Auto merge of #6798 - dzbarsky:gCS, r=pcwalton

Implement getComputedStyle

It's not quite done but can probably be reviewed anyway.
I still need to finish up a few of the ToCss impls, I just got lazy and wanted to make sure things worked.

The computation of the used values is definitely not right, I'm going to investigate that.

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components/script/dom/bindings/trace.rs

@@ -63,6 +63,7 @@ use msg::constellation_msg::ConstellationChan;
 use net_traits::image::base::Image;
 use profile_traits::mem::ProfilerChan;
 use util::str::{LengthOrPercentageOrAuto};
+use selectors::parser::PseudoElement;
 use serde::{Deserialize, Serialize};
 use std::cell::{Cell, UnsafeCell, RefCell};
 use std::collections::{HashMap, HashSet};
@@ -304,6 +305,7 @@ no_jsmanaged_fields!(LineCapStyle, LineJoinStyle, CompositionOrBlending);
 no_jsmanaged_fields!(RepetitionStyle);
 no_jsmanaged_fields!(WebGLError);
 no_jsmanaged_fields!(ProfilerChan);
+no_jsmanaged_fields!(PseudoElement);
 
 impl JSTraceable for Box<ScriptChan+Send> {
     #[inline]

components/script/dom/cssstyledeclaration.rs

@@ -11,9 +11,10 @@ use dom::bindings::utils::{Reflector, reflect_dom_object};
 use dom::document::DocumentHelpers;
 use dom::element::{ElementHelpers, StylePriority};
 use dom::htmlelement::HTMLElement;
-use dom::node::{window_from_node, document_from_node, NodeDamage};
+use dom::node::{window_from_node, document_from_node, NodeDamage, NodeHelpers};
 use dom::window::{Window, WindowHelpers};
 use util::str::DOMString;
+use selectors::parser::PseudoElement;
 use string_cache::Atom;
 use style::properties::{is_supported_property, longhands_from_shorthand, parse_style_attribute};
 use style::properties::PropertyDeclaration;
@@ -27,6 +28,7 @@ pub struct CSSStyleDeclaration {
     reflector_: Reflector,
     owner: JS<HTMLElement>,
     readonly: bool,
+    pseudo: Option<PseudoElement>,
 }
 
 #[derive(PartialEq)]
@@ -56,17 +58,20 @@ fn serialize_list(list: &Vec<PropertyDeclaration>) -> DOMString {
 
 impl CSSStyleDeclaration {
     pub fn new_inherited(owner: &HTMLElement,
+                         pseudo: Option<PseudoElement>,
                          modification_access: CSSModificationAccess) -> CSSStyleDeclaration {
         CSSStyleDeclaration {
             reflector_: Reflector::new(),
             owner: JS::from_ref(owner),
+            pseudo: pseudo,
             readonly: modification_access == CSSModificationAccess::Readonly,
         }
     }
 
     pub fn new(global: &Window, owner: &HTMLElement,
+               pseudo: Option<PseudoElement>,
                modification_access: CSSModificationAccess) -> Root<CSSStyleDeclaration> {
-        reflect_dom_object(box CSSStyleDeclaration::new_inherited(owner, modification_access),
+        reflect_dom_object(box CSSStyleDeclaration::new_inherited(owner, pseudo, modification_access),
                            GlobalRef::Window(global),
                            CSSStyleDeclarationBinding::Wrap)
     }
@@ -75,6 +80,7 @@ impl CSSStyleDeclaration {
 trait PrivateCSSStyleDeclarationHelpers {
     fn get_declaration(self, property: &Atom) -> Option<PropertyDeclaration>;
     fn get_important_declaration(self, property: &Atom) -> Option<PropertyDeclaration>;
+    fn get_computed_style(self, property: &Atom) -> Option<DOMString>;
 }
 
 impl<'a> PrivateCSSStyleDeclarationHelpers for &'a CSSStyleDeclaration {
@@ -89,6 +95,13 @@ impl<'a> PrivateCSSStyleDeclarationHelpers for &'a CSSStyleDeclaration {
         let element = ElementCast::from_ref(owner.r());
         element.get_important_inline_style_declaration(property).map(|decl| decl.clone())
     }
+
+    fn get_computed_style(self, property: &Atom) -> Option<DOMString> {
+        let owner = self.owner.root();
+        let node = NodeCast::from_ref(owner.r());
+        let addr = node.to_trusted_node_address();
+        window_from_node(owner.r()).resolved_style_query(addr, self.pseudo.clone(), property)
+    }
 }
 
 impl<'a> CSSStyleDeclarationMethods for &'a CSSStyleDeclaration {
@@ -129,6 +142,11 @@ impl<'a> CSSStyleDeclarationMethods for &'a CSSStyleDeclaration {
         // Step 1
         let property = Atom::from_slice(&property.to_ascii_lowercase());
 
+        if self.readonly {
+            // Readonly style declarations are used for getComputedStyle.
+            return self.get_computed_style(&property).unwrap_or("".to_owned());
+        }
+
         // Step 2
         let longhand_properties = longhands_from_shorthand(&property);
         if let Some(longhand_properties) = longhand_properties {

components/script/dom/htmlelement.rs

@@ -135,7 +135,7 @@ impl<'a> HTMLElementMethods for &'a HTMLElement {
     fn Style(self) -> Root<CSSStyleDeclaration> {
         self.style_decl.or_init(|| {
             let global = window_from_node(self);
-            CSSStyleDeclaration::new(global.r(), self, CSSModificationAccess::ReadWrite)
+            CSSStyleDeclaration::new(global.r(), self, None, CSSModificationAccess::ReadWrite)
         })
     }
 

components/script/dom/webidls/Window.webidl

@@ -90,6 +90,13 @@ partial interface Window {
   /*[Replaceable]*/ readonly attribute Performance performance;
 };
 
+// https://drafts.csswg.org/cssom/#extensions-to-the-window-interface
+partial interface Window {
+   //CSSStyleDeclaration getComputedStyle(Element elt, optional DOMString? pseudoElt);
+   [NewObject]
+   CSSStyleDeclaration getComputedStyle(HTMLElement elt, optional DOMString pseudoElt);
+};
+
 // http://dev.w3.org/csswg/cssom-view/#extensions-to-the-window-interface
 partial interface Window {
   //MediaQueryList matchMedia(DOMString query);

components/script/dom/window.rs

@@ -20,9 +20,11 @@ use dom::bindings::utils::{GlobalStaticData, Reflectable, WindowProxyHandler};
 use dom::browsercontext::BrowsingContext;
 use dom::console::Console;
 use dom::crypto::Crypto;
+use dom::cssstyledeclaration::{CSSModificationAccess, CSSStyleDeclaration};
 use dom::document::{Document, DocumentHelpers};
 use dom::element::Element;
 use dom::eventtarget::{EventTarget, EventTargetHelpers, EventTargetTypeId};
+use dom::htmlelement::HTMLElement;
 use dom::location::Location;
 use dom::navigator::Navigator;
 use dom::node::{window_from_node, TrustedNodeAddress, NodeHelpers};
@@ -30,7 +32,7 @@ use dom::performance::Performance;
 use dom::screen::Screen;
 use dom::storage::Storage;
 use layout_interface::{ReflowGoal, ReflowQueryType, LayoutRPC, LayoutChan, Reflow, Msg};
-use layout_interface::{ContentBoxResponse, ContentBoxesResponse, ScriptReflow};
+use layout_interface::{ContentBoxResponse, ContentBoxesResponse, ResolvedStyleResponse, ScriptReflow};
 use page::Page;
 use script_task::{TimerSource, ScriptChan, ScriptPort, NonWorkerScriptChan};
 use script_task::ScriptMsg;
@@ -47,6 +49,7 @@ use net_traits::ResourceTask;
 use net_traits::image_cache_task::{ImageCacheChan, ImageCacheTask};
 use net_traits::storage_task::{StorageTask, StorageType};
 use profile_traits::mem;
+use string_cache::Atom;
 use util::geometry::{self, Au, MAX_RECT};
 use util::{breakpoint, opts};
 use util::str::{DOMString,HTML_SPACE_CHARACTERS};
@@ -58,10 +61,12 @@ use js::jsapi::{JSContext, HandleValue};
 use js::jsapi::{JS_GC, JS_GetRuntime, JSAutoCompartment, JSAutoRequest};
 use js::rust::Runtime;
 use js::rust::CompileOptionsWrapper;
+use selectors::parser::PseudoElement;
 use url::{Url, UrlParser};
 
 use libc;
 use rustc_serialize::base64::{FromBase64, ToBase64, STANDARD};
+use std::ascii::AsciiExt;
 use std::borrow::ToOwned;
 use std::cell::{Cell, Ref, RefMut, RefCell};
 use std::collections::HashSet;
@@ -539,6 +544,23 @@ impl<'a> WindowMethods for &'a Window {
             chan.send(Err(WebDriverJSError::Timeout)).unwrap();
         }
     }
+
+    // https://drafts.csswg.org/cssom/#dom-window-getcomputedstyle
+    fn GetComputedStyle(self,
+                        element: &HTMLElement,
+                        pseudo: Option<DOMString>) -> Root<CSSStyleDeclaration> {
+        // Steps 1-4.
+        let pseudo = match pseudo.map(|s| s.to_ascii_lowercase()) {
+            Some(ref pseudo) if pseudo == ":before" || pseudo == "::before" =>
+                Some(PseudoElement::Before),
+            Some(ref pseudo) if pseudo == ":after" || pseudo == "::after" =>
+                Some(PseudoElement::After),
+            _ => None
+        };
+
+        // Step 5.
+        CSSStyleDeclaration::new(self, element, pseudo, CSSModificationAccess::Readonly)
+    }
 }
 
 pub trait WindowHelpers {
@@ -553,6 +575,8 @@ pub trait WindowHelpers {
     fn content_box_query(self, content_box_request: TrustedNodeAddress) -> Rect<Au>;
     fn content_boxes_query(self, content_boxes_request: TrustedNodeAddress) -> Vec<Rect<Au>>;
     fn client_rect_query(self, node_geometry_request: TrustedNodeAddress) -> Rect<i32>;
+    fn resolved_style_query(self, element: TrustedNodeAddress,
+                            pseudo: Option<PseudoElement>, property: &Atom) -> Option<String>;
     fn handle_reflow_complete_msg(self, reflow_id: u32);
     fn set_fragment_name(self, fragment: Option<String>);
     fn steal_fragment_name(self) -> Option<String>;
@@ -791,6 +815,17 @@ impl<'a> WindowHelpers for &'a Window {
         self.layout_rpc.node_geometry().client_rect
     }
 
+    fn resolved_style_query(self,
+                            element: TrustedNodeAddress,
+                            pseudo: Option<PseudoElement>,
+                            property: &Atom) -> Option<String> {
+        self.reflow(ReflowGoal::ForScriptQuery,
+                    ReflowQueryType::ResolvedStyleQuery(element, pseudo, property.clone()),
+                    ReflowReason::Query);
+        let ResolvedStyleResponse(resolved) = self.layout_rpc.resolved_style();
+        resolved
+    }
+
     fn handle_reflow_complete_msg(self, reflow_id: u32) {
         let last_reflow_id = self.last_reflow_id.get();
         if last_reflow_id == reflow_id {
@@ -1098,6 +1133,7 @@ fn debug_reflow_events(goal: &ReflowGoal, query_type: &ReflowQueryType, reason:
         ReflowQueryType::ContentBoxQuery(_n) => "\tContentBoxQuery",
         ReflowQueryType::ContentBoxesQuery(_n) => "\tContentBoxesQuery",
         ReflowQueryType::NodeGeometryQuery(_n) => "\tNodeGeometryQuery",
+        ReflowQueryType::ResolvedStyleQuery(_, _, _) => "\tResolvedStyleQuery",
     });
 
     debug_msg.push_str(match *reason {