LayOutGraphCore
(
IGraph graph,
ICollection <IVertex> verticesToLayOut,
LayoutContext layoutContext,
BackgroundWorker backgroundWorker
)
{
Debug.Assert(graph != null);
Debug.Assert(verticesToLayOut != null);
Debug.Assert(verticesToLayOut.Count > 0);
Debug.Assert(layoutContext != null);
AssertValid();
Int32 iVertices = verticesToLayOut.Count;
ICollection <IEdge> oEdgesToLayOut =
GetEdgesToLayOut(graph, verticesToLayOut);
// If the graph has already been laid out, use the current vertex
// locations as initial values.
if (!LayoutMetadataUtil.GraphHasBeenLaidOut(graph))
{
// The graph has not been laid out. By default, randomize the
// locations of those vertices that are not locked. If the graph
// has the FruchtermanReingoldLayoutSelectivelyRandomize key,
// however, randomize the locations of those vertices that have
// IVertex.Location set to LayoutBase.RandomizeThisLocation and are
// not locked.
Boolean bSelectivelyRandomize = graph.ContainsKey(
ReservedMetadataKeys.
FruchtermanReingoldLayoutSelectivelyRandomize);
RandomizeVertexLocations(verticesToLayOut, layoutContext,
new Random(1), bSelectivelyRandomize);
}
// Store required metadata on the graph's vertices.
InitializeMetadata(verticesToLayOut);
Rectangle oRectangle = layoutContext.GraphRectangle;
Single fArea = oRectangle.Width * oRectangle.Height;
Debug.Assert(iVertices > 0);
// The algorithm in Figure 1 of the Fruchterman-Reingold paper doesn't
// include the constant C, but it is included in the calculation for k
// under the "Modelling the forces" section.
Single k = m_fC * (Single)Math.Sqrt(fArea / (Single)iVertices);
// The rectangle is guaranteed to have non-zero width and height, so
// k should never be zero.
Debug.Assert(k != 0);
// Use the simple cooling algorithm suggested in the Fruchterman-
// Reingold paper.
Single fTemperature = oRectangle.Width / 10F;
Debug.Assert(m_iIterations != 0);
Single fTemperatureDecrement = fTemperature / (Single)m_iIterations;
while (fTemperature > 0)
{
if (backgroundWorker != null &&
backgroundWorker.CancellationPending)
{
return(false);
}
// Calculate the attractive and repulsive forces between the
// vertices. The results get written to metadata on the vertices.
CalculateRepulsiveForces(verticesToLayOut, k);
CalculateAttractiveForces(oEdgesToLayOut, k);
Single fNextTemperature = fTemperature - fTemperatureDecrement;
// Set the unbounded location of each vertex based on the vertex's
// current location and the calculated forces.
SetUnboundedLocations(verticesToLayOut, layoutContext,
fTemperature, fNextTemperature > 0);
// Decrease the temperature.
fTemperature = fNextTemperature;
// For graphs with many edges, telling NodeXLControl to refresh
// its window (which is the end result of calling
// FireLayOutGraphIterationCompleted()) can significantly slow down
// performance, so don't do it.
//
// For example, a random graph with 1,000 vertices and 10,000 edges
// took 3.6 seconds to lay out when the window was repeatedly
// refreshed, but only 2.1 seconds with no refreshes.
//
// The performance improvement is much smaller for graphs with a
// large number of vertices, where the O(V-squared) behavior in
// CalculateRepulsiveForces() dominates the layout time.
#if false
if (backgroundWorker != null)
{
FireLayOutGraphIterationCompleted();
}
#endif
}
RemoveMetadata(verticesToLayOut);
return(true);
}
LayOutSmallerComponentsInBins
(
IGraph graph,
ICollection <IVertex> verticesToLayOut,
LayoutContext layoutContext,
out ICollection <IVertex> remainingVertices,
out Rectangle remainingRectangle
)
{
AssertValid();
remainingVertices = null;
remainingRectangle = Rectangle.Empty;
// This method modifies some of the graph's metadata. Save the
// original metadata.
Boolean bOriginalGraphHasBeenLaidOut =
LayoutMetadataUtil.GraphHasBeenLaidOut(graph);
ICollection <IVertex> oOriginalLayOutTheseVerticesOnly =
(ICollection <IVertex>)graph.GetValue(
ReservedMetadataKeys.LayOutTheseVerticesOnly,
typeof(ICollection <IVertex>));
// Split the vertices into strongly connected components, sorted in
// increasing order of vertex count.
ConnectedComponentCalculator oConnectedComponentCalculator =
new ConnectedComponentCalculator();
IList <LinkedList <IVertex> > oComponents =
oConnectedComponentCalculator.CalculateStronglyConnectedComponents(
verticesToLayOut, graph, true);
Int32 iComponents = oComponents.Count;
// This object will split the graph rectangle into bin rectangles.
RectangleBinner oRectangleBinner = new RectangleBinner(
layoutContext.GraphRectangle, m_iBinLength);
Int32 iComponent = 0;
for (iComponent = 0; iComponent < iComponents; iComponent++)
{
LinkedList <IVertex> oComponent = oComponents[iComponent];
Int32 iVerticesInComponent = oComponent.Count;
if (iVerticesInComponent > m_iMaximumVerticesPerBin)
{
// The vertices in the remaining components should not be
// binned.
break;
}
Rectangle oBinRectangle;
if (!oRectangleBinner.TryGetNextBin(out oBinRectangle))
{
// There is no room for an additional bin rectangle.
break;
}
// Lay out the component within the bin rectangle.
LayOutComponentInBin(graph, oComponent, oBinRectangle);
}
// Restore the original metadata on the graph.
if (bOriginalGraphHasBeenLaidOut)
{
LayoutMetadataUtil.MarkGraphAsLaidOut(graph);
}
else
{
LayoutMetadataUtil.MarkGraphAsNotLaidOut(graph);
}
if (oOriginalLayOutTheseVerticesOnly != null)
{
graph.SetValue(ReservedMetadataKeys.LayOutTheseVerticesOnly,
oOriginalLayOutTheseVerticesOnly);
}
else
{
graph.RemoveKey(ReservedMetadataKeys.LayOutTheseVerticesOnly);
}
if (oRectangleBinner.TryGetRemainingRectangle(
out remainingRectangle))
{
remainingVertices = GetRemainingVertices(oComponents, iComponent);
return(remainingVertices.Count > 0);
}
return(false);
}