The Tor Browser: layout/base/nsFrameManager.cpp@b8a032363ba2 (annotated)

layout/base/nsFrameManager.cpp@b8a032363ba2 (annotated)

layout/base/nsFrameManager.cpp

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
  * vim:cindent:ts=2:et:sw=2:
  *
  * This Source Code Form is subject to the terms of the Mozilla Public
  * 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/.
  *
  * This Original Code has been modified by IBM Corporation. Modifications made by IBM
  * described herein are Copyright (c) International Business Machines Corporation, 2000.
  * Modifications to Mozilla code or documentation identified per MPL Section 3.3
  *
  * Date             Modified by     Description of modification
  * 04/20/2000       IBM Corp.      OS/2 VisualAge build.
  */
 /* storage of the frame tree and information about it */
 #include "nscore.h"
 #include "nsIPresShell.h"
 #include "nsStyleContext.h"
 #include "nsCOMPtr.h"
 #include "plhash.h"
 #include "nsPlaceholderFrame.h"
 #include "nsGkAtoms.h"
 #include "nsILayoutHistoryState.h"
 #include "nsPresState.h"
 #include "mozilla/dom/Element.h"
 #include "nsIDocument.h"
 #include "nsContentUtils.h"
 #include "nsError.h"
 #include "nsAutoPtr.h"
 #include "nsAbsoluteContainingBlock.h"
 #include "ChildIterator.h"
 #include "nsFrameManager.h"
 #include "GeckoProfiler.h"
 #include "nsIStatefulFrame.h"
   #ifdef DEBUG
     //#define DEBUG_UNDISPLAYED_MAP
   #else
     #undef DEBUG_UNDISPLAYED_MAP
   #endif
 using namespace mozilla;
 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(PLDHashTable *table, 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 = {
   PL_DHashAllocTable,
   PL_DHashFreeTable,
   PL_DHashVoidPtrKeyStub,
   PlaceholderMapMatchEntry,
   PL_DHashMoveEntryStub,
   PL_DHashClearEntryStub,
   PL_DHashFinalizeStub,
   nullptr
 };
 //----------------------------------------------------------------------
 // XXXldb This seems too complicated for what I think it's doing, and it
 // should also be using pldhash rather than plhash to use less memory.
 class nsFrameManagerBase::UndisplayedMap {
 public:
   UndisplayedMap(uint32_t aNumBuckets = 16) NS_HIDDEN;
   ~UndisplayedMap(void) NS_HIDDEN;
   NS_HIDDEN_(UndisplayedNode*) GetFirstNode(nsIContent* aParentContent);
   NS_HIDDEN_(nsresult) AddNodeFor(nsIContent* aParentContent,
                                   nsIContent* aChild, nsStyleContext* aStyle);
   NS_HIDDEN_(void) RemoveNodeFor(nsIContent* aParentContent,
                                  UndisplayedNode* aNode);
   NS_HIDDEN_(void) RemoveNodesFor(nsIContent* aParentContent);
   // Removes all entries from the hash table
   NS_HIDDEN_(void)  Clear(void);
 protected:
   /**
    * Gets the entry for the provided parent content. If the content
    * is a <xbl:children> element, |**aParentContent| is set to
    * the parent of the children element.
    */
   NS_HIDDEN_(PLHashEntry**) GetEntryFor(nsIContent** aParentContent);
   NS_HIDDEN_(void)          AppendNodeFor(UndisplayedNode* aNode,
                                           nsIContent* aParentContent);
   PLHashTable*  mTable;
   PLHashEntry** mLastLookup;
 };
 //----------------------------------------------------------------------
 nsFrameManager::~nsFrameManager()
 {
   NS_ASSERTION(!mPresShell, "nsFrameManager::Destroy never called");
 }
 void
 nsFrameManager::Destroy()
 {
   NS_ASSERTION(mPresShell, "Frame manager already shut down.");
   // Destroy the frame hierarchy.
   mPresShell->SetIgnoreFrameDestruction(true);
   // Unregister all placeholders before tearing down the frame tree
   nsFrameManager::ClearPlaceholderFrameMap();
   if (mRootFrame) {
     mRootFrame->Destroy();
     mRootFrame = nullptr;
   }
   delete mUndisplayedMap;
   mUndisplayedMap = nullptr;
   mPresShell = nullptr;
 }
 //----------------------------------------------------------------------
 // Placeholder frame functions
 nsPlaceholderFrame*
 nsFrameManager::GetPlaceholderFrameFor(const nsIFrame* aFrame)
 {
   NS_PRECONDITION(aFrame, "null param unexpected");
   if (mPlaceholderMap.ops) {
     PlaceholderMapEntry *entry = static_cast<PlaceholderMapEntry*>
                                             (PL_DHashTableOperate(const_cast<PLDHashTable*>(&mPlaceholderMap),
                                 aFrame, PL_DHASH_LOOKUP));
     if (PL_DHASH_ENTRY_IS_BUSY(entry)) {
       return entry->placeholderFrame;
     }
   }
   return nullptr;
 }
 nsresult
 nsFrameManager::RegisterPlaceholderFrame(nsPlaceholderFrame* aPlaceholderFrame)
 {
   NS_PRECONDITION(aPlaceholderFrame, "null param unexpected");
   NS_PRECONDITION(nsGkAtoms::placeholderFrame == aPlaceholderFrame->GetType(),
                   "unexpected frame type");
   if (!mPlaceholderMap.ops) {
     PL_DHashTableInit(&mPlaceholderMap, &PlaceholderMapOps, nullptr,
                       sizeof(PlaceholderMapEntry), 16);
   }
   PlaceholderMapEntry *entry = static_cast<PlaceholderMapEntry*>(PL_DHashTableOperate(&mPlaceholderMap,
                               aPlaceholderFrame->GetOutOfFlowFrame(),
                               PL_DHASH_ADD));
   if (!entry)
     return NS_ERROR_OUT_OF_MEMORY;
   NS_ASSERTION(!entry->placeholderFrame, "Registering a placeholder for a frame that already has a placeholder!");
   entry->placeholderFrame = aPlaceholderFrame;
   return NS_OK;
 }
 void
 nsFrameManager::UnregisterPlaceholderFrame(nsPlaceholderFrame* aPlaceholderFrame)
 {
   NS_PRECONDITION(aPlaceholderFrame, "null param unexpected");
   NS_PRECONDITION(nsGkAtoms::placeholderFrame == aPlaceholderFrame->GetType(),
                   "unexpected frame type");
   if (mPlaceholderMap.ops) {
     PL_DHashTableOperate(&mPlaceholderMap,
                          aPlaceholderFrame->GetOutOfFlowFrame(),
                          PL_DHASH_REMOVE);
   }
 }
 static PLDHashOperator
 UnregisterPlaceholders(PLDHashTable* table, PLDHashEntryHdr* hdr,
                        uint32_t number, void* arg)
 {
   PlaceholderMapEntry* entry = static_cast<PlaceholderMapEntry*>(hdr);
   entry->placeholderFrame->SetOutOfFlowFrame(nullptr);
   return PL_DHASH_NEXT;
 }
 void
 nsFrameManager::ClearPlaceholderFrameMap()
 {
   if (mPlaceholderMap.ops) {
     PL_DHashTableEnumerate(&mPlaceholderMap, UnregisterPlaceholders, nullptr);
     PL_DHashTableFinish(&mPlaceholderMap);
     mPlaceholderMap.ops = nullptr;
   }
 }
 //----------------------------------------------------------------------
 nsStyleContext*
 nsFrameManager::GetUndisplayedContent(nsIContent* aContent)
 {
   if (!aContent || !mUndisplayedMap)
     return nullptr;
   nsIContent* parent = aContent->GetParent();
   for (UndisplayedNode* node = mUndisplayedMap->GetFirstNode(parent);
          node; node = node->mNext) {
     if (node->mContent == aContent)
       return node->mStyle;
   }
   return nullptr;
 }
 UndisplayedNode*
 nsFrameManager::GetAllUndisplayedContentIn(nsIContent* aParentContent)
 {
   if (!mUndisplayedMap)
     return nullptr;
   return mUndisplayedMap->GetFirstNode(aParentContent);
 }
 void
 nsFrameManager::SetUndisplayedContent(nsIContent* aContent,
                                       nsStyleContext* aStyleContext)
 {
   NS_PRECONDITION(!aStyleContext->GetPseudo(),
                   "Should only have actual elements here");
 #ifdef DEBUG_UNDISPLAYED_MAP
   static int i = 0;
   printf("SetUndisplayedContent(%d): p=%p \n", i++, (void *)aContent);
 #endif
   NS_ASSERTION(!GetUndisplayedContent(aContent),
                "Already have an undisplayed context entry for aContent");
   if (! mUndisplayedMap) {
     mUndisplayedMap = new UndisplayedMap;
   }
   nsIContent* parent = aContent->GetParent();
   NS_ASSERTION(parent || (mPresShell && mPresShell->GetDocument() &&
                mPresShell->GetDocument()->GetRootElement() == aContent),
                "undisplayed content must have a parent, unless it's the root "
                "element");
   mUndisplayedMap->AddNodeFor(parent, aContent, aStyleContext);
 }
 void
 nsFrameManager::ChangeUndisplayedContent(nsIContent* aContent,
                                          nsStyleContext* aStyleContext)
 {
   NS_ASSERTION(mUndisplayedMap, "no existing undisplayed content");
 #ifdef DEBUG_UNDISPLAYED_MAP
    static int i = 0;
    printf("ChangeUndisplayedContent(%d): p=%p \n", i++, (void *)aContent);
 #endif
   for (UndisplayedNode* node = mUndisplayedMap->GetFirstNode(aContent->GetParent());
          node; node = node->mNext) {
     if (node->mContent == aContent) {
       node->mStyle = aStyleContext;
       return;
     }
   }
   NS_NOTREACHED("no existing undisplayed content");
 }
 void
 nsFrameManager::ClearUndisplayedContentIn(nsIContent* aContent,
                                           nsIContent* aParentContent)
 {
 #ifdef DEBUG_UNDISPLAYED_MAP
   static int i = 0;
   printf("ClearUndisplayedContent(%d): content=%p parent=%p --> ", i++, (void *)aContent, (void*)aParentContent);
 #endif
   if (mUndisplayedMap) {
     UndisplayedNode* node = mUndisplayedMap->GetFirstNode(aParentContent);
     while (node) {
       if (node->mContent == aContent) {
         mUndisplayedMap->RemoveNodeFor(aParentContent, node);
 #ifdef DEBUG_UNDISPLAYED_MAP
         printf( "REMOVED!\n");
 #endif
 #ifdef DEBUG
         // make sure that there are no more entries for the same content
         nsStyleContext *context = GetUndisplayedContent(aContent);
         NS_ASSERTION(context == nullptr, "Found more undisplayed content data after removal");
 #endif
         return;
       }
       node = node->mNext;
     }
   }
 }
 void
 nsFrameManager::ClearAllUndisplayedContentIn(nsIContent* aParentContent)
 {
 #ifdef DEBUG_UNDISPLAYED_MAP
   static int i = 0;
   printf("ClearAllUndisplayedContentIn(%d): parent=%p \n", i++, (void*)aParentContent);
 #endif
   if (mUndisplayedMap) {
     mUndisplayedMap->RemoveNodesFor(aParentContent);
   }
   // Need to look at aParentContent's content list due to XBL insertions.
   // Nodes in aParentContent's content list do not have aParentContent as a
   // parent, but are treated as children of aParentContent. We iterate over
   // the flattened content list and just ignore any nodes we don't care about.
   FlattenedChildIterator iter(aParentContent);
   for (nsIContent* child = iter.GetNextChild(); child; child = iter.GetNextChild()) {
     if (child->GetParent() != aParentContent) {
       ClearUndisplayedContentIn(child, child->GetParent());
     }
   }
 }
 //----------------------------------------------------------------------
 nsresult
 nsFrameManager::AppendFrames(nsIFrame*       aParentFrame,
                              ChildListID     aListID,
                              nsFrameList&    aFrameList)
 {
   if (aParentFrame->IsAbsoluteContainer() &&
       aListID == aParentFrame->GetAbsoluteListID()) {
     return aParentFrame->GetAbsoluteContainingBlock()->
            AppendFrames(aParentFrame, aListID, aFrameList);
   } else {
     return aParentFrame->AppendFrames(aListID, aFrameList);
   }
 }
 nsresult
 nsFrameManager::InsertFrames(nsIFrame*       aParentFrame,
                              ChildListID     aListID,
                              nsIFrame*       aPrevFrame,
                              nsFrameList&    aFrameList)
 {
   NS_PRECONDITION(!aPrevFrame || (!aPrevFrame->GetNextContinuation()
                   || (((aPrevFrame->GetNextContinuation()->GetStateBits() & NS_FRAME_IS_OVERFLOW_CONTAINER))
                   && !(aPrevFrame->GetStateBits() & NS_FRAME_IS_OVERFLOW_CONTAINER))),
                   "aPrevFrame must be the last continuation in its chain!");
   if (aParentFrame->IsAbsoluteContainer() &&
       aListID == aParentFrame->GetAbsoluteListID()) {
     return aParentFrame->GetAbsoluteContainingBlock()->
            InsertFrames(aParentFrame, aListID, aPrevFrame, aFrameList);
   } else {
     return aParentFrame->InsertFrames(aListID, aPrevFrame, aFrameList);
   }
 }
 nsresult
 nsFrameManager::RemoveFrame(ChildListID     aListID,
                             nsIFrame*       aOldFrame)
 {
   bool wasDestroyingFrames = mIsDestroyingFrames;
   mIsDestroyingFrames = true;
   // In case the reflow doesn't invalidate anything since it just leaves
   // a gap where the old frame was, we invalidate it here.  (This is
   // reasonably likely to happen when removing a last child in a way
   // that doesn't change the size of the parent.)
   // This has to sure to invalidate the entire overflow rect; this
   // is important in the presence of absolute positioning
   aOldFrame->InvalidateFrameForRemoval();
   NS_ASSERTION(!aOldFrame->GetPrevContinuation() ||
                // exception for nsCSSFrameConstructor::RemoveFloatingFirstLetterFrames
                aOldFrame->GetType() == nsGkAtoms::textFrame,
                "Must remove first continuation.");
   NS_ASSERTION(!(aOldFrame->GetStateBits() & NS_FRAME_OUT_OF_FLOW &&
                  GetPlaceholderFrameFor(aOldFrame)),
                "Must call RemoveFrame on placeholder for out-of-flows.");
   nsresult rv = NS_OK;
   nsIFrame* parentFrame = aOldFrame->GetParent();
   if (parentFrame->IsAbsoluteContainer() &&
       aListID == parentFrame->GetAbsoluteListID()) {
     parentFrame->GetAbsoluteContainingBlock()->
       RemoveFrame(parentFrame, aListID, aOldFrame);
   } else {
     rv = parentFrame->RemoveFrame(aListID, aOldFrame);
   }
   mIsDestroyingFrames = wasDestroyingFrames;
   return rv;
 }
 //----------------------------------------------------------------------
 void
 nsFrameManager::NotifyDestroyingFrame(nsIFrame* aFrame)
 {
   nsIContent* content = aFrame->GetContent();
   if (content && content->GetPrimaryFrame() == aFrame) {
     ClearAllUndisplayedContentIn(content);
   }
 }
 // Capture state for a given frame.
 // Accept a content id here, in some cases we may not have content (scroll position)
 void
 nsFrameManager::CaptureFrameStateFor(nsIFrame* aFrame,
                                      nsILayoutHistoryState* aState)
 {
   if (!aFrame || !aState) {
     NS_WARNING("null frame, or state");
     return;
   }
   // Only capture state for stateful frames
   nsIStatefulFrame* statefulFrame = do_QueryFrame(aFrame);
   if (!statefulFrame) {
     return;
   }
   // Capture the state, exit early if we get null (nothing to save)
   nsAutoPtr<nsPresState> frameState;
   nsresult rv = statefulFrame->SaveState(getter_Transfers(frameState));
   if (!frameState) {
     return;
   }
   // Generate the hash key to store the state under
   // Exit early if we get empty key
   nsAutoCString stateKey;
   nsIContent* content = aFrame->GetContent();
   nsIDocument* doc = content ? content->GetCurrentDoc() : nullptr;
   rv = nsContentUtils::GenerateStateKey(content, doc, stateKey);
   if(NS_FAILED(rv) || stateKey.IsEmpty()) {
     return;
   }
   // Store the state. aState owns frameState now.
   aState->AddState(stateKey, frameState.forget());
 }
 void
 nsFrameManager::CaptureFrameState(nsIFrame* aFrame,
                                   nsILayoutHistoryState* aState)
 {
   NS_PRECONDITION(nullptr != aFrame && nullptr != aState, "null parameters passed in");
   CaptureFrameStateFor(aFrame, aState);
   // Now capture state recursively for the frame hierarchy rooted at aFrame
   nsIFrame::ChildListIterator lists(aFrame);
   for (; !lists.IsDone(); lists.Next()) {
     nsFrameList::Enumerator childFrames(lists.CurrentList());
     for (; !childFrames.AtEnd(); childFrames.Next()) {
       nsIFrame* child = childFrames.get();
       if (child->GetStateBits() & NS_FRAME_OUT_OF_FLOW) {
         // We'll pick it up when we get to its placeholder
         continue;
       }
       // Make sure to walk through placeholders as needed, so that we
       // save state for out-of-flows which may not be our descendants
       // themselves but whose placeholders are our descendants.
       CaptureFrameState(nsPlaceholderFrame::GetRealFrameFor(child), aState);
     }
   }
 }
 // Restore state for a given frame.
 // Accept a content id here, in some cases we may not have content (scroll position)
 void
 nsFrameManager::RestoreFrameStateFor(nsIFrame* aFrame,
                                      nsILayoutHistoryState* aState)
 {
   if (!aFrame || !aState) {
     NS_WARNING("null frame or state");
     return;
   }
   // Only restore state for stateful frames
   nsIStatefulFrame* statefulFrame = do_QueryFrame(aFrame);
   if (!statefulFrame) {
     return;
   }
   // Generate the hash key the state was stored under
   // Exit early if we get empty key
   nsIContent* content = aFrame->GetContent();
   // If we don't have content, we can't generate a hash
   // key and there's probably no state information for us.
   if (!content) {
     return;
   }
   nsAutoCString stateKey;
   nsIDocument* doc = content->GetCurrentDoc();
   nsresult rv = nsContentUtils::GenerateStateKey(content, doc, stateKey);
   if (NS_FAILED(rv) || stateKey.IsEmpty()) {
     return;
   }
   // Get the state from the hash
   nsPresState* frameState = aState->GetState(stateKey);
   if (!frameState) {
     return;
   }
   // Restore it
   rv = statefulFrame->RestoreState(frameState);
   if (NS_FAILED(rv)) {
     return;
   }
   // If we restore ok, remove the state from the state table
   aState->RemoveState(stateKey);
 }
 void
 nsFrameManager::RestoreFrameState(nsIFrame* aFrame,
                                   nsILayoutHistoryState* aState)
 {
   NS_PRECONDITION(nullptr != aFrame && nullptr != aState, "null parameters passed in");
   RestoreFrameStateFor(aFrame, aState);
   // Now restore state recursively for the frame hierarchy rooted at aFrame
   nsIFrame::ChildListIterator lists(aFrame);
   for (; !lists.IsDone(); lists.Next()) {
     nsFrameList::Enumerator childFrames(lists.CurrentList());
     for (; !childFrames.AtEnd(); childFrames.Next()) {
       RestoreFrameState(childFrames.get(), aState);
     }
   }
 }
 //----------------------------------------------------------------------
 static PLHashNumber
 HashKey(void* key)
 {
   return NS_PTR_TO_INT32(key);
 }
 static int
 CompareKeys(void* key1, void* key2)
 {
   return key1 == key2;
 }
 //----------------------------------------------------------------------
 nsFrameManagerBase::UndisplayedMap::UndisplayedMap(uint32_t aNumBuckets)
 {
   MOZ_COUNT_CTOR(nsFrameManagerBase::UndisplayedMap);
   mTable = PL_NewHashTable(aNumBuckets, (PLHashFunction)HashKey,
                            (PLHashComparator)CompareKeys,
                            (PLHashComparator)nullptr,
                            nullptr, nullptr);
   mLastLookup = nullptr;
 }
 nsFrameManagerBase::UndisplayedMap::~UndisplayedMap(void)
 {
   MOZ_COUNT_DTOR(nsFrameManagerBase::UndisplayedMap);
   Clear();
   PL_HashTableDestroy(mTable);
 }
 PLHashEntry**
 nsFrameManagerBase::UndisplayedMap::GetEntryFor(nsIContent** aParentContent)
 {
   nsIContent* parentContent = *aParentContent;
   if (mLastLookup && (parentContent == (*mLastLookup)->key)) {
     return mLastLookup;
   }
   // In the case of XBL default content, <xbl:children> elements do not get a
   // frame causing a mismatch between the content tree and the frame tree.
   // |GetEntryFor| is sometimes called with the content tree parent (which may
   // be a <xbl:children> element) but the parent in the frame tree would be the
   // insertion parent (parent of the <xbl:children> element). Here the children
   // elements are normalized to the insertion parent to correct for the mismatch.
   if (parentContent && nsContentUtils::IsContentInsertionPoint(parentContent)) {
     parentContent = parentContent->GetParent();
     // Change the caller's pointer for the parent content to be the insertion parent.
     *aParentContent = parentContent;
   }
   PLHashNumber hashCode = NS_PTR_TO_INT32(parentContent);
   PLHashEntry** entry = PL_HashTableRawLookup(mTable, hashCode, parentContent);
   if (*entry) {
     mLastLookup = entry;
   }
   return entry;
 }
 UndisplayedNode*
 nsFrameManagerBase::UndisplayedMap::GetFirstNode(nsIContent* aParentContent)
 {
   PLHashEntry** entry = GetEntryFor(&aParentContent);
   if (*entry) {
     return (UndisplayedNode*)((*entry)->value);
   }
   return nullptr;
 }
 void
 nsFrameManagerBase::UndisplayedMap::AppendNodeFor(UndisplayedNode* aNode,
                                                   nsIContent* aParentContent)
 {
   PLHashEntry** entry = GetEntryFor(&aParentContent);
   if (*entry) {
     UndisplayedNode*  node = (UndisplayedNode*)((*entry)->value);
     while (node->mNext) {
       if (node->mContent == aNode->mContent) {
         // We actually need to check this in optimized builds because
         // there are some callers that do this.  See bug 118014, bug
         // 136704, etc.
         NS_NOTREACHED("node in map twice");
         delete aNode;
         return;
       }
       node = node->mNext;
     }
     node->mNext = aNode;
   }
   else {
     PLHashNumber hashCode = NS_PTR_TO_INT32(aParentContent);
     PL_HashTableRawAdd(mTable, entry, hashCode, aParentContent, aNode);
     mLastLookup = nullptr; // hashtable may have shifted bucket out from under us
   }
 }
 nsresult
 nsFrameManagerBase::UndisplayedMap::AddNodeFor(nsIContent* aParentContent,
                                                nsIContent* aChild,
                                                nsStyleContext* aStyle)
 {
   UndisplayedNode*  node = new UndisplayedNode(aChild, aStyle);
   AppendNodeFor(node, aParentContent);
   return NS_OK;
 }
 void
 nsFrameManagerBase::UndisplayedMap::RemoveNodeFor(nsIContent* aParentContent,
                                                   UndisplayedNode* aNode)
 {
   PLHashEntry** entry = GetEntryFor(&aParentContent);
   NS_ASSERTION(*entry, "content not in map");
   if (*entry) {
     if ((UndisplayedNode*)((*entry)->value) == aNode) {  // first node
       if (aNode->mNext) {
         (*entry)->value = aNode->mNext;
         aNode->mNext = nullptr;
       }
       else {
         PL_HashTableRawRemove(mTable, entry, *entry);
         mLastLookup = nullptr; // hashtable may have shifted bucket out from under us
       }
     }
     else {
       UndisplayedNode*  node = (UndisplayedNode*)((*entry)->value);
       while (node->mNext) {
         if (node->mNext == aNode) {
           node->mNext = aNode->mNext;
           aNode->mNext = nullptr;
           break;
         }
         node = node->mNext;
       }
     }
   }
   delete aNode;
 }
 void
 nsFrameManagerBase::UndisplayedMap::RemoveNodesFor(nsIContent* aParentContent)
 {
   PLHashEntry** entry = GetEntryFor(&aParentContent);
   NS_ASSERTION(entry, "content not in map");
   if (*entry) {
     UndisplayedNode*  node = (UndisplayedNode*)((*entry)->value);
     NS_ASSERTION(node, "null node for non-null entry in UndisplayedMap");
     delete node;
     PL_HashTableRawRemove(mTable, entry, *entry);
     mLastLookup = nullptr; // hashtable may have shifted bucket out from under us
   }
 }
 static int
 RemoveUndisplayedEntry(PLHashEntry* he, int i, void* arg)
 {
   UndisplayedNode*  node = (UndisplayedNode*)(he->value);
   delete node;
   // Remove and free this entry and continue enumerating
   return HT_ENUMERATE_REMOVE | HT_ENUMERATE_NEXT;
 }
 void
 nsFrameManagerBase::UndisplayedMap::Clear(void)
 {
   mLastLookup = nullptr;
   PL_HashTableEnumerateEntries(mTable, RemoveUndisplayedEntry, 0);
 }
 uint32_t nsFrameManagerBase::sGlobalGenerationNumber;

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layout/base/nsFrameManager.cpp