Introduce a ToCssWithGuard trait

components/script/dom/cssconditionrule.rs

@@ -12,6 +12,7 @@ use dom::csssupportsrule::CSSSupportsRule;
 use dom_struct::dom_struct;
 use parking_lot::RwLock;
 use std::sync::Arc;
+use style::shared_lock::SharedRwLock;
 use style::stylesheets::CssRules as StyleCssRules;
 
 #[dom_struct]
@@ -27,6 +28,9 @@ impl CSSConditionRule {
         }
     }
 
+    pub fn shared_lock(&self) -> &SharedRwLock {
+        self.cssgroupingrule.shared_lock()
+    }
 }
 
 impl CSSConditionRuleMethods for CSSConditionRule {

components/script/dom/cssfontfacerule.rs

@@ -12,8 +12,8 @@ use dom::window::Window;
 use dom_struct::dom_struct;
 use parking_lot::RwLock;
 use std::sync::Arc;
+use style::shared_lock::ToCssWithGuard;
 use style::font_face::FontFaceRule;
-use style_traits::ToCss;
 
 #[dom_struct]
 pub struct CSSFontFaceRule {
@@ -47,6 +47,7 @@ impl SpecificCSSRule for CSSFontFaceRule {
     }
 
     fn get_css(&self) -> DOMString {
-        self.fontfacerule.read().to_css_string().into()
+        let guard = self.cssrule.shared_lock().read();
+        self.fontfacerule.read().to_css_string(&guard).into()
     }
 }

components/script/dom/cssgroupingrule.rs

@@ -14,6 +14,7 @@ use dom::cssstylesheet::CSSStyleSheet;
 use dom_struct::dom_struct;
 use parking_lot::RwLock;
 use std::sync::Arc;
+use style::shared_lock::SharedRwLock;
 use style::stylesheets::CssRules as StyleCssRules;
 
 #[dom_struct]
@@ -40,6 +41,10 @@ impl CSSGroupingRule {
                                                   parent_stylesheet,
                                                   RulesSource::Rules(self.rules.clone())))
     }
+
+    pub fn shared_lock(&self) -> &SharedRwLock {
+        self.cssrule.shared_lock()
+    }
 }
 
 impl CSSGroupingRuleMethods for CSSGroupingRule {

components/script/dom/cssimportrule.rs

@@ -12,8 +12,8 @@ use dom::window::Window;
 use dom_struct::dom_struct;
 use parking_lot::RwLock;
 use std::sync::Arc;
+use style::shared_lock::ToCssWithGuard;
 use style::stylesheets::ImportRule;
-use style_traits::ToCss;
 
 #[dom_struct]
 pub struct CSSImportRule {
@@ -49,6 +49,7 @@ impl SpecificCSSRule for CSSImportRule {
     }
 
     fn get_css(&self) -> DOMString {
-        self.import_rule.read().to_css_string().into()
+        let guard = self.cssrule.shared_lock().read();
+        self.import_rule.read().to_css_string(&guard).into()
     }
 }

components/script/dom/csskeyframesrule.rs

@@ -21,8 +21,8 @@ use servo_atoms::Atom;
 use std::sync::Arc;
 use style::keyframes::{Keyframe, KeyframeSelector};
 use style::parser::ParserContextExtraData;
+use style::shared_lock::ToCssWithGuard;
 use style::stylesheets::KeyframesRule;
-use style_traits::ToCss;
 
 #[dom_struct]
 pub struct CSSKeyframesRule {
@@ -134,7 +134,8 @@ impl SpecificCSSRule for CSSKeyframesRule {
     }
 
     fn get_css(&self) -> DOMString {
-        self.keyframesrule.read().to_css_string().into()
+        let guard = self.cssrule.shared_lock().read();
+        self.keyframesrule.read().to_css_string(&guard).into()
     }
 
     fn deparent_children(&self) {

components/script/dom/cssmediarule.rs

@@ -17,12 +17,13 @@ use dom_struct::dom_struct;
 use parking_lot::RwLock;
 use std::sync::Arc;
 use style::media_queries::parse_media_query_list;
+use style::shared_lock::ToCssWithGuard;
 use style::stylesheets::MediaRule;
 use style_traits::ToCss;
 
 #[dom_struct]
 pub struct CSSMediaRule {
-    cssrule: CSSConditionRule,
+    cssconditionrule: CSSConditionRule,
     #[ignore_heap_size_of = "Arc"]
     mediarule: Arc<RwLock<MediaRule>>,
     medialist: MutNullableJS<MediaList>,
@@ -33,7 +34,7 @@ impl CSSMediaRule {
                      -> CSSMediaRule {
         let list = mediarule.read().rules.clone();
         CSSMediaRule {
-            cssrule: CSSConditionRule::new_inherited(parent_stylesheet, list),
+            cssconditionrule: CSSConditionRule::new_inherited(parent_stylesheet, list),
             mediarule: mediarule,
             medialist: MutNullableJS::new(None),
         }
@@ -76,7 +77,8 @@ impl SpecificCSSRule for CSSMediaRule {
     }
 
     fn get_css(&self) -> DOMString {
-        self.mediarule.read().to_css_string().into()
+        let guard = self.cssconditionrule.shared_lock().read();
+        self.mediarule.read().to_css_string(&guard).into()
     }
 }
 

components/script/dom/cssnamespacerule.rs

@@ -13,8 +13,8 @@ use dom::window::Window;
 use dom_struct::dom_struct;
 use parking_lot::RwLock;
 use std::sync::Arc;
+use style::shared_lock::ToCssWithGuard;
 use style::stylesheets::NamespaceRule;
-use style_traits::ToCss;
 
 #[dom_struct]
 pub struct CSSNamespaceRule {
@@ -62,6 +62,7 @@ impl SpecificCSSRule for CSSNamespaceRule {
     }
 
     fn get_css(&self) -> DOMString {
-        self.namespacerule.read().to_css_string().into()
+        let guard = self.cssrule.shared_lock().read();
+        self.namespacerule.read().to_css_string(&guard).into()
     }
 }

components/script/dom/cssrule.rs

@@ -20,6 +20,7 @@ use dom::cssviewportrule::CSSViewportRule;
 use dom::window::Window;
 use dom_struct::dom_struct;
 use std::cell::Cell;
+use style::shared_lock::SharedRwLock;
 use style::stylesheets::CssRule as StyleCssRule;
 
 
@@ -103,6 +104,10 @@ impl CSSRule {
     pub fn parent_stylesheet(&self) -> &CSSStyleSheet {
         &self.parent_stylesheet
     }
+
+    pub fn shared_lock(&self) -> &SharedRwLock {
+        &self.parent_stylesheet.style_stylesheet().shared_lock
+    }
 }
 
 impl CSSRuleMethods for CSSRule {

components/script/dom/cssstylerule.rs

@@ -14,8 +14,8 @@ use dom::window::Window;
 use dom_struct::dom_struct;
 use parking_lot::RwLock;
 use std::sync::Arc;
+use style::shared_lock::ToCssWithGuard;
 use style::stylesheets::StyleRule;
-use style_traits::ToCss;
 
 #[dom_struct]
 pub struct CSSStyleRule {
@@ -51,7 +51,8 @@ impl SpecificCSSRule for CSSStyleRule {
     }
 
     fn get_css(&self) -> DOMString {
-        self.stylerule.read().to_css_string().into()
+        let guard = self.cssrule.shared_lock().read();
+        self.stylerule.read().to_css_string(&guard).into()
     }
 }
 

components/script/dom/csssupportsrule.rs

@@ -16,13 +16,14 @@ use dom_struct::dom_struct;
 use parking_lot::RwLock;
 use std::sync::Arc;
 use style::parser::ParserContext;
+use style::shared_lock::ToCssWithGuard;
 use style::stylesheets::SupportsRule;
 use style::supports::SupportsCondition;
 use style_traits::ToCss;
 
 #[dom_struct]
 pub struct CSSSupportsRule {
-    cssrule: CSSConditionRule,
+    cssconditionrule: CSSConditionRule,
     #[ignore_heap_size_of = "Arc"]
     supportsrule: Arc<RwLock<SupportsRule>>,
 }
@@ -32,7 +33,7 @@ impl CSSSupportsRule {
                      -> CSSSupportsRule {
         let list = supportsrule.read().rules.clone();
         CSSSupportsRule {
-            cssrule: CSSConditionRule::new_inherited(parent_stylesheet, list),
+            cssconditionrule: CSSConditionRule::new_inherited(parent_stylesheet, list),
             supportsrule: supportsrule,
         }
     }
@@ -75,6 +76,7 @@ impl SpecificCSSRule for CSSSupportsRule {
     }
 
     fn get_css(&self) -> DOMString {
-        self.supportsrule.read().to_css_string().into()
+        let guard = self.cssconditionrule.shared_lock().read();
+        self.supportsrule.read().to_css_string(&guard).into()
     }
 }

components/script/dom/cssviewportrule.rs

@@ -12,8 +12,8 @@ use dom::window::Window;
 use dom_struct::dom_struct;
 use parking_lot::RwLock;
 use std::sync::Arc;
+use style::shared_lock::ToCssWithGuard;
 use style::viewport::ViewportRule;
-use style_traits::ToCss;
 
 #[dom_struct]
 pub struct CSSViewportRule {
@@ -46,6 +46,7 @@ impl SpecificCSSRule for CSSViewportRule {
     }
 
     fn get_css(&self) -> DOMString {
-        self.viewportrule.read().to_css_string().into()
+        let guard = self.cssrule.shared_lock().read();
+        self.viewportrule.read().to_css_string(&guard).into()
     }
 }

components/style/font_face.rs

@@ -14,6 +14,7 @@ use computed_values::font_family::FamilyName;
 use cssparser::{AtRuleParser, DeclarationListParser, DeclarationParser, Parser};
 #[cfg(feature = "gecko")] use cssparser::UnicodeRange;
 use parser::{ParserContext, log_css_error, Parse};
+use shared_lock::{SharedRwLockReadGuard, ToCssWithGuard};
 use std::fmt;
 use std::iter;
 use style_traits::{ToCss, OneOrMoreCommaSeparated};
@@ -230,11 +231,10 @@ macro_rules! font_face_descriptors {
             }
         }
 
-        impl ToCss for FontFaceRule {
+        impl ToCssWithGuard for FontFaceRule {
             // Serialization of FontFaceRule is not specced.
-            fn to_css<W>(&self, dest: &mut W) -> fmt::Result
-                where W: fmt::Write,
-            {
+            fn to_css<W>(&self, _guard: &SharedRwLockReadGuard, dest: &mut W) -> fmt::Result
+            where W: fmt::Write {
                 dest.write_str("@font-face {\n")?;
                 $(
                     dest.write_str(concat!("  ", $m_name, ": "))?;

components/style/shared_lock.rs

@@ -160,3 +160,20 @@ mod compile_time_assert {
     impl<'a> Marker2 for SharedRwLockReadGuard<'a> {}  // Assert SharedRwLockReadGuard: !Copy
     impl<'a> Marker2 for SharedRwLockWriteGuard<'a> {}  // Assert SharedRwLockWriteGuard: !Copy
 }
+
+/// Like ToCss, but with a lock guard given by the caller.
+pub trait ToCssWithGuard {
+    /// Serialize `self` in CSS syntax, writing to `dest`, using the given lock guard.
+    fn to_css<W>(&self, guard: &SharedRwLockReadGuard, dest: &mut W) -> fmt::Result
+    where W: fmt::Write;
+
+    /// Serialize `self` in CSS syntax using the given lock guard and return a string.
+    ///
+    /// (This is a convenience wrapper for `to_css` and probably should not be overridden.)
+    #[inline]
+    fn to_css_string(&self, guard: &SharedRwLockReadGuard) -> String {
+        let mut s = String::new();
+        self.to_css(guard, &mut s).unwrap();
+        s
+    }
+}

components/style/stylesheets.rs

@@ -21,7 +21,7 @@ use selector_parser::{SelectorImpl, SelectorParser};
 use selectors::parser::SelectorList;
 use servo_config::prefs::PREFS;
 use servo_url::ServoUrl;
-use shared_lock::{SharedRwLock, Locked, SharedRwLockReadGuard};
+use shared_lock::{SharedRwLock, Locked, SharedRwLockReadGuard, ToCssWithGuard};
 use std::cell::Cell;
 use std::fmt;
 use std::sync::Arc;
@@ -372,18 +372,19 @@ impl CssRule {
     }
 }
 
-impl ToCss for CssRule {
+impl ToCssWithGuard for CssRule {
     // https://drafts.csswg.org/cssom/#serialize-a-css-rule
-    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+    fn to_css<W>(&self, guard: &SharedRwLockReadGuard, dest: &mut W) -> fmt::Result
+    where W: fmt::Write {
         match *self {
-            CssRule::Namespace(ref lock) => lock.read().to_css(dest),
-            CssRule::Import(ref lock) => lock.read().to_css(dest),
-            CssRule::Style(ref lock) => lock.read().to_css(dest),
-            CssRule::FontFace(ref lock) => lock.read().to_css(dest),
-            CssRule::Viewport(ref lock) => lock.read().to_css(dest),
-            CssRule::Keyframes(ref lock) => lock.read().to_css(dest),
-            CssRule::Media(ref lock) => lock.read().to_css(dest),
-            CssRule::Supports(ref lock) => lock.read().to_css(dest),
+            CssRule::Namespace(ref lock) => lock.read().to_css(guard, dest),
+            CssRule::Import(ref lock) => lock.read().to_css(guard, dest),
+            CssRule::Style(ref lock) => lock.read().to_css(guard, dest),
+            CssRule::FontFace(ref lock) => lock.read().to_css(guard, dest),
+            CssRule::Viewport(ref lock) => lock.read().to_css(guard, dest),
+            CssRule::Keyframes(ref lock) => lock.read().to_css(guard, dest),
+            CssRule::Media(ref lock) => lock.read().to_css(guard, dest),
+            CssRule::Supports(ref lock) => lock.read().to_css(guard, dest),
         }
     }
 }
@@ -396,9 +397,10 @@ pub struct NamespaceRule {
     pub url: Namespace,
 }
 
-impl ToCss for NamespaceRule {
+impl ToCssWithGuard for NamespaceRule {
     // https://drafts.csswg.org/cssom/#serialize-a-css-rule CSSNamespaceRule
-    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+    fn to_css<W>(&self, _guard: &SharedRwLockReadGuard, dest: &mut W) -> fmt::Result
+    where W: fmt::Write {
         try!(dest.write_str("@namespace "));
         if let Some(ref prefix) = self.prefix {
             try!(dest.write_str(&*prefix.to_string()));
@@ -426,12 +428,12 @@ pub struct ImportRule {
     pub stylesheet: Arc<Stylesheet>,
 }
 
-impl ToCss for ImportRule {
-    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+impl ToCssWithGuard for ImportRule {
+    fn to_css<W>(&self, guard: &SharedRwLockReadGuard, dest: &mut W) -> fmt::Result
+    where W: fmt::Write {
         try!(dest.write_str("@import "));
         try!(self.url.to_css(dest));
-        let guard = self.stylesheet.shared_lock.read();  // FIXME: have the caller pass this?
-        let media = self.stylesheet.media.read_with(&guard);
+        let media = self.stylesheet.media.read_with(guard);
         if !media.is_empty() {
             try!(dest.write_str(" "));
             try!(media.to_css(dest));
@@ -451,9 +453,10 @@ pub struct KeyframesRule {
     pub keyframes: Vec<Arc<RwLock<Keyframe>>>,
 }
 
-impl ToCss for KeyframesRule {
+impl ToCssWithGuard for KeyframesRule {
     // Serialization of KeyframesRule is not specced.
-    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+    fn to_css<W>(&self, _guard: &SharedRwLockReadGuard, dest: &mut W) -> fmt::Result
+    where W: fmt::Write {
         try!(dest.write_str("@keyframes "));
         try!(dest.write_str(&*self.name.to_string()));
         try!(dest.write_str(" { "));
@@ -478,16 +481,17 @@ pub struct MediaRule {
     pub rules: Arc<RwLock<CssRules>>,
 }
 
-impl ToCss for MediaRule {
+impl ToCssWithGuard for MediaRule {
     // Serialization of MediaRule is not specced.
     // https://drafts.csswg.org/cssom/#serialize-a-css-rule CSSMediaRule
-    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+    fn to_css<W>(&self, guard: &SharedRwLockReadGuard, dest: &mut W) -> fmt::Result
+    where W: fmt::Write {
         try!(dest.write_str("@media "));
         try!(self.media_queries.read().to_css(dest));
         try!(dest.write_str(" {"));
         for rule in self.rules.read().0.iter() {
             try!(dest.write_str(" "));
-            try!(rule.to_css(dest));
+            try!(rule.to_css(guard, dest));
         }
         dest.write_str(" }")
     }
@@ -505,14 +509,15 @@ pub struct SupportsRule {
     pub enabled: bool,
 }
 
-impl ToCss for SupportsRule {
-    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+impl ToCssWithGuard for SupportsRule {
+    fn to_css<W>(&self, guard: &SharedRwLockReadGuard, dest: &mut W) -> fmt::Result
+    where W: fmt::Write {
         try!(dest.write_str("@supports "));
         try!(self.condition.to_css(dest));
         try!(dest.write_str(" {"));
         for rule in self.rules.read().0.iter() {
             try!(dest.write_str(" "));
-            try!(rule.to_css(dest));
+            try!(rule.to_css(guard, dest));
         }
         dest.write_str(" }")
     }
@@ -525,9 +530,10 @@ pub struct StyleRule {
     pub block: Arc<RwLock<PropertyDeclarationBlock>>,
 }
 
-impl ToCss for StyleRule {
+impl ToCssWithGuard for StyleRule {
     // https://drafts.csswg.org/cssom/#serialize-a-css-rule CSSStyleRule
-    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+    fn to_css<W>(&self, _guard: &SharedRwLockReadGuard, dest: &mut W) -> fmt::Result
+    where W: fmt::Write {
         // Step 1
         try!(self.selectors.to_css(dest));
         // Step 2

components/style/viewport.rs

@@ -15,7 +15,7 @@ use cssparser::ToCss as ParserToCss;
 use euclid::size::TypedSize2D;
 use media_queries::Device;
 use parser::{ParserContext, log_css_error};
-use shared_lock::SharedRwLockReadGuard;
+use shared_lock::{SharedRwLockReadGuard, ToCssWithGuard};
 use std::ascii::AsciiExt;
 use std::borrow::Cow;
 use std::fmt;
@@ -505,9 +505,10 @@ impl ViewportRule {
     }
 }
 
-impl ToCss for ViewportRule {
+impl ToCssWithGuard for ViewportRule {
     // Serialization of ViewportRule is not specced.
-    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+    fn to_css<W>(&self, _guard: &SharedRwLockReadGuard, dest: &mut W) -> fmt::Result
+    where W: fmt::Write {
         try!(dest.write_str("@viewport { "));
         let mut iter = self.declarations.iter();
         try!(iter.next().unwrap().to_css(dest));

ports/geckolib/glue.rs

@@ -76,7 +76,7 @@ use style::properties::parse_one_declaration;
 use style::restyle_hints::{self, RestyleHint};
 use style::selector_parser::PseudoElementCascadeType;
 use style::sequential;
-use style::shared_lock::SharedRwLock;
+use style::shared_lock::{SharedRwLock, ToCssWithGuard};
 use style::string_cache::Atom;
 use style::stylesheets::{CssRule, CssRules, ImportRule, MediaRule, NamespaceRule};
 use style::stylesheets::{Origin, Stylesheet, StyleRule};
@@ -581,8 +581,10 @@ macro_rules! impl_basic_rule_funcs {
 
         #[no_mangle]
         pub extern "C" fn $to_css(rule: &$raw_type, result: *mut nsAString) {
+            let global_style_data = &*GLOBAL_STYLE_DATA;
+            let guard = global_style_data.shared_lock.read();
             let rule = RwLock::<$rule_type>::as_arc(&rule);
-            rule.read().to_css(unsafe { result.as_mut().unwrap() }).unwrap();
+            rule.read().to_css(&guard, unsafe { result.as_mut().unwrap() }).unwrap();
         }
     }
 }