- From: John Daggett via cvs-syncmail <cvsmail@w3.org>
- Date: Tue, 01 Mar 2011 07:44:16 +0000
- To: public-css-commits@w3.org
Update of /sources/public/csswg/css3-fonts
In directory hutz:/tmp/cvs-serv28117
Modified Files:
Fonts.html
Log Message:
revised vertical-position
Index: Fonts.html
===================================================================
RCS file: /sources/public/csswg/css3-fonts/Fonts.html,v
retrieving revision 1.38
retrieving revision 1.39
diff -u -d -r1.38 -r1.39
--- Fonts.html 24 Feb 2011 12:53:04 -0000 1.38
+++ Fonts.html 1 Mar 2011 07:44:14 -0000 1.39
@@ -111,14 +111,14 @@
<h1>CSS Fonts Module Level 3</h1>
- <h2 class="no-num no-toc" id=editors>Editor's Draft 24 February 2011</h2>
+ <h2 class="no-num no-toc" id=editors>Editor's Draft 1 March 2011</h2>
<dl id=authors>
<dt>This version:
<dd><a
href="http://dev.w3.org/csswg/css3-fonts/">http://dev.w3.org/csswg/css3-fonts/</a>
- <!-- <dd><a href="http://www.w3.org/TR/2011/ED-css3-fonts-20110224">http://www.w3.org/TR/2011/ED-css3-fonts-20110224</a> -->
+ <!-- <dd><a href="http://www.w3.org/TR/2011/ED-css3-fonts-20110301">http://www.w3.org/TR/2011/ED-css3-fonts-20110301</a> -->
<dt>Latest version:
@@ -2770,16 +2770,24 @@
<h3 id=char-handling-issues><span class=secno>5.2 </span>Character handling
issues</h3>
- <p>The procedure above does not assume that text runs are in either
- normalized or denormalized form <a href="#UAX15"
- rel=biblioentry>[UAX15]<!--{{!UAX15}}--></a>. Layout engines often convert
- base character plus combining character sequences into precomposed
- codepoints if they exist. Fonts can generally support both ways of
- matching characters but variations can occur. Authors should always tailor
- their choice of fonts to their content, including whether that content
- contains normalized or denormalized character streams.
+ <p>The procedure above is always performed on text runs containing Unicode
+ characters, documents using legacy encodings are assumed to have been
+ transcoded before matching fonts. For fonts containing character maps for
+ both legacy encodings and Unicode, the contents of the legacy encoding
+ character map must have no effect on the results of the font matching
+ process.
- <p>If a text run contains variation selectors, special handling is
+ <p>The font matching process does not assume that text runs are in either
+ normalized or denormalized form (see <a href="#CHARMOD-NORM"
+ rel=biblioentry>[CHARMOD-NORM]<!--{{!CHARMOD-NORM}}--></a> for more
+ details). Layout engines often convert base character plus combining
+ character sequences into precomposed characters if they exist. Fonts can
+ generally support both ways of matching characters but variations can
+ occur. Authors should always tailor their choice of fonts to their
+ content, including whether that content contains normalized or
+ denormalized character streams.
+
+ <p>If a text run contains Unicode variation selectors, special handling is
required. For each character + variation selector pair, if the first font
with a glyph for the base character also contains a glyph for the variant
specified by the variation selector, user agents must display the variant
@@ -3104,18 +3112,73 @@
<p class=issue>Issue: the name for this feature has been a point of
contention. The name used here is taken from the AAT feature name but the
- eventual name for this is still under discussion.
+ eventual name may change.
<p>The values ‘<code class=property>subscript</code>’, ‘<code
- class=property>superscript</code>’ and ‘<code
+ class=property>superscript</code>’, and ‘<code
class=property>ordinal</code>’ imply the appropriate variant glyph is
displayed when available in the font (OpenType features: <code>subs, supr,
- ordn</code>). When a variant glyph is not available, a simulated version
- is synthesized using a reduced form of the default glyph. Normal implies
- use of the default glyph at normal size. When the value is anything other
- than ‘<code class=property>normal</code>’, the font-size and
- vertical-align properties are set to ‘<code
- class=property>inherit</code>’.</p>
+ ordn</code>). Because of the semantic nature of subscripts and
+ superscripts, when the value is either ‘<code
+ class=property>subscript</code>’ or ‘<code
+ class=property>superscript</code>’ and a variant glyph is not available,
+ a simulated glyph is synthesized using a reduced form of the default
+ glyph. If the value is ‘<code class=property>ordinal</code>’ and a
+ variant glyph is not available, the normal glyph is used, no attempt is
+ made to synthesize one. A value of ‘<code
+ class=property>normal</code>’ implies use of the default glyph at normal
+ size.
+
+ <p>In the past, user agents have used font-size and vertical-align to
+ simulate subscripts and superscripts for the <code>sub</code> and
+ <code>sup</code> elements. To allow a backwards combatible way of defining
+ subscripts and superscripts, when the value is either ‘<code
+ class=property>subscript</code>’ or ‘<code
+ class=property>superscript</code>’, the property acts as a shorthand and
+ resets the value of the font-size and vertical-align properties to
+ ‘<code class=property>inherit</code>’. Other than this, the property
+ does not affect the height of the line box.
+
+ <div class=example>
+ <p>A typical user agent default style for the <code>sub</code> element:</p>
+
+ <pre>sub {
+ vertical-align: sub;
+ font-size: smaller;
+ line-height: normal;
+}
+</pre>
+
+ <p>Using vertical-position to specify typographic subscripts in a way that
+ will still show subscripts in older user agents:</p>
+
+ <pre>sub {
+ vertical-align: sub;
+ font-size: smaller;
+ line-height: normal;
+ vertical-position: subscript;
+}
+</pre>
+
+ <p>User agents that support the ‘<code class=property><a
+ href="#propdef-vertical-position">vertical-position</a></code>’
+ property will select a subscript variant glyph and reset vertical-align
+ and font-size to ‘<code class=property>inherit</code>’. Older user
+ agents will ignore the vertical-position property definition and use the
+ standard defaults for subscripts.</p>
+ </div>
+
+ <p>Note that because this property is not cumulative, it's not suitable for
+ nested subscripts or superscripts. Due to this limitation,
+ vertical-position is not recommended for use in user agent stylesheets.
+
+ <p>In the case of OpenType fonts that lack subscript or superscript glyphs,
+ to calculate the size and offset of the synthesized substitutes user
+ agents must use the appropriate subscript and superscript metrics
+ specified in the selected font's <a
+ href="http://www.microsoft.com/typography/otspec/os2.htm#subxs">OS/2
+ table</a> <a href="#OPENTYPE"
+ rel=biblioentry>[OPENTYPE]<!--{{OPENTYPE}}--></a>.</p>
<!-- prop: font-variant-ligatures -->
<h3 id=font-variant-ligatures-prop><span class=secno>6.5 </span>Ligatures:
@@ -4547,13 +4610,33 @@
</dd>
<!---->
+ <dt id=CHARMOD>[CHARMOD]
+
+ <dd>Martin J. Dürst; et al. <a
+ href="http://www.w3.org/TR/2005/REC-charmod-20050215"><cite>Character
+ Model for the World Wide Web 1.0: Fundamentals.</cite></a> 15 February
+ 2005. W3C Recommendation. URL: <a
+ href="http://www.w3.org/TR/2005/REC-charmod-20050215">http://www.w3.org/TR/2005/REC-charmod-20050215</a>
+ </dd>
+ <!---->
+
+ <dt id=CHARMOD-NORM>[CHARMOD-NORM]
+
+ <dd>François Yergeau; et al. <a
+ href="http://www.w3.org/TR/2005/WD-charmod-norm-20051027"><cite>Character
+ Model for the World Wide Web 1.0: Normalization.</cite></a> 27 October
+ 2005. W3C Working Draft. (Work in progress.) URL: <a
+ href="http://www.w3.org/TR/2005/WD-charmod-norm-20051027">http://www.w3.org/TR/2005/WD-charmod-norm-20051027</a>
+ </dd>
+ <!---->
+
<dt id=CORS>[CORS]
<dd>Anne van Kesteren. <a
- href="http://www.w3.org/TR/2010/WD-cors-20100727"><cite>Cross-Origin
+ href="http://www.w3.org/TR/2010/WD-cors-20100727/"><cite>Cross-Origin
Resource Sharing.</cite></a> 27 July 2010. W3C Working Draft. (Work in
progress.) URL: <a
- href="http://www.w3.org/TR/2010/WD-cors-20100727">http://www.w3.org/TR/2010/WD-cors-20100727</a>
+ href="http://www.w3.org/TR/2010/WD-cors-20100727/">http://www.w3.org/TR/2010/WD-cors-20100727/</a>
</dd>
<!---->
@@ -4598,19 +4681,20 @@
<dt id=UAX15>[UAX15]
<dd>Mark Davis. <a
- href="http://www.unicode.org/reports/tr15/"><cite>Unicode Normalization
- Forms.</cite></a> 17 September 2010. Unicode Standard Annex #15. URL: <a
- href="http://www.unicode.org/reports/tr15/">http://www.unicode.org/reports/tr15/</a>
+ href="http://www.unicode.org/reports/tr15/tr15-33.html"><cite>Unicode
+ Normalization Forms.</cite></a> 17 September 2010. Unicode Standard Annex
+ #15. URL: <a
+ href="http://www.unicode.org/reports/tr15/tr15-33.html">http://www.unicode.org/reports/tr15/tr15-33.html</a>
</dd>
<!---->
<dt id=UAX29>[UAX29]
<dd>Mark Davis. <a
- href="http://www.unicode.org/reports/tr29/"><cite>Unicode Text
- Segmentation.</cite></a> 8 October 2010. Unicode Standard Annex #29. URL:
- <a
- href="http://www.unicode.org/reports/tr29/">http://www.unicode.org/reports/tr29/</a>
+ href="http://www.unicode.org/reports/tr29/tr29-17.html"><cite>Unicode
+ Text Segmentation.</cite></a> 8 October 2010. Unicode Standard Annex #29.
+ URL: <a
+ href="http://www.unicode.org/reports/tr29/tr29-17.html">http://www.unicode.org/reports/tr29/tr29-17.html</a>
</dd>
<!---->
@@ -4634,6 +4718,8 @@
<!--{{!UAX29}}-->
<!--{{!CORS}}-->
<!--{{!HTML5}}-->
+ <!--{{!CHARMOD}}-->
+ <!--{{!CHARMOD-NORM}}-->
<h3 class=no-num id=other-references>Other References</h3>
<!--begin-informative-->
@@ -4674,6 +4760,15 @@
ISBN 1-932026-01-0.</dd>
<!---->
+ <dt id=OPENTYPE>[OPENTYPE]
+
+ <dd><a
+ href="http://www.microsoft.com/typography/otspec/default.htm"><cite>OpenType
+ specification.</cite></a> Microsoft. URL: <a
+ href="http://www.microsoft.com/typography/otspec/default.htm">http://www.microsoft.com/typography/otspec/default.htm</a>
+ </dd>
+ <!---->
+
<dt id=OPENTYPE-FONT-GUIDE>[OPENTYPE-FONT-GUIDE]
<dd><a
Received on Tuesday, 1 March 2011 07:44:19 UTC