diff -r 000000000000 -r 6474c204b198 editor/libeditor/base/DeleteTextTxn.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/editor/libeditor/base/DeleteTextTxn.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,115 @@
+/* -*- 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 "DeleteTextTxn.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/dom/Selection.h"
+#include "nsAutoPtr.h"
+#include "nsDebug.h"
+#include "nsEditor.h"
+#include "nsError.h"
+#include "nsIEditor.h"
+#include "nsISelection.h"
+#include "nsISupportsImpl.h"
+#include "nsSelectionState.h"
+#include "nsAString.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+DeleteTextTxn::DeleteTextTxn() :
+  EditTxn(),
+  mEditor(nullptr),
+  mCharData(),
+  mOffset(0),
+  mNumCharsToDelete(0),
+  mRangeUpdater(nullptr)
+{
+}
+
+NS_IMPL_CYCLE_COLLECTION_INHERITED(DeleteTextTxn, EditTxn,
+                                   mCharData)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(DeleteTextTxn)
+NS_INTERFACE_MAP_END_INHERITING(EditTxn)
+
+NS_IMETHODIMP
+DeleteTextTxn::Init(nsEditor* aEditor,
+                    nsIDOMCharacterData* aCharData,
+                    uint32_t aOffset,
+                    uint32_t aNumCharsToDelete,
+                    nsRangeUpdater* aRangeUpdater)
+{
+  MOZ_ASSERT(aEditor && aCharData);
+
+  mEditor = aEditor;
+  mCharData = aCharData;
+
+  // do nothing if the node is read-only
+  if (!mEditor->IsModifiableNode(mCharData)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  mOffset = aOffset;
+  mNumCharsToDelete = aNumCharsToDelete;
+#ifdef DEBUG
+  uint32_t length;
+  mCharData->GetLength(&length);
+  NS_ASSERTION(length >= aOffset + aNumCharsToDelete,
+               "Trying to delete more characters than in node");
+#endif
+  mDeletedText.Truncate();
+  mRangeUpdater = aRangeUpdater;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DeleteTextTxn::DoTransaction()
+{
+  MOZ_ASSERT(mEditor && mCharData);
+
+  // get the text that we're about to delete
+  nsresult res = mCharData->SubstringData(mOffset, mNumCharsToDelete,
+                                          mDeletedText);
+  MOZ_ASSERT(NS_SUCCEEDED(res));
+  res = mCharData->DeleteData(mOffset, mNumCharsToDelete);
+  NS_ENSURE_SUCCESS(res, res);
+
+  if (mRangeUpdater) {
+    mRangeUpdater->SelAdjDeleteText(mCharData, mOffset, mNumCharsToDelete);
+  }
+
+  // only set selection to deletion point if editor gives permission
+  bool bAdjustSelection;
+  mEditor->ShouldTxnSetSelection(&bAdjustSelection);
+  if (bAdjustSelection) {
+    nsRefPtr<Selection> selection = mEditor->GetSelection();
+    NS_ENSURE_TRUE(selection, NS_ERROR_NULL_POINTER);
+    res = selection->Collapse(mCharData, mOffset);
+    NS_ASSERTION(NS_SUCCEEDED(res),
+                 "selection could not be collapsed after undo of deletetext.");
+    NS_ENSURE_SUCCESS(res, res);
+  }
+  // else do nothing - dom range gravity will adjust selection
+  return NS_OK;
+}
+
+//XXX: we may want to store the selection state and restore it properly
+//     was it an insertion point or an extended selection?
+NS_IMETHODIMP
+DeleteTextTxn::UndoTransaction()
+{
+  MOZ_ASSERT(mEditor && mCharData);
+
+  return mCharData->InsertData(mOffset, mDeletedText);
+}
+
+NS_IMETHODIMP
+DeleteTextTxn::GetTxnDescription(nsAString& aString)
+{
+  aString.AssignLiteral("DeleteTextTxn: ");
+  aString += mDeletedText;
+  return NS_OK;
+}