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[css2] Added optional whitespace after hexadecimal escape sequence.
--HG-- extra : convert_revision : svn%3A73dc7c4b-06e6-40f3-b4f7-9ed1dbc14bfc/trunk%40858
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‎css2/syndata.src‎

Lines changed: 68 additions & 139 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,6 @@
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<html lang="en">
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<!-- $Id: syndata.src,v 2.2 1998-02-10 22:28:42 ijacobs Exp $ -->
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<!-- $Id: syndata.src,v 2.3 1998-02-10 23:45:01 bbos Exp $ -->
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<HEAD>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<TITLE>CSS2 syntax and basic data types</TITLE>
@@ -73,7 +73,7 @@ multiple matches, the longest match determines the token.
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<TR><TD>ident <TD><code><var>{nmstart}{nmchar}*</var></code>
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<TR><TD>nmstart <TD><code>[a-zA-Z]|<var>{nonascii}</var>|<var>{escape}</var></code>
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<TR><TD>nonascii<TD><code>[^\0-\4177777]</code>
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<TR><TD>unicode <TD><code>\\[0-9a-f]{1,6}</code>
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<TR><TD>unicode <TD><code>\\[0-9a-f]{1,6}[ \n\r\t\f]?</code>
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<TR><TD>escape <TD><code>{unicode}|\\[ -~\200-\4177777]</code>
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<TR><TD>nmchar <TD><code>[a-z0-9-]|<var>{nonascii}</var>|<var>{escape}</var></code>
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<TR><TD>num <TD><code>[0-9]+|[0-9]*\.[0-9]+</code>
@@ -82,6 +82,8 @@ multiple matches, the longest match determines the token.
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<TR><TD>string2 <TD><code>\'([\t !#$%&amp;(-~]|\\\n|\"|<var>{nonascii}</var>|<var>{escape}</var>)*\'</code>
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</TABLE>
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<!-- optional whitespace after \unicode OIK? -->
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<P>Below is the core syntax for CSS. The sections that follow describe
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how to use it. <a href="grammar.html">Appendix B</a> describes a
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more restrictive grammar that is closer to the CSS level 2 language.
@@ -149,15 +151,12 @@ href="#escaped-characters">escaped characters.</a>
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<LI> <a name="escaped-characters">The backslash</a> (\) followed
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by at most six hexadecimal digits (0..9A..F) stands for the <a
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rel="biblioentry" href="./refs.html#ref-ISO10646">[ISO10646]</a>
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character with that number. The first space following the
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hexadecimal sequence is ignored. This allows authors to avoid
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ambiguities between, for example, hexadecimal "\26C" and
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hexadecimal "\26" followed immediately by the letter "C".
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character with that number.
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<LI> Any character except a hexadecimal digit can be escaped to
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remove its special meaning, by putting a backslash (\) in front,
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For example, <samp>"\""</samp> is a string consisting of one
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double quote.
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double quote.
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<LI> The two preceding items define <span class="index-inst"
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title="backslash
@@ -545,16 +544,14 @@ display to a laser printer).
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</PRE>
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</div>
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<P>The 'em' unit refers to the <span class="index-def"
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title="em-height"><a name="em-height"><dfn>em-height</dfn></a></span>.
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In CSS, the em-height is equal to the <span class="index-inst"
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title="font size">font size</span> used when rendering an element's
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text. It may be used for vertical or horizontal measurement. The 'ex'
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unit is equal to the font's <span class="index-def"
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title="x-height"><dfn>x-height</dfn></span> (the height of the letter
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'x') of the element's font. A font need not contain the letter "M" to
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have an 'em' size or the letter "x" to have an x-height; the font
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should still define the two units.
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<P>The 'em' unit, as used in CSS, is equal to the <span
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class="index-inst" title="font size">font size</span> used when
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rendering an element's text. It may be used for vertical or horizontal
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measurement. The 'ex' unit is equal to the font's <span
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class="index-def" title="x-height"><dfn>x-height</dfn></span> (the
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height of the letter 'x') of the element's font. A font need not
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contain the letter "M" to have an 'em' size or the letter "x" to have
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an x-height; the font should still define the two units.
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<!-- Incomplete -->
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@@ -607,7 +604,7 @@ href="cascade.html#computed-value">computed values</a>. For example:</p>
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<PRE>
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BODY {
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font-size: 12pt;
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text-indent: 3em; /* i.e., 36pt */
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text-indent: 3em; /* i.e. 36pt */
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}
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H1 { font-size: 15pt }
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</PRE>
@@ -648,12 +645,9 @@ is an optional sign character ('+' or '-', with '+' being the default)
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immediately followed by a number immediately followed by '%'.
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<P> Percentage values are always relative to another value, for
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example a length. Each property that allows percentages also defines
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the value to which the percentage refers. The value may be that of
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another property for the same element, a property for an ancestor
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element, or a value of the rendering context (e.g., the width of a <a
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href="visuren.html#containing-block">containing block</a>). When a
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percentage value is set for a property of the root of the <a
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example a length. Each property that allows percentages also
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defines to which value the percentage refers. When a percentage value
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is set for a property of the root of the <a
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href="conform.html#doctree">document tree</a> and the percentage is
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defined as referring to the inherited value of some property X, the
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resultant value is the percentage times the <a
@@ -668,7 +662,7 @@ the percentage value (120%):
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<PRE>
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P { font-size: 10pt }
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P { line-height: 120% } /* relative to 'font-size', i.e., 12pt */
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P { line-height: 120% } /* relative to 'font-size', i.e. 12pt */
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</PRE>
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</div>
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@@ -832,7 +826,7 @@ identifier is optional.
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<P>These following are legal angle unit identifiers:</p>
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<ul>
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<li><strong>deg</strong>: degrees
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<li><strong>deg</strong>: degrees.
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<LI><strong>grad</strong>: gradient
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<LI><strong>rad</strong>: radians
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</UL>
@@ -910,14 +904,15 @@ cannot occur inside double quotes, unless escaped (as '\"' or as
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<P>A string cannot directly contain a <span class="index-inst"
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title="newline">newline</span>. To include a newline in a string, use
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the escape "\A" (hexadecimal A is the line feed character in Unicode,
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but represents the generic notion of "newline" in CSS). Sometimes it
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but represents the generic notion of "newline" in CSS). <!--Sometimes it
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is safer to write "\00000A", since that will avoid the situation where
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the character following the "A" can be interpreted as a hexadecimal
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digit. For example, in the string
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<pre>"A. one\AB. two"</pre>
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<p>the UA will see an escape sequence "\AB" (&#171;) instead of \A.
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<p>the UA will see an escape sequence "\AB" (&#171;) instead of \A.-->
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See also <a href="#char-escapes">Character escapes in CSS</a> below.
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<p>It is possible to break strings over several lines, for aesthetic
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or other reasons, but in such a case the newline itself has to be
@@ -930,129 +925,63 @@ o very long title"] {border: double}
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A[TITLE="a not so very long title"] {border: double}
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</pre>
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<H2>CSS document representation</H2>
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<P>A CSS style sheet is a sequence of characters from the Universal
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Character Set, defined in <a rel="biblioentry"
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href="./refs.html#ref-ISO10646">[ISO10646]</a>. For transmission and
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storage, these characters must be <span class="index-def"
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title="character encoding">encoded</span> by a character encoding that
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supports the ASCII character set (e.g., ISO 8859-x, SHIFT JIS, etc.).
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For a good introduction to character sets and character encodings,
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please consult <a rel="biblioentry" href="./refs.html#ref-HTML40"
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class="informref">[HTML40]</a>, Chapter 5.
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<P>When a style sheet is embedded in another document, the style sheet
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shares the character encoding of the whole document. ("Embedded" here
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means textual inclusion, not embedded byte sequences.) For
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example, in <a rel="biblioentry" href="./refs.html#ref-HTML40"
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class="informref">[HTML40]</a>, the "charset" attribute of many
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elements (META, LINK, A, etc.) designates the character encoding, as
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in:</p>
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<pre>
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&lt;META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"&gt;
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</pre>
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<H2><a name="css-in-html">CSS embedded in HTML</a></H2>
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<P>When a style sheet resides in a separate file, user agents must
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observe the following <span class="index-inst" title="character
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encoding::user agent's determination of">priorities</span> when
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determining a document's <span class="index-inst" title="character
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encoding::default|default::character encoding">character
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encoding</span> (from highest priority to lowest):</p>
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<P> CSS style sheets may be embedded in HTML documents, and to be able
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to hide style sheets from older UAs, it is convenient put the style
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sheets inside HTML comments. Please consult <a rel="biblioentry"
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href="./refs.html#ref-HTML40" class="informref">[HTML40]</a> for more
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information.
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<ol>
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<li>An HTTP "charset" parameter in a "Content-Type" field.
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<li>The <span class="index-def" title="@charset">@charset</span>
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at-rule.
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<li>Mechanisms of the language of the
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referencing document (e.g., in HTML, the "charset"
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attribute of the LINK element).
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</ol>
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<P>When CSS is embedded in HTML, it shares the <tt>charset</tt>
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parameter used to transmit the enclosing HTML document. As with HTML,
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the value of the <tt>charset</tt> parameter is used to convert from
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the transfer encoding to the document character set, which is
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specified by <a rel="biblioentry"
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href="./refs.html#ref-ISO10646">[ISO10646]</a>.
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<P>When present, only one @charset rule may appear in an external
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style sheet -- it must <em>not</em> appear in an embedded style sheet
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-- and it must be the first line in the document (not preceded by any
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other characters). After "@charset", authors specify the name of a
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character encoding. The name must be a charset name as described in <a
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href="refs.html#ref-IANA" class="normref">[IANA]</a> registry (see <a
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rel="biblioentry" href="./refs.html#ref-CHARSETS"
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class="informref">[CHARSETS]</a> for a complete list). For
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example:</p>
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<H2><a name="css-by-itself">CSS as a stand-alone file</a></H2>
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<!-- Add reference to rfc2045? -->
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<div class="example"><P>
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@charset "ISO-8859-1";
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</div>
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<p>CSS style sheets may exist in files by themselves, being linked
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from the document. In this case, the CSS files are served with the
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media type <tt>text/css</tt>. As with all text media types, a
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<tt>charset</tt> parameter may be added which is used to convert from
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the transfer encoding to <a rel="biblioentry"
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href="./refs.html#ref-ISO10646">[ISO10646]</a>.
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<h2><a name="char-escapes">Character escapes in CSS</a></h2>
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<P>This specification does not mandate which character encodings
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a user agent must support.
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<P>What purpose does the @charset construct serve if user agents
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cannot understand it before they know the character encoding? It acts
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as a verification mechanism. In the case HTTP headers do not provide
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character encoding information, user agents may attempt to guess the
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character set, and should they succeed, the @charset allows them to
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double check their guess. For this reason, character encodings in
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which the ASCII characters are encoded as themselves are more likely
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to help user agents determine the correct character encoding than
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other encodings schemes.
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<!-- More examples of good encodings to use? -IJ -->
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<!-- Encodings not to use? (cf. HTML 4.0) -IJ -->
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<h3>Referring to characters not represented in a character encoding</h3>
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<P>A style sheet may have to refer to characters that cannot be
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represented in the current character encoding. These characters must
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be written as <a href="#escaped-characters">escaped</a> references to
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<a rel="biblioentry" href="./refs.html#ref-ISO10646">[ISO10646]</a>
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characters. These escapes are the equivalent of numeric character
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references in HTML or XML documents (see <a rel="biblioentry"
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href="./refs.html#ref-HTML40">[HTML40], Chapters 5 and 25).</a>
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<P>The character escape mechanism should be used when only a few
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characters must be represented this way. If most of a document
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requires escaping, authors should encode it with a more appropriate
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encoding (e.g., if the document contains a lot of Greek characters,
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authors might use ISO 8859-7 or UTF 8).
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<P>Intermediate processors using a different character encoding may
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translate these escaped sequences into byte sequences of that
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encoding. <strong>Note.</strong> Intermediate processors must not, on
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the other hand, alter escape sequences that cancel the special meaning
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of an ASCII character.
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<P><a href="conform.html#conformance">Conforming user agents</a> must
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correctly map to Unicode all characters in any character encodings
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that they recognize (or they must behave as if they did).
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<p>CSS may need to use characters that are outside the encoding used
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to transmit the document. For example, the "class" attribute of HTML
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allows more characters in a class name than the set allowed for
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selectors above. In CSS2, such characters can be <a
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href="#escaped-characters">escaped</a> or written as <a
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rel="biblioentry" href="./refs.html#ref-ISO10646">[ISO10646]</a>
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numbers.
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<P>For instance, "B&amp;W?" may be written as "B\&amp;W\?" or
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"B\26 W\3F". For example, a document transmitted as ISO-8859-1
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"B\26W\3F". For example, a document transmitted as ISO-8859-1
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(Latin-1) cannot contain Greek letters directly:
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"&#954;&#959;&#965;&#961;&#959;&#962;" (Greek: "kouros") has to be
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written as "\3BA\3BF\3C5\3C1\3BF\3C2".
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1036-
<div class="note"><P>
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<em><strong>Note.</strong>
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In <a rel="biblioentry" href="./refs.html#ref-HTML40"
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class="informref">[HTML40]</a>,
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numeric character references may appear in "style" attribute
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values but not in the content of the STYLE element. Because of this
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asymmetry, we recommend that authors use the CSS character
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escape mechanism rather than numeric character references.
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For example, authors should write:</em></p>
1045-
1046-
<pre class="html-example">
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&lt;SPAN style="voice-family: D\FCrst"&gt;...&lt;/SPAN&gt;
1048-
</pre>
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written as "\3BA\3BF\3C5\3C1\3BF\3C2". These escapes are thus the CSS
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equivalent of numeric character references in HTML or XML documents.
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1050-
<P><em>rather than:</em></p>
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<p class=note>[Is the following OK?]
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1052-
<pre class="html-example">
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&lt;SPAN style="voice-family: D&amp;amp;#FC;rst"&gt;...&lt;/SPAN&gt;
1054-
</pre>
1055-
</div>
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<p>If a digit or letter follows the hexadecimal number, the end of the
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number needs to be made clear. There are two ways to do that:
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<ol>
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<li>with a space (or other whitespace character): "\26 B" ("&B")
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<li>by providing exactly 6 hexadecimal digits: "\000026B" ("&B")
979+
</ol>
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<p>In fact, the two methods may be combined. Only one whitespace
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character is ignored after a hexadecimal escape. Note that this means
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that a "real" space after the escape sequence must itself either be
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escaped or doubled.
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</BODY>
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</html>

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