[css-text] semantically-perceived character/visually-perceived character/visually-perceived letters

--HG--
extra : rebase_source : 22709134b04bb005ec565f87b8cdba39d93297e3

Author: kojiishi

css-text/Overview.bs

@@ -140,6 +140,10 @@ Values</h3>
 <h3 id="terms">
 Terminology</h3>
 
+  <p><dfn>semantically-perceived character</dfn>
+  <p><dfn>visually-perceived character</dfn>
+  <p><dfn>visually-perceived letters</dfn>
+
   <p id="grapheme-cluster">A <dfn>grapheme cluster</dfn> is what
     a language user considers to be a character or a basic unit of the
     script. The term is described in detail in the Unicode Technical
@@ -179,10 +183,11 @@ Terminology</h3>
     for how to determine the Unicode properties of a character.
 
   <p id="letter">A <dfn>letter</dfn> for the purpose of this specification
-    is a <i>character</i> belonging to one of the Letter or Number general
+    is a <i>semantically-perceived character</i> belonging to one of the Letter or Number general
     categories in Unicode. [[!UAX44]]
 
-  <p>The rendering characteristics of a <i>character</i> divided by an
+  <p>The rendering characteristics of a <i>semantically-perceived character</i>
+    and a <i>visually-perceived character</i> divided by an
     element boundary is undefined: it may be rendered as belonging to
     either side of the boundary, or as some approximation of belonging
     to both. Authors are forewarned that dividing grapheme clusters by
@@ -1489,7 +1494,7 @@ Canonical order: N/A
           For example, the UA could use by default a justification method that is a
           simple universal compromise for all writing systems&mdash;such as
           primarily expanding <i>word separators</i>
-          along with secondarily expanding between CJK and Southeast Asian <i>letters</i>.
+          along with secondarily expanding between CJK and Southeast Asian <i>visually-perceived letters</i>.
           Then, in cases where the <i>content language</i> of the paragraph is known,
           it could choose a more language-tailored justification behavior
           e.g. following [[JLREQ]] for Japanese,
@@ -1531,7 +1536,7 @@ Canonical order: N/A
             <p class="caption">Mixed-script text with ''text-justify: inter-word''
           </div>
       <dt><dfn>distribute</dfn></dt>
-        <dd>Justification adjusts spacing between each pair of adjacent <i>characters</i>
+        <dd>Justification adjusts spacing between each pair of adjacent <i>visually-perceived characters</i>
           (effectively varying the used 'letter-spacing' on the line).
           This value is sometimes used in newspapers,
           and is one of the common justification methods in East Asian scripts such as Japanese.
@@ -1561,24 +1566,24 @@ Expanding and Compressing Text</h4>
 
   <p>A <span id="expansion-opportunity"><dfn>justification opportunity</dfn></span> is
     a point where the justification algorithm may alter spacing within the text.
-    A justification opportunity can be provided by a single <i>character</i>
+    A justification opportunity can be provided by a single <i>visually-perceived character</i>
     (such as a <i>word separator</i>),
-    or by the juxtaposition of two <i>characters</i>.
+    or by the juxtaposition of two <i>visually-perceived characters</i>.
     Space distributed by justification is <em>in addition to</em>
     the spacing defined by the 'letter-spacing' or 'word-spacing' properties.
     However, when space is distributed to a <i>word separator</i> <i>justification opportunity</i>,
     it is applied under the same rules as for 'word-spacing'.
-    Similarly, when space is distributed to an <i>justification opportunity</i> between two <i>characters</i>,
+    Similarly, when space is distributed to an <i>justification opportunity</i> between two <i>visually-perceived characters</i>,
     it is applied under the same rules as for 'letter-spacing'.
 
   <p>A justification algorithm may divide <i>justification opportunities</i> into different priority levels.
     All <i>justification opportunities</i> within a given level
     are expanded or compressed at the same priority,
-    regardless of which <i>characters</i> created that opportunity.
+    regardless of which <i>visually-perceived characters</i> created that opportunity.
     For example, if <i>justification opportunities</i> between two Han characters
-    and between two Latin <i>letters</i> are defined to be at the same level
+    and between two Latin letters are defined to be at the same level
     (as they are in the ''distribute'' justification style),
-    they are not treated differently because they originate from different <i>characters</i>.
+    they are not treated differently because they originate from different <i>visually-perceived characters</i>.
     It is not defined in this level
     whether or how other factors
     (such as font size, letter-spacing, glyph shape, position within the line, etc.)
@@ -1588,11 +1593,11 @@ Expanding and Compressing Text</h4>
 Handling Symbols and Punctuation</h4>
 
     <p>When determining <i>justification opportunities</i>,
-      a character from the Unicode Symbols (S*) and Punctuation (P*) classes
-      is generally treated the same as a <i>letter</i>:
-      in the case of ''inter-word'', as a Latin <i>letter</i>;
-      in the case of ''distribute'', as a Han <i>letter</i>;
-      and in the case of ''text-justify:auto'', as a <i>letter</i> of the dominant script.
+      a <i>visually-perceived character</i> from the Unicode Symbols (S*) and Punctuation (P*) classes
+      is generally treated the same as a <i>visually-perceived letter</i>:
+      in the case of ''inter-word'', as a Latin <i>visually-perceived letter</i>;
+      in the case of ''distribute'', as a Han <i>visually-perceived letter</i>;
+      and in the case of ''text-justify:auto'', as a <i>visually-perceived letter</i> of the dominant script.
 
     <p>However, by typographic tradition there may be additional rules 
       controlling the justification of symbols and punctuation.
@@ -1622,13 +1627,13 @@ Unexpandable Text</h4>
 <h4 id="justify-cursive">
 Cursive Scripts</h4>
 
-    <p>Justification <em>must not</em> introduce gaps between <i>letters</i>
+    <p>Justification <em>must not</em> introduce gaps between <i>visually-perceived letters</i>
       of <i>cursive scripts</i> such as Arabic.
       If it is able, the UA <em>may</em>
-      translate space distributed to <i>justification opportunities</i> within a run of such <i>letters</i>
+      translate space distributed to <i>justification opportunities</i> within a run of such <i>visually-perceived letters</i>
       into some form of cursive elongation for that run.
       It otherwise <em>must</em> assume that no <i>justification opportunity</i> exists
-      between any pair of <i>cursive script</i> <i>letters</i>.
+      between any pair of <i>visually-perceived letters</i> in <i>cursive script</i>.
 
 <h4 id="justify-algos">
 Possible Algorithms</h4>
@@ -1686,7 +1691,7 @@ Possible Algorithms</h4>
 
   <p>CSS offers control over text spacing
   via the 'word-spacing' and 'letter-spacing' properties, which specify additional space
-  around <i>word separators</i> or between <i>characters</i>, respectively.
+  around <i>word separators</i> or between <i>visually-perceived characters</i>, respectively.
   The 'word-spacing' property can now be specified in percentages,
   making it possible to, for example, double or eliminate word spacing.
 
@@ -1768,7 +1773,7 @@ Word Spacing: the 'word-spacing' property</h3>
   </div>
 
     <p><dfn id="word-separator" title="word-separator character | word separator">Word-separator characters</dfn>
-      are <i>characters</i> whose purpose and general usage is to separate words.
+      are <i>semantically-perceived characters</i> whose purpose and general usage is to separate words.
       In [UNICODE] this includes
       the space (U+0020), the no-break space (U+00A0), the Ethiopic word space (U+1361),
       the Aegean word separators (U+10100,U+10101), the Ugaritic word divider (U+1039F),
@@ -1826,13 +1831,13 @@ Word Spacing: the 'word-spacing' property</h3>
           <td>N/A
     </table>
 
-  <p>This property specifies additional spacing between adjacent <i>characters</i>
+  <p>This property specifies additional spacing between adjacent <i>visually-perceived characters</i>
   (commonly called <dfn>tracking</dfn>).
   Letter-spacing is applied after
   <a href="http://www.w3.org/TR/css3-writing-modes/#text-direction">bidi reordering</a>
   and is in addition to any 'word-spacing'.
   Depending on the justification rules in effect,
-  user agents may further increase or decrease the space between <i>characters</i>
+  user agents may further increase or decrease the space between <i>visually-perceived characters</i>
   in order to <a href="#text-justify">justify text</a>.
 
   <p>Values have the following meanings:
@@ -1841,13 +1846,13 @@ Word Spacing: the 'word-spacing' property</h3>
     <dt><dfn>normal</dfn>
       <dd>No additional spacing is applied. Computes to zero.
     <dt><dfn>&lt;length&gt;</dfn>
-      <dd>Specifies <em>additional</em> spacing between <i>characters</i>.
+      <dd>Specifies <em>additional</em> spacing between <i>visually-perceived characters</i>.
         Values may be negative, but there may be implementation-dependent limits.
   </dl>
 
     <p>For the purpose of 'letter-spacing', each consecutive run of atomic
       inlines (such as images and inline blocks) is treated as a single
-      <i>character</i>.
+      <i>visually-perceived character</i>.
 
     <p>Letter-spacing must not be applied at the beginning or at the end of a line.
 
@@ -1867,11 +1872,11 @@ Word Spacing: the 'word-spacing' property</h3>
     <p class="ls-ex bad ls-fixed-width color-box" style="text-align: right">a&emsp;b&emsp;c&emsp;</p>
   </div>
 
-    <p>Letter spacing between two <i>characters</i> effectively “belongs”
-      to the innermost element that contains the two <i>characters</i>:
-      the total letter spacing between two adjacent <i>characters</i> (after bidi reordering)
+    <p>Letter spacing between two <i>visually-perceived characters</i> effectively “belongs”
+      to the innermost element that contains the two <i>visually-perceived characters</i>:
+      the total letter spacing between two adjacent <i>visually-perceived characters</i> (after bidi reordering)
       is specified by and rendered within
-      the innermost element that <em>contains</em> the boundary between the two <i>characters</i>.
+      the innermost element that <em>contains</em> the boundary between the two <i>visually-perceived characters</i>.
 
   <div class="example">
     <p>A given value of 'letter-spacing' only affects the spacing
@@ -1944,12 +1949,12 @@ Word Spacing: the 'word-spacing' property</h3>
       as it will prevent even spacing of the text.
 
     <p>If it is able, the UA <em>may</em> apply letter-spacing to <i>cursive scripts</i>
-    by translating the total spacing distributed to a run of such <i>letters</i>
+    by translating the total spacing distributed to a run of such letters
     into some form of cursive elongation for that run.
     Otherwise, if the UA cannot expand text from a <i>cursive script</i>
     without breaking its cursive connections,
     it <em>must not</em> apply spacing
-    between any pair of that script's <i>letters</i> at all.
+    between any pair of that script's <i>visually-perceived characters</i> at all.
 
 <h2 id="edge-effects">
   Edge Effects</h2>