diff -r 000000000000 -r 6474c204b198 editor/libeditor/text/nsTextEditRulesBidi.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/editor/libeditor/text/nsTextEditRulesBidi.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,83 @@
+/* -*- 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 "nsAutoPtr.h"
+#include "nsCOMPtr.h"
+#include "nsDebug.h"
+#include "nsError.h"
+#include "nsFrameSelection.h"
+#include "nsIContent.h"
+#include "nsIDOMNode.h"
+#include "nsIEditor.h"
+#include "nsIPresShell.h"
+#include "mozilla/dom/Selection.h"
+#include "nsISelectionPrivate.h"
+#include "nsISupportsImpl.h"
+#include "nsPlaintextEditor.h"
+#include "nsPresContext.h"
+#include "nsTextEditRules.h"
+#include "nscore.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+// Test for distance between caret and text that will be deleted
+nsresult
+nsTextEditRules::CheckBidiLevelForDeletion(nsISelection         *aSelection,
+                                           nsIDOMNode           *aSelNode, 
+                                           int32_t               aSelOffset, 
+                                           nsIEditor::EDirection aAction,
+                                           bool                 *aCancel)
+{
+  NS_ENSURE_ARG_POINTER(aCancel);
+  *aCancel = false;
+
+  nsCOMPtr<nsIPresShell> shell = mEditor->GetPresShell();
+  NS_ENSURE_TRUE(shell, NS_ERROR_NOT_INITIALIZED);
+  
+  nsPresContext *context = shell->GetPresContext();
+  NS_ENSURE_TRUE(context, NS_ERROR_NULL_POINTER);
+  
+  if (!context->BidiEnabled())
+    return NS_OK;
+  
+  nsCOMPtr<nsIContent> content = do_QueryInterface(aSelNode);
+  NS_ENSURE_TRUE(content, NS_ERROR_NULL_POINTER);
+
+  uint8_t levelBefore;
+  uint8_t levelAfter;
+  nsRefPtr<nsFrameSelection> frameSelection =
+    static_cast<Selection*>(aSelection)->GetFrameSelection();
+  NS_ENSURE_TRUE(frameSelection, NS_ERROR_NULL_POINTER);
+  
+  nsPrevNextBidiLevels levels = frameSelection->
+    GetPrevNextBidiLevels(content, aSelOffset, true);
+    
+  levelBefore = levels.mLevelBefore;
+  levelAfter = levels.mLevelAfter;
+
+  uint8_t currentCaretLevel = frameSelection->GetCaretBidiLevel();
+
+  uint8_t levelOfDeletion;
+  levelOfDeletion =
+    (nsIEditor::eNext==aAction || nsIEditor::eNextWord==aAction) ?
+    levelAfter : levelBefore;
+
+  if (currentCaretLevel == levelOfDeletion)
+    ; // perform the deletion
+  else
+  {
+    if (mDeleteBidiImmediately || levelBefore == levelAfter)
+      ; // perform the deletion
+    else
+      *aCancel = true;
+
+    // Set the bidi level of the caret to that of the
+    // character that will be (or would have been) deleted
+    frameSelection->SetCaretBidiLevel(levelOfDeletion);
+  }
+  return NS_OK;
+}
+