[css-writing-modes] backout 424d647e6366adf07a29785f8020be2ced6aab03 as this text is linked from css-text <http://lists.w3.org/Archives/Public/www-style/2013Nov/0188.html>

Author: kojiishi

css-text/issues-lc-2013.txt

@@ -148,7 +148,7 @@ Response: http://lists.w3.org/Archives/Public/www-style/2013Nov/0188.html
 Closed:   OutOfScope
 ----
 Issue 17.
-Summary:  comments from DPub IG (Fwd) #2
+Summary:  comments from DPub IG (Fwd) #2 Unicode properties for grapheme clusters
 From:     Bert Bos
 Comment:  http://lists.w3.org/Archives/Public/www-style/2013Nov/0116.html
 Response: http://lists.w3.org/Archives/Public/www-style/2013Nov/0188.html

css-writing-modes/Overview.bs

@@ -2578,6 +2578,21 @@ Characters and Properties</h2>
     Tibetan tsek and shad marks are kept with the preceding letters,
     rather than treated as an independent cluster.
 
+  <p>Unicode defines properties for characters, but for 'text-orientation',
+    it is necessary to determine the properties of a grapheme cluster.
+    For the purposes of CSS Writing Modes, the properties of a grapheme
+    cluster are given by its base character—except in two cases:
+  <ul>
+    <li>Grapheme clusters formed with an Enclosing Mark (Me) of the Common
+    script are considered to be Other Symbols (So) in the Common script.
+    They are assumed to have the same Unicode properties as the
+    Replacement Character U+FFFD.
+    <li>Grapheme clusters formed with a Space Separator (Zs) as the base
+    are considered to be Modifier Symbols (Sk). They are assumed to have
+    the same East Asian Width property as the base, but take their other
+    properties from the first combining character in the sequence.
+  </ul>
+
 <h2 id="bidi-html" class=no-num>
 Appendix B: Bidi Rules for HTML 4</h2>
 

css-writing-modes/Overview.html

@@ -2510,6 +2510,21 @@ <h2 class="no-num heading settled heading" id=character-properties><span class=c
     Tibetan tsek and shad marks are kept with the preceding letters,
     rather than treated as an independent cluster.
 
+  <p>Unicode defines properties for characters, but for <a class=property data-link-type=propdesc href=#propdef-text-orientation title=text-orientation>text-orientation</a>,
+    it is necessary to determine the properties of a grapheme cluster.
+    For the purposes of CSS Writing Modes, the properties of a grapheme
+    cluster are given by its base character—except in two cases:
+  <ul>
+    <li>Grapheme clusters formed with an Enclosing Mark (Me) of the Common
+    script are considered to be Other Symbols (So) in the Common script.
+    They are assumed to have the same Unicode properties as the
+    Replacement Character U+FFFD.
+    <li>Grapheme clusters formed with a Space Separator (Zs) as the base
+    are considered to be Modifier Symbols (Sk). They are assumed to have
+    the same East Asian Width property as the base, but take their other
+    properties from the first combining character in the sequence.
+  </ul>
+
 <h2 class="no-num heading settled heading" id=bidi-html><span class=content>
 Appendix B: Bidi Rules for HTML 4</span><a class=self-link href=#bidi-html></a></h2>