bug 1368547 part 1 - Remove nsFrameManagerBase::mPlaceholderMap and store the placeholder on a frame property on the out-of-flow instead. r=jfkthame

MozReview-Commit-ID: 6AOxc2XgtO1

layout/base/nsFrameManager.cpp

@@ -46,34 +46,9 @@ using namespace mozilla::dom;
 
 //----------------------------------------------------------------------
 
-struct PlaceholderMapEntry : public PLDHashEntryHdr {
-  // key (the out of flow frame) can be obtained through placeholder frame
-  nsPlaceholderFrame *placeholderFrame;
-};
-
-static bool
-PlaceholderMapMatchEntry(const PLDHashEntryHdr *hdr, const void *key)
-{
-  const PlaceholderMapEntry *entry =
-    static_cast<const PlaceholderMapEntry*>(hdr);
-  NS_ASSERTION(entry->placeholderFrame->GetOutOfFlowFrame() !=
-               (void*)0xdddddddd,
-               "Dead placeholder in placeholder map");
-  return entry->placeholderFrame->GetOutOfFlowFrame() == key;
-}
-
-static const PLDHashTableOps PlaceholderMapOps = {
-  PLDHashTable::HashVoidPtrKeyStub,
-  PlaceholderMapMatchEntry,
-  PLDHashTable::MoveEntryStub,
-  PLDHashTable::ClearEntryStub,
-  nullptr
-};
-
 nsFrameManagerBase::nsFrameManagerBase()
   : mPresShell(nullptr)
   , mRootFrame(nullptr)
-  , mPlaceholderMap(&PlaceholderMapOps, sizeof(PlaceholderMapEntry))
   , mUndisplayedMap(nullptr)
   , mDisplayContentsMap(nullptr)
   , mIsDestroyingFrames(false)
@@ -164,47 +139,30 @@ nsFrameManager::Destroy()
 nsPlaceholderFrame*
 nsFrameManager::GetPlaceholderFrameFor(const nsIFrame* aFrame)
 {
-  NS_PRECONDITION(aFrame, "null param unexpected");
-
-  auto entry = static_cast<PlaceholderMapEntry*>
-    (const_cast<PLDHashTable*>(&mPlaceholderMap)->Search(aFrame));
-  if (entry) {
-    return entry->placeholderFrame;
-  }
-
-  return nullptr;
+  MOZ_ASSERT(aFrame);
+  MOZ_ASSERT(aFrame->HasAnyStateBits(NS_FRAME_OUT_OF_FLOW));
+  return aFrame->GetProperty(nsIFrame::PlaceholderFrameProperty());
 }
 
 void
 nsFrameManager::RegisterPlaceholderFrame(nsPlaceholderFrame* aPlaceholderFrame)
 {
-  MOZ_ASSERT(aPlaceholderFrame, "null param unexpected");
-  MOZ_ASSERT(aPlaceholderFrame->IsPlaceholderFrame(), "unexpected frame type");
-  auto entry = static_cast<PlaceholderMapEntry*>
-    (mPlaceholderMap.Add(aPlaceholderFrame->GetOutOfFlowFrame()));
-  MOZ_ASSERT(!entry->placeholderFrame,
+  MOZ_ASSERT(aPlaceholderFrame);
+  MOZ_ASSERT(!GetPlaceholderFrameFor(aPlaceholderFrame->GetOutOfFlowFrame()),
              "Registering a placeholder for a frame that already has a placeholder!");
-  entry->placeholderFrame = aPlaceholderFrame;
+  aPlaceholderFrame->GetOutOfFlowFrame()->SetProperty(nsIFrame::PlaceholderFrameProperty(), aPlaceholderFrame);
 }
 
 void
 nsFrameManager::UnregisterPlaceholderFrame(nsPlaceholderFrame* aPlaceholderFrame)
 {
-  NS_PRECONDITION(aPlaceholderFrame, "null param unexpected");
-  NS_PRECONDITION(aPlaceholderFrame->IsPlaceholderFrame(),
-                  "unexpected frame type");
-
-  mPlaceholderMap.Remove(aPlaceholderFrame->GetOutOfFlowFrame());
+  MOZ_ASSERT(aPlaceholderFrame);
+  aPlaceholderFrame->GetOutOfFlowFrame()->DeleteProperty(nsIFrame::PlaceholderFrameProperty());
 }
 
 void
 nsFrameManager::ClearPlaceholderFrameMap()
 {
-  for (auto iter = mPlaceholderMap.Iter(); !iter.Done(); iter.Next()) {
-    auto entry = static_cast<PlaceholderMapEntry*>(iter.Get());
-    entry->placeholderFrame->SetOutOfFlowFrame(nullptr);
-  }
-  mPlaceholderMap.Clear();
 }
 
 //----------------------------------------------------------------------

layout/base/nsFrameManagerBase.h

@@ -51,7 +51,6 @@ protected:
   // weak link, because the pres shell owns us
   nsIPresShell* MOZ_NON_OWNING_REF mPresShell;
   nsIFrame*                       mRootFrame;
-  PLDHashTable                    mPlaceholderMap;
   UndisplayedMap*                 mUndisplayedMap;
   UndisplayedMap*                 mDisplayContentsMap;
   bool                            mIsDestroyingFrames;  // The frame manager is destroying some frame(s).

layout/generic/nsFrame.cpp

@@ -735,7 +735,6 @@ nsFrame::DestroyFrom(nsIFrame* aDestructRoot)
                  "Placeholder relationship should have been torn down already; "
                  "this might mean we have a stray placeholder in the tree.");
     if (placeholder) {
-      shell->FrameManager()->UnregisterPlaceholderFrame(placeholder);
       placeholder->SetOutOfFlowFrame(nullptr);
     }
   }

layout/generic/nsIFrame.h

@@ -83,6 +83,7 @@ class nsLineList_iterator;
 class nsAbsoluteContainingBlock;
 class nsIContent;
 class nsContainerFrame;
+class nsPlaceholderFrame;
 class nsStyleChangeList;
 
 struct nsPeekOffsetStruct;
@@ -1186,6 +1187,8 @@ public:
 
   NS_DECLARE_FRAME_PROPERTY_SMALL_VALUE(BidiDataProperty, mozilla::FrameBidiData)
 
+  NS_DECLARE_FRAME_PROPERTY_WITHOUT_DTOR(PlaceholderFrameProperty, nsPlaceholderFrame)
+
   mozilla::FrameBidiData GetBidiData() const
   {
     bool exists;

layout/generic/nsPlaceholderFrame.cpp

@@ -160,16 +160,15 @@ nsPlaceholderFrame::DestroyFrom(nsIFrame* aDestructRoot)
 {
   nsIFrame* oof = mOutOfFlowFrame;
   if (oof) {
-    // Unregister out-of-flow frame
-    nsFrameManager* fm = PresContext()->GetPresShell()->FrameManager();
-    fm->UnregisterPlaceholderFrame(this);
     mOutOfFlowFrame = nullptr;
+    oof->DeleteProperty(nsIFrame::PlaceholderFrameProperty());
     // If aDestructRoot is not an ancestor of the out-of-flow frame,
     // then call RemoveFrame on it here.
     // Also destroy it here if it's a popup frame. (Bug 96291)
     if ((GetStateBits() & PLACEHOLDER_FOR_POPUP) ||
         !nsLayoutUtils::IsProperAncestorFrame(aDestructRoot, oof)) {
       ChildListID listId = nsLayoutUtils::GetChildListNameFor(oof);
+      nsFrameManager* fm = PresContext()->GetPresShell()->FrameManager();
       fm->RemoveFrame(listId, oof);
     }
     // else oof will be destroyed by its parent