servo: Merge #14238 - Implement ToCss serialization for CSSRules (from canaltinova:cssom-tocss); r=Manishearth

<!-- Please describe your changes on the following line: -->
Implementation of ToCss serialization for CSSRules. It requires #14190 to merge first to uncomment `CssRule::Style` branch in CssRule's ToCss implementation.

r? @Manishearth

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #14195 (github issue number if applicable).

- [X] These changes do not require tests because it's serialization changes and I'm not sure there is a test for that.

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

Source-Repo: https://github.com/servo/servo
Source-Revision: 731264f20e1f19687bf0d77fb364568bd1ac034e

servo/components/script/dom/cssfontfacerule.rs

@@ -12,6 +12,7 @@ use dom::window::Window;
 use parking_lot::RwLock;
 use std::sync::Arc;
 use style::font_face::FontFaceRule;
+use style_traits::ToCss;
 
 #[dom_struct]
 pub struct CSSFontFaceRule {
@@ -44,7 +45,6 @@ impl SpecificCSSRule for CSSFontFaceRule {
     }
 
     fn get_css(&self) -> DOMString {
-        // self.fontfacerule.read().to_css_string().into()
-        "".into()
+        self.fontfacerule.read().to_css_string().into()
     }
 }

servo/components/script/dom/csskeyframesrule.rs

@@ -12,6 +12,7 @@ use dom::window::Window;
 use parking_lot::RwLock;
 use std::sync::Arc;
 use style::stylesheets::KeyframesRule;
+use style_traits::ToCss;
 
 #[dom_struct]
 pub struct CSSKeyframesRule {
@@ -44,7 +45,6 @@ impl SpecificCSSRule for CSSKeyframesRule {
     }
 
     fn get_css(&self) -> DOMString {
-        // self.keyframesrule.read().to_css_string().into()
-        "".into()
+        self.keyframesrule.read().to_css_string().into()
     }
 }

servo/components/script/dom/cssmediarule.rs

@@ -13,6 +13,7 @@ use dom::window::Window;
 use parking_lot::RwLock;
 use std::sync::Arc;
 use style::stylesheets::MediaRule;
+use style_traits::ToCss;
 
 #[dom_struct]
 pub struct CSSMediaRule {
@@ -45,7 +46,6 @@ impl SpecificCSSRule for CSSMediaRule {
     }
 
     fn get_css(&self) -> DOMString {
-        // self.mediarule.read().to_css_string().into()
-        "".into()
+        self.mediarule.read().to_css_string().into()
     }
 }

servo/components/script/dom/cssnamespacerule.rs

@@ -12,6 +12,7 @@ use dom::window::Window;
 use parking_lot::RwLock;
 use std::sync::Arc;
 use style::stylesheets::NamespaceRule;
+use style_traits::ToCss;
 
 #[dom_struct]
 pub struct CSSNamespaceRule {
@@ -44,7 +45,6 @@ impl SpecificCSSRule for CSSNamespaceRule {
     }
 
     fn get_css(&self) -> DOMString {
-        // self.namespacerule.read().to_css_string().into()
-        "".into()
+        self.namespacerule.read().to_css_string().into()
     }
 }

servo/components/script/dom/cssviewportrule.rs

@@ -12,6 +12,7 @@ use dom::window::Window;
 use parking_lot::RwLock;
 use std::sync::Arc;
 use style::viewport::ViewportRule;
+use style_traits::ToCss;
 
 #[dom_struct]
 pub struct CSSViewportRule {
@@ -44,7 +45,6 @@ impl SpecificCSSRule for CSSViewportRule {
     }
 
     fn get_css(&self) -> DOMString {
-        // self.viewportrule.read().to_css_string().into()
-        "".into()
+        self.viewportrule.read().to_css_string().into()
     }
 }

servo/components/style/font_face.rs

@@ -10,7 +10,9 @@ use computed_values::font_family::FontFamily;
 use cssparser::{AtRuleParser, DeclarationListParser, DeclarationParser, Parser};
 use parser::{ParserContext, log_css_error};
 use properties::longhands::font_family::parse_one_family;
+use std::fmt;
 use std::iter;
+use style_traits::ToCss;
 use values::specified::url::SpecifiedUrl;
 
 #[derive(Clone, Debug, PartialEq, Eq)]
@@ -20,6 +22,22 @@ pub enum Source {
     Local(FontFamily),
 }
 
+impl ToCss for Source {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        match *self {
+            Source::Url(ref url) => {
+                try!(dest.write_str("local(\""));
+                try!(url.to_css(dest));
+            },
+            Source::Local(ref family) => {
+                try!(dest.write_str("url(\""));
+                try!(family.to_css(dest));
+            },
+        }
+        dest.write_str("\")")
+    }
+}
+
 #[derive(Clone, Debug, PartialEq, Eq)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf, Deserialize, Serialize))]
 pub struct UrlSource {
@@ -27,6 +45,12 @@ pub struct UrlSource {
     pub format_hints: Vec<String>,
 }
 
+impl ToCss for UrlSource {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        dest.write_str(self.url.as_str())
+    }
+}
+
 #[derive(Debug, PartialEq, Eq)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct FontFaceRule {
@@ -34,6 +58,28 @@ pub struct FontFaceRule {
     pub sources: Vec<Source>,
 }
 
+impl ToCss for FontFaceRule {
+    // Serialization of FontFaceRule is not specced.
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        try!(dest.write_str("@font-face { font-family: "));
+        try!(self.family.to_css(dest));
+        try!(dest.write_str(";"));
+
+        if self.sources.len() > 0 {
+            try!(dest.write_str(" src: "));
+            let mut iter = self.sources.iter();
+            try!(iter.next().unwrap().to_css(dest));
+            for source in iter {
+                try!(dest.write_str(", "));
+                try!(source.to_css(dest));
+            }
+            try!(dest.write_str(";"));
+        }
+
+        dest.write_str(" }")
+    }
+}
+
 pub fn parse_font_face_block(context: &ParserContext, input: &mut Parser)
                              -> Result<FontFaceRule, ()> {
     let mut family = None;

servo/components/style/keyframes.rs

@@ -9,7 +9,9 @@ use parser::{ParserContext, log_css_error};
 use properties::{Importance, PropertyDeclaration, PropertyDeclarationBlock};
 use properties::PropertyDeclarationParseResult;
 use properties::animated_properties::TransitionProperty;
+use std::fmt;
 use std::sync::Arc;
+use style_traits::ToCss;
 
 /// A number from 1 to 100, indicating the percentage of the animation where
 /// this keyframe should run.
@@ -82,6 +84,21 @@ pub struct Keyframe {
     pub block: Arc<RwLock<PropertyDeclarationBlock>>,
 }
 
+impl ToCss for Keyframe {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        let mut iter = self.selector.percentages().iter();
+        try!(write!(dest, "{}%", iter.next().unwrap().0));
+        for percentage in iter {
+            try!(write!(dest, ", "));
+            try!(write!(dest, "{}%", percentage.0));
+        }
+        try!(dest.write_str(" { "));
+        try!(self.block.read().to_css(dest));
+        try!(dest.write_str(" }"));
+        Ok(())
+    }
+}
+
 /// A keyframes step value. This can be a synthetised keyframes animation, that
 /// is, one autogenerated from the current computed values, or a list of
 /// declarations to apply.

servo/components/style/stylesheets.rs

@@ -107,6 +107,20 @@ impl CssRule {
     }
 }
 
+impl ToCss 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 {
+        match *self {
+            CssRule::Namespace(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),
+        }
+    }
+}
+
 #[derive(Debug, PartialEq)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct NamespaceRule {
@@ -115,18 +129,62 @@ pub struct NamespaceRule {
     pub url: Namespace,
 }
 
+impl ToCss 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 {
+        try!(dest.write_str("@namespace "));
+        if let Some(ref prefix) = self.prefix {
+            try!(dest.write_str(&*prefix.to_string()));
+            try!(dest.write_str(" "));
+        }
+        try!(dest.write_str("url(\""));
+        try!(dest.write_str(&*self.url.to_string()));
+        dest.write_str("\");")
+    }
+}
+
 #[derive(Debug)]
 pub struct KeyframesRule {
     pub name: Atom,
     pub keyframes: Vec<Arc<RwLock<Keyframe>>>,
 }
 
+impl ToCss for KeyframesRule {
+    // Serialization of KeyframesRule is not specced.
+    fn to_css<W>(&self, 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(" { "));
+        let iter = self.keyframes.iter();
+        for lock in iter {
+            let keyframe = lock.read();
+            try!(keyframe.to_css(dest));
+        }
+        dest.write_str(" }")
+    }
+}
+
 #[derive(Debug)]
 pub struct MediaRule {
     pub media_queries: Arc<RwLock<MediaList>>,
     pub rules: CssRules,
 }
 
+impl ToCss 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 {
+        try!(dest.write_str("@media ("));
+        try!(self.media_queries.read().to_css(dest));
+        try!(dest.write_str(") {"));
+        for rule in self.rules.0.read().iter() {
+            try!(dest.write_str(" "));
+            try!(rule.to_css(dest));
+        }
+        dest.write_str(" }")
+    }
+}
+
 #[derive(Debug)]
 pub struct StyleRule {
     pub selectors: Vec<Selector<TheSelectorImpl>>,

servo/components/style/values/specified/url.rs

@@ -104,6 +104,13 @@ impl SpecifiedUrl {
         self.resolved.as_ref()
     }
 
+    pub fn as_str(&self) -> &str {
+        match self.resolved {
+            Some(ref url) => url.as_str(),
+            None => "",
+        }
+    }
+
     /// Little helper for Gecko's ffi.
     pub fn as_slice_components(&self) -> (*const u8, usize) {
         match self.resolved {

servo/components/style/viewport.rs

@@ -9,6 +9,7 @@
 
 use app_units::Au;
 use cssparser::{AtRuleParser, DeclarationListParser, DeclarationParser, Parser, parse_important};
+use cssparser::ToCss as ParserToCss;
 use euclid::scale_factor::ScaleFactor;
 use euclid::size::{Size2D, TypedSize2D};
 use media_queries::Device;
@@ -26,32 +27,34 @@ use values::computed::{Context, ToComputedValue};
 use values::specified::{Length, LengthOrPercentageOrAuto, ViewportPercentageLength};
 
 macro_rules! declare_viewport_descriptor {
-    ( $( $variant: ident($data: ident), )+ ) => {
-        declare_viewport_descriptor_inner!([] [ $( $variant($data), )+ ] 0);
+    ( $( $variant_name: expr => $variant: ident($data: ident), )+ ) => {
+         declare_viewport_descriptor_inner!([] [ $( $variant_name => $variant($data), )+ ] 0);
     };
 }
 
 macro_rules! declare_viewport_descriptor_inner {
     (
-        [ $( $assigned_variant: ident($assigned_data: ident) = $assigned_discriminant: expr, )* ]
+        [ $( $assigned_variant_name: expr =>
+             $assigned_variant: ident($assigned_data: ident) = $assigned_discriminant: expr, )* ]
         [
-            $next_variant: ident($next_data: ident),
-            $( $variant: ident($data: ident), )*
+            $next_variant_name: expr => $next_variant: ident($next_data: ident),
+            $( $variant_name: expr => $variant: ident($data: ident), )*
         ]
         $next_discriminant: expr
     ) => {
         declare_viewport_descriptor_inner! {
             [
-                $( $assigned_variant($assigned_data) = $assigned_discriminant, )*
-                $next_variant($next_data) = $next_discriminant,
+                $( $assigned_variant_name => $assigned_variant($assigned_data) = $assigned_discriminant, )*
+                $next_variant_name => $next_variant($next_data) = $next_discriminant,
             ]
-            [ $( $variant($data), )* ]
+            [ $( $variant_name => $variant($data), )* ]
             $next_discriminant + 1
         }
     };
 
     (
-        [ $( $assigned_variant: ident($assigned_data: ident) = $assigned_discriminant: expr, )* ]
+        [ $( $assigned_variant_name: expr =>
+             $assigned_variant: ident($assigned_data: ident) = $assigned_discriminant: expr, )* ]
         [ ]
         $number_of_variants: expr
     ) => {
@@ -74,22 +77,37 @@ macro_rules! declare_viewport_descriptor_inner {
                 }
             }
         }
+
+        impl ToCss for ViewportDescriptor {
+            fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+                match *self {
+                    $(
+                        ViewportDescriptor::$assigned_variant(val) => {
+                            try!(dest.write_str($assigned_variant_name));
+                            try!(dest.write_str(": "));
+                            try!(val.to_css(dest));
+                        },
+                    )*
+                }
+                dest.write_str(";")
+            }
+        }
     };
 }
 
 declare_viewport_descriptor! {
-    MinWidth(ViewportLength),
-    MaxWidth(ViewportLength),
+    "min-width" => MinWidth(ViewportLength),
+    "max-width" => MaxWidth(ViewportLength),
 
-    MinHeight(ViewportLength),
-    MaxHeight(ViewportLength),
+    "min-height" => MinHeight(ViewportLength),
+    "max-height" => MaxHeight(ViewportLength),
 
-    Zoom(Zoom),
-    MinZoom(Zoom),
-    MaxZoom(Zoom),
+    "zoom" => Zoom(Zoom),
+    "min-zoom" => MinZoom(Zoom),
+    "max-zoom" => MaxZoom(Zoom),
 
-    UserZoom(UserZoom),
-    Orientation(Orientation),
+    "user-zoom" => UserZoom(UserZoom),
+    "orientation" => Orientation(Orientation),
 }
 
 trait FromMeta: Sized {
@@ -210,6 +228,16 @@ impl ViewportDescriptorDeclaration {
     }
 }
 
+impl ToCss for ViewportDescriptorDeclaration {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        try!(self.descriptor.to_css(dest));
+        if self.important {
+            try!(dest.write_str(" !important"));
+        }
+        dest.write_str(";")
+    }
+}
+
 fn parse_shorthand(input: &mut Parser) -> Result<[ViewportLength; 2], ()> {
     let min = try!(ViewportLength::parse(input));
     match input.try(|input| ViewportLength::parse(input)) {
@@ -467,6 +495,20 @@ impl ViewportRule {
     }
 }
 
+impl ToCss for ViewportRule {
+    // Serialization of ViewportRule is not specced.
+    fn to_css<W>(&self, 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));
+        for declaration in iter {
+            try!(dest.write_str(" "));
+            try!(declaration.to_css(dest));
+        }
+        dest.write_str(" }")
+    }
+}
+
 /// Computes the cascade precedence as according to
 /// http://dev.w3.org/csswg/css-cascade/#cascade-origin
 fn cascade_precendence(origin: Origin, important: bool) -> u8 {