/// <summary>
/// Returns the subquad containing the envelope. Creates the subquad if it does not already exist.
/// </summary>
/// <param name="searchEnv"></param>
/// <returns></returns>
public Node GetNode(Envelope searchEnv)
{
int subnodeIndex = GetSubnodeIndex(searchEnv, _centre);
// if subquadIndex is -1 searchEnv is not contained in a subquad
if (subnodeIndex != -1)
{
// create the quad if it does not exist
Node node = GetSubnode(subnodeIndex);
// recursively search the found/created quad
return(node.GetNode(searchEnv));
}
else
{
return(this);
}
}
/// <summary>
/// insert an item which is known to be contained in the tree rooted at
/// the given QuadNode root. Lower levels of the tree will be created
/// if necessary to hold the item.
/// </summary>
/// <param name="tree"></param>
/// <param name="itemEnv"></param>
/// <param name="item"></param>
private void InsertContained(Node tree, Envelope itemEnv, Object item)
{
if (!tree.Envelope.Contains(itemEnv))
{
throw new TopologyException("Node envelope must contain item envelope");
}
// Do NOT create a new quad for zero-area envelopes - this would lead
// to infinite recursion. Instead, use a heuristic of simply returning
// the smallest existing quad containing the query
bool isZeroX = IntervalSize.IsZeroWidth(itemEnv.MinX, itemEnv.MaxX);
bool isZeroY = IntervalSize.IsZeroWidth(itemEnv.MinX, itemEnv.MaxX);
NodeBase node;
if (isZeroX || isZeroY)
{
node = tree.Find(itemEnv);
}
else
{
node = tree.GetNode(itemEnv);
}
node.Add(item);
}
