source: stable/HeuristicLab.ExtLibs/HeuristicLab.Netron/3.0.2672.12446/Netron.Diagramming.Core-3.0.2672.12446/Layout/FruchtermanReingoldLayout.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using Netron.Diagramming.Core.Analysis;
namespace Netron.Diagramming.Core {
  /// <summary>
  /// <para>Layout instance implementing the Fruchterman-Reingold algorithm for
  ///  force-directed placement of graph nodes. The computational complexity of
  ///  this algorithm is quadratic [O(n^2)] in the number of nodes, so should
  ///  only be applied for relatively small graphs, particularly in interactive
  ///  situations.</para>
  ///  
  ///  <para>This implementation was ported from the implementation in the
  ///  <a href="http://jung.sourceforge.net/">JUNG</a> framework.</para>
  /// </summary>
  class FruchtermanReingoldLayout : LayoutBase {
    #region Fields
    private double forceConstant;
    private double temp;
    private int maxIter = 300;

    protected int m_fidx;
    private Random rnd;
    private static double EPSILON = 0.000001D;
    private static double ALPHA = 0.1D;

    Dictionary<string, Params> Pars;
    double width;
    double height;
    BackgroundWorker worker;
    #endregion

    #region Constructor
    ///<summary>
    ///Default constructor
    ///</summary>
    public FruchtermanReingoldLayout(IController controller)
      : base("FruchtermanReingold Layout", controller) {
    }
    #endregion

    #region Methods

    /// <summary>
    /// Inits the calculational state
    /// </summary>
    private bool Init() {
      this.Graph = this.Model as IGraph;

      if (Graph == null)
        throw new InconsistencyException("The model has not been set and the Graph property is hence 'null'");

      //this.LayoutRoot = this.Controller.Model.LayoutRoot;//could be null if not set in the GUI
      //Graph.ClearSpanningTree();
      //Graph.MakeSpanningTree(LayoutRoot as INode);

      Pars = new Dictionary<string, Params>();
      if (Nodes.Count == 0)
        return false;
      if (Edges.Count == 0) //this layout is base on embedded springs in the connections
        return false;

      width = (double)Bounds.Width;
      height = (double)Bounds.Height;
      rnd = new Random();


      temp = width / 10;
      forceConstant = 0.75 * Math.Sqrt(height * width / Nodes.Count);

      // initialize node positions


      double scaleW = ALPHA * width / 2;
      double scaleH = ALPHA * height / 2;
      Params par;
      double[] loc;
      foreach (INode node in Nodes) {
        loc = new double[2];
        loc[0] = Center.X + rnd.NextDouble() * scaleW;
        loc[1] = Center.Y + rnd.NextDouble() * scaleH;
        par = new Params(loc, new double[2]);
        Pars.Add(node.Uid.ToString(), par);
      }
      return true;
    }

    /// <summary>
    /// Runs this instance.
    /// </summary>
    public override void Run() {
      width = this.Bounds.Width;
      height = this.Bounds.Height;
      Run(1000);


    }
    /// <summary>
    /// Stops this instance.
    /// </summary>
    public override void Stop() {
      if (worker != null && worker.IsBusy)
        worker.CancelAsync();
    }
    /// <summary>
    /// Runs the layout for a specified time.
    /// </summary>
    /// <param name="time">The time.</param>
    public override void Run(int time) {
      if (Init()) {

        worker = new BackgroundWorker();
        worker.DoWork += new DoWorkEventHandler(worker_DoWork);
        worker.RunWorkerAsync(time);

      }

    }

    /// <summary>
    /// Handles the DoWork event of the worker control.
    /// </summary>
    /// <param name="sender">The source of the event.</param>
    /// <param name="e">The <see cref="T:System.ComponentModel.DoWorkEventArgs"/> instance containing the event data.</param>
    void worker_DoWork(object sender, DoWorkEventArgs e) {
      //this.Controller.View.Suspend();
      DateTime start = DateTime.Now;
      while (DateTime.Now < start.AddMilliseconds((int)e.Argument)) {
        RunStep();

      }
      //this.Controller.View.Resume();
      UpdateShapes();

      RunAnimation();
    }

    private void RunAnimation() {

    }

    /// <summary>
    /// Runs a single step.
    /// </summary>
    private void RunStep() {

      for (int curIter = 0; curIter < maxIter; curIter++) {

        // Calculate repulsion
        foreach (INode node in Nodes) {
          if (node.IsFixed) continue;
          CalculateRepulsion(node);
        }

        // Calculate attraction
        foreach (IEdge edge in Edges) {
          CalculateAttraction(edge);
        }

        foreach (INode node in Nodes) {
          if (node.IsFixed) continue;
          CalculatePositions(node);
        }

        CoolDown(curIter);


      }


    }

    private void UpdateShapes() {
      int x, y;
      lock (Nodes)
        lock (Pars) {
          foreach (INode node in Nodes) {
            x = Convert.ToInt32(Pars[node.Uid.ToString()].loc[0]) - node.Rectangle.X;
            y = Convert.ToInt32(Pars[node.Uid.ToString()].loc[1]) - node.Rectangle.Y;
            //if (node.Rectangle.X + x < width - node.Rectangle.Width - 10 && node.Rectangle.X + x > 10 && node.Rectangle.Y + y < height - node.Rectangle.Height - 10 && node.Rectangle.Y + y > 10)
            node.MoveBy(new Point(x, y));
          }
        }
    }

    #region Calculations
    public void CalculatePositions(INode n) {
      Params np = Pars[n.Uid.ToString()];


      double deltaLength = Math.Max(EPSILON, Math.Sqrt(np.disp[0] * np.disp[0] + np.disp[1] * np.disp[1]));

      double xDisp = np.disp[0] / deltaLength * Math.Min(deltaLength, temp);

      if (Double.IsNaN(xDisp)) {
        System.Diagnostics.Trace.WriteLine("Oops, the layout resulted in a NaN problem.");
        return;
      }

      double yDisp = np.disp[1] / deltaLength * Math.Min(deltaLength, temp);

      np.loc[0] += xDisp;
      np.loc[1] += yDisp;


      // don't let nodes leave the display
      double borderWidth = width / 50.0;
      double x = np.loc[0];
      if (x < borderWidth) {
        x = borderWidth + rnd.NextDouble() * borderWidth * 2.0;
      } else if (x > (width - borderWidth)) {
        x = width - borderWidth - rnd.NextDouble() * borderWidth * 2.0;
      }

      double y = np.loc[1];
      if (y < borderWidth) {
        y = borderWidth + rnd.NextDouble() * borderWidth * 2.0;
      } else if (y > (height - borderWidth)) {
        y = height - borderWidth - rnd.NextDouble() * borderWidth * 2.0;
      }

      np.loc[0] = x;
      np.loc[1] = y;
    }

    /// <summary>
    /// Calculates the attraction or tension on the given edge.
    /// </summary>
    /// <param name="edge">The edge.</param>
    public void CalculateAttraction(IEdge edge) {
      INode n1, n2;
      Params n1p = new Params();
      Params n2p = new Params();
      if (edge.SourceNode != null) {
        n2 = edge.SourceNode;
        n2p = Pars[n2.Uid.ToString()];
      };
      if (edge.TargetNode != null) {
        n1 = edge.TargetNode;
        n1p = Pars[n1.Uid.ToString()];
      };



      double xDelta = n1p.loc[0] - n2p.loc[0];
      double yDelta = n1p.loc[1] - n2p.loc[1];

      double deltaLength = Math.Max(EPSILON, Math.Sqrt(xDelta * xDelta + yDelta * yDelta));
      double force = (deltaLength * deltaLength) / forceConstant;

      if (Double.IsNaN(force)) {
        System.Diagnostics.Trace.WriteLine("Oops, the layout resulted in a NaN problem.");
        return;
      }

      double xDisp = (xDelta / deltaLength) * force;
      double yDisp = (yDelta / deltaLength) * force;

      n1p.disp[0] -= xDisp; n1p.disp[1] -= yDisp;
      n2p.disp[0] += xDisp; n2p.disp[1] += yDisp;
    }

    public void CalculateRepulsion(INode node) {
      Params np = Pars[node.Uid.ToString()];
      np.disp[0] = 0.0; np.disp[1] = 0.0;

      foreach (INode n2 in Nodes) {

        Params n2p = Pars[n2.Uid.ToString()];
        if (n2.IsFixed) continue;
        if (node != n2) {
          double xDelta = np.loc[0] - n2p.loc[0];
          double yDelta = np.loc[1] - n2p.loc[1];

          double deltaLength = Math.Max(EPSILON, Math.Sqrt(xDelta * xDelta + yDelta * yDelta));

          double force = (forceConstant * forceConstant) / deltaLength;

          if (Double.IsNaN(force)) {
            System.Diagnostics.Trace.WriteLine("Oops, the layout resulted in a NaN problem.");
            return;
          }

          np.disp[0] += (xDelta / deltaLength) * force;
          np.disp[1] += (yDelta / deltaLength) * force;
        }
      }
    }

    private void CoolDown(int curIter) {
      temp *= (1.0 - curIter / (double)maxIter);
    }
    #endregion


    /// <summary>
    /// Paramter blob to temporarily keep working data of one node.
    /// </summary>
    struct Params {
      public double[] loc;
      public double[] disp;

      public Params(double[] loc, double[] disp) {
        this.loc = loc;
        this.disp = disp;
      }


    }


    #endregion

  }
}