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 // see license file for original license.
 
 #ifndef tools_glutess_sweep
 #define tools_glutess_sweep
 
 #include "mesh"
 #include "dict"
 
 /* For each pair of adjacent edges crossing the sweep line, there is
  * an ActiveRegion to represent the region between them.  The active
  * regions are kept in sorted order in a dynamic dictionary.  As the
  * sweep line crosses each vertex, we update the affected regions.
  */
 
 struct ActiveRegion {
   GLUhalfEdge   *eUp;           /* upper edge, directed right to left */
   DictNode      *nodeUp;        /* dictionary node corresponding to eUp */
   int           windingNumber;  /* used to determine which regions are
                                  * inside the polygon */
   GLUboolean    inside;         /* is this region inside the polygon? */
   GLUboolean    sentinel;       /* marks fake edges at t = +/-infinity */
   GLUboolean    dirty;          /* marks regions where the upper or lower
                                  * edge has changed, but we haven't checked
                                  * whether they intersect yet */
   GLUboolean    fixUpperEdge;   /* marks temporary edges introduced when
                                  * we process a "right vertex" (one without
                                  * any edges leaving to the right) */
 };
 
 #define RegionBelow(r)  ((ActiveRegion *) dictKey(dictPred((r)->nodeUp)))
 #define RegionAbove(r)  ((ActiveRegion *) dictKey(dictSucc((r)->nodeUp)))
 
 ////////////////////////////////////////////////////////
 /// inlined C code : ///////////////////////////////////
 ////////////////////////////////////////////////////////
 
 #include "geom"
 #include "_tess"
 #include "priorityq"
 
 #define DebugEvent( tess )
 
 /*
  * Invariants for the Edge Dictionary.
  * - each pair of adjacent edges e2=Succ(e1) satisfies EdgeLeq(e1,e2)
  *   at any valid location of the sweep event
  * - if EdgeLeq(e2,e1) as well (at any valid sweep event), then e1 and e2
  *   share a common endpoint
  * - for each e, e->Dst has been processed, but not e->Org
  * - each edge e satisfies VertLeq(e->Dst,event) && VertLeq(event,e->Org)
  *   where "event" is the current sweep line event.
  * - no edge e has zero length
  *
  * Invariants for the Mesh (the processed portion).
  * - the portion of the mesh left of the sweep line is a planar graph,
  *   ie. there is *some* way to embed it in the plane
  * - no processed edge has zero length
  * - no two processed vertices have identical coordinates
  * - each "inside" region is monotone, ie. can be broken into two chains
  *   of monotonically increasing vertices according to VertLeq(v1,v2)
  *   - a non-invariant: these chains may intersect (very slightly)
  *
  * Invariants for the Sweep.
  * - if none of the edges incident to the event vertex have an activeRegion
  *   (ie. none of these edges are in the edge dictionary), then the vertex
  *   has only right-going edges.
  * - if an edge is marked "fixUpperEdge" (it is a temporary edge introduced
  *   by ConnectRightVertex), then it is the only right-going edge from
  *   its associated vertex.  (This says that these edges exist only
  *   when it is necessary.)
  */
 
 /* When we merge two edges into one, we need to compute the combined
  * winding of the new edge.
  */
 #define AddWinding(eDst,eSrc)   (eDst->winding += eSrc->winding, \
                                  eDst->Sym->winding += eSrc->Sym->winding)
 
 inline/*static*/ void static_SweepEvent( GLUtesselator *tess, GLUvertex *vEvent );
 inline/*static*/ void static_WalkDirtyRegions( GLUtesselator *tess, ActiveRegion *regUp );
 inline/*static*/ int static_CheckForRightSplice( GLUtesselator *tess, ActiveRegion *regUp );
 
 inline/*static*/ int static_EdgeLeq( GLUtesselator *tess, ActiveRegion *reg1,
                     ActiveRegion *reg2 )
 /*
  * Both edges must be directed from right to left (this is the canonical
  * direction for the upper edge of each region).
  *
  * The strategy is to evaluate a "t" value for each edge at the
  * current sweep line position, given by tess->event.  The calculations
  * are designed to be very stable, but of course they are not perfect.
  *
  * Special case: if both edge destinations are at the sweep event,
  * we sort the edges by slope (they would otherwise compare equally).
  */
 {
   GLUvertex *event = tess->event;
   GLUhalfEdge *e1, *e2;
   GLUdouble t1, t2;
 
   e1 = reg1->eUp;
   e2 = reg2->eUp;
 
   if( e1->Dst == event ) {
     if( e2->Dst == event ) {
       /* Two edges right of the sweep line which meet at the sweep event.
        * Sort them by slope.
        */
       if( VertLeq( e1->Org, e2->Org )) {
         return EdgeSign( e2->Dst, e1->Org, e2->Org ) <= 0;
       }
       return EdgeSign( e1->Dst, e2->Org, e1->Org ) >= 0;
     }
     return EdgeSign( e2->Dst, event, e2->Org ) <= 0;
   }
   if( e2->Dst == event ) {
     return EdgeSign( e1->Dst, event, e1->Org ) >= 0;
   }
 
   /* General case - compute signed distance *from* e1, e2 to event */
   t1 = EdgeEval( e1->Dst, event, e1->Org );
   t2 = EdgeEval( e2->Dst, event, e2->Org );
   return (t1 >= t2);
 }
 
 
 inline/*static*/ void static_DeleteRegion( GLUtesselator *tess, ActiveRegion *reg )
 {
   if( reg->fixUpperEdge ) {
     /* It was created with zero winding number, so it better be
      * deleted with zero winding number (ie. it better not get merged
      * with a real edge).
      */
     assert( reg->eUp->winding == 0 );
   }
   reg->eUp->activeRegion = NULL;
   dictDelete( tess->dict, reg->nodeUp ); /* __gl_dictListDelete */
   memFree( reg );
 }
 
 
 inline/*static*/ int static_FixUpperEdge( ActiveRegion *reg, GLUhalfEdge *newEdge )
 /*
  * Replace an upper edge which needs fixing (see ConnectRightVertex).
  */
 {
   assert( reg->fixUpperEdge );
   if ( !__gl_meshDelete( reg->eUp ) ) return 0;
   reg->fixUpperEdge = TOOLS_GLU_FALSE;
   reg->eUp = newEdge;
   newEdge->activeRegion = reg;
 
   return 1;
 }
 
 inline/*static*/ ActiveRegion *static_TopLeftRegion( ActiveRegion *reg )
 {
   GLUvertex *org = reg->eUp->Org;
   GLUhalfEdge *e;
 
   /* Find the region above the uppermost edge with the same origin */
   do {
     reg = RegionAbove( reg );
   } while( reg->eUp->Org == org );
 
   /* If the edge above was a temporary edge introduced by ConnectRightVertex,
    * now is the time to fix it.
    */
   if( reg->fixUpperEdge ) {
     e = __gl_meshConnect( RegionBelow(reg)->eUp->Sym, reg->eUp->Lnext );
     if (e == NULL) return NULL;
     if ( !static_FixUpperEdge( reg, e ) ) return NULL;
     reg = RegionAbove( reg );
   }
   return reg;
 }
 
 inline/*static*/ ActiveRegion *static_TopRightRegion( ActiveRegion *reg )
 {
   GLUvertex *dst = reg->eUp->Dst;
 
   /* Find the region above the uppermost edge with the same destination */
   do {
     reg = RegionAbove( reg );
   } while( reg->eUp->Dst == dst );
   return reg;
 }
 
 inline/*static*/ ActiveRegion *static_AddRegionBelow( GLUtesselator *tess,
                                      ActiveRegion *regAbove,
                                      GLUhalfEdge *eNewUp )
 /*
  * Add a new active region to the sweep line, *somewhere* below "regAbove"
  * (according to where the new edge belongs in the sweep-line dictionary).
  * The upper edge of the new region will be "eNewUp".
  * Winding number and "inside" flag are not updated.
  */
 {
   ActiveRegion *regNew = (ActiveRegion *)memAlloc( sizeof( ActiveRegion ));
   if (regNew == NULL) longjmp(tess->env,1);
 
   regNew->eUp = eNewUp;
   /* __gl_dictListInsertBefore */
   regNew->nodeUp = dictInsertBefore( tess->dict, regAbove->nodeUp, regNew );
   if (regNew->nodeUp == NULL) longjmp(tess->env,1);
   regNew->fixUpperEdge = TOOLS_GLU_FALSE;
   regNew->sentinel = TOOLS_GLU_FALSE;
   regNew->dirty = TOOLS_GLU_FALSE;
 
   eNewUp->activeRegion = regNew;
   return regNew;
 }
 
 inline/*static*/ GLUboolean static_IsWindingInside( GLUtesselator *tess, int n )
 {
   switch( tess->windingRule ) {
   case GLU_TESS_WINDING_ODD:
     return (n & 1);
   case GLU_TESS_WINDING_NONZERO:
     return (n != 0);
   case GLU_TESS_WINDING_POSITIVE:
     return (n > 0);
   case GLU_TESS_WINDING_NEGATIVE:
     return (n < 0);
   case GLU_TESS_WINDING_ABS_GEQ_TWO:
     return (n >= 2) || (n <= -2);
   }
   /*LINTED*/
   assert( TOOLS_GLU_FALSE );
   /*NOTREACHED*/
   return TOOLS_GLU_FALSE;  /* avoid compiler complaints */
 }
 
 
 inline/*static*/ void static_ComputeWinding( GLUtesselator *tess, ActiveRegion *reg )
 {
   reg->windingNumber = RegionAbove(reg)->windingNumber + reg->eUp->winding;
   reg->inside = static_IsWindingInside( tess, reg->windingNumber );
 }
 
 
 inline/*static*/ void static_FinishRegion( GLUtesselator *tess, ActiveRegion *reg )
 /*
  * Delete a region from the sweep line.  This happens when the upper
  * and lower chains of a region meet (at a vertex on the sweep line).
  * The "inside" flag is copied to the appropriate mesh face (we could
  * not do this before -- since the structure of the mesh is always
  * changing, this face may not have even existed until now).
  */
 {
   GLUhalfEdge *e = reg->eUp;
   GLUface *f = e->Lface;
 
   f->inside = reg->inside;
   f->anEdge = e;   /* optimization for __gl_meshTessellateMonoRegion() */
   static_DeleteRegion( tess, reg );
 }
 
 
 inline/*static*/ GLUhalfEdge *static_FinishLeftRegions( GLUtesselator *tess,
                ActiveRegion *regFirst, ActiveRegion *regLast )
 /*
  * We are given a vertex with one or more left-going edges.  All affected
  * edges should be in the edge dictionary.  Starting at regFirst->eUp,
  * we walk down deleting all regions where both edges have the same
  * origin vOrg.  At the same time we copy the "inside" flag from the
  * active region to the face, since at this point each face will belong
  * to at most one region (this was not necessarily true until this point
  * in the sweep).  The walk stops at the region above regLast; if regLast
  * is NULL we walk as far as possible.  At the same time we relink the
  * mesh if necessary, so that the ordering of edges around vOrg is the
  * same as in the dictionary.
  */
 {
   ActiveRegion *reg, *regPrev;
   GLUhalfEdge *e, *ePrev;
 
   regPrev = regFirst;
   ePrev = regFirst->eUp;
   while( regPrev != regLast ) {
     regPrev->fixUpperEdge = TOOLS_GLU_FALSE;    /* placement was OK */
     reg = RegionBelow( regPrev );
     e = reg->eUp;
     if( e->Org != ePrev->Org ) {
       if( ! reg->fixUpperEdge ) {
         /* Remove the last left-going edge.  Even though there are no further
          * edges in the dictionary with this origin, there may be further
          * such edges in the mesh (if we are adding left edges to a vertex
          * that has already been processed).  Thus it is important to call
          * FinishRegion rather than just DeleteRegion.
          */
         static_FinishRegion( tess, regPrev );
         break;
       }
       /* If the edge below was a temporary edge introduced by
        * ConnectRightVertex, now is the time to fix it.
        */
       e = __gl_meshConnect( ePrev->Lprev, e->Sym );
       if (e == NULL) longjmp(tess->env,1);
       if ( !static_FixUpperEdge( reg, e ) ) longjmp(tess->env,1);
     }
 
     /* Relink edges so that ePrev->Onext == e */
     if( ePrev->Onext != e ) {
       if ( !__gl_meshSplice( e->Oprev, e ) ) longjmp(tess->env,1);
       if ( !__gl_meshSplice( ePrev, e ) ) longjmp(tess->env,1);
     }
     static_FinishRegion( tess, regPrev );       /* may change reg->eUp */
     ePrev = reg->eUp;
     regPrev = reg;
   }
   return ePrev;
 }
 
 
 inline/*static*/ void static_AddRightEdges( GLUtesselator *tess, ActiveRegion *regUp,
        GLUhalfEdge *eFirst, GLUhalfEdge *eLast, GLUhalfEdge *eTopLeft,
        GLUboolean cleanUp )
 /*
  * Purpose: insert right-going edges into the edge dictionary, and update
  * winding numbers and mesh connectivity appropriately.  All right-going
  * edges share a common origin vOrg.  Edges are inserted CCW starting at
  * eFirst; the last edge inserted is eLast->Oprev.  If vOrg has any
  * left-going edges already processed, then eTopLeft must be the edge
  * such that an imaginary upward vertical segment from vOrg would be
  * contained between eTopLeft->Oprev and eTopLeft; otherwise eTopLeft
  * should be NULL.
  */
 {
   ActiveRegion *reg, *regPrev;
   GLUhalfEdge *e, *ePrev;
   int firstTime = TOOLS_GLU_TRUE;
 
   /* Insert the new right-going edges in the dictionary */
   e = eFirst;
   do {
     assert( VertLeq( e->Org, e->Dst ));
     static_AddRegionBelow( tess, regUp, e->Sym );
     e = e->Onext;
   } while ( e != eLast );
 
   /* Walk *all* right-going edges from e->Org, in the dictionary order,
    * updating the winding numbers of each region, and re-linking the mesh
    * edges to match the dictionary ordering (if necessary).
    */
   if( eTopLeft == NULL ) {
     eTopLeft = RegionBelow( regUp )->eUp->Rprev;
   }
   regPrev = regUp;
   ePrev = eTopLeft;
   for( ;; ) {
     reg = RegionBelow( regPrev );
     e = reg->eUp->Sym;
     if( e->Org != ePrev->Org ) break;
 
     if( e->Onext != ePrev ) {
       /* Unlink e from its current position, and relink below ePrev */
       if ( !__gl_meshSplice( e->Oprev, e ) ) longjmp(tess->env,1);
       if ( !__gl_meshSplice( ePrev->Oprev, e ) ) longjmp(tess->env,1);
     }
     /* Compute the winding number and "inside" flag for the new regions */
     reg->windingNumber = regPrev->windingNumber - e->winding;
     reg->inside = static_IsWindingInside( tess, reg->windingNumber );
 
     /* Check for two outgoing edges with same slope -- process these
      * before any intersection tests (see example in __gl_computeInterior).
      */
     regPrev->dirty = TOOLS_GLU_TRUE;
     if( ! firstTime && static_CheckForRightSplice( tess, regPrev )) {
       AddWinding( e, ePrev );
       static_DeleteRegion( tess, regPrev );
       if ( !__gl_meshDelete( ePrev ) ) longjmp(tess->env,1);
     }
     firstTime = TOOLS_GLU_FALSE;
     regPrev = reg;
     ePrev = e;
   }
   regPrev->dirty = TOOLS_GLU_TRUE;
   assert( regPrev->windingNumber - e->winding == reg->windingNumber );
 
   if( cleanUp ) {
     /* Check for intersections between newly adjacent edges. */
     static_WalkDirtyRegions( tess, regPrev );
   }
 }
 
 
 inline/*static*/ void static_CallCombine( GLUtesselator *tess, GLUvertex *isect,
                          void *data[4], GLUfloat weights[4], int needed )
 {
   GLUdouble coords[3];
 
   /* Copy coord data in case the callback changes it. */
   coords[0] = isect->coords[0];
   coords[1] = isect->coords[1];
   coords[2] = isect->coords[2];
 
   isect->data = NULL;
   CALL_COMBINE_OR_COMBINE_DATA( coords, data, weights, &isect->data );
   if( isect->data == NULL ) {
     if( ! needed ) {
       isect->data = data[0];
     } else if( ! tess->fatalError ) {
       /* The only way fatal error is when two edges are found to intersect,
        * but the user has not provided the callback necessary to handle
        * generated intersection points.
        */
       CALL_ERROR_OR_ERROR_DATA( GLU_TESS_NEED_COMBINE_CALLBACK );
       tess->fatalError = TOOLS_GLU_TRUE;
     }
   }
 }
 
 inline/*static*/ void static_SpliceMergeVertices( GLUtesselator *tess, GLUhalfEdge *e1,
                                  GLUhalfEdge *e2 )
 /*
  * Two vertices with idential coordinates are combined into one.
  * e1->Org is kept, while e2->Org is discarded.
  */
 {
   void *data[4] = { NULL, NULL, NULL, NULL };
   GLUfloat weights[4] = { 0.5, 0.5, 0.0, 0.0 };
 
   data[0] = e1->Org->data;
   data[1] = e2->Org->data;
   static_CallCombine( tess, e1->Org, data, weights, TOOLS_GLU_FALSE );
   if ( !__gl_meshSplice( e1, e2 ) ) longjmp(tess->env,1);
 }
 
 inline/*static*/ void static_VertexWeights( GLUvertex *isect, GLUvertex *org, GLUvertex *dst,
                            GLUfloat *weights )
 /*
  * Find some weights which describe how the intersection vertex is
  * a linear combination of "org" and "dest".  Each of the two edges
  * which generated "isect" is allocated 50% of the weight; each edge
  * splits the weight between its org and dst according to the
  * relative distance to "isect".
  */
 {
   GLUdouble t1 = VertL1dist( org, isect );
   GLUdouble t2 = VertL1dist( dst, isect );
 
   weights[0] = float(0.5 * t2 / (t1 + t2));
   weights[1] = float(0.5 * t1 / (t1 + t2));
   isect->coords[0] += weights[0]*org->coords[0] + weights[1]*dst->coords[0];
   isect->coords[1] += weights[0]*org->coords[1] + weights[1]*dst->coords[1];
   isect->coords[2] += weights[0]*org->coords[2] + weights[1]*dst->coords[2];
 }
 
 
 inline/*static*/ void static_GetIntersectData( GLUtesselator *tess, GLUvertex *isect,
        GLUvertex *orgUp, GLUvertex *dstUp,
        GLUvertex *orgLo, GLUvertex *dstLo )
 /*
  * We've computed a new intersection point, now we need a "data" pointer
  * from the user so that we can refer to this new vertex in the
  * rendering callbacks.
  */
 {
   void *data[4];
   GLUfloat weights[4];
 
   data[0] = orgUp->data;
   data[1] = dstUp->data;
   data[2] = orgLo->data;
   data[3] = dstLo->data;
 
   isect->coords[0] = isect->coords[1] = isect->coords[2] = 0;
   static_VertexWeights( isect, orgUp, dstUp, &weights[0] );
   static_VertexWeights( isect, orgLo, dstLo, &weights[2] );
 
   static_CallCombine( tess, isect, data, weights, TOOLS_GLU_TRUE );
 }
 
 inline/*static*/ int static_CheckForRightSplice( GLUtesselator *tess, ActiveRegion *regUp )
 /*
  * Check the upper and lower edge of "regUp", to make sure that the
  * eUp->Org is above eLo, or eLo->Org is below eUp (depending on which
  * origin is leftmost).
  *
  * The main purpose is to splice right-going edges with the same
  * dest vertex and nearly identical slopes (ie. we can't distinguish
  * the slopes numerically).  However the splicing can also help us
  * to recover from numerical errors.  For example, suppose at one
  * point we checked eUp and eLo, and decided that eUp->Org is barely
  * above eLo.  Then later, we split eLo into two edges (eg. from
  * a splice operation like this one).  This can change the result of
  * our test so that now eUp->Org is incident to eLo, or barely below it.
  * We must correct this condition to maintain the dictionary invariants.
  *
  * One possibility is to check these edges for intersection again
  * (ie. CheckForIntersect).  This is what we do if possible.  However
  * CheckForIntersect requires that tess->event lies between eUp and eLo,
  * so that it has something to fall back on when the intersection
  * calculation gives us an unusable answer.  So, for those cases where
  * we can't check for intersection, this routine fixes the problem
  * by just splicing the offending vertex into the other edge.
  * This is a guaranteed solution, no matter how degenerate things get.
  * Basically this is a combinatorial solution to a numerical problem.
  */
 {
   ActiveRegion *regLo = RegionBelow(regUp);
   GLUhalfEdge *eUp = regUp->eUp;
   GLUhalfEdge *eLo = regLo->eUp;
 
   if( VertLeq( eUp->Org, eLo->Org )) {
     if( EdgeSign( eLo->Dst, eUp->Org, eLo->Org ) > 0 ) return TOOLS_GLU_FALSE;
 
     /* eUp->Org appears to be below eLo */
     if( ! VertEq( eUp->Org, eLo->Org )) {
       /* Splice eUp->Org into eLo */
       if ( __gl_meshSplitEdge( eLo->Sym ) == NULL) longjmp(tess->env,1);
       if ( !__gl_meshSplice( eUp, eLo->Oprev ) ) longjmp(tess->env,1);
       regUp->dirty = regLo->dirty = TOOLS_GLU_TRUE;
 
     } else if( eUp->Org != eLo->Org ) {
       /* merge the two vertices, discarding eUp->Org */
       pqDelete( tess->pq, eUp->Org->pqHandle ); /* __gl_pqSortDelete */
       static_SpliceMergeVertices( tess, eLo->Oprev, eUp );
     }
   } else {
     if( EdgeSign( eUp->Dst, eLo->Org, eUp->Org ) < 0 ) return TOOLS_GLU_FALSE;
 
     /* eLo->Org appears to be above eUp, so splice eLo->Org into eUp */
     RegionAbove(regUp)->dirty = regUp->dirty = TOOLS_GLU_TRUE;
     if (__gl_meshSplitEdge( eUp->Sym ) == NULL) longjmp(tess->env,1);
     if ( !__gl_meshSplice( eLo->Oprev, eUp ) ) longjmp(tess->env,1);
   }
   return TOOLS_GLU_TRUE;
 }
 
 inline/*static*/ int static_CheckForLeftSplice( GLUtesselator *tess, ActiveRegion *regUp )
 /*
  * Check the upper and lower edge of "regUp", to make sure that the
  * eUp->Dst is above eLo, or eLo->Dst is below eUp (depending on which
  * destination is rightmost).
  *
  * Theoretically, this should always be true.  However, splitting an edge
  * into two pieces can change the results of previous tests.  For example,
  * suppose at one point we checked eUp and eLo, and decided that eUp->Dst
  * is barely above eLo.  Then later, we split eLo into two edges (eg. from
  * a splice operation like this one).  This can change the result of
  * the test so that now eUp->Dst is incident to eLo, or barely below it.
  * We must correct this condition to maintain the dictionary invariants
  * (otherwise new edges might get inserted in the wrong place in the
  * dictionary, and bad stuff will happen).
  *
  * We fix the problem by just splicing the offending vertex into the
  * other edge.
  */
 {
   ActiveRegion *regLo = RegionBelow(regUp);
   GLUhalfEdge *eUp = regUp->eUp;
   GLUhalfEdge *eLo = regLo->eUp;
   GLUhalfEdge *e;
 
   assert( ! VertEq( eUp->Dst, eLo->Dst ));
 
   if( VertLeq( eUp->Dst, eLo->Dst )) {
     if( EdgeSign( eUp->Dst, eLo->Dst, eUp->Org ) < 0 ) return TOOLS_GLU_FALSE;
 
     /* eLo->Dst is above eUp, so splice eLo->Dst into eUp */
     RegionAbove(regUp)->dirty = regUp->dirty = TOOLS_GLU_TRUE;
     e = __gl_meshSplitEdge( eUp );
     if (e == NULL) longjmp(tess->env,1);
     if ( !__gl_meshSplice( eLo->Sym, e ) ) longjmp(tess->env,1);
     e->Lface->inside = regUp->inside;
   } else {
     if( EdgeSign( eLo->Dst, eUp->Dst, eLo->Org ) > 0 ) return TOOLS_GLU_FALSE;
 
     /* eUp->Dst is below eLo, so splice eUp->Dst into eLo */
     regUp->dirty = regLo->dirty = TOOLS_GLU_TRUE;
     e = __gl_meshSplitEdge( eLo );
     if (e == NULL) longjmp(tess->env,1);
     if ( !__gl_meshSplice( eUp->Lnext, eLo->Sym ) ) longjmp(tess->env,1);
     e->Rface->inside = regUp->inside;
   }
   return TOOLS_GLU_TRUE;
 }
 
 
 inline/*static*/ int static_CheckForIntersect( GLUtesselator *tess, ActiveRegion *regUp )
 /*
  * Check the upper and lower edges of the given region to see if
  * they intersect.  If so, create the intersection and add it
  * to the data structures.
  *
  * Returns TOOLS_GLU_TRUE if adding the new intersection resulted in a recursive
  * call to AddRightEdges(); in this case all "dirty" regions have been
  * checked for intersections, and possibly regUp has been deleted.
  */
 {
   ActiveRegion *regLo = RegionBelow(regUp);
   GLUhalfEdge *eUp = regUp->eUp;
   GLUhalfEdge *eLo = regLo->eUp;
   GLUvertex *orgUp = eUp->Org;
   GLUvertex *orgLo = eLo->Org;
   GLUvertex *dstUp = eUp->Dst;
   GLUvertex *dstLo = eLo->Dst;
   GLUdouble tMinUp, tMaxLo;
   GLUvertex isect, *orgMin;
   GLUhalfEdge *e;
 
   assert( ! VertEq( dstLo, dstUp ));
   assert( EdgeSign( dstUp, tess->event, orgUp ) <= 0 );
   assert( EdgeSign( dstLo, tess->event, orgLo ) >= 0 );
   assert( orgUp != tess->event && orgLo != tess->event );
   assert( ! regUp->fixUpperEdge && ! regLo->fixUpperEdge );
 
   if( orgUp == orgLo ) return TOOLS_GLU_FALSE;  /* right endpoints are the same */
 
   tMinUp = GLU_MIN( orgUp->t, dstUp->t );
   tMaxLo = GLU_MAX( orgLo->t, dstLo->t );
   if( tMinUp > tMaxLo ) return TOOLS_GLU_FALSE; /* t ranges do not overlap */
 
   if( VertLeq( orgUp, orgLo )) {
     if( EdgeSign( dstLo, orgUp, orgLo ) > 0 ) return TOOLS_GLU_FALSE;
   } else {
     if( EdgeSign( dstUp, orgLo, orgUp ) < 0 ) return TOOLS_GLU_FALSE;
   }
 
   /* At this point the edges intersect, at least marginally */
   DebugEvent( tess );
 
   __gl_edgeIntersect( dstUp, orgUp, dstLo, orgLo, &isect );
   /* The following properties are guaranteed: */
   assert( GLU_MIN( orgUp->t, dstUp->t ) <= isect.t );
   assert( isect.t <= GLU_MAX( orgLo->t, dstLo->t ));
   assert( GLU_MIN( dstLo->s, dstUp->s ) <= isect.s );
   assert( isect.s <= GLU_MAX( orgLo->s, orgUp->s ));
 
   if( VertLeq( &isect, tess->event )) {
     /* The intersection point lies slightly to the left of the sweep line,
      * so move it until it''s slightly to the right of the sweep line.
      * (If we had perfect numerical precision, this would never happen
      * in the first place).  The easiest and safest thing to do is
      * replace the intersection by tess->event.
      */
     isect.s = tess->event->s;
     isect.t = tess->event->t;
   }
   /* Similarly, if the computed intersection lies to the right of the
    * rightmost origin (which should rarely happen), it can cause
    * unbelievable inefficiency on sufficiently degenerate inputs.
    * (If you have the test program, try running test54.d with the
    * "X zoom" option turned on).
    */
   orgMin = VertLeq( orgUp, orgLo ) ? orgUp : orgLo;
   if( VertLeq( orgMin, &isect )) {
     isect.s = orgMin->s;
     isect.t = orgMin->t;
   }
 
   if( VertEq( &isect, orgUp ) || VertEq( &isect, orgLo )) {
     /* Easy case -- intersection at one of the right endpoints */
     (void) static_CheckForRightSplice( tess, regUp );
     return TOOLS_GLU_FALSE;
   }
 
   if(    (! VertEq( dstUp, tess->event )
           && EdgeSign( dstUp, tess->event, &isect ) >= 0)
       || (! VertEq( dstLo, tess->event )
           && EdgeSign( dstLo, tess->event, &isect ) <= 0 ))
   {
     /* Very unusual -- the new upper or lower edge would pass on the
      * wrong side of the sweep event, or through it.  This can happen
      * due to very small numerical errors in the intersection calculation.
      */
     if( dstLo == tess->event ) {
       /* Splice dstLo into eUp, and process the new region(s) */
       if (__gl_meshSplitEdge( eUp->Sym ) == NULL) longjmp(tess->env,1);
       if ( !__gl_meshSplice( eLo->Sym, eUp ) ) longjmp(tess->env,1);
       regUp = static_TopLeftRegion( regUp );
       if (regUp == NULL) longjmp(tess->env,1);
       eUp = RegionBelow(regUp)->eUp;
       static_FinishLeftRegions( tess, RegionBelow(regUp), regLo );
       static_AddRightEdges( tess, regUp, eUp->Oprev, eUp, eUp, TOOLS_GLU_TRUE );
       return TOOLS_GLU_TRUE;
     }
     if( dstUp == tess->event ) {
       /* Splice dstUp into eLo, and process the new region(s) */
       if (__gl_meshSplitEdge( eLo->Sym ) == NULL) longjmp(tess->env,1);
       if ( !__gl_meshSplice( eUp->Lnext, eLo->Oprev ) ) longjmp(tess->env,1);
       regLo = regUp;
       regUp = static_TopRightRegion( regUp );
       e = RegionBelow(regUp)->eUp->Rprev;
       regLo->eUp = eLo->Oprev;
       eLo = static_FinishLeftRegions( tess, regLo, NULL );
       static_AddRightEdges( tess, regUp, eLo->Onext, eUp->Rprev, e, TOOLS_GLU_TRUE );
       return TOOLS_GLU_TRUE;
     }
     /* Special case: called from ConnectRightVertex.  If either
      * edge passes on the wrong side of tess->event, split it
      * (and wait for ConnectRightVertex to splice it appropriately).
      */
     if( EdgeSign( dstUp, tess->event, &isect ) >= 0 ) {
       RegionAbove(regUp)->dirty = regUp->dirty = TOOLS_GLU_TRUE;
       if (__gl_meshSplitEdge( eUp->Sym ) == NULL) longjmp(tess->env,1);
       eUp->Org->s = tess->event->s;
       eUp->Org->t = tess->event->t;
     }
     if( EdgeSign( dstLo, tess->event, &isect ) <= 0 ) {
       regUp->dirty = regLo->dirty = TOOLS_GLU_TRUE;
       if (__gl_meshSplitEdge( eLo->Sym ) == NULL) longjmp(tess->env,1);
       eLo->Org->s = tess->event->s;
       eLo->Org->t = tess->event->t;
     }
     /* leave the rest for ConnectRightVertex */
     return TOOLS_GLU_FALSE;
   }
 
   /* General case -- split both edges, splice into new vertex.
    * When we do the splice operation, the order of the arguments is
    * arbitrary as far as correctness goes.  However, when the operation
    * creates a new face, the work done is proportional to the size of
    * the new face.  We expect the faces in the processed part of
    * the mesh (ie. eUp->Lface) to be smaller than the faces in the
    * unprocessed original contours (which will be eLo->Oprev->Lface).
    */
   if (__gl_meshSplitEdge( eUp->Sym ) == NULL) longjmp(tess->env,1);
   if (__gl_meshSplitEdge( eLo->Sym ) == NULL) longjmp(tess->env,1);
   if ( !__gl_meshSplice( eLo->Oprev, eUp ) ) longjmp(tess->env,1);
   eUp->Org->s = isect.s;
   eUp->Org->t = isect.t;
   eUp->Org->pqHandle = pqInsert( tess->pq, eUp->Org ); /* __gl_pqSortInsert */
   if (eUp->Org->pqHandle == LONG_MAX) {
      pqDeletePriorityQ(tess->pq);       /* __gl_pqSortDeletePriorityQ */
      tess->pq = NULL;
      longjmp(tess->env,1);
   }
   static_GetIntersectData( tess, eUp->Org, orgUp, dstUp, orgLo, dstLo );
   RegionAbove(regUp)->dirty = regUp->dirty = regLo->dirty = TOOLS_GLU_TRUE;
   return TOOLS_GLU_FALSE;
 }
 
 inline/*static*/ void static_WalkDirtyRegions( GLUtesselator *tess, ActiveRegion *regUp )
 /*
  * When the upper or lower edge of any region changes, the region is
  * marked "dirty".  This routine walks through all the dirty regions
  * and makes sure that the dictionary invariants are satisfied
  * (see the comments at the beginning of this file).  Of course
  * new dirty regions can be created as we make changes to restore
  * the invariants.
  */
 {
   ActiveRegion *regLo = RegionBelow(regUp);
   GLUhalfEdge *eUp, *eLo;
 
   for( ;; ) {
     /* Find the lowest dirty region (we walk from the bottom up). */
     while( regLo->dirty ) {
       regUp = regLo;
       regLo = RegionBelow(regLo);
     }
     if( ! regUp->dirty ) {
       regLo = regUp;
       regUp = RegionAbove( regUp );
       if( regUp == NULL || ! regUp->dirty ) {
         /* We've walked all the dirty regions */
         return;
       }
     }
     regUp->dirty = TOOLS_GLU_FALSE;
     eUp = regUp->eUp;
     eLo = regLo->eUp;
 
     if( eUp->Dst != eLo->Dst ) {
       /* Check that the edge ordering is obeyed at the Dst vertices. */
       if( static_CheckForLeftSplice( tess, regUp )) {
 
         /* If the upper or lower edge was marked fixUpperEdge, then
          * we no longer need it (since these edges are needed only for
          * vertices which otherwise have no right-going edges).
          */
         if( regLo->fixUpperEdge ) {
           static_DeleteRegion( tess, regLo );
           if ( !__gl_meshDelete( eLo ) ) longjmp(tess->env,1);
           regLo = RegionBelow( regUp );
           eLo = regLo->eUp;
         } else if( regUp->fixUpperEdge ) {
           static_DeleteRegion( tess, regUp );
           if ( !__gl_meshDelete( eUp ) ) longjmp(tess->env,1);
           regUp = RegionAbove( regLo );
           eUp = regUp->eUp;
         }
       }
     }
     if( eUp->Org != eLo->Org ) {
       if(    eUp->Dst != eLo->Dst
           && ! regUp->fixUpperEdge && ! regLo->fixUpperEdge
           && (eUp->Dst == tess->event || eLo->Dst == tess->event) )
       {
         /* When all else fails in CheckForIntersect(), it uses tess->event
          * as the intersection location.  To make this possible, it requires
          * that tess->event lie between the upper and lower edges, and also
          * that neither of these is marked fixUpperEdge (since in the worst
          * case it might splice one of these edges into tess->event, and
          * violate the invariant that fixable edges are the only right-going
          * edge from their associated vertex).
          */
         if( static_CheckForIntersect( tess, regUp )) {
           /* WalkDirtyRegions() was called recursively; we're done */
           return;
         }
       } else {
         /* Even though we can't use CheckForIntersect(), the Org vertices
          * may violate the dictionary edge ordering.  Check and correct this.
          */
         (void) static_CheckForRightSplice( tess, regUp );
       }
     }
     if( eUp->Org == eLo->Org && eUp->Dst == eLo->Dst ) {
       /* A degenerate loop consisting of only two edges -- delete it. */
       AddWinding( eLo, eUp );
       static_DeleteRegion( tess, regUp );
       if ( !__gl_meshDelete( eUp ) ) longjmp(tess->env,1);
       regUp = RegionAbove( regLo );
     }
   }
 }
 
 
 inline/*static*/ void static_ConnectRightVertex( GLUtesselator *tess, ActiveRegion *regUp,
                                 GLUhalfEdge *eBottomLeft )
 /*
  * Purpose: connect a "right" vertex vEvent (one where all edges go left)
  * to the unprocessed portion of the mesh.  Since there are no right-going
  * edges, two regions (one above vEvent and one below) are being merged
  * into one.  "regUp" is the upper of these two regions.
  *
  * There are two reasons for doing this (adding a right-going edge):
  *  - if the two regions being merged are "inside", we must add an edge
  *    to keep them separated (the combined region would not be monotone).
  *  - in any case, we must leave some record of vEvent in the dictionary,
  *    so that we can merge vEvent with features that we have not seen yet.
  *    For example, maybe there is a vertical edge which passes just to
  *    the right of vEvent; we would like to splice vEvent into this edge.
  *
  * However, we don't want to connect vEvent to just any vertex.  We don''t
  * want the new edge to cross any other edges; otherwise we will create
  * intersection vertices even when the input data had no self-intersections.
  * (This is a bad thing; if the user's input data has no intersections,
  * we don't want to generate any false intersections ourselves.)
  *
  * Our eventual goal is to connect vEvent to the leftmost unprocessed
  * vertex of the combined region (the union of regUp and regLo).
  * But because of unseen vertices with all right-going edges, and also
  * new vertices which may be created by edge intersections, we don''t
  * know where that leftmost unprocessed vertex is.  In the meantime, we
  * connect vEvent to the closest vertex of either chain, and mark the region
  * as "fixUpperEdge".  This flag says to delete and reconnect this edge
  * to the next processed vertex on the boundary of the combined region.
  * Quite possibly the vertex we connected to will turn out to be the
  * closest one, in which case we won''t need to make any changes.
  */
 {
   GLUhalfEdge *eNew;
   GLUhalfEdge *eTopLeft = eBottomLeft->Onext;
   ActiveRegion *regLo = RegionBelow(regUp);
   GLUhalfEdge *eUp = regUp->eUp;
   GLUhalfEdge *eLo = regLo->eUp;
   int degenerate = TOOLS_GLU_FALSE;
 
   if( eUp->Dst != eLo->Dst ) {
     (void) static_CheckForIntersect( tess, regUp );
   }
 
   /* Possible new degeneracies: upper or lower edge of regUp may pass
    * through vEvent, or may coincide with new intersection vertex
    */
   if( VertEq( eUp->Org, tess->event )) {
     if ( !__gl_meshSplice( eTopLeft->Oprev, eUp ) ) longjmp(tess->env,1);
     regUp = static_TopLeftRegion( regUp );
     if (regUp == NULL) longjmp(tess->env,1);
     eTopLeft = RegionBelow( regUp )->eUp;
     static_FinishLeftRegions( tess, RegionBelow(regUp), regLo );
     degenerate = TOOLS_GLU_TRUE;
   }
   if( VertEq( eLo->Org, tess->event )) {
     if ( !__gl_meshSplice( eBottomLeft, eLo->Oprev ) ) longjmp(tess->env,1);
     eBottomLeft = static_FinishLeftRegions( tess, regLo, NULL );
     degenerate = TOOLS_GLU_TRUE;
   }
   if( degenerate ) {
     static_AddRightEdges( tess, regUp, eBottomLeft->Onext, eTopLeft, eTopLeft, TOOLS_GLU_TRUE );
     return;
   }
 
   /* Non-degenerate situation -- need to add a temporary, fixable edge.
    * Connect to the closer of eLo->Org, eUp->Org.
    */
   if( VertLeq( eLo->Org, eUp->Org )) {
     eNew = eLo->Oprev;
   } else {
     eNew = eUp;
   }
   eNew = __gl_meshConnect( eBottomLeft->Lprev, eNew );
   if (eNew == NULL) longjmp(tess->env,1);
 
   /* Prevent cleanup, otherwise eNew might disappear before we've even
    * had a chance to mark it as a temporary edge.
    */
   static_AddRightEdges( tess, regUp, eNew, eNew->Onext, eNew->Onext, TOOLS_GLU_FALSE );
   eNew->Sym->activeRegion->fixUpperEdge = TOOLS_GLU_TRUE;
   static_WalkDirtyRegions( tess, regUp );
 }
 
 /* Because vertices at exactly the same location are merged together
  * before we process the sweep event, some degenerate cases can't occur.
  * However if someone eventually makes the modifications required to
  * merge features which are close together, the cases below marked
  * TOLERANCE_NONZERO will be useful.  They were debugged before the
  * code to merge identical vertices in the main loop was added.
  */
 //#define TOLERANCE_NONZERO     TOOLS_GLU_FALSE
 
 inline/*static*/ void static_ConnectLeftDegenerate( GLUtesselator *tess,
                                    ActiveRegion *regUp, GLUvertex *vEvent )
 /*
  * The event vertex lies exacty on an already-processed edge or vertex.
  * Adding the new vertex involves splicing it into the already-processed
  * part of the mesh.
  */
 {
   GLUhalfEdge *e, *eTopLeft, *eTopRight, *eLast;
   ActiveRegion *reg;
 
   e = regUp->eUp;
   if( VertEq( e->Org, vEvent )) {
     /* e->Org is an unprocessed vertex - just combine them, and wait
      * for e->Org to be pulled from the queue
      */
     assert( /*TOLERANCE_NONZERO*/ TOOLS_GLU_FALSE );
     static_SpliceMergeVertices( tess, e, vEvent->anEdge );
     return;
   }
 
   if( ! VertEq( e->Dst, vEvent )) {
     /* General case -- splice vEvent into edge e which passes through it */
     if (__gl_meshSplitEdge( e->Sym ) == NULL) longjmp(tess->env,1);
     if( regUp->fixUpperEdge ) {
       /* This edge was fixable -- delete unused portion of original edge */
       if ( !__gl_meshDelete( e->Onext ) ) longjmp(tess->env,1);
       regUp->fixUpperEdge = TOOLS_GLU_FALSE;
     }
     if ( !__gl_meshSplice( vEvent->anEdge, e ) ) longjmp(tess->env,1);
     static_SweepEvent( tess, vEvent ); /* recurse */
     return;
   }
 
   /* vEvent coincides with e->Dst, which has already been processed.
    * Splice in the additional right-going edges.
    */
   assert( /*TOLERANCE_NONZERO*/ TOOLS_GLU_FALSE );
   regUp = static_TopRightRegion( regUp );
   reg = RegionBelow( regUp );
   eTopRight = reg->eUp->Sym;
   eTopLeft = eLast = eTopRight->Onext;
   if( reg->fixUpperEdge ) {
     /* Here e->Dst has only a single fixable edge going right.
      * We can delete it since now we have some real right-going edges.
      */
     assert( eTopLeft != eTopRight );   /* there are some left edges too */
     static_DeleteRegion( tess, reg );
     if ( !__gl_meshDelete( eTopRight ) ) longjmp(tess->env,1);
     eTopRight = eTopLeft->Oprev;
   }
   if ( !__gl_meshSplice( vEvent->anEdge, eTopRight ) ) longjmp(tess->env,1);
   if( ! EdgeGoesLeft( eTopLeft )) {
     /* e->Dst had no left-going edges -- indicate this to AddRightEdges() */
     eTopLeft = NULL;
   }
   static_AddRightEdges( tess, regUp, eTopRight->Onext, eLast, eTopLeft, TOOLS_GLU_TRUE );
 }
 
 
 inline/*static*/ void static_ConnectLeftVertex( GLUtesselator *tess, GLUvertex *vEvent )
 /*
  * Purpose: connect a "left" vertex (one where both edges go right)
  * to the processed portion of the mesh.  Let R be the active region
  * containing vEvent, and let U and L be the upper and lower edge
  * chains of R.  There are two possibilities:
  *
  * - the normal case: split R into two regions, by connecting vEvent to
  *   the rightmost vertex of U or L lying to the left of the sweep line
  *
  * - the degenerate case: if vEvent is close enough to U or L, we
  *   merge vEvent into that edge chain.  The subcases are:
  *      - merging with the rightmost vertex of U or L
  *      - merging with the active edge of U or L
  *      - merging with an already-processed portion of U or L
  */
 {
   ActiveRegion *regUp, *regLo, *reg;
   GLUhalfEdge *eUp, *eLo, *eNew;
   ActiveRegion tmp;
 
   /* assert( vEvent->anEdge->Onext->Onext == vEvent->anEdge ); */
 
   /* Get a pointer to the active region containing vEvent */
   tmp.eUp = vEvent->anEdge->Sym;
   /* __GL_DICTLISTKEY */ /* __gl_dictListSearch */
   regUp = (ActiveRegion *)dictKey( dictSearch( tess->dict, &tmp ));
   regLo = RegionBelow( regUp );
   eUp = regUp->eUp;
   eLo = regLo->eUp;
 
   /* Try merging with U or L first */
   if( EdgeSign( eUp->Dst, vEvent, eUp->Org ) == 0 ) {
     static_ConnectLeftDegenerate( tess, regUp, vEvent );
     return;
   }
 
   /* Connect vEvent to rightmost processed vertex of either chain.
    * e->Dst is the vertex that we will connect to vEvent.
    */
   reg = VertLeq( eLo->Dst, eUp->Dst ) ? regUp : regLo;
 
   if( regUp->inside || reg->fixUpperEdge) {
     if( reg == regUp ) {
       eNew = __gl_meshConnect( vEvent->anEdge->Sym, eUp->Lnext );
       if (eNew == NULL) longjmp(tess->env,1);
     } else {
       GLUhalfEdge *tempHalfEdge= __gl_meshConnect( eLo->Dnext, vEvent->anEdge);
       if (tempHalfEdge == NULL) longjmp(tess->env,1);
 
       eNew = tempHalfEdge->Sym;
     }
     if( reg->fixUpperEdge ) {
       if ( !static_FixUpperEdge( reg, eNew ) ) longjmp(tess->env,1);
     } else {
       static_ComputeWinding( tess, static_AddRegionBelow( tess, regUp, eNew ));
     }
     static_SweepEvent( tess, vEvent );
   } else {
     /* The new vertex is in a region which does not belong to the polygon.
      * We don''t need to connect this vertex to the rest of the mesh.
      */
     static_AddRightEdges( tess, regUp, vEvent->anEdge, vEvent->anEdge, NULL, TOOLS_GLU_TRUE );
   }
 }
 
 
 inline/*static*/ void static_SweepEvent( GLUtesselator *tess, GLUvertex *vEvent )
 /*
  * Does everything necessary when the sweep line crosses a vertex.
  * Updates the mesh and the edge dictionary.
  */
 {
   ActiveRegion *regUp, *reg;
   GLUhalfEdge *e, *eTopLeft, *eBottomLeft;
 
   tess->event = vEvent;         /* for access in EdgeLeq() */
   DebugEvent( tess );
 
   /* Check if this vertex is the right endpoint of an edge that is
    * already in the dictionary.  In this case we don't need to waste
    * time searching for the location to insert new edges.
    */
   e = vEvent->anEdge;
   while( e->activeRegion == NULL ) {
     e = e->Onext;
     if( e == vEvent->anEdge ) {
       /* All edges go right -- not incident to any processed edges */
       static_ConnectLeftVertex( tess, vEvent );
       return;
     }
   }
 
   /* Processing consists of two phases: first we "finish" all the
    * active regions where both the upper and lower edges terminate
    * at vEvent (ie. vEvent is closing off these regions).
    * We mark these faces "inside" or "outside" the polygon according
    * to their winding number, and delete the edges from the dictionary.
    * This takes care of all the left-going edges from vEvent.
    */
   regUp = static_TopLeftRegion( e->activeRegion );
   if (regUp == NULL) longjmp(tess->env,1);
   reg = RegionBelow( regUp );
   eTopLeft = reg->eUp;
   eBottomLeft = static_FinishLeftRegions( tess, reg, NULL );
 
   /* Next we process all the right-going edges from vEvent.  This
    * involves adding the edges to the dictionary, and creating the
    * associated "active regions" which record information about the
    * regions between adjacent dictionary edges.
    */
   if( eBottomLeft->Onext == eTopLeft ) {
     /* No right-going edges -- add a temporary "fixable" edge */
     static_ConnectRightVertex( tess, regUp, eBottomLeft );
   } else {
     static_AddRightEdges( tess, regUp, eBottomLeft->Onext, eTopLeft, eTopLeft, TOOLS_GLU_TRUE );
   }
 }
 
 
 /* Make the sentinel coordinates big enough that they will never be
  * merged with real input features.  (Even with the largest possible
  * input contour and the maximum tolerance of 1.0, no merging will be
  * done with coordinates larger than 3 * GLU_TESS_MAX_COORD).
  */
 //#define SENTINEL_COORD (4 * GLU_TESS_MAX_COORD)
 inline GLUdouble SENTINEL_COORD() {
   static const GLUdouble s_value = 4 * GLU_TESS_MAX_COORD;
   return s_value;
 }
 
 inline/*static*/ void static_AddSentinel( GLUtesselator *tess, GLUdouble t )
 /*
  * We add two sentinel edges above and below all other edges,
  * to avoid special cases at the top and bottom.
  */
 {
   GLUhalfEdge *e;
   ActiveRegion *reg = (ActiveRegion *)memAlloc( sizeof( ActiveRegion ));
   if (reg == NULL) longjmp(tess->env,1);
 
   e = __gl_meshMakeEdge( tess->mesh );
   if (e == NULL) longjmp(tess->env,1);
 
   e->Org->s = SENTINEL_COORD();
   e->Org->t = t;
   e->Dst->s = -SENTINEL_COORD();
   e->Dst->t = t;
   tess->event = e->Dst;         /* initialize it */
 
   reg->eUp = e;
   reg->windingNumber = 0;
   reg->inside = TOOLS_GLU_FALSE;
   reg->fixUpperEdge = TOOLS_GLU_FALSE;
   reg->sentinel = TOOLS_GLU_TRUE;
   reg->dirty = TOOLS_GLU_FALSE;
   reg->nodeUp = dictInsert( tess->dict, reg ); /* __gl_dictListInsertBefore */
   if (reg->nodeUp == NULL) longjmp(tess->env,1);
 }
 
 
 inline/*static*/ void static_InitEdgeDict( GLUtesselator *tess )
 /*
  * We maintain an ordering of edge intersections with the sweep line.
  * This order is maintained in a dynamic dictionary.
  */
 {
   /* __gl_dictListNewDict */
   tess->dict = dictNewDict( tess, (int (*)(void *, DictKey, DictKey)) static_EdgeLeq );
   if (tess->dict == NULL) longjmp(tess->env,1);
 
   static_AddSentinel( tess, -SENTINEL_COORD() );
   static_AddSentinel( tess, SENTINEL_COORD() );
 }
 
 
 inline/*static*/ void static_DoneEdgeDict( GLUtesselator *tess )
 {
   ActiveRegion *reg;
 #ifndef NDEBUG
   int fixedEdges = 0;
 #endif
 
   /* __GL_DICTLISTKEY */ /* __GL_DICTLISTMIN */
   while( (reg = (ActiveRegion *)dictKey( dictMin( tess->dict ))) != NULL ) {
     /*
      * At the end of all processing, the dictionary should contain
      * only the two sentinel edges, plus at most one "fixable" edge
      * created by ConnectRightVertex().
      */
     if( ! reg->sentinel ) {
       assert( reg->fixUpperEdge );
     //G.Barrand : fix a Coverity diagnostic : begin :
     //assert( ++fixedEdges == 1 );
 #ifndef NDEBUG
       fixedEdges++;
 #endif
       assert( fixedEdges == 1 );
     //G.Barrand : end.
     }
     assert( reg->windingNumber == 0 );
     static_DeleteRegion( tess, reg );
 /*    __gl_meshDelete( reg->eUp );*/
   }
   dictDeleteDict( tess->dict ); /* __gl_dictListDeleteDict */
 }
 
 
 inline/*static*/ void static_RemoveDegenerateEdges( GLUtesselator *tess )
 /*
  * Remove zero-length edges, and contours with fewer than 3 vertices.
  */
 {
   GLUhalfEdge *e, *eNext, *eLnext;
   GLUhalfEdge *eHead = &tess->mesh->eHead;
 
   /*LINTED*/
   for( e = eHead->next; e != eHead; e = eNext ) {
     eNext = e->next;
     eLnext = e->Lnext;
 
     if( VertEq( e->Org, e->Dst ) && e->Lnext->Lnext != e ) {
       /* Zero-length edge, contour has at least 3 edges */
 
       static_SpliceMergeVertices( tess, eLnext, e );    /* deletes e->Org */
       if ( !__gl_meshDelete( e ) ) longjmp(tess->env,1); /* e is a self-loop */
       e = eLnext;
       eLnext = e->Lnext;
     }
     if( eLnext->Lnext == e ) {
       /* Degenerate contour (one or two edges) */
 
       if( eLnext != e ) {
         if( eLnext == eNext || eLnext == eNext->Sym ) { eNext = eNext->next; }
         if ( !__gl_meshDelete( eLnext ) ) longjmp(tess->env,1);
       }
       if( e == eNext || e == eNext->Sym ) { eNext = eNext->next; }
       if ( !__gl_meshDelete( e ) ) longjmp(tess->env,1);
     }
   }
 }
 
 inline/*static*/ int static_InitPriorityQ( GLUtesselator *tess )
 /*
  * Insert all vertices into the priority queue which determines the
  * order in which vertices cross the sweep line.
  */
 {
   PriorityQ *pq;
   GLUvertex *v, *vHead;
 
   /* __gl_pqSortNewPriorityQ */
   pq = tess->pq = pqNewPriorityQ( (int (*)(PQkey, PQkey)) __gl_vertLeq );
   if (pq == NULL) return 0;
 
   vHead = &tess->mesh->vHead;
   for( v = vHead->next; v != vHead; v = v->next ) {
     v->pqHandle = pqInsert( pq, v ); /* __gl_pqSortInsert */
     if (v->pqHandle == LONG_MAX) break;
   }
   if (v != vHead || !pqInit( pq ) ) { /* __gl_pqSortInit */
     pqDeletePriorityQ(tess->pq);        /* __gl_pqSortDeletePriorityQ */
     tess->pq = NULL;
     return 0;
   }
 
   return 1;
 }
 
 
 inline/*static*/ void static_DonePriorityQ( GLUtesselator *tess )
 {
   pqDeletePriorityQ( tess->pq ); /* __gl_pqSortDeletePriorityQ */
 }
 
 
 inline/*static*/ int static_RemoveDegenerateFaces( GLUmesh *mesh )
 /*
  * Delete any degenerate faces with only two edges.  WalkDirtyRegions()
  * will catch almost all of these, but it won't catch degenerate faces
  * produced by splice operations on already-processed edges.
  * The two places this can happen are in FinishLeftRegions(), when
  * we splice in a "temporary" edge produced by ConnectRightVertex(),
  * and in CheckForLeftSplice(), where we splice already-processed
  * edges to ensure that our dictionary invariants are not violated
  * by numerical errors.
  *
  * In both these cases it is *very* dangerous to delete the offending
  * edge at the time, since one of the routines further up the stack
  * will sometimes be keeping a pointer to that edge.
  */
 {
   GLUface *f, *fNext;
   GLUhalfEdge *e;
 
   /*LINTED*/
   for( f = mesh->fHead.next; f != &mesh->fHead; f = fNext ) {
     fNext = f->next;
     e = f->anEdge;
     assert( e->Lnext != e );
 
     if( e->Lnext->Lnext == e ) {
       /* A face with only two edges */
       AddWinding( e->Onext, e );
       if ( !__gl_meshDelete( e ) ) return 0;
     }
   }
   return 1;
 }
 
 inline int __gl_computeInterior( GLUtesselator *tess )
 /*
  * __gl_computeInterior( tess ) computes the planar arrangement specified
  * by the given contours, and further subdivides this arrangement
  * into regions.  Each region is marked "inside" if it belongs
  * to the polygon, according to the rule given by tess->windingRule.
  * Each interior region is guaranteed be monotone.
  */
 {
   GLUvertex *v, *vNext;
 
   tess->fatalError = TOOLS_GLU_FALSE;
 
   /* Each vertex defines an event for our sweep line.  Start by inserting
    * all the vertices in a priority queue.  Events are processed in
    * lexicographic order, ie.
    *
    *    e1 < e2  iff  e1.x < e2.x || (e1.x == e2.x && e1.y < e2.y)
    */
   static_RemoveDegenerateEdges( tess );
   if ( !static_InitPriorityQ( tess ) ) return 0; /* if error */
   static_InitEdgeDict( tess );
 
   /* __gl_pqSortExtractMin */
   while( (v = (GLUvertex *)pqExtractMin( tess->pq )) != NULL ) {
     for( ;; ) {
       vNext = (GLUvertex *)pqMinimum( tess->pq ); /* __gl_pqSortMinimum */
       if( vNext == NULL || ! VertEq( vNext, v )) break;
 
       /* Merge together all vertices at exactly the same location.
        * This is more efficient than processing them one at a time,
        * simplifies the code (see ConnectLeftDegenerate), and is also
        * important for correct handling of certain degenerate cases.
        * For example, suppose there are two identical edges A and B
        * that belong to different contours (so without this code they would
        * be processed by separate sweep events).  Suppose another edge C
        * crosses A and B from above.  When A is processed, we split it
        * at its intersection point with C.  However this also splits C,
        * so when we insert B we may compute a slightly different
        * intersection point.  This might leave two edges with a small
        * gap between them.  This kind of error is especially obvious
        * when using boundary extraction (GLU_TESS_BOUNDARY_ONLY).
        */
       vNext = (GLUvertex *)pqExtractMin( tess->pq ); /* __gl_pqSortExtractMin*/
       static_SpliceMergeVertices( tess, v->anEdge, vNext->anEdge );
     }
     static_SweepEvent( tess, v );
   }
 
   /* Set tess->event for debugging purposes */
   /* __GL_DICTLISTKEY */ /* __GL_DICTLISTMIN */
   tess->event = ((ActiveRegion *) dictKey( dictMin( tess->dict )))->eUp->Org;
   DebugEvent( tess );
   static_DoneEdgeDict( tess );
   static_DonePriorityQ( tess );
 
   if ( !static_RemoveDegenerateFaces( tess->mesh ) ) return 0;
   __gl_meshCheckMesh( tess->mesh );
 
   return 1;
 }
 
 #endif

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