/// <summary>
/// Gets the side code for a horizontal segment which is incident on a node,
/// given any one the boundaries incident on the node.
/// </summary>
/// <param name="id">The divider we know about (incident on node).</param>
/// <param name="isStart">True if it's the start of <c>ib</c>.</param>
/// <param name="od">The divider the returned side refers to</param>
/// <returns>Side.Left if the segment is to the left of <c>ob</c>, Side.Right
/// if segment to the right.</returns>
internal Side GetSide(IDivider id, bool isStart, out IDivider od)
{
ConnectionFinder connect = new ConnectionFinder(id, isStart, this);
od = connect.Next;
return(connect.IsStart ? Side.Right : Side.Left);
}
/// <summary>
/// Get the dividers defining a new polygon ring, starting with the specified divider.
/// </summary>
/// <param name="start">The first divider for the new ring</param>
/// <param name="isPolLeft">Is the polygon ring to the left of the divider?</param>
/// <returns>The dividers making up the new ring</returns>
List<Face> GetPolygonFaces(IDivider start, bool isPolLeft)
{
List<Face> result = new List<Face>(10);
bool isLeft = isPolLeft;
IDivider d = start;
uint nface = 0;
// Cycle the polygon until we return to the first divider.
for (; ; )
{
// Define the next face
Face face = new Face(d, isLeft);
nface++;
// If we've created quite a few faces (more than you'd expect), confirm there are no duplicate faces.
if ((nface % 256)==0 && GetDuplicateFace(result)!=null)
{
IDivider bad = GetDuplicateFace(result).Divider;
string msg = String.Format("Topology.GetPolygonDividers - Duplicate face from ({0}) to ({1}) [Line {2}]",
bad.From.ToString(), bad.To.ToString(), bad.Line.InternalId);
DumpFaces(msg, result);
throw new Exception(msg);
}
result.Add(face);
// Get the next divider in the cycle.
ConnectionFinder connect = new ConnectionFinder();
if (!connect.Create(d, isLeft))
throw new Exception("Cannot find connecting boundary");
// If we connected to the start of another divider, the polygon is
// to the right. The end of the next divider means the polygon is
// to the left.
isLeft = !connect.IsStart;
d = connect.Next;
// Break out of loop if we have come back to the first divider.
if (d==start && isLeft==isPolLeft)
break;
}
return result;
}