drafts: css3-conditional/Overview.src.html@eb9aa921aa39

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     6   <title>CSS Conditional Rules Module Level 3</title>

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    15 <h1>CSS Conditional Rules Module Level 3</h1>

    17 <h2 class="no-num no-toc">[LONGSTATUS] [DATE]</h2>

    18 <dl>

    19   <dt>This version:

    20     <dd><a href="[VERSION]">

    21     http://www.w3.org/TR/[YEAR]/ED-css3-conditional-[CDATE]/</a>

    23   <dt>Latest version:

    24     <dd><a href="http://www.w3.org/TR/[SHORTNAME]/">http://www.w3.org/TR/[SHORTNAME]/</a>

    26   <dt>Editor's draft:

    27     <dd><a href="http://dev.w3.org/csswg/[SHORTNAME]/">http://dev.w3.org/csswg/[SHORTNAME]/</a>

    29   <dt>Previous version:

    30     <dd><a href="http://www.w3.org/TR/2011/WD-css3-conditional-20110901/">http://www.w3.org/TR/2011/WD-css3-conditional-20110901/</a></dd>

    32   <dt>Editors:

    33     <dd class=vcard><a class=fn href="http://dbaron.org/">L. David Baron</a>,

    34       <a class=org href="http://www.mozilla.org/">Mozilla</a>

    36   <dt>Issues list:

    37     <dd>Maintained in document (only editor's draft is current)

    39     <dt>Feedback:

    41     <dd><a

    42      href="http://lists.w3.org/Archives/Public/www-style/">www-style@w3.org</a>

    43      with subject line “<kbd>&#x5b;[SHORTNAME]&#x5d; <var>… message topic

    44      …</var></kbd>”

    46   <dt>Test suite:

    47     <dd><a href="https://test.csswg.org/shepherd/search/spec/css3-conditional/">submitted tests</a>; no built test suite yet

    49 </dl>

    51 <!--copyright-->

    53 <hr title="Separator for header">

    54 </div>

    56 <h2 class="no-num no-toc" id="abstract">Abstract</h2>

    58   <p>CSS is a language for describing the rendering of structured documents

    59   (such as HTML and XML) on screen, on paper,  in speech, etc. This module

    60   contains the features of CSS for conditional processing of parts of

    61   style sheets, conditioned on capabilities of the processor or the

    62   document the style sheet is being applied to.

    63   It includes and extends the functionality of CSS level&nbsp;2 [[!CSS21]],

    64   which builds on CSS level&nbsp;1 [[CSS1]].

    65   The main extensions compared to level&nbsp;2 are

    66   allowing nesting of certain at-rules inside '@media',

    67   the addition of the '@supports' and '@document'

    68   rules for conditional processing.

    70 <h2 class="no-num no-toc" id="status">Status of this document</h2>

    72 <!--status-->

    74 <p>The following features are at risk:

    75 <ul>

    76   <li>The inclusion of '@font-face' rules and

    77   '@keyframes' rules as allowed within all of the @-rules in

    78   this specification is at risk, though only because of the relative

    79   rates of advancement of specifications.  If this specification is able

    80   to advance faster than one or both of the specifications defining

    81   those rules, then the inclusion of those rules will move from this

    82   specification to the specification defining those rules.</li>

    84   <li>The addition of support for @-rules inside of conditional grouping

    85   rules is at risk; if interoperable implementations are not found, it

    86   may be removed to advance the other features in this specification to

    87   Proposed Recommendation.</li>

    89   <li>The '@supports' rule is at risk; if interoperable

    90   implementations are not found, it may be removed to advance the other

    91   features in this specification to Proposed Recommendation.</li>

    93   <li>The '@document' rule is at risk; if interoperable

    94   implementations are not found, it may be removed to advance the other

    95   features in this specification to Proposed Recommendation.</li>

    97 </ul>

    99 <h2 class="no-num no-toc" id="contents">Table of contents</h2>

   101 <!--toc-->

   103 <h2 id="introduction">Introduction</h2>

   105 <h3 id="context">Background</h3>

   107   <p><em>This section is not normative.</em>

   109   <p>[[!CSS21]] defines one type of conditional group rule, the

   110   '@media' rule, and allows only rulesets (not other @-rules)

   111   inside of it.  The '@media' rule provides the ability to

   112   have media-specific style sheets, which is also provided by style

   113   sheet linking features such as '@import' and

   114   <code class="html">&lt;link&gt;</code>.  The restrictions on the contents of

   115   '@media' rules made them less useful; they have forced authors

   116   using CSS features involving @-rules in media-specific style sheets to

   117   use separate style sheets for each medium.</p>

   119   <p>This specification extends the rules for the contents of

   120   conditional group rules to allow other @-rules, which enables authors

   121   to combine CSS features involving @-rules with media specific style

   122   sheets within a single style sheet.</p>

   124   <p>This specification also defines additional types of conditional

   125   group rules, '@supports' and '@document', to

   126   address author and user requirements.</p>

   128   <p>The '@supports' rule allows CSS to be conditioned on

   129   implementation support for CSS properties and values.  This rule makes

   130   it much easier for authors to use new CSS features and provide good

   131   fallback for implementations that do not support those features.  This

   132   is particularly important for CSS features that provide new layout

   133   mechanisms, and for other cases where a set of related styles needs to

   134   be conditioned on property support.</p>

   136   <p>The '@document' rule allows CSS to be conditioned on the

   137   page to which the style sheet is being applied.  This allows users to

   138   apply styles to a particular page or group of pages, which greatly

   139   increases the power of user style sheets.</p>

   141 <h3 id="placement">Module Interactions</h3>

   143   <p>This module replaces and extends the '@media' rule

   144   feature defined in [[!CSS21]] section <var>7.2.1</var> and

   145   incorporates the modifications previously made non-normatively by

   146   [[!MEDIAQ]] section <var>1</var>.</p>

   148   <p>Its current definition depends on @-rules defined in [[!CSS3-FONTS]]

   149   and [[!CSS3-ANIMATIONS]], but that dependency is only on the

   150   assumption that those modules will advance ahead of this one.  If this

   151   module advances faster, then the dependency will be reversed.</p>

   153 <h3 id="conventions">Document Conventions</h3>

   155   <p>Conformance requirements are expressed with a combination of

   156   descriptive assertions and RFC 2119 terminology. The key words “MUST”,

   157   “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”,

   158   “RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this

   159   document are to be interpreted as described in RFC 2119.

   160   However, for readability, these words do not appear in all uppercase

   161   letters in this specification.

   163   <p>All of the text of this specification is normative except sections

   164   explicitly marked as non-normative, examples, and notes. [[!RFC2119]]</p>

   166   <p>Examples in this specification are introduced with the words “for example”

   167   or are set apart from the normative text with

   168   <code class="html">class="example"</code>, like this:

   170   <div class="example">

   171     <p>This is an example of an informative example.</p>

   172   </div>

   174   <p>Informative notes begin with the word “Note” and are set apart from the

   175   normative text with <code class="html">class="note"</code>, like this:

   177   <p class="note">Note, this is an informative note.</p>

   179 <h2 id="processing">Processing of conditional group rules</h2>

   181 <p>This specification defines some CSS @-rules, called <dfn>conditional

   182 group rules</dfn>, that associate a condition with a group of other

   183 CSS rules.  These different rules allow testing different types of

   184 conditions, but share common behavior for how their contents are used

   185 when the condition is true and when the condition is false.</p>

   187 <div class="example">

   188 <p>For example, this rule:</p>

   189 <pre>@media print {

   190   #navigation { display: none }

   191 }</pre>

   192 <p>causes a particular CSS rule (making elements with ID "navigation" be

   193 display:none) apply only when the style sheet is used for a print

   194 medium.  Likewise, this CSS rule:</p>

   195 <pre>@document url("http://www.example.com/") {

   196   #example1 { display: none }

   197 }</pre>

   198 <p>does the same type of conditional application, but using a different

   199 condition:  whether the style sheet is being applied to the page

   200 <code>http://www.example.com/</code>.</p>

   201 </div>

   203 <p>Each conditional group rule has a condition, which at any time

   204 evaluates to true or false.  When the condition is true, CSS processors

   205 <strong>must</strong> apply the rules inside the group rule as though

   206 they were at the group rule's location; when the condition is false, CSS

   207 processors <strong>must not</strong> apply any of rules inside the group

   208 rule.  The current state of the condition does not affect the CSS object

   209 model, in which the contents of the group rule always remain within the

   210 group rule.</p>

   212 <p>This means that when multiple conditional group rules are nested,

   213 a rule inside of both of them applies only when all of the rules'

   214 conditions are true.</p>

   216 <div class="example">For example, with this set of nested rules:

   217 <pre>@media print { // rule (1)

   218   #navigation { display: none }

   219   @media (max-width: 12cm) { // rule (2)

   220     .note { float: none }

   221   }

   222 }</pre>

   223 the condition of the rule marked (1) is true for print media, and the

   224 condition of the rule marked (2) is true when the width of the display

   225 area (which for print media is the page box) is less than or equal to

   226 12cm.  Thus the rule ''#navigation { display: none }'' applies

   227 whenever this style sheet is applied to print media, and the rule

   228 ''.note { float: none }'' is applied only when the style sheet

   229 is applied to print media <em>and</em> the width of the page box is less

   230 than or equal to 12 centimeters.</div>

   232 <p>When the condition for a conditional group rule changes, CSS

   233 processors <strong>must</strong> reflect that the rules now apply or no

   234 longer apply, except for properties whose definitions define effects of

   235 computed values that persist past the lifetime of that value (such as

   236 for some properties in [[CSS3-TRANSITIONS]] and

   237 [[!CSS3-ANIMATIONS]]).</p>

   239 <h2 id="contents-of">Contents of conditional group rules</h2>

   241 <p class="issue">There is also likely demand for using these

   242 conditions with '@import'.  We should see if we can

   243 come up with sensible syntax for that, perhaps functional notation

   244 at the end of the '@import' rule.</p>

   246 <p>The syntax of each conditional group rule consists of some syntax

   247 specific to the type of rule followed by a <dfn>group rule body</dfn>,

   248 which is a block (pair of braces) containing a sequence of rules.</p>

   250 <p>A group rule body is allowed to contain rulesets and any @-rules that

   251 are allowed at the top level of a style sheet before and after a

   252 ruleset.  This means that @-rules that must occur at the beginning of

   253 the style sheet (such as '@charset', '@import',

   254 and '@namespace' rules) are not allowed inside of conditional group

   255 rules.  Conditional group rules can be nested.</p>

   257 <p>In terms of the grammar, this specification defines the following

   258 productions for use in the grammar of conditional group rules:</p>

   260 <pre>nested_statement

   261   : ruleset | media | page | font_face_rule | keyframes_rule |

   262     supports_rule | document_rule

   263   ;

   265 group_rule_body

   266   : '{' S* nested_statement* '}' S*

   267   ;</pre>

   268 <p>

   269 in which all the productions are defined in that grammar with the

   270 exception of <code>font_face_rule</code> <span class="issue">not</span>

   271 defined in [[!CSS3-FONTS]], <code>keyframes_rule</code> defined in

   272 [[!CSS3-ANIMATIONS]], and <code>media</code>, <code>supports_rule</code>

   273 and <code>document_rule</code> defined in this specification.</p>

   275 <p>In general, future CSS specifications that add new @-rules that are

   276 not forbidden to occur after some other types of rules should modify

   277 this <code>nested_statement</code> production to keep the grammar

   278 accurate.</p>

   280 <p>Style sheets <strong>must not</strong> use rules other than the allowed ones inside

   281 conditional group rules.</p>

   283 <p>CSS processors <strong>must</strong> ignore rules that are not

   284 allowed within a group rule, and <strong>must</strong> handle invalid

   285 rules inside of group rules as described in <a

   286 href="http://www.w3.org/TR/CSS21/syndata.html#parsing-errors">section

   287 4.2 (Rules for handling parsing errors)</a>, <a

   288 href="http://www.w3.org/TR/CSS21/syndata.html#at-rules">section 4.1.5

   289 (At-rules)</a>, and <a

   290 href="http://www.w3.org/TR/CSS21/syndata.html#rule-sets">section 4.1.7

   291 (Rule sets, declaration blocks, and selectors)</a> of [[!CSS21]].</p>

   293 <h2 id="use">Placement of conditional group rules</h2>

   295 <p>Conditional group rules are allowed at the top-level of a style

   296 sheet, and inside other conditional group rules.  CSS processors

   297 <strong>must</strong> process such rules as <a

   298 href="#processing">described above</a>.</p>

   300 <p>Any rules that are not allowed after a ruleset (e.g., ''@charset'',

   301 ''@import'', or ''@namespace'' rules) are also not allowed after a

   302 conditional group rule.  Therefore, style sheets <strong>must

   303 not</strong> place such rules after a conditional group rules, and CSS

   304 processors <strong>must</strong> ignore such rules.</p>

   306 <h2 id="at-media">Media-specific style sheets:  the '@media' rule</h2>

   308 <p>The <dfn>'@media' rule</dfn> is a conditional group rule whose

   309 condition is a media query.  It consists of the at-keyword

   310 '@media' followed by a (possibly empty) media query list (as

   311 defined in [[!MEDIAQ]]), followed by a group rule body.  The condition

   312 of the rule is the result of the media query.</p>

   314 <div class="example">

   315 <p>This '@media' rule:</p>

   316 <pre>@media print, (max-width: 600px) {

   317   #extra_navigation { display: none }

   318 }</pre>

   319 <p>has the condition ''print, (max-width: 600px)'', which is

   320 true for print media and for devices whose width is at most 600px.  When

   321 either of these is true, the condition of the rule is true, and the rule

   322 ''#extra_navigation { display: none }'' is applied.

   323 </div>

   325 <p>In terms of the grammar, this specification extends the

   326 <code>media</code> production in the

   327 <a href="http://www.w3.org/TR/CSS21/grammar.html">Grammar of CSS 2.1</a>

   328 ([[!CSS21]], Appendix G) into:

   329 <pre>media

   330   : MEDIA_SYM S* media_query_list group_rule_body

   331   ;</pre>

   332 <p>where the <code>group_rule_body</code> production is defined in this

   333 specification, the <code>media_query_list</code> production is defined

   334 in [[!MEDIAQ]], and the others are defined in the <a

   335 href="http://www.w3.org/TR/CSS21/grammar.html">Grammar of CSS 2.1</a>

   336 ([[!CSS21]], Appendix G).

   338 <h2 id="at-supports">Feature queries: the '@supports' rule</h2>

   340 <p>The <dfn>'@supports' rule</dfn> is a conditional group

   341 rule whose condition tests whether the user agent supports CSS

   342 property:value pairs.  Authors can use it to write style sheets that use

   343 new features when available but degrade gracefully when those features

   344 are not supported.  CSS has existing mechanisms for graceful

   345 degradation, such as ignoring unsupported properties or values, but

   346 these are not always sufficient when large groups of styles need to be

   347 tied to the support for certain features, as is the case for use of new

   348 layout system features.</p>

   350 <p>The syntax of the condition in the '@supports' rule is

   351 slightly more complicated than for the other conditional group rules

   352 (though has some similarities to media queries) since:</p>

   353 <ul>

   354   <li>negation is needed so that the new-feature styles and the fallback

   355   styles can be separated (within the forward-compatible grammar's rules

   356   for the syntax of @-rules), and not required to override each other</li>

   357   <li>conjunction (and) is needed so that multiple required features can

   358   be tested</li>

   359   <li>disjunction (or) is needed when there are multiple alternative

   360   features for a set of styles, particularly when some of those

   361   alternatives are vendor-prefixed properties or values</li>

   362 </ul>

   364 <p>Therefore, the syntax of the '@supports' rule allows

   365 testing for property:value pairs, and arbitrary conjunctions (and),

   366 disjunctions (or), and negations (not) of them.</p>

   368 <p>This extends the lexical scanner in the

   369 <a href="http://www.w3.org/TR/CSS21/grammar.html">Grammar of CSS 2.1</a>

   370 ([[!CSS21]], Appendix G) by adding:

   371 <pre>@{S}{U}{P}{P}{O}{R}{T}{S}	{return SUPPORTS_SYM;}</pre>

   372 <p>and the grammar by adding</p>

   373 <pre><dfn>supports_rule</dfn>

   374   : SUPPORTS_SYM S* supports_condition group_rule_body

   375   ;

   377 <dfn>supports_condition</dfn>

   378   : supports_negation | supports_conjunction | supports_disjunction |

   379     supports_condition_in_parens

   380   ;

   382 <dfn>supports_condition_in_parens</dfn>

   383   : ( '(' S* supports_condition ')' S* ) | supports_declaration_condition

   384   ;

   386 <dfn>supports_negation</dfn>

   387   : 'not' S* supports_condition_in_parens

   388   ;

   390 <dfn>supports_conjunction</dfn>

   391   : supports_condition_in_parens ( 'and' S* supports_condition_in_parens )+

   392   ;

   394 <dfn>supports_disjunction</dfn>

   395   : supports_condition_in_parens ( 'or' S* supports_condition_in_parens )+

   396   ;

   398 <dfn>supports_declaration_condition</dfn>

   399   : '(' S* core_declaration ')' S*

   400   ;</pre>

   401 <p>in which <code>core_declaration</code> is the production

   402 <code>declaration</code> in the core syntax of CSS defined in <a

   403 href="http://www.w3.org/TR/CSS21/syndata.html#tokenization">section

   404 4.1.1 (Tokenization)</a> of [[!CSS21]].</p>

   406 <p>Any ''@supports'' rule that does not parse according to the grammar

   407 above is invalid.  Style sheets <strong>must not</strong> use such a

   408 rule and processors <strong>must</strong> ignore such a rule.</p>

   410 <p class="note">Note that this means that declarations that meet the

   411 forward-compatible syntax for declarations are permitted (and support

   412 for them is then tested by the ''@supports'' rule), but declarations

   413 that do not meet the forward-compatible syntax for declarations cause

   414 the entire ''@supports'' rule to be ignored.</p>

   416 <p class="issue">Is any further allowance for forward-compatible parsing

   417 needed, for example, to allow additional features (such as, say,

   418 selector tests) to be added to the ''@supports'' rule?  Or are these

   419 forward-compatible parsing rules the best solution for such future

   420 expansion anyway?</p>

   422 <p>Each of these grammar terms is associated with a boolean result, as

   423 follows:</p>

   424 <dl>

   425 <dt>supports_condition</dt>

   426 <dd>

   427   The result is the result of the single child term.

   428 </dd>

   430 <dt>supports_condition_in_parens</dt>

   431 <dd>

   432   The result is the result of the single <code>supports_condition</code>

   433   or <code>supports_declaration_condition</code> child term.

   434 </dd>

   436 <dt>supports_negation</dt>

   437 <dd>

   438   The result is the <em>negation</em> of the result of the

   439   <code>supports_condition_in_parens</code> child term.

   440 </dd>

   442 <dt>supports_conjunction</dt>

   443 <dd>

   444   The result is true if the result of <em>all</em> of the

   445   <code>supports_condition_in_parens</code> child terms is true;

   446   otherwise it is false.

   447 </dd>

   449 <dt>supports_disjunction</dt>

   450 <dd>

   451   The result is true if the result of <em>any</em> of the

   452   <code>supports_condition_in_parens</code> child terms is true;

   453   otherwise it is false.

   454 </dd>

   456 <dt>supports_declaration_condition</dt>

   457 <dd>

   458   The result is whether the CSS processor <a

   459   href="#support-definition">supports</a> the declaration.

   460 </dd>

   461 </dl>

   463 <p>The condition of the '@supports' rule is the result of the

   464 <code>supports_condition</code> term that is a child of the

   465 <code>supports_rule</code> term.</p>

   467 <div class="example">

   468 <p>For example, the following rule</p>

   469 <pre>@supports ( display: flexbox ) {

   470   body, #navigation, #content { display: flexbox; }

   471   #navigation { background: blue; color: white; }

   472   #article { background: white; color: black; }

   473 }</pre>

   474 <p>applies the rules inside the '@supports' rule only when

   475 ''display: flexbox'' is supported.</p>

   476 </div>

   478 <div class="example">

   479 <p>The following example shows an additional '@supports' rule that can

   480 be used to provide an alternative for when ''display: flexbox'' is not

   481 supported:</p>

   482 <pre>@supports not ( display: flexbox ) {

   483   body { width: 100%; height: 100%; background: white; color: black; }

   484   #navigation { width: 25%; }

   485   #article { width: 75%; }

   486 }</pre>

   487 <p>Note that the 'width' declarations may be harmful to the

   488 flexbox-based layout, so it is important that they be present only in

   489 the non-flexbox styles.</p>

   490 </div>

   492 <div class="example">

   493 <p>The following example checks for support for the 'box-shadow'

   494 property, including checking for support for vendor-prefixed versions of

   495 it.  When the support is present, it specifies both 'box-shadow' (with

   496 the prefixed versions) and 'color' in a way what would cause the text to

   497 become invisible were 'box-shadow' not supported.</p>

   498 <pre>@supports ( box-shadow: 2px 2px 2px black ) or

   499           ( -moz-box-shadow: 2px 2px 2px black ) or

   500           ( -webkit-box-shadow: 2px 2px 2px black ) or

   501           ( -o-box-shadow: 2px 2px 2px black ) {

   502   .outline {

   503     color: white;

   504     -moz-box-shadow: 2px 2px 2px black;

   505     -webkit-box-shadow: 2px 2px 2px black;

   506     -o-box-shadow: 2px 2px 2px black;

   507     box-shadow: 2px 2px 2px black; /* unprefixed last */

   508   }

   509 }</pre></div>

   511 <p>To avoid confusion between ''and'' and ''or'', the syntax requires

   512 that both ''and'' and ''or'' be specified explicitly (rather than, say,

   513 using commas or spaces for one of them).  Likewise, to avoid confusion

   514 caused by precedence rules, the syntax does not allow ''and'', ''or'',

   515 and ''not'' operators to be mixed without a layer of parentheses.</p>

   517 <div class="example">

   518 <p>For example, the following rule is not valid:

   519 <pre class="illegal">@supports (transition-property: color) or

   520           (animation-name: foo) and

   521           (transform: rotate(10deg)) {

   522   // ...

   523 }</pre>

   524 <p>Instead, authors must write one of the following:</p>

   525 <pre>@supports ((transition-property: color) or

   526            (animation-name: foo)) and

   527           (transform: rotate(10deg)) {

   528   // ...

   529 }</pre>

   530 <pre>@supports (transition-property: color) or

   531           ((animation-name: foo) and

   532            (transform: rotate(10deg))) {

   533   // ...

   534 }</pre>

   535 </div>

   537 <p>The declaration being tested must always occur within parentheses,

   538 when it is the only thing in the expression.<p>

   540 <div class="example">

   541 <p>For example, the following rule is not valid:

   542 <pre class="illegal">@supports display: flexbox {

   543   // ...

   544 }</pre>

   545 <p>Instead, authors must write:</p>

   546 <pre>@supports (display: flexbox) {

   547   // ...

   548 }</pre>

   549 </div>

   551 <p>The syntax allows extra parentheses when they are not needed.  This

   552 flexibility is sometimes useful for authors (for example, when

   553 commenting out parts of an expression) and may also be useful for

   554 authoring tools.</p>

   556 <div class="example">

   557 <p>For example, authors may write:</p>

   558 <pre>@supports ((display: flexbox)) {

   559   // ...

   560 }</pre>

   561 </div>

   563 <p>A trailing ''!important'' on a declaration being tested is allowed,

   564 though it won't change the validity of the declaration.

   566 <div class="example">

   567 <p>For example, the following rule is valid:

   568 <pre>@supports (display: flexbox !important) {

   569   // ...

   570 }</pre>

   571 </div>

   573 <h3 id="support-definition">Definition of support</h3>

   575 <p>For forward-compatibility,

   576 <a href="http://www.w3.org/TR/CSS21/syndata.html#declaration">section 4.1.8

   577 (Declarations and properties)</a> of [[!CSS21]]

   578 defines rules for handling invalid properties and values.

   579 CSS processors that

   580 do not implement or partially implement a specification

   581 <strong>must</strong> treat any part of a value that they

   582 do not implement, or

   583 do not have a usable level of support for,

   584 as invalid according to this rule

   585 for handling invalid properties and values,

   586 and therefore <strong>must</strong> discard the declaration as a parse error.</p>

   588 <p>A CSS processor is considered to <dfn id="dfn-support">support</dfn>

   589 a declaration (consisting of a property and value) if it accepts that

   590 declaration (rather than discarding it as a parse error).

   591 If a processor does not implement, with a usable level of support,

   592 the value given,

   593 then it <strong>must not</strong>

   594 accept the declaration or claim support for it.</p>

   596 <p>These rules (and the equivalence between them) allow

   597 authors to use fallback (either in the [[CSS1]] sense of declarations

   598 that are overridden by later declarations or with the new capabilities

   599 provided by the ''@supports'' rule in this specification) that works

   600 correctly for the features implemented.  This applies especially to

   601 compound values; implementations must implement all parts of the value

   602 in order to consider the declaration supported, either inside a ruleset

   603 or in the declaration condition of an ''@supports'' rule.</p>

   605 <h2 id="at-document">Document queries: the '@document' rule</h2>

   607 <p>The <dfn>'@document' rule</dfn> is a conditional group

   608 rule whose condition depends on the

   609 <a href="#url-of-doc">URL of the document being styled</a>.

   610 This allows style sheets, particularly user style sheets, to have styles

   611 that only apply to a set of pages rather than to all pages using the

   612 style sheet.</p>

   614 <p class="issue">Given that this @-rule is intended primarily for user

   615 style sheets, what should this specification say about its use in author

   616 style sheets?  Should it be forbidden?  Should use instead be

   617 discouraged?  Or should this specification remain neutral on the

   618 topic, since there are valid uses in author style sheets?</p>

   620 <p id="url-of-doc">The <dfn>URL of the document being styled</dfn> is

   621 the URI at which the document is located, excluding any fragment

   622 identifiers.  (This means, for example, that HTTP redirects have been

   623 followed.)  If the styles are being applied inside a complete document

   624 embedded into the presentation of another (e.g., [[HTML5]]&#39;s <code

   625 class="html">iframe</code>, <code class="html">object</code>, or <code

   626 class="html">img</code> elements), the relevant URI is that of the

   627 frame, not of its container.  However, if content from other documents

   628 is mixed in via mechanisms that mix content from one document into

   629 another (e.g., [[SVG11]]&#39;s <code>use</code> element), then the

   630 address of the container document is used.</p>

   632 <p class="note">Note:  In [[HTML5]], this is the

   633 <a href="http://dev.w3.org/html5/spec/dom.html#documents">document's address</a>

   634 of a document in a

   635 <a href="http://dev.w3.org/html5/spec/browsers.html#browsing-context">browsing context</a>.</p>

   637 <div class="issue">What form of normalization is done on URLs and domains

   638 before matching?  In particular, this specification needs to describe:

   639 <ul>

   640 <li>what form is used for the <a href="#url-of-doc">URL of the document

   641 being styled</a> (and what has been normalized in that form)</li>

   642 <li>what normalization (if any) happens to the argument of each of the match

   643 functions before the comparison that they describe and</li>

   644 <li>whether the

   645 comparison algorithm used is string comparison or some other URL

   646 comparison algorithm.</li></ul></div>

   648 <p>The '@document' rule's condition is written as a

   649 comma-separated list of <dfn>URL matching functions</dfn>, and the

   650 condition evaluates to true whenever any one of those functions

   651 evaluates to true.  The following URL matching functions are

   652 permitted:</p>

   654 <dl>

   655   <dt><dfn id="url-exact" title="url()|URL matching functions::exact">&lt;url&gt;</dfn></dt>

   657   <dd>

   658     <p>The 'url()' function is the <dfn>exact url matching

   659     function</dfn>.  It evaluates to true whenever the <a

   660     href="#url-of-doc">URL of the document being styled</a> is exactly

   661     the URL given.</p>

   663     <p class="Note">The 'url()' function, since it is a core syntax

   664     element in CSS, is allowed (subject to different character

   665     limitations and thus escaping requirements) to contain an unquoted

   666     value (in addition to the string values that are allowed as

   667     arguments for all four functions).</p>

   669     <div class="example">

   670       <p>For example, this rule:</p>

   671 <pre>@document url("http://www.w3.org/Style/CSS/") {

   672   #summary { background: yellow; color: black}

   673 }</pre>

   674       <p>styles the <code class="html">summary</code> element on the page

   675       <code>http://www.w3.org/Style/CSS/</code>, but not on any other

   676       pages.</p>

   677     </div>

   678   </dd>

   680   <dt><dfn id="url-prefix" title="url-prefix()|URL matching functions::prefix">url-prefix(&lt;string&gt;)</dfn></dt>

   682   <dd>

   683     <p>The 'url-prefix()' function is the <dfn>url prefix

   684     matching function</dfn>.  It evaluates to true whenever the

   685     <a href="#url-of-doc">URL of the document being styled</a>

   686     has the argument to the function as an

   687     initial substring (which is true when the two strings are equal).

   688     When the argument is the empty string, it evaluates to true for all

   689     documents.</p>

   690     <div class="example">

   691       <p>For example, this rule:</p>

   692 <pre>@document url-prefix("http://www.w3.org/Style/CSS/") {

   693   #summary { background: yellow; color: black}

   694 }</pre>

   695       <p>styles the <code class="html">summary</code> element on the page

   696       <code>http://www.w3.org/Style/CSS/</code> and on the page

   697       <code>http://www.w3.org/Style/CSS/Test</code>, but it does not

   698       affect the page <code>http://www.w3.org/</code> or the page

   699       <code>http://www.example.com/Style/CSS/</code>.</p>

   700     </div>

   701   </dd>

   703   <dt><dfn id="url-domain" title="domain()|URL matching functions::domain">domain(&lt;string&gt;)</dfn></dt>

   705   <dd>

   706     <p>The 'domain()' function is the <dfn>domain

   707     matching function</dfn>.  It evaluates to true whenever

   708     the <a href="#url-of-doc">URL of the document being styled</a>

   709     has a host subcomponent (as defined in [[!URI]])

   710     and that host subcomponent is exactly the argument to the

   711     'domain()' function or a final substring of the host

   712     component is a period (U+002E) immediately followed by the argument

   713     to the 'domain()' function.</p>

   714     <div class="example">

   715       <p>For example, this rule:</p>

   716 <pre>@document domain("w3.org") {

   717   body { font-size: 16px ! important }

   718 }</pre>

   719       <p>changes the font size of the body element for pages such as

   720       <code>http://www.w3.org/Style/CSS/</code> and

   721       <code>http://w3.org/Style/CSS/</code> and

   722       <code>http://lists.w3.org/Archives/Public/www-style/</code>

   723       but it does not affect the page

   724       <code>http://www.example.com/Style/CSS/</code>.</p>

   725     </div>

   726   </dd>

   728   <dt><dfn id="url-regexp" title="regexp()|URL matching functions::regular expression">regexp(&lt;string&gt;)</dfn></dt>

   730   <dd>

   731     <p>The contents of the &lt;string&gt; argument <strong>must</strong>

   732     match the JavaScript <code>Pattern</code> production

   733     ([[!ECMA-262-5.1]], section 15.10.1).  However,

   734     failing to do so is not a CSS syntax error and does not trigger any

   735     error handling for CSS syntax errors.</p>

   737     <p>The ''regexp()'' function evaluates to true whenever the string

   738     argument compiled as a JavaScript regular expression with the

   739     <code>global</code>, <code>ignoreCase</code> and

   740     <code>multiline</code> flags <em>disabled</em>

   741     (see [[!ECMA-262-5.1]], sections 15.10.7.2 through 15.10.7.4)

   742     compiles successfully and the resulting regular expression matches

   743     the entirety of the

   744     <a href="#url-of-doc">URL of the document being styled</a>.</p>

   746     <p class="note">Note that regular expression must match the entire

   747     URL, not just a part of it.</p>

   749     <p class="note">Note that this definition intentionally matches the

   750     behavior of the <a

   751     href="http://dev.w3.org/html5/spec/common-input-element-attributes.html#attr-input-pattern"><code class="html">pattern</code>

   752     attribute</a> on the <code class="html">input</code> element

   753     in [[HTML5]].</p>

   755     <div class="example">

   756       <p>For example, this rule:</p>

   757 <pre>@document regexp("http://www.w3.org/TR/\\d{4}/[^/]*-CSS2-\\d{8}/") {

   758   body { font-size: 20px ! important }

   759 }</pre>

   760       <p>changes the font size of the body element for pages such as

   761       <code>http://www.w3.org/TR/2011/PR-CSS2-20110412/</code>.</p>

   762       <p class="note">Note that the backslashes in the regular

   763       expression require CSS escaping as ''\\''.</p>

   764     </div>

   765   </dd>

   767 </dl>

   769 <p>Implementations <strong>must</strong> treat any unknown URL matching

   770 functions as a syntax error, and thus ignore the '@document' rule.

   771 <span class="issue">Should we instead have more complicated error

   772 handling rules to make forward-compatibility work differently, or is

   773 this rule the best solution for such future expansion anyway?</span></p>

   775 <div class="issue">This syntax doesn't offer any ability to do negations,

   776 which has been requested in <a

   777 href="https://bugzilla.mozilla.org/show_bug.cgi?id=349813">Mozilla bug

   778 349813</a>.  Use cases that people have wanted negations for

   779 include:

   780 <ul>

   781   <li>User style sheets that want a particular rule in general, but know

   782   that that rule does more harm than good on specific sites.</li>

   783   <li>Authors who have a rule that they want to apply to most of their

   784   pages, but wish to make a few exceptions for.</li>

   785 </ul>

   786 </div>

   788 <p>This extends the lexical scanner in the

   789 <a href="http://www.w3.org/TR/CSS21/grammar.html">Grammar of CSS 2.1</a>

   790 ([[!CSS21]], Appendix G) by adding:

   791 <pre>@{D}{O}{C}{U}{M}{E}{N}{T}	{return DOCUMENT_SYM;}</pre>

   792 <p>and the grammar by adding</p>

   793 <pre>document_rule

   794   : DOCUMENT_SYM S+ url_match_fn ( "," S* url_match_fn )* group_rule_body

   795   ;

   797 url_match_fn

   798   : (URI | FUNCTION S* STRING S* ')' ) S*

   799   ;</pre>

   801 <h2 id="apis">APIs</h2>

   803 <h3 id='extentions-to-cssrule-interface'>

   804 Extensions to the <code>CSSRule</code> interface</h3>

   806 <p>The <code>CSSRule</code> interface is extended as follows:

   808 <pre class='idl'>partial interface CSSRule {

   809     const unsigned short SUPPORTS_RULE = 12;

   810     const unsigned short DOCUMENT_RULE = 13;

   811 }</pre>

   814 <h3 id='the-cssgroupingrule-interface'>

   815 The <code>CSSGroupingRule</code> interface</h3>

   817 <p>The <dfn><code>CSSGroupingRule</code></dfn> interface represents an at-rule that contains other rules nested inside itself.

   819 <pre class='idl'>interface CSSGroupingRule : CSSRule {

   820     readonly attribute CSSRuleList cssRules;

   821     unsigned long insertRule (DOMString rule, unsigned long index);

   822     void deleteRule (unsigned long index);

   823 }</pre>

   825 <dl class='idl-attributes'>

   826   <dt><code>cssRules</code> of type <code>CSSRuleList</code>, readonly

   827   <dd>The <code>cssRules</code> attribute must return a <code>CSSRuleList</code>

   828     object for the list of CSS rules nested inside the grouping rule.

   829 </dl>

   831 <dl class='idl-methods'>

   832   <dt><code>insertRule(DOMString rule, unsigned long index)</code>, returns

   833     <code>unsigned long</code>

   834   <dd>The <code>insertRule</code> operation must insert a CSS rule <var>rule</var>

   835     into the CSS rule list returned by <code>cssRules</code> at <var>index</var>.

   837   <dt><code>deleteRule (unsigned long index)</code>, return <code>void</code>

   838   <dd>The <code>deleteRule</code> operation must remove a CSS rule from the

   839     CSS rule list returned by <code>cssRules</code> at <var>index</var>.

   840 </dl>

   843 <h3 id="the-cssconditionrule-interface">

   844 The <code>CSSConditionRule</code> interface</h3>

   846 <p>The <dfn><code>CSSConditionRule</code></dfn> interface represents all the "conditional" at-rules,

   847   which consist of a condition and a statement block.

   849 <pre class='idl'>interface CSSConditionRule : CSSGroupingRule {

   850     attribute DOMString conditionText;

   851 }</pre>

   853 <dl class='idl-attributes'>

   855   <dt><code>conditionText</code> of type <code>DOMString</code>

   856   <dd>

   857     <p>The <code>conditionText</code> attribute represents

   858     the condition of the rule.

   859     Since what this condition does

   860     varies between the derived interfaces of <code>CSSConditionRule</code>,

   861     those derived interfaces

   862     may specify different behavior for this attribute

   863     (see, for example, <code>CSSMediaRule</code> below).

   864     In the absence of such rule-specific behavior,

   865     the following rules apply:</p>

   867     <p>The <code>conditionText</code> attribute, on getting, must return

   868     the result of serializing the associated condition.

   870     <p>On setting the <code>conditionText</code> attribute these steps

   871       must be run:

   873     <ol>

   874       <li>Trim the given value of white space.

   875       <li>If the given value matches the grammar of the

   876         appropriate condition production for the given rule,

   877         replace the associated CSS condition with the given value.

   878       <li>Otherwise, do nothing.

   879     </ol>

   880 </dl>

   883 <h3 id="the-cssmediarule-interface">

   884 The <code>CSSMediaRule</code> interface</h3>

   886 <p>The <dfn><code>CSSMediaRule</code></dfn> interface represents a ''@media'' rule:

   888 <pre class='idl'>interface CSSMediaRule : CSSConditionRule {

   889     readonly attribute MediaList media;

   890 }</pre>

   892 <dl class='idl-attributes'>

   893   <dt><code>media</code> of type <code>MediaList</code>, readonly

   894   <dd>The <code>media</code> attribute must return a <code>MediaList</code> object

   895     for the list of media queries specified with the ''@media'' rule.

   897   <dt><code>conditionText</code> of type <code>DOMString</code>

   898   <dd>The <code>conditionText</code> attribute (defined on the <code>CSSConditionRule</code> parent rule),

   899     on getting, must return the value of <code>media.mediaText</code> on the rule.

   901     <p>Setting the <code>conditionText</code> attribute

   902       must set the <code>media.mediaText</code> attribute on the rule.

   903 </dl>

   906 <h3 id="the-csssupportsrule-interface">

   907 The <code>CSSSupportsRule</code> interface</h3>

   909 <p>The <dfn><code>CSSSupportsRule</code></dfn> interface represents a ''@supports'' rule.</p>

   911 <pre class='idl'>interface CSSSupportsRule : CSSConditionRule {

   912 }</pre>

   915 <h3 id="the-cssdocumentrule-interface">

   916 The <code>CSSDocumentRule</code> interface</h3>

   918 <p>The <dfn><code>CSSDocumentRule</code></dfn> interface represents a ''@document'' rule.</p>

   920 <pre class='idl'>interface CSSDocumentRule : CSSConditionRule {

   921 }</pre>

   924 <h3 id='the-css-interface'>

   925 The <code>CSS</code> interface, and the <code title=''>supports()</code> function</h3>

   927 <p>The <dfn id='CSS-interface'><code>CSS</code></dfn> interface holds useful CSS-related functions that do not belong elsewhere.

   929 <pre class='idl'>interface CSS {

   930   boolean supports(DOMString property, DOMString value);

   931   boolean supports(DOMString declaration);

   932 }</pre>

   934 <dl class='idl-methods'>

   935   <dt><code>supports(DOMString property, DOMString value)</code>,

   936     returns <code>boolean</code>

   937   <dt><code>supports(DOMString conditionText)</code>,

   938     returns <code>boolean</code>

   939   <dd>

   940     When the <code title=''>supports()</code> method is invoked with two arguments <var>property</var> and <var>value</var>,

   941     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,

   942     and <var>value</var> would be successfully parsed as a supported value for that property.

   943     Otherwise, it must return <code>false</code>.

   945     <p>

   946       When invoked with a single <var>conditionText</var> argument,

   947       it must return <code>true</code> if <var>conditionText</var>,

   948       when parsed and evaluated as a <code>supports_condition</code>,

   949       would return true.

   950       Otherwise, it must return <code>false</code>.

   951   </dl>

   954 <h2 id="conformance">Conformance</h2>

   956 <h3 id="base-modules">Base Modules</h3>

   958 <p>This specification defines conformance in terms of base modules,

   959 which are modules that this specification builds on top of.  The base

   960 modules of this module are:</p>

   962 <ul>

   963 <li>[[!CSS21]]</li>

   964 </ul>

   966 <p>All of the conformance requirements of all base modules are

   967 incorporated as conformance requirements of this module, except where

   968 overridden by this module.</p>

   970 <p>Additionally, all conformance requirements related to validity of

   971 syntax in this module and all of its base modules are to be interpreted

   972 as though all syntax in all of those modules is valid.</p>

   974 <div class="example"><p>For example, this means that grammar presented

   975 in modules other than [[!CSS21]] must obey the requirements that

   976 [[!CSS21]] defines for the parsing of properties, and that requirements

   977 for handling invalid syntax in [[!CSS21]] do not treat syntax added by

   978 other modules as invalid.</p></div>

   980 <p>Additionally, the set of valid syntax can be increased by the

   981 conformance of a style sheet or processor to additional modules; use of

   982 such syntax does not make a style sheet nonconformant and failure to

   983 treat such syntax as invalid does not make a processor

   984 nonconformant.</p>

   986 <h3 id="conformance-classes">Conformance Classes</h3>

   988   <p>Conformance to the CSS Conditional Rules Module is defined for three

   989   conformance classes:

   990   <dl>

   991     <dt><dfn title="conformance::style sheet" id="conform-style-sheet">style sheet</dfn>

   992       <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS

   993       style sheet</a>.</dd>

   994     <dt><dfn title="conformance::processor" id="conform-processor">processor</dfn></dt>

   995       <dd>A tool that reads CSS style sheets:  it may be a renderer or

   996       <a

   997       href="http://www.w3.org/TR/CSS21/conform.html#user-agent">user-agent</a>

   998       that interprets the semantics of a style sheet and renders

   999       documents that use style sheets, or it may be a validator that

  1000       checks style sheets.</dd>

  1001     <dt><dfn title="conformance::authoring tool" id="conform-authoring-tool">authoring tool</dfn></dt>

  1002       <dd>A tool that writes a style sheet.</dd>

  1003   </dl>

  1005   <p>A style sheet is conformant to the CSS Conditional Rules Module

  1006   if it meets all of the conformance requirements in the module that are

  1007   described as requirements of style sheets.</p>

  1009   <p>A processor is conformant to the CSS Conditional Rules Module if it

  1010   meets all applicable conformance requirements in the module that are

  1011   described as requirements of processors.  In general, all requirements

  1012   are applicable to renderers.  Requirements concerning a part of CSS

  1013   not performed by a processor are not applicable, e.g., requirements

  1014   related to rendering are not applicable to a validator.  The inability

  1015   of a processor to correctly render a document due to limitations of

  1016   the device does not make it non-conformant. (For example, a renderer

  1017   is not required to render color on a monochrome monitor.)</p>

  1019   <p>An authoring tool is conformant to the CSS Conditional Rules Module

  1020   if it writes style sheets that conform to the module and (if it reads

  1021   CSS) it is a conformant processor.</p>

  1023 <h3 id="partial">

  1024 Partial Implementations</h3>

  1026   <p>So that authors can exploit the forward-compatible parsing rules to

  1027   assign fallback values, CSS renderers <strong>must</strong>

  1028   treat as invalid (and <a href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignore

  1029   as appropriate</a>) any at-rules, properties, property values, keywords,

  1030   and other syntactic constructs for which they have no usable level of

  1031   support. In particular, user agents <strong>must not</strong> selectively

  1032   ignore unsupported component values and honor supported values in a single

  1033   multi-value property declaration: if any value is considered invalid

  1034   (as unsupported values must be), CSS requires that the entire declaration

  1035   be ignored.</p>

  1037 <h3 id="experimental">Experimental Implementations</h3>

  1039   <p>To avoid clashes with future CSS features, the CSS specifications

  1040   reserve a <a href="http://www.w3.org/TR/CSS21/syndata.html#vendor-keywords">prefixed

  1041   syntax</a> for proprietary property and value extensions to CSS. The CSS

  1042   Working Group recommends that experimental implementations of features in

  1043   CSS Working Drafts also use vendor-prefixed property or value names. This

  1044   avoids any incompatibilities with future changes in the draft. Once a

  1045   specification reaches the Candidate Recommendation stage, implementors

  1046   should implement the non-prefixed syntax for any feature they consider to

  1047   be correctly implemented according to spec.</p>

  1049 <h3 id="cr-exit-criteria">CR Exit Criteria</h3>

  1051   <p>For this specification to be advanced to Proposed Recommendation,

  1052   there must be at least two independent, interoperable implementations

  1053   of each feature. Each feature may be implemented by a different set of

  1054   products, there is no requirement that all features be implemented by

  1055   a single product. For the purposes of this criterion, we define the

  1056   following terms:

  1058   <dl>

  1059     <dt>independent <dd>each implementation must be developed by a

  1060     different party and cannot share, reuse, or derive from code

  1061     used by another qualifying implementation. Sections of code that

  1062     have no bearing on the implementation of this specification are

  1063     exempt from this requirement.

  1065     <dt>interoperable <dd>passing the respective test case(s) in the

  1066     official CSS test suite, or, if the implementation is not a Web

  1067     browser, an equivalent test. Every relevant test in the test

  1068     suite should have an equivalent test created if such a user

  1069     agent (UA) is to be used to claim interoperability. In addition

  1070     if such a UA is to be used to claim interoperability, then there

  1071     must one or more additional UAs which can also pass those

  1072     equivalent tests in the same way for the purpose of

  1073     interoperability. The equivalent tests must be made publicly

  1074     available for the purposes of peer review.

  1076     <dt>implementation <dd>a user agent which:

  1078     <ol class=inline>

  1079       <li>implements the specification.

  1081       <li>is available to the general public. The implementation may

  1082       be a shipping product or other publicly available version

  1083       (i.e., beta version, preview release, or “nightly build”).

  1084       Non-shipping product releases must have implemented the

  1085       feature(s) for a period of at least one month in order to

  1086       demonstrate stability.

  1088       <li>is not experimental (i.e., a version specifically designed

  1089       to pass the test suite and is not intended for normal usage

  1090       going forward).

  1091     </ol>

  1092   </dl>

  1094   <p>The specification will remain Candidate Recommendation for at least

  1095   six months.

  1097 <h2 class=no-num id="grammar">Grammar</h2>

  1099 <p>In order to allow these new @-rules in CSS style sheets, this

  1100 specification modifies the <code>stylesheet</code> production in the <a

  1101 href="http://www.w3.org/TR/CSS21/grammar.html">Appendix G</a> grammar of

  1102 [[!CSS21]] by replacing the <code>media</code> production defined in

  1103 [[!CSS21]] with the <code>media</code> production defined in this one,

  1104 and additionally inserting <code>| supports_rule | document_rule</code>

  1105 alongside <code>ruleset | media | page</code>.</p>

  1107 <h2 class=no-num id="acknowledgments">Acknowledgments</h2>

  1109 <p>

  1110 Thanks to the ideas and feedback from

  1111 Tab Atkins,

  1112 <span lang="tr">Tantek Çelik</span>,

  1113 Alex Danilo,

  1114 Elika Etemad,

  1115 Pascal Germroth,

  1116 <span lang="de">Björn Höhrmann</span>,

  1117 Paul Irish,

  1118 Vitor Menezes,

  1119 Alex Mogilevsky,

  1120 Chris Moschini,

  1121 Simon Sapin,

  1122 Ben Ward,

  1123 Zack Weinberg,

  1124 Estelle Weyl,

  1125 Boris Zbarsky,

  1126 and all the rest of the <a href="http://lists.w3.org/Archives/Public/www-style/">www-style</a> community.

  1128 </p>

  1130 <h2 class=no-num id="references">References</h2>

  1133 <h3 class="no-num" id="normative-references">Normative references</h3>

  1134 <!--normative-->

  1136 <h3 class="no-num" id="other-references">Other references</h3>

  1137 <!--informative-->

  1139 <h2 class="no-num" id="index">Index</h2>

  1140 <!--index-->

  1142 </body>

  1143 </html>

  1144 <!-- Keep this comment at the end of the file

  1145 Local variables:

  1146 mode: sgml

  1147 sgml-declaration:"~/SGML/HTML4.decl"

  1148 sgml-default-doctype-name:"html"

  1149 sgml-minimize-attributes:t

  1150 sgml-nofill-elements:("pre" "style" "br")

  1151 sgml-live-element-indicator:t

  1152 sgml-omittag:nil

  1153 sgml-shorttag:nil

  1154 sgml-namecase-general:t

  1155 sgml-general-insert-case:lower

  1156 sgml-always-quote-attributes:t

  1157 sgml-indent-step:nil

  1158 sgml-indent-data:t

  1159 sgml-parent-document:nil

  1160 sgml-exposed-tags:nil

  1161 sgml-local-catalogs:nil

  1162 sgml-local-ecat-files:nil

  1163 End:

  1164 -->

Mercurial > drafts / file revision

css3-conditional/Overview.src.html@eb9aa921aa39

css3-conditional/Overview.src.html