Improve Quadrant computation robustness by using vector endpoints

modules/core/src/main/java/org/locationtech/jts/algorithm/PolygonNodeTopology.java

@@ -142,8 +142,8 @@ private static int compareBetween(Coordinate origin, Coordinate p, Coordinate e0
    * @return true if vector P has angle greater than Q
    */
   private static boolean isAngleGreater(Coordinate origin, Coordinate p, Coordinate q) {      
-    int quadrantP = quadrant(origin, p);
-    int quadrantQ = quadrant(origin, q);
+    int quadrantP = Quadrant.quadrant(origin, p);
+    int quadrantQ = Quadrant.quadrant(origin, q);
 
     /**
      * If the vectors are in different quadrants, 
@@ -170,8 +170,8 @@ private static boolean isAngleGreater(Coordinate origin, Coordinate p, Coordinat
    * @return a negative integer, zero, or a positive integer as this vector P has angle less than, equal to, or greater than vector Q
    */
   public static int compareAngle(Coordinate origin, Coordinate p, Coordinate q) {      
-    int quadrantP = quadrant(origin, p);
-    int quadrantQ = quadrant(origin, q);
+    int quadrantP = Quadrant.quadrant(origin, p);
+    int quadrantQ = Quadrant.quadrant(origin, q);
 
     /**
      * If the vectors are in different quadrants, 
@@ -190,11 +190,6 @@ public static int compareAngle(Coordinate origin, Coordinate p, Coordinate q) {
     default: return 0;
     }
   }
-
-  private static int quadrant(Coordinate origin, Coordinate p) {
-    double dx = p.getX() - origin.getX();
-    double dy = p.getY() - origin.getY();
-    return Quadrant.quadrant(dx,  dy);
-  }
+
 
 }

modules/core/src/main/java/org/locationtech/jts/geom/Quadrant.java

@@ -34,6 +34,9 @@ public class Quadrant
    * Returns the quadrant of a directed line segment (specified as x and y
    * displacements, which cannot both be 0).
    * 
+   * If the segment coordinates are available it is more robust
+   * to use {@link #quadrant(Coordinate, Coordinate). 
+   * 
    * @throws IllegalArgumentException if the displacements are both 0
    */
   public static int quadrant(double dx, double dy)
@@ -57,8 +60,8 @@ public static int quadrant(double dx, double dy)
   /**
    * Returns the quadrant of a directed line segment from p0 to p1.
    * 
-   * Note: using this method is more robust than using {@link #quadrant(double, double)
-   * if that requires subtractions to compute vector components. 
+   * This method is more robust than {@link #quadrant(double, double)
+   * if using that requires subtractions to compute vector components. 
    * 
    * @throws IllegalArgumentException if the points are equal
    */

modules/core/src/main/java/org/locationtech/jts/geomgraph/EdgeEnd.java

@@ -57,9 +57,9 @@ protected void init(Coordinate p0, Coordinate p1)
   {
     this.p0 = p0;
     this.p1 = p1;
+    quadrant = Quadrant.quadrant(p0, p1);
     dx = p1.x - p0.x;
     dy = p1.y - p0.y;
-    quadrant = Quadrant.quadrant(dx, dy);
     Assert.isTrue(! (dx == 0 && dy == 0), "EdgeEnd with identical endpoints found");
   }
 

modules/core/src/main/java/org/locationtech/jts/planargraph/DirectedEdge.java

@@ -75,9 +75,9 @@ public DirectedEdge(Node from, Node to, Coordinate directionPt, boolean edgeDire
     this.edgeDirection = edgeDirection;
     p0 = from.getCoordinate();
     p1 = directionPt;
+    quadrant = Quadrant.quadrant(p0, p1);
     double dx = p1.x - p0.x;
     double dy = p1.y - p0.y;
-    quadrant = Quadrant.quadrant(dx, dy);
     angle = Math.atan2(dy, dx);
     //Assert.isTrue(! (dx == 0 && dy == 0), "EdgeEnd with identical endpoints found");
   }