Implement browsing context discarding.

5 files changed, 96 insertions, 112 deletions

diff --git a/components/script/dom/browsingcontext.rs b/components/script/dom/browsingcontext.rs
index 1a7f26253a0..9652445d96f 100644
--- a/components/script/dom/browsingcontext.rs
+++ b/components/script/dom/browsingcontext.rs
@@ -3,16 +3,13 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::conversions::{ToJSValConvertible, root_from_handleobject};
-use dom::bindings::inheritance::Castable;
-use dom::bindings::js::{JS, MutNullableJS, Root, RootedReference};
+use dom::bindings::js::{JS, Root, RootedReference};
 use dom::bindings::proxyhandler::{fill_property_descriptor, get_property_descriptor};
 use dom::bindings::reflector::{DomObject, MutDomObject, Reflector};
 use dom::bindings::trace::JSTraceable;
 use dom::bindings::utils::WindowProxyHandler;
 use dom::bindings::utils::get_array_index_from_id;
-use dom::document::Document;
 use dom::element::Element;
-use dom::globalscope::GlobalScope;
 use dom::window::Window;
 use js::JSCLASS_IS_GLOBAL;
 use js::glue::{CreateWrapperProxyHandler, ProxyTraps, NewWindowProxy};
@@ -26,7 +23,6 @@ use js::jsapi::{MutableHandle, MutableHandleObject, MutableHandleValue};
 use js::jsapi::{ObjectOpResult, PropertyDescriptor};
 use js::jsval::{UndefinedValue, PrivateValue};
 use js::rust::get_object_class;
-use msg::constellation_msg::PipelineId;
 use std::cell::Cell;
 
 #[dom_struct]
@@ -40,10 +36,8 @@ pub struct BrowsingContext {
     /// Indicates if reflow is required when reloading.
     needs_reflow: Cell<bool>,
 
-    /// The current active document.
-    /// Note that the session history is stored in the constellation,
-    /// in the script thread we just track the current active document.
-    active_document: MutNullableJS<Document>,
+    /// Has this browsing context been discarded?
+    discarded: Cell<bool>,
 
     /// The containing iframe element, if this is a same-origin iframe
     frame_element: Option<JS<Element>>,
@@ -54,7 +48,7 @@ impl BrowsingContext {
         BrowsingContext {
             reflector: Reflector::new(),
             needs_reflow: Cell::new(true),
-            active_document: Default::default(),
+            discarded:  Cell::new(false),
             frame_element: frame_element.map(JS::from_ref),
         }
     }
@@ -84,20 +78,12 @@ impl BrowsingContext {
         }
     }
 
-    pub fn set_active_document(&self, document: &Document) {
-        self.active_document.set(Some(document))
+    pub fn discard(&self) {
+        self.discarded.set(true);
     }
 
-    pub fn active_document(&self) -> Root<Document> {
-        self.active_document.get().expect("No active document.")
-    }
-
-    pub fn maybe_active_document(&self) -> Option<Root<Document>> {
-        self.active_document.get()
-    }
-
-    pub fn active_window(&self) -> Root<Window> {
-        Root::from_ref(self.active_document().window())
+    pub fn is_discarded(&self) -> bool {
+        self.discarded.get()
     }
 
     pub fn frame_element(&self) -> Option<&Element> {
@@ -115,15 +101,6 @@ impl BrowsingContext {
         self.needs_reflow.set(status);
         old
     }
-
-    pub fn active_pipeline_id(&self) -> Option<PipelineId> {
-        self.active_document.get()
-            .map(|doc| doc.window().upcast::<GlobalScope>().pipeline_id())
-    }
-
-    pub fn unset_active_document(&self) {
-        self.active_document.set(None)
-    }
 }
 
 #[allow(unsafe_code)]
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index d6d967db6c4..bfc98d61b0f 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -190,6 +190,7 @@ pub struct Document {
     last_modified: Option<String>,
     encoding: Cell<EncodingRef>,
     is_html_document: bool,
+    is_fully_active: Cell<bool>,
     url: DOMRefCell<ServoUrl>,
     quirks_mode: Cell<QuirksMode>,
     /// Caches for the getElement methods
@@ -385,20 +386,17 @@ impl Document {
         self.trigger_mozbrowser_event(MozBrowserEvent::SecurityChange(https_state));
     }
 
-    // https://html.spec.whatwg.org/multipage/#active-document
-    pub fn is_active(&self) -> bool {
-        self.browsing_context().map_or(false, |context| {
-            self == &*context.active_document()
-        })
-    }
-
     // https://html.spec.whatwg.org/multipage/#fully-active
     pub fn is_fully_active(&self) -> bool {
-        if !self.is_active() {
-            return false;
-        }
-        // FIXME: It should also check whether the browser context is top-level or not
-        true
+        self.is_fully_active.get()
+    }
+
+    pub fn fully_activate(&self) {
+        self.is_fully_active.set(true)
+    }
+
+    pub fn fully_deactivate(&self) {
+        self.is_fully_active.set(false)
     }
 
     pub fn origin(&self) -> &Origin {
@@ -1693,11 +1691,16 @@ impl Document {
         self.current_parser.get()
     }
 
-    /// Find an iframe element in the document.
-    pub fn find_iframe(&self, frame_id: FrameId) -> Option<Root<HTMLIFrameElement>> {
+    /// Iterate over all iframes in the document.
+    pub fn iter_iframes(&self) -> impl Iterator<Item=Root<HTMLIFrameElement>> {
         self.upcast::<Node>()
             .traverse_preorder()
             .filter_map(Root::downcast::<HTMLIFrameElement>)
+    }
+
+    /// Find an iframe element in the document.
+    pub fn find_iframe(&self, frame_id: FrameId) -> Option<Root<HTMLIFrameElement>> {
+        self.iter_iframes()
             .find(|node| node.frame_id() == frame_id)
     }
 
@@ -1864,6 +1867,7 @@ impl Document {
             // https://dom.spec.whatwg.org/#concept-document-encoding
             encoding: Cell::new(UTF_8),
             is_html_document: is_html_document == IsHTMLDocument::HTMLDocument,
+            is_fully_active: Cell::new(false),
             id_map: DOMRefCell::new(HashMap::new()),
             tag_map: DOMRefCell::new(HashMap::new()),
             tagns_map: DOMRefCell::new(HashMap::new()),
@@ -2261,19 +2265,12 @@ impl DocumentMethods for Document {
 
     // https://html.spec.whatwg.org/multipage/#dom-document-hasfocus
     fn HasFocus(&self) -> bool {
-        match self.browsing_context() {
-            Some(browsing_context) => {
-                // Step 2.
-                let candidate = browsing_context.active_document();
-                // Step 3.
-                if &*candidate == self {
-                    true
-                } else {
-                    false //TODO  Step 4.
-                }
-            }
-            None => false,
+        // Step 1-2.
+        if self.window().parent_info().is_none() && self.is_fully_active() {
+            return true;
         }
+        // TODO Step 3.
+        false
     }
 
     // https://html.spec.whatwg.org/multipage/#relaxing-the-same-origin-restriction
@@ -3190,8 +3187,8 @@ impl DocumentMethods for Document {
 
         // Step 2.
         // TODO: handle throw-on-dynamic-markup-insertion counter.
-
-        if !self.is_active() {
+        // FIXME: this should check for being active rather than fully active
+        if !self.is_fully_active() {
             // Step 3.
             return Ok(());
         }
diff --git a/components/script/dom/htmliframeelement.rs b/components/script/dom/htmliframeelement.rs
index 692598d5339..3a1c9daf1c9 100644
--- a/components/script/dom/htmliframeelement.rs
+++ b/components/script/dom/htmliframeelement.rs
@@ -33,7 +33,6 @@ use dom::eventtarget::EventTarget;
 use dom::globalscope::GlobalScope;
 use dom::htmlelement::HTMLElement;
 use dom::node::{Node, NodeDamage, UnbindContext, document_from_node, window_from_node};
-use dom::urlhelper::UrlHelper;
 use dom::virtualmethods::VirtualMethods;
 use dom::window::{ReflowReason, Window};
 use html5ever_atoms::LocalName;
@@ -709,42 +708,34 @@ impl VirtualMethods for HTMLIFrameElement {
         LoadBlocker::terminate(&mut blocker);
 
         // https://html.spec.whatwg.org/multipage/#a-browsing-context-is-discarded
-        if let Some(pipeline_id) = self.pipeline_id.get() {
-            debug!("Unbinding pipeline {} from frame {}.", pipeline_id, self.frame_id);
-            let window = window_from_node(self);
-
-            // The only reason we're waiting for the iframe to be totally
-            // removed is to ensure the script thread can't add iframes faster
-            // than the compositor can remove them.
-            //
-            // Since most of this cleanup doesn't happen on same-origin
-            // iframes, and since that would cause a deadlock, don't do it.
-            let same_origin = {
-                // FIXME(#10968): this should probably match the origin check in
-                //                HTMLIFrameElement::contentDocument.
-                let self_url = self.get_url();
-                let win_url = window_from_node(self).get_url();
-                UrlHelper::SameOrigin(&self_url, &win_url) || self_url.as_str() == "about:blank"
-            };
-            let (sender, receiver) = if same_origin {
-                (None, None)
-            } else {
-                let (sender, receiver) = ipc::channel().unwrap();
-                (Some(sender), Some(receiver))
-            };
-            let msg = ConstellationMsg::RemoveIFrame(pipeline_id, sender);
-            window.upcast::<GlobalScope>().constellation_chan().send(msg).unwrap();
-            if let Some(receiver) = receiver {
-                receiver.recv().unwrap()
+        debug!("Unbinding frame {}.", self.frame_id);
+        let window = window_from_node(self);
+        let (sender, receiver) = ipc::channel().unwrap();
+
+        // Ask the constellation to remove the iframe, and tell us the
+        // pipeline ids of the closed pipelines.
+        let msg = ConstellationMsg::RemoveIFrame(self.frame_id, sender);
+        window.upcast::<GlobalScope>().constellation_chan().send(msg).unwrap();
+        let exited_pipeline_ids = receiver.recv().unwrap();
+
+        // The spec for discarding is synchronous,
+        // so we need to discard the browsing contexts now, rather than
+        // when the `PipelineExit` message arrives.
+        for exited_pipeline_id in exited_pipeline_ids {
+            if let Some(exited_document) = ScriptThread::find_document(exited_pipeline_id) {
+                exited_document.window().browsing_context().discard();
+                for exited_iframe in exited_document.iter_iframes() {
+                    exited_iframe.pipeline_id.set(None);
+                }
             }
-
-            // Resetting the pipeline_id to None is required here so that
-            // if this iframe is subsequently re-added to the document
-            // the load doesn't think that it's a navigation, but instead
-            // a new iframe. Without this, the constellation gets very
-            // confused.
-            self.pipeline_id.set(None);
         }
+
+        // Resetting the pipeline_id to None is required here so that
+        // if this iframe is subsequently re-added to the document
+        // the load doesn't think that it's a navigation, but instead
+        // a new iframe. Without this, the constellation gets very
+        // confused.
+        self.pipeline_id.set(None);
     }
 }
 
diff --git a/components/script/dom/webidls/Window.webidl b/components/script/dom/webidls/Window.webidl
index dbc4b76591e..47c753f43b1 100644
--- a/components/script/dom/webidls/Window.webidl
+++ b/components/script/dom/webidls/Window.webidl
@@ -31,9 +31,13 @@
   // other browsing contexts
   [Replaceable] readonly attribute WindowProxy frames;
   //[Replaceable] readonly attribute unsigned long length;
-  [Unforgeable] readonly attribute WindowProxy top;
+  // Note that this can return null in the case that the browsing context has been discarded.
+  // https://github.com/whatwg/html/issues/2115
+  [Unforgeable] readonly attribute WindowProxy? top;
   //         attribute any opener;
-  readonly attribute WindowProxy parent;
+  // Note that this can return null in the case that the browsing context has been discarded.
+  // https://github.com/whatwg/html/issues/2115
+  readonly attribute WindowProxy? parent;
   readonly attribute Element? frameElement;
   //WindowProxy open(optional DOMString url = "about:blank", optional DOMString target = "_blank",
   //                 optional DOMString features = "", optional boolean replace = false);
diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index 37bf817ed7a..87d15ab1616 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -163,6 +163,7 @@ pub struct Window {
     #[ignore_heap_size_of = "channels are hard"]
     image_cache_chan: ImageCacheChan,
     browsing_context: MutNullableJS<BrowsingContext>,
+    document: MutNullableJS<Document>,
     history: MutNullableJS<History>,
     performance: MutNullableJS<Performance>,
     navigation_start: u64,
@@ -443,7 +444,7 @@ impl WindowMethods for Window {
 
     // https://html.spec.whatwg.org/multipage/#dom-document-2
     fn Document(&self) -> Root<Document> {
-        self.browsing_context().active_document()
+        self.document.get().expect("Document accessed before initialization.")
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-history
@@ -551,21 +552,32 @@ impl WindowMethods for Window {
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-parent
-    fn Parent(&self) -> Root<BrowsingContext> {
-        match  self.parent() {
-            Some(window) => window.browsing_context(),
-            None => self.Window()
+    fn GetParent(&self) -> Option<Root<BrowsingContext>> {
+        // Steps 1. and 2.
+        if self.browsing_context().is_discarded() {
+            return None;
         }
-    }
+        match self.parent() {
+            // Step 4.
+            Some(parent) => Some(parent.Window()),
+            // Step 5.
+            None => Some(self.Window())
+        }
+     }
 
     // https://html.spec.whatwg.org/multipage/#dom-top
-    fn Top(&self) -> Root<BrowsingContext> {
+    fn GetTop(&self) -> Option<Root<BrowsingContext>> {
+        // Steps 1. and 2.
+        if self.browsing_context().is_discarded() {
+            return None;
+        }
+        // Step 5.
         let mut window = Root::from_ref(self);
         while let Some(parent) = window.parent() {
             window = parent;
         }
-        window.browsing_context()
-    }
+        Some(window.Window())
+     }
 
     // https://dvcs.w3.org/hg/webperf/raw-file/tip/specs/
     // NavigationTiming/Overview.html#sec-window.performance-attribute
@@ -1351,6 +1363,13 @@ impl Window {
         unsafe { SetWindowProxy(cx, window, browsing_context.reflector().get_jsobject()); }
     }
 
+    #[allow(unsafe_code)]
+    pub fn init_document(&self, document: &Document) {
+        assert!(self.document.get().is_none());
+        assert!(document.window() == self);
+        self.document.set(Some(&document));
+    }
+
     /// Commence a new URL load which will either replace this window or scroll to a fragment.
     pub fn load_url(&self, url: ServoUrl, replace: bool, force_reload: bool,
                     referrer_policy: Option<ReferrerPolicy>) {
@@ -1518,13 +1537,8 @@ impl Window {
             return None;
         }
 
-        let browsing_context = self.browsing_context();
-
-        browsing_context.frame_element().map(|frame_element| {
-            let window = window_from_node(frame_element);
-            let context = window.browsing_context();
-            context.active_window()
-        })
+        self.browsing_context().frame_element()
+            .map(|frame_element| window_from_node(frame_element))
     }
 
     /// Returns whether this window is mozbrowser.
@@ -1610,6 +1624,7 @@ impl Window {
             image_cache_thread: image_cache_thread,
             history: Default::default(),
             browsing_context: Default::default(),
+            document: Default::default(),
             performance: Default::default(),
             navigation_start: (current_time.sec * 1000 + current_time.nsec as i64 / 1000000) as u64,
             navigation_start_precise: time::precise_time_ns() as f64,