diff -r 000000000000 -r 6474c204b198 editor/libeditor/base/SplitElementTxn.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/editor/libeditor/base/SplitElementTxn.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,157 @@
+/* -*- 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 <stdio.h>                      // for printf
+
+#include "SplitElementTxn.h"
+#include "nsAString.h"
+#include "nsDebug.h"                    // for NS_ASSERTION, etc
+#include "nsEditor.h"                   // for nsEditor
+#include "nsError.h"                    // for NS_ERROR_NOT_INITIALIZED, etc
+#include "nsIDOMCharacterData.h"        // for nsIDOMCharacterData
+#include "nsIDOMNode.h"                 // for nsIDOMNode
+#include "nsIEditor.h"                  // for nsEditor::DebugDumpContent, etc
+#include "nsISelection.h"               // for nsISelection
+#include "nsISupportsUtils.h"           // for NS_ADDREF
+
+// note that aEditor is not refcounted
+SplitElementTxn::SplitElementTxn()
+  : EditTxn()
+{
+}
+
+NS_IMPL_CYCLE_COLLECTION_INHERITED(SplitElementTxn, EditTxn,
+                                   mParent,
+                                   mNewLeftNode)
+
+NS_IMPL_ADDREF_INHERITED(SplitElementTxn, EditTxn)
+NS_IMPL_RELEASE_INHERITED(SplitElementTxn, EditTxn)
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(SplitElementTxn)
+NS_INTERFACE_MAP_END_INHERITING(EditTxn)
+
+NS_IMETHODIMP SplitElementTxn::Init(nsEditor   *aEditor,
+                                    nsIDOMNode *aNode,
+                                    int32_t     aOffset)
+{
+  NS_ASSERTION(aEditor && aNode, "bad args");
+  if (!aEditor || !aNode) { return NS_ERROR_NOT_INITIALIZED; }
+
+  mEditor = aEditor;
+  mExistingRightNode = do_QueryInterface(aNode);
+  mOffset = aOffset;
+  return NS_OK;
+}
+
+NS_IMETHODIMP SplitElementTxn::DoTransaction(void)
+{
+  NS_ASSERTION(mExistingRightNode && mEditor, "bad state");
+  if (!mExistingRightNode || !mEditor) { return NS_ERROR_NOT_INITIALIZED; }
+
+  // create a new node
+  nsresult result = mExistingRightNode->CloneNode(false, 1, getter_AddRefs(mNewLeftNode));
+  NS_ASSERTION(((NS_SUCCEEDED(result)) && (mNewLeftNode)), "could not create element.");
+  NS_ENSURE_SUCCESS(result, result);
+  NS_ENSURE_TRUE(mNewLeftNode, NS_ERROR_NULL_POINTER);
+  mEditor->MarkNodeDirty(mExistingRightNode);
+
+  // get the parent node
+  result = mExistingRightNode->GetParentNode(getter_AddRefs(mParent));
+  NS_ENSURE_SUCCESS(result, result);
+  NS_ENSURE_TRUE(mParent, NS_ERROR_NULL_POINTER);
+
+  // insert the new node
+  result = mEditor->SplitNodeImpl(mExistingRightNode, mOffset, mNewLeftNode, mParent);
+  if (mNewLeftNode) {
+    bool bAdjustSelection;
+    mEditor->ShouldTxnSetSelection(&bAdjustSelection);
+    if (bAdjustSelection)
+    {
+      nsCOMPtr<nsISelection> selection;
+      result = mEditor->GetSelection(getter_AddRefs(selection));
+      NS_ENSURE_SUCCESS(result, result);
+      NS_ENSURE_TRUE(selection, NS_ERROR_NULL_POINTER);
+      result = selection->Collapse(mNewLeftNode, mOffset);
+    }
+    else
+    {
+      // do nothing - dom range gravity will adjust selection
+    }
+  }
+  return result;
+}
+
+NS_IMETHODIMP SplitElementTxn::UndoTransaction(void)
+{
+  NS_ASSERTION(mEditor && mExistingRightNode && mNewLeftNode && mParent, "bad state");
+  if (!mEditor || !mExistingRightNode || !mNewLeftNode || !mParent) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  // this assumes Do inserted the new node in front of the prior existing node
+  nsCOMPtr<nsINode> rightNode = do_QueryInterface(mExistingRightNode);
+  nsCOMPtr<nsINode> leftNode = do_QueryInterface(mNewLeftNode);
+  nsCOMPtr<nsINode> parent = do_QueryInterface(mParent);
+  NS_ENSURE_TRUE(rightNode && leftNode && parent, NS_ERROR_FAILURE);
+  return mEditor->JoinNodesImpl(rightNode, leftNode, parent);
+}
+
+/* redo cannot simply resplit the right node, because subsequent transactions
+ * on the redo stack may depend on the left node existing in its previous state.
+ */
+NS_IMETHODIMP SplitElementTxn::RedoTransaction(void)
+{
+  NS_ASSERTION(mEditor && mExistingRightNode && mNewLeftNode && mParent, "bad state");
+  if (!mEditor || !mExistingRightNode || !mNewLeftNode || !mParent) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  nsresult result;
+  nsCOMPtr<nsIDOMNode>resultNode;
+  // first, massage the existing node so it is in its post-split state
+  nsCOMPtr<nsIDOMCharacterData>rightNodeAsText = do_QueryInterface(mExistingRightNode);
+  if (rightNodeAsText)
+  {
+    nsresult result = rightNodeAsText->DeleteData(0, mOffset);
+    NS_ENSURE_SUCCESS(result, result);
+  }
+  else
+  {
+    nsCOMPtr<nsIDOMNode>child;
+    nsCOMPtr<nsIDOMNode>nextSibling;
+    result = mExistingRightNode->GetFirstChild(getter_AddRefs(child));
+    int32_t i;
+    for (i=0; i<mOffset; i++)
+    {
+      if (NS_FAILED(result)) {return result;}
+      if (!child) {return NS_ERROR_NULL_POINTER;}
+      child->GetNextSibling(getter_AddRefs(nextSibling));
+      result = mExistingRightNode->RemoveChild(child, getter_AddRefs(resultNode));
+      if (NS_SUCCEEDED(result)) 
+      {
+        result = mNewLeftNode->AppendChild(child, getter_AddRefs(resultNode));
+      }
+      child = do_QueryInterface(nextSibling);
+    }
+  }
+  // second, re-insert the left node into the tree 
+  result = mParent->InsertBefore(mNewLeftNode, mExistingRightNode, getter_AddRefs(resultNode));
+  return result;
+}
+
+
+NS_IMETHODIMP SplitElementTxn::GetTxnDescription(nsAString& aString)
+{
+  aString.AssignLiteral("SplitElementTxn");
+  return NS_OK;
+}
+
+NS_IMETHODIMP SplitElementTxn::GetNewNode(nsIDOMNode **aNewNode)
+{
+  NS_ENSURE_TRUE(aNewNode, NS_ERROR_NULL_POINTER);
+  NS_ENSURE_TRUE(mNewLeftNode, NS_ERROR_NOT_INITIALIZED);
+  *aNewNode = mNewLeftNode;
+  NS_ADDREF(*aNewNode);
+  return NS_OK;
+}