checkShellInsideHole method

Coordinate? checkShellInsideHole(LinearRing shell, LinearRing hole, GeometryGraph graph)

This routine checks to see if a shell is properly contained in a hole. It assumes that the edges of the shell and hole do not properly intersect.

@return null if the shell is properly contained, or a Coordinate which is not inside the hole if it is not

Implementation

Coordinate? checkShellInsideHole(
    LinearRing shell, LinearRing hole, GeometryGraph graph) {
  List<Coordinate> shellPts = shell.getCoordinates();
  List<Coordinate> holePts = hole.getCoordinates();
  // TODO: improve performance of this - by sorting pointlists for instance?
  Coordinate? shellPt = findPtNotNode(shellPts, hole, graph);
  // if point is on shell but not hole, check that the shell is inside the hole
  if (shellPt != null) {
    bool insideHole = PointLocation.isInRing(shellPt, holePts);
    if (!insideHole) {
      return shellPt;
    }
  }
  Coordinate? holePt = findPtNotNode(holePts, shell, graph);
  // if point is on hole but not shell, check that the hole is outside the shell
  if (holePt != null) {
    bool insideShell = PointLocation.isInRing(holePt, shellPts);
    if (insideShell) {
      return holePt;
    }
    return null;
  }
  assert(true, "points in shell and hole appear to be equal");
  return null;
}