diff --git a/src/digest-tree-scene.h b/src/digest-tree-scene.h
new file mode 100644
index 0000000..6ac6b1c
--- /dev/null
+++ b/src/digest-tree-scene.h
@@ -0,0 +1,124 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
+/*
+ * Copyright (c) 2013, Regents of the University of California
+ *                     Yingdi Yu
+ *
+ * BSD license, See the LICENSE file for more information
+ *
+ * Author: Zhenkai Zhu <zhenkai@cs.ucla.edu>
+ *         Alexander Afanasyev <alexander.afanasyev@ucla.edu>
+ */
+
+#ifndef DIGEST_TREE_SCENE_H
+#define DIGEST_TREE_SCENE_H
+
+#include <QtGui/QGraphicsScene>
+#include <QColor>
+#include <QMap>
+
+#ifndef Q_MOC_RUN
+#include "tree-layout.h"
+#include <sync-seq-no.h>
+#include <sync-logic.h>
+#include <ctime>
+#include <vector>
+#include <boost/shared_ptr.hpp>
+#endif
+
+const int FRESHNESS = 60;
+
+class QGraphicsTextItem;
+
+class User;
+class DisplayUser;
+typedef boost::shared_ptr<DisplayUser> DisplayUserPtr;
+static DisplayUserPtr DisplayUserNullPtr;
+
+class DigestTreeScene : public QGraphicsScene
+{
+  Q_OBJECT
+
+typedef QMap<QString, DisplayUserPtr> Roster;
+typedef QMap<QString, DisplayUserPtr>::iterator Roster_iterator;
+typedef QMapIterator<QString, DisplayUserPtr> RosterIterator;
+
+public:
+  DigestTreeScene(QWidget *parent = 0);
+  void processUpdate(const std::vector<Sync::MissingDataInfo> &v, QString digest);
+  void msgReceived(QString prefix, QString nick);
+  void clearAll();
+  bool removeNode(const QString prefix);
+  void plot(QString digest);
+  QStringList getRosterList();
+  void setCurrentPrefix(QString prefix) {m_currentPrefix = prefix;}
+  QMap<QString, DisplayUserPtr> getRosterFull() { return m_roster;}
+
+signals:
+  void replot();
+  void rosterChanged(QStringList);
+
+private slots:
+  void emitReplot();
+
+private:
+  void plotEdge(const std::vector<TreeLayout::Coordinate> &v, int nodeSize);
+  void plotNode(const std::vector<TreeLayout::Coordinate> &v, QString digest, int nodeSize);
+  void reDrawNode(DisplayUserPtr p, QColor rimColor);
+
+private:
+  Roster m_roster;
+  QGraphicsTextItem *m_rootDigest; 
+  DisplayUserPtr previouslyUpdatedUser;
+  QString m_currentPrefix;
+};
+
+class User 
+{
+public:
+  User():m_received(time(NULL)) {}
+  User(QString n, QString p, QString c): m_nick(n), m_prefix(p), m_chatroom(c), m_received(time(NULL)) {}
+  void setNick(QString nick) {m_nick = nick;}
+  void setPrefix(QString prefix) {m_prefix = prefix;}
+  void setChatroom(QString chatroom) {m_chatroom = chatroom;}
+  void setSeq(Sync::SeqNo seq) {m_seq = seq;}
+  void setReceived(time_t t) {m_received = t;}
+  void setOriginPrefix(QString originPrefix) { m_originPrefix = originPrefix;}
+  QString getNick() { return m_nick;}
+  QString getPrefix() { return m_prefix;}
+  QString getChatroom() { return m_chatroom;}
+  QString getOriginPrefix() { return m_originPrefix;}
+  Sync::SeqNo getSeqNo() { return m_seq;}
+  time_t getReceived() { return m_received;}
+private:
+  QString m_nick;
+  QString m_prefix;
+  QString m_chatroom;
+  QString m_originPrefix;
+  Sync::SeqNo m_seq;
+  time_t m_received;
+};
+
+class DisplayUser : public User 
+{
+public:
+  DisplayUser():m_seqTextItem(NULL), m_nickTextItem(NULL), m_rimRectItem(NULL) {}
+  DisplayUser(QString n, QString p , QString c): User(n, p, c), m_seqTextItem(NULL), m_nickTextItem(NULL), m_rimRectItem(NULL) {}
+  QGraphicsTextItem *getSeqTextItem() {return m_seqTextItem;}
+  QGraphicsTextItem *getNickTextItem() {return m_nickTextItem;}
+  QGraphicsRectItem *getRimRectItem() {return m_rimRectItem;}
+  QGraphicsRectItem *getInnerRectItem() {return m_innerRectItem;}
+  QGraphicsRectItem *getNickRectItem() {return m_nickRectItem;}
+  void setSeqTextItem(QGraphicsTextItem *item) { m_seqTextItem = item;}
+  void setNickTextItem(QGraphicsTextItem *item) { m_nickTextItem = item;}
+  void setRimRectItem(QGraphicsRectItem *item) {m_rimRectItem = item;}
+  void setInnerRectItem(QGraphicsRectItem *item) {m_innerRectItem = item;}
+  void setNickRectItem(QGraphicsRectItem *item) {m_nickRectItem = item;}
+private:
+  QGraphicsTextItem *m_seqTextItem;
+  QGraphicsTextItem *m_nickTextItem;
+  QGraphicsRectItem *m_rimRectItem;
+  QGraphicsRectItem *m_innerRectItem;
+  QGraphicsRectItem *m_nickRectItem;
+};
+
+#endif // DIGEST_TREE_SCENE_H