/// <summary>
/// If the existing number of bends is 2 mod 3 (i.e. the bends are consistent with
/// what the bezier style expects),
/// this implementation creates a triple of collinear bends and adjust the neighboring bends
/// in a way that the shape of the curve is not changed initially and returns the middle bend.
/// If there are no bends at all, it creates a triple plus two initial and final control bends, all of them collinear.
/// Otherwise, the fallback bend creator is used to create a bend with its default strategy.
/// </summary>
/// <returns>The index of middle bend of a control point triple if such a triple was created,
/// or the index of the newly created single bend.</returns>
public int CreateBend(IInputModeContext context, IGraph graph, IEdge edge, PointD location)
{
switch (edge.Bends.Count)
{
case 0:
var spl = edge.SourcePort.GetLocation();
var tpl = edge.TargetPort.GetLocation();
//a single linear segment... we just insert 5 collinear bends adjusted to the angle of the linear segment,
//approximately evenly spaced
graph.AddBend(edge, (location - spl) / 4 + spl, 0);
graph.AddBend(edge, -(location - spl) / 4 + location, 1);
graph.AddBend(edge, location, 2);
graph.AddBend(edge, (location - spl) / 4 + location, 3);
graph.AddBend(edge, location + (tpl - location) * 3 / 4, 4);
return(2);
case 1:
//Use the default strategy to insert a single bend at the correct index
return(fallBackCreator.CreateBend(context, graph, edge, location));
default:
var pathPoints = edge.GetPathPoints();
if (pathPoints.Count % 3 == 1)
{
//Consistent number of existing points
//Try to insert a smooth bend
//I.e. a triple of three collinear bends and adjust the neighbor bends
//Various quality measures and counters
var segmentIndex = 0;
var pathCounter = 0;
var bestDistanceSqr = Double.PositiveInfinity;
double bestRatio = Double.NaN;
//The index of the segment where we want to create the bend in the end
int bestIndex = -1;
//Find the best segment
while (pathCounter + 3 < pathPoints.Count)
{
//Get the control points defining the current segment
var cp0 = pathPoints[pathCounter++];
var cp1 = pathPoints[pathCounter++];
var cp2 = pathPoints[pathCounter++];
//Consecutive segments share the last/first control point! So we may not advance the counter here
var cp3 = pathPoints[pathCounter];
//Shift a cubic segment
//
//Here we assume that the path is actually composed of cubic segments, only.
//Alternatively, we could inspect the actual path created by the edge renderer - this would also
//allow to deal with intermediate non cubic segments, but we'd have to associate those
//path segments somehow with the correct bends again, so again this would be tied to the actual
//renderer implementation.
var fragment = new GeneralPath(2);
fragment.MoveTo(cp0);
fragment.CubicTo(cp1, cp2, cp3);
//Try to find the projection onto the fragment
var ratio = fragment.GetProjection(location, 0);
if (ratio.HasValue)
{
//Actually found a projection ratio
//Determine the point on the curve - the tangent provides this
var tangent = fragment.GetTangent(0, ratio.Value);
if (tangent.HasValue)
{
//There actually is a tangent
var d = (location - tangent.Value.Point).SquaredVectorLength;
//Is this the best distance?
if (d < bestDistanceSqr)
{
bestDistanceSqr = d;
//Remember ratio (needed to split the curve)
bestRatio = ratio.Value;
//and the index, of course
bestIndex = segmentIndex;
}
}
}
++segmentIndex;
}
if (bestIndex != -1)
{
//Actually found a segment
//For the drag, we want to move the middle bend
return(CreateBends(graph, edge, bestIndex, bestRatio, pathPoints).GetIndex());
}
//No best segment found (for whatever reason) - we don't want to create a bend so that we don't mess up anything
return(-1);
}
else
{
//No consistent number of bends - just insert a single bend
//We could also see whether we actually would have a cubic segment on the path, and treat that differently
//However, why bother - just create the edge with a correct number of points instead
return(fallBackCreator.CreateBend(context, graph, edge, location));
}
}
}