Clarifications to text-combine-horizontal; pull out technical details outside definition list; allow UA to not combine things that involve element boundaries

Author: fantasai

css3-writing-modes/Overview.html

@@ -2799,7 +2799,8 @@ <h2 id=text-combine><span class=secno>9. </span> Glyph Composition: the
    space of a single character. For text layout purposes, e.g. bidi ordering,
    line-breaking, emphasis marks, text-decoration, etc. the resulting
    composition is treated as a single glyph representing the Object
-   Replacement Character U+FFFC. Values have the following meanings:
+   Replacement Character U+FFFC. This property only has an effect in vertical
+   writing modes. Values have the following meanings:
 
   <dl>
    <dt><dfn id=none title="text-combine-horizontal:none">none</dfn>
@@ -2811,24 +2812,7 @@ <h2 id=text-combine><span class=secno>9. </span> Glyph Composition: the
    <dd>
     <p>In vertical writing mode, attempt to display the text contents of the
      element horizontally within the vertical line box, ideally within the
-     space of one ideographic character (1em square).
-
-    <p>The combined glyphs are stacked horizontally (similar to the contents
-     of an inline-box with a horizontal writing mode and a line-height of
-     1em) and the baseline of the resulting composition chosen such that it
-     is centered between the content edges of its parent inline box. The
-     effective height of the composition is assumed to be 1em square;
-     anything outside the square is not measured for layout purposes.
-
-    <p>Any CSS fullwidth transformations (&lsquo;<code
-     class=css>text-transform: full-width</code>&rsquo; <a href="#CSS3TEXT"
-     rel=biblioentry>[CSS3TEXT]<!--{{CSS3TEXT}}--></a> or &lsquo;<code
-     class=css>font-variant-east-asian-width: full-width</code>&rsquo; <a
-     href="#CSS3FONT" rel=biblioentry>[CSS3FONT]<!--{{CSS3FONT}}--></a>) are
-     turned off when the element contains more than one character.
-
-    <p>In horizontal mode, this value is equivalent to &lsquo;<code
-     class=css>none</code>&rsquo;.
+     space of one ideographic character (1em square). See below.
 
    <dt><dfn id=digits title="text-combine-horizontal:digits">digits</dfn>
 
@@ -2867,15 +2851,36 @@ <h2 id=text-combine><span class=secno>9. </span> Glyph Composition: the
     proportional glyphs, a three-digit number may use 1/3-em glyphs (if
     available, else halfwidth glyphs), etc. If such glyphs are not available,
     the UA must compress the composition horizontally until they fit within
-    the 1em square.
+    1em width.
 
    <dt><dfn id=scale title="text-combine-horizontal:scale">scale</dfn>
-    Compress the composition horizontally until it fits within 1em square.
+    Compress the composition horizontally until it fits within 1em width.
   </dl>
 
   <p class=issue>Do we need a tolerance value for scaling? (e.g. 1.1 instead
    of 1em)
 
+  <p>When combining text as for &lsquo;<code
+   class=css>text-combine-horizontal: all</code>&rsquo;, the glyphs of the
+   combined text are stacked horizontally, similar to the contents of an
+   inline-box with a horizontal writing mode and a line-height of 1em. The
+   effective size of the composition is assumed to be 1em square; anything
+   outside the square is not measured for layout purposes. The UA should
+   center the glyphs horizontally and vertically within the measured 1em
+   square. The baseline of the resulting composition chosen such that the
+   square is centered between the content edges of its parent inline box. Any
+   CSS fullwidth transformations (&lsquo;<code class=css>text-transform:
+   full-width</code>&rsquo; <a href="#CSS3TEXT"
+   rel=biblioentry>[CSS3TEXT]<!--{{CSS3TEXT}}--></a> or &lsquo;<code
+   class=css>font-variant-east-asian-width: full-width</code>&rsquo; <a
+   href="#CSS3FONT" rel=biblioentry>[CSS3FONT]<!--{{CSS3FONT}}--></a>) are
+   turned off when the element contains more than one character.
+
+  <p>UAs are not required to combine content that contains any element
+   boundaries: in such cases, the UA may treat such contents as for
+   &lsquo;<code class=css>text-combine-horizontal: none</code>&rsquo;.
+   Authors should beware that such contents may not be combined.
+
   <div class=example>
    <p>In East Asian documents, the &lsquo;<a
     href="#text-combine-horizontal"><code

css3-writing-modes/Overview.src.html

@@ -2093,28 +2093,16 @@ <h2 id="text-combine">
     space of a single character. For text layout purposes, e.g. bidi
     ordering, line-breaking, emphasis marks, text-decoration, etc. the
     resulting composition is treated as a single glyph representing the
-    Object Replacement Character U+FFFC. Values have the following
-    meanings:</p>
+    Object Replacement Character U+FFFC. This property only has an effect
+    in vertical writing modes. Values have the following meanings:</p>
 
   <dl>
     <dt><dfn title="text-combine-horizontal:none">none</dfn>
     <dd>No special processing.</dd>
     <dt><dfn title="text-combine-horizontal:all">all</dfn>
     <dd><p>In vertical writing mode, attempt to display the text contents
       of the element horizontally within the vertical line box, ideally
-      within the space of one ideographic character (1em square).
-    <p>The combined glyphs are stacked
-      horizontally (similar to the contents of an inline-box with a
-      horizontal writing mode and a line-height of 1em) and the baseline
-      of the resulting composition chosen such that it is centered between
-      the content edges of its parent inline box. The effective height of
-      the composition is assumed to be 1em square; anything outside the
-      square is not measured for layout purposes.
-    <p>Any CSS fullwidth transformations
-      (''text-transform: full-width'' [[CSS3TEXT]] or
-      ''font-variant-east-asian-width: full-width'' [[CSS3FONT]])
-      are turned off when the element contains more than one character.
-    <p>In horizontal mode, this value is equivalent to ''none''.
+      within the space of one ideographic character (1em square). See below.
     <dt><dfn title="text-combine-horizontal:digits">digits</dfn>
     <dd>Within the element, each sequence of consecutive horizontal digits
       that has as many or fewer characters than the integer given (or 2,
@@ -2142,13 +2130,32 @@ <h2 id="text-combine">
       halfwidth or proportional glyphs, a three-digit number may use 1/3-em glyphs
       (if available, else halfwidth glyphs), etc.
       If such glyphs are not available, the UA must compress the composition
-      horizontally until they fit within the 1em square.
+      horizontally until they fit within 1em width.
     <dt><dfn title="text-combine-horizontal:scale">scale</dfn>
-      Compress the composition horizontally until it fits within 1em square.
+      Compress the composition horizontally until it fits within 1em width.
   </dl>
 
   <p class="issue">Do we need a tolerance value for scaling? (e.g. 1.1 instead of 1em)
 
+  <p>When combining text as for ''text-combine-horizontal: all'', the
+    glyphs of the combined text are stacked horizontally, similar to
+    the contents of an inline-box with a horizontal writing mode and
+    a line-height of 1em. The effective size of the composition is
+    assumed to be 1em square; anything outside the square is not
+    measured for layout purposes. The UA should center the glyphs
+    horizontally and vertically within the measured 1em square.
+    The baseline of the resulting composition chosen such that the
+    square is centered between the content edges of its parent inline
+    box. Any CSS fullwidth transformations
+    (''text-transform: full-width'' [[CSS3TEXT]] or
+    ''font-variant-east-asian-width: full-width'' [[CSS3FONT]])
+    are turned off when the element contains more than one character.
+
+  <p>UAs are not required to combine content that contains any
+    element boundaries: in such cases, the UA may treat such contents
+    as for 'text-combine-horizontal: none'. Authors should beware that
+    such contents may not be combined.
+
   <div class="example">
     <p>In East Asian documents, the ''text-combine-horizontal'' effect is often
       used to display Latin-based strings such as components of a date or