/// <summary>
/// Runs the force-directed layout algorithm on this Diagram, using the specified parameters.
/// </summary>
/// <param name="damping">Value between 0 and 1 that slows the motion of the nodes during layout.</param>
/// <param name="springLength">Value in pixels representing the length of the imaginary springs that run along the connectors.</param>
/// <param name="maxIterations">Maximum number of iterations before the algorithm terminates.</param>
/// <param name="deterministic">Whether to use a random or deterministic layout.</param>
public void Arrange(double damping, int springLength, int maxIterations, bool deterministic) {
// random starting positions can be made deterministic by seeding System.Random with a constant
Random rnd = deterministic ? new Random(0) : new Random();
// copy nodes into an array of metadata and randomise initial coordinates for each node
NodeLayoutInfo[] layout = new NodeLayoutInfo[mNodes.Count];
for (int i = 0; i < mNodes.Count; i++) {
layout[i] = new NodeLayoutInfo(mNodes[i], new Vector(), Point.Empty);
layout[i].Node.Location = new Point(rnd.Next(-50, 50), rnd.Next(-50, 50));
}
int stopCount = 0;
int iterations = 0;
while (true) {
double totalDisplacement = 0;
for (int i=0; i<layout.Length; i++) {
NodeLayoutInfo current = layout[i];
// express the node's current position as a vector, relative to the origin
Vector currentPosition = new Vector(CalcDistance(Point.Empty, current.Node.Location), GetBearingAngle(Point.Empty, current.Node.Location));
Vector netForce = new Vector(0, 0);
// determine repulsion between nodes
foreach (Node other in mNodes) {
if (other != current.Node) netForce += CalcRepulsionForce(current.Node, other);
}
// determine attraction caused by connections
foreach (Node child in current.Node.Connections) {
netForce += CalcAttractionForce(current.Node, child, springLength);
}
foreach (Node parent in mNodes) {
if (parent.Connections.Contains(current.Node)) netForce += CalcAttractionForce(current.Node, parent, springLength);
}
// apply net force to node velocity
current.Velocity = (current.Velocity + netForce) * damping;
// apply velocity to node position
current.NextPosition = (currentPosition + current.Velocity).ToPoint();
}
// move nodes to resultant positions (and calculate total displacement)
for (int i = 0; i < layout.Length; i++) {
NodeLayoutInfo current = layout[i];
totalDisplacement += CalcDistance(current.Node.Location, current.NextPosition);
current.Node.Location = current.NextPosition;
}
iterations++;
if (totalDisplacement < 10) stopCount++;
if (stopCount > 15) break;
if (iterations > maxIterations) break;
}
// center the diagram around the origin
Rectangle logicalBounds = GetDiagramBounds();
Point midPoint = new Point(logicalBounds.X + (logicalBounds.Width / 2), logicalBounds.Y + (logicalBounds.Height / 2));
foreach (Node node in mNodes) {
node.Location -= (Size)midPoint;
}
}
public Point NextPosition; // the node's position after the next iteration
/// <summary>
/// Initialises a new instance of the Diagram.NodeLayoutInfo class, using the specified parameters.
/// </summary>
/// <param name="node"></param>
/// <param name="velocity"></param>
/// <param name="nextPosition"></param>
public NodeLayoutInfo(Node node, Vector velocity, Point nextPosition) {
Node = node;
Velocity = velocity;
NextPosition = nextPosition;
}