[css-fonts] fixups based on font-variant-*, minor comments II (but I'm not hyphenating subproperty dammit)

Author: John Daggett

css-fonts/Fonts.html

@@ -4408,11 +4408,22 @@ <h3 id=font-variant-alternates-prop><span class=secno>6.8 </span>Alternates
   font-variant-alternates: swash(flowing); /* use swash alternate #2 */
 }</pre>
 
-  <p>When a particular value has not been defined for a given family, the
-   named value is treated as if the feature had been omitted from the style
-   rule. If a given value is outside the range supported by a given font, the
-   value is ignored. These values never apply to generic font families, nor
-   to families selected as part of system font fallback.
+  <p>When a particular <code>&lt;feature-value-name&gt;</code> has not been
+   defined for a given family or for a particular feature type, the computed
+   value must be the same as if it had been defined. However, property values
+   that contain these undefined <code>&lt;feature-value-name&gt;</code>
+   identifiers must be ignored when choosing glyphs.
+
+  <pre>/* these two style rules are effectively the same */
+p { font-variant-alternates: swash(unknown-value); } /* not a defined value, ignored */
+p { font-variant-alternates: normal; }
+</pre>
+
+  <p>This allows values to be defined and used for a given set of font
+   families but ignored if fallback occurs, since the font family name would
+   be different. If a given value is outside the range supported by a given
+   font, the value is ignored. These values never apply to generic font
+   families.
 
   <p>Individual values have the following meanings:
 
@@ -4541,44 +4552,7 @@ <h3 id=font-feature-values><span class=secno>6.9 </span>Defining font
    values specified within a given font's data.
 
   <p>In terms of the grammar, this specification defines the following
-   productions:</p>
-  <!--
-<pre><dfn>supports_rule</dfn>
-  : <i>SUPPORTS_SYM</i> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <i>supports_condition</i> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <i>group_rule_body</i>
-  ;
-
-<dfn>supports_condition</dfn>
-  : <i>supports_negation</i> | <i>supports_conjunction</i> | <i>supports_disjunction</i> |
-    <i>supports_condition_in_parens</i>
-  ;
-
-<dfn>supports_condition_in_parens</dfn>
-  : ( '(' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <i>supports_condition</i> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* ')' ) | <i>supports_declaration_condition</i> |
-    <i>general_enclosed</i>
-  ;
-
-<dfn>supports_negation</dfn>
-  : <a href="http://www.w3.org/TR/css3-mediaqueries/#syntax"><i>NOT</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>+ <i>supports_condition_in_parens</i>
-  ;
-
-<dfn>supports_conjunction</dfn>
-  : <i>supports_condition_in_parens</i> ( <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>+ <a href="http://www.w3.org/TR/css3-mediaqueries/#syntax"><i>AND</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>+ <i>supports_condition_in_parens</i> )+
-  ;
-
-<dfn>supports_disjunction</dfn>
-  : <i>supports_condition_in_parens</i> ( <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>+ <i>OR</i> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>+ <i>supports_condition_in_parens</i> )+
-  ;
-
-<dfn>supports_declaration_condition</dfn>
-  : '(' <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>declaration</i></a> ')'
-  ;
-
-<dfn>general_enclosed</dfn>
-  : ( <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>FUNCTION</i></a> | '(' ) ( <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>any</i></a> | <a href="http://www.w3.org/TR/CSS21/syndata.html#tokenization"><i>unused</i></a> )* ')'
-  ;
-</pre>
-
--->
+   productions:
 
   <pre><dfn id=fontfeaturevaluesrule>font_feature_values_rule</dfn>
   : <a href="#fontfeaturevaluessym"><i>FONT_FEATURE_VALUES_SYM</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>* <a href="#fontfamilynamelist"><i>font_family_name_list</i></a> <a href="http://www.w3.org/TR/CSS21/grammar.html#scanner"><i>S</i></a>*
@@ -4952,20 +4926,21 @@ <h3 id=font-variant-east-asian-prop><span class=secno>6.10 </span>East
 
    <dd>Enables rendering of simplified forms (OpenType feature: <span
     class=tag>smpl</span>).
-    <p>The ‘<a href="#simplified"><code
-     class=property>simplified</code></a>’ and ‘<a
-     href="#traditional"><code class=property>traditional</code></a>’
-     values allow control over the glyph forms for characters which have been
-     simplified over time but for which the older, traditional form is still
-     used in some contexts. The exact set of characters and glyph forms will
-     vary to some degree by context for which a given font was designed.</p>
 
    <dt><dfn id=traditional>traditional</dfn>
 
    <dd>Enables rendering of traditional forms (OpenType feature: <span
     class=tag>trad</span>).
   </dl>
 
+  <p>The ‘<a href="#simplified"><code
+   class=property>simplified</code></a>’ and ‘<a
+   href="#traditional"><code class=property>traditional</code></a>’ values
+   allow control over the glyph forms for characters which have been
+   simplified over time but for which the older, traditional form is still
+   used in some contexts. The exact set of characters and glyph forms will
+   vary to some degree by context for which a given font was designed.
+
   <div class=featex><img alt="tradtional form example" src=trad.png></div>
 
   <dl>
@@ -5090,10 +5065,11 @@ <h3 id=font-variant-prop><span class=secno>6.11 </span>Overall shorthand
      <td>see individual properties
   </table>
 
-  <p>The value <dfn id=font-variant-normal-value
-   title="normal!!font-variant">‘<code
-   class=property>normal</code>’</dfn> resets all other font feature
-   properties to their inital value. The <dfn id=font-variant-none-value
+  <p>The ‘<code class=property>font-variant</code>’ property is a
+   shorthand for all font-variant subproperties. The value <dfn
+   id=font-variant-normal-value title="normal!!font-variant">‘<code
+   class=property>normal</code>’</dfn> resets all subproperties of
+   font-variant to their inital value. The <dfn id=font-variant-none-value
    title="none!!font-variant">‘<code class=property>none</code>’</dfn>
    value sets ‘<a href="#propdef-font-variant-ligatures"><code
    class=property>font-variant-ligatures</code></a>’ to ‘<code
@@ -5165,17 +5141,23 @@ <h3 id=font-feature-settings-prop><span class=secno>6.12 </span>Low-level
 
   <p>This property provides low-level control over OpenType font features. It
    is intended as a way of providing access to font features that are not
-   widely used but are needed for a particular use case. A value of <dfn
-   id=font-feature-settings-normal-value
-   title="normal!!font-feature-settings">‘<code
-   class=property>normal</code>’</dfn> means that no change in glyph
-   selection or positioning occurs due to this property.
+   widely used but are needed for a particular use case.
 
-  <p>
+  <p>Authors should generally use <a href="#propdef-font-variant"
+   title="font-variant!!property">‘<code
+   class=property>font-variant</code>’</a> and its related subproperties
+   whenever possible and only use this property for special cases where its
+   use is the only way of accessing a particular infrequently used font
+   feature.
 
   <pre>/* enable small caps and use second swash alternate */
 font-feature-settings: "smcp", "swsh" 2;</pre>
 
+  <p>A value of <dfn id=font-feature-settings-normal-value
+   title="normal!!font-feature-settings">‘<code
+   class=property>normal</code>’</dfn> means that no change in glyph
+   selection or positioning occurs due to this property.
+
   <p>Feature tag values have the following syntax:
 
   <pre
@@ -5185,10 +5167,9 @@ <h3 id=font-feature-settings-prop><span class=secno>6.12 </span>Low-level
    specified in the OpenType specification, feature tags contain four ASCII
    characters. Tag strings longer or shorter than four characters, or
    containing characters outside the U+20–7E codepoint range are invalid.
-   User agents must not use a feature tag created by truncating or padding
-   the string to four characters. Feature tags need only match a feature tag
-   defined in the font, they are not limited to explicitly registered
-   OpenType features. Fonts defining custom feature tags should follow the <a
+   Feature tags need only match a feature tag defined in the font, so they
+   are not limited to explicitly registered OpenType features. Fonts defining
+   custom feature tags should follow the <a
    href="http://www.microsoft.com/typography/otspec/featuretags.htm">tag name
    rules</a> defined in the OpenType specification <a
    href="#OPENTYPE-FEATURES"
@@ -5233,13 +5214,6 @@ <h3 id=font-feature-settings-prop><span class=secno>6.12 </span>Low-level
    the exact behavior will depend upon the way the font is designed
    (specifically, which type of lookup is used to define the feature).
 
-  <p>Authors should generally use <a href="#propdef-font-variant"
-   title="font-variant!!property">‘<code
-   class=property>font-variant</code>’</a> and its related subproperties
-   whenever possible and only use this property for special cases where its
-   use is the only way of accessing a particular infrequently used font
-   feature.
-
   <p>Although specifically defined for OpenType feature tags, feature tags
    for other modern font formats that support font features may be added in
    the future. Where possible, features defined for other font formats should
@@ -5344,6 +5318,9 @@ <h3 id=font-language-override-prop><span class=secno>6.13 </span>Font
     of the language system implied by the language of the element
   </dl>
 
+  <p>Use of invalid OpenType language system tags must not generate a parse
+   error but must be ignored when doing glyph selection and placement.
+
   <div class=example>
    <p>The <a href="http://www.un.org/en/documents/udhr/index.shtml">Universal
     Declaration of Human Rights</a> has been translated into a wide variety