patch to import Jon Smirl's work from Bitkeeper

1 files changed, 938 insertions, 0 deletions

diff --git a/src/glu/mini/polytest.c b/src/glu/mini/polytest.c
new file mode 100644
index 00000000000..52f272a3cb4
--- /dev/null
+++ b/src/glu/mini/polytest.c
@@ -0,0 +1,938 @@
+/* $Id: polytest.c,v 1.2 2003/08/22 20:11:43 brianp Exp $ */
+
+/*
+ * Mesa 3-D graphics library
+ * Version:  3.3
+ * Copyright (C) 1995-2000  Brian Paul
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the Free
+ * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+
+/*
+ * This file is part of the polygon tesselation code contributed by
+ * Bogdan Sikorski
+ */
+
+
+#ifdef PC_HEADER
+#include "all.h"
+#else
+#include <math.h>
+#include <stdlib.h>
+#include "gluP.h"
+#include "tess.h"
+#endif
+
+
+
+static GLenum store_polygon_as_contour(GLUtriangulatorObj *);
+static void free_current_polygon(tess_polygon *);
+static void prepare_projection_info(GLUtriangulatorObj *);
+static GLdouble twice_the_polygon_area(tess_vertex *, tess_vertex *);
+static GLenum verify_edge_vertex_intersections(GLUtriangulatorObj *);
+void tess_find_contour_hierarchies(GLUtriangulatorObj *);
+static GLenum test_for_overlapping_contours(GLUtriangulatorObj *);
+static GLenum contours_overlap(tess_contour *, tess_polygon *);
+static GLenum is_contour_contained_in(tess_contour *, tess_contour *);
+static void add_new_exterior(GLUtriangulatorObj *, tess_contour *);
+static void add_new_interior(GLUtriangulatorObj *, tess_contour *,
+			     tess_contour *);
+static void add_interior_with_hierarchy_check(GLUtriangulatorObj *,
+					      tess_contour *, tess_contour *);
+static void reverse_hierarchy_and_add_exterior(GLUtriangulatorObj *,
+					       tess_contour *,
+					       tess_contour *);
+static GLboolean point_in_polygon(tess_contour *, GLdouble, GLdouble);
+static void shift_interior_to_exterior(GLUtriangulatorObj *, tess_contour *);
+static void add_exterior_with_check(GLUtriangulatorObj *, tess_contour *,
+				    tess_contour *);
+static GLenum cut_out_hole(GLUtriangulatorObj *, tess_contour *,
+			   tess_contour *);
+static GLenum merge_hole_with_contour(GLUtriangulatorObj *,
+				      tess_contour *, tess_contour *,
+				      tess_vertex *, tess_vertex *);
+
+static GLenum
+find_normal(GLUtriangulatorObj * tobj)
+{
+   tess_polygon *polygon = tobj->current_polygon;
+   tess_vertex *va, *vb, *vc;
+   GLdouble A, B, C;
+   GLdouble A0, A1, A2, B0, B1, B2;
+
+   va = polygon->vertices;
+   vb = va->next;
+   A0 = vb->location[0] - va->location[0];
+   A1 = vb->location[1] - va->location[1];
+   A2 = vb->location[2] - va->location[2];
+   for (vc = vb->next; vc != va; vc = vc->next) {
+      B0 = vc->location[0] - va->location[0];
+      B1 = vc->location[1] - va->location[1];
+      B2 = vc->location[2] - va->location[2];
+      A = A1 * B2 - A2 * B1;
+      B = A2 * B0 - A0 * B2;
+      C = A0 * B1 - A1 * B0;
+      if (fabs(A) > EPSILON || fabs(B) > EPSILON || fabs(C) > EPSILON) {
+	 polygon->A = A;
+	 polygon->B = B;
+	 polygon->C = C;
+	 polygon->D =
+	    -A * va->location[0] - B * va->location[1] - C * va->location[2];
+	 return GLU_NO_ERROR;
+      }
+   }
+   tess_call_user_error(tobj, GLU_TESS_ERROR7);
+   return GLU_ERROR;
+}
+
+void
+tess_test_polygon(GLUtriangulatorObj * tobj)
+{
+   tess_polygon *polygon = tobj->current_polygon;
+
+   /* any vertices defined? */
+   if (polygon->vertex_cnt < 3) {
+      free_current_polygon(polygon);
+      return;
+   }
+   /* wrap pointers */
+   polygon->last_vertex->next = polygon->vertices;
+   polygon->vertices->previous = polygon->last_vertex;
+   /* determine the normal */
+   if (find_normal(tobj) == GLU_ERROR)
+      return;
+   /* compare the normals of previously defined contours and this one */
+   /* first contour define ? */
+   if (tobj->contours == NULL) {
+      tobj->A = polygon->A;
+      tobj->B = polygon->B;
+      tobj->C = polygon->C;
+      tobj->D = polygon->D;
+      /* determine the best projection to use */
+      if (fabs(polygon->A) > fabs(polygon->B))
+	 if (fabs(polygon->A) > fabs(polygon->C))
+	    tobj->projection = OYZ;
+	 else
+	    tobj->projection = OXY;
+      else if (fabs(polygon->B) > fabs(polygon->C))
+	 tobj->projection = OXZ;
+      else
+	 tobj->projection = OXY;
+   }
+   else {
+      GLdouble a[3], b[3];
+      tess_vertex *vertex = polygon->vertices;
+
+      a[0] = tobj->A;
+      a[1] = tobj->B;
+      a[2] = tobj->C;
+      b[0] = polygon->A;
+      b[1] = polygon->B;
+      b[2] = polygon->C;
+
+      /* compare the normals */
+      if (fabs(a[1] * b[2] - a[2] * b[1]) > EPSILON ||
+	  fabs(a[2] * b[0] - a[0] * b[2]) > EPSILON ||
+	  fabs(a[0] * b[1] - a[1] * b[0]) > EPSILON) {
+	 /* not coplanar */
+	 tess_call_user_error(tobj, GLU_TESS_ERROR9);
+	 return;
+      }
+      /* the normals are parallel - test for plane equation */
+      if (fabs(a[0] * vertex->location[0] + a[1] * vertex->location[1] +
+	       a[2] * vertex->location[2] + tobj->D) > EPSILON) {
+	 /* not the same plane */
+	 tess_call_user_error(tobj, GLU_TESS_ERROR9);
+	 return;
+      }
+   }
+   prepare_projection_info(tobj);
+   if (verify_edge_vertex_intersections(tobj) == GLU_ERROR)
+      return;
+   if (test_for_overlapping_contours(tobj) == GLU_ERROR)
+      return;
+   if (store_polygon_as_contour(tobj) == GLU_ERROR)
+      return;
+}
+
+static GLenum
+test_for_overlapping_contours(GLUtriangulatorObj * tobj)
+{
+   tess_contour *contour;
+   tess_polygon *polygon;
+
+   polygon = tobj->current_polygon;
+   for (contour = tobj->contours; contour != NULL; contour = contour->next)
+      if (contours_overlap(contour, polygon) != GLU_NO_ERROR) {
+	 tess_call_user_error(tobj, GLU_TESS_ERROR5);
+	 return GLU_ERROR;
+      }
+   return GLU_NO_ERROR;
+}
+
+static GLenum
+store_polygon_as_contour(GLUtriangulatorObj * tobj)
+{
+   tess_polygon *polygon = tobj->current_polygon;
+   tess_contour *contour = tobj->contours;
+
+   /* the first contour defined */
+   if (contour == NULL) {
+      if ((contour = (tess_contour *) malloc(sizeof(tess_contour))) == NULL) {
+	 tess_call_user_error(tobj, GLU_OUT_OF_MEMORY);
+	 free_current_polygon(polygon);
+	 return GLU_ERROR;
+      }
+      tobj->contours = tobj->last_contour = contour;
+      contour->next = contour->previous = NULL;
+   }
+   else {
+      if ((contour = (tess_contour *) malloc(sizeof(tess_contour))) == NULL) {
+	 tess_call_user_error(tobj, GLU_OUT_OF_MEMORY);
+	 free_current_polygon(polygon);
+	 return GLU_ERROR;
+      }
+      contour->previous = tobj->last_contour;
+      tobj->last_contour->next = contour;
+      tobj->last_contour = contour;
+      contour->next = NULL;
+   }
+   /* mark all vertices in new contour as not special */
+   /* and all are boundary edges */
+   {
+      tess_vertex *vertex;
+      GLuint vertex_cnt, i;
+
+      for (vertex = polygon->vertices, i = 0, vertex_cnt =
+	   polygon->vertex_cnt; i < vertex_cnt; vertex = vertex->next, i++) {
+	 vertex->shadow_vertex = NULL;
+	 vertex->edge_flag = GL_TRUE;
+      }
+   }
+   contour->vertex_cnt = polygon->vertex_cnt;
+   contour->area = polygon->area;
+   contour->orientation = polygon->orientation;
+   contour->type = GLU_UNKNOWN;
+   contour->vertices = polygon->vertices;
+   contour->last_vertex = polygon->last_vertex;
+   polygon->vertices = polygon->last_vertex = NULL;
+   polygon->vertex_cnt = 0;
+   ++(tobj->contour_cnt);
+   return GLU_NO_ERROR;
+}
+
+static void
+free_current_polygon(tess_polygon * polygon)
+{
+   tess_vertex *vertex, *vertex_tmp;
+   GLuint i;
+
+   /* free current_polygon structures */
+   for (vertex = polygon->vertices, i = 0; i < polygon->vertex_cnt; i++) {
+      vertex_tmp = vertex->next;
+      free(vertex);
+      vertex = vertex_tmp;
+   }
+   polygon->vertices = polygon->last_vertex = NULL;
+   polygon->vertex_cnt = 0;
+}
+
+static void
+prepare_projection_info(GLUtriangulatorObj * tobj)
+{
+   tess_polygon *polygon = tobj->current_polygon;
+   tess_vertex *vertex, *last_vertex_ptr;
+   GLdouble area;
+
+   last_vertex_ptr = polygon->last_vertex;
+   switch (tobj->projection) {
+   case OXY:
+      for (vertex = polygon->vertices; vertex != last_vertex_ptr;
+	   vertex = vertex->next) {
+	 vertex->x = vertex->location[0];
+	 vertex->y = vertex->location[1];
+      }
+      last_vertex_ptr->x = last_vertex_ptr->location[0];
+      last_vertex_ptr->y = last_vertex_ptr->location[1];
+      break;
+   case OXZ:
+      for (vertex = polygon->vertices; vertex != last_vertex_ptr;
+	   vertex = vertex->next) {
+	 vertex->x = vertex->location[0];
+	 vertex->y = vertex->location[2];
+      }
+      last_vertex_ptr->x = last_vertex_ptr->location[0];
+      last_vertex_ptr->y = last_vertex_ptr->location[2];
+      break;
+   case OYZ:
+      for (vertex = polygon->vertices; vertex != last_vertex_ptr;
+	   vertex = vertex->next) {
+	 vertex->x = vertex->location[1];
+	 vertex->y = vertex->location[2];
+      }
+      last_vertex_ptr->x = last_vertex_ptr->location[1];
+      last_vertex_ptr->y = last_vertex_ptr->location[2];
+      break;
+   }
+   area = twice_the_polygon_area(polygon->vertices, polygon->last_vertex);
+   if (area >= 0.0) {
+      polygon->orientation = GLU_CCW;
+      polygon->area = area;
+   }
+   else {
+      polygon->orientation = GLU_CW;
+      polygon->area = -area;
+   }
+}
+
+static GLdouble
+twice_the_polygon_area(tess_vertex * vertex, tess_vertex * last_vertex)
+{
+   tess_vertex *next;
+   GLdouble area, x, y;
+
+   area = 0.0;
+   x = vertex->x;
+   y = vertex->y;
+   vertex = vertex->next;
+   for (; vertex != last_vertex; vertex = vertex->next) {
+      next = vertex->next;
+      area +=
+	 (vertex->x - x) * (next->y - y) - (vertex->y - y) * (next->x - x);
+   }
+   return area;
+}
+
+/* test if edges ab and cd intersect */
+/* if not return GLU_NO_ERROR, else if cross return GLU_TESS_ERROR8, */
+/* else if adjacent return GLU_TESS_ERROR4 */
+static GLenum
+edge_edge_intersect(tess_vertex * a,
+		    tess_vertex * b, tess_vertex * c, tess_vertex * d)
+{
+   GLdouble denom, r, s;
+   GLdouble xba, ydc, yba, xdc, yac, xac;
+
+   xba = b->x - a->x;
+   yba = b->y - a->y;
+   xdc = d->x - c->x;
+   ydc = d->y - c->y;
+   xac = a->x - c->x;
+   yac = a->y - c->y;
+   denom = xba * ydc - yba * xdc;
+   r = yac * xdc - xac * ydc;
+   /* parallel? */
+   if (fabs(denom) < EPSILON) {
+      if (fabs(r) < EPSILON) {
+	 /* colinear */
+	 if (fabs(xba) < EPSILON) {
+	    /* compare the Y coordinate */
+	    if (yba > 0.0) {
+	       if (
+		   (fabs(a->y - c->y) < EPSILON
+		    && fabs(c->y - b->y) < EPSILON)
+		   || (fabs(a->y - d->y) < EPSILON
+		       && fabs(d->y - b->y) <
+		       EPSILON)) return GLU_TESS_ERROR4;
+
+	    }
+	    else {
+	       if (
+		   (fabs(b->y - c->y) < EPSILON
+		    && fabs(c->y - a->y) < EPSILON)
+		   || (fabs(b->y - d->y) < EPSILON
+		       && fabs(d->y - a->y) <
+		       EPSILON)) return GLU_TESS_ERROR4;
+	    }
+	 }
+	 else {
+	    /* compare the X coordinate */
+	    if (xba > 0.0) {
+	       if (
+		   (fabs(a->x - c->x) < EPSILON
+		    && fabs(c->x - b->x) < EPSILON)
+		   || (fabs(a->x - d->x) < EPSILON
+		       && fabs(d->x - b->x) <
+		       EPSILON)) return GLU_TESS_ERROR4;
+	    }
+	    else {
+	       if (
+		   (fabs(b->x - c->x) < EPSILON
+		    && fabs(c->x - a->x) < EPSILON)
+		   || (fabs(b->x - d->x) < EPSILON
+		       && fabs(d->x - a->x) <
+		       EPSILON)) return GLU_TESS_ERROR4;
+	    }
+	 }
+      }
+      return GLU_NO_ERROR;
+   }
+   r /= denom;
+   s = (yac * xba - xac * yba) / denom;
+   /* test if one vertex lies on other edge */
+   if (((fabs(r) < EPSILON || (r < 1.0 + EPSILON && r > 1.0 - EPSILON)) &&
+	s > -EPSILON && s < 1.0 + EPSILON) ||
+       ((fabs(s) < EPSILON || (s < 1.0 + EPSILON && s > 1.0 - EPSILON)) &&
+	r > -EPSILON && r < 1.0 + EPSILON)) {
+      return GLU_TESS_ERROR4;
+   }
+   /* test for crossing */
+   if (r > -EPSILON && r < 1.0 + EPSILON && s > -EPSILON && s < 1.0 + EPSILON) {
+      return GLU_TESS_ERROR8;
+   }
+   return GLU_NO_ERROR;
+}
+
+static GLenum
+verify_edge_vertex_intersections(GLUtriangulatorObj * tobj)
+{
+   tess_polygon *polygon = tobj->current_polygon;
+   tess_vertex *vertex1, *last_vertex, *vertex2;
+   GLenum test;
+
+   last_vertex = polygon->last_vertex;
+   vertex1 = last_vertex;
+   for (vertex2 = vertex1->next->next;
+	vertex2->next != last_vertex; vertex2 = vertex2->next) {
+      test = edge_edge_intersect(vertex1, vertex1->next, vertex2,
+				 vertex2->next);
+      if (test != GLU_NO_ERROR) {
+	 tess_call_user_error(tobj, test);
+	 return GLU_ERROR;
+      }
+   }
+   for (vertex1 = polygon->vertices;
+	vertex1->next->next != last_vertex; vertex1 = vertex1->next) {
+      for (vertex2 = vertex1->next->next;
+	   vertex2 != last_vertex; vertex2 = vertex2->next) {
+	 test = edge_edge_intersect(vertex1, vertex1->next, vertex2,
+				    vertex2->next);
+	 if (test != GLU_NO_ERROR) {
+	    tess_call_user_error(tobj, test);
+	    return GLU_ERROR;
+	 }
+      }
+   }
+   return GLU_NO_ERROR;
+}
+
+static int
+#ifdef WIN32
+  __cdecl
+#endif
+area_compare(const void *a, const void *b)
+{
+   GLdouble area1, area2;
+
+   area1 = (*((tess_contour **) a))->area;
+   area2 = (*((tess_contour **) b))->area;
+   if (area1 < area2)
+      return 1;
+   if (area1 > area2)
+      return -1;
+   return 0;
+}
+
+void
+tess_find_contour_hierarchies(GLUtriangulatorObj * tobj)
+{
+   tess_contour **contours;	/* dinamic array of pointers */
+   tess_contour *tmp_contour_ptr = tobj->contours;
+   GLuint cnt, i;
+   GLenum result;
+   GLboolean hierarchy_changed;
+
+   /* any contours? */
+   if (tobj->contour_cnt < 2) {
+      tobj->contours->type = GLU_EXTERIOR;
+      return;
+   }
+   if ((contours = (tess_contour **)
+	malloc(sizeof(tess_contour *) * (tobj->contour_cnt))) == NULL) {
+      tess_call_user_error(tobj, GLU_OUT_OF_MEMORY);
+      return;
+   }
+   for (tmp_contour_ptr = tobj->contours, cnt = 0;
+	tmp_contour_ptr != NULL; tmp_contour_ptr = tmp_contour_ptr->next)
+      contours[cnt++] = tmp_contour_ptr;
+   /* now sort the contours in decreasing area size order */
+   qsort((void *) contours, (size_t) cnt, (size_t) sizeof(tess_contour *),
+	 area_compare);
+   /* we leave just the first contour - remove others from list */
+   tobj->contours = contours[0];
+   tobj->contours->next = tobj->contours->previous = NULL;
+   tobj->last_contour = tobj->contours;
+   tobj->contour_cnt = 1;
+   /* first contour is the one with greatest area */
+   /* must be EXTERIOR */
+   tobj->contours->type = GLU_EXTERIOR;
+   tmp_contour_ptr = tobj->contours;
+   /* now we play! */
+   for (i = 1; i < cnt; i++) {
+      hierarchy_changed = GL_FALSE;
+      for (tmp_contour_ptr = tobj->contours;
+	   tmp_contour_ptr != NULL; tmp_contour_ptr = tmp_contour_ptr->next) {
+	 if (tmp_contour_ptr->type == GLU_EXTERIOR) {
+	    /* check if contour completely contained in EXTERIOR */
+	    result = is_contour_contained_in(tmp_contour_ptr, contours[i]);
+	    switch (result) {
+	    case GLU_INTERIOR:
+	       /* now we have to check if contour is inside interiors */
+	       /* or not */
+	       /* any interiors? */
+	       if (tmp_contour_ptr->next != NULL &&
+		   tmp_contour_ptr->next->type == GLU_INTERIOR) {
+		  /* for all interior, check if inside any of them */
+		  /* if not inside any of interiors, its another */
+		  /* interior */
+		  /* or it may contain some interiors, then change */
+		  /* the contained interiors to exterior ones */
+		  add_interior_with_hierarchy_check(tobj,
+						    tmp_contour_ptr,
+						    contours[i]);
+	       }
+	       else {
+		  /* not in interior, add as new interior contour */
+		  add_new_interior(tobj, tmp_contour_ptr, contours[i]);
+	       }
+	       hierarchy_changed = GL_TRUE;
+	       break;
+	    case GLU_EXTERIOR:
+	       /* ooops, the marked as EXTERIOR (contours[i]) is */
+	       /* actually an interior of tmp_contour_ptr */
+	       /*  reverse the local hierarchy */
+	       reverse_hierarchy_and_add_exterior(tobj, tmp_contour_ptr,
+						  contours[i]);
+	       hierarchy_changed = GL_TRUE;
+	       break;
+	    case GLU_NO_ERROR:
+	       break;
+	    default:
+	       abort();
+	    }
+	 }
+	 if (hierarchy_changed)
+	    break;		/* break from for loop */
+      }
+      if (hierarchy_changed == GL_FALSE) {
+	 /* disjoint with all contours, add to contour list */
+	 add_new_exterior(tobj, contours[i]);
+      }
+   }
+   free(contours);
+}
+
+/* returns GLU_INTERIOR if inner is completey enclosed within outer */
+/* returns GLU_EXTERIOR if outer is completely enclosed within inner */
+/* returns GLU_NO_ERROR if contours are disjoint */
+static GLenum
+is_contour_contained_in(tess_contour * outer, tess_contour * inner)
+{
+   GLenum relation_flag;
+
+   /* set relation_flag to relation of containment of first inner vertex */
+   /* regarding outer contour */
+   if (point_in_polygon(outer, inner->vertices->x, inner->vertices->y))
+      relation_flag = GLU_INTERIOR;
+   else
+      relation_flag = GLU_EXTERIOR;
+   if (relation_flag == GLU_INTERIOR)
+      return GLU_INTERIOR;
+   if (point_in_polygon(inner, outer->vertices->x, outer->vertices->y))
+      return GLU_EXTERIOR;
+   return GLU_NO_ERROR;
+}
+
+static GLboolean
+point_in_polygon(tess_contour * contour, GLdouble x, GLdouble y)
+{
+   tess_vertex *v1, *v2;
+   GLuint i, vertex_cnt;
+   GLdouble xp1, yp1, xp2, yp2;
+   GLboolean tst;
+
+   tst = GL_FALSE;
+   v1 = contour->vertices;
+   v2 = contour->vertices->previous;
+   for (i = 0, vertex_cnt = contour->vertex_cnt; i < vertex_cnt; i++) {
+      xp1 = v1->x;
+      yp1 = v1->y;
+      xp2 = v2->x;
+      yp2 = v2->y;
+      if ((((yp1 <= y) && (y < yp2)) || ((yp2 <= y) && (y < yp1))) &&
+	  (x < (xp2 - xp1) * (y - yp1) / (yp2 - yp1) + xp1))
+	 tst = (tst == GL_FALSE ? GL_TRUE : GL_FALSE);
+      v2 = v1;
+      v1 = v1->next;
+   }
+   return tst;
+}
+
+static GLenum
+contours_overlap(tess_contour * contour, tess_polygon * polygon)
+{
+   tess_vertex *vertex1, *vertex2;
+   GLuint vertex1_cnt, vertex2_cnt, i, j;
+   GLenum test;
+
+   vertex1 = contour->vertices;
+   vertex2 = polygon->vertices;
+   vertex1_cnt = contour->vertex_cnt;
+   vertex2_cnt = polygon->vertex_cnt;
+   for (i = 0; i < vertex1_cnt; vertex1 = vertex1->next, i++) {
+      for (j = 0; j < vertex2_cnt; vertex2 = vertex2->next, j++)
+	 if ((test = edge_edge_intersect(vertex1, vertex1->next, vertex2,
+					 vertex2->next)) != GLU_NO_ERROR)
+	    return test;
+   }
+   return GLU_NO_ERROR;
+}
+
+static void
+add_new_exterior(GLUtriangulatorObj * tobj, tess_contour * contour)
+{
+   contour->type = GLU_EXTERIOR;
+   contour->next = NULL;
+   contour->previous = tobj->last_contour;
+   tobj->last_contour->next = contour;
+   tobj->last_contour = contour;
+}
+
+static void
+add_new_interior(GLUtriangulatorObj * tobj,
+		 tess_contour * outer, tess_contour * contour)
+{
+   contour->type = GLU_INTERIOR;
+   contour->next = outer->next;
+   contour->previous = outer;
+   if (outer->next != NULL)
+      outer->next->previous = contour;
+   outer->next = contour;
+   if (tobj->last_contour == outer)
+      tobj->last_contour = contour;
+}
+
+static void
+add_interior_with_hierarchy_check(GLUtriangulatorObj * tobj,
+				  tess_contour * outer,
+				  tess_contour * contour)
+{
+   tess_contour *ptr;
+
+   /* for all interiors of outer check if they are interior of contour */
+   /* if so, change that interior to exterior and move it of of the */
+   /* interior sequence */
+   if (outer->next != NULL && outer->next->type == GLU_INTERIOR) {
+      GLenum test;
+
+      for (ptr = outer->next; ptr != NULL && ptr->type == GLU_INTERIOR;
+	   ptr = ptr->next) {
+	 test = is_contour_contained_in(ptr, contour);
+	 switch (test) {
+	 case GLU_INTERIOR:
+	    /* contour is contained in one of the interiors */
+	    /* check if possibly contained in other exteriors */
+	    /* move ptr to first EXTERIOR */
+	    for (; ptr != NULL && ptr->type == GLU_INTERIOR; ptr = ptr->next);
+	    if (ptr == NULL)
+	       /* another exterior */
+	       add_new_exterior(tobj, contour);
+	    else
+	       add_exterior_with_check(tobj, ptr, contour);
+	    return;
+	 case GLU_EXTERIOR:
+	    /* one of the interiors is contained in the contour */
+	    /* change it to EXTERIOR, and shift it away from the */
+	    /* interior sequence */
+	    shift_interior_to_exterior(tobj, ptr);
+	    break;
+	 case GLU_NO_ERROR:
+	    /* disjoint */
+	    break;
+	 default:
+	    abort();
+	 }
+      }
+   }
+   /* add contour to the interior sequence */
+   add_new_interior(tobj, outer, contour);
+}
+
+static void
+reverse_hierarchy_and_add_exterior(GLUtriangulatorObj * tobj,
+				   tess_contour * outer,
+				   tess_contour * contour)
+{
+   tess_contour *ptr;
+
+   /* reverse INTERIORS to EXTERIORS */
+   /* any INTERIORS? */
+   if (outer->next != NULL && outer->next->type == GLU_INTERIOR)
+      for (ptr = outer->next; ptr != NULL && ptr->type == GLU_INTERIOR;
+	   ptr = ptr->next) ptr->type = GLU_EXTERIOR;
+   /* the outer now becomes inner */
+   outer->type = GLU_INTERIOR;
+   /* contour is the EXTERIOR */
+   contour->next = outer;
+   if (tobj->contours == outer) {
+      /* first contour beeing reversed */
+      contour->previous = NULL;
+      tobj->contours = contour;
+   }
+   else {
+      outer->previous->next = contour;
+      contour->previous = outer->previous;
+   }
+   outer->previous = contour;
+}
+
+static void
+shift_interior_to_exterior(GLUtriangulatorObj * tobj, tess_contour * contour)
+{
+   contour->previous->next = contour->next;
+   if (contour->next != NULL)
+      contour->next->previous = contour->previous;
+   else
+      tobj->last_contour = contour->previous;
+}
+
+static void
+add_exterior_with_check(GLUtriangulatorObj * tobj,
+			tess_contour * outer, tess_contour * contour)
+{
+   GLenum test;
+
+   /* this contour might be interior to further exteriors - check */
+   /* if not, just add as a new exterior */
+   for (; outer != NULL && outer->type == GLU_EXTERIOR; outer = outer->next) {
+      test = is_contour_contained_in(outer, contour);
+      switch (test) {
+      case GLU_INTERIOR:
+	 /* now we have to check if contour is inside interiors */
+	 /* or not */
+	 /* any interiors? */
+	 if (outer->next != NULL && outer->next->type == GLU_INTERIOR) {
+	    /* for all interior, check if inside any of them */
+	    /* if not inside any of interiors, its another */
+	    /* interior */
+	    /* or it may contain some interiors, then change */
+	    /* the contained interiors to exterior ones */
+	    add_interior_with_hierarchy_check(tobj, outer, contour);
+	 }
+	 else {
+	    /* not in interior, add as new interior contour */
+	    add_new_interior(tobj, outer, contour);
+	 }
+	 return;
+      case GLU_NO_ERROR:
+	 /* disjoint */
+	 break;
+      default:
+	 abort();
+      }
+   }
+   /* add contour to the exterior sequence */
+   add_new_exterior(tobj, contour);
+}
+
+void
+tess_handle_holes(GLUtriangulatorObj * tobj)
+{
+   tess_contour *contour, *hole;
+   GLenum exterior_orientation;
+
+   /* verify hole orientation */
+   for (contour = tobj->contours; contour != NULL;) {
+      exterior_orientation = contour->orientation;
+      for (contour = contour->next;
+	   contour != NULL && contour->type == GLU_INTERIOR;
+	   contour = contour->next) {
+	 if (contour->orientation == exterior_orientation) {
+	    tess_call_user_error(tobj, GLU_TESS_ERROR5);
+	    return;
+	 }
+      }
+   }
+   /* now cut-out holes */
+   for (contour = tobj->contours; contour != NULL;) {
+      hole = contour->next;
+      while (hole != NULL && hole->type == GLU_INTERIOR) {
+	 if (cut_out_hole(tobj, contour, hole) == GLU_ERROR)
+	    return;
+	 hole = contour->next;
+      }
+      contour = contour->next;
+   }
+}
+
+static GLenum
+cut_out_hole(GLUtriangulatorObj * tobj,
+	     tess_contour * contour, tess_contour * hole)
+{
+   tess_contour *tmp_hole;
+   tess_vertex *v1, *v2, *tmp_vertex;
+   GLuint vertex1_cnt, vertex2_cnt, tmp_vertex_cnt;
+   GLuint i, j, k;
+   GLenum test = 0;
+
+   /* find an edge connecting contour and hole not intersecting any other */
+   /* edge belonging to either the contour or any of the other holes */
+   for (v1 = contour->vertices, vertex1_cnt = contour->vertex_cnt, i = 0;
+	i < vertex1_cnt; i++, v1 = v1->next) {
+      for (v2 = hole->vertices, vertex2_cnt = hole->vertex_cnt, j = 0;
+	   j < vertex2_cnt; j++, v2 = v2->next) {
+	 /* does edge (v1,v2) intersect any edge of contour */
+	 for (tmp_vertex = contour->vertices, tmp_vertex_cnt =
+	      contour->vertex_cnt, k = 0; k < tmp_vertex_cnt;
+	      tmp_vertex = tmp_vertex->next, k++) {
+	    /* skip edge tests for edges directly connected */
+	    if (v1 == tmp_vertex || v1 == tmp_vertex->next)
+	       continue;
+	    test = edge_edge_intersect(v1, v2, tmp_vertex, tmp_vertex->next);
+	    if (test != GLU_NO_ERROR)
+	       break;
+	 }
+	 if (test == GLU_NO_ERROR) {
+	    /* does edge (v1,v2) intersect any edge of hole */
+	    for (tmp_vertex = hole->vertices,
+		 tmp_vertex_cnt = hole->vertex_cnt, k = 0;
+		 k < tmp_vertex_cnt; tmp_vertex = tmp_vertex->next, k++) {
+	       /* skip edge tests for edges directly connected */
+	       if (v2 == tmp_vertex || v2 == tmp_vertex->next)
+		  continue;
+	       test =
+		  edge_edge_intersect(v1, v2, tmp_vertex, tmp_vertex->next);
+	       if (test != GLU_NO_ERROR)
+		  break;
+	    }
+	    if (test == GLU_NO_ERROR) {
+	       /* does edge (v1,v2) intersect any other hole? */
+	       for (tmp_hole = hole->next;
+		    tmp_hole != NULL && tmp_hole->type == GLU_INTERIOR;
+		    tmp_hole = tmp_hole->next) {
+		  /* does edge (v1,v2) intersect any edge of hole */
+		  for (tmp_vertex = tmp_hole->vertices,
+		       tmp_vertex_cnt = tmp_hole->vertex_cnt, k = 0;
+		       k < tmp_vertex_cnt; tmp_vertex = tmp_vertex->next, k++) {
+		     test = edge_edge_intersect(v1, v2, tmp_vertex,
+						tmp_vertex->next);
+		     if (test != GLU_NO_ERROR)
+			break;
+		  }
+		  if (test != GLU_NO_ERROR)
+		     break;
+	       }
+	    }
+	 }
+	 if (test == GLU_NO_ERROR) {
+	    /* edge (v1,v2) is good for eliminating the hole */
+	    if (merge_hole_with_contour(tobj, contour, hole, v1, v2)
+		== GLU_NO_ERROR)
+	       return GLU_NO_ERROR;
+	    else
+	       return GLU_ERROR;
+	 }
+      }
+   }
+   /* other holes are blocking all possible connections of hole */
+   /* with contour, we shift this hole as the last hole and retry */
+   for (tmp_hole = hole;
+	tmp_hole != NULL && tmp_hole->type == GLU_INTERIOR;
+	tmp_hole = tmp_hole->next);
+   contour->next = hole->next;
+   hole->next->previous = contour;
+   if (tmp_hole == NULL) {
+      /* last EXTERIOR contour, shift hole as last contour */
+      hole->next = NULL;
+      hole->previous = tobj->last_contour;
+      tobj->last_contour->next = hole;
+      tobj->last_contour = hole;
+   }
+   else {
+      tmp_hole->previous->next = hole;
+      hole->previous = tmp_hole->previous;
+      tmp_hole->previous = hole;
+      hole->next = tmp_hole;
+   }
+   hole = contour->next;
+   /* try once again - recurse */
+   return cut_out_hole(tobj, contour, hole);
+}
+
+static GLenum
+merge_hole_with_contour(GLUtriangulatorObj * tobj,
+			tess_contour * contour,
+			tess_contour * hole,
+			tess_vertex * v1, tess_vertex * v2)
+{
+   tess_vertex *v1_new, *v2_new;
+
+   /* make copies of v1 and v2, place them respectively after their originals */
+   if ((v1_new = (tess_vertex *) malloc(sizeof(tess_vertex))) == NULL) {
+      tess_call_user_error(tobj, GLU_OUT_OF_MEMORY);
+      return GLU_ERROR;
+   }
+   if ((v2_new = (tess_vertex *) malloc(sizeof(tess_vertex))) == NULL) {
+      tess_call_user_error(tobj, GLU_OUT_OF_MEMORY);
+      return GLU_ERROR;
+   }
+   v1_new->edge_flag = GL_TRUE;
+   v1_new->data = v1->data;
+   v1_new->location[0] = v1->location[0];
+   v1_new->location[1] = v1->location[1];
+   v1_new->location[2] = v1->location[2];
+   v1_new->x = v1->x;
+   v1_new->y = v1->y;
+   v1_new->shadow_vertex = v1;
+   v1->shadow_vertex = v1_new;
+   v1_new->next = v1->next;
+   v1_new->previous = v1;
+   v1->next->previous = v1_new;
+   v1->next = v1_new;
+   v2_new->edge_flag = GL_TRUE;
+   v2_new->data = v2->data;
+   v2_new->location[0] = v2->location[0];
+   v2_new->location[1] = v2->location[1];
+   v2_new->location[2] = v2->location[2];
+   v2_new->x = v2->x;
+   v2_new->y = v2->y;
+   v2_new->shadow_vertex = v2;
+   v2->shadow_vertex = v2_new;
+   v2_new->next = v2->next;
+   v2_new->previous = v2;
+   v2->next->previous = v2_new;
+   v2->next = v2_new;
+   /* link together the two lists */
+   v1->next = v2_new;
+   v2_new->previous = v1;
+   v2->next = v1_new;
+   v1_new->previous = v2;
+   /* update the vertex count of the contour */
+   contour->vertex_cnt += hole->vertex_cnt + 2;
+   /* remove the INTERIOR contour */
+   contour->next = hole->next;
+   if (hole->next != NULL)
+      hole->next->previous = contour;
+   free(hole);
+   /* update tobj structure */
+   --(tobj->contour_cnt);
+   if (contour->last_vertex == v1)
+      contour->last_vertex = v1_new;
+   /* mark two vertices with edge_flag */
+   v2->edge_flag = GL_FALSE;
+   v1->edge_flag = GL_FALSE;
+   return GLU_NO_ERROR;
+}