Allow windows to share browsing contexts.

components/script/dom/browsingcontext.rs

@@ -5,7 +5,7 @@
 use dom::bindings::conversions::{ToJSValConvertible, root_from_handleobject};
 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::reflector::{DomObject, Reflector};
 use dom::bindings::trace::JSTraceable;
 use dom::bindings::utils::WindowProxyHandler;
 use dom::bindings::utils::get_array_index_from_id;
@@ -19,18 +19,24 @@ use js::jsapi::{JSAutoCompartment, JSContext, JSErrNum, JSFreeOp, JSObject};
 use js::jsapi::{JSPROP_READONLY, JSTracer, JS_DefinePropertyById};
 use js::jsapi::{JS_ForwardGetPropertyTo, JS_ForwardSetPropertyTo};
 use js::jsapi::{JS_GetOwnPropertyDescriptorById, JS_HasPropertyById};
+use js::jsapi::{JS_TransplantObject, SetWindowProxy};
 use js::jsapi::{MutableHandle, MutableHandleObject, MutableHandleValue};
 use js::jsapi::{ObjectOpResult, PropertyDescriptor};
 use js::jsval::{UndefinedValue, PrivateValue};
 use js::rust::get_object_class;
 use std::cell::Cell;
+use std::ptr;
 
 #[dom_struct]
 // NOTE: the browsing context for a window is managed in two places:
 // here, in script, but also in the constellation. The constellation
 // manages the session history, which in script is accessed through
 // History objects, messaging the constellation.
 pub struct BrowsingContext {
+    /// The WindowProxy object.
+    /// Unlike other reflectors, we mutate this field because
+    /// we have to brain-transplant the reflector when the WindowProxy
+    /// changes Window.
     reflector: Reflector,
 
     /// Has this browsing context been discarded?
@@ -44,7 +50,7 @@ impl BrowsingContext {
     pub fn new_inherited(frame_element: Option<&Element>) -> BrowsingContext {
         BrowsingContext {
             reflector: Reflector::new(),
-            discarded:  Cell::new(false),
+            discarded: Cell::new(false),
             frame_element: frame_element.map(JS::from_ref),
         }
     }
@@ -56,21 +62,29 @@ impl BrowsingContext {
             assert!(!handler.is_null());
 
             let cx = window.get_cx();
-            let parent = window.reflector().get_jsobject();
-            assert!(!parent.get().is_null());
-            assert!(((*get_object_class(parent.get())).flags & JSCLASS_IS_GLOBAL) != 0);
-            let _ac = JSAutoCompartment::new(cx, parent.get());
-            rooted!(in(cx) let window_proxy = NewWindowProxy(cx, parent, handler));
+            let window_jsobject = window.reflector().get_jsobject();
+            assert!(!window_jsobject.get().is_null());
+            assert!(((*get_object_class(window_jsobject.get())).flags & JSCLASS_IS_GLOBAL) != 0);
+            let _ac = JSAutoCompartment::new(cx, window_jsobject.get());
+
+            // Create a new window proxy.
+            rooted!(in(cx) let window_proxy = NewWindowProxy(cx, window_jsobject, handler));
             assert!(!window_proxy.is_null());
 
-            let object = box BrowsingContext::new_inherited(frame_element);
+            // Create a new browsing context.
+            let mut browsing_context = box BrowsingContext::new_inherited(frame_element);
 
-            let raw = Box::into_raw(object);
-            SetProxyExtra(window_proxy.get(), 0, &PrivateValue(raw as *const _));
+            // The window proxy owns the browsing context.
+            // When we finalize the window proxy, it drops the browsing context it owns.
+            SetProxyExtra(window_proxy.get(), 0, &PrivateValue(&*browsing_context as *const _ as *const _));
 
-            (*raw).init_reflector(window_proxy.get());
+            // Notify the JS engine about the new window proxy binding.
+            SetWindowProxy(cx, window_jsobject, window_proxy.handle());
 
-            Root::from_ref(&*raw)
+            // Set the reflector.
+            debug!("Initializing reflector of {:p} to {:p}.", browsing_context, window_proxy.get());
+            browsing_context.reflector.set_jsobject(window_proxy.get());
+            Root::from_ref(&*Box::into_raw(browsing_context))
         }
     }
 
@@ -86,6 +100,50 @@ impl BrowsingContext {
         self.frame_element.r()
     }
 
+    #[allow(unsafe_code)]
+    /// Change the Window that this browsing context's WindowProxy resolves to.
+    // TODO: support setting the window proxy to a dummy value,
+    // to handle the case when the active document is in another script thread.
+    pub fn set_window_proxy(&self, window: &Window) {
+        unsafe {
+            debug!("Setting window proxy of {:p}.", self);
+            let WindowProxyHandler(handler) = window.windowproxy_handler();
+            assert!(!handler.is_null());
+
+            let cx = window.get_cx();
+            let window_jsobject = window.reflector().get_jsobject();
+            let old_window_proxy = self.reflector.get_jsobject();
+            assert!(!window_jsobject.get().is_null());
+            assert!(((*get_object_class(window_jsobject.get())).flags & JSCLASS_IS_GLOBAL) != 0);
+            let _ac = JSAutoCompartment::new(cx, window_jsobject.get());
+
+            // The old window proxy no longer owns this browsing context.
+            SetProxyExtra(old_window_proxy.get(), 0, &PrivateValue(ptr::null_mut()));
+
+            // Brain transpant the window proxy.
+            // We need to do this, because the Window and WindowProxy
+            // objects need to be in the same compartment.
+            // JS_TransplantObject does this by copying the contents
+            // of the old window proxy to the new window proxy, then
+            // making the old window proxy a cross-compartment wrapper
+            // pointing to the new window proxy.
+            rooted!(in(cx) let new_window_proxy = NewWindowProxy(cx, window_jsobject, handler));
+            debug!("Transplanting window proxy from {:p} to {:p}.", old_window_proxy.get(), new_window_proxy.get());
+            rooted!(in(cx) let new_window_proxy = JS_TransplantObject(cx, old_window_proxy, new_window_proxy.handle()));
+            debug!("Transplanted window proxy is {:p}.", new_window_proxy.get());
+
+            // Transfer ownership of this browsing context from the old window proxy to the new one.
+            SetProxyExtra(new_window_proxy.get(), 0, &PrivateValue(self as *const _ as *const _));
+
+            // Notify the JS engine about the new window proxy binding.
+            SetWindowProxy(cx, window_jsobject, new_window_proxy.handle());
+
+            // Update the reflector.
+            debug!("Setting reflector of {:p} to {:p}.", self, new_window_proxy.get());
+            self.reflector.rootable().set(new_window_proxy.get());
+        }
+    }
+
     pub fn window_proxy(&self) -> *mut JSObject {
         let window_proxy = self.reflector.get_jsobject();
         assert!(!window_proxy.get().is_null());
@@ -277,16 +335,20 @@ static PROXY_HANDLER: ProxyTraps = ProxyTraps {
 #[allow(unsafe_code)]
 unsafe extern fn finalize(_fop: *mut JSFreeOp, obj: *mut JSObject) {
     let this = GetProxyExtra(obj, 0).to_private() as *mut BrowsingContext;
-    assert!(!this.is_null());
+    if this.is_null() {
+        // GC during obj creation or after transplanting.
+        return;
+    }
+    let jsobject = (*this).reflector.get_jsobject().get();
+    debug!("BrowsingContext finalize: {:p}, with reflector {:p} from {:p}.", this, jsobject, obj);
     let _ = Box::from_raw(this);
-    debug!("BrowsingContext finalize: {:p}", this);
 }
 
 #[allow(unsafe_code)]
 unsafe extern fn trace(trc: *mut JSTracer, obj: *mut JSObject) {
     let this = GetProxyExtra(obj, 0).to_private() as *const BrowsingContext;
     if this.is_null() {
-        // GC during obj creation
+        // GC during obj creation or after transplanting.
         return;
     }
     (*this).trace(trc);

components/script/dom/document.rs

@@ -184,13 +184,12 @@ impl PendingRestyle {
 pub struct Document {
     node: Node,
     window: JS<Window>,
-    /// https://html.spec.whatwg.org/multipage/#concept-document-bc
-    browsing_context: Option<JS<BrowsingContext>>,
     implementation: MutNullableJS<DOMImplementation>,
     location: MutNullableJS<Location>,
     content_type: DOMString,
     last_modified: Option<String>,
     encoding: Cell<EncodingRef>,
+    has_browsing_context: bool,
     is_html_document: bool,
     activity: Cell<DocumentActivity>,
     url: DOMRefCell<ServoUrl>,
@@ -369,8 +368,12 @@ impl Document {
 
     /// https://html.spec.whatwg.org/multipage/#concept-document-bc
     #[inline]
-    pub fn browsing_context(&self) -> Option<&BrowsingContext> {
-        self.browsing_context.as_ref().map(|browsing_context| &**browsing_context)
+    pub fn browsing_context(&self) -> Option<Root<BrowsingContext>> {
+        if self.has_browsing_context {
+            Some(self.window.browsing_context())
+        } else {
+            None
+        }
     }
 
     #[inline]
@@ -398,7 +401,7 @@ impl Document {
 
     pub fn set_activity(&self, activity: DocumentActivity) {
         // This function should only be called on documents with a browsing context
-        assert!(self.browsing_context.is_some());
+        assert!(self.has_browsing_context);
         // Set the document's activity level, reflow if necessary, and suspend or resume timers.
         if activity != self.activity.get() {
             self.activity.set(activity);
@@ -1568,7 +1571,7 @@ impl Document {
                 self.process_deferred_scripts();
             },
             LoadType::PageSource(_) => {
-                if self.browsing_context.is_some() {
+                if self.has_browsing_context {
                     // Disarm the reflow timer and trigger the initial reflow.
                     self.reflow_timeout.set(None);
                     self.upcast::<Node>().dirty(NodeDamage::OtherNodeDamage);
@@ -1830,7 +1833,7 @@ impl Document {
 
     /// https://html.spec.whatwg.org/multipage/#cookie-averse-document-object
     pub fn is_cookie_averse(&self) -> bool {
-        self.browsing_context.is_none() || !url_has_network_scheme(&self.url())
+        !self.has_browsing_context || !url_has_network_scheme(&self.url())
     }
 
     pub fn nodes_from_point(&self, client_point: &Point2D<f32>) -> Vec<UntrustedNodeAddress> {
@@ -1901,9 +1904,15 @@ fn url_has_network_scheme(url: &ServoUrl) -> bool {
     }
 }
 
+#[derive(Copy, Clone, HeapSizeOf, JSTraceable, PartialEq, Eq)]
+pub enum HasBrowsingContext {
+    No,
+    Yes,
+}
+
 impl Document {
     pub fn new_inherited(window: &Window,
-                         browsing_context: Option<&BrowsingContext>,
+                         has_browsing_context: HasBrowsingContext,
                          url: Option<ServoUrl>,
                          origin: Origin,
                          is_html_document: IsHTMLDocument,
@@ -1926,7 +1935,7 @@ impl Document {
         Document {
             node: Node::new_document_node(),
             window: JS::from_ref(window),
-            browsing_context: browsing_context.map(JS::from_ref),
+            has_browsing_context: has_browsing_context == HasBrowsingContext::Yes,
             implementation: Default::default(),
             location: Default::default(),
             content_type: match content_type {
@@ -1970,7 +1979,7 @@ impl Document {
             deferred_scripts: Default::default(),
             asap_in_order_scripts_list: Default::default(),
             asap_scripts_set: Default::default(),
-            scripting_enabled: browsing_context.is_some(),
+            scripting_enabled: has_browsing_context == HasBrowsingContext::Yes,
             animation_frame_ident: Cell::new(0),
             animation_frame_list: DOMRefCell::new(vec![]),
             running_animation_callbacks: Cell::new(false),
@@ -2007,7 +2016,7 @@ impl Document {
         let doc = window.Document();
         let docloader = DocumentLoader::new(&*doc.loader());
         Ok(Document::new(window,
-                         None,
+                         HasBrowsingContext::No,
                          None,
                          doc.origin().alias(),
                          IsHTMLDocument::NonHTMLDocument,
@@ -2021,7 +2030,7 @@ impl Document {
     }
 
     pub fn new(window: &Window,
-               browsing_context: Option<&BrowsingContext>,
+               has_browsing_context: HasBrowsingContext,
                url: Option<ServoUrl>,
                origin: Origin,
                doctype: IsHTMLDocument,
@@ -2034,7 +2043,7 @@ impl Document {
                referrer_policy: Option<ReferrerPolicy>)
                -> Root<Document> {
         let document = reflect_dom_object(box Document::new_inherited(window,
-                                                                      browsing_context,
+                                                                      has_browsing_context,
                                                                       url,
                                                                       origin,
                                                                       doctype,
@@ -2107,7 +2116,7 @@ impl Document {
                 IsHTMLDocument::NonHTMLDocument
             };
             let new_doc = Document::new(self.window(),
-                                        None,
+                                        HasBrowsingContext::No,
                                         None,
                                         // https://github.com/whatwg/html/issues/2109
                                         Origin::opaque_identifier(),
@@ -3011,10 +3020,10 @@ impl DocumentMethods for Document {
 
     // https://html.spec.whatwg.org/multipage/#dom-document-defaultview
     fn GetDefaultView(&self) -> Option<Root<Window>> {
-        if self.browsing_context.is_none() {
-            None
-        } else {
+        if self.has_browsing_context {
             Some(Root::from_ref(&*self.window))
+        } else {
+            None
         }
     }
 

components/script/dom/domimplementation.rs

@@ -13,7 +13,7 @@ use dom::bindings::js::{JS, Root};
 use dom::bindings::reflector::{Reflector, reflect_dom_object};
 use dom::bindings::str::DOMString;
 use dom::bindings::xmlname::{namespace_from_domstring, validate_qualified_name};
-use dom::document::{Document, IsHTMLDocument};
+use dom::document::{Document, HasBrowsingContext, IsHTMLDocument};
 use dom::document::DocumentSource;
 use dom::documenttype::DocumentType;
 use dom::htmlbodyelement::HTMLBodyElement;
@@ -78,7 +78,7 @@ impl DOMImplementationMethods for DOMImplementation {
 
         // Step 1.
         let doc = XMLDocument::new(win,
-                                   None,
+                                   HasBrowsingContext::No,
                                    None,
                                    self.document.origin().alias(),
                                    IsHTMLDocument::NonHTMLDocument,
@@ -125,7 +125,7 @@ impl DOMImplementationMethods for DOMImplementation {
 
         // Step 1-2.
         let doc = Document::new(win,
-                                None,
+                                HasBrowsingContext::No,
                                 None,
                                 self.document.origin().alias(),
                                 IsHTMLDocument::HTMLDocument,

components/script/dom/domparser.rs

@@ -15,7 +15,7 @@ use dom::bindings::error::Fallible;
 use dom::bindings::js::{JS, Root};
 use dom::bindings::reflector::{Reflector, reflect_dom_object};
 use dom::bindings::str::DOMString;
-use dom::document::{Document, IsHTMLDocument};
+use dom::document::{Document, HasBrowsingContext, IsHTMLDocument};
 use dom::document::DocumentSource;
 use dom::servoparser::ServoParser;
 use dom::window::Window;
@@ -60,7 +60,7 @@ impl DOMParserMethods for DOMParser {
         match ty {
             Text_html => {
                 let document = Document::new(&self.window,
-                                             None,
+                                             HasBrowsingContext::No,
                                              Some(url.clone()),
                                              doc.origin().alias(),
                                              IsHTMLDocument::HTMLDocument,
@@ -78,7 +78,7 @@ impl DOMParserMethods for DOMParser {
             Text_xml | Application_xml | Application_xhtml_xml => {
                 // FIXME: this should probably be FromParser when we actually parse the string (#3756).
                 let document = Document::new(&self.window,
-                                             None,
+                                             HasBrowsingContext::No,
                                              Some(url.clone()),
                                              doc.origin().alias(),
                                              IsHTMLDocument::NonHTMLDocument,

components/script/dom/node.rs

@@ -29,7 +29,7 @@ use dom::bindings::str::{DOMString, USVString};
 use dom::bindings::xmlname::namespace_from_domstring;
 use dom::characterdata::{CharacterData, LayoutCharacterDataHelpers};
 use dom::cssstylesheet::CSSStyleSheet;
-use dom::document::{Document, DocumentSource, IsHTMLDocument};
+use dom::document::{Document, DocumentSource, HasBrowsingContext, IsHTMLDocument};
 use dom::documentfragment::DocumentFragment;
 use dom::documenttype::DocumentType;
 use dom::element::{Element, ElementCreator};
@@ -1726,7 +1726,7 @@ impl Node {
                 };
                 let window = document.window();
                 let loader = DocumentLoader::new(&*document.loader());
-                let document = Document::new(window, None,
+                let document = Document::new(window, HasBrowsingContext::No,
                                              Some(document.url()),
                                              // https://github.com/whatwg/dom/issues/378
                                              document.origin().alias(),

components/script/dom/servoparser/mod.rs

@@ -14,7 +14,7 @@ use dom::bindings::refcounted::Trusted;
 use dom::bindings::reflector::{Reflector, reflect_dom_object};
 use dom::bindings::str::DOMString;
 use dom::characterdata::CharacterData;
-use dom::document::{Document, DocumentSource, IsHTMLDocument};
+use dom::document::{Document, DocumentSource, HasBrowsingContext, IsHTMLDocument};
 use dom::element::Element;
 use dom::globalscope::GlobalScope;
 use dom::htmlformelement::HTMLFormElement;
@@ -102,7 +102,7 @@ impl ServoParser {
         let loader = DocumentLoader::new_with_threads(context_document.loader().resource_threads().clone(),
                                                       Some(url.clone()));
         let document = Document::new(window,
-                                     None,
+                                     HasBrowsingContext::No,
                                      Some(url.clone()),
                                      context_document.origin().alias(),
                                      IsHTMLDocument::HTMLDocument,