Revise lifetime management of IntersectionObservers.

Tag #249

8 files changed, 46 insertions, 26 deletions

diff --git a/dom/base/DOMIntersectionObserver.cpp b/dom/base/DOMIntersectionObserver.cpp
index e39abf1a6e..cb624fb17d 100644
--- a/dom/base/DOMIntersectionObserver.cpp
+++ b/dom/base/DOMIntersectionObserver.cpp
@@ -43,16 +43,18 @@ NS_IMPL_CYCLE_COLLECTION_TRACE_END
 
 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(DOMIntersectionObserver)
   NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
+  tmp->Disconnect();
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mOwner)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mDocument)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mCallback)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mRoot)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mQueuedEntries)
-  tmp->Disconnect();
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(DOMIntersectionObserver)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mOwner)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDocument)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mCallback)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mRoot)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mQueuedEntries)
@@ -185,10 +187,11 @@ DOMIntersectionObserver::Connect()
   if (mConnected) {
     return;
   }
+  
   mConnected = true;
-
-  nsIDocument* document = mOwner->GetExtantDoc();
-  document->AddIntersectionObserver(this);
+  if(mDocument) {
+    mDocument->AddIntersectionObserver(this);
+  }
 }
 
 void
@@ -202,11 +205,8 @@ DOMIntersectionObserver::Disconnect()
     target->UnregisterIntersectionObserver(this);
   }
   mObservationTargets.Clear();
-  if (mOwner) {
-    nsIDocument* document = mOwner->GetExtantDoc();
-    if (document) {
-      document->RemoveIntersectionObserver(this);
-    }
+  if (mDocument) {
+    mDocument->RemoveIntersectionObserver(this);
   }
   mConnected = false;
 }
diff --git a/dom/base/DOMIntersectionObserver.h b/dom/base/DOMIntersectionObserver.h
index 8144fc5c5c..c290002ea5 100644
--- a/dom/base/DOMIntersectionObserver.h
+++ b/dom/base/DOMIntersectionObserver.h
@@ -106,7 +106,10 @@ class DOMIntersectionObserver final : public nsISupports,
 public:
   DOMIntersectionObserver(already_AddRefed<nsPIDOMWindowInner>&& aOwner,
                           mozilla::dom::IntersectionCallback& aCb)
-  : mOwner(aOwner), mCallback(&aCb), mConnected(false)
+  : mOwner(aOwner)
+  , mDocument(mOwner->GetExtantDoc())
+  , mCallback(&aCb)
+  , mConnected(false)
   {
   }
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS
@@ -164,6 +167,7 @@ protected:
                                       double aIntersectionRatio);
 
   nsCOMPtr<nsPIDOMWindowInner>                    mOwner;
+  RefPtr<nsIDocument>                             mDocument;
   RefPtr<mozilla::dom::IntersectionCallback>      mCallback;
   RefPtr<Element>                                 mRoot;
   nsCSSRect                                       mRootMargin;
diff --git a/dom/base/Element.cpp b/dom/base/Element.cpp
index 3760dc43f4..67759fdb26 100644
--- a/dom/base/Element.cpp
+++ b/dom/base/Element.cpp
@@ -3947,7 +3947,7 @@ Element::ClearDataset()
   slots->mDataset = nullptr;
 }
 
-nsDataHashtable<nsPtrHashKey<DOMIntersectionObserver>, int32_t>*
+nsDataHashtable<nsRefPtrHashKey<DOMIntersectionObserver>, int32_t>*
 Element::RegisteredIntersectionObservers()
 {
   nsDOMSlots* slots = DOMSlots();
@@ -3962,7 +3962,7 @@ enum nsPreviousIntersectionThreshold {
 void
 Element::RegisterIntersectionObserver(DOMIntersectionObserver* aObserver)
 {
-  nsDataHashtable<nsPtrHashKey<DOMIntersectionObserver>, int32_t>* observers =
+  nsDataHashtable<nsRefPtrHashKey<DOMIntersectionObserver>, int32_t>* observers =
     RegisteredIntersectionObservers();
   if (observers->Contains(aObserver)) {
     return;
@@ -3979,7 +3979,7 @@ Element::RegisterIntersectionObserver(DOMIntersectionObserver* aObserver)
 void
 Element::UnregisterIntersectionObserver(DOMIntersectionObserver* aObserver)
 {
-  nsDataHashtable<nsPtrHashKey<DOMIntersectionObserver>, int32_t>* observers =
+  nsDataHashtable<nsRefPtrHashKey<DOMIntersectionObserver>, int32_t>* observers =
     RegisteredIntersectionObservers();
   observers->Remove(aObserver);
 }
@@ -3987,7 +3987,7 @@ Element::UnregisterIntersectionObserver(DOMIntersectionObserver* aObserver)
 bool
 Element::UpdateIntersectionObservation(DOMIntersectionObserver* aObserver, int32_t aThreshold)
 {
-  nsDataHashtable<nsPtrHashKey<DOMIntersectionObserver>, int32_t>* observers =
+  nsDataHashtable<nsRefPtrHashKey<DOMIntersectionObserver>, int32_t>* observers =
     RegisteredIntersectionObservers();
   if (!observers->Contains(aObserver)) {
     return false;
diff --git a/dom/base/Element.h b/dom/base/Element.h
index c269ab14aa..ef57a64668 100644
--- a/dom/base/Element.h
+++ b/dom/base/Element.h
@@ -1382,7 +1382,8 @@ protected:
   nsDOMTokenList* GetTokenList(nsIAtom* aAtom,
                                const DOMTokenListSupportedTokenArray aSupportedTokens = nullptr);
 
-  nsDataHashtable<nsPtrHashKey<DOMIntersectionObserver>, int32_t>* RegisteredIntersectionObservers();
+  nsDataHashtable<nsRefPtrHashKey<DOMIntersectionObserver>, int32_t>* 
+    RegisteredIntersectionObservers();
 
 private:
   /**
diff --git a/dom/base/FragmentOrElement.cpp b/dom/base/FragmentOrElement.cpp
index fde983e7cb..13ba19c8c6 100644
--- a/dom/base/FragmentOrElement.cpp
+++ b/dom/base/FragmentOrElement.cpp
@@ -585,6 +585,12 @@ FragmentOrElement::nsDOMSlots::Traverse(nsCycleCollectionTraversalCallback &cb,
       mCustomElementData->mCallbackQueue[i]->Traverse(cb);
     }
   }
+
+  for (auto iter = mRegisteredIntersectionObservers.Iter(); !iter.Done(); iter.Next()) {
+    DOMIntersectionObserver* observer = iter.Key();
+    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mSlots->mRegisteredIntersectionObservers[i]");
+    cb.NoteXPCOMChild(observer);
+  }
 }
 
 void
diff --git a/dom/base/FragmentOrElement.h b/dom/base/FragmentOrElement.h
index 7c74e9cd45..f0cc29f224 100644
--- a/dom/base/FragmentOrElement.h
+++ b/dom/base/FragmentOrElement.h
@@ -354,7 +354,8 @@ public:
     /**
      * Registered Intersection Observers on the element.
      */
-    nsDataHashtable<nsPtrHashKey<DOMIntersectionObserver>, int32_t> mRegisteredIntersectionObservers;
+    nsDataHashtable<nsRefPtrHashKey<DOMIntersectionObserver>, int32_t> 
+      mRegisteredIntersectionObservers;
   };
 
 protected:
diff --git a/dom/base/nsDocument.cpp b/dom/base/nsDocument.cpp
index ac9601caf1..e779c060c9 100644
--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -1736,8 +1736,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(nsDocument)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mOnDemandBuiltInUASheets)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mPreloadingImages)
 
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mIntersectionObservers)
-
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSubImportLinks)
 
   for (uint32_t i = 0; i < tmp->mFrameRequestCallbacks.Length(); ++i) {
@@ -12375,15 +12373,15 @@ nsDocument::ReportUseCounters()
 void
 nsDocument::AddIntersectionObserver(DOMIntersectionObserver* aObserver)
 {
-  NS_ASSERTION(mIntersectionObservers.IndexOf(aObserver) == nsTArray<int>::NoIndex,
-               "Intersection observer already in the list");
-  mIntersectionObservers.AppendElement(aObserver);
+  MOZ_ASSERT(!mIntersectionObservers.Contains(aObserver),
+             "Intersection observer already in the list");
+  mIntersectionObservers.PutEntry(aObserver);
 }
 
 void
 nsDocument::RemoveIntersectionObserver(DOMIntersectionObserver* aObserver)
 {
-  mIntersectionObservers.RemoveElement(aObserver);
+  mIntersectionObservers.RemoveEntry(aObserver);
 }
 
 void
@@ -12396,7 +12394,8 @@ nsDocument::UpdateIntersectionObservations()
       time = perf->Now();
     }
   }
-  for (const auto& observer : mIntersectionObservers) {
+  for (auto iter = mIntersectionObservers.Iter(); !iter.Done(); iter.Next()) {
+    DOMIntersectionObserver* observer = iter.Get()->GetKey();
     observer->Update(this, time);
   }
 }
@@ -12404,6 +12403,10 @@ nsDocument::UpdateIntersectionObservations()
 void
 nsDocument::ScheduleIntersectionObserverNotification()
 {
+  if (mIntersectionObservers.IsEmpty()) {
+    return;
+  }
+
   nsCOMPtr<nsIRunnable> notification = NewRunnableMethod(this,
     &nsDocument::NotifyIntersectionObservers);
   NS_DispatchToCurrentThread(notification);
@@ -12412,7 +12415,11 @@ nsDocument::ScheduleIntersectionObserverNotification()
 void
 nsDocument::NotifyIntersectionObservers()
 {
-  nsTArray<RefPtr<DOMIntersectionObserver>> observers(mIntersectionObservers);
+  nsTArray<RefPtr<DOMIntersectionObserver>> observers(mIntersectionObservers.Count());
+  for (auto iter = mIntersectionObservers.Iter(); !iter.Done(); iter.Next()) {
+    DOMIntersectionObserver* observer = iter.Get()->GetKey();
+    observers.AppendElement(observer);
+  }
   for (const auto& observer : observers) {
     observer->Notify();
   }
diff --git a/dom/base/nsDocument.h b/dom/base/nsDocument.h
index 3725b3c18f..d2f97a33e5 100644
--- a/dom/base/nsDocument.h
+++ b/dom/base/nsDocument.h
@@ -1341,8 +1341,9 @@ protected:
   // Array of observers
   nsTObserverArray<nsIDocumentObserver*> mObservers;
 
-  // Array of intersection observers
-  nsTArray<RefPtr<mozilla::dom::DOMIntersectionObserver>> mIntersectionObservers;
+  // Hashtable of intersection observers
+  nsTHashtable<nsPtrHashKey<mozilla::dom::DOMIntersectionObserver>>
+    mIntersectionObservers;
 
   // Tracker for animations that are waiting to start.
   // nullptr until GetOrCreatePendingAnimationTracker is called.