diff --git a/common/rfb/ComparingUpdateTracker.h b/common/rfb/ComparingUpdateTracker.h
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+++ b/common/rfb/ComparingUpdateTracker.h
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+/* Copyright (C) 2002-2005 RealVNC Ltd.  All Rights Reserved.
+ * 
+ * This is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ * 
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this software; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
+ * USA.
+ */
+
+#ifndef __RFB_COMPARINGUPDATETRACKER_H__
+#define __RFB_COMPARINGUPDATETRACKER_H__
+
+#include <rfb/UpdateTracker.h>
+
+namespace rfb {
+
+  class ComparingUpdateTracker : public SimpleUpdateTracker {
+  public:
+    ComparingUpdateTracker(PixelBuffer* buffer);
+    ~ComparingUpdateTracker();
+
+    // compare() does the comparison and reduces its changed and copied regions
+    // as appropriate.
+
+    virtual void compare();
+  private:
+    void compareRect(const Rect& r, Region* newchanged);
+    PixelBuffer* fb;
+    ManagedPixelBuffer oldFb;
+    bool firstCompare;
+  };
+
+}
+#endif