Changeset 10649 for branches/HeuristicLab.EvolutionTracking/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding.Views/3.4

Timestamp:

03/24/14 16:56:18 (10 years ago)

Author:

bburlacu

Message:

#1772: Merged trunk changes (related to the ReingoldTilfordLayoutEngine).

Location:

branches/HeuristicLab.EvolutionTracking/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding.Views

Files:

• . (modified) (1 prop)
• 3.4/Formatters/SymbolicExpressionTreeLatexFormatter.cs (modified) (3 diffs)
• 3.4/LayoutEngines/BoxesLayoutEngine.cs (modified) (2 diffs)
• 3.4/LayoutEngines/ILayoutEngine.cs (modified) (2 diffs)
• 3.4/LayoutEngines/LayoutNode.cs (modified) (1 diff)
• 3.4/LayoutEngines/ReingoldTilfordLayoutEngine.cs (modified) (9 diffs)
• 3.4/SymbolicExpressionGrammarAllowedChildSymbolsControl.cs (modified) (4 diffs)
• 3.4/SymbolicExpressionTreeChart.cs (modified) (16 diffs)

branches/HeuristicLab.EvolutionTracking/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding.Views/3.4/Formatters/SymbolicExpressionTreeLatexFormatter.cs

@@ -22 +22 @@
 using System;
 using System.Collections.Generic;
+using System.Drawing;
 using System.Globalization;
 using System.Linq;
@@ -36 +37 @@
       {"StartSymbol","RPB"}
     };
-    private readonly ReingoldTilfordLayoutEngine<ISymbolicExpressionTreeNode> layoutEngine = new ReingoldTilfordLayoutEngine<ISymbolicExpressionTreeNode>();
+
+    private readonly ReingoldTilfordLayoutEngine<ISymbolicExpressionTreeNode> layoutEngine;
 
     public SymbolicExpressionTreeLatexFormatter()
       : base("LaTeX/PDF Formatter", "Formatter for symbolic expression trees for use with latex package tikz.") {
-      layoutEngine = new ReingoldTilfordLayoutEngine<ISymbolicExpressionTreeNode> {
+      layoutEngine = new ReingoldTilfordLayoutEngine<ISymbolicExpressionTreeNode>(n => n.Subtrees) {
         HorizontalSpacing = 2,
         VerticalSpacing = 2,
@@ -57 +59 @@
 
     public string Format(ISymbolicExpressionTree symbolicExpressionTree) {
-      layoutEngine.Reset();
       var root = symbolicExpressionTree.Root;
       var actualRoot = root.SubtreeCount == 0 ? root.GetSubtree(0) : root;
-      layoutEngine.Initialize(actualRoot, x => x.Subtrees);
-      layoutEngine.CalculateLayout();
-      var nodeCoordinates = layoutEngine.GetCoordinates();
+      var nodeCoordinates = layoutEngine.CalculateLayout(actualRoot).ToDictionary(n => n.Content, n => new PointF(n.X, n.Y));
       var sb = new StringBuilder();
       var nl = Environment.NewLine;

branches/HeuristicLab.EvolutionTracking/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding.Views/3.4/LayoutEngines/BoxesLayoutEngine.cs

@@ -1 @@
-
+#region License Information
+
+/* HeuristicLab
+ * Copyright (C) 2002-2014 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
+ *
+ * This file is part of HeuristicLab.
+ *
+ * HeuristicLab 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 3 of the License, or
+ * (at your option) any later version.
+ *
+ * HeuristicLab 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 HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#endregion
+
 using System;
 using System.Collections.Generic;
-using System.Drawing;
 using System.Linq;
 
 namespace HeuristicLab.Encodings.SymbolicExpressionTreeEncoding.Views {
   public class BoxesLayoutEngine<T> : ILayoutEngine<T> where T : class {
-    private readonly Dictionary<T, VisualTreeNode<T>> nodeMap;
-
     public int NodeWidth { get; set; }
     public int NodeHeight { get; set; }
     public int HorizontalSpacing { get; set; }
     public int VerticalSpacing { get; set; }
-    private VisualTreeNode<T> layoutRoot;
 
-    public int Width { get; private set; }
-    public int Height { get; private set; }
+    private readonly Func<T, IEnumerable<T>> GetChildren;
+    private readonly Func<T, int> GetLength;
+    private readonly Func<T, int> GetDepth;
 
-    public Func<T, IEnumerable<T>> GetChildren { get; set; }
-    public Func<T, int> GetLength { get; set; }
-    public Func<T, int> GetDepth { get; set; }
+    public BoxesLayoutEngine(Func<T, IEnumerable<T>> GetChildren, Func<T, int> GetLength, Func<T, int> GetDepth) {
+      if (GetChildren == null) throw new ArgumentNullException("GetChildren");
+      if (GetLength == null) throw new ArgumentNullException("GetLength");
+      if (GetDepth == null) throw new ArgumentNullException("GetDepth");
 
-    public BoxesLayoutEngine() {
-      nodeMap = new Dictionary<T, VisualTreeNode<T>>();
+      this.GetChildren = GetChildren;
+      this.GetLength = GetLength;
+      this.GetDepth = GetDepth;
     }
 
-    public void CalculateLayout() {
-      throw new Exception("The BoxesLayoutEngine does not support arbitrary bounds. Please use method CalculateLayout(Width, Height)");
+
+    public IEnumerable<VisualTreeNode<T>> CalculateLayout(T root, float width, float height) {
+      var nodeMap = new Dictionary<T, VisualTreeNode<T>>();
+      CreateVisualNodes(root, nodeMap);
+      RecursiveLayout(nodeMap, nodeMap[root], 0, 0, (int)Math.Round(width), (int)Math.Round(height) / GetDepth(root));
+      return nodeMap.Values;
     }
 
-    public void CalculateLayout(float width, float height) {
-      Width = (int)Math.Round(width);
-      Height = (int)Math.Round(height);
-      Reset();
-      RecursiveLayout(layoutRoot, 0, 0, Width, Height / GetDepth(layoutRoot.Content));
-    }
-
-    public void Initialize(T root, Func<T, IEnumerable<T>> getChildren, Func<T, int> getLength, Func<T, int> getDepth) {
-      if (getChildren == null || getLength == null || getDepth == null)
-        throw new ArgumentNullException("The BoxesLayoutEngine requires all of the lambdas: (getChildren, getLength and getDepth) to be defined.");
-      GetChildren = getChildren;
-      GetLength = getLength;
-      GetDepth = getDepth;
-      Clear();
-      Expand(root); // produce the nodeMap
-      layoutRoot = nodeMap[root];
-    }
-
-    private void Expand(T root) {
+    private void CreateVisualNodes(T root, Dictionary<T, VisualTreeNode<T>> map) {
       var node = new VisualTreeNode<T>(root) {
         PreferredWidth = NodeWidth,
         PreferredHeight = NodeHeight
       };
-      nodeMap.Add(root, node);
+
+      map.Add(root, node);
       var children = GetChildren(root).ToList();
       if (children.Any()) {
         foreach (var child in children) {
-          Expand(child);
+          CreateVisualNodes(child, map);
         }
       }
     }
 
-    public void Center(float width, float height) {
-      // does nothing because the BoxesLayout centers the tree by default
-    }
-
-    public void Clear() {
-      nodeMap.Clear();
-      layoutRoot = null;
-    }
-
-    public void Reset() {
-      foreach (var node in nodeMap.Values) {
-        node.X = 0;
-        node.Y = 0;
-      }
-    }
-
-    public Dictionary<T, PointF> GetCoordinates() {
-      return nodeMap.ToDictionary(x => x.Key, x => new PointF(x.Value.X, x.Value.Y));
-    }
-
-    public void FitToBounds(float width, float height) {
-      // does nothing because the BoxesLayout is by default stretched on the whole drawing area
-    }
-
-    private void RecursiveLayout(VisualTreeNode<T> visualTreeNode, int x, int y, int width, int height) {
+    private void RecursiveLayout(Dictionary<T, VisualTreeNode<T>> nodeMap, VisualTreeNode<T> visualTreeNode, int x, int y, int width, int height) {
       float center_x = x + width / 2;
       float center_y = y + height / 2;
@@ -127 +111 @@
       for (int i = 0; i < children.Count; i++) {
         xBoundaries[i + 1] = (int)(xBoundaries[i] + (width * (double)GetLength(children[i])) / (GetLength(node) - 1));
-        RecursiveLayout(nodeMap[children[i]], xBoundaries[i], y + height, xBoundaries[i + 1] - xBoundaries[i], height);
+        RecursiveLayout(nodeMap, nodeMap[children[i]], xBoundaries[i], y + height, xBoundaries[i + 1] - xBoundaries[i], height);
       }
-    }
-
-    public IEnumerable<VisualTreeNode<T>> GetVisualNodes() {
-      return nodeMap.Values;
     }
   }

branches/HeuristicLab.EvolutionTracking/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding.Views/3.4/LayoutEngines/ILayoutEngine.cs

@@ -1 @@
-
-using System;
+#region License Information
+/* HeuristicLab
+ * Copyright (C) 2002-2014 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
+ *
+ * This file is part of HeuristicLab.
+ *
+ * HeuristicLab 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 3 of the License, or
+ * (at your option) any later version.
+ *
+ * HeuristicLab 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 HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#endregion
+
 using System.Collections.Generic;
-using System.Drawing;
 
 namespace HeuristicLab.Encodings.SymbolicExpressionTreeEncoding.Views {
@@ -11 +30 @@
     int VerticalSpacing { get; set; }
 
-    void CalculateLayout();
-    void CalculateLayout(float width, float height);
-    void Initialize(T root, Func<T, IEnumerable<T>> getChildren, Func<T, int> getLength = null, Func<T, int> getDepth = null);
-    void Clear();
-    void Reset();
-
-    // function members necessary to navigate the tree structure
-    Func<T, IEnumerable<T>> GetChildren { get; set; }
-    Func<T, int> GetLength { get; set; }
-    Func<T, int> GetDepth { get; set; }
-
-    IEnumerable<VisualTreeNode<T>> GetVisualNodes();
-    Dictionary<T, PointF> GetCoordinates();
+    IEnumerable<VisualTreeNode<T>> CalculateLayout(T root, float width, float height);
   }
 }

branches/HeuristicLab.EvolutionTracking/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding.Views/3.4/LayoutEngines/LayoutNode.cs

@@ -25 +25 @@
 
 namespace HeuristicLab.Encodings.SymbolicExpressionTreeEncoding.Views {
-  public class LayoutNode<T> : object where T : class {
+  internal class LayoutNode<T> : object where T : class {
     public float Width { get; set; }
     public float Height { get; set; }

branches/HeuristicLab.EvolutionTracking/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding.Views/3.4/LayoutEngines/ReingoldTilfordLayoutEngine.cs

@@ -1 @@
-
+#region License Information
+/* HeuristicLab
+ * Copyright (C) 2002-2014 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
+ *
+ * This file is part of HeuristicLab.
+ *
+ * HeuristicLab 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 3 of the License, or
+ * (at your option) any later version.
+ *
+ * HeuristicLab 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 HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
+ */
+#endregion
+
 using System;
 using System.Collections.Generic;
@@ -7 +27 @@
 namespace HeuristicLab.Encodings.SymbolicExpressionTreeEncoding.Views {
   public class ReingoldTilfordLayoutEngine<T> : ILayoutEngine<T> where T : class {
-    private readonly Dictionary<T, LayoutNode<T>> nodeMap; // provides a reverse mapping T => LayoutNode
     public int NodeWidth { get; set; }
     public int NodeHeight { get; set; }
@@ -22 +41 @@
     }
 
-    public Func<T, IEnumerable<T>> GetChildren { get; set; }
-    public Func<T, int> GetLength { get; set; }
-    public Func<T, int> GetDepth { get; set; }
-    private LayoutNode<T> layoutRoot;
-
-    public ReingoldTilfordLayoutEngine() {
-      nodeMap = new Dictionary<T, LayoutNode<T>>();
-    }
-
-    public ReingoldTilfordLayoutEngine(T root, Func<T, IEnumerable<T>> childrenFunc)
-      : this() {
-      Initialize(root, childrenFunc);
-    }
-
-    public void Initialize(T root, Func<T, IEnumerable<T>> getChildren, Func<T, int> getLength = null, Func<T, int> getDepth = null) {
-      GetChildren = getChildren;
-      Clear();
-      var node = new LayoutNode<T> { Content = root, Width = NodeWidth, Height = NodeHeight };
-      node.Ancestor = node;
-      layoutRoot = node;
-      Expand(node);
-    }
-
-    private void Expand(LayoutNode<T> lRoot) {
-      nodeMap.Add(lRoot.Content, lRoot);
+    private readonly Func<T, IEnumerable<T>> GetChildren;
+
+    public ReingoldTilfordLayoutEngine(Func<T, IEnumerable<T>> GetChildren) {
+      this.GetChildren = GetChildren;
+    }
+
+    public IEnumerable<VisualTreeNode<T>> CalculateLayout(T root) {
+      return CalculateLayout(root, 0, 0);
+    }
+
+    public IEnumerable<VisualTreeNode<T>> CalculateLayout(T root, float width, float height) {
+      Dictionary<T, LayoutNode<T>> layoutNodeMap = new Dictionary<T, LayoutNode<T>>();
+      var layoutRoot = new LayoutNode<T> { Content = root, Width = NodeWidth, Height = NodeHeight, };
+      layoutRoot.Ancestor = layoutRoot;
+      Expand(layoutRoot, layoutNodeMap);
+
+      FirstWalk(layoutRoot);
+      SecondWalk(layoutRoot, -layoutRoot.Prelim);
+      NormalizeCoordinates(layoutNodeMap.Values);
+      if (height != 0 && width != 0) {
+        FitToBounds(width, height, layoutNodeMap.Values);
+        Center(width, height, layoutNodeMap.Values);
+      }
+
+      return layoutNodeMap.Values.Select(x => new VisualTreeNode<T>(x.Content) {
+        Width = (int)Math.Round(x.Width),
+        Height = (int)Math.Round(x.Height),
+        X = (int)Math.Round(x.X),
+        Y = (int)Math.Round(x.Y)
+      });
+    }
+
+    private void Expand(LayoutNode<T> lRoot, Dictionary<T, LayoutNode<T>> map) {
+      map.Add(lRoot.Content, lRoot);
       var children = GetChildren(lRoot.Content).ToList();
       if (!children.Any()) return;
@@ -61 +89 @@
         node.Ancestor = node;
         lRoot.Children.Add(node);
-        Expand(node);
-      }
-    }
-
-    public IEnumerable<VisualTreeNode<T>> GetVisualNodes() {
-      return nodeMap.Values.Select(x => new VisualTreeNode<T>(x.Content) {
-        Width = (int)Math.Round(x.Width),
-        Height = (int)Math.Round(x.Height),
-        X = (int)Math.Round(x.X),
-        Y = (int)Math.Round(x.Y)
-      });
-    }
-
-    public void AddNode(T content) {
-      if (nodeMap.ContainsKey(content)) { throw new ArgumentException("Content already present in the dictionary."); }
-      var node = new LayoutNode<T> { Content = content };
-      nodeMap.Add(content, node);
-    }
-
-    public void AddNode(LayoutNode<T> node) {
-      var content = node.Content;
-      if (nodeMap.ContainsKey(content)) { throw new ArgumentException("Content already present in the dictionary."); }
-      nodeMap.Add(content, node);
-    }
-
-    public void AddNodes(IEnumerable<LayoutNode<T>> nodes) {
-      foreach (var node in nodes)
-        nodeMap.Add(node.Content, node);
-    }
-
-    public LayoutNode<T> GetNode(T content) {
-      LayoutNode<T> layoutNode;
-      nodeMap.TryGetValue(content, out layoutNode);
-      return layoutNode;
-    }
-
-    public void ResetCoordinates() {
-      foreach (var node in nodeMap.Values) {
-        node.ResetCoordinates();
-      }
-    }
-
-    public Dictionary<T, PointF> GetCoordinates() {
-      return nodeMap.ToDictionary(x => x.Key, x => new PointF(x.Value.X, x.Value.Y));
-    }
+        Expand(node, map);
+      }
+    }
+
 
     /// <summary>
     /// Transform LayoutNode coordinates so that all coordinates are positive and start from (0,0)
     /// </summary>
-    private void NormalizeCoordinates() {
-      var nodes = nodeMap.Values.ToList();
+    private static void NormalizeCoordinates(IEnumerable<LayoutNode<T>> nodes) {
       float xmin = 0, ymin = 0;
       foreach (var node in nodes) {
@@ -123 +109 @@
     }
 
-    public void Center(float width, float height) {
+    private void Center(float width, float height, IEnumerable<LayoutNode<T>> nodes) {
       // center layout on screen
-      var bounds = Bounds();
+      var bounds = Bounds(nodes);
       float dx = 0, dy = 0;
       if (width > bounds.Width) { dx = (width - bounds.Width) / 2f; }
       if (height > bounds.Height) { dy = (height - bounds.Height) / 2f; }
-      foreach (var node in nodeMap.Values) { node.Translate(dx, dy); }
-    }
-
-    public void FitToBounds(float width, float height) {
-      var bounds = Bounds();
+      foreach (var node in nodes) { node.Translate(dx, dy); }
+    }
+
+    private void FitToBounds(float width, float height, IEnumerable<LayoutNode<T>> nodes) {
+      var bounds = Bounds(nodes);
       var myWidth = bounds.Width;
       var myHeight = bounds.Height;
@@ -139 +125 @@
       if (myWidth <= width && myHeight <= height) return; // no need to fit since we are within bounds
 
-      var layers = nodeMap.Values.GroupBy(node => node.Level, node => node).ToList();
+      var layers = nodes.GroupBy(node => node.Level, node => node).ToList();
 
       if (myWidth > width) {
@@ -150 +136 @@
         float spacing = minHorizontalSpacing * x;
         foreach (var layer in layers) {
-          var nodes = layer.ToList();
+          var nodesLayer = layer.ToList();
           float minWidth = float.MaxValue;
-          for (int i = 0; i < nodes.Count - 1; ++i) { minWidth = Math.Min(minWidth, nodes[i + 1].X - nodes[i].X); }
+          for (int i = 0; i < nodesLayer.Count - 1; ++i) { minWidth = Math.Min(minWidth, nodesLayer[i + 1].X - nodesLayer[i].X); }
           float w = Math.Min(NodeWidth, minWidth - spacing);
-          foreach (var node in nodes) {
+          foreach (var node in nodesLayer) {
             node.X += (node.Width - w) / 2f;
             node.Width = w;
@@ -178 +164 @@
     }
 
-    public void Clear() {
-      layoutRoot = null;
-      nodeMap.Clear();
-    }
-
-    public void Reset() {
-      foreach (var layoutNode in nodeMap.Values) {
-        // reset layout-related parameters 
-        layoutNode.Reset();
-      }
-    }
-
-    public void CalculateLayout() {
-      if (layoutRoot == null) throw new Exception("Layout layoutRoot cannot be null.");
-      Reset(); // reset node parameters like Mod, Shift etc. and set coordinates to 0
-      FirstWalk(layoutRoot);
-      SecondWalk(layoutRoot, -layoutRoot.Prelim);
-      NormalizeCoordinates();
-    }
-
-    public void CalculateLayout(float width, float height) {
-      CalculateLayout();
-      FitToBounds(width, height);
-      Center(width, height);
-    }
 
     /// <summary>
@@ -208 +169 @@
     /// </summary>
     /// <returns></returns>
-    public RectangleF Bounds() {
+    private RectangleF Bounds(IEnumerable<LayoutNode<T>> nodes) {
       float xmin = 0, xmax = 0, ymin = 0, ymax = 0;
-      var list = nodeMap.Values.ToList();
-      foreach (LayoutNode<T> node in list) {
+      foreach (LayoutNode<T> node in nodes) {
         float x = node.X, y = node.Y;
         if (xmin > x) xmin = x;

branches/HeuristicLab.EvolutionTracking/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding.Views/3.4/SymbolicExpressionGrammarAllowedChildSymbolsControl.cs

@@ -105 +105 @@
 
       var tree = new SymbolicExpressionTree(new SymbolicExpressionTreeNode(Symbol));
-      symbolicExpressionTreeChart.SuspendRepaint = true;
       if (Grammar.GetMaximumSubtreeCount(Symbol) > 0) {
         for (int i = 0; i < Grammar.GetMaximumSubtreeCount(Symbol); i++) {
@@ -118 +117 @@
       }
       symbolicExpressionTreeChart.Tree = tree;
-
+      symbolicExpressionTreeChart.SuspendRepaint = true;
       foreach (var subtreeNode in tree.Root.Subtrees) {
         foreach (var allowedChildNode in subtreeNode.Subtrees) {
@@ -144 +143 @@
         }
       }
-
       symbolicExpressionTreeChart.SuspendRepaint = false;
       UpdateSelectedSymbolicExpressionTreeNodes();
@@ -155 +153 @@
         else visualNode.FillColor = Color.LightSteelBlue;
       }
-      symbolicExpressionTreeChart.Repaint();
+      symbolicExpressionTreeChart.RepaintNodes();
     }
 

branches/HeuristicLab.EvolutionTracking/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding.Views/3.4/SymbolicExpressionTreeChart.cs

@@ -27 +27 @@
 using System.Linq;
 using System.Windows.Forms;
-using Point = System.Drawing.Point;
+
 
 namespace HeuristicLab.Encodings.SymbolicExpressionTreeEncoding.Views {
@@ -50 +50 @@
       this.backgroundColor = Color.White;
       this.textFont = new Font(FontFamily.GenericSansSerif, 12);
-      //      layoutEngine = new ReingoldTilfordLayoutEngine<ISymbolicExpressionTreeNode> {
-      layoutEngine = new BoxesLayoutEngine<ISymbolicExpressionTreeNode> {
+
+      visualTreeNodes = new Dictionary<ISymbolicExpressionTreeNode, VisualTreeNode<ISymbolicExpressionTreeNode>>();
+      visualLines = new Dictionary<Tuple<ISymbolicExpressionTreeNode, ISymbolicExpressionTreeNode>, VisualTreeNodeConnection>();
+
+      layoutEngine = new ReingoldTilfordLayoutEngine<ISymbolicExpressionTreeNode>(n => n.Subtrees) {
         NodeWidth = preferredNodeWidth,
         NodeHeight = preferredNodeHeight,
@@ -57 +60 @@
         VerticalSpacing = minVerticalDistance
       };
-    }
+      reingoldTilfordToolStripMenuItem.Checked = true;
+    }
+
+    //private ILayoutEngine<ISymbolicExpressionTreeNode> TreeLayoutEngine {
+    //  get { return layoutEngine; }
+    //  set {
+    //    layoutEngine = value;
+    //    InitializeLayout();
+    //    Repaint();
+    //  }
+    //}
 
     public SymbolicExpressionTreeChart(ISymbolicExpressionTree tree)
@@ -106 +119 @@
       set {
         tree = value;
-        if (tree != null) {
-          Repaint();
-        }
+        Repaint();
       }
     }
@@ -127 +138 @@
       if (this.Width <= 1 || this.Height <= 1)
         this.image = new Bitmap(1, 1);
-      else
+      else {
         this.image = new Bitmap(Width, Height);
+      }
       this.Repaint();
+    }
+
+    public event EventHandler Repainted;//expose this event to notify the parent control that the tree was repainted
+    protected virtual void OnRepaint(object sender, EventArgs e) {
+      var repainted = Repainted;
+      if (repainted != null) {
+        repainted(sender, e);
+      }
     }
 
@@ -136 +156 @@
         this.GenerateImage();
         this.Refresh();
+        OnRepaint(this, EventArgs.Empty);
       }
     }
@@ -146 +167 @@
           foreach (var visualNode in visualTreeNodes.Values) {
             DrawTreeNode(graphics, visualNode);
+            if (visualNode.Content.SubtreeCount > 0) {
+              foreach (var visualSubtree in visualNode.Content.Subtrees.Select(s => visualTreeNodes[s])) {
+                DrawLine(graphics, visualNode, visualSubtree);
+              }
+            }
           }
         }
@@ -169 +195 @@
         graphics.Clear(backgroundColor);
         if (tree != null) {
-          DrawFunctionTree(tree, graphics, preferredNodeWidth, preferredNodeHeight, minHorizontalDistance, minVerticalDistance);
+          DrawFunctionTree(graphics, preferredNodeWidth, preferredNodeHeight, minHorizontalDistance, minVerticalDistance);
         }
       }
@@ -260 +286 @@
     #endregion
 
-    #region methods for painting the symbolic expression tree
-    private void DrawFunctionTree(ISymbolicExpressionTree symbExprTree, Graphics graphics, int preferredWidth, int preferredHeight, int minHDistance, int minVDistance) {
-      var root = symbExprTree.Root;
-      var actualRoot = root.SubtreeCount == 1 ? root.GetSubtree(0) : root;
+    private void CalculateLayout(int preferredWidth, int preferredHeight, int minHDistance, int minVDistance) {
       layoutEngine.NodeWidth = preferredWidth;
       layoutEngine.NodeHeight = preferredHeight;
       layoutEngine.HorizontalSpacing = minHDistance;
       layoutEngine.VerticalSpacing = minVDistance;
-      layoutEngine.Initialize(actualRoot, n => n.Subtrees, n => n.GetLength(), n => n.GetDepth());
-      layoutEngine.CalculateLayout(Width, Height);
-
-      var visualNodes = layoutEngine.GetVisualNodes().ToList();
+
+      var actualRoot = tree.Root;
+      if (actualRoot.Symbol is ProgramRootSymbol && actualRoot.SubtreeCount == 1) {
+        actualRoot = tree.Root.GetSubtree(0);
+      }
+
+      var visualNodes = layoutEngine.CalculateLayout(actualRoot, Width, Height).ToList();
       visualTreeNodes = visualNodes.ToDictionary(x => x.Content, x => x);
       visualLines = new Dictionary<Tuple<ISymbolicExpressionTreeNode, ISymbolicExpressionTreeNode>, VisualTreeNodeConnection>();
@@ -279 +305 @@
         }
       }
-      // draw nodes and connections
+    }
+
+    #region methods for painting the symbolic expression tree
+    private void DrawFunctionTree(Graphics graphics, int preferredWidth, int preferredHeight, int minHDistance, int minVDistance) {
+      CalculateLayout(preferredWidth, preferredHeight, minHDistance, minVDistance);
+      var visualNodes = visualTreeNodes.Values;
+      //draw nodes and connections
       foreach (var visualNode in visualNodes) {
         DrawTreeNode(visualNode);
@@ -325 +357 @@
       }
     }
+
+    protected void DrawLine(Graphics graphics, VisualTreeNode<ISymbolicExpressionTreeNode> startNode, VisualTreeNode<ISymbolicExpressionTreeNode> endNode) {
+      var origin = new Point(startNode.X + startNode.Width / 2, startNode.Y + startNode.Height);
+      var target = new Point(endNode.X + endNode.Width / 2, endNode.Y);
+      graphics.Clip = new Region(new Rectangle(Math.Min(origin.X, target.X), origin.Y, Math.Max(origin.X, target.X), target.Y));
+      var visualLine = GetVisualSymbolicExpressionTreeNodeConnection(startNode.Content, endNode.Content);
+      using (var linePen = new Pen(visualLine.LineColor)) {
+        linePen.DashStyle = visualLine.DashStyle;
+        graphics.DrawLine(linePen, origin, target);
+      }
+    }
     #endregion
     #region save image
@@ -340 +383 @@
       Image image = new Bitmap(Width, Height);
       using (Graphics g = Graphics.FromImage(image)) {
-        DrawFunctionTree(tree, g, preferredNodeWidth, preferredNodeHeight, minHorizontalDistance, minVerticalDistance);
+        DrawFunctionTree(g, preferredNodeWidth, preferredNodeHeight, minHorizontalDistance, minVerticalDistance);
       }
       image.Save(filename);
@@ -350 +393 @@
         using (Metafile file = new Metafile(filename, g.GetHdc())) {
           using (Graphics emfFile = Graphics.FromImage(file)) {
-            DrawFunctionTree(tree, emfFile, preferredNodeWidth, preferredNodeHeight, minHorizontalDistance, minVerticalDistance);
+            DrawFunctionTree(emfFile, preferredNodeWidth, preferredNodeHeight, minHorizontalDistance, minVerticalDistance);
           }
         }
@@ -369 +412 @@
 
     private void reingoldTilfordToolStripMenuItem_Click(object sender, EventArgs e) {
-      layoutEngine = new ReingoldTilfordLayoutEngine<ISymbolicExpressionTreeNode> {
+      layoutEngine = new ReingoldTilfordLayoutEngine<ISymbolicExpressionTreeNode>(n => n.Subtrees) {
         NodeWidth = preferredNodeWidth,
         NodeHeight = preferredNodeHeight,
@@ -375 +418 @@
         VerticalSpacing = minVerticalDistance
       };
+      reingoldTilfordToolStripMenuItem.Checked = true;
+      boxesToolStripMenuItem.Checked = false;
       Repaint();
     }
 
     private void boxesToolStripMenuItem_Click(object sender, EventArgs e) {
-      layoutEngine = new BoxesLayoutEngine<ISymbolicExpressionTreeNode> {
+      layoutEngine = new BoxesLayoutEngine<ISymbolicExpressionTreeNode>(n => n.Subtrees, n => n.GetLength(), n => n.GetDepth()) {
         NodeWidth = preferredNodeWidth,
         NodeHeight = preferredNodeHeight,
@@ -385 +430 @@
         VerticalSpacing = minVerticalDistance
       };
+      reingoldTilfordToolStripMenuItem.Checked = false;
+      boxesToolStripMenuItem.Checked = true;
       Repaint();
     }