computeLabelling method

void computeLabelling(List<GeometryGraph> geomGraph)

Implementation

void computeLabelling(List<GeometryGraph> geomGraph) {
  computeEdgeEndLabels(geomGraph[0].getBoundaryNodeRule());
  // Propagate side labels  around the edges in the star
  // for each parent Geometry
//Debug.print(this);
  propagateSideLabels(0);
//Debug.print(this);
//Debug.printIfWatch(this);
  propagateSideLabels(1);
//Debug.print(this);
//Debug.printIfWatch(this);

  /**
   * If there are edges that still have null labels for a geometry
   * this must be because there are no area edges for that geometry incident on this node.
   * In this case, to label the edge for that geometry we must test whether the
   * edge is in the interior of the geometry.
   * To do this it suffices to determine whether the node for the edge is in the interior of an area.
   * If so, the edge has location INTERIOR for the geometry.
   * In all other cases (e.g. the node is on a line, on a point, or not on the geometry at all) the edge
   * has the location EXTERIOR for the geometry.
   * <p>
   * Note that the edge cannot be on the BOUNDARY of the geometry, since then
   * there would have been a parallel edge from the Geometry at this node also labelled BOUNDARY
   * and this edge would have been labelled in the previous step.
   * <p>
   * This code causes a problem when dimensional collapses are present, since it may try and
   * determine the location of a node where a dimensional collapse has occurred.
   * The point should be considered to be on the EXTERIOR
   * of the polygon, but locate() will return INTERIOR, since it is passed
   * the original Geometry, not the collapsed version.
   *
   * If there are incident edges which are Line edges labelled BOUNDARY,
   * then they must be edges resulting from dimensional collapses.
   * In this case the other edges can be labelled EXTERIOR for this Geometry.
   *
   * MD 8/11/01 - NOT TRUE!  The collapsed edges may in fact be in the interior of the Geometry,
   * which means the other edges should be labelled INTERIOR for this Geometry.
   * Not sure how solve this...  Possibly labelling needs to be split into several phases:
   * area label propagation, symLabel merging, then finally null label resolution.
   */
  List<bool> hasDimensionalCollapseEdge = [false, false];
  for (Iterator it = iterator(); it.moveNext();) {
    EdgeEnd e = it.current;
    Label label = e.getLabel()!;
    for (int geomi = 0; geomi < 2; geomi++) {
      if (label.isLine(geomi) &&
          label.getLocation(geomi) == Location.BOUNDARY)
        hasDimensionalCollapseEdge[geomi] = true;
    }
  }
//Debug.print(this);
  for (Iterator it = iterator(); it.moveNext();) {
    EdgeEnd e = it.current;
    Label label = e.getLabel()!;
//Debug.println(e);
    for (int geomi = 0; geomi < 2; geomi++) {
      if (label.isAnyNull(geomi)) {
        int loc = Location.NONE;
        if (hasDimensionalCollapseEdge[geomi]) {
          loc = Location.EXTERIOR;
        } else {
          Coordinate p = e.getCoordinate()!;
          loc = getLocation(geomi, p, geomGraph);
        }
        label.setAllLocationsIfNullWithIndex(geomi, loc);
      }
    }
//Debug.println(e);
  }
//Debug.print(this);
//Debug.printIfWatch(this);
}