geckolib: Add FFI function to parse a @counter-style name.

components/style/counter_style/mod.rs

@@ -22,8 +22,12 @@ use std::ops::Range;
 use style_traits::{Comma, OneOrMoreSeparated, ParseError, StyleParseErrorKind, ToCss};
 use values::CustomIdent;
 
-/// Parse the prelude of an @counter-style rule
-pub fn parse_counter_style_name<'i, 't>(input: &mut Parser<'i, 't>) -> Result<CustomIdent, ParseError<'i>> {
+/// Parse a counter style name reference.
+///
+/// This allows the reserved counter style names "decimal" and "disc".
+pub fn parse_counter_style_name<'i, 't>(
+    input: &mut Parser<'i, 't>
+) -> Result<CustomIdent, ParseError<'i>> {
     macro_rules! predefined {
         ($($name: expr,)+) => {
             {
@@ -41,7 +45,7 @@ pub fn parse_counter_style_name<'i, 't>(input: &mut Parser<'i, 't>) -> Result<Cu
                 if let Some(&lower_cased) = predefined(&ident) {
                     Ok(CustomIdent(Atom::from(lower_cased)))
                 } else {
-                    // https://github.com/w3c/csswg-drafts/issues/1295 excludes "none"
+                    // none is always an invalid <counter-style> value.
                     CustomIdent::from_ident(location, ident, &["none"])
                 }
             }
@@ -50,6 +54,20 @@ pub fn parse_counter_style_name<'i, 't>(input: &mut Parser<'i, 't>) -> Result<Cu
     include!("predefined.rs")
 }
 
+/// Parse the prelude of an @counter-style rule
+pub fn parse_counter_style_name_definition<'i, 't>(
+    input: &mut Parser<'i, 't>
+) -> Result<CustomIdent, ParseError<'i>> {
+    parse_counter_style_name(input)
+        .and_then(|ident| {
+            if ident.0 == atom!("decimal") || ident.0 == atom!("disc") {
+                Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+            } else {
+                Ok(ident)
+            }
+        })
+}
+
 /// Parse the body (inside `{}`) of an @counter-style rule
 pub fn parse_counter_style_body<'i, 't, R>(name: CustomIdent,
                                            context: &ParserContext,

components/style/stylesheets/rule_parser.rs

@@ -5,7 +5,7 @@
 //! Parsing of the stylesheet contents.
 
 use {Namespace, Prefix};
-use counter_style::{parse_counter_style_body, parse_counter_style_name};
+use counter_style::{parse_counter_style_body, parse_counter_style_name_definition};
 use cssparser::{AtRuleParser, AtRuleType, Parser, QualifiedRuleParser, RuleListParser};
 use cssparser::{CowRcStr, SourceLocation, BasicParseError, BasicParseErrorKind};
 use error_reporting::{ContextualParseError, ParseErrorReporter};
@@ -383,13 +383,7 @@ impl<'a, 'b, 'i, R: ParseErrorReporter> AtRuleParser<'i> for NestedRuleParser<'a
                     // Support for this rule is not fully implemented in Servo yet.
                     return Err(input.new_custom_error(StyleParseErrorKind::UnsupportedAtRule(name.clone())))
                 }
-                let name = parse_counter_style_name(input)?;
-                // ASCII-case-insensitive matches for "decimal" and "disc".
-                // The name is already lower-cased by `parse_counter_style_name`
-                // so we can use == here.
-                if name.0 == atom!("decimal") || name.0 == atom!("disc") {
-                    return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
-                }
+                let name = parse_counter_style_name_definition(input)?;
                 Ok(AtRuleType::WithBlock(AtRuleBlockPrelude::CounterStyle(name)))
             },
             "viewport" => {

ports/geckolib/glue.rs

@@ -18,6 +18,7 @@ use std::ptr;
 use style::applicable_declarations::ApplicableDeclarationBlock;
 use style::context::{CascadeInputs, QuirksMode, SharedStyleContext, StyleContext};
 use style::context::ThreadLocalStyleContext;
+use style::counter_style;
 use style::data::{ElementStyles, self};
 use style::dom::{ShowSubtreeData, TDocument, TElement, TNode};
 use style::driver;
@@ -4735,3 +4736,16 @@ pub unsafe extern "C" fn Servo_SourceSizeList_Evaluate(
 pub unsafe extern "C" fn Servo_SourceSizeList_Drop(list: RawServoSourceSizeListOwned) {
     let _ = list.into_box::<SourceSizeList>();
 }
+
+#[no_mangle]
+pub extern "C" fn Servo_ParseCounterStyleName(
+    value: *const nsACString,
+) -> *mut nsAtom {
+    let value = unsafe { value.as_ref().unwrap().as_str_unchecked() };
+    let mut input = ParserInput::new(&value);
+    let mut parser = Parser::new(&mut input);
+    match parser.parse_entirely(counter_style::parse_counter_style_name_definition) {
+        Ok(name) => name.0.into_addrefed(),
+        Err(_) => ptr::null_mut(),
+    }
+}