Add m-esr52 at 52.6.0

1 files changed, 752 insertions, 0 deletions

diff --git a/editor/txmgr/nsTransactionManager.cpp b/editor/txmgr/nsTransactionManager.cpp
new file mode 100644
index 000000000..10f9c3d06
--- /dev/null
+++ b/editor/txmgr/nsTransactionManager.cpp
@@ -0,0 +1,752 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 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/. */
+
+#include "mozilla/Assertions.h"
+#include "mozilla/mozalloc.h"
+#include "nsCOMPtr.h"
+#include "nsDebug.h"
+#include "nsError.h"
+#include "nsISupportsBase.h"
+#include "nsISupportsUtils.h"
+#include "nsITransaction.h"
+#include "nsITransactionList.h"
+#include "nsITransactionListener.h"
+#include "nsIWeakReference.h"
+#include "nsTransactionItem.h"
+#include "nsTransactionList.h"
+#include "nsTransactionManager.h"
+#include "nsTransactionStack.h"
+
+nsTransactionManager::nsTransactionManager(int32_t aMaxTransactionCount)
+  : mMaxTransactionCount(aMaxTransactionCount)
+  , mDoStack(nsTransactionStack::FOR_UNDO)
+  , mUndoStack(nsTransactionStack::FOR_UNDO)
+  , mRedoStack(nsTransactionStack::FOR_REDO)
+{
+}
+
+nsTransactionManager::~nsTransactionManager()
+{
+}
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(nsTransactionManager)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsTransactionManager)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mListeners)
+  tmp->mDoStack.DoUnlink();
+  tmp->mUndoStack.DoUnlink();
+  tmp->mRedoStack.DoUnlink();
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsTransactionManager)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mListeners)
+  tmp->mDoStack.DoTraverse(cb);
+  tmp->mUndoStack.DoTraverse(cb);
+  tmp->mRedoStack.DoTraverse(cb);
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsTransactionManager)
+  NS_INTERFACE_MAP_ENTRY(nsITransactionManager)
+  NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsITransactionManager)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(nsTransactionManager)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(nsTransactionManager)
+
+NS_IMETHODIMP
+nsTransactionManager::DoTransaction(nsITransaction *aTransaction)
+{
+  NS_ENSURE_TRUE(aTransaction, NS_ERROR_NULL_POINTER);
+
+  bool doInterrupt = false;
+
+  nsresult rv = WillDoNotify(aTransaction, &doInterrupt);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  if (doInterrupt) {
+    return NS_OK;
+  }
+
+  rv = BeginTransaction(aTransaction, nullptr);
+  if (NS_FAILED(rv)) {
+    DidDoNotify(aTransaction, rv);
+    return rv;
+  }
+
+  rv = EndTransaction(false);
+
+  nsresult rv2 = DidDoNotify(aTransaction, rv);
+  if (NS_SUCCEEDED(rv)) {
+    rv = rv2;
+  }
+
+  // XXX The result of EndTransaction() or DidDoNotify() if EndTransaction()
+  //     succeeded.
+  return rv;
+}
+
+NS_IMETHODIMP
+nsTransactionManager::UndoTransaction()
+{
+  // It is illegal to call UndoTransaction() while the transaction manager is
+  // executing a  transaction's DoTransaction() method! If this happens,
+  // the UndoTransaction() request is ignored, and we return NS_ERROR_FAILURE.
+  if (!mDoStack.IsEmpty()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Peek at the top of the undo stack. Don't remove the transaction
+  // until it has successfully completed.
+  RefPtr<nsTransactionItem> tx = mUndoStack.Peek();
+  if (!tx) {
+    // Bail if there's nothing on the stack.
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsITransaction> t = tx->GetTransaction();
+  bool doInterrupt = false;
+  nsresult rv = WillUndoNotify(t, &doInterrupt);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  if (doInterrupt) {
+    return NS_OK;
+  }
+
+  rv = tx->UndoTransaction(this);
+  if (NS_SUCCEEDED(rv)) {
+    tx = mUndoStack.Pop();
+    mRedoStack.Push(tx.forget());
+  }
+
+  nsresult rv2 = DidUndoNotify(t, rv);
+  if (NS_SUCCEEDED(rv)) {
+    rv = rv2;
+  }
+
+  // XXX The result of UndoTransaction() or DidUndoNotify() if UndoTransaction()
+  //     succeeded.
+  return rv;
+}
+
+NS_IMETHODIMP
+nsTransactionManager::RedoTransaction()
+{
+  // It is illegal to call RedoTransaction() while the transaction manager is
+  // executing a  transaction's DoTransaction() method! If this happens,
+  // the RedoTransaction() request is ignored, and we return NS_ERROR_FAILURE.
+  if (!mDoStack.IsEmpty()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Peek at the top of the redo stack. Don't remove the transaction
+  // until it has successfully completed.
+  RefPtr<nsTransactionItem> tx = mRedoStack.Peek();
+  if (!tx) {
+    // Bail if there's nothing on the stack.
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsITransaction> t = tx->GetTransaction();
+  bool doInterrupt = false;
+  nsresult rv = WillRedoNotify(t, &doInterrupt);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  if (doInterrupt) {
+    return NS_OK;
+  }
+
+  rv = tx->RedoTransaction(this);
+  if (NS_SUCCEEDED(rv)) {
+    tx = mRedoStack.Pop();
+    mUndoStack.Push(tx.forget());
+  }
+
+  nsresult rv2 = DidRedoNotify(t, rv);
+  if (NS_SUCCEEDED(rv)) {
+    rv = rv2;
+  }
+
+  // XXX The result of RedoTransaction() or DidRedoNotify() if RedoTransaction()
+  //     succeeded.
+  return rv;
+}
+
+NS_IMETHODIMP
+nsTransactionManager::Clear()
+{
+  nsresult rv = ClearRedoStack();
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  return ClearUndoStack();
+}
+
+NS_IMETHODIMP
+nsTransactionManager::BeginBatch(nsISupports* aData)
+{
+  // We can batch independent transactions together by simply pushing
+  // a dummy transaction item on the do stack. This dummy transaction item
+  // will be popped off the do stack, and then pushed on the undo stack
+  // in EndBatch().
+  bool doInterrupt = false;
+  nsresult rv = WillBeginBatchNotify(&doInterrupt);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  if (doInterrupt) {
+    return NS_OK;
+  }
+
+  rv = BeginTransaction(0, aData);
+
+  nsresult rv2 = DidBeginBatchNotify(rv);
+  if (NS_SUCCEEDED(rv)) {
+    rv = rv2;
+  }
+
+  // XXX The result of BeginTransaction() or DidBeginBatchNotify() if
+  //     BeginTransaction() succeeded.
+  return rv;
+}
+
+NS_IMETHODIMP
+nsTransactionManager::EndBatch(bool aAllowEmpty)
+{
+  // XXX: Need to add some mechanism to detect the case where the transaction
+  //      at the top of the do stack isn't the dummy transaction, so we can
+  //      throw an error!! This can happen if someone calls EndBatch() within
+  //      the DoTransaction() method of a transaction.
+  //
+  //      For now, we can detect this case by checking the value of the
+  //      dummy transaction's mTransaction field. If it is our dummy
+  //      transaction, it should be nullptr. This may not be true in the
+  //      future when we allow users to execute a transaction when beginning
+  //      a batch!!!!
+  RefPtr<nsTransactionItem> tx = mDoStack.Peek();
+  nsCOMPtr<nsITransaction> ti;
+  if (tx) {
+    ti = tx->GetTransaction();
+  }
+  if (!tx || ti) {
+    return NS_ERROR_FAILURE;
+  }
+
+  bool doInterrupt = false;
+  nsresult rv = WillEndBatchNotify(&doInterrupt);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  if (doInterrupt) {
+    return NS_OK;
+  }
+
+  rv = EndTransaction(aAllowEmpty);
+  nsresult rv2 = DidEndBatchNotify(rv);
+  if (NS_SUCCEEDED(rv)) {
+    rv = rv2;
+  }
+
+  // XXX The result of EndTransaction() or DidEndBatchNotify() if
+  //     EndTransaction() succeeded.
+  return rv;
+}
+
+NS_IMETHODIMP
+nsTransactionManager::GetNumberOfUndoItems(int32_t *aNumItems)
+{
+  *aNumItems = mUndoStack.GetSize();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsTransactionManager::GetNumberOfRedoItems(int32_t *aNumItems)
+{
+  *aNumItems = mRedoStack.GetSize();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsTransactionManager::GetMaxTransactionCount(int32_t *aMaxCount)
+{
+  NS_ENSURE_TRUE(aMaxCount, NS_ERROR_NULL_POINTER);
+  *aMaxCount = mMaxTransactionCount;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsTransactionManager::SetMaxTransactionCount(int32_t aMaxCount)
+{
+  // It is illegal to call SetMaxTransactionCount() while the transaction
+  // manager is executing a  transaction's DoTransaction() method because
+  // the undo and redo stacks might get pruned! If this happens, the
+  // SetMaxTransactionCount() request is ignored, and we return
+  // NS_ERROR_FAILURE.
+  if (!mDoStack.IsEmpty()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // If aMaxCount is less than zero, the user wants unlimited
+  // levels of undo! No need to prune the undo or redo stacks!
+  if (aMaxCount < 0) {
+    mMaxTransactionCount = -1;
+    return NS_OK;
+  }
+
+  // If aMaxCount is greater than the number of transactions that currently
+  // exist on the undo and redo stack, there is no need to prune the
+  // undo or redo stacks!
+  int32_t numUndoItems = mUndoStack.GetSize();
+  int32_t numRedoItems = mRedoStack.GetSize();
+  int32_t total = numUndoItems + numRedoItems;
+  if (aMaxCount > total) {
+    mMaxTransactionCount = aMaxCount;
+    return NS_OK;
+  }
+
+  // Try getting rid of some transactions on the undo stack! Start at
+  // the bottom of the stack and pop towards the top.
+  while (numUndoItems > 0 && (numRedoItems + numUndoItems) > aMaxCount) {
+    RefPtr<nsTransactionItem> tx = mUndoStack.PopBottom();
+    if (!tx) {
+      return NS_ERROR_FAILURE;
+    }
+    --numUndoItems;
+  }
+
+  // If necessary, get rid of some transactions on the redo stack! Start at
+  // the bottom of the stack and pop towards the top.
+  while (numRedoItems > 0 && (numRedoItems + numUndoItems) > aMaxCount) {
+    RefPtr<nsTransactionItem> tx = mRedoStack.PopBottom();
+    if (!tx) {
+      return NS_ERROR_FAILURE;
+    }
+    --numRedoItems;
+  }
+
+  mMaxTransactionCount = aMaxCount;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsTransactionManager::PeekUndoStack(nsITransaction **aTransaction)
+{
+  MOZ_ASSERT(aTransaction);
+  *aTransaction = PeekUndoStack().take();
+  return NS_OK;
+}
+
+already_AddRefed<nsITransaction>
+nsTransactionManager::PeekUndoStack()
+{
+  RefPtr<nsTransactionItem> tx = mUndoStack.Peek();
+  if (!tx) {
+    return nullptr;
+  }
+  return tx->GetTransaction();
+}
+
+NS_IMETHODIMP
+nsTransactionManager::PeekRedoStack(nsITransaction** aTransaction)
+{
+  MOZ_ASSERT(aTransaction);
+  *aTransaction = PeekRedoStack().take();
+  return NS_OK;
+}
+
+already_AddRefed<nsITransaction>
+nsTransactionManager::PeekRedoStack()
+{
+  RefPtr<nsTransactionItem> tx = mRedoStack.Peek();
+  if (!tx) {
+    return nullptr;
+  }
+  return tx->GetTransaction();
+}
+
+NS_IMETHODIMP
+nsTransactionManager::GetUndoList(nsITransactionList **aTransactionList)
+{
+  NS_ENSURE_TRUE(aTransactionList, NS_ERROR_NULL_POINTER);
+
+  *aTransactionList = (nsITransactionList *)new nsTransactionList(this, &mUndoStack);
+  NS_IF_ADDREF(*aTransactionList);
+  return (! *aTransactionList) ? NS_ERROR_OUT_OF_MEMORY : NS_OK;
+}
+
+NS_IMETHODIMP
+nsTransactionManager::GetRedoList(nsITransactionList **aTransactionList)
+{
+  NS_ENSURE_TRUE(aTransactionList, NS_ERROR_NULL_POINTER);
+
+  *aTransactionList = (nsITransactionList *)new nsTransactionList(this, &mRedoStack);
+  NS_IF_ADDREF(*aTransactionList);
+  return (! *aTransactionList) ? NS_ERROR_OUT_OF_MEMORY : NS_OK;
+}
+
+nsresult
+nsTransactionManager::BatchTopUndo()
+{
+  if (mUndoStack.GetSize() < 2) {
+    // Not enough transactions to merge into one batch.
+    return NS_OK;
+  }
+
+  RefPtr<nsTransactionItem> lastUndo;
+  RefPtr<nsTransactionItem> previousUndo;
+
+  lastUndo = mUndoStack.Pop();
+  MOZ_ASSERT(lastUndo, "There should be at least two transactions.");
+
+  previousUndo = mUndoStack.Peek();
+  MOZ_ASSERT(previousUndo, "There should be at least two transactions.");
+
+  nsresult rv = previousUndo->AddChild(lastUndo);
+
+  // Transfer data from the transactions that is going to be
+  // merged to the transaction that it is being merged with.
+  nsCOMArray<nsISupports>& lastData = lastUndo->GetData();
+  nsCOMArray<nsISupports>& previousData = previousUndo->GetData();
+  NS_ENSURE_TRUE(previousData.AppendObjects(lastData), NS_ERROR_UNEXPECTED);
+  lastData.Clear();
+  return rv;
+}
+
+nsresult
+nsTransactionManager::RemoveTopUndo()
+{
+  if (mUndoStack.IsEmpty()) {
+    return NS_OK;
+  }
+
+  RefPtr<nsTransactionItem> lastUndo = mUndoStack.Pop();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsTransactionManager::AddListener(nsITransactionListener *aListener)
+{
+  NS_ENSURE_TRUE(aListener, NS_ERROR_NULL_POINTER);
+  return mListeners.AppendObject(aListener) ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsTransactionManager::RemoveListener(nsITransactionListener *aListener)
+{
+  NS_ENSURE_TRUE(aListener, NS_ERROR_NULL_POINTER);
+  return mListeners.RemoveObject(aListener) ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsTransactionManager::ClearUndoStack()
+{
+  mUndoStack.Clear();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsTransactionManager::ClearRedoStack()
+{
+  mRedoStack.Clear();
+  return NS_OK;
+}
+
+nsresult
+nsTransactionManager::WillDoNotify(nsITransaction *aTransaction, bool *aInterrupt)
+{
+  for (int32_t i = 0, lcount = mListeners.Count(); i < lcount; i++) {
+    nsITransactionListener* listener = mListeners[i];
+    NS_ENSURE_TRUE(listener, NS_ERROR_FAILURE);
+
+    nsresult rv = listener->WillDo(this, aTransaction, aInterrupt);
+    if (NS_FAILED(rv) || *aInterrupt) {
+      return rv;
+    }
+  }
+  return NS_OK;
+}
+
+nsresult
+nsTransactionManager::DidDoNotify(nsITransaction *aTransaction, nsresult aDoResult)
+{
+  for (int32_t i = 0, lcount = mListeners.Count(); i < lcount; i++) {
+    nsITransactionListener* listener = mListeners[i];
+    NS_ENSURE_TRUE(listener, NS_ERROR_FAILURE);
+
+    nsresult rv = listener->DidDo(this, aTransaction, aDoResult);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+  }
+  return NS_OK;
+}
+
+nsresult
+nsTransactionManager::WillUndoNotify(nsITransaction *aTransaction, bool *aInterrupt)
+{
+  for (int32_t i = 0, lcount = mListeners.Count(); i < lcount; i++) {
+    nsITransactionListener* listener = mListeners[i];
+    NS_ENSURE_TRUE(listener, NS_ERROR_FAILURE);
+
+    nsresult rv = listener->WillUndo(this, aTransaction, aInterrupt);
+    if (NS_FAILED(rv) || *aInterrupt) {
+      return rv;
+    }
+  }
+  return NS_OK;
+}
+
+nsresult
+nsTransactionManager::DidUndoNotify(nsITransaction *aTransaction, nsresult aUndoResult)
+{
+  for (int32_t i = 0, lcount = mListeners.Count(); i < lcount; i++) {
+    nsITransactionListener* listener = mListeners[i];
+    NS_ENSURE_TRUE(listener, NS_ERROR_FAILURE);
+
+    nsresult rv = listener->DidUndo(this, aTransaction, aUndoResult);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+  }
+  return NS_OK;
+}
+
+nsresult
+nsTransactionManager::WillRedoNotify(nsITransaction *aTransaction, bool *aInterrupt)
+{
+  for (int32_t i = 0, lcount = mListeners.Count(); i < lcount; i++) {
+    nsITransactionListener* listener = mListeners[i];
+    NS_ENSURE_TRUE(listener, NS_ERROR_FAILURE);
+
+    nsresult rv = listener->WillRedo(this, aTransaction, aInterrupt);
+    if (NS_FAILED(rv) || *aInterrupt) {
+      return rv;
+    }
+  }
+  return NS_OK;
+}
+
+nsresult
+nsTransactionManager::DidRedoNotify(nsITransaction *aTransaction, nsresult aRedoResult)
+{
+  for (int32_t i = 0, lcount = mListeners.Count(); i < lcount; i++) {
+    nsITransactionListener* listener = mListeners[i];
+    NS_ENSURE_TRUE(listener, NS_ERROR_FAILURE);
+
+    nsresult rv = listener->DidRedo(this, aTransaction, aRedoResult);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+  }
+  return NS_OK;
+}
+
+nsresult
+nsTransactionManager::WillBeginBatchNotify(bool *aInterrupt)
+{
+  for (int32_t i = 0, lcount = mListeners.Count(); i < lcount; i++) {
+    nsITransactionListener* listener = mListeners[i];
+    NS_ENSURE_TRUE(listener, NS_ERROR_FAILURE);
+
+    nsresult rv = listener->WillBeginBatch(this, aInterrupt);
+    if (NS_FAILED(rv) || *aInterrupt) {
+      return rv;
+    }
+  }
+  return NS_OK;
+}
+
+nsresult
+nsTransactionManager::DidBeginBatchNotify(nsresult aResult)
+{
+  for (int32_t i = 0, lcount = mListeners.Count(); i < lcount; i++) {
+    nsITransactionListener* listener = mListeners[i];
+    NS_ENSURE_TRUE(listener, NS_ERROR_FAILURE);
+
+    nsresult rv = listener->DidBeginBatch(this, aResult);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+  }
+  return NS_OK;
+}
+
+nsresult
+nsTransactionManager::WillEndBatchNotify(bool *aInterrupt)
+{
+  for (int32_t i = 0, lcount = mListeners.Count(); i < lcount; i++) {
+    nsITransactionListener* listener = mListeners[i];
+    NS_ENSURE_TRUE(listener, NS_ERROR_FAILURE);
+
+    nsresult rv = listener->WillEndBatch(this, aInterrupt);
+    if (NS_FAILED(rv) || *aInterrupt) {
+      return rv;
+    }
+  }
+  return NS_OK;
+}
+
+nsresult
+nsTransactionManager::DidEndBatchNotify(nsresult aResult)
+{
+  for (int32_t i = 0, lcount = mListeners.Count(); i < lcount; i++) {
+    nsITransactionListener* listener = mListeners[i];
+    NS_ENSURE_TRUE(listener, NS_ERROR_FAILURE);
+
+    nsresult rv = listener->DidEndBatch(this, aResult);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+  }
+  return NS_OK;
+}
+
+nsresult
+nsTransactionManager::WillMergeNotify(nsITransaction *aTop, nsITransaction *aTransaction, bool *aInterrupt)
+{
+  for (int32_t i = 0, lcount = mListeners.Count(); i < lcount; i++) {
+    nsITransactionListener* listener = mListeners[i];
+    NS_ENSURE_TRUE(listener, NS_ERROR_FAILURE);
+
+    nsresult rv = listener->WillMerge(this, aTop, aTransaction, aInterrupt);
+    if (NS_FAILED(rv) || *aInterrupt) {
+      return rv;
+    }
+  }
+  return NS_OK;
+}
+
+nsresult
+nsTransactionManager::DidMergeNotify(nsITransaction *aTop,
+                                     nsITransaction *aTransaction,
+                                     bool aDidMerge,
+                                     nsresult aMergeResult)
+{
+  for (int32_t i = 0, lcount = mListeners.Count(); i < lcount; i++) {
+    nsITransactionListener* listener = mListeners[i];
+    NS_ENSURE_TRUE(listener, NS_ERROR_FAILURE);
+
+    nsresult rv =
+      listener->DidMerge(this, aTop, aTransaction, aDidMerge, aMergeResult);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+  }
+  return NS_OK;
+}
+
+nsresult
+nsTransactionManager::BeginTransaction(nsITransaction *aTransaction,
+                                       nsISupports *aData)
+{
+  // XXX: POSSIBLE OPTIMIZATION
+  //      We could use a factory that pre-allocates/recycles transaction items.
+  RefPtr<nsTransactionItem> tx = new nsTransactionItem(aTransaction);
+  if (!tx) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  if (aData) {
+    nsCOMArray<nsISupports>& data = tx->GetData();
+    data.AppendObject(aData);
+  }
+
+  mDoStack.Push(tx);
+
+  nsresult rv = tx->DoTransaction();
+  if (NS_FAILED(rv)) {
+    tx = mDoStack.Pop();
+    return rv;
+  }
+  return NS_OK;
+}
+
+nsresult
+nsTransactionManager::EndTransaction(bool aAllowEmpty)
+{
+  RefPtr<nsTransactionItem> tx = mDoStack.Pop();
+  if (!tx) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsITransaction> tint = tx->GetTransaction();
+  if (!tint && !aAllowEmpty) {
+    // If we get here, the transaction must be a dummy batch transaction
+    // created by BeginBatch(). If it contains no children, get rid of it!
+    int32_t nc = 0;
+    tx->GetNumberOfChildren(&nc);
+    if (!nc) {
+      return NS_OK;
+    }
+  }
+
+  // Check if the transaction is transient. If it is, there's nothing
+  // more to do, just return.
+  bool isTransient = false;
+  nsresult rv = NS_OK;
+  if (tint) {
+    rv = tint->GetIsTransient(&isTransient);
+  }
+  if (NS_FAILED(rv) || isTransient || !mMaxTransactionCount) {
+    // XXX: Should we be clearing the redo stack if the transaction
+    //      is transient and there is nothing on the do stack?
+    return rv;
+  }
+
+  // Check if there is a transaction on the do stack. If there is,
+  // the current transaction is a "sub" transaction, and should
+  // be added to the transaction at the top of the do stack.
+  RefPtr<nsTransactionItem> top = mDoStack.Peek();
+  if (top) {
+    return top->AddChild(tx); // XXX: What do we do if this fails?
+  }
+
+  // The transaction succeeded, so clear the redo stack.
+  rv = ClearRedoStack();
+  if (NS_FAILED(rv)) {
+    // XXX: What do we do if this fails?
+  }
+
+  // Check if we can coalesce this transaction with the one at the top
+  // of the undo stack.
+  top = mUndoStack.Peek();
+  if (tint && top) {
+    bool didMerge = false;
+    nsCOMPtr<nsITransaction> topTransaction = top->GetTransaction();
+    if (topTransaction) {
+      bool doInterrupt = false;
+      rv = WillMergeNotify(topTransaction, tint, &doInterrupt);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      if (!doInterrupt) {
+        rv = topTransaction->Merge(tint, &didMerge);
+        nsresult rv2 = DidMergeNotify(topTransaction, tint, didMerge, rv);
+        if (NS_SUCCEEDED(rv)) {
+          rv = rv2;
+        }
+        if (NS_FAILED(rv)) {
+          // XXX: What do we do if this fails?
+        }
+        if (didMerge) {
+          return rv;
+        }
+      }
+    }
+  }
+
+  // Check to see if we've hit the max level of undo. If so,
+  // pop the bottom transaction off the undo stack and release it!
+  int32_t sz = mUndoStack.GetSize();
+  if (mMaxTransactionCount > 0 && sz >= mMaxTransactionCount) {
+    RefPtr<nsTransactionItem> overflow = mUndoStack.PopBottom();
+  }
+
+  // Push the transaction on the undo stack:
+  mUndoStack.Push(tx.forget());
+  return NS_OK;
+}