[css-ruby-1] Draft additional requirements for justification opportunities in ruby (in a comment). w3c#1907 w3c#771 w3c/jlreq#184

Author: fantasai

css-ruby-1/Overview.bs

@@ -1381,6 +1381,38 @@ Ruby Text Distribution: the 'ruby-align' property</h3>
 		</dd>
 	</dl>
 
+<!--
+
+	[=Justification opportunities=] are defined in [[!CSS-TEXT-3]]
+	and controlled by the 'text-justify' property.
+	For the purpose of 'ruby-align' specifically,
+	the following additional requirements apply under ''text-justify: auto'':
+
+	<ul>
+		<li>
+			Any [=typographic letter unit=] from the Han, Kana, or Hangul scripts
+			is handled the same as under ''text-justify: inter-character''.
+		<li>
+			In [=ruby annotations=] only (?),
+			any [=typographic letter unit=] from the Bopomofo script
+			is handled the same as under ''text-justify: inter-word''.
+		<li>
+			In [=ruby annotations=] only (?),
+			neither SPACE U+0020 nor NO-BREAK SPACE U+00A0
+			provide a [=justification opportunity=].
+	</ul>
+
+	<div class="example">
+		Make an example showing `text-justify: auto` vs `text-justify: inter-word` vs `text-justify: inter-character`.
+	</div>
+
+	Relevant issues:
+		https://github.com/w3c/csswg-drafts/issues/1907 bopomofo
+		https://github.com/w3c/csswg-drafts/issues/771 spaces/Latin
+		https://github.com/w3c/jlreq/issues/184
+
+-->
+
 	<div class="example">
 		Since a typical implementation will by default define [=justification opportunities=]
 		between every adjacent pair of CJK [=characters=]