Refactor the script task to conform to current coding style

src/components/servo/dom/bindings/clientrect.rs

@@ -12,8 +12,8 @@ use scripting::script_task::{task_from_context, global_script_context};
 pub impl ClientRect {
     pub fn init_wrapper(@mut self) {
         let script_context = global_script_context();
-        let cx = script_context.compartment.get().cx.ptr;
-        let owner = script_context.window.get();
+        let cx = script_context.js_compartment.cx.ptr;
+        let owner = script_context.root_frame.get_ref().window;
         let cache = owner.get_wrappercache();
         let scope = cache.get_wrapper();
         self.wrap_object_shared(cx, scope);
@@ -37,7 +37,7 @@ impl BindingObject for ClientRect {
     fn GetParentObject(&self, cx: *JSContext) -> @mut CacheableWrapper {
         let script_context = task_from_context(cx);
         unsafe {
-            (*script_context).window.get() as @mut CacheableWrapper
+            (*script_context).root_frame.get_ref().window as @mut CacheableWrapper
         }
     }
 }

src/components/servo/dom/bindings/clientrectlist.rs

@@ -11,8 +11,8 @@ use scripting::script_task::{task_from_context, global_script_context};
 pub impl ClientRectList {
     fn init_wrapper(@mut self) {
         let script_context = global_script_context();
-        let cx = script_context.compartment.get().cx.ptr;
-        let owner = script_context.window.get();
+        let cx = script_context.js_compartment.cx.ptr;
+        let owner = script_context.root_frame.get_ref().window;
         let cache = owner.get_wrappercache();
         let scope = cache.get_wrapper();
         self.wrap_object_shared(cx, scope);
@@ -21,7 +21,9 @@ pub impl ClientRectList {
 
 impl CacheableWrapper for ClientRectList {
     fn get_wrappercache(&mut self) -> &mut WrapperCache {
-        unsafe { cast::transmute(&self.wrapper) }
+        unsafe {
+            cast::transmute(&self.wrapper)
+        }
     }
 
     fn wrap_object_shared(@mut self, cx: *JSContext, scope: *JSObject) -> *JSObject {
@@ -33,6 +35,8 @@ impl CacheableWrapper for ClientRectList {
 impl BindingObject for ClientRectList {
     fn GetParentObject(&self, cx: *JSContext) -> @mut CacheableWrapper {
         let script_context = task_from_context(cx);
-        unsafe { (*script_context).window.get() as @mut CacheableWrapper }
+        unsafe {
+            (*script_context).root_frame.get_ref().window as @mut CacheableWrapper
+        }
     }
 }

src/components/servo/dom/bindings/codegen/CodegenRust.py

@@ -3615,7 +3615,7 @@ class CGClassConstructHook(CGAbstractExternMethod):
   //       or through unwrapping a slot or something). We'll punt and get the Window
   //       from the context for now. 
   let script_context = task_from_context(cx);
-  let global = (*script_context).window.get();
+  let global = (*script_context).root_frame.get_ref().window;
   let obj = global.get_wrappercache().get_wrapper();
 """
             preArgs = ["global"]

src/components/servo/dom/bindings/document.rs

@@ -146,6 +146,9 @@ impl CacheableWrapper for Document {
 
     fn wrap_object_shared(@mut self, cx: *JSContext, _scope: *JSObject) -> *JSObject {
         let script_context = task_from_context(cx);
-        unsafe { create((*script_context).compartment.get(), self) }
+        unsafe {
+            create((*script_context).js_compartment, self)
+        }
     }
 }
+

src/components/servo/dom/bindings/event.rs

@@ -12,8 +12,8 @@ use scripting::script_task::{task_from_context, global_script_context};
 pub impl Event_ {
     pub fn init_wrapper(@mut self) {
         let script_context = global_script_context();
-        let cx = script_context.compartment.get().cx.ptr;
-        let owner = script_context.window.get();
+        let cx = script_context.js_compartment.cx.ptr;
+        let owner = script_context.root_frame.get_ref().window;
         let cache = owner.get_wrappercache();
         let scope = cache.get_wrapper();
         self.wrap_object_shared(cx, scope);
@@ -34,7 +34,9 @@ impl CacheableWrapper for Event_ {
 impl BindingObject for Event_ {
     fn GetParentObject(&self, cx: *JSContext) -> @mut CacheableWrapper {
         let script_context = task_from_context(cx);
-        unsafe { (*script_context).window.get() as @mut CacheableWrapper }
+        unsafe {
+            (*script_context).root_frame.get_ref().window as @mut CacheableWrapper
+        }
     }
 }
 

src/components/servo/dom/bindings/eventtarget.rs

@@ -5,6 +5,7 @@
 use dom::bindings::codegen::EventTargetBinding;
 use dom::bindings::utils::{CacheableWrapper, WrapperCache, BindingObject, DerivedWrapper};
 use dom::eventtarget::EventTarget;
+
 use js::glue::bindgen::RUST_OBJECT_TO_JSVAL;
 use js::jsapi::{JSObject, JSContext, JSVal};
 use scripting::script_task::{task_from_context, global_script_context};
@@ -12,8 +13,8 @@ use scripting::script_task::{task_from_context, global_script_context};
 pub impl EventTarget {
     pub fn init_wrapper(@mut self) {
         let script_context = global_script_context();
-        let cx = script_context.compartment.get().cx.ptr;
-        let owner = script_context.window.get();
+        let cx = script_context.js_compartment.cx.ptr;
+        let owner = script_context.root_frame.get_ref().window;
         let cache = owner.get_wrappercache();
         let scope = cache.get_wrapper();
         self.wrap_object_shared(cx, scope);
@@ -34,7 +35,9 @@ impl CacheableWrapper for EventTarget {
 impl BindingObject for EventTarget {
     fn GetParentObject(&self, cx: *JSContext) -> @mut CacheableWrapper {
         let script_context = task_from_context(cx);
-        unsafe { (*script_context).window.get() as @mut CacheableWrapper }
+        unsafe {
+            (*script_context).root_frame.get_ref().window as @mut CacheableWrapper
+        }
     }
 }
 
@@ -48,7 +51,9 @@ impl DerivedWrapper for EventTarget {
         if obj.is_null() {
             return 0;
         } else {
-            unsafe { *vp = RUST_OBJECT_TO_JSVAL(obj) };
+            unsafe {
+                *vp = RUST_OBJECT_TO_JSVAL(obj)
+            };
             return 1;
         }
     }

src/components/servo/dom/bindings/htmlcollection.rs

@@ -11,8 +11,8 @@ use scripting::script_task::{task_from_context, global_script_context};
 pub impl HTMLCollection {
     fn init_wrapper(@mut self) {
         let script_context = global_script_context();
-        let cx = script_context.compartment.get().cx.ptr;
-        let owner = script_context.window.get();
+        let cx = script_context.js_compartment.cx.ptr;
+        let owner = script_context.root_frame.get_ref().window;
         let cache = owner.get_wrappercache();
         let scope = cache.get_wrapper();
         self.wrap_object_shared(cx, scope);
@@ -22,13 +22,17 @@ pub impl HTMLCollection {
 impl BindingObject for HTMLCollection {
     fn GetParentObject(&self, cx: *JSContext) -> @mut CacheableWrapper {
         let script_context = task_from_context(cx);
-        unsafe { (*script_context).window.get() as @mut CacheableWrapper }
+        unsafe {
+            (*script_context).root_frame.get_ref().window as @mut CacheableWrapper
+        }
     }
 }
 
 impl CacheableWrapper for HTMLCollection {
     fn get_wrappercache(&mut self) -> &mut WrapperCache {
-        unsafe { cast::transmute(&self.wrapper) }
+        unsafe {
+            cast::transmute(&self.wrapper)
+        }
     }
 
     fn wrap_object_shared(@mut self, cx: *JSContext, scope: *JSObject) -> *JSObject {

src/components/servo/dom/bindings/utils.rs

@@ -164,8 +164,7 @@ pub unsafe fn domstring_to_jsval(cx: *JSContext, string: &DOMString) -> JSVal {
 pub fn get_compartment(cx: *JSContext) -> @mut Compartment {
     unsafe {
         let script_context = task_from_context(cx);
-        let compartment = (*script_context).compartment.expect(~"Should always have compartment \
-                                                                 when executing JS code");
+        let compartment = (*script_context).js_compartment;
         assert!(cx == compartment.cx.ptr);
         compartment
     }

src/components/servo/dom/document.rs

@@ -25,7 +25,7 @@ pub fn Document(root: AbstractNode, window: Option<@mut Window>) -> @mut Documen
         wrapper: WrapperCache::new(),
         window: window
     };
-    let compartment = global_script_context().compartment.get();
+    let compartment = global_script_context().js_compartment;
     do root.with_base |base| {
         assert!(base.wrapper.get_wrapper().is_not_null());
         let rootable = base.wrapper.get_rootable();
@@ -38,7 +38,7 @@ pub fn Document(root: AbstractNode, window: Option<@mut Window>) -> @mut Documen
 #[unsafe_destructor]
 impl Drop for Document {
     fn finalize(&self) {
-        let compartment = global_script_context().compartment.get();
+        let compartment = global_script_context().js_compartment;
         do self.root.with_base |base| {
             assert!(base.wrapper.get_wrapper().is_not_null());
             let rootable = base.wrapper.get_rootable();

src/components/servo/dom/domparser.rs

@@ -22,7 +22,7 @@ impl DOMParser {
             wrapper: WrapperCache::new()
         };
 
-        let cx = global_script_context().compartment.get().cx.ptr;
+        let cx = global_script_context().js_compartment.cx.ptr;
         let cache = owner.get_wrappercache();
         let scope = cache.get_wrapper();
         parser.wrap_object_shared(cx, scope);

src/components/servo/dom/node.rs

@@ -391,7 +391,7 @@ impl Node {
         let mut node = AbstractNode {
             obj: transmute(node),
         };
-        let cx = global_script_context().compartment.get().cx.ptr;
+        let cx = global_script_context().js_compartment.cx.ptr;
         node::create(cx, &mut node);
         node
     }

src/components/servo/dom/window.rs

@@ -2,14 +2,15 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use scripting::script_task::{ControlMsg, ExitMsg, ScriptContext, Timer, global_script_context};
 use dom::bindings::utils::WrapperCache;
 use dom::bindings::window;
 use dom::event::Event;
-use js::jsapi::JSVal;
+use scripting::script_task::{ControlMsg, ExitMsg, FireTimerMsg, ScriptContext};
+use scripting::script_task::{global_script_context};
 use util::task::spawn_listener;
 
 use core::comm::{Port, Chan, SharedChan};
+use js::jsapi::JSVal;
 use std::timer;
 use std::uv_global_loop;
 
@@ -90,20 +91,21 @@ pub fn Window(script_chan: comm::SharedChan<ControlMsg>,
     let win = @mut Window {
         wrapper: WrapperCache::new(),
         dom_event_chan: dom_event_chan,
-        timer_chan: do spawn_listener |timer_port: Port<TimerControlMsg>| {
-            loop {
-                match timer_port.recv() {
-                    TimerMessage_Close => break,
-                    TimerMessage_Fire(td) => {
-                        script_chan.send(Timer(td));
+        timer_chan: {
+            do spawn_listener |timer_port: Port<TimerControlMsg>| {
+                loop {
+                    match timer_port.recv() {
+                        TimerMessage_Close => break,
+                        TimerMessage_Fire(td) => script_chan.send(FireTimerMsg(td)),
+                        TimerMessage_TriggerExit => script_chan.send(ExitMsg),
                     }
-                    TimerMessage_TriggerExit => script_chan.send(ExitMsg)
                 }
             }
         },
-        script_context: script_context
+        script_context: script_context,
     };
-    let compartment = global_script_context().compartment.get();
+
+    let compartment = global_script_context().js_compartment;
     window::create(compartment, win);
     win
 }

src/components/servo/engine.rs

@@ -6,7 +6,7 @@ use compositing::CompositorImpl;
 use dom::event::Event;
 use layout::layout_task::LayoutTask;
 use layout::layout_task;
-use scripting::script_task::{ExecuteMsg, ParseMsg, ScriptTask};
+use scripting::script_task::{ExecuteMsg, LoadMsg, ScriptTask};
 use scripting::script_task;
 use util::task::spawn_listener;
 
@@ -55,11 +55,11 @@ impl Engine {
             let opts = opts.take();
             let layout_task = LayoutTask(render_task.clone(), image_cache_task.clone(), opts);
 
-            let script_task = ScriptTask(layout_task.clone(),
-                                         dom_event_port.take(),
-                                         dom_event_chan.take(),
-                                         resource_task.clone(),
-                                         image_cache_task.clone());
+            let script_task = ScriptTask::new(layout_task.clone(),
+                                              dom_event_port.take(),
+                                              dom_event_chan.take(),
+                                              resource_task.clone(),
+                                              image_cache_task.clone());
 
             Engine {
                 request_port: request,
@@ -83,15 +83,15 @@ impl Engine {
         match request {
             LoadUrlMsg(url) => {
                 if url.path.ends_with(".js") {
-                    self.script_task.send(ExecuteMsg(url))
+                    self.script_task.chan.send(ExecuteMsg(url))
                 } else {
-                    self.script_task.send(ParseMsg(url))
+                    self.script_task.chan.send(LoadMsg(url))
                 }
                 return true
             }
 
             ExitMsg(sender) => {
-                self.script_task.send(script_task::ExitMsg);
+                self.script_task.chan.send(script_task::ExitMsg);
                 self.layout_task.send(layout_task::ExitMsg);
 
                 let (response_port, response_chan) = comm::stream();

src/components/servo/scripting/script_task.rs

@@ -10,167 +10,155 @@ use dom::document::Document;
 use dom::event::{Event, ResizeEvent, ReflowEvent};
 use dom::node::define_bindings;
 use dom::window::Window;
-use layout::layout_task::{AddStylesheet, BuildData, BuildMsg, Damage, LayoutTask};
-use layout::layout_task::{MatchSelectorsDamage, NoDamage, ReflowDamage};
+use layout::layout_task::{AddStylesheet, BuildData, BuildMsg, Damage, LayoutQuery};
+use layout::layout_task::{LayoutQueryResponse, LayoutTask, MatchSelectorsDamage, NoDamage};
+use layout::layout_task::{QueryMsg, ReflowDamage};
 use layout::layout_task;
 
+use core::cast::transmute;
 use core::cell::Cell;
 use core::comm::{Port, SharedChan};
-use core::either;
 use core::io::read_whole_file;
 use core::local_data;
 use core::pipes::select2i;
 use core::ptr::null;
 use core::task::{SingleThreaded, task};
 use core::util::replace;
-use dom;
+use dom::window::TimerData;
 use geom::size::Size2D;
-use html;
+use html::hubbub_html_parser;
 use js::JSVAL_NULL;
 use js::global::{global_class, debug_fns};
 use js::glue::bindgen::RUST_JSVAL_TO_OBJECT;
 use js::jsapi::JSContext;
 use js::jsapi::bindgen::{JS_CallFunctionValue, JS_GetContextPrivate};
 use js::rust::{Compartment, Cx};
-use jsrt = js::rust::rt;
+use js;
 use servo_net::image_cache_task::ImageCacheTask;
 use servo_net::resource_task::ResourceTask;
 use servo_util::tree::TreeNodeRef;
 use std::net::url::Url;
-use url_to_str = std::net::url::to_str;
+use std::net::url;
 
+/// Messages used to control the script task at a high level.
 pub enum ControlMsg {
-    ParseMsg(Url),
+    /// Loads a new URL.
+    LoadMsg(Url),
+    /// Executes a standalone script.
     ExecuteMsg(Url),
-    Timer(~dom::window::TimerData),
-    ExitMsg
+    /// Fires a JavaScript timeout.
+    FireTimerMsg(~TimerData),
+    /// Exits the engine.
+    ExitMsg,
 }
 
-pub enum PingMsg {
-    PongMsg
+/// Encapsulates external communication with the script task.
+pub struct ScriptTask {
+    /// The channel used to send control messages to the script task.
+    chan: SharedChan<ControlMsg>,
 }
 
-pub type ScriptTask = SharedChan<ControlMsg>;
+impl ScriptTask {
+    /// Creates a new script task.
+    pub fn new(layout_task: LayoutTask,
+               dom_event_port: Port<Event>,
+               dom_event_chan: SharedChan<Event>,
+               resource_task: ResourceTask,
+               image_cache_task: ImageCacheTask)
+               -> ScriptTask {
+        let (control_port, control_chan) = comm::stream();
 
-pub fn ScriptTask(layout_task: LayoutTask,
-                  dom_event_port: Port<Event>,
-                  dom_event_chan: SharedChan<Event>,
-                  resource_task: ResourceTask,
-                  img_cache_task: ImageCacheTask)
-                  -> ScriptTask {
-    let (control_port, control_chan) = comm::stream();
+        let control_chan = SharedChan::new(control_chan);
+        let control_chan_copy = control_chan.clone();
+        let control_port = Cell(control_port);
+        let dom_event_port = Cell(dom_event_port);
+        let dom_event_chan = Cell(dom_event_chan);
 
-    let control_chan = SharedChan::new(control_chan);
-    let control_chan_copy = control_chan.clone();
-    let control_port = Cell(control_port);
-    let dom_event_port = Cell(dom_event_port);
-    let dom_event_chan = Cell(dom_event_chan);
+        // FIXME: rust#6399
+        let mut the_task = task();
+        the_task.sched_mode(SingleThreaded);
+        do the_task.spawn {
+            let script_context = ScriptContext::new(layout_task.clone(),
+                                                    control_port.take(),
+                                                    control_chan_copy.clone(),
+                                                    resource_task.clone(),
+                                                    image_cache_task.clone(),
+                                                    dom_event_port.take(),
+                                                    dom_event_chan.take());
+            script_context.start();
+        }
 
-    // FIXME: rust#6399
-    let mut the_task = task();
-    the_task.sched_mode(SingleThreaded);
-    do the_task.spawn {
-        let script_context = ScriptContext(layout_task.clone(),
-                                    control_port.take(),
-                                    control_chan_copy.clone(),
-                                    resource_task.clone(),
-                                    img_cache_task.clone(),
-                                    dom_event_port.take(),
-                                    dom_event_chan.take());
-        script_context.start();
+        ScriptTask {
+            chan: control_chan
+        }
     }
-
-    return control_chan;
 }
 
+/// Information for one frame in the browsing context.
+pub struct Frame {
+    document: @mut Document,
+    window: @mut Window,
+    url: Url,
+}
+
+/// Information for an entire page. Pages are top-level browsing contexts and can contain multiple
+/// frames.
+///
+/// FIXME: Rename to `Page`, following WebKit?
 pub struct ScriptContext {
+    /// A handle to the layout task.
     layout_task: LayoutTask,
-    layout_join_port: Option<comm::Port<()>>,
-
+    /// A handle to the image cache task.
     image_cache_task: ImageCacheTask,
-    control_port: comm::Port<ControlMsg>,
-    control_chan: comm::SharedChan<ControlMsg>,
-    event_port: comm::Port<Event>,
-    event_chan: comm::SharedChan<Event>,
-
-    jsrt: jsrt,
-    cx: @Cx,
-    dom_static: GlobalStaticData,
-
-    document: Option<@mut Document>,
-    window:   Option<@mut Window>,
-    doc_url: Option<Url>,
-    window_size: Size2D<uint>,
-
+    /// A handle to the resource task.
     resource_task: ResourceTask,
 
-    compartment: Option<@mut Compartment>,
+    /// The port that we will use to join layout. If this is `None`, then layout is not currently
+    /// running.
+    layout_join_port: Option<Port<()>>,
+    /// The port on which we receive control messages (load URL, exit, etc.)
+    control_port: Port<ControlMsg>,
+    /// A channel for us to hand out when we want some other task to be able to send us control
+    /// messages.
+    control_chan: SharedChan<ControlMsg>,
+    /// The port on which we receive DOM events.
+    event_port: Port<Event>,
+    /// A channel for us to hand out when we want some other task to be able to send us DOM
+    /// events.
+    event_chan: SharedChan<Event>,
 
-    // What parts of layout are dirty.
+    /// The JavaScript runtime.
+    js_runtime: js::rust::rt,
+    /// The JavaScript context.
+    js_context: @Cx,
+    /// The JavaScript compartment.
+    js_compartment: @mut Compartment,
+    /// Global static data related to the DOM.
+    dom_static: GlobalStaticData,
+
+    /// The outermost frame. This frame contains the document, window, and page URL.
+    root_frame: Option<Frame>,
+
+    /// The current size of the window, in pixels.
+    window_size: Size2D<uint>,
+    /// What parts of layout are dirty.
     damage: Damage,
 }
 
-pub fn ScriptContext(layout_task: LayoutTask, 
-                     control_port: comm::Port<ControlMsg>,
-                     control_chan: comm::SharedChan<ControlMsg>,
-                     resource_task: ResourceTask,
-                     img_cache_task: ImageCacheTask,
-                     event_port: comm::Port<Event>,
-                     event_chan: comm::SharedChan<Event>)
-                     -> @mut ScriptContext {
-    let jsrt = jsrt();
-    let cx = jsrt.cx();
-
-    cx.set_default_options_and_version();
-    cx.set_logging_error_reporter();
-
-    let compartment = match cx.new_compartment(global_class) {
-          Ok(c) => Some(c),
-          Err(()) => None
-    };
-
-    let script_context = @mut ScriptContext {
-        layout_task: layout_task,
-        layout_join_port: None,
-        image_cache_task: img_cache_task,
-        control_port: control_port,
-        control_chan: control_chan,
-        event_port: event_port,
-        event_chan: event_chan,
-
-        jsrt: jsrt,
-        cx: cx,
-        dom_static: GlobalStaticData(),
-
-        document: None,
-        window: None,
-        doc_url: None,
-        window_size: Size2D(800u, 600u),
-
-        resource_task: resource_task,
-        compartment: compartment,
-
-        damage: MatchSelectorsDamage,
-    };
-
-    cx.set_cx_private(ptr::to_unsafe_ptr(&*script_context) as *());
-    unsafe {
-        local_data::local_data_set(global_script_context_key, cast::transmute(script_context));
-    }
-
-    script_context
-}
-
 fn global_script_context_key(_: @ScriptContext) {}
 
+/// Returns this task's script context singleton.
 pub fn global_script_context() -> @ScriptContext {
     unsafe {
-        return local_data::local_data_get(global_script_context_key).get();
+        local_data::local_data_get(global_script_context_key).get()
     }
 }
 
-pub fn task_from_context(cx: *JSContext) -> *mut ScriptContext {
-    JS_GetContextPrivate(cx) as *mut ScriptContext
+/// Returns the script context from the JS Context.
+///
+/// FIXME: Rename to `script_context_from_js_context`.
+pub fn task_from_context(js_context: *JSContext) -> *mut ScriptContext {
+    JS_GetContextPrivate(js_context) as *mut ScriptContext
 }
 
 #[unsafe_destructor]
@@ -182,139 +170,215 @@ impl Drop for ScriptContext {
     }
 }
 
-#[allow(non_implicitly_copyable_typarams)]
-pub impl ScriptContext {
-    fn start(&mut self) {
+impl ScriptContext {
+    /// Creates a new script context.
+    pub fn new(layout_task: LayoutTask, 
+               control_port: Port<ControlMsg>,
+               control_chan: SharedChan<ControlMsg>,
+               resource_task: ResourceTask,
+               img_cache_task: ImageCacheTask,
+               event_port: Port<Event>,
+               event_chan: SharedChan<Event>)
+               -> @mut ScriptContext {
+        let js_runtime = js::rust::rt();
+        let js_context = js_runtime.cx();
+
+        js_context.set_default_options_and_version();
+        js_context.set_logging_error_reporter();
+
+        let compartment = match js_context.new_compartment(global_class) {
+              Ok(c) => c,
+              Err(()) => fail!("Failed to create a compartment"),
+        };
+
+        let script_context = @mut ScriptContext {
+            layout_task: layout_task,
+            image_cache_task: img_cache_task,
+            resource_task: resource_task,
+
+            layout_join_port: None,
+            control_port: control_port,
+            control_chan: control_chan,
+            event_port: event_port,
+            event_chan: event_chan,
+
+            js_runtime: js_runtime,
+            js_context: js_context,
+            js_compartment: compartment,
+            dom_static: GlobalStaticData(),
+
+            root_frame: None,
+
+            window_size: Size2D(800, 600),
+            damage: MatchSelectorsDamage,
+        };
+
+        let script_context_ptr: *ScriptContext = &*script_context;
+        js_context.set_cx_private(script_context_ptr as *());
+
+        unsafe {
+            local_data::local_data_set(global_script_context_key, transmute(script_context))
+        }
+
+        script_context
+    }
+
+    /// Starts the script task. After calling this method, the script task will loop receiving
+    /// messages on its port.
+    pub fn start(&mut self) {
         while self.handle_msg() {
             // Go on...
         }
     }
 
+    /// Handles an incoming control message.
     fn handle_msg(&mut self) -> bool {
         match select2i(&mut self.control_port, &mut self.event_port) {
-            either::Left(*) => {
+            Left(*) => {
                 let msg = self.control_port.recv();
                 self.handle_control_msg(msg)
             }
-            either::Right(*) => {
+            Right(*) => {
                 let ev = self.event_port.recv();
-                self.handle_event(ev)
+                self.handle_event(ev);
+                true
             }
         }
     }
 
+    /// Handles a control message from the compositor/front-end. Returns true if the task is to
+    /// continue and false otherwise.
     fn handle_control_msg(&mut self, control_msg: ControlMsg) -> bool {
         match control_msg {
-          ParseMsg(url) => {
-            debug!("script: Received url `%s` to parse", url_to_str(&url));
-
-            define_bindings(self.compartment.get());
-
-            // Note: we can parse the next document in parallel
-            // with any previous documents.
-
-            let result = html::hubbub_html_parser::parse_html(copy url,
-                                                              self.resource_task.clone(),
-                                                              self.image_cache_task.clone());
-
-            let root = result.root;
-
-              // Send stylesheets over to layout
-              // FIXME: Need these should be streamed to layout as they are parsed
-              // and do not need to stop here in the script task
-              loop {
-                  match result.style_port.recv() {
-                      Some(sheet) => {
-                          self.layout_task.send(AddStylesheet(sheet));
-                      }
-                      None => break
-                  }
-              }
-
-            let js_scripts = result.js_port.recv();
-            debug!("js_scripts: %?", js_scripts);
-
-            let window   = Window(self.control_chan.clone(),
-                                  self.event_chan.clone(),
-                                  ptr::to_mut_unsafe_ptr(&mut *self)); //FIXME store this safely
-            let document = Document(root, Some(window));
-
-            do root.with_mut_base |base| {
-                base.add_to_doc(document);
+            LoadMsg(url) => {
+                debug!("script: Received url `%s` to load", url::to_str(&url));
+                self.load(url);
+                true
             }
 
-            self.damage.add(MatchSelectorsDamage);
-            self.relayout(document, &url);
+            FireTimerMsg(timer_data) => {
+                let this_value = if timer_data.args.len() > 0 {
+                    RUST_JSVAL_TO_OBJECT(timer_data.args[0])
+                } else {
+                    self.js_compartment.global_obj.ptr
+                };
 
-            self.document = Some(document);
-            self.window   = Some(window);
-            self.doc_url = Some(url);
+                let rval = JSVAL_NULL;
+                // TODO: Support extra arguments. This requires passing a `*JSVal` array as `argv`.
+                JS_CallFunctionValue(self.js_context.ptr,
+                                     this_value,
+                                     timer_data.funval,
+                                     0,
+                                     null(),
+                                     &rval);
 
-            let compartment = self.compartment.expect(~"TODO error checking");
-            compartment.define_functions(debug_fns);
-
-            do vec::consume(js_scripts) |_i, bytes| {
-                self.cx.evaluate_script(compartment.global_obj, bytes, ~"???", 1u);
+                self.relayout();
+                true
             }
 
-            return true;
-          }
 
-          Timer(timerData) => {
-            let compartment = self.compartment.expect(~"TODO error checking");
-            let thisValue = if timerData.args.len() > 0 {
-                RUST_JSVAL_TO_OBJECT(timerData.args[0])
-            } else {
-                compartment.global_obj.ptr
-            };
-            let rval = JSVAL_NULL;
-            //TODO: support extra args. requires passing a *JSVal argv
-            JS_CallFunctionValue(self.cx.ptr, thisValue, timerData.funval,
-                                 0, null(), ptr::to_unsafe_ptr(&rval));
-            self.relayout(self.document.get(), &(copy self.doc_url).get());
-            return true;
-          }
+            ExecuteMsg(url) => {
+                debug!("script: Received url `%s` to execute", url::to_str(&url));
 
+                match read_whole_file(&Path(url.path)) {
+                    Err(msg) => println(fmt!("Error opening %s: %s", url::to_str(&url), msg)),
+                    Ok(bytes) => {
+                        self.js_compartment.define_functions(debug_fns);
+                        let _ = self.js_context.evaluate_script(self.js_compartment.global_obj,
+                                                                bytes,
+                                                                copy url.path,
+                                                                1);
+                    }
+                }
 
-          ExecuteMsg(url) => {
-            debug!("script: Received url `%s` to execute", url_to_str(&url));
-
-            match read_whole_file(&Path(url.path)) {
-              Err(msg) => {
-                println(fmt!("Error opening %s: %s", url_to_str(&url), msg));
-              }
-              Ok(bytes) => {
-                let compartment = self.compartment.expect(~"TODO error checking");
-                compartment.define_functions(debug_fns);
-                self.cx.evaluate_script(compartment.global_obj, bytes, copy url.path, 1u);
-              }
+                true
             }
-            return true;
-          }
 
-          ExitMsg => {
-            self.layout_task.send(layout_task::ExitMsg);
-            return false;
-          }
+            ExitMsg => {
+                self.layout_task.send(layout_task::ExitMsg);
+                false
+            }
         }
     }
 
-    /**
-       Sends a ping to layout and waits for the response (i.e., it has finished any
-       pending layout request messages).
-    */
+    /// The entry point to document loading. Defines bindings, sets up the window and document
+    /// objects, parses HTML and CSS, and kicks off initial layout.
+    fn load(&mut self, url: Url) {
+        // Define the script DOM bindings.
+        define_bindings(self.js_compartment);
+
+        // Parse HTML.
+        //
+        // Note: We can parse the next document in parallel with any previous documents.
+        let html_parsing_result = hubbub_html_parser::parse_html(copy url,
+                                                                 self.resource_task.clone(),
+                                                                 self.image_cache_task.clone());
+
+        let root_node = html_parsing_result.root;
+
+        // Send style sheets over to layout.
+        //
+        // FIXME: These should be streamed to layout as they're parsed. We don't need to stop here
+        // in the script task.
+        loop {
+              match html_parsing_result.style_port.recv() {
+                  Some(sheet) => self.layout_task.send(AddStylesheet(sheet)),
+                  None => break,
+              }
+        }
+
+        // Receive the JavaScript scripts.
+        let js_scripts = html_parsing_result.js_port.recv();
+        debug!("js_scripts: %?", js_scripts);
+
+        // Create the window and document objects.
+        let window = Window(self.control_chan.clone(), self.event_chan.clone(), &mut *self);
+        let document = Document(root_node, Some(window));
+
+        // Tie the root into the document.
+        do root_node.with_mut_base |base| {
+            base.add_to_doc(document)
+        }
+
+        // Create the root frame.
+        self.root_frame = Some(Frame {
+            document: document,
+            window: window,
+            url: url
+        });
+
+        // Perform the initial reflow.
+        self.damage.add(MatchSelectorsDamage);
+        self.relayout();
+
+        // Define debug functions.
+        self.js_compartment.define_functions(debug_fns);
+
+        // Evaluate every script in the document.
+        do vec::consume(js_scripts) |_, bytes| {
+            let _ = self.js_context.evaluate_script(self.js_compartment.global_obj,
+                                                    bytes,
+                                                    ~"???",
+                                                    1);
+        }
+    }
+
+    /// Sends a ping to layout and waits for the response. The response will arrive when the
+    /// layout task has finished any pending request messages.
     fn join_layout(&mut self) {
         if self.layout_join_port.is_some() {
             let join_port = replace(&mut self.layout_join_port, None);
             match join_port {
                 Some(ref join_port) => {
                     if !join_port.peek() {
-                        warn!("script: waiting on layout");
+                        info!("script: waiting on layout");
                     }
+
                     join_port.recv();
-                    debug!("script: layout joined");
+
+                    debug!("script: layout joined")
                 }
-                None => fail!(~"reader forked but no join port?")
+                None => fail!(~"reader forked but no join port?"),
             }
         }
     }
@@ -322,7 +386,9 @@ pub impl ScriptContext {
     /// This method will wait until the layout task has completed its current action, join the
     /// layout task, and then request a new layout run. It won't wait for the new layout
     /// computation to finish.
-    fn relayout(&mut self, document: &Document, doc_url: &Url) {
+    ///
+    /// This function fails if there is no root frame.
+    fn relayout(&mut self) {
         debug!("script: performing relayout");
 
         // Now, join the layout so that they will see the latest changes we have made.
@@ -332,67 +398,64 @@ pub impl ScriptContext {
         let (join_port, join_chan) = comm::stream();
         self.layout_join_port = Some(join_port);
 
-        // Send new document and relevant styles to layout.
-        let data = ~BuildData {
-            node: document.root,
-            url: copy *doc_url,
-            dom_event_chan: self.event_chan.clone(),
-            window_size: self.window_size,
-            script_join_chan: join_chan,
-            damage: replace(&mut self.damage, NoDamage),
-        };
+        match self.root_frame {
+            None => fail!(~"Tried to relayout with no root frame!"),
+            Some(ref root_frame) => {
+                // Send new document and relevant styles to layout.
+                let data = ~BuildData {
+                    node: root_frame.document.root,
+                    url: copy root_frame.url,
+                    dom_event_chan: self.event_chan.clone(),
+                    window_size: self.window_size,
+                    script_join_chan: join_chan,
+                    damage: replace(&mut self.damage, NoDamage),
+                };
 
-        self.layout_task.send(BuildMsg(data));
+                self.layout_task.send(BuildMsg(data))
+            }
+        }
 
-        debug!("script: layout forked");
+        debug!("script: layout forked")
     }
 
-     fn query_layout(&mut self, query: layout_task::LayoutQuery)
-                     -> layout_task::LayoutQueryResponse {
-         //self.relayout(self.document.get(), &(copy self.doc_url).get());
+    /// Sends the given query to layout.
+    pub fn query_layout(&mut self, query: LayoutQuery) -> LayoutQueryResponse {
+         //self.relayout();
          self.join_layout();
 
          let (response_port, response_chan) = comm::stream();
-         self.layout_task.send(layout_task::QueryMsg(query, response_chan));
-         return response_port.recv()
+         self.layout_task.send(QueryMsg(query, response_chan));
+         response_port.recv()
     }
 
-    /**
-       This is the main entry point for receiving and dispatching DOM events.
-    */
-    // TODO: actually perform DOM event dispatch.
-    fn handle_event(&mut self, event: Event) -> bool {
+    /// This is the main entry point for receiving and dispatching DOM events.
+    ///
+    /// TODO: Actually perform DOM event dispatch.
+    fn handle_event(&mut self, event: Event) {
         match event {
-          ResizeEvent(new_width, new_height, response_chan) => {
-            debug!("script got resize event: %u, %u", new_width, new_height);
-            self.damage.add(ReflowDamage);
-            self.window_size = Size2D(new_width, new_height);
-            match copy self.document {
-                None => {
-                    // Nothing to do.
+            ResizeEvent(new_width, new_height, response_chan) => {
+                debug!("script got resize event: %u, %u", new_width, new_height);
+
+                self.damage.add(ReflowDamage);
+                self.window_size = Size2D(new_width, new_height);
+
+                if self.root_frame.is_some() {
+                    self.relayout()
                 }
-                Some(document) => {
-                    assert!(self.doc_url.is_some());
-                    self.relayout(document, &(copy self.doc_url).get());
+
+                response_chan.send(())
+            }
+
+            ReflowEvent => {
+                debug!("script got reflow event");
+
+                self.damage.add(MatchSelectorsDamage);
+
+                if self.root_frame.is_some() {
+                    self.relayout()
                 }
             }
-            response_chan.send(());
-            return true;
-          }
-          ReflowEvent => {
-            debug!("script got reflow event");
-            self.damage.add(MatchSelectorsDamage);
-            match /*bad*/ copy self.document {
-                None => {
-                    // Nothing to do.
-                }
-                Some(document) => {
-                    assert!(self.doc_url.is_some());
-                    self.relayout(document, &(copy self.doc_url).get());
-                }
-            }
-            return true;
-          }
         }
     }
 }
+