diff -r 000000000000 -r 6474c204b198 editor/libeditor/base/ChangeAttributeTxn.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/editor/libeditor/base/ChangeAttributeTxn.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,105 @@
+/* -*- 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 "ChangeAttributeTxn.h"
+#include "nsAString.h"
+#include "nsDebug.h"                    // for NS_ASSERTION
+#include "nsError.h"                    // for NS_ERROR_NOT_INITIALIZED, etc
+#include "nsIDOMElement.h"              // for nsIDOMElement
+#include "nsIEditor.h"                  // for nsIEditor
+#include "nsString.h"                   // for nsString
+
+ChangeAttributeTxn::ChangeAttributeTxn()
+  : EditTxn()
+{
+}
+
+NS_IMPL_CYCLE_COLLECTION_INHERITED(ChangeAttributeTxn, EditTxn,
+                                   mElement)
+
+NS_IMPL_ADDREF_INHERITED(ChangeAttributeTxn, EditTxn)
+NS_IMPL_RELEASE_INHERITED(ChangeAttributeTxn, EditTxn)
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ChangeAttributeTxn)
+NS_INTERFACE_MAP_END_INHERITING(EditTxn)
+
+NS_IMETHODIMP ChangeAttributeTxn::Init(nsIEditor      *aEditor,
+                                       nsIDOMElement  *aElement,
+                                       const nsAString& aAttribute,
+                                       const nsAString& aValue,
+                                       bool aRemoveAttribute)
+{
+  NS_ASSERTION(aEditor && aElement, "bad arg");
+  if (!aEditor || !aElement) { return NS_ERROR_NULL_POINTER; }
+
+  mEditor = aEditor;
+  mElement = do_QueryInterface(aElement);
+  mAttribute = aAttribute;
+  mValue = aValue;
+  mRemoveAttribute = aRemoveAttribute;
+  mAttributeWasSet=false;
+  mUndoValue.Truncate();
+  return NS_OK;
+}
+
+NS_IMETHODIMP ChangeAttributeTxn::DoTransaction(void)
+{
+  NS_ASSERTION(mEditor && mElement, "bad state");
+  if (!mEditor || !mElement) { return NS_ERROR_NOT_INITIALIZED; }
+
+  // need to get the current value of the attribute and save it, and set mAttributeWasSet
+  nsresult result = mEditor->GetAttributeValue(mElement, mAttribute, mUndoValue, &mAttributeWasSet);
+  // XXX: hack until attribute-was-set code is implemented
+  if (!mUndoValue.IsEmpty())
+    mAttributeWasSet = true;
+  // XXX: end hack
+  
+  // now set the attribute to the new value
+  if (!mRemoveAttribute)
+    result = mElement->SetAttribute(mAttribute, mValue);
+  else
+    result = mElement->RemoveAttribute(mAttribute);
+
+  return result;
+}
+
+NS_IMETHODIMP ChangeAttributeTxn::UndoTransaction(void)
+{
+  NS_ASSERTION(mEditor && mElement, "bad state");
+  if (!mEditor || !mElement) { return NS_ERROR_NOT_INITIALIZED; }
+
+  nsresult result;
+  if (mAttributeWasSet)
+    result = mElement->SetAttribute(mAttribute, mUndoValue);
+  else
+    result = mElement->RemoveAttribute(mAttribute);
+
+  return result;
+}
+
+NS_IMETHODIMP ChangeAttributeTxn::RedoTransaction(void)
+{
+  NS_ASSERTION(mEditor && mElement, "bad state");
+  if (!mEditor || !mElement) { return NS_ERROR_NOT_INITIALIZED; }
+
+  nsresult result;
+  if (!mRemoveAttribute)
+    result = mElement->SetAttribute(mAttribute, mValue);
+  else
+    result = mElement->RemoveAttribute(mAttribute);
+
+  return result;
+}
+
+NS_IMETHODIMP ChangeAttributeTxn::GetTxnDescription(nsAString& aString)
+{
+  aString.AssignLiteral("ChangeAttributeTxn: [mRemoveAttribute == ");
+
+  if (!mRemoveAttribute)
+    aString.AppendLiteral("false] ");
+  else
+    aString.AppendLiteral("true] ");
+  aString += mAttribute;
+  return NS_OK;
+}