fix sline_sline_pos, add tests for degenerate polygons

Author: ggnmstr

Diff for: expected/poly.out

@@ -328,6 +328,15 @@ SELECT spoly '{(0d,0d),(10d,10d),(0d,10d),(10d,0d)}';
 ERROR:  spherepoly_from_array: a line segment overlaps or polygon too large
 LINE 1: SELECT spoly '{(0d,0d),(10d,10d),(0d,10d),(10d,0d)}';
                      ^
+--- degenerate polygons -----
+SELECT spoly '{(0d,1d),(0d,2d),(0d,3d)}';
+ERROR:  spherepoly_from_array: a line segment overlaps or polygon too large
+LINE 1: SELECT spoly '{(0d,1d),(0d,2d),(0d,3d)}';
+                     ^
+SELECT spoly '{(1d,0d),(2d,0d),(3d,0d)}';
+ERROR:  spherepoly_from_array: a line segment overlaps or polygon too large
+LINE 1: SELECT spoly '{(1d,0d),(2d,0d),(3d,0d)}';
+                     ^
 --- functions
 SELECT npoints( spoly '{(10d,0d),(10d,1d),(15d,0d)}');
  npoints 

Diff for: sql/poly.sql

@@ -86,6 +86,12 @@ SELECT spoly '{(10d,0d),(10d,1d)}';
 
 SELECT spoly '{(0d,0d),(10d,10d),(0d,10d),(10d,0d)}';
 
+--- degenerate polygons -----
+
+SELECT spoly '{(0d,1d),(0d,2d),(0d,3d)}';
+
+SELECT spoly '{(1d,0d),(2d,0d),(3d,0d)}';
+
 --- functions
 
 SELECT npoints( spoly '{(10d,0d),(10d,1d),(15d,0d)}');

Diff for: src/line.c

@@ -494,15 +494,6 @@ sline_sline_pos(const SLine *l1, const SLine *l2)
 	vector3d_spoint(&p[2], &v[1][0]);
 	vector3d_spoint(&p[3], &v[1][1]);
 
-	/* check connected lines */
-	if (FPgt(il2->length, 0.0) && (vector3d_eq(&v[0][0], &v[1][0]) ||
-								   vector3d_eq(&v[0][0], &v[1][1]) ||
-								   vector3d_eq(&v[0][1], &v[1][0]) ||
-								   vector3d_eq(&v[0][1], &v[1][1])))
-	{
-		return PGS_LINE_CONNECT;
-	}
-
 	/* Check, sl2 is at equator */
 	if (FPzero(p[2].lat) && FPzero(p[3].lat))
 	{
@@ -527,6 +518,15 @@ sline_sline_pos(const SLine *l1, const SLine *l2)
 		return PGS_LINE_AVOID;
 	}
 
+	/* check connected lines */
+	if (FPgt(il2->length, 0.0) && (vector3d_eq(&v[0][0], &v[1][0]) ||
+								   vector3d_eq(&v[0][0], &v[1][1]) ||
+								   vector3d_eq(&v[0][1], &v[1][0]) ||
+								   vector3d_eq(&v[0][1], &v[1][1])))
+	{
+		return PGS_LINE_CONNECT;
+	}
+
 	/* Now sl2 is not at equator */
 
 	if (FPle(il2->length, seg_length))