[css3-syntax] Split up some parsing railroad diagrams.

Author: SimonSapin

css3-syntax/Diagrams.src.html

@@ -176,19 +176,24 @@ <h3>Parsing</h3>
     NT('Style rule'), NT('At-rule'), NT('WHITESPACE'), NT('CDO'), NT('CDC')))));
 
 add('Style rule', Diagram(
+    NT('Style rule prelude'),
+    NT('{'), NT('Declaration/at-rule list'), NT('}')));
+
+add('Style rule prelude', Diagram(
     Optional(Sequence(
         NT('Component value, except AT-KEYWORD or {} block'),
-        ZeroOrMore(NT('Component value, except {} block')))),  // selector
-    NT('{'), NT('Declaration/at-rule list'), NT('}')));
+        ZeroOrMore(NT('Component value, except {} block'))))));
 
 add('At-rule', Diagram(
-    NT('AT-KEYWORD'),
-    ZeroOrMore(NT('Component value, except SEMICOLON or {} block')),
+    NT('AT-KEYWORD'), NT('At-rule prelude'),
     Choice(0,
         Sequence(NT('{'), NT('Declaration/at-rule list'), NT('}')),
         Sequence(NT('{'), NT('Rule list'), NT('}')),
         NT('SEMICOLON'))));
 
+add('At-rule prelude', Diagram(
+    ZeroOrMore(NT('Component value, except SEMICOLON or {} block'))));
+
 add('Rule list', Diagram(
     ZeroOrMore(Choice(0, NT('Style rule'), NT('At-rule'), NT('WHITESPACE')))));
 
@@ -206,10 +211,15 @@ <h3>Parsing</h3>
 
 add('Declaration', Diagram(
     NT('IDENT'), NT('WS*'), NT('COLON'), NT('WS*'),
-    ZeroOrMore(NT('Component value, except SEMICOLON or DELIM(!)')),
-    Optional(Sequence(
-        // XXX Mention ASCII case-insensitivity?
-        NT('DELIM(!)'), NT('WS*'), NT('IDENT(important)')))));
+    NT('Declaration value'),
+    Optional(NT('!important'))));
+
+add('Declaration value', Diagram(
+    ZeroOrMore(NT('Component value, except SEMICOLON or DELIM(!)'))));
+
+add('!important', Diagram(
+    NT('DELIM(!)'), NT('WS*'),
+    NT('IDENT(ASCII case-insensitive match for "important")')));
 
 add('Component value', Diagram(Choice(0,
     NT("IDENT"),