'',
dbaron@2984 540 and ''not'' operators to be mixed without a layer of parentheses.</p>
dbaron@2974 541
dbaron@2984 542 <div class="example">
dbaron@2984 543 <p>For example, the following rule is not valid:
dbaron@3959 544 <pre class="illegal">@supports (transition-property: color) or
dbaron@2984 545 (animation-name: foo) and
dbaron@2984 546 (transform: rotate(10deg)) {
dbaron@2984 547 // ...
dbaron@2984 548 }</pre>
dbaron@2984 549 <p>Instead, authors must write one of the following:</p>
dbaron@2984 550 <pre>@supports ((transition-property: color) or
dbaron@2984 551 (animation-name: foo)) and
dbaron@2984 552 (transform: rotate(10deg)) {
dbaron@2984 553 // ...
dbaron@2984 554 }</pre>
dbaron@2984 555 <pre>@supports (transition-property: color) or
dbaron@3430 556 ((animation-name: foo) and
dbaron@2984 557 (transform: rotate(10deg))) {
dbaron@2984 558 // ...
dbaron@2984 559 }</pre>
dbaron@2984 560 </div>
dbaron@2974 561
dbaron@3957 562 <p>The declaration being tested must always occur within parentheses,
dbaron@3957 563 when it is the only thing in the expression.<p>
dbaron@3957 564
dbaron@3957 565 <div class="example">
dbaron@3957 566 <p>For example, the following rule is not valid:
dbaron@3959 567 <pre class="illegal">@supports display: flexbox {
dbaron@3957 568 // ...
dbaron@3957 569 }</pre>
dbaron@3957 570 <p>Instead, authors must write:</p>
dbaron@3957 571 <pre>@supports (display: flexbox) {
dbaron@3957 572 // ...
dbaron@3957 573 }</pre>
dbaron@3957 574 </div>
dbaron@3957 575
dbaron@3957 576 <p>The syntax allows extra parentheses when they are not needed. This
dbaron@3957 577 flexibility is sometimes useful for authors (for example, when
dbaron@3957 578 commenting out parts of an expression) and may also be useful for
dbaron@3957 579 authoring tools.</p>
dbaron@3957 580
dbaron@3957 581 <div class="example">
dbaron@3957 582 <p>For example, authors may write:</p>
dbaron@3957 583 <pre>@supports ((display: flexbox)) {
dbaron@3957 584 // ...
dbaron@3957 585 }</pre>
dbaron@3957 586 </div>
dbaron@3957 587
jackalmage@6793 588 <p>A trailing ''!important'' on a declaration being tested is allowed,
jackalmage@6793 589 though it won't change the validity of the declaration.
jackalmage@6793 590
jackalmage@6793 591 <div class="example">
jackalmage@6793 592 <p>For example, the following rule is valid:
jackalmage@6793 593 <pre>@supports (display: flexbox !important) {
jackalmage@6793 594 // ...
jackalmage@6793 595 }</pre>
jackalmage@6793 596 </div>
dbaron@6306 597
jackalmage@6617 598 <h3 id="support-definition">Definition of support</h3>
dbaron@3021 599
dbaron@6741 600 <p>For forward-compatibility,
dbaron@6741 601 <a href="http://www.w3.org/TR/CSS21/syndata.html#declaration">section 4.1.8
dbaron@6741 602 (Declarations and properties)</a> of [[!CSS21]]
dbaron@6741 603 defines rules for handling invalid properties and values.
dbaron@6741 604 CSS processors that
dbaron@6741 605 do not implement or partially implement a specification
dbaron@6741 606 <strong>must</strong> treat any part of a value that they
dbaron@6741 607 do not implement, or
dbaron@6741 608 do not have a usable level of support for,
dbaron@6741 609 as invalid according to this rule
dbaron@6741 610 for handling invalid properties and values,
dbaron@6741 611 and therefore <strong>must</strong> discard the declaration as a parse error.</p>
dbaron@6741 612
jackalmage@6617 613 <p>A CSS processor is considered to <dfn id="dfn-support">support</dfn>
dbaron@6741 614 a declaration (consisting of a property and value) if it accepts that
dbaron@6741 615 declaration (rather than discarding it as a parse error).
dbaron@6741 616 If a processor does not implement, with a usable level of support,
dbaron@6741 617 the value given,
dbaron@6741 618 then it <strong>must not</strong>
dbaron@6741 619 accept the declaration or claim support for it.</p>
dbaron@3021 620
dbaron@6742 621 <p>These rules (and the equivalence between them) allow
dbaron@3021 622 authors to use fallback (either in the [[CSS1]] sense of declarations
dbaron@3021 623 that are overridden by later declarations or with the new capabilities
dbaron@3021 624 provided by the ''@supports'' rule in this specification) that works
dbaron@3021 625 correctly for the features implemented. This applies especially to
dbaron@3021 626 compound values; implementations must implement all parts of the value
dbaron@3021 627 in order to consider the declaration supported, either inside a ruleset
dbaron@3021 628 or in the declaration condition of an ''@supports'' rule.</p>
dbaron@3021 629
jackalmage@6838 630 <!--
jackalmage@6617 631 <h2 id="at-document">Document queries: the '@document' rule</h2>
dbaron@2974 632
dbaron@2983 633 <p>The <dfn>'@document' rule</dfn> is a conditional group
dbaron@3027 634 rule whose condition depends on the
dbaron@3027 635 <a href="#url-of-doc">URL of the document being styled</a>.
dbaron@2974 636 This allows style sheets, particularly user style sheets, to have styles
dbaron@2974 637 that only apply to a set of pages rather than to all pages using the
dbaron@2974 638 style sheet.</p>
dbaron@2974 639
dbaron@2974 640 <p class="issue">Given that this @-rule is intended primarily for user
dbaron@2974 641 style sheets, what should this specification say about its use in author
dbaron@2974 642 style sheets? Should it be forbidden? Should use instead be
dbaron@2974 643 discouraged? Or should this specification remain neutral on the
dbaron@2986 644 topic, since there are valid uses in author style sheets?</p>
dbaron@2974 645
jackalmage@6617 646 <p id="url-of-doc">The <dfn>URL of the document being styled</dfn> is
dbaron@3027 647 the URI at which the document is located, excluding any fragment
dbaron@3027 648 identifiers. (This means, for example, that HTTP redirects have been
dbaron@3027 649 followed.) If the styles are being applied inside a complete document
dbaron@3246 650 embedded into the presentation of another (e.g., [[HTML5]]&#39;s <code
dbaron@3027 651 class="html">iframe</code>, <code class="html">object</code>, or <code
dbaron@3027 652 class="html">img</code> elements), the relevant URI is that of the
dbaron@3027 653 frame, not of its container. However, if content from other documents
dbaron@3027 654 is mixed in via mechanisms that mix content from one document into
dbaron@3246 655 another (e.g., [[SVG11]]&#39;s <code>use</code> element), then the
dbaron@3027 656 address of the container document is used.</p>
dbaron@3027 657
dbaron@3027 658 <p class="note">Note: In [[HTML5]], this is the
fantasai@6697 659 <a href="http://dev.w3.org/html5/spec/dom.html#documents">document's address</a>
dbaron@3027 660 of a document in a
dbaron@3027 661 <a href="http://dev.w3.org/html5/spec/browsers.html#browsing-context">browsing context</a>.</p>
dbaron@3027 662
dbaron@3240 663 <div class="issue">What form of normalization is done on URLs and domains
dbaron@3240 664 before matching? In particular, this specification needs to describe:
dbaron@3240 665 <ul>
dbaron@3240 666 <li>what form is used for the <a href="#url-of-doc">URL of the document
dbaron@3240 667 being styled</a> (and what has been normalized in that form)</li>
dbaron@3240 668 <li>what normalization (if any) happens to the argument of each of the match
dbaron@3240 669 functions before the comparison that they describe and</li>
dbaron@3240 670 <li>whether the
dbaron@3240 671 comparison algorithm used is string comparison or some other URL
dbaron@3240 672 comparison algorithm.</li></ul></div>
dbaron@3027 673
dbaron@2983 674 <p>The '@document' rule's condition is written as a
dbaron@2974 675 comma-separated list of <dfn>URL matching functions</dfn>, and the
dbaron@2974 676 condition evaluates to true whenever any one of those functions
dbaron@2974 677 evaluates to true. The following URL matching functions are
dbaron@2974 678 permitted:</p>
dbaron@2974 679
dbaron@2974 680 <dl>
jackalmage@6617 681 <dt><dfn id="url-exact" title="url()|URL matching functions::exact">&lt;url&gt;</dfn></dt>
dbaron@2974 682
dbaron@2974 683 <dd>
dbaron@2983 684 <p>The 'url()' function is the <dfn>exact url matching
dbaron@3027 685 function</dfn>. It evaluates to true whenever the <a
dbaron@3027 686 href="#url-of-doc">URL of the document being styled</a> is exactly
dbaron@3027 687 the URL given.</p>
dbaron@2974 688
dbaron@2983 689 <p class="Note">The 'url()' function, since it is a core syntax
dbaron@2974 690 element in CSS, is allowed (subject to different character
dbaron@2974 691 limitations and thus escaping requirements) to contain an unquoted
dbaron@2974 692 value (in addition to the string values that are allowed as
dbaron@2974 693 arguments for all four functions).</p>
dbaron@2974 694
dbaron@2974 695 <div class="example">
dbaron@2974 696 <p>For example, this rule:</p>
dbaron@2974 697 <pre>@document url("http://www.w3.org/Style/CSS/") {
dbaron@2974 698 #summary { background: yellow; color: black}
dbaron@2974 699 }</pre>
dbaron@2983 700 <p>styles the <code class="html">summary</code> element on the page
dbaron@2974 701 <code>http://www.w3.org/Style/CSS/</code>, but not on any other
dbaron@2974 702 pages.</p>
dbaron@2974 703 </div>
dbaron@2974 704 </dd>
dbaron@2974 705
jackalmage@6617 706 <dt><dfn id="url-prefix" title="url-prefix()|URL matching functions::prefix">url-prefix(&lt;string&gt;)</dfn></dt>
dbaron@2974 707
dbaron@2974 708 <dd>
dbaron@2983 709 <p>The 'url-prefix()' function is the <dfn>url prefix
dbaron@3027 710 matching function</dfn>. It evaluates to true whenever the
dbaron@3027 711 <a href="#url-of-doc">URL of the document being styled</a>
dbaron@3027 712 has the argument to the function as an
dbaron@2974 713 initial substring (which is true when the two strings are equal).
dbaron@2974 714 When the argument is the empty string, it evaluates to true for all
dbaron@2974 715 documents.</p>
dbaron@2974 716 <div class="example">
dbaron@2974 717 <p>For example, this rule:</p>
dbaron@2974 718 <pre>@document url-prefix("http://www.w3.org/Style/CSS/") {
dbaron@2974 719 #summary { background: yellow; color: black}
dbaron@2974 720 }</pre>
dbaron@2983 721 <p>styles the <code class="html">summary</code> element on the page
dbaron@2974 722 <code>http://www.w3.org/Style/CSS/</code> and on the page
dbaron@2974 723 <code>http://www.w3.org/Style/CSS/Test</code>, but it does not
dbaron@2974 724 affect the page <code>http://www.w3.org/</code> or the page
dbaron@2974 725 <code>http://www.example.com/Style/CSS/</code>.</p>
dbaron@2974 726 </div>
dbaron@2974 727 </dd>
dbaron@2974 728
jackalmage@6617 729 <dt><dfn id="url-domain" title="domain()|URL matching functions::domain">domain(&lt;string&gt;)</dfn></dt>
dbaron@2974 730
dbaron@2974 731 <dd>
dbaron@2983 732 <p>The 'domain()' function is the <dfn>domain
dbaron@2974 733 matching function</dfn>. It evaluates to true whenever
dbaron@3027 734 the <a href="#url-of-doc">URL of the document being styled</a>
dbaron@3027 735 has a host subcomponent (as defined in [[!URI]])
dbaron@2974 736 and that host subcomponent is exactly the argument to the
dbaron@2983 737 'domain()' function or a final substring of the host
dbaron@2974 738 component is a period (U+002E) immediately followed by the argument
dbaron@2983 739 to the 'domain()' function.</p>
dbaron@2974 740 <div class="example">
dbaron@2974 741 <p>For example, this rule:</p>
dbaron@2974 742 <pre>@document domain("w3.org") {
dbaron@2974 743 body { font-size: 16px ! important }
dbaron@2974 744 }</pre>
dbaron@2974 745 <p>changes the font size of the body element for pages such as
dbaron@2974 746 <code>http://www.w3.org/Style/CSS/</code> and
dbaron@2974 747 <code>http://w3.org/Style/CSS/</code> and
dbaron@2974 748 <code>http://lists.w3.org/Archives/Public/www-style/</code>
dbaron@2974 749 but it does not affect the page
dbaron@2974 750 <code>http://www.example.com/Style/CSS/</code>.</p>
dbaron@2974 751 </div>
dbaron@2974 752 </dd>
dbaron@2974 753
jackalmage@6617 754 <dt><dfn id="url-regexp" title="regexp()|URL matching functions::regular expression">regexp(&lt;string&gt;)</dfn></dt>
dbaron@2974 755
dbaron@2974 756 <dd>
dbaron@2986 757 <p>The contents of the &lt;string&gt; argument <strong>must</strong>
dbaron@3068 758 match the JavaScript <code>Pattern</code> production
dbaron@3068 759 ([[!ECMA-262-5.1]], section 15.10.1). However,
dbaron@2986 760 failing to do so is not a CSS syntax error and does not trigger any
dbaron@2986 761 error handling for CSS syntax errors.</p>
dbaron@2986 762
dbaron@2986 763 <p>The ''regexp()'' function evaluates to true whenever the string
dbaron@2986 764 argument compiled as a JavaScript regular expression with the
dbaron@2986 765 <code>global</code>, <code>ignoreCase</code> and
dbaron@2986 766 <code>multiline</code> flags <em>disabled</em>
dbaron@3068 767 (see [[!ECMA-262-5.1]], sections 15.10.7.2 through 15.10.7.4)
dbaron@2986 768 compiles successfully and the resulting regular expression matches
dbaron@3027 769 the entirety of the
dbaron@3027 770 <a href="#url-of-doc">URL of the document being styled</a>.</p>
dbaron@2986 771
dbaron@2986 772 <p class="note">Note that regular expression must match the entire
dbaron@2986 773 URL, not just a part of it.</p>
dbaron@2974 774
dbaron@3018 775 <p class="note">Note that this definition intentionally matches the
dbaron@3018 776 behavior of the <a
dbaron@2983 777 href="http://dev.w3.org/html5/spec/common-input-element-attributes.html#attr-input-pattern"><code class="html">pattern</code>
dbaron@2983 778 attribute</a> on the <code class="html">input</code> element
dbaron@2983 779 in [[HTML5]].</p>
dbaron@2986 780
dbaron@2986 781 <div class="example">
dbaron@2986 782 <p>For example, this rule:</p>
dbaron@2986 783 <pre>@document regexp("http://www.w3.org/TR/\\d{4}/[^/]*-CSS2-\\d{8}/") {
dbaron@2986 784 body { font-size: 20px ! important }
dbaron@2986 785 }</pre>
dbaron@2986 786 <p>changes the font size of the body element for pages such as
dbaron@2986 787 <code>http://www.w3.org/TR/2011/PR-CSS2-20110412/</code>.</p>
dbaron@2986 788 <p class="note">Note that the backslashes in the regular
dbaron@2986 789 expression require CSS escaping as ''\\''.</p>
dbaron@2986 790 </div>
dbaron@2974 791 </dd>
dbaron@2974 792
dbaron@2974 793 </dl>
dbaron@2974 794
dbaron@2979 795 <p>Implementations <strong>must</strong> treat any unknown URL matching
dbaron@3045 796 functions as a syntax error, and thus ignore the '@document' rule.
dbaron@3045 797 <span class="issue">Should we instead have more complicated error
dbaron@3045 798 handling rules to make forward-compatibility work differently, or is
dbaron@3045 799 this rule the best solution for such future expansion anyway?</span></p>
dbaron@2974 800
dbaron@5293 801 <div class="issue">This syntax doesn't offer any ability to do negations,
dbaron@5293 802 which has been requested in <a
jackalmage@6617 803 href="https://bugzilla.mozilla.org/show_bug.cgi?id=349813">Mozilla bug
dbaron@5293 804 349813</a>. Use cases that people have wanted negations for
dbaron@5293 805 include:
dbaron@5293 806 <ul>
dbaron@5293 807 <li>User style sheets that want a particular rule in general, but know
dbaron@5293 808 that that rule does more harm than good on specific sites.</li>
dbaron@5293 809 <li>Authors who have a rule that they want to apply to most of their
dbaron@5293 810 pages, but wish to make a few exceptions for.</li>
dbaron@5293 811 </ul>
dbaron@5293 812 </div>
dbaron@5293 813
dbaron@2974 814 <p>This extends the lexical scanner in the
dbaron@2974 815 <a href="http://www.w3.org/TR/CSS21/grammar.html">Grammar of CSS 2.1</a>
dbaron@2974 816 ([[!CSS21]], Appendix G) by adding:
dbaron@2974 817 <pre>@{D}{O}{C}{U}{M}{E}{N}{T} {return DOCUMENT_SYM;}</pre>
dbaron@2974 818 <p>and the grammar by adding</p>
dbaron@7032 819 <pre><dfn>document_rule</dfn>
dbaron@7032 820 : DOCUMENT_SYM S+ <i>url_match_fn</i> ( "," S* <i>url_match_fn</i> )* <i>group_rule_body</i>
dbaron@2974 821 ;
dbaron@2974 822
dbaron@7032 823 <dfn>url_match_fn</dfn>
dbaron@6740 824 : (URI | FUNCTION S* STRING S* ')' ) S*
dbaron@2974 825 ;</pre>
jackalmage@6838 826 -->
jackalmage@6838 827
dbaron@2974 828
jackalmage@6617 829 <h2 id="apis">APIs</h2>
dbaron@3416 830
jackalmage@6617 831 <h3 id='extentions-to-cssrule-interface'>
jackalmage@6315 832 Extensions to the <code>CSSRule</code> interface</h3>
dbaron@3416 833
jackalmage@6315 834 <p>The <code>CSSRule</code> interface is extended as follows:
jackalmage@6315 835
jackalmage@6315 836 <pre class='idl'>partial interface CSSRule {
jackalmage@6315 837 const unsigned short SUPPORTS_RULE = 12;
jackalmage@6838 838 <!--
jackalmage@6315 839 const unsigned short DOCUMENT_RULE = 13;
jackalmage@6838 840 -->
jackalmage@6315 841 }</pre>
jackalmage@6315 842
jackalmage@6315 843
jackalmage@6655 844 <h3 id='the-cssgroupingrule-interface'>
jackalmage@6655 845 The <code>CSSGroupingRule</code> interface</h3>
jackalmage@6655 846
jackalmage@6655 847 <p>The <dfn><code>CSSGroupingRule</code></dfn> interface represents an at-rule that contains other rules nested inside itself.
jackalmage@6655 848
jackalmage@6655 849 <pre class='idl'>interface CSSGroupingRule : CSSRule {
dbaron@7102 850 readonly attribute <a href="http://www.w3.org/TR/DOM-Level-2-Style/css.html#CSS-CSSRuleList">CSSRuleList</a> cssRules;
jackalmage@6655 851 unsigned long insertRule (DOMString rule, unsigned long index);
jackalmage@6655 852 void deleteRule (unsigned long index);
jackalmage@6655 853 }</pre>
jackalmage@6655 854
jackalmage@6655 855 <dl class='idl-attributes'>
dbaron@7102 856 <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 857 <dd>The <code>cssRules</code> attribute must return a <code>CSSRuleList</code>
jackalmage@6655 858 object for the list of CSS rules nested inside the grouping rule.
jackalmage@6655 859 </dl>
jackalmage@6655 860
jackalmage@6655 861 <dl class='idl-methods'>
jackalmage@6655 862 <dt><code>insertRule(DOMString rule, unsigned long index)</code>, returns
jackalmage@6655 863 <code>unsigned long</code>
dbaron@7104 864 <dd>
dbaron@7104 865 The <code>insertRule</code> operation must
dbaron@7104 866 insert a CSS rule <var>rule</var>
dbaron@7104 867 into the CSS rule list returned by <code>cssRules</code>,
dbaron@7104 868 such that the inserted rule will be at position <var>index</var>,
dbaron@7104 869 and any rules previously at <var>index</var> or higher
dbaron@7104 870 will increase their index by one.
dbaron@7104 871 It must throw INDEX_SIZE_ERR
dbaron@7104 872 if index is greater than <code>cssRules.length</code>.
dbaron@7104 873 It must throw SYNTAX_ERR
dbaron@7104 874 if the rule has a syntax error and is unparseable;
dbaron@7104 875 this does not include syntax errors handled by error handling rules
dbaron@7104 876 for constructs inside of the rule.
dbaron@7104 877 It must throw HIERARCHY_REQUEST_ERR
dbaron@7104 878 if the rule cannot be inserted at the location specified,
dbaron@7104 879 for example, if an ''@import'' rule is inserted inside a group rule.
dbaron@7104 880
dbaron@7104 881 <span class="issue">This needs to specify what to do
dbaron@7104 882 if <code>rule</code> is the empty string,
dbaron@7104 883 if it contains more than one CSS rule,
dbaron@7104 884 or if it contains garbage after a valid rule.</span>
jackalmage@6655 885
jackalmage@6655 886 <dt><code>deleteRule (unsigned long index)</code>, return <code>void</code>
dbaron@7104 887 <dd>
dbaron@7104 888 The <code>deleteRule</code> operation must
dbaron@7104 889 remove a CSS rule from
dbaron@7104 890 the CSS rule list returned by <code>cssRules</code> at <var>index</var>.
dbaron@7104 891 It must throw INDEX_SIZE_ERR
dbaron@7104 892 if index is greater than or equal to <code>cssRules.length</code>.
jackalmage@6655 893 </dl>
jackalmage@6655 894
jackalmage@6655 895
jackalmage@6618 896 <h3 id="the-cssconditionrule-interface">
jackalmage@6618 897 The <code>CSSConditionRule</code> interface</h3>
jackalmage@6315 898
jackalmage@6620 899 <p>The <dfn><code>CSSConditionRule</code></dfn> interface represents all the "conditional" at-rules,
jackalmage@6620 900 which consist of a condition and a statement block.
dbaron@6323 901
jackalmage@6655 902 <pre class='idl'>interface CSSConditionRule : CSSGroupingRule {
dbaron@6324 903 attribute DOMString conditionText;
jackalmage@6315 904 }</pre>
jackalmage@6315 905
jackalmage@6315 906 <dl class='idl-attributes'>
dbaron@6732 907
jackalmage@6619 908 <dt><code>conditionText</code> of type <code>DOMString</code>
dbaron@6732 909 <dd>
dbaron@6732 910 <p>The <code>conditionText</code> attribute represents
dbaron@6732 911 the condition of the rule.
dbaron@6732 912 Since what this condition does
dbaron@6732 913 varies between the derived interfaces of <code>CSSConditionRule</code>,
dbaron@6732 914 those derived interfaces
dbaron@6732 915 may specify different behavior for this attribute
dbaron@6732 916 (see, for example, <code>CSSMediaRule</code> below).
dbaron@6732 917 In the absence of such rule-specific behavior,
dbaron@6732 918 the following rules apply:</p>
dbaron@6732 919
dbaron@6732 920 <p>The <code>conditionText</code> attribute, on getting, must return
jackalmage@6618 921 the result of serializing the associated condition.
jackalmage@6315 922
dbaron@6324 923 <p>On setting the <code>conditionText</code> attribute these steps
jackalmage@6315 924 must be run:
jackalmage@6315 925
jackalmage@6315 926 <ol>
jackalmage@6315 927 <li>Trim the given value of white space.
jackalmage@6315 928 <li>If the given value matches the grammar of the
jackalmage@6618 929 appropriate condition production for the given rule,
jackalmage@6618 930 replace the associated CSS condition with the given value.
jackalmage@6315 931 <li>Otherwise, do nothing.
jackalmage@6315 932 </ol>
jackalmage@6315 933 </dl>
jackalmage@6315 934
jackalmage@6618 935
jackalmage@6618 936 <h3 id="the-cssmediarule-interface">
jackalmage@6618 937 The <code>CSSMediaRule</code> interface</h3>
jackalmage@6618 938
jackalmage@6618 939 <p>The <dfn><code>CSSMediaRule</code></dfn> interface represents a ''@media'' rule:
jackalmage@6618 940
jackalmage@6618 941 <pre class='idl'>interface CSSMediaRule : CSSConditionRule {
dbaron@7102 942 readonly attribute <a href="http://www.w3.org/TR/DOM-Level-2-Style/stylesheets.html#StyleSheets-MediaList">MediaList</a> media;
jackalmage@6618 943 }</pre>
jackalmage@6618 944
jackalmage@6618 945 <dl class='idl-attributes'>
dbaron@7102 946 <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 947 <dd>The <code>media</code> attribute must return a <code>MediaList</code> object
jackalmage@6618 948 for the list of media queries specified with the ''@media'' rule.
jackalmage@6618 949
jackalmage@6619 950 <dt><code>conditionText</code> of type <code>DOMString</code>
jackalmage@6618 951 <dd>The <code>conditionText</code> attribute (defined on the <code>CSSConditionRule</code> parent rule),
jackalmage@6618 952 on getting, must return the value of <code>media.mediaText</code> on the rule.
jackalmage@6618 953
jackalmage@6621 954 <p>Setting the <code>conditionText</code> attribute
jackalmage@6621 955 must set the <code>media.mediaText</code> attribute on the rule.
jackalmage@6621 956 </dl>
jackalmage@6618 957
jackalmage@6618 958
jackalmage@6618 959 <h3 id="the-csssupportsrule-interface">
jackalmage@6618 960 The <code>CSSSupportsRule</code> interface</h3>
jackalmage@6618 961
jackalmage@6618 962 <p>The <dfn><code>CSSSupportsRule</code></dfn> interface represents a ''@supports'' rule.</p>
jackalmage@6618 963
jackalmage@6621 964 <pre class='idl'>interface CSSSupportsRule : CSSConditionRule {
jackalmage@6618 965 }</pre>
jackalmage@6618 966
jackalmage@6838 967 <!--
jackalmage@6618 968 <h3 id="the-cssdocumentrule-interface">
jackalmage@6618 969 The <code>CSSDocumentRule</code> interface</h3>
jackalmage@6618 970
jackalmage@6618 971 <p>The <dfn><code>CSSDocumentRule</code></dfn> interface represents a ''@document'' rule.</p>
jackalmage@6618 972
jackalmage@6621 973 <pre class='idl'>interface CSSDocumentRule : CSSConditionRule {
jackalmage@6618 974 }</pre>
jackalmage@6838 975 -->
jackalmage@6315 976
jackalmage@6315 977
jackalmage@6620 978 <h3 id='the-css-interface'>
jackalmage@6620 979 The <code>CSS</code> interface, and the <code title=''>supports()</code> function</h3>
jackalmage@6315 980
jackalmage@6620 981 <p>The <dfn id='CSS-interface'><code>CSS</code></dfn> interface holds useful CSS-related functions that do not belong elsewhere.
jackalmage@6315 982
jackalmage@6620 983 <pre class='idl'>interface CSS {
dbaron@7043 984 static boolean supports(DOMString property, DOMString value);
dbaron@7043 985 static boolean supports(DOMString declaration);
jackalmage@6620 986 }</pre>
jackalmage@6620 987
jackalmage@6620 988 <dl class='idl-methods'>
jackalmage@6620 989 <dt><code>supports(DOMString property, DOMString value)</code>,
jackalmage@6620 990 returns <code>boolean</code>
jackalmage@6625 991 <dt><code>supports(DOMString conditionText)</code>,
jackalmage@6620 992 returns <code>boolean</code>
jackalmage@6620 993 <dd>
jackalmage@6620 994 When the <code title=''>supports()</code> method is invoked with two arguments <var>property</var> and <var>value</var>,
jackalmage@6620 995 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 996 and <var>value</var> would be successfully parsed as a supported value for that property.
jackalmage@6620 997 Otherwise, it must return <code>false</code>.
jackalmage@6620 998
jackalmage@6620 999 <p>
jackalmage@6625 1000 When invoked with a single <var>conditionText</var> argument,
jackalmage@6625 1001 it must return <code>true</code> if <var>conditionText</var>,
jackalmage@6625 1002 when parsed and evaluated as a <code>supports_condition</code>,
jackalmage@6625 1003 would return true.
jackalmage@6620 1004 Otherwise, it must return <code>false</code>.
jackalmage@6620 1005 </dl>
jackalmage@6620 1006
dbaron@3417 1007
fantasai@6831 1008 <h2 class=no-num id="grammar">Grammar</h2>
fantasai@6831 1009
fantasai@6831 1010 <p>In order to allow these new @-rules in CSS style sheets, this
fantasai@6831 1011 specification modifies the <code>stylesheet</code> production in the <a
fantasai@6831 1012 href="http://www.w3.org/TR/CSS21/grammar.html">Appendix G</a> grammar of
fantasai@6831 1013 [[!CSS21]] by replacing the <code>media</code> production defined in
fantasai@6831 1014 [[!CSS21]] with the <code>media</code> production defined in this one,
jackalmage@6838 1015 and additionally inserting <code>| supports_rule</code>
fantasai@6831 1016 alongside <code>ruleset | media | page</code>.</p>
fantasai@6831 1017
fantasai@6831 1018
jackalmage@6617 1019 <h2 id="conformance">Conformance</h2>
dbaron@2974 1020
jackalmage@6617 1021 <h3 id="base-modules">Base Modules</h3>
dbaron@3022 1022
dbaron@3022 1023 <p>This specification defines conformance in terms of base modules,
dbaron@3022 1024 which are modules that this specification builds on top of. The base
dbaron@3022 1025 modules of this module are:</p>
dbaron@3022 1026
dbaron@3022 1027 <ul>
dbaron@3022 1028 <li>[[!CSS21]]</li>
dbaron@3022 1029 </ul>
dbaron@3022 1030
dbaron@3022 1031 <p>All of the conformance requirements of all base modules are
dbaron@3022 1032 incorporated as conformance requirements of this module, except where
dbaron@3022 1033 overridden by this module.</p>
dbaron@3022 1034
dbaron@3022 1035 <p>Additionally, all conformance requirements related to validity of
dbaron@3022 1036 syntax in this module and all of its base modules are to be interpreted
dbaron@3022 1037 as though all syntax in all of those modules is valid.</p>
dbaron@3022 1038
dbaron@3022 1039 <div class="example"><p>For example, this means that grammar presented
dbaron@3022 1040 in modules other than [[!CSS21]] must obey the requirements that
dbaron@3022 1041 [[!CSS21]] defines for the parsing of properties, and that requirements
dbaron@3022 1042 for handling invalid syntax in [[!CSS21]] do not treat syntax added by
dbaron@3022 1043 other modules as invalid.</p></div>
dbaron@3022 1044
dbaron@3022 1045 <p>Additionally, the set of valid syntax can be increased by the
dbaron@3022 1046 conformance of a style sheet or processor to additional modules; use of
dbaron@3022 1047 such syntax does not make a style sheet nonconformant and failure to
dbaron@3022 1048 treat such syntax as invalid does not make a processor
dbaron@3022 1049 nonconformant.</p>
dbaron@3022 1050
jackalmage@6617 1051 <h3 id="conformance-classes">Conformance Classes</h3>
dbaron@2974 1052
dbaron@2974 1053 <p>Conformance to the CSS Conditional Rules Module is defined for three
dbaron@2974 1054 conformance classes:
dbaron@2974 1055 <dl>
jackalmage@6617 1056 <dt><dfn title="conformance::style sheet" id="conform-style-sheet">style sheet</dfn>
dbaron@2974 1057 <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS
dbaron@3022 1058 style sheet</a>.</dd>
jackalmage@6617 1059 <dt><dfn title="conformance::processor" id="conform-processor">processor</dfn></dt>
dbaron@3022 1060 <dd>A tool that reads CSS style sheets: it may be a renderer or
dbaron@3022 1061 <a
dbaron@3022 1062 href="http://www.w3.org/TR/CSS21/conform.html#user-agent">user-agent</a>
dbaron@2974 1063 that interprets the semantics of a style sheet and renders
dbaron@3022 1064 documents that use style sheets, or it may be a validator that
dbaron@3022 1065 checks style sheets.</dd>
jackalmage@6617 1066 <dt><dfn title="conformance::authoring tool" id="conform-authoring-tool">authoring tool</dfn></dt>
dbaron@3022 1067 <dd>A tool that writes a style sheet.</dd>
dbaron@2974 1068 </dl>
dbaron@3022 1069
dbaron@3022 1070 <p>A style sheet is conformant to the CSS Conditional Rules Module
dbaron@3022 1071 if it meets all of the conformance requirements in the module that are
dbaron@3022 1072 described as requirements of style sheets.</p>
dbaron@3022 1073
dbaron@3022 1074 <p>A processor is conformant to the CSS Conditional Rules Module if it
dbaron@3022 1075 meets all applicable conformance requirements in the module that are
dbaron@3022 1076 described as requirements of processors. In general, all requirements
dbaron@3022 1077 are applicable to renderers. Requirements concerning a part of CSS
dbaron@3022 1078 not performed by a processor are not applicable, e.g., requirements
dbaron@3022 1079 related to rendering are not applicable to a validator. The inability
dbaron@3022 1080 of a processor to correctly render a document due to limitations of
dbaron@3022 1081 the device does not make it non-conformant. (For example, a renderer
dbaron@3022 1082 is not required to render color on a monochrome monitor.)</p>
dbaron@3022 1083
dbaron@3022 1084 <p>An authoring tool is conformant to the CSS Conditional Rules Module
dbaron@3022 1085 if it writes style sheets that conform to the module and (if it reads
dbaron@3022 1086 CSS) it is a conformant processor.</p>
dbaron@2974 1087
jackalmage@6617 1088 <h3 id="partial">
dbaron@2974 1089 Partial Implementations</h3>
dbaron@2974 1090
dbaron@2974 1091 <p>So that authors can exploit the forward-compatible parsing rules to
dbaron@2974 1092 assign fallback values, CSS renderers <strong>must</strong>
dbaron@2974 1093 treat as invalid (and <a href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignore
dbaron@2974 1094 as appropriate</a>) any at-rules, properties, property values, keywords,
dbaron@2974 1095 and other syntactic constructs for which they have no usable level of
dbaron@2974 1096 support. In particular, user agents <strong>must not</strong> selectively
dbaron@2974 1097 ignore unsupported component values and honor supported values in a single
dbaron@2974 1098 multi-value property declaration: if any value is considered invalid
dbaron@2974 1099 (as unsupported values must be), CSS requires that the entire declaration
dbaron@2974 1100 be ignored.</p>
dbaron@2974 1101
jackalmage@6617 1102 <h3 id="experimental">Experimental Implementations</h3>
dbaron@2974 1103
dbaron@2974 1104 <p>To avoid clashes with future CSS features, the CSS specifications
dbaron@2974 1105 reserve a <a href="http://www.w3.org/TR/CSS21/syndata.html#vendor-keywords">prefixed
dbaron@2974 1106 syntax</a> for proprietary property and value extensions to CSS. The CSS
dbaron@2974 1107 Working Group recommends that experimental implementations of features in
dbaron@2974 1108 CSS Working Drafts also use vendor-prefixed property or value names. This
dbaron@2974 1109 avoids any incompatibilities with future changes in the draft. Once a
dbaron@2974 1110 specification reaches the Candidate Recommendation stage, implementors
dbaron@2974 1111 should implement the non-prefixed syntax for any feature they consider to
dbaron@2974 1112 be correctly implemented according to spec.</p>
dbaron@2974 1113
jackalmage@6617 1114 <h3 id="cr-exit-criteria">CR Exit Criteria</h3>
dbaron@2974 1115
dbaron@3244 1116 <p>For this specification to be advanced to Proposed Recommendation,
dbaron@2974 1117 there must be at least two independent, interoperable implementations
dbaron@2974 1118 of each feature. Each feature may be implemented by a different set of
dbaron@2974 1119 products, there is no requirement that all features be implemented by
dbaron@2974 1120 a single product. For the purposes of this criterion, we define the
dbaron@2974 1121 following terms:
dbaron@2974 1122
dbaron@2974 1123 <dl>
dbaron@2974 1124 <dt>independent <dd>each implementation must be developed by a
dbaron@2974 1125 different party and cannot share, reuse, or derive from code
dbaron@2974 1126 used by another qualifying implementation. Sections of code that
dbaron@2974 1127 have no bearing on the implementation of this specification are
dbaron@2974 1128 exempt from this requirement.
dbaron@2974 1129
dbaron@2974 1130 <dt>interoperable <dd>passing the respective test case(s) in the
dbaron@2974 1131 official CSS test suite, or, if the implementation is not a Web
dbaron@2974 1132 browser, an equivalent test. Every relevant test in the test
dbaron@2974 1133 suite should have an equivalent test created if such a user
dbaron@2974 1134 agent (UA) is to be used to claim interoperability. In addition
dbaron@2974 1135 if such a UA is to be used to claim interoperability, then there
dbaron@2974 1136 must one or more additional UAs which can also pass those
dbaron@2974 1137 equivalent tests in the same way for the purpose of
dbaron@2974 1138 interoperability. The equivalent tests must be made publicly
dbaron@2974 1139 available for the purposes of peer review.
dbaron@2974 1140
dbaron@2974 1141 <dt>implementation <dd>a user agent which:
dbaron@2974 1142
dbaron@2974 1143 <ol class=inline>
dbaron@2974 1144 <li>implements the specification.
dbaron@2974 1145
dbaron@2974 1146 <li>is available to the general public. The implementation may
dbaron@2974 1147 be a shipping product or other publicly available version
dbaron@2974 1148 (i.e., beta version, preview release, or “nightly build”).
dbaron@2974 1149 Non-shipping product releases must have implemented the
dbaron@2974 1150 feature(s) for a period of at least one month in order to
dbaron@2974 1151 demonstrate stability.
dbaron@2974 1152
dbaron@2974 1153 <li>is not experimental (i.e., a version specifically designed
dbaron@2974 1154 to pass the test suite and is not intended for normal usage
dbaron@2974 1155 going forward).
dbaron@2974 1156 </ol>
dbaron@2974 1157 </dl>
dbaron@2974 1158
dbaron@2974 1159 <p>The specification will remain Candidate Recommendation for at least
dbaron@2974 1160 six months.
dbaron@2974 1161
fantasai@6831 1162 <h2 id="changes">
fantasai@6831 1163 Changes</h2>
dbaron@2974 1164
fantasai@6831 1165 <p>The following (non-editorial) changes were made to this specification since the
fantasai@6831 1166 <a href="http://www.w3.org/TR/2012/WD-css3-conditional-20120911/">11 September 2012 Working Draft</a>:
fantasai@6831 1167
fantasai@6831 1168 <ul>
fantasai@6846 1169 <li>Removed ''@document'' rule; it has been deferred to Level 4.
fantasai@6845 1170 <li>Allow functional notation in ''@supports'' queries to be valid (to allow for future extensions),
fantasai@6845 1171 but treat such notations as always being false.
fantasai@6831 1172 <li>Corrected the grammar as follows:
fantasai@6831 1173 <pre>
fantasai@6831 1174 - : SUPPORTS_SYM S+ supports_condition group_rule_body
fantasai@6831 1175 + : SUPPORTS_SYM S* supports_condition group_rule_body
fantasai@6831 1176 </pre>
fantasai@6842 1177 <pre>
fantasai@6842 1178 - : (URI | FUNCTION) S*
fantasai@6842 1179 + : (URI | FUNCTION S* STRING S* ')' ) S*
fantasai@6842 1180 </pre>
fantasai@6842 1181 <li>Switched "and", "or", and "not" keywords to use appropriate productions rather than literals.
fantasai@6846 1182 <li>Clarified definition of support used for interpreting ''@support'' rules
fantasai@6846 1183 and its relationship to CSS forwards-compatible parsing rules.
fantasai@6831 1184 </ul>
dbaron@2974 1185
jackalmage@6617 1186 <h2 class=no-num id="acknowledgments">Acknowledgments</h2>
dbaron@2974 1187
dbaron@2974 1188 <p>
dbaron@2974 1189 Thanks to the ideas and feedback from
dbaron@3418 1190 Tab Atkins,
dbaron@2974 1191 <span lang="tr">Tantek Çelik</span>,
dbaron@3418 1192 Alex Danilo,
dbaron@2974 1193 Elika Etemad,
dbaron@2974 1194 Pascal Germroth,
dbaron@2974 1195 <span lang="de">Björn Höhrmann</span>,
dbaron@3417 1196 Paul Irish,
dbaron@7044 1197 <span lang="nl">Anne van Kesteren</span>,
dbaron@3418 1198 Vitor Menezes,
dbaron@2977 1199 Alex Mogilevsky,
dbaron@2974 1200 Chris Moschini,
dbaron@6740 1201 Simon Sapin,
dbaron@2974 1202 Ben Ward,
dbaron@2974 1203 Zack Weinberg,
dbaron@3430 1204 Estelle Weyl,
dbaron@2974 1205 Boris Zbarsky,
dbaron@2974 1206 and all the rest of the <a href="http://lists.w3.org/Archives/Public/www-style/">www-style</a> community.
dbaron@2974 1207
dbaron@2974 1208 </p>
dbaron@2974 1209
jackalmage@6617 1210 <h2 class=no-num id="references">References</h2>
dbaron@2974 1211
dbaron@2974 1212
jackalmage@6617 1213 <h3 class="no-num" id="normative-references">Normative references</h3>
dbaron@2974 1214 <!--normative-->
dbaron@2974 1215
jackalmage@6617 1216 <h3 class="no-num" id="other-references">Other references</h3>
dbaron@2974 1217 <!--informative-->
dbaron@2974 1218
jackalmage@6617 1219 <h2 class="no-num" id="index">Index</h2>
dbaron@2974 1220 <!--index-->
dbaron@2974 1221
dbaron@2974 1222 </body>
dbaron@2974 1223 </html>
dbaron@2974 1224 <!-- Keep this comment at the end of the file
dbaron@2974 1225 Local variables:
dbaron@2974 1226 mode: sgml
dbaron@2974 1227 sgml-declaration:"~/SGML/HTML4.decl"
dbaron@2974 1228 sgml-default-doctype-name:"html"
dbaron@2974 1229 sgml-minimize-attributes:t
dbaron@2974 1230 sgml-nofill-elements:("pre" "style" "br")
dbaron@2974 1231 sgml-live-element-indicator:t
dbaron@2974 1232 sgml-omittag:nil
dbaron@2974 1233 sgml-shorttag:nil
dbaron@2974 1234 sgml-namecase-general:t
dbaron@2974 1235 sgml-general-insert-case:lower
dbaron@2974 1236 sgml-always-quote-attributes:t
dbaron@2974 1237 sgml-indent-step:nil
dbaron@2974 1238 sgml-indent-data:t
dbaron@2974 1239 sgml-parent-document:nil
dbaron@2974 1240 sgml-exposed-tags:nil
dbaron@2974 1241 sgml-local-catalogs:nil
dbaron@2974 1242 sgml-local-ecat-files:nil
dbaron@2974 1243 End:
dbaron@2974 1244 -->
dbaron@2974 1245

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