Change get_attr() to get_attr_val_for_layout().

The old code was used by both layout and script, but was erroneously
borrowing for the layout case (which causes parallelism
problems). script now uses only `value_ref()` or `get_attribute()`, and
layout now has its own unsafe version that dances around the borrows of
`@mut Attr`.

src/components/main/layout/wrapper.rs

@@ -385,9 +385,9 @@ impl<'le> TElement for LayoutElement<'le> {
         self.element.namespace.to_str().unwrap_or("")
     }
 
-    fn get_attr(&self, ns_url: Option<~str>, name: &str) -> Option<~str> {
+    fn get_attr(&self, ns_url: Option<~str>, name: &str) -> Option<&'static str> {
         let namespace = Namespace::from_str(ns_url);
-        self.element.get_attr(namespace, name)
+        unsafe { self.element.get_attr_val_for_layout(namespace, name) }
     }
 
     fn get_link(&self) -> Option<~str> {
@@ -397,7 +397,9 @@ impl<'le> TElement for LayoutElement<'le> {
             // selector-link
             ElementNodeTypeId(HTMLAnchorElementTypeId) |
             ElementNodeTypeId(HTMLAreaElementTypeId) |
-            ElementNodeTypeId(HTMLLinkElementTypeId) => self.get_attr(None, "href"),
+            ElementNodeTypeId(HTMLLinkElementTypeId) => {
+                self.get_attr(None, "href").map(|val| val.to_owned())
+            }
             _ => None,
         }
     }

src/components/script/dom/attr.rs

@@ -65,6 +65,10 @@ impl Attr {
         util::swap(&mut self.value, &mut value);
         value
     }
+
+    pub fn value_ref<'a>(&'a self) -> &'a str {
+        self.value.as_slice()
+    }
 }
 
 impl Attr {

src/components/script/dom/document.rs

@@ -366,7 +366,7 @@ impl Document {
 
     pub fn GetElementsByName(&self, name: DOMString) -> @mut HTMLCollection {
         self.createHTMLCollection(|elem|
-            elem.get_attr(Null, "name").is_some() && eq_slice(elem.get_attr(Null, "name").unwrap(), name))
+            elem.get_attribute(Null, "name").is_some() && eq_slice(elem.get_attribute(Null, "name").unwrap().value_ref(), name))
     }
 
     pub fn createHTMLCollection(&self, callback: |elem: &Element| -> bool) -> @mut HTMLCollection {
@@ -456,9 +456,9 @@ fn foreach_ided_elements(root: &AbstractNode, callback: |&DOMString, &AbstractNo
         }
 
         node.with_imm_element(|element| {
-            match element.get_attr(Null, "id") {
+            match element.get_attribute(Null, "id") {
                 Some(id) => {
-                    callback(&id.to_str(), &node);
+                    callback(&id.Value(), &node);
                 }
                 None => ()
             }

src/components/script/dom/element.rs

@@ -23,8 +23,10 @@ use layout_interface::{ContentBoxesResponse, ContentChangedDocumentDamage};
 use layout_interface::{MatchSelectorsDocumentDamage};
 use style;
 
-use std::str::eq;
 use std::ascii::StrAsciiExt;
+use std::cast;
+use std::str::eq;
+use std::unstable::raw::Box;
 
 pub struct Element {
     node: Node,
@@ -155,9 +157,19 @@ impl Element {
         }).map(|&x| x)
     }
 
-    // FIXME(pcwalton): This is kind of confusingly named relative to the above...
+    pub unsafe fn get_attr_val_for_layout(&self, namespace: Namespace, name: &str) 
-    pub fn get_attr(&self, namespace: Namespace, name: &str) -> Option<~str> {
+                                          -> Option<&'static str> {
-        self.get_attribute(namespace, name).map(|attr| attr.value.clone())
+        // FIXME: only case-insensitive in the HTML namespace (as opposed to SVG, etc.)
+        let name = name.to_ascii_lower();
+        self.attrs.iter().find(|attr: & &@mut Attr| {
+            // unsafely avoid a borrow because this is accessed by many tasks
+            // during parallel layout
+            let attr: ***Box<Attr> = cast::transmute(attr);
+            name == (***attr).data.local_name && (***attr).data.namespace == namespace
+       }).map(|attr| {
+            let attr: **Box<Attr> = cast::transmute(attr);
+            cast::transmute((**attr).data.value.as_slice())
+        })
     }
 
     pub fn set_attr(&mut self, abstract_self: AbstractNode, name: DOMString, value: DOMString)
@@ -352,8 +364,8 @@ impl Element {
     }
 
     pub fn get_string_attribute(&self, name: &str) -> DOMString {
-        match self.get_attr(Null, name) {
+        match self.get_attribute(Null, name) {
-            Some(x) => x,
+            Some(x) => x.Value(),
             None => ~""
         }
     }
@@ -390,7 +402,7 @@ impl Element {
     }
 
     pub fn GetAttribute(&self, name: DOMString) -> Option<DOMString> {
-        self.get_attr(Null, name).map(|s| s.to_owned())
+        self.get_attribute(Null, name).map(|s| s.Value())
     }
 
     pub fn GetAttributeNS(&self, namespace: Option<DOMString>, local_name: DOMString) -> Option<DOMString> {

src/components/script/dom/htmldocument.rs

@@ -11,7 +11,6 @@ use dom::window::Window;
 
 use js::jsapi::JSTracer;
 use std::str::eq_slice;
-use style::TElement;
 
 pub struct HTMLDocument {
     parent: Document
@@ -46,7 +45,7 @@ impl HTMLDocument {
     pub fn Links(&self) -> @mut HTMLCollection {
         self.parent.createHTMLCollection(|elem|
             (eq_slice(elem.tag_name, "a") || eq_slice(elem.tag_name, "area"))
-            && elem.get_attr(Null, "href").is_some())
+            && elem.get_attribute(Null, "href").is_some())
     }
 
     pub fn Forms(&self) -> @mut HTMLCollection {
@@ -59,7 +58,7 @@ impl HTMLDocument {
 
     pub fn Anchors(&self) -> @mut HTMLCollection {
         self.parent.createHTMLCollection(|elem|
-            eq_slice(elem.tag_name, "a") && elem.get_attr(Null, "name").is_some())
+            eq_slice(elem.tag_name, "a") && elem.get_attribute(Null, "name").is_some())
     }
 
     pub fn Applets(&self) -> @mut HTMLCollection {

src/components/script/dom/htmlimageelement.rs

@@ -15,7 +15,6 @@ use layout_interface::{ContentBoxQuery, ContentBoxResponse};
 use servo_net::image_cache_task;
 use servo_net::image_cache_task::ImageCacheTask;
 use servo_util::url::make_url;
-use style::TElement;
 
 pub struct HTMLImageElement {
     htmlelement: HTMLElement,
@@ -41,7 +40,7 @@ impl HTMLImageElement {
     /// prefetching the image. This method must be called after `src` is changed.
     pub fn update_image(&mut self, image_cache: ImageCacheTask, url: Option<Url>) {
         let elem = &mut self.htmlelement.element;
-        let src_opt = elem.get_attr(Null, "src").map(|x| x.to_str());
+        let src_opt = elem.get_attribute(Null, "src").map(|x| x.Value());
         match src_opt {
             None => {}
             Some(src) => {

src/components/script/html/hubbub_html_parser.rs

@@ -28,7 +28,7 @@ use std::comm::{Port, SharedChan};
 use std::from_str::FromStr;
 use std::str::eq_slice;
 use std::str;
-use style::{Stylesheet, TElement};
+use style::Stylesheet;
 
 macro_rules! handle_element(
     ($document: expr,
@@ -339,11 +339,11 @@ pub fn parse_html(cx: *JSContext,
                 // Handle CSS style sheets from <link> elements
                 ElementNodeTypeId(HTMLLinkElementTypeId) => {
                     node.with_imm_element(|element| {
-                        match (element.get_attr(Null, "rel"), element.get_attr(Null, "href")) {
+                        match (element.get_attribute(Null, "rel"), element.get_attribute(Null, "href")) {
                             (Some(rel), Some(href)) => {
-                                if "stylesheet" == rel {
+                                if "stylesheet" == rel.value_ref() {
-                                    debug!("found CSS stylesheet: {:s}", href);
+                                    debug!("found CSS stylesheet: {:s}", href.value_ref());
-                                    let url = make_url(href.to_str(), Some(url2.clone()));
+                                    let url = make_url(href.Value(), Some(url2.clone()));
                                     css_chan2.send(CSSTaskNewFile(UrlProvenance(url)));
                                 }
                             }
@@ -357,7 +357,7 @@ pub fn parse_html(cx: *JSContext,
                     node.with_mut_iframe_element(|iframe_element| {
                         let sandboxed = iframe_element.is_sandboxed();
                         let elem = &mut iframe_element.htmlelement.element;
-                        let src_opt = elem.get_attr(Null, "src").map(|x| x.to_str());
+                        let src_opt = elem.get_attribute(Null, "src").map(|x| x.Value());
                         for src in src_opt.iter() {
                             let iframe_url = make_url(src.clone(), Some(url2.clone()));
                             iframe_element.frame = Some(iframe_url.clone());
@@ -453,10 +453,10 @@ pub fn parse_html(cx: *JSContext,
             unsafe {
                 let scriptnode: AbstractNode = NodeWrapping::from_hubbub_node(script);
                 scriptnode.with_imm_element(|script| {
-                    match script.get_attr(Null, "src") {
+                    match script.get_attribute(Null, "src") {
                         Some(src) => {
-                            debug!("found script: {:s}", src);
+                            debug!("found script: {:s}", src.Value());
-                            let new_url = make_url(src.to_str(), Some(url3.clone()));
+                            let new_url = make_url(src.Value(), Some(url3.clone()));
                             js_chan2.send(JSTaskNewFile(new_url));
                         }
                         None => {

src/components/script/script_task.rs

@@ -786,8 +786,8 @@ impl ScriptTask {
                 let mut anchors = doc_node.traverse_preorder().filter(|node| node.is_anchor_element());
                 anchors.find(|node| {
                     node.with_imm_element(|elem| {
-                        match elem.get_attr(Null, "name") {
+                        match elem.get_attribute(Null, "name") {
-                            Some(name) => eq_slice(name, fragid),
+                            Some(name) => eq_slice(name.value_ref(), fragid),
                             None => false
                         }
                     })
@@ -885,15 +885,15 @@ impl ScriptTask {
 
     fn load_url_from_element(&self, page: @mut Page, element: &Element) {
         // if the node's element is "a," load url from href attr
-        let attr = element.get_attr(Null, "href");
+        let attr = element.get_attribute(Null, "href");
         for href in attr.iter() {
-            debug!("ScriptTask: clicked on link to {:s}", *href);
+            debug!("ScriptTask: clicked on link to {:s}", href.Value());
-            let click_frag = href.starts_with("#");
+            let click_frag = href.value_ref().starts_with("#");
             let current_url = page.url.as_ref().map(|&(ref url, _)| {
                 url.clone()
             });
             debug!("ScriptTask: current url is {:?}", current_url);
-            let url = make_url(href.to_owned(), current_url);
+            let url = make_url(href.Value(), current_url);
 
             if click_frag {
                 match self.find_fragment_node(page, url.fragment.unwrap()) {

src/components/style/node.rs

@@ -18,7 +18,7 @@ pub trait TNode<E:TElement> : Clone {
 }
 
 pub trait TElement {
-    fn get_attr(&self, namespace: Option<~str>, attr: &str) -> Option<~str>;
+    fn get_attr(&self, namespace: Option<~str>, attr: &str) -> Option<&'static str>;
     fn get_link(&self) -> Option<~str>;
     fn get_local_name<'a>(&'a self) -> &'a str;
     fn get_namespace_url<'a>(&'a self) -> &'a str;