several bugs fixed here.

        849789  Second assertion `m_poly_borders->next' failed in Gcalc_operation_reducer::count_slice in maria-5.3-gis
        849791  Fourth assertion `n > 0 && n < SINUSES_CALCULATED*2+1' in get_n_sincos
        849789  Second assertion `m_poly_borders->next' failed in Gcalc_operation_reducer::count_slice in maria-5.3-gis
        848901   Assertion `fabs(cur_isc->x-m_cur_intersection->x) + fabs(cur_isc->y-m_cur_intersection->y) < 0.000000000001' failed in Gcalc_scan_iterator::intersection_scan() in maria-5.3-gis
        
per-file comments:
  mysql-test/r/gis-precise.result
        test result updated.
  mysql-test/r/gis.result
        test result updated.
  sql/gcalc_slicescan.cc
        bugfixes.
  sql/gcalc_slicescan.h
        bugfixes.
  sql/gcalc_tools.cc
        bugfixes.
  sql/gcalc_tools.h
        bugfixes.
  sql/item_geofunc.cc
        bugfixes.
  sql/spatial.cc
        bugfixes.

8 files changed, 1572 insertions, 330 deletions

diff --git a/mysql-test/r/gis-precise.result b/mysql-test/r/gis-precise.result
index c3f77f6680f..5adecfb5a35 100644
--- a/mysql-test/r/gis-precise.result
+++ b/mysql-test/r/gis-precise.result
@@ -189,7 +189,7 @@ st_touches(geomfromtext('polygon((0 0, 2 2, 0 4, 0 0))'), geomfromtext('point(1
 0
 select st_touches(geomfromtext('polygon((0 0, 2 2, 0 4, 0 0))'), geomfromtext('polygon((1 1.2, 1 0, 2 0, 1 1.2))'));
 st_touches(geomfromtext('polygon((0 0, 2 2, 0 4, 0 0))'), geomfromtext('polygon((1 1.2, 1 0, 2 0, 1 1.2))'))
-1
+0
 select st_touches(geomfromtext('polygon((0 0, 2 2, 0 4, 0 0))'), geomfromtext('polygon((1 1, 1 0, 2 0, 1 1))'));
 st_touches(geomfromtext('polygon((0 0, 2 2, 0 4, 0 0))'), geomfromtext('polygon((1 1, 1 0, 2 0, 1 1))'))
 1
@@ -257,7 +257,7 @@ ST_NUMGEOMETRIES((ST_UNION(ST_UNION(
 MULTILINESTRINGFROMTEXT('MULTILINESTRING((2 0,4 2,0 2,1 5,0 3,7 0,8 5,5 8),
                                                  (6 2,4 0,3 5,3 6,4 3,6 4,3 9,0 7,3 7,8 4,2 9,5 0),
                                           
-176
+185
 SELECT Round(ST_AREA(ST_BUFFER( ST_UNION(
 POLYGONFROMTEXT('POLYGON((7 7, 7 7, 7 4, 7 7, 7 7))'),
 POLYGONFROMTEXT('POLYGON((7 7, 4 7, 2 9, 7 6, 7 7))')), 1)), 6);
@@ -338,7 +338,7 @@ MULTILINESTRINGFROMTEXT('MULTILINESTRING((3 4, 3 1, 2 7, 4 2, 6 2, 1 5))')
 ST_NUMPOINTS(ST_EXTERIORRING(ST_BUFFER(ST_UNION(
 MULTILINESTRINGFROMTEXT('MULTILINESTRING((3 4, 2 5, 7 6, 1 8),(0 0 ,1 6 ,0 1, 8 9, 2 4, 6 1, 3 5, 4 8), (9 3, 5 4, 1 8, 4 2, 5 8, 3 0))' ) ,
 MULTILINESTRINGFROMTEXT('MULTILINESTRING((3 4, 3 1, 2 7, 4 2, 6 2
-280
+275
 SELECT ST_NUMGEOMETRIES(ST_DIFFERENCE (
 ST_UNION (
 MULTILINESTRINGFROMTEXT( ' MULTILINESTRING( ( 2 4 , 5 0 , 2 9 , 6 2 , 0 2 ) , ( 4 3 , 5 6 , 9 4 , 0 7 , 7 2 , 2 0 , 8 2 ) , ( 5 0 , 1 5 , 3 7 , 7 7 ) , ( 2 3 , 9 5 , 2 0 , 8 1 ) , ( 0 9 , 9 3 , 2 8 , 8 1 , 9 4 ) ) ' ),
@@ -354,7 +354,7 @@ MULTILINESTRINGFROMTEXT( ' MULTILINESTRING( ( 2 9 , 1 3 , 7 3 , 8 5 ) , ( 5 0 ,
 ST_NUMGEOMETRIES(ST_DIFFERENCE (
 ST_UNION (
 MULTILINESTRINGFROMTEXT( ' MULTILINESTRING( ( 2 4 , 5 0 , 2 9 , 6 2 , 0 2 ) , ( 4 3 , 5 6 , 9 4 , 0 7 , 7 2 , 2 0 , 8 2 ) , ( 5 0 , 1 5 , 3 7 , 7 7 ) , ( 2 3 , 9 5 , 2 0 , 8 1 ) , ( 0 9 , 9 3 , 2 8 , 8 1 , 9 4 )
-126
+123
 SELECT ST_NUMPOINTS(ST_EXTERIORRING(ST_BUFFER (
 ST_UNION (
 MULTILINESTRINGFROMTEXT( ' MULTILINESTRING( ( 7 3 , 1 8 , 4 0 , 7 9 ) , ( 5 4 , 9 8 , 7 4 , 3 7 ) , ( 5 8 , 5 4 , 9 2 , 5 6 ) , ( 4 0 , 3 2 , 0 1 , 3 9 ) , ( 2 0 , 3 5 , 9 5 , 0 9 ) ) ' ) ,
@@ -365,7 +365,7 @@ ST_NUMPOINTS(ST_EXTERIORRING(ST_BUFFER (
 ST_UNION (
 MULTILINESTRINGFROMTEXT( ' MULTILINESTRING( ( 7 3 , 1 8 , 4 0 , 7 9 ) , ( 5 4 , 9 8 , 7 4 , 3 7 ) , ( 5 8 , 5 4 , 9 2 , 5 6 ) , ( 4 0 , 3 2 , 0 1 , 3 9 ) , ( 2 0 , 3 5 , 9 5 , 0 9 ) ) ' ) ,
 MULTILINESTRI
-659
+653
 SELECT ASTEXT(ST_DIFFERENCE (
 POLYGONFROMTEXT( ' POLYGON( ( 2 2 , 2 8 , 8 8 , 8 2 , 2 2 ) , ( 4 4 , 4 6 , 6 6 , 6 4 , 4 4 ) ) ' ) ,
 ST_UNION (
@@ -416,7 +416,7 @@ ST_DISTANCE (     ST_DIFFERENCE (                                 MULTIPOLYGONFR
 NULL
 SELECT ST_NUMGEOMETRIES( ST_SYMDIFFERENCE ( ST_SYMDIFFERENCE ( ST_INTERSECTION ( MULTILINESTRINGFROMTEXT( ' MULTILINESTRING( ( 6 4 , 3 7 , 9 4 , 3 8 ) , ( 2 2 , 2 9 , 1 2 , 9 8 ) ) ' ) , ST_SYMDIFFERENCE ( MULTIPOINTFROMTEXT( ' MULTIPOINT( 6 1 , 3 8 , 3 3 , 0 6 , 7 2 , 3 4 ) ' ) , ST_BUFFER ( ST_UNION ( MULTIPOLYGONFROMTEXT( ' MULTIPOLYGON( ( ( 2 2 , 6 2 , 1 3 , 2 2 , 2 2 ) ) ) ' ) , GEOMETRYFROMTEXT( ' MULTILINESTRING( ( 1 4 , 9 9 , 3 0 , 6 6 ) , ( 3 5 , 1 0 , 5 8 , 6 1 ) , ( 8 9 , 6 1 , 5 1 , 6 2 ) , ( 2 2 , 7 5 , 5 8 , 6 9 , 3 0 ) , ( 8 0 , 8 4 , 6 7 , 5 5 ) ) ' ) ) , NUMPOINTS( EXTERIORRING( POLYGONFROMTEXT( ' POLYGON( ( 0 0 , 2 1 , 8 2 , 0 0 ) ) ' ) ) ) ) ) ) , ST_INTERSECTION ( POLYGONFROMTEXT( ' POLYGON( ( 2 3, 5 7 , 3 7 , 4 1 , 0 5, 2 3 ) ) ' ) , MULTILINESTRINGFROMTEXT( ' MULTILINESTRING( ( 2 3 , 1 4 , 6 4 , 9 1 , 3 4 , 1 8 ) , ( 9 9 , 0 3 , 1 7 , 9 9 ) ) ' ) ) ) , POLYGONFROMTEXT( ' POLYGON( ( 1 3, 7 2 , 1 5 , 3 8 , 5 0, 1 3) ) ' ) ) ) ;
 ST_NUMGEOMETRIES( ST_SYMDIFFERENCE ( ST_SYMDIFFERENCE ( ST_INTERSECTION ( MULTILINESTRINGFROMTEXT( ' MULTILINESTRING( ( 6 4 , 3 7 , 9 4 , 3 8 ) , ( 2 2 , 2 9 , 1 2 , 9 8 ) ) ' ) , ST_SYMDIFFERENCE ( MULTIPOINTFROMTEXT( ' MULTIPOINT( 6 1 , 3 8 , 3 3 , 0 6 
-27
+25
 SELECT ASTEXT(ST_INTERSECTION( GEOMETRYFROMTEXT('GEOMETRYCOLLECTION(LINESTRING(7 7,5.33333333333333 7),LINESTRING(5.33333333333333 7,0 7,5 8,5.33333333333333 7),LINESTRING(5.33333333333333 7,7 2,7 7),POLYGON((0 5,3 5,3 2,1 2,1 1,3 1,3 0,0 0,0 3,2 3,2 4,0 4,0 5)))'), geomETRYFROMTEXT(' MULTILINESTRING( ( 5 1 , 3 7 , 6 1 , 7 0 ) , ( 1 6 , 8 5 , 7 5 , 5 6 ) )') ));
 ASTEXT(ST_INTERSECTION( GEOMETRYFROMTEXT('GEOMETRYCOLLECTION(LINESTRING(7 7,5.33333333333333 7),LINESTRING(5.33333333333333 7,0 7,5 8,5.33333333333333 7),LINESTRING(5.33333333333333 7,7 2,7 7),POLYGON((0 5,3 5,3 2,1 2,1 1,3 1,3 0,0 0,0 3,2 3,2 4,0 4,0 5))
 MULTIPOINT(7 5,7 5.14285714285714,5.9 5.3,5.8 5.6,3 7)
diff --git a/mysql-test/r/gis.result b/mysql-test/r/gis.result
index b3993657182..190795855dd 100644
--- a/mysql-test/r/gis.result
+++ b/mysql-test/r/gis.result
@@ -850,7 +850,7 @@ mbroverlaps
 down,left,right,up
 SELECT GROUP_CONCAT(a2.name ORDER BY a2.name) AS mbrtouches   FROM t1 a1 JOIN t1 a2 ON MBRTouches(    a1.square, a2.square) WHERE a1.name = "center" GROUP BY a1.name;
 mbrtouches
-big,center,down,down2,left,left2,right,right2,small,up,up2
+down2,left2,right2,up2
 SELECT GROUP_CONCAT(a2.name ORDER BY a2.name) AS mbrwithin    FROM t1 a1 JOIN t1 a2 ON MBRWithin(     a1.square, a2.square) WHERE a1.name = "center" GROUP BY a1.name;
 mbrwithin
 big,center
@@ -871,7 +871,7 @@ overlaps
 down,left,right,up
 SELECT GROUP_CONCAT(a2.name ORDER BY a2.name) AS touches      FROM t1 a1 JOIN t1 a2 ON Touches(       a1.square, a2.square) WHERE a1.name = "center" GROUP BY a1.name;
 touches
-big,center,down,down2,left,left2,right,right2,small,up,up2
+down2,left2,right2,up2
 SELECT GROUP_CONCAT(a2.name ORDER BY a2.name) AS within       FROM t1 a1 JOIN t1 a2 ON Within(        a1.square, a2.square) WHERE a1.name = "center" GROUP BY a1.name;
 within
 big,center
diff --git a/sql/gcalc_slicescan.cc b/sql/gcalc_slicescan.cc
index 6f41a5fc371..07120d2e87e 100644
--- a/sql/gcalc_slicescan.cc
+++ b/sql/gcalc_slicescan.cc
@@ -116,6 +116,450 @@ void Gcalc_dyn_list::reset()
 }
 
 
+/* Internal coordinate operations implementations */
+
+void Gcalc_internal_coord::set_zero()
+{
+  int n_res= 0;
+  do
+  {
+    digits[n_res++]= 0;
+  } while (n_res < n_digits); 
+  sign= 0;
+}
+
+
+int Gcalc_internal_coord::is_zero() const
+{
+  int n_res= 0;
+  do
+  {
+    if (digits[n_res++] != 0)
+      return 0;
+  } while (n_res < n_digits); 
+  return 1;
+}
+
+
+#ifdef GCALC_CHECK_WITH_FLOAT
+long double Gcalc_internal_coord::get_double() const
+{
+  int n= 0;
+  long double res= 0.0;
+  do
+  {
+    res*= (long double) DIG_BASE;
+    res+= digits[n];
+  } while(++n < n_digits);
+
+  n= 0;
+  do
+  {
+    if (n & 1)
+      res/= (long double) C_SCALE;
+  } while(++n < n_digits);
+
+  if (sign)
+    res*= -1.0;
+  return res;
+}
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+
+
+static void do_add(Gcalc_internal_coord *result,
+                   const Gcalc_internal_coord *a,
+                   const Gcalc_internal_coord *b)
+{
+  DBUG_ASSERT(a->n_digits == b->n_digits);
+  DBUG_ASSERT(a->n_digits == result->n_digits);
+  int n_digit= a->n_digits-1;
+  coord_digit_t carry= 0;
+
+  do
+  {
+    if ((result->digits[n_digit]=
+          a->digits[n_digit] + b->digits[n_digit] + carry) >= DIG_BASE)
+    {
+      carry= 1;
+      result->digits[n_digit]-= DIG_BASE;
+    }
+    else
+      carry= 0;
+  } while (n_digit--);
+  DBUG_ASSERT(carry == 0);
+  result->sign= a->sign;
+}
+
+
+static void do_sub(Gcalc_internal_coord *result,
+                   const Gcalc_internal_coord *a,
+                   const Gcalc_internal_coord *b)
+{
+  DBUG_ASSERT(a->n_digits == b->n_digits);
+  DBUG_ASSERT(a->n_digits == result->n_digits);
+  int n_digit= a->n_digits-1;
+  coord_digit_t carry= 0;
+
+  do
+  {
+    if ((result->digits[n_digit]=
+          a->digits[n_digit] - b->digits[n_digit] - carry) < 0)
+    {
+      carry= 1;
+      result->digits[n_digit]+= DIG_BASE;
+    }
+    else
+      carry= 0;
+  } while (n_digit--);
+  DBUG_ASSERT(carry == 0);
+  if (a->sign && result->is_zero())
+    result->sign= 0;
+  else
+    result->sign= a->sign;
+}
+
+
+static int do_cmp(const Gcalc_internal_coord *a,
+                  const Gcalc_internal_coord *b)
+{
+  DBUG_ASSERT(a->n_digits == b->n_digits);
+  int n_digit= 0;
+
+  do
+  {
+    coord_digit_t d= a->digits[n_digit] - b->digits[n_digit];
+    if (d > 0)
+      return 1;
+    if (d < 0)
+      return -1;
+    n_digit++;
+  } while (n_digit < a->n_digits);
+
+  return 0;
+}
+
+
+#ifdef GCALC_CHECK_WITH_FLOAT
+static int de_check(long double a, long double b)
+{
+  long double d= a - b;
+  if (d < (long double) 1e-6 && d > (long double) -1e-6)
+    return 1;
+  printf("xxx\n");
+  return 0;
+}
+
+static int de_check1(long double a, long double b)
+{
+  long double d= a - b;
+  if (d < (long double) 1e-6 && d > (long double) -1e-6)
+    return 1;
+  return 0;
+}
+static int de_weak(long double a, long double b)
+{
+  long double d= a - b;
+  if (d < (long double) 1 && d > (long double) -1)
+    return 1;
+  return 0;
+}
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+
+
+void gcalc_mul_coord(Gcalc_internal_coord *result,
+                     const Gcalc_internal_coord *a,
+                     const Gcalc_internal_coord *b)
+{
+  DBUG_ASSERT(result->n_digits == a->n_digits + b->n_digits);
+  int n_a, n_b, n_res;
+  coord_digit_t carry= 0;
+
+  result->set_zero();
+  if (a->is_zero() || b->is_zero())
+    return;
+
+  n_a= a->n_digits - 1;
+  do
+  {
+    n_b= b->n_digits - 1;
+    do
+    {
+      coord2 mul= ((coord2) a->digits[n_a]) * b->digits[n_b] + carry +
+        result->digits[n_a + n_b + 1];
+      result->digits[n_a + n_b + 1]= mul % DIG_BASE;
+      carry= mul / DIG_BASE;
+    } while (n_b--);
+    if (carry)
+    {
+      for (n_res= n_a; (result->digits[n_res]+= carry) >= DIG_BASE; n_res--)
+      {
+        result->digits[n_res]-= DIG_BASE;
+        carry= 1;
+      }
+      carry= 0;
+    }
+  } while (n_a--);
+  result->sign= a->sign != b->sign;
+#ifdef GCALC_CHECK_WITH_FLOAT
+  DBUG_ASSERT(de_check(a->get_double() * b->get_double(),
+                       result->get_double()));
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+}
+
+
+void gcalc_add_coord(Gcalc_internal_coord *result,
+                     const Gcalc_internal_coord *a,
+                     const Gcalc_internal_coord *b)
+{
+  if (a->sign == b->sign)
+    do_add(result, a, b);
+  else
+  {
+    int cmp_res= do_cmp(a, b);
+    if (cmp_res == 0)
+      result->set_zero();
+    else if (cmp_res > 0)
+      do_sub(result, a, b);
+    else
+      do_sub(result, b, a);
+  }
+#ifdef GCALC_CHECK_WITH_FLOAT
+  DBUG_ASSERT(de_check(a->get_double() + b->get_double(),
+                       result->get_double()));
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+}
+
+
+void gcalc_sub_coord(Gcalc_internal_coord *result,
+                     const Gcalc_internal_coord *a,
+                     const Gcalc_internal_coord *b)
+{
+  if (a->sign != b->sign)
+    do_add(result, a, b);
+  else
+  {
+    int cmp_res= do_cmp(a, b);
+    if (cmp_res == 0)
+      result->set_zero();
+    else if (cmp_res > 0)
+      do_sub(result, a, b);
+    else
+    {
+      do_sub(result, b, a);
+      result->sign= 1 - result->sign;
+    }
+  }
+#ifdef GCALC_CHECK_WITH_FLOAT
+  DBUG_ASSERT(de_check(a->get_double() - b->get_double(),
+                       result->get_double()));
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+}
+
+
+int gcalc_cmp_coord(const Gcalc_internal_coord *a,
+                    const Gcalc_internal_coord *b)
+{
+  int result;
+  if (a->sign != b->sign)
+    return a->sign ? -1 : 1;
+  result= a->sign ? do_cmp(b, a) : do_cmp(a, b);
+#ifdef GCALC_CHECK_WITH_FLOAT
+  if (result == 0)
+    DBUG_ASSERT(de_check(a->get_double(), b->get_double()));
+  else if (result == 1)
+    DBUG_ASSERT(de_check1(a->get_double(), b->get_double()) ||
+                a->get_double() > b->get_double());
+  else
+    DBUG_ASSERT(de_check1(a->get_double(), b->get_double()) ||
+                a->get_double() < b->get_double());
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+  return result;
+}
+
+
+int Gcalc_coord1::set_double(double d)
+{
+  double ds= d * C_SCALE;
+  init();
+  if ((sign= ds < 0))
+    ds= -ds;
+  c[0]= (coord_digit_t) (ds / (double) DIG_BASE);
+  c[1]= (coord_digit_t) (ds - ((double) c[0]) * DIG_BASE);
+#ifdef GCALC_CHECK_WITH_FLOAT
+  DBUG_ASSERT(de_check(d, get_double()));
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+  return 0;
+} 
+
+
+void Gcalc_coord1::copy(const Gcalc_coord1 *from)
+{
+  c[0]= from->c[0];
+  c[1]= from->c[1];
+  sign= from->sign;
+}
+
+/* Internal coordinates implementation end */
+
+
+Gcalc_heap::Info *Gcalc_heap::new_point_info(double x, double y,
+                                             gcalc_shape_info shape)
+{
+  Info *result= (Info *)new_item();
+  if (!result)
+    return NULL;
+  *m_hook= result;
+  m_hook= &result->next;
+  m_n_points++;
+  result->x= x;
+  result->y= y;
+  result->shape= shape;
+  result->ix.set_double(x);
+  result->iy.set_double(y);
+  return result;
+}
+
+
+Gcalc_heap::Intersection_info *Gcalc_heap::new_intersection(
+    const Info *p1, const Info *p2,
+    const Info *p3, const Info *p4)
+{
+  Intersection_info *isc= (Intersection_info *)new_item();
+  if (!isc)
+    return 0;
+  isc->p1= p1;
+  isc->p2= p2;
+  isc->p3= p3;
+  isc->p4= p4;
+  *m_intersection_hook= isc;
+  m_intersection_hook= &isc->next;
+  return isc;
+}
+
+
+class Gcalc_coord3 : public Gcalc_internal_coord
+{
+  coord_digit_t c[COORD_BASE*3];
+  public:
+  void init()
+  {
+    n_digits= COORD_BASE*3;
+    digits= c;
+  }
+};
+
+
+static void calc_t(Gcalc_coord2 *t_a, Gcalc_coord2 *t_b,
+                   Gcalc_coord1 *b1x,
+                   Gcalc_coord1 *b1y,
+                   const Gcalc_heap::Info *p1,
+                   const Gcalc_heap::Info *p2,
+                   const Gcalc_heap::Info *p3,
+                   const Gcalc_heap::Info *p4)
+{
+  Gcalc_coord1 a2_a1x, a2_a1y;
+  Gcalc_coord1 b2x, b2y;
+  Gcalc_coord2 x1y2, x2y1;
+
+  a2_a1x.init();
+  a2_a1y.init();
+  x1y2.init();
+  x2y1.init();
+  t_a->init();
+  t_b->init();
+  b1y->init();
+  b1x->init();
+  b2x.init();
+  b2y.init();
+
+  gcalc_sub_coord(&a2_a1x, &p3->ix, &p1->ix);
+  gcalc_sub_coord(&a2_a1y, &p3->iy, &p1->iy);
+  gcalc_sub_coord(b1x, &p2->ix, &p1->ix);
+  gcalc_sub_coord(b1y, &p2->iy, &p1->iy);
+  gcalc_sub_coord(&b2x, &p4->ix, &p3->ix);
+  gcalc_sub_coord(&b2y, &p4->iy, &p3->iy);
+
+  gcalc_mul_coord(&x1y2, b1x, &b2y);
+  gcalc_mul_coord(&x2y1, &b2x, b1y);
+  gcalc_sub_coord(t_b, &x1y2, &x2y1);
+
+
+  gcalc_mul_coord(&x1y2, &a2_a1x, &b2y);
+  gcalc_mul_coord(&x2y1, &a2_a1y, &b2x);
+  gcalc_sub_coord(t_a, &x1y2, &x2y1);
+}
+
+
+inline void calc_t(Gcalc_coord2 *t_a, Gcalc_coord2 *t_b,
+                   Gcalc_coord1 *b1x,
+                   Gcalc_coord1 *b1y,
+                   const Gcalc_heap::Intersection_info *isc)
+{
+  calc_t(t_a, t_b, b1x, b1y, isc->p1, isc->p2, isc->p3, isc->p4);
+}
+
+
+void Gcalc_heap::Intersection_info::calc_xy(double *x, double *y) const
+{
+  double b0_x= p2->x - p1->x;
+  double b0_y= p2->y - p1->y;
+  double b1_x= p4->x - p3->x;
+  double b1_y= p4->y - p3->y;
+  double b0xb1= b0_x * b1_y - b0_y * b1_x;
+  double t= (p3->x - p1->x) * b1_y - (p3->y - p1->y) * b1_x;
+
+  t/= b0xb1;
+
+  *x= p1->x + b0_x * t;
+  *y= p1->y + b0_y * t;
+}
+
+
+#ifdef GCALC_CHECK_WITH_FLOAT
+void Gcalc_heap::Intersection_info::calc_xy_ld(long double *x,
+                                               long double *y) const
+{
+  long double b0_x= p2->x - p1->x;
+  long double b0_y= p2->y - p1->y;
+  long double b1_x= p4->x - p3->x;
+  long double b1_y= p4->y - p3->y;
+  long double b0xb1= b0_x * b1_y - b0_y * b1_x;
+  long double t= (p3->x - p1->x) * b1_y - (p3->y - p1->y) * b1_x;
+  long double cx, cy;
+
+  t/= b0xb1;
+
+  cx= (long double) p1->x + b0_x * t;
+  cy= (long double) p1->y + b0_y * t;
+
+  Gcalc_coord2 t_a, t_b;
+  Gcalc_coord1 yb, xb;
+  Gcalc_coord3 m1, m2, sum;
+
+  calc_t(&t_a, &t_b, &xb, &yb, this);
+  if (t_b.is_zero())
+  {
+    *x= p1->x;
+    *y= p1->y;
+    return;
+  }
+
+  m1.init();
+  m2.init();
+  sum.init();
+  gcalc_mul_coord(&m1, &p1->ix, &t_b);
+  gcalc_mul_coord(&m2, &xb, &t_a);
+  gcalc_add_coord(&sum, &m1, &m2);
+  *x= sum.get_double() / t_b.get_double();
+
+  gcalc_mul_coord(&m1, &p1->iy, &t_b);
+  gcalc_mul_coord(&m2, &yb, &t_a);
+  gcalc_add_coord(&sum, &m1, &m2);
+  *y= sum.get_double() / t_b.get_double();
+}
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+
+
 static inline void trim_node(Gcalc_heap::Info *node, Gcalc_heap::Info *prev_node)
 {
   if (!node)
@@ -127,13 +571,21 @@ static inline void trim_node(Gcalc_heap::Info *node, Gcalc_heap::Info *prev_node
 }
 
 
+static int cmp_point_info(const Gcalc_heap::Info *i0,
+                          const Gcalc_heap::Info *i1)
+{
+  int cmp_y= gcalc_cmp_coord(&i0->iy, &i1->iy);
+  if (cmp_y)
+    return cmp_y;
+  return gcalc_cmp_coord(&i0->ix, &i1->ix);
+}
+
+
 static int compare_point_info(const void *e0, const void *e1)
 {
   const Gcalc_heap::Info *i0= (const Gcalc_heap::Info *)e0;
   const Gcalc_heap::Info *i1= (const Gcalc_heap::Info *)e1;
-  if (!coord_eq(i0->y, i1->y))
-    return i0->y > i1->y;
-  return i0->x > i1->x;
+  return cmp_point_info(i0, i1) > 0;
 }
 
 
@@ -155,6 +607,7 @@ void Gcalc_heap::prepare_operation()
 
 void Gcalc_heap::reset()
 {
+#ifdef TMP_BLOCK
   if (!m_hook)
   {
     m_hook= &m_first;
@@ -164,10 +617,18 @@ void Gcalc_heap::reset()
 
   *m_hook= m_free;
   m_free= m_first;
+#endif /*TMP_BLOCK*/
+  if (m_n_points)
+  {
+    free_list(m_first);
+    free_list(m_first_intersection, m_intersection_hook);
+    m_intersection_hook= (Gcalc_dyn_list::Item **) &m_first_intersection;
+    m_n_points= 0;
+  }
   m_hook= &m_first;
-  m_n_points= 0;
 }
 
+
 int Gcalc_shape_transporter::int_single_point(gcalc_shape_info Info,
                                               double x, double y)
 {
@@ -229,6 +690,7 @@ void Gcalc_shape_transporter::int_complete()
 }
 
 
+#ifdef TMP_BLOCK
 inline int GET_DX_DY(double *dxdy,
                      const Gcalc_heap::Info *p0, const Gcalc_heap::Info *p1)
 {
@@ -238,6 +700,13 @@ inline int GET_DX_DY(double *dxdy,
          (*dxdy/= dy)>DBL_MAX ||
          (*dxdy)<-DBL_MAX;
 }
+#endif /*TMP_BLOCK*/
+inline void calc_dx_dy(Gcalc_scan_iterator::point *p)
+{
+  gcalc_sub_coord(&p->dx, &p->next_pi->ix, &p->pi->ix);
+  gcalc_sub_coord(&p->dy, &p->next_pi->iy, &p->pi->iy);
+}
+
 
 Gcalc_scan_iterator::Gcalc_scan_iterator(size_t blk_size) :
   Gcalc_dyn_list(blk_size,
@@ -268,14 +737,20 @@ void Gcalc_scan_iterator::init(Gcalc_heap *points)
 
   if (!(m_cur_pi= points->get_first()))
     return;
+  m_heap= points;
   m_cur_thread= 0;
   m_intersections= NULL;
+  m_cur_intersection= NULL;
   m_next_is_top_point= true;
   m_events= NULL;
   current_state= &state0;
   next_state= &state1;
   saved_state= &state_s;
+#ifdef TMP_BLOCK
   next_state->y= m_cur_pi->y;
+#endif /*TMP_BLOCK*/
+  next_state->intersection_scan= 0;
+  next_state->pi= m_cur_pi;
 }
 
 void Gcalc_scan_iterator::reset()
@@ -286,21 +761,36 @@ void Gcalc_scan_iterator::reset()
 }
 
 
-void Gcalc_scan_iterator::point::copy_core(point *from)
+void Gcalc_scan_iterator::point::copy_core(const point *from)
 {
+#ifdef TMP_BLOCK
   dx_dy= from->dx_dy;
   horiz_dir= from->horiz_dir;
+#endif /*TMP_BLOCK*/
   pi= from->pi;
   next_pi= from->next_pi;
   thread= from->thread;
+  dx.copy(&from->dx);
+  dy.copy(&from->dy);
 #ifdef TO_REMOVE
   from->next_link= this;
 #endif /*TO_REMOVE*/
 }
 
 
-int Gcalc_scan_iterator::point::compare_dx_dy(int horiz_dir_a, double dx_dy_a,
-                                              int horiz_dir_b, double dx_dy_b)
+void Gcalc_scan_iterator::point::copy_all(const point *from)
+{
+  pi= from->pi;
+  next_pi= from->next_pi;
+  thread= from->thread;
+  dx.copy(&from->dx);
+  dy.copy(&from->dy);
+  intersection_link= from->intersection_link;
+  event= from->event;
+}
+#ifdef TMP_BLOCK
+int Gcalc_scan_iterator::point::cmp_dx_dy(int horiz_dir_a, double dx_dy_a,
+                                          int horiz_dir_b, double dx_dy_b)
 {
   if (!horiz_dir_a && !horiz_dir_b)
   {
@@ -323,7 +813,169 @@ int Gcalc_scan_iterator::point::cmp_dx_dy(const point *p) const
     return p->is_bottom() ? 0 : -1;
   if (p->is_bottom())
     return 1;
-  return compare_dx_dy(horiz_dir, dx_dy, p->horiz_dir, p->dx_dy);
+  return cmp_dx_dy(horiz_dir, dx_dy, p->horiz_dir, p->dx_dy);
+}
+#endif /*TMP_BLOCK*/
+int Gcalc_scan_iterator::point::cmp_dx_dy(const Gcalc_coord1 *dx_a,
+                                          const Gcalc_coord1 *dy_a,
+                                          const Gcalc_coord1 *dx_b,
+                                          const Gcalc_coord1 *dy_b)
+{
+  Gcalc_coord2 dx_a_dy_b;
+  Gcalc_coord2 dy_a_dx_b;
+  dx_a_dy_b.init();
+  dy_a_dx_b.init();
+  gcalc_mul_coord(&dx_a_dy_b, dx_a, dy_b);
+  gcalc_mul_coord(&dy_a_dx_b, dy_a, dx_b);
+
+  return gcalc_cmp_coord(&dx_a_dy_b, &dy_a_dx_b);
+}
+
+
+int Gcalc_scan_iterator::point::cmp_dx_dy(const Gcalc_heap::Info *p1,
+                                          const Gcalc_heap::Info *p2,
+                                          const Gcalc_heap::Info *p3,
+                                          const Gcalc_heap::Info *p4)
+{
+  Gcalc_coord1 dx_a, dy_a, dx_b, dy_b;
+  dx_a.init();
+  dx_b.init();
+  dy_a.init();
+  dy_b.init();
+  gcalc_sub_coord(&dx_a, &p2->ix, &p1->ix);
+  gcalc_sub_coord(&dy_a, &p2->iy, &p1->iy);
+  gcalc_sub_coord(&dx_b, &p4->ix, &p3->ix);
+  gcalc_sub_coord(&dy_b, &p4->iy, &p3->iy);
+  return cmp_dx_dy(&dx_a, &dy_a, &dx_b, &dy_b);
+}
+
+
+int Gcalc_scan_iterator::point::cmp_dx_dy(const point *p) const
+{
+  if (is_bottom())
+    return p->is_bottom() ? 0 : -1;
+  if (p->is_bottom())
+    return 1;
+  return cmp_dx_dy(&dx, &dy, &p->dx, &p->dy);
+}
+
+
+#ifdef GCALC_CHECK_WITH_FLOAT
+void Gcalc_scan_iterator::point::calc_x(long double *x, long double y,
+                                        long double ix) const
+{
+  if (fabsl(dy.get_double()) < (long double) 1e-15)
+  {
+    *x= ix;
+  }
+  else
+    *x= (long double) pi->x + dx.get_double()/dy.get_double() * (y - pi->y);
+}
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+
+
+static int cmp_sp_pi(const Gcalc_scan_iterator::point *sp,
+                     const Gcalc_heap::Info *pi)
+{
+  Gcalc_coord1 dx_pi, dy_pi;
+  Gcalc_coord2 dx_sp_dy_pi, dy_sp_dx_pi;
+
+  if (!sp->next_pi)
+    return cmp_point_info(sp->pi, pi);
+
+  dx_pi.init();
+  dy_pi.init();
+  dx_sp_dy_pi.init();
+  dy_sp_dx_pi.init();
+
+
+  gcalc_sub_coord(&dx_pi, &pi->ix, &sp->pi->ix);
+  gcalc_sub_coord(&dy_pi, &pi->iy, &sp->pi->iy);
+  gcalc_mul_coord(&dx_sp_dy_pi, &sp->dx, &dy_pi);
+  gcalc_mul_coord(&dy_sp_dx_pi, &sp->dy, &dx_pi);
+
+  int result= gcalc_cmp_coord(&dx_sp_dy_pi, &dy_sp_dx_pi);
+#ifdef GCALC_CHECK_WITH_FLOAT
+  long double sp_x;
+  sp->calc_x(&sp_x, pi->y, pi->x);
+  if (result == 0)
+    DBUG_ASSERT(de_check1(sp->dy.get_double(), 0.0) ||
+                de_check(sp_x, pi->x));
+  if (result < 0)
+    DBUG_ASSERT(de_check1(sp->dy.get_double(), 0.0) ||
+                de_check1(sp_x, pi->x) ||
+                sp_x < pi->x);
+  if (result > 0)
+    DBUG_ASSERT(de_check1(sp->dy.get_double(), 0.0) ||
+                de_check1(sp_x, pi->x) ||
+                sp_x > pi->x);
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+  return result;
+}
+
+
+static void calc_cmp_sp_sp_exp(Gcalc_coord3 *result,
+                               const Gcalc_scan_iterator::point *a,
+                               const Gcalc_scan_iterator::point *b,
+                               const Gcalc_coord1 *ly)
+{
+  Gcalc_coord2 x_dy, dx_ly, sum;
+
+  x_dy.init();
+  dx_ly.init();
+  sum.init();
+  result->init();
+
+  gcalc_mul_coord(&x_dy, &a->pi->ix, &a->dy);
+  gcalc_mul_coord(&dx_ly, &a->dx, ly);
+  gcalc_add_coord(&sum, &x_dy, &dx_ly);
+  gcalc_mul_coord(result, &sum, &b->dy);
+}
+
+
+static int cmp_sp_sp_cnt(const Gcalc_scan_iterator::point *a,
+                         const Gcalc_scan_iterator::point *b,
+                         const Gcalc_coord1 *y)
+{
+  Gcalc_coord1 lya, lyb;
+  Gcalc_coord3 a_exp, b_exp;
+
+  lya.init();
+  lyb.init();
+  gcalc_sub_coord(&lya, y, &a->pi->iy);
+  gcalc_sub_coord(&lyb, y, &b->pi->iy);
+
+  calc_cmp_sp_sp_exp(&a_exp, a, b, &lya);
+  calc_cmp_sp_sp_exp(&b_exp, b, a, &lyb);
+
+  int result= gcalc_cmp_coord(&a_exp, &b_exp);
+#ifdef GCALC_CHECK_WITH_FLOAT
+  long double a_x, b_x;
+  a->calc_x(&a_x, y->get_double(), 0);
+  b->calc_x(&b_x, y->get_double(), 0);
+  if (result == 0)
+    DBUG_ASSERT(de_check(a_x, b_x));
+  if (result < 0)
+    DBUG_ASSERT(de_check1(a_x, b_x) || a_x < b_x);
+  if (result > 0)
+    DBUG_ASSERT(de_check1(a_x, b_x) || a_x > b_x);
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+  return result;
+}
+
+
+static int cmp_sp_sp(const Gcalc_scan_iterator::point *a,
+                     const Gcalc_scan_iterator::point *b,
+                     const Gcalc_heap::Info *pi)
+{
+  if (a->event == scev_none && b->event == scev_none)
+    return cmp_sp_sp_cnt(a, b, &pi->iy);
+  if (a->event == scev_none)
+    return cmp_sp_pi(a, pi);
+  if (b->event == scev_none)
+    return -1 * cmp_sp_pi(b, pi);
+
+  return 0;
 }
 
 
@@ -366,7 +1018,7 @@ int Gcalc_scan_iterator::arrange_event()
       continue;
     if (!(new_sp= new_slice_point()))
       return 1;
-    *new_sp= *sp;
+    new_sp->copy_all(sp);
     *ae_hook= new_sp;
     ae_hook= &new_sp->next;
 #ifdef TO_REMOVE
@@ -420,10 +1072,12 @@ int Gcalc_scan_iterator::insert_top_point()
   sp0->pi= m_cur_pi;
   sp0->next_pi= m_cur_pi->left;
   sp0->thread= m_cur_thread++;
+#ifdef TMP_BLOCK
   sp0->x= coord_to_float(m_cur_pi->x);
+#endif /*TMP_BLOCK*/
   if (m_cur_pi->left)
   {
-    sp0->horiz_dir= GET_DX_DY(&sp0->dx_dy, m_cur_pi, m_cur_pi->left);
+    calc_dx_dy(sp0);
     sp0->event= scev_thread;
 
     /*Now just to increase the size of m_slice0 to be same*/
@@ -436,15 +1090,13 @@ int Gcalc_scan_iterator::insert_top_point()
       if (!(sp1= new_slice_point()))
         return 1;
       sp1->event= sp0->event= scev_two_threads;
-#ifdef TO_REMOVE
-      sp1->event_pair= sp0;
-      sp0->event_pair= sp1;
-#endif /*TO_REMOVE*/
       sp1->pi= m_cur_pi;
       sp1->next_pi= m_cur_pi->right;
       sp1->thread= m_cur_thread++;
+#ifdef TMP_BLOCK
       sp1->x= sp0->x;
-      sp1->horiz_dir= GET_DX_DY(&sp1->dx_dy, m_cur_pi, m_cur_pi->right);
+#endif /*TMP_BLOCK*/
+      calc_dx_dy(sp1);
       /* We have two threads so should decide which one will be first */
       if (sp0->cmp_dx_dy(sp1)>0)
       {
@@ -463,17 +1115,20 @@ int Gcalc_scan_iterator::insert_top_point()
   else
   {
     sp0->event= scev_single_point;
+#ifdef TMP_BLOCK
     sp0->horiz_dir= 0;
     sp0->dx_dy= 0.0;
+#endif /*TMP_BLOCK*/
   }
 
 
   /* We need to find the place to insert. */
-  for (; sp && (sp->x < sp0->x); prev_hook= &sp->next, sp=sp->get_next())
+  for (; sp && cmp_sp_pi(sp, m_cur_pi) < 0;
+         prev_hook= &sp->next, sp=sp->get_next())
   {}
 
   next_state->event_position_hook= prev_hook;
-  if (sp && coord_eq(sp->x, sp0->x))
+  if (sp && cmp_sp_pi(sp, m_cur_pi) == 0)
   {
     next_state->event_position= sp;
     do
@@ -482,7 +1137,7 @@ int Gcalc_scan_iterator::insert_top_point()
         sp->event= scev_intersection;
       prev_hook= &sp->next;
       sp= sp->get_next();
-    } while (sp && coord_eq(sp->x, sp0->x));
+    } while (sp && cmp_sp_pi(sp, m_cur_pi) == 0);
   }
   else
     next_state->event_position= sp0;
@@ -503,44 +1158,88 @@ int Gcalc_scan_iterator::insert_top_point()
 }
 
 
+#ifndef NO_TESTING
+const char *pev(int ev)
+{
+  switch (ev)
+  {
+    case scev_none:
+      return "n";
+    case scev_thread:
+      return "t";
+    case scev_two_threads:
+      return "tt";
+    case scev_end:
+      return "e";
+    case scev_two_ends:
+      return "ee";
+    case scev_intersection:
+      return "i";
+    case scev_point:
+      return "p";
+    case scev_single_point:
+      return "sp";
+  };
+  return "fck";
+}
+extern int ca_counter;
+#endif /*NO_TESTING*/
 int Gcalc_scan_iterator::normal_scan()
 {
   point *sp;
   Gcalc_dyn_list::Item **sp_hook;
   Gcalc_heap::Info *next_pi;
-  point *first_bottom_point= NULL;
+  point *first_bottom_point;
 
   if (m_next_is_top_point && insert_top_point())
     return 1;
 
   for (next_pi= m_cur_pi->get_next();
-       next_pi &&
-         coord_eq(m_cur_pi->x, next_pi->x) &&
-         coord_eq(m_cur_pi->y, next_pi->y);
+       next_pi && cmp_point_info(m_cur_pi, next_pi) == 0;
        next_pi= next_pi->get_next())
   {
-    DBUG_ASSERT(coord_eq(next_state->event_position->x, next_pi->x));
     next_state->clear_event_position();
     m_next_is_top_point= true;
+    first_bottom_point= NULL;
     for (sp= next_state->slice,
          sp_hook= (Gcalc_dyn_list::Item **) &next_state->slice; sp;
          sp_hook= &sp->next, sp= sp->get_next())
     {
+#ifndef NO_TESTING
+    //  if (ca_counter == 21)
+        printf("%s%d\t", pev(sp->event), sp->thread);
+#endif /*NO_TESTING*/
       if (sp->next_pi == next_pi) /* End of the segment */
       {
+#ifdef TMP_BLOCK
         sp->x= coord_to_float(next_pi->x);
         sp->pi= next_pi;
+#endif /*TMP_BLOCK*/
+        if (cmp_point_info(sp->pi, next_pi))
+          sp->pi= next_pi;
         sp->next_pi= next_pi->left;
         m_next_is_top_point= false;
         if (next_pi->is_bottom())
         {
-          if (first_bottom_point)
+          if (sp->event == scev_thread)
+            sp->event= scev_single_point;
+          else if (sp->event == scev_two_threads)
+          {
+            if (sp->get_next() && sp->get_next()->pi == sp->pi)
+              sp->get_next()->event= scev_thread;
+            else if (sp != next_state->slice)
+            {
+              point *fnd_sp;
+              for (fnd_sp= next_state->slice; fnd_sp->get_next() != sp;
+                   fnd_sp= fnd_sp->get_next());
+              DBUG_ASSERT(fnd_sp->pi == sp->pi);
+              fnd_sp->event= scev_thread;
+            }
+            sp->event= scev_single_point;
+          }
+          else if (first_bottom_point)
           {
             first_bottom_point->event= sp->event= scev_two_ends;
-#ifdef TO_REMOVE
-            first_bottom_point->event_pair= sp;
-            sp->event_pair= first_bottom_point;
-#endif /*TO_REMOVE*/
           }
           else
           {
@@ -550,21 +1249,52 @@ int Gcalc_scan_iterator::normal_scan()
         }
         else
         {
-          sp->event= scev_point;
-          sp->horiz_dir= GET_DX_DY(&sp->dx_dy, next_pi, next_pi->left);
+          if ((sp->event & (scev_point | scev_thread | scev_two_threads)) == 0)
+            sp->event= scev_point;
+          calc_dx_dy(sp);
         }
         mark_event_position1(sp, sp_hook);
       }
-      else if (coord_eq(sp->x, next_pi->x))
+      else if (sp->event || (cmp_sp_pi(sp, next_pi) == 0))
       {
         if (!sp->event)
           sp->event= scev_intersection;
         mark_event_position1(sp, sp_hook);
       }
     }
+#ifndef NO_TESTING
+    //if (ca_counter == 21)
+      printf("\n");
+#endif /*NO_TESTING*/
     m_cur_pi= next_pi;
-    if (m_next_is_top_point && insert_top_point())
-      return 1;
+    if (m_next_is_top_point)
+    {
+      if (insert_top_point())
+        return 1;
+      /* Set proper values to the event position */
+      /* TODO: can be done faster                */
+      next_state->clear_event_position();
+      if (next_state->slice->event)
+        mark_event_position1(next_state->slice,
+          (Gcalc_dyn_list::Item **) &next_state->slice);
+#ifndef NO_TESTING
+      //if (ca_counter == 21)
+        printf("*%s%d\t", pev(next_state->slice->event), next_state->slice->thread);
+#endif /*NO_TESTING*/
+      for (sp= next_state->slice; sp->get_next(); sp= sp->get_next())
+      {
+#ifndef NO_TESTING
+      //if (ca_counter == 21)
+        printf("%s%d\t", pev(sp->get_next()->event), sp->get_next()->thread);
+#endif /*NO_TESTING*/
+        if (sp->get_next()->event)
+          mark_event_position1(sp->get_next(), &sp->next);
+      }
+#ifndef NO_TESTING
+      //if (ca_counter == 21)
+        printf("\n");
+#endif /*NO_TESTING*/
+    }
   }
 
   /* Swap current <-> next */
@@ -580,6 +1310,19 @@ int Gcalc_scan_iterator::normal_scan()
   point *sp0= current_state->slice;
   point *sp1= next_state->slice;
   point *prev_sp1= NULL;
+#ifndef NO_TESTING
+  //if (ca_counter == 21)
+  {
+    point *sp= current_state->slice;
+    printf("After arrange\n");
+    for (; sp; sp= sp->get_next())
+      printf("%s%d\t", pev(sp->event), sp->thread);
+    printf("\nEvent\n");
+    for (sp= m_events; sp; sp= sp->get_next())
+      printf("%s%d\t", pev(sp->event), sp->thread);
+    printf("\n");
+  }
+#endif /*NO_TESTING*/
 
   if (!(m_cur_pi= next_pi))
   {
@@ -592,8 +1335,12 @@ int Gcalc_scan_iterator::normal_scan()
     return 0;
   }
   
+  next_state->intersection_scan= 0;
+  next_state->pi= m_cur_pi;
   Gcalc_heap::Info *cur_pi= m_cur_pi;
+#ifdef TMP_BLOCK
   next_state->y= coord_to_float(cur_pi->y);
+#endif /*TMP_BLOCK*/
 
 
   first_bottom_point= NULL;
@@ -603,9 +1350,12 @@ int Gcalc_scan_iterator::normal_scan()
 
   for (; sp0; sp0= sp0->get_next())
   {
+    DBUG_ASSERT(!sp0->is_bottom());
     if (sp0->next_pi == cur_pi) /* End of the segment */
     {
+#ifdef TMP_BLOCK
       sp1->x= coord_to_float(cur_pi->x);
+#endif /*TMP_BLOCK*/
       sp1->pi= cur_pi;
       sp1->thread= sp0->thread;
       sp1->next_pi= cur_pi->left;
@@ -625,16 +1375,12 @@ int Gcalc_scan_iterator::normal_scan()
 	else
         {
           first_bottom_point->event= sp1->event= scev_two_ends;
-#ifdef TO_REMOVE
-          sp1->event_pair= first_bottom_point;
-          first_bottom_point->event_pair= sp1;
-#endif /*TO_REMOVE*/
         }
       }
       else
       {
         sp1->event= scev_point;
-	sp1->horiz_dir= GET_DX_DY(&sp1->dx_dy, m_cur_pi, m_cur_pi->left);
+        calc_dx_dy(sp1);
       }
       mark_event_position1(sp1,
         prev_sp1 ? &prev_sp1->next :
@@ -644,10 +1390,12 @@ int Gcalc_scan_iterator::normal_scan()
     {
       /* Cut current string with the height of the new point*/
       sp1->copy_core(sp0);
+#ifdef TMP_BLOCK
       sp1->x= sp1->horiz_dir ? coord_to_float(cur_pi->x) :
 	(coord_to_float(sp1->pi->x) +
 	 (next_state->y-coord_to_float(sp1->pi->y)) * sp1->dx_dy);
-      if (coord_eq(sp1->x, cur_pi->x))
+#endif /*TMP_BLOCK*/
+      if (cmp_sp_pi(sp1, cur_pi) == 0)
       {
         mark_event_position1(sp1,
           prev_sp1 ? &prev_sp1->next :
@@ -659,7 +1407,7 @@ int Gcalc_scan_iterator::normal_scan()
     }
 
     intersections_found= intersections_found ||
-                         (prev_sp1 && prev_sp1->x > sp1->x);
+                         (prev_sp1 && cmp_sp_sp(prev_sp1, sp1, cur_pi) > 0);
 
     prev_sp1= sp1;
     sp1= sp1->get_next();
@@ -674,6 +1422,16 @@ int Gcalc_scan_iterator::normal_scan()
     free_list(sp1);
   }
 
+#ifndef NO_TESTING
+  //if (ca_counter == 21)
+  {
+    point *sp= next_state->slice;
+    printf("After slice\n");
+    for (; sp; sp= sp->get_next())
+      printf("%s%d\t", pev(sp->event), sp->thread);
+    printf("\n");
+  }
+#endif /*NO_TESTING*/
   if (intersections_found)
     return handle_intersections();
 
@@ -681,16 +1439,20 @@ int Gcalc_scan_iterator::normal_scan()
 }
 
 
-#define INTERSECTION_ZERO 0.000000000001
-
+#ifndef NO_TESTING
+int isc_counter= 0;
+#endif /*NO_TESTING*/
 int Gcalc_scan_iterator::add_intersection(int n_row,
                                           const point *a, const point *b,
 		                          Gcalc_dyn_list::Item ***p_hook)
 {
+  const point *a0= a->intersection_link;
+  const point *b0= b->intersection_link;
   intersection *isc= new_intersection();
 
   if (!isc)
     return 1;
+
   m_n_intersections++;
   **p_hook= isc;
   *p_hook= &isc->next;
@@ -698,34 +1460,17 @@ int Gcalc_scan_iterator::add_intersection(int n_row,
   isc->thread_a= a->thread;
   isc->thread_b= b->thread;
 
-  /* intersection_normal */
-  const point *a0= a->intersection_link;
-  const point *b0= b->intersection_link;
-  DBUG_ASSERT(!a0->horiz_dir || !b0->horiz_dir);
-
-  if (!a0->horiz_dir && !b0->horiz_dir)
+  isc->ii= m_heap->new_intersection(a0->pi, a0->next_pi,
+                                    b0->pi, b0->next_pi);
+#ifndef NO_TESTING
+  //if (isc_counter == 40)
   {
-    double b0_x= a0->next_pi->x - a0->pi->x;
-    double b0_y= a0->next_pi->y - a0->pi->y;
-    double b1_x= b0->next_pi->x - b0->pi->x;
-    double b1_y= b0->next_pi->y - b0->pi->y;
-    double b1xb0= b1_x * b0_y - b1_y * b0_x;
-    double t= (a0->pi->x - b0->pi->x) * b0_y - (a0->pi->y - b0->pi->y) * b0_x;
-    if (fabs(b1xb0) < INTERSECTION_ZERO)
-    {
-      isc->y= current_state->y;
-      isc->x= a0->x;
-      return 0;
-    }
-
-    t/= b1xb0;
-    isc->x= b0->pi->x + b1_x*t;
-    isc->y= b0->pi->y + b1_y*t;
-    return 0;
+    long double ix, iy;
+    isc->ii->calc_xy_ld(&ix, &iy);
+    printf("%d\t%d\t%.20LG\t%.20LG\t%d\n", isc->thread_a, isc->thread_b, ix, iy, isc->n_row);
   }
-  isc->y= next_state->y;
-  isc->x= a0->horiz_dir ? b->x : a->x;
-  return 0;
+#endif /*NO_TESTING*/
+  return isc->ii == NULL;
 }
 
 
@@ -733,6 +1478,10 @@ int Gcalc_scan_iterator::find_intersections()
 {
   Gcalc_dyn_list::Item **hook;
 
+#ifndef NO_TESTING
+  ++isc_counter;
+  printf("Looking for intersections\n");
+#endif /*NO_TESTING*/
   m_n_intersections= 0;
   {
     /* Set links between slicepoints */
@@ -743,6 +1492,15 @@ int Gcalc_scan_iterator::find_intersections()
       DBUG_ASSERT(!sp0->is_bottom());
       DBUG_ASSERT(sp0->thread == sp1->thread);
       sp1->intersection_link= sp0;
+#ifndef NO_TESTING
+      //if (isc_counter == 40)
+      {
+        long double spx, spx1;
+        sp0->calc_x(&spx, current_state->pi->y, current_state->pi->x);
+        sp1->calc_x(&spx1, m_cur_pi->y, m_cur_pi->x);
+        printf("%d\t%.20LG\t%.20LG\n", sp0->thread, spx, spx1);
+      }
+#endif /*NO_TESTING*/
     }
   }
 
@@ -761,7 +1519,7 @@ int Gcalc_scan_iterator::find_intersections()
       point *s1= prev_s1->get_next();
       if (!s1)
         break;
-      if (prev_s1->x <= s1->x)
+      if (cmp_sp_sp(prev_s1, s1, m_cur_pi) <= 0)
       {
         pprev_s1= (point **) &prev_s1->next;
         continue;
@@ -783,19 +1541,250 @@ int Gcalc_scan_iterator::find_intersections()
 }
 
 
-static int compare_intersections(const void *e0, const void *e1)
+class Gcalc_coord4 : public Gcalc_internal_coord
+{
+  coord_digit_t c[COORD_BASE*4];
+  public:
+  void init()
+  {
+    n_digits= COORD_BASE*4;
+    digits= c;
+  }
+};
+
+class Gcalc_coord5 : public Gcalc_internal_coord
+{
+  coord_digit_t c[COORD_BASE*5];
+  public:
+  void init()
+  {
+    n_digits= COORD_BASE*5;
+    digits= c;
+  }
+};
+
+
+static void calc_isc_exp(Gcalc_coord5 *exp,
+                         const Gcalc_coord2 *bb2,
+                         const Gcalc_coord1 *ya1,
+                         const Gcalc_coord2 *bb1,
+                         const Gcalc_coord1 *yb1,
+                         const Gcalc_coord2 *a21_b1)
+{
+  Gcalc_coord3 p1, p2, sum;
+  p1.init();
+  p2.init();
+  sum.init();
+  exp->init();
+
+  gcalc_mul_coord(&p1, ya1, bb1);
+  gcalc_mul_coord(&p2, yb1, a21_b1);
+  gcalc_add_coord(&sum, &p1, &p2);
+  gcalc_mul_coord(exp, bb2, &sum);
+}
+
+
+#ifdef TMP_BLOCK
+static void calc_aa1_b(Gcalc_coord2 *res,
+                       const Gcalc_heap::Info *a0,
+                       const Gcalc_heap::Info *a1,
+                       const Gcalc_coord1 *xb,
+                       const Gcalc_coord1 *yb)
+{
+  Gcalc_coord1 aa1_x, aa1_y;
+  Gcalc_coord2 p1, p2;
+  res->init();
+  aa1_x.init();
+  aa1_y.init();
+  p1.init();
+  p2.init();
+
+  gcalc_sub_coord(&aa1_x, &a1->ix, &a0->ix);
+  gcalc_sub_coord(&aa1_y, &a1->iy, &a0->iy);
+  gcalc_mul_coord(&p1, &aa1_x, yb);
+  gcalc_mul_coord(&p2, &aa1_y, xb);
+  gcalc_sub_coord(res, &p1, &p2);
+}
+
+
+static int cmp_intersections_y(const Gcalc_heap::Intersection_info *i1,
+                               const Gcalc_heap::Intersection_info *i2)
+{
+  Gcalc_coord2 t_a1, t_b1;
+  Gcalc_coord2 t_a2, t_b2;
+  Gcalc_coord1 yb1, yb2;
+  Gcalc_coord1 xb1, xb2;
+  Gcalc_coord5 exp_a, exp_b;
+
+  calc_t(&t_a1, &t_b1, &xb1, &yb1, i1);
+  calc_t(&t_a2, &t_b2, &xb2, &yb2, i2);
+
+  calc_isc_exp(&exp_a, &t_b2, &i1->p1->iy, &t_b1, &yb1, &t_a1);
+  calc_isc_exp(&exp_b, &t_b1, &i2->p1->iy, &t_b2, &yb2, &t_a2);
+
+  int result= gcalc_cmp_coord(&exp_a, &exp_b);
+#ifdef GCALC_CHECK_WITH_FLOAT
+  long double x1, y1, x2,y2;
+  i1->calc_xy_ld(&x1, &y1);
+  i2->calc_xy_ld(&x2, &y2);
+
+  if (result == 0)
+    DBUG_ASSERT(de_check(y1, y2));
+  if (result < 0)
+    DBUG_ASSERT(de_check1(y1, y2) || y1 < y2);
+  if (result > 0)
+    DBUG_ASSERT(de_check1(y1, y2) || y1 > y2);
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+  return result;
+}
+
+
+static int compare_intersections(const void *e1, const void *e2)
 {
-  Gcalc_scan_iterator::intersection *i0= (Gcalc_scan_iterator::intersection *)e0;
   Gcalc_scan_iterator::intersection *i1= (Gcalc_scan_iterator::intersection *)e1;
+  Gcalc_scan_iterator::intersection *i2= (Gcalc_scan_iterator::intersection *)e2;
+  int result= cmp_intersections_y(i1->ii, i2->ii);
+  if (result != 0)
+    return result > 0;
+  return (i1->n_row > i2->n_row);
+}
+
+#endif /*TMP_BLOCK*/
+
+#ifndef NO_TESTING
+extern int ca_counter;
+#endif /*NO_TESTING*/
+static int cmp_intersections(const Gcalc_heap::Intersection_info *i1,
+                             const Gcalc_heap::Intersection_info *i2)
+{
+  Gcalc_coord2 t_a1, t_b1;
+  Gcalc_coord2 t_a2, t_b2;
+  Gcalc_coord1 yb1, yb2;
+  Gcalc_coord1 xb1, xb2;
+  Gcalc_coord5 exp_a, exp_b;
+  int result;
+
+  calc_t(&t_a1, &t_b1, &xb1, &yb1, i1);
+  calc_t(&t_a2, &t_b2, &xb2, &yb2, i2);
+
+  calc_isc_exp(&exp_a, &t_b2, &i1->p1->iy, &t_b1, &yb1, &t_a1);
+  calc_isc_exp(&exp_b, &t_b1, &i2->p1->iy, &t_b2, &yb2, &t_a2);
+
+  result= gcalc_cmp_coord(&exp_a, &exp_b);
+#ifdef GCALC_CHECK_WITH_FLOAT
+  long double x1, y1, x2, y2;
+  i1->calc_xy_ld(&x1, &y1);
+  i2->calc_xy_ld(&x2, &y2);
+
+  if (result == 0)
+    DBUG_ASSERT(de_weak(y1, y2));
+#ifndef NO_TESTING
+  if (ca_counter == 7)
+    printf("77");
+#endif /*NO_TESTING*/
+  if (result < 0)
+    DBUG_ASSERT(de_weak(y1, y2) || y1 < y2);
+  if (result > 0)
+    DBUG_ASSERT(de_weak(y1, y2) || y1 > y2);
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+
+  if (result != 0)
+    return result;
+
+
+  calc_isc_exp(&exp_a, &t_b2, &i1->p1->ix, &t_b1, &xb1, &t_a1);
+  calc_isc_exp(&exp_b, &t_b1, &i2->p1->ix, &t_b2, &xb2, &t_a2);
+  result= gcalc_cmp_coord(&exp_a, &exp_b);
+#ifdef GCALC_CHECK_WITH_FLOAT
+  if (result == 0)
+    DBUG_ASSERT(de_weak(x1, x2));
+  if (result < 0)
+    DBUG_ASSERT(de_weak(x1, x2) || x1 < x2);
+  if (result > 0)
+    DBUG_ASSERT(de_weak(x1, x2) || x1 > x2);
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+  return result;
+}
 
-  if (fabs(i0->y - i1->y) > 0.00000000000001)
-    return i0->y > i1->y;
+static int compare_intersections(const void *e1, const void *e2)
+{
+  Gcalc_scan_iterator::intersection *i1= (Gcalc_scan_iterator::intersection *)e1;
+  Gcalc_scan_iterator::intersection *i2= (Gcalc_scan_iterator::intersection *)e2;
+  int result= cmp_intersections(i1->ii, i2->ii);
+  if (result != 0)
+    return result > 0;
+  return (i1->n_row > i2->n_row);
+}
 
-  if (i0->n_row != i1->n_row)
-    return i0->n_row > i1->n_row;
-  if (!coord_eq(i0->y, i1->y))
-    return i0->y > i1->y;
-  return i0->x > i1->x;
+inline int intersections_eq(const Gcalc_heap::Intersection_info *i1,
+                            const Gcalc_heap::Intersection_info *i2)
+{
+  return cmp_intersections(i1, i2) == 0;
+}
+
+
+#ifdef TMP_BLOCK
+static void calc_isc_sp_exp(Gcalc_coord4 *exp,
+                            const Gcalc_coord2 *bb,
+                            const Gcalc_coord1 *x1,
+                            const Gcalc_coord1 *y1,
+                            const Gcalc_coord1 *x2,
+                            const Gcalc_coord1 *y2)
+{
+  Gcalc_coord2 p1, p2, sum;
+  p1.init();
+  p2.init();
+  sum.init();
+  exp->init();
+
+  gcalc_mul_coord(&p1, x1, y1);
+  gcalc_mul_coord(&p2, x2, y2);
+  gcalc_add_coord(&sum, &p1, &p2);
+  gcalc_mul_coord(exp, bb, &sum);
+}
+#endif /*TMP_BLOCK*/
+
+
+static int sp_isc_eq(const Gcalc_scan_iterator::point *sp,
+                     const Gcalc_heap::Intersection_info *isc)
+{
+
+  Gcalc_coord4 exp_a, exp_b;
+  Gcalc_coord1 xb1, yb1;
+  Gcalc_coord2 t_a, t_b;
+  Gcalc_coord2 t_sp_a, t_sp_b;
+#ifdef TMP_BLOCK
+  xa1a0.init();
+  ya1a0.init();
+
+  gcalc_sub_coord(&xa1a0, &isc->p1->ix, &sp->pi->ix);
+  gcalc_sub_coord(&ya1a0, &isc->p1->iy, &sp->pi->iy);
+  calc_isc_sp_exp(&exp_a, &t_b, &sp->pi->ix, &ya1a0, &sp->pi->iy, &xa1a0);
+  calc_isc_sp_exp(&exp_b, &t_a, &sp->pi->iy, &isc->p1->ix,
+                                &sp->pi->ix, &isc->p1->iy);
+  return gcalc_cmp_coord(&exp_a, &exp_b);
+#endif /*TMP_BLOCK*/
+  exp_a.init();
+  exp_b.init();
+  calc_t(&t_a, &t_b, &xb1, &yb1, isc);
+  calc_t(&t_sp_a, &t_sp_b, &xb1, &yb1, isc->p1, isc->p2, sp->pi, sp->next_pi);
+
+  gcalc_mul_coord(&exp_a, &t_a, &t_sp_b);
+  gcalc_mul_coord(&exp_b, &t_b, &t_sp_a);
+  int result= gcalc_cmp_coord(&exp_a, &exp_b);
+#ifdef GCALC_CHECK_WITH_FLOAT
+  long double int_x, int_y, sp_x;
+  isc->calc_xy_ld(&int_x, &int_y);
+  sp->calc_x(&sp_x, int_y, int_x);
+  if (result == 0)
+    DBUG_ASSERT(de_check1(sp->dy.get_double(), 0.0) ||
+                de_check(sp_x, int_x));
+#ifdef TMP_BLOCK
+  else
+    DBUG_ASSERT(!de_check1(sp_x, int_x));
+#endif /*TMP_BLOCK*/
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+  return result == 0;
 }
 
 
@@ -823,6 +1812,18 @@ int Gcalc_scan_iterator::handle_intersections()
   /* We need the next slice to be just equal */
   next_state->slice= new_slice(saved_state->slice);
   m_cur_intersection= m_intersections;
+#ifndef NO_TESTING
+  //if (isc_counter == 40)
+  {
+    printf("Sorted\n");
+    for (intersection *isc= m_intersections; isc; isc= isc->get_next())
+    {
+      long double ix, iy;
+      isc->ii->calc_xy_ld(&ix, &iy);
+      printf("%d\t%d\t%.20LG\t%.20LG\t%d\n", isc->thread_a, isc->thread_b, ix, iy, isc->n_row);
+    }
+  }
+#endif /*NO_TESTING*/
   return intersection_scan();
 }
 
@@ -832,7 +1833,6 @@ int Gcalc_scan_iterator::intersection_scan()
   point *sp0, *sp1;
   Gcalc_dyn_list::Item **hook;
   intersection *next_intersection= NULL;
-  int met_equal= 0;
 
   if (m_cur_intersection != m_intersections)
   {
@@ -846,31 +1846,72 @@ int Gcalc_scan_iterator::intersection_scan()
     if (arrange_event())
       return 1;
 
+#ifdef TMP_BLOCK
     if (!m_cur_intersection)
     {
       saved_state->event_position_hook=
         (Gcalc_dyn_list::Item **) &saved_state->slice;
-#ifdef TO_REMOVE
-      for (sp0= current_state->slice, sp1= saved_state->slice;
-           sp0;
-           sp0= sp0->get_next(), sp1= sp1->get_next())
+
+      for (sp1= saved_state->slice; sp1; sp1= sp1->get_next())
       {
-        sp0->next_link= sp1;
         if (sp1->get_next() == saved_state->event_position)
           saved_state->event_position_hook= &sp1->next;
       }
-#endif /*TO_REMOVE*/
-      for (sp1= saved_state->slice; sp1; sp1= sp1->get_next())
+      /* Swap saved <-> next */
       {
-        if (sp1->get_next() == saved_state->event_position)
-          saved_state->event_position_hook= &sp1->next;
+        slice_state *tmp= next_state;
+        next_state= saved_state;
+        saved_state= tmp;
       }
+      free_list(saved_state->slice);
+      saved_state->slice= NULL;
+
+      free_list(m_intersections);
+      m_intersections= NULL;
+      return 0;
+    }
+#endif /*TMP_BLOCK*/
+    if (!m_cur_intersection)
+    {
       /* Swap saved <-> next */
       {
         slice_state *tmp= next_state;
         next_state= saved_state;
         saved_state= tmp;
       }
+      Gcalc_dyn_list::Item **n_hook=
+        (Gcalc_dyn_list::Item **) &next_state->slice;
+
+      next_state->clear_event_position();
+      sp0= current_state->slice;
+      sp1= next_state->slice;
+
+      for (; sp0;
+           sp0= sp0->get_next(), n_hook= &sp1->next, sp1= sp1->get_next())
+      {
+        if (sp0->thread != sp1->thread)
+        {
+          point *fnd_s= sp1->get_next();
+          Gcalc_dyn_list::Item **fnd_hook= &sp1->next;
+          for (; fnd_s && fnd_s->thread != sp0->thread;
+               fnd_hook= &fnd_s->next, fnd_s= fnd_s->get_next());
+          DBUG_ASSERT(fnd_s && fnd_s == *fnd_hook);
+          /* Now swap items of the next_state->slice */
+          *n_hook= fnd_s;
+          *fnd_hook= fnd_s->next;
+          fnd_s->next= sp1;
+          sp1= fnd_s;
+        }
+        if (sp1->event)
+          mark_event_position1(sp1, n_hook);
+      }
+#ifndef DBUG_OFF
+      sp0= current_state->slice;
+      sp1= next_state->slice;
+      for (; sp0; sp0= sp0->get_next(), sp1= sp1->get_next())
+        DBUG_ASSERT(sp0->thread == sp1->thread);
+      DBUG_ASSERT(!sp1);
+#endif /*DBUG_OFF*/
       free_list(saved_state->slice);
       saved_state->slice= NULL;
 
@@ -880,12 +1921,12 @@ int Gcalc_scan_iterator::intersection_scan()
     }
   }
 
-  next_state->y= m_cur_intersection->y;
-
   sp0= current_state->slice;
   hook= (Gcalc_dyn_list::Item **) &next_state->slice;
   sp1= next_state->slice;
   next_state->clear_event_position();
+  next_state->intersection_scan= 1;
+  next_state->isc= m_cur_intersection->ii;
 
   for (; sp0;
        hook= &sp1->next, sp1= sp1->get_next(), sp0= sp0->get_next())
@@ -893,27 +1934,20 @@ int Gcalc_scan_iterator::intersection_scan()
     if (sp0->thread == m_cur_intersection->thread_a ||
         sp0->thread == m_cur_intersection->thread_b)
     {
-#ifdef REACTIVATE_THIS
       DBUG_ASSERT(sp0->thread != m_cur_intersection->thread_a ||
-        sp0->get_next()->thread == m_cur_intersection->thread_b);
-#endif /*REACTIVATE_THIS*/
+        sp0->get_next()->thread == m_cur_intersection->thread_b ||
+        sp_isc_eq(sp0->get_next(), m_cur_intersection->ii));
       sp1->copy_core(sp0);
-      sp1->x= m_cur_intersection->x;
       sp1->event= scev_intersection;
       mark_event_position1(sp1, hook);
     }
     else
     {
       sp1->copy_core(sp0);
-      sp1->x= sp1->horiz_dir ?
-                m_cur_intersection->x :
-                coord_to_float(sp1->pi->x) +
-                  (next_state->y-coord_to_float(sp1->pi->y)) * sp1->dx_dy;
-      if (coord_eq(sp1->x, m_cur_intersection->x))
+      if (sp_isc_eq(sp1, m_cur_intersection->ii))
       {
         sp1->event= scev_intersection;
         mark_event_position1(sp1, hook);
-        met_equal= 1;
       }
       else
         sp1->event= scev_none;
@@ -926,45 +1960,10 @@ int Gcalc_scan_iterator::intersection_scan()
     *hook= NULL;
   }
 
-  if (met_equal)
-  {
-    /* Remove superfluous intersections. */
-    /* Double operations can produce unexact result, so it's needed. */
-    for (sp0= next_state->event_position;
-        sp0 != *next_state->event_end_hook;
-        sp0= sp0->get_next())
-    {
-      for (sp1= sp0->get_next();
-          sp1 != *next_state->event_end_hook;
-          sp1= sp1->get_next())
-      {
-        intersection *isc= m_cur_intersection;
-        while (isc->get_next())
-        {
-          intersection *cur_isc= isc->get_next();
-          if ((cur_isc->thread_a == sp0->thread &&
-                cur_isc->thread_b == sp1->thread) ||
-              (cur_isc->thread_a == sp1->thread &&
-               cur_isc->thread_b == sp0->thread))
-          {
-            /* The superfluous intersection should be close to the current. */
-            DBUG_ASSERT(fabs(cur_isc->x-m_cur_intersection->x) +
-                        fabs(cur_isc->y-m_cur_intersection->y) <
-                         0.00000000001);
-            isc->next= isc->next->next;
-            free_item(cur_isc);
-          }
-          else
-            isc= isc->get_next();
-        }
-      }
-    }
-  }
-
+  /* Now check equal intersections */
   for (next_intersection= m_cur_intersection->get_next();
        next_intersection &&
-         coord_eq(next_intersection->x, m_cur_intersection->x) &&
-         coord_eq(next_intersection->y, m_cur_intersection->y);
+         intersections_eq(next_intersection->ii, m_cur_intersection->ii);
        next_intersection= next_intersection->get_next())
   {
     /* Handle equal intersections. We only need to set proper events */
@@ -990,5 +1989,58 @@ int Gcalc_scan_iterator::intersection_scan()
   return 0;
 }
 
+
+double Gcalc_scan_iterator::get_y() const
+{
+  if (current_state->intersection_scan)
+  {
+    double x, y;
+    current_state->isc->calc_xy(&x, &y);
+    return y;
+  }
+  else
+    return current_state->pi->y;
+}
+
+
+double Gcalc_scan_iterator::get_event_x() const
+{
+  if (current_state->intersection_scan)
+  {
+    double x, y;
+    current_state->isc->calc_xy(&x, &y);
+    return x;
+  }
+  else
+    return current_state->pi->x;
+}
+
+double Gcalc_scan_iterator::get_h() const
+{
+  double cur_y= get_y();
+  double next_y;
+  if (next_state->intersection_scan)
+  {
+    double x;
+    next_state->isc->calc_xy(&x, &next_y);
+  }
+  else
+    next_y= next_state->pi->y;
+  return next_y - cur_y;
+}
+
+
+double Gcalc_scan_iterator::get_sp_x(const point *sp) const
+{
+  double dy;
+  if (sp->event == scev_end | scev_two_ends | scev_point)
+    return sp->pi->x;
+  dy= sp->next_pi->y - sp->pi->y;
+  if (fabs(dy) < 1e-12)
+    return sp->pi->x;
+  return (sp->next_pi->x - sp->pi->x) * dy;
+}
+
+
 #endif /* HAVE_SPATIAL */
 
diff --git a/sql/gcalc_slicescan.h b/sql/gcalc_slicescan.h
index ebe2bcffe5c..d1c81ca4648 100644
--- a/sql/gcalc_slicescan.h
+++ b/sql/gcalc_slicescan.h
@@ -59,8 +59,11 @@ public:
   }
   inline void free_list(Item *list, Item **hook)
   {
-    *hook= m_free;
-    m_free= list;
+    if (*hook != list)
+    {
+      *hook= m_free;
+      m_free= list;
+    }
   }
 
   void free_list(Item *list)
@@ -91,6 +94,79 @@ protected:
   }
 };
 
+/* Internal Gcalc coordinates to provide the precise calculations */
+
+#define DIG_BASE     1000000000
+typedef int32 coord_digit_t;
+typedef long long coord2;
+
+#define C_SCALE 1e13
+#define COORD_BASE 2
+#ifndef DBUG_OFF
+//#define GCALC_CHECK_WITH_FLOAT
+#define NO_TESTING
+#else
+#define NO_TESTING
+#endif /*DBUG_OFF*/
+
+class Gcalc_internal_coord
+{
+public:
+  coord_digit_t *digits;
+  int sign;
+  int n_digits;
+  void set_zero();
+  int is_zero() const;
+#ifdef GCALC_CHECK_WITH_FLOAT
+  long double get_double() const;
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+};
+
+
+class Gcalc_coord1 : public Gcalc_internal_coord
+{
+  coord_digit_t c[COORD_BASE];
+public:
+  void init()
+  {
+    n_digits= COORD_BASE;
+    digits= c;
+  }
+  int set_double(double d);
+  void copy(const Gcalc_coord1 *from);
+};
+
+
+class Gcalc_coord2 : public Gcalc_internal_coord
+{
+  coord_digit_t c[COORD_BASE*2];
+public:
+  void init()
+  {
+    n_digits= COORD_BASE*2;
+    digits= c;
+  }
+};
+
+
+void gcalc_mul_coord(Gcalc_internal_coord *result,
+                     const Gcalc_internal_coord *a,
+                     const Gcalc_internal_coord *b);
+
+void gcalc_add_coord(Gcalc_internal_coord *result,
+                     const Gcalc_internal_coord *a,
+                     const Gcalc_internal_coord *b);
+
+void gcalc_sub_coord(Gcalc_internal_coord *result,
+                     const Gcalc_internal_coord *a,
+                     const Gcalc_internal_coord *b);
+
+int gcalc_cmp_coord(const Gcalc_internal_coord *a,
+                    const Gcalc_internal_coord *b);
+
+/* Internal coordinates declarations end. */
+
+
 typedef uint gcalc_shape_info;
 
 /*
@@ -114,27 +190,34 @@ public:
     Info *left;
     Info *right;
     double x,y;
+    Gcalc_coord1 ix, iy;
 
     inline bool is_bottom() const { return !left; }
     inline Info *get_next() { return (Info *)next; }
     inline const Info *get_next() const { return (const Info *)next; }
   };
+  class Intersection_info : public Gcalc_dyn_list::Item
+  {
+  public:
+    /* Line p1-p2 supposed to intersect line p3-p4 */
+    const Info *p1;
+    const Info *p2;
+    const Info *p3;
+    const Info *p4;
+    void calc_xy(double *x, double *y) const;
+#ifdef GCALC_CHECK_WITH_FLOAT
+    void calc_xy_ld(long double *x, long double *y) const;
+#endif /*GCALC_CHECK_WITH_FLOAT*/
+  };
 
   Gcalc_heap(size_t blk_size=8192) :
-    Gcalc_dyn_list(blk_size, sizeof(Info)), m_hook(&m_first), m_n_points(0) {}
-  Info *new_point_info(double x, double y, gcalc_shape_info shape)
-  {
-    Info *result= (Info *)new_item();
-    if (!result)
-      return NULL;
-    *m_hook= result;
-    m_hook= &result->next;
-    m_n_points++;
-    result->x= x;
-    result->y= y;
-    result->shape= shape;
-    return result;
-  }
+    Gcalc_dyn_list(blk_size, sizeof(Info)),
+    m_hook(&m_first), m_n_points(0),
+    m_intersection_hook((Gcalc_dyn_list::Item **) &m_first_intersection)
+  {}
+  Info *new_point_info(double x, double y, gcalc_shape_info shape);
+  Intersection_info *new_intersection(const Info *p1, const Info *p2,
+                                      const Info *p3, const Info *p4);
   void prepare_operation();
   inline bool ready() const { return m_hook == NULL; }
   Info *get_first() { return (Info *)m_first; }
@@ -145,6 +228,8 @@ private:
   Gcalc_dyn_list::Item *m_first;
   Gcalc_dyn_list::Item **m_hook;
   int m_n_points;
+  Intersection_info *m_first_intersection;
+  Gcalc_dyn_list::Item **m_intersection_hook;
 };
 
 
@@ -263,9 +348,13 @@ public:
   class point : public Gcalc_dyn_list::Item
   {
   public:
+#ifdef TMP_BLOCK
     double x;
     double dx_dy;
     int horiz_dir;
+#endif /*TMP_BLOCK*/
+    Gcalc_coord1 dx;
+    Gcalc_coord1 dy;
     Gcalc_heap::Info *pi;
     Gcalc_heap::Info *next_pi;
     sc_thread_id thread;
@@ -273,22 +362,32 @@ public:
     const point *intersection_link;
     Gcalc_scan_events event;
 #ifdef TO_REMOVE
-    const point *event_pair;
     point *next_link;
 #endif /*TO_REMOVE*/
 
     inline const point *c_get_next() const
       { return (const point *)next; }
-    inline bool is_bottom() const { return pi->is_bottom(); }
+    inline bool is_bottom() const { return !next_pi; }
     gcalc_shape_info get_shape() const { return pi->shape; }
     inline point *get_next() { return (point *)next; }
     inline const point *get_next() const { return (const point *)next; }
     /* copies all but 'next' 'x' and 'precursor' */
-    void copy_core(point *from);
+    void copy_core(const point *from);
+    void copy_all(const point *from);
     /* Compare the dx_dy parameters regarding the horiz_dir */
     /* returns -1 if less, 0 if equal, 1 if bigger          */
-    static int compare_dx_dy(int horiz_dir_a, double dx_dy_a,
-                             int horiz_dir_b, double dx_dy_b);
+#ifdef TMP_BLOCK
+    static int cmp_dx_dy(int horiz_dir_a, double dx_dy_a,
+                         int horiz_dir_b, double dx_dy_b);
+#endif /*TMP_BLOCK*/
+    static int cmp_dx_dy(const Gcalc_coord1 *dx_a,
+                         const Gcalc_coord1 *dy_a,
+                         const Gcalc_coord1 *dx_b,
+                         const Gcalc_coord1 *dy_b);
+    static int cmp_dx_dy(const Gcalc_heap::Info *p1,
+                         const Gcalc_heap::Info *p2,
+                         const Gcalc_heap::Info *p3,
+                         const Gcalc_heap::Info *p4);
     int cmp_dx_dy(const point *p) const;
     int simple_event() const
     {
@@ -298,6 +397,9 @@ public:
 #ifndef DBUG_OFF
     void dbug_print();
 #endif /*DBUG_OFF*/
+#ifdef GCALC_CHECK_WITH_FLOAT
+    void calc_x(long double *x, long double y, long double ix) const;
+#endif /*GCALC_CHECK_WITH_FLOAT*/
   };
 
   class intersection : public Gcalc_dyn_list::Item
@@ -306,8 +408,11 @@ public:
     int n_row;
     sc_thread_id thread_a;
     sc_thread_id thread_b;
+#ifdef TMP_BLOCK
     double x;
     double y;
+#endif /*TMP_BLOCK*/
+    const Gcalc_heap::Intersection_info *ii;
     inline intersection *get_next() { return (intersection *)next; }
   };
 
@@ -318,7 +423,15 @@ public:
     point *event_position;
     Gcalc_dyn_list::Item **event_position_hook;
     Gcalc_dyn_list::Item **event_end_hook;
+    int intersection_scan;
+    union
+    {
+      const Gcalc_heap::Info *pi;
+      const Gcalc_heap::Intersection_info *isc;
+    };
+#ifdef TMP_BLOCK
     double y;
+#endif /*TMP_BLOCK*/
     slice_state() : slice(NULL) {}
     void clear_event_position()
     {
@@ -350,10 +463,24 @@ public:
     { return (point *) *current_state->event_end_hook; }
   inline const point *get_b_slice() const { return current_state->slice; }
   inline const point *get_t_slice() const { return next_state->slice; }
-  inline double get_h() const { return current_state->y - next_state->y; }
-  inline double get_y() const { return current_state->y; }
+  double get_h() const;
+  double get_y() const;
+  double get_event_x() const;
+  double get_sp_x(const point *sp) const;
+  int intersection_step() const { return current_state->intersection_scan; }
+  const Gcalc_heap::Info *get_cur_pi() const
+  {
+    DBUG_ASSERT(!intersection_step());
+    return current_state->pi;
+  }
+  const Gcalc_heap::Intersection_info *get_cur_ii() const
+  {
+    DBUG_ASSERT(intersection_step());
+    return current_state->isc;
+  }
 
 private:
+  Gcalc_heap *m_heap;
   Gcalc_heap::Info *m_cur_pi;
   slice_state state0, state1, state_s;
   slice_state *current_state;
@@ -382,7 +509,10 @@ private:
   }
   point *new_slice_point()
   {
-    return (point *)new_item();
+    point *new_point= (point *)new_item();
+    new_point->dx.init();
+    new_point->dy.init();
+    return new_point;
   }
   point *new_slice(point *example);
   int arrange_event();
@@ -450,7 +580,6 @@ public:
   inline const Gcalc_scan_iterator::point *point() const { return sp; }
   inline const Gcalc_heap::Info *get_pi() const { return sp->pi; }
   inline gcalc_shape_info get_shape() const { return sp->get_shape(); }
-  inline double get_x() const { return sp->x; }
   inline void restart(const Gcalc_scan_iterator *scan_i)
   { sp= scan_i->get_b_slice(); }
 };
diff --git a/sql/gcalc_tools.cc b/sql/gcalc_tools.cc
index baff6278444..90c39f08d0b 100644
--- a/sql/gcalc_tools.cc
+++ b/sql/gcalc_tools.cc
@@ -347,6 +347,10 @@ int Gcalc_result_receiver::add_point(double x, double y)
   buffer.q_append(prev_y);
   prev_x= x;
   prev_y= y;
+#ifndef NO_TESTING
+  if (n_points == 53)
+    printf("xxx\n");
+#endif /*NO_TESTING*/
   return 0;
 }
 
@@ -488,6 +492,9 @@ int Gcalc_result_receiver::move_hole(uint32 dest_position, uint32 source_positio
 
 Gcalc_operation_reducer::Gcalc_operation_reducer(size_t blk_size) :
   Gcalc_dyn_list(blk_size, sizeof(res_point)),
+#ifndef DBUG_OFF
+  n_res_points(0),
+#endif /*DBUG_OFF*/
   m_res_hook((Gcalc_dyn_list::Item **)&m_result),
   m_first_active_thread(NULL)
 {}
@@ -514,9 +521,73 @@ Gcalc_operation_reducer(Gcalc_function *fn, modes mode, size_t blk_size) :
 }
 
 
-inline int Gcalc_operation_reducer::continue_range(active_thread *t,
-						const Gcalc_heap::Info *p,
-                                                int horiz_dir, double dx_dy)
+void Gcalc_operation_reducer::res_point::set(const Gcalc_scan_iterator *si)
+{
+  if ((intersection_point= si->intersection_step()))
+    ii= si->get_cur_ii();
+  else
+    pi= si->get_cur_pi();
+}
+
+#ifndef NO_TESTING
+void call_checkpoint(int d)
+{
+  printf("%d\n", d);
+}
+#endif /*NO_TESTING*/
+
+Gcalc_operation_reducer::res_point *
+  Gcalc_operation_reducer::add_res_point(Gcalc_function::shape_type type)
+{
+  res_point *result= (res_point *)new_item();
+  *m_res_hook= result;
+  result->prev_hook= m_res_hook;
+  m_res_hook= &result->next;
+  result->type= type;
+#ifndef DBUG_OFF
+  result->point_n= n_res_points++;
+#endif /*DBUG_OFF*/
+#ifndef NO_TESTING
+  if (result->point_n == 74)
+    call_checkpoint(74);
+#endif /*NO_TESTING*/
+  return result;
+}
+
+int Gcalc_operation_reducer::add_line(int incoming, active_thread *t,
+    const Gcalc_scan_iterator::point *p)
+{
+  line *l= new_line();
+  if (!l)
+    return 1;
+  l->incoming= incoming;
+  l->t= t;
+  l->p= p;
+  *m_lines_hook= l;
+  m_lines_hook= &l->next;
+  return 0;
+}
+
+
+int Gcalc_operation_reducer::add_poly_border(int incoming,
+    active_thread *t, int prev_state, const Gcalc_scan_iterator::point *p)
+{
+  poly_border *b= new_poly_border();
+  if (!b)
+    return 1;
+  b->incoming= incoming;
+  b->t= t;
+  b->prev_state= prev_state;
+  b->p= p;
+  *m_poly_borders_hook= b;
+  m_poly_borders_hook= &b->next;
+  return 0;
+}
+
+
+int Gcalc_operation_reducer::continue_range(active_thread *t,
+                                            const Gcalc_heap::Info *p,
+                                            const Gcalc_heap::Info *p_next)
 {
   res_point *rp= add_res_point(t->rp->type);
   if (!rp)
@@ -527,15 +598,14 @@ inline int Gcalc_operation_reducer::continue_range(active_thread *t,
   rp->intersection_point= false;
   rp->pi= p;
   t->rp= rp;
-  t->horiz_dir= horiz_dir;
-  t->dx_dy= dx_dy;
+  t->p1= p;
+  t->p2= p_next;
   return 0;
 }
 
 
 inline int Gcalc_operation_reducer::continue_i_range(active_thread *t,
-						  double x, double y,
-                                                  int horiz_dir, double dx_dy)
+			            const Gcalc_heap::Intersection_info *ii)
 {
   res_point *rp= add_res_point(t->rp->type);
   if (!rp)
@@ -544,11 +614,8 @@ inline int Gcalc_operation_reducer::continue_i_range(active_thread *t,
   rp->down= t->rp;
   t->rp->up= rp;
   rp->intersection_point= true;
-  rp->x= x;
-  rp->y= y;
+  rp->ii= ii;
   t->rp= rp;
-  t->horiz_dir= horiz_dir;
-  t->dx_dy= dx_dy;
   return 0;
 }
 
@@ -573,6 +640,9 @@ int Gcalc_operation_reducer::end_couple(active_thread *t0, active_thread *t1,
 }
 
 
+#ifndef NO_TESTING
+int ca_counter= 0;
+#endif /*NO_TESTING*/
 int Gcalc_operation_reducer::count_slice(Gcalc_scan_iterator *si)
 {
   Gcalc_point_iterator pi(si);
@@ -587,8 +657,16 @@ int Gcalc_operation_reducer::count_slice(Gcalc_scan_iterator *si)
   active_thread *bottom_threads= NULL;
   active_thread *eq_thread, *point_thread;;
 
+#ifndef NO_TESTING
+  if (ca_counter == 11522)
+    call_checkpoint(89);
+#endif /*NO_TESTING*/
   m_fn->clear_state();
   /* Walk to the event, remembering what is needed. */
+#ifndef NO_TESTING
+  if (si->get_event_position() == pi.point())
+    printf("yyy\n");
+#endif /*NO_TESTING*/
   for (; pi.point() != si->get_event_position();
        ++pi, cur_t_hook= (active_thread **) &(*cur_t_hook)->next)
   {
@@ -612,13 +690,13 @@ int Gcalc_operation_reducer::count_slice(Gcalc_scan_iterator *si)
       case scev_point:
       {
         if (cur_t->enabled() &&
-            continue_range(cur_t, events->pi, events->horiz_dir, events->dx_dy))
+            continue_range(cur_t, events->pi, events->next_pi))
           return 1;
         break;
       }
       case scev_end:
       {
-        if (cur_t->enabled() && end_line(cur_t, events->pi, si))
+        if (cur_t->enabled() && end_line(cur_t, si))
           return 1;
         *cur_t_hook= cur_t->get_next();
         free_item(cur_t);
@@ -635,8 +713,7 @@ int Gcalc_operation_reducer::count_slice(Gcalc_scan_iterator *si)
         else if (cur_t->enabled() || cur_t->get_next()->enabled())
         {
           /* Rare case when edges of a polygon coincide */
-          if (end_line(cur_t->enabled() ? cur_t : cur_t->get_next(),
-                       events->pi, si))
+          if (end_line(cur_t->enabled() ? cur_t : cur_t->get_next(), si))
             return 1;
         }
         *cur_t_hook= cur_t->get_next()->get_next();
@@ -647,6 +724,9 @@ int Gcalc_operation_reducer::count_slice(Gcalc_scan_iterator *si)
       default:
         DBUG_ASSERT(0);
     }
+#ifndef NO_TESTING
+    goto testing;
+#endif /*NO_TESTING*/
     return 0;
   }
 
@@ -773,7 +853,7 @@ int Gcalc_operation_reducer::count_slice(Gcalc_scan_iterator *si)
     for (events= si->get_events(); events; events= events->get_next())
       m_fn->set_on_state(events->get_shape());
 
-    return m_fn->count() ? add_single_point(event_point, si) : 0;
+    return m_fn->count() ? add_single_point(si) : 0;
   }
 
   if (m_poly_borders)
@@ -783,6 +863,10 @@ int Gcalc_operation_reducer::count_slice(Gcalc_scan_iterator *si)
     {
       poly_border *pb1, *pb2;
       pb1= m_poly_borders;
+#ifndef NO_TESTING
+      if (!m_poly_borders->next)
+        call_checkpoint(3);
+#endif /*NO_TESTING*/
       DBUG_ASSERT(m_poly_borders->next);
 
       pb2= get_pair_border(pb1);
@@ -790,8 +874,7 @@ int Gcalc_operation_reducer::count_slice(Gcalc_scan_iterator *si)
       m_poly_borders= pb1->get_next();
       if (connect_threads(pb1->incoming, pb2->incoming,
                           pb1->t, pb2->t, pb1->p, pb2->p,
-                          prev_range, event_point, si,
-                          Gcalc_function::shape_polygon))
+                          prev_range, si, Gcalc_function::shape_polygon))
         return 1;
 
       free_item(pb1);
@@ -809,8 +892,8 @@ int Gcalc_operation_reducer::count_slice(Gcalc_scan_iterator *si)
     {
       if (connect_threads(m_lines->incoming, m_lines->get_next()->incoming,
                           m_lines->t, m_lines->get_next()->t,
-                          m_lines->p, m_lines->get_next()->p, NULL,
-                          event_point, si, Gcalc_function::shape_line))
+                          m_lines->p, m_lines->get_next()->p,
+                          NULL, si, Gcalc_function::shape_line))
         return 1;
     }
     else
@@ -819,11 +902,11 @@ int Gcalc_operation_reducer::count_slice(Gcalc_scan_iterator *si)
       {
         if (cur_line->incoming)
         {
-          if (end_line(cur_line->t, event_point, si))
+          if (end_line(cur_line->t, si))
             return 1;
         }
         else
-          start_line(cur_line->t, cur_line->p, event_point, si);
+          start_line(cur_line->t, cur_line->p, si);
       }
     }
     free_list(m_lines);
@@ -834,28 +917,56 @@ int Gcalc_operation_reducer::count_slice(Gcalc_scan_iterator *si)
   if (bottom_threads)
     free_list(bottom_threads);
 
+#ifndef NO_TESTING
+testing:
+  {
+    Gcalc_point_iterator x_pi(si);
+    active_thread **x_cur_t_hook= &m_first_active_thread;
+    int x_prev_state= 0;
+    m_fn->save_states();
+    m_fn->clear_state();
+    if (ca_counter == /*11552*/90)
+      call_checkpoint(10);
+    for (; x_pi.point(); ++x_pi)
+    {
+      active_thread *cur_t= *x_cur_t_hook;
+      if (cur_t->enabled() &&
+          cur_t->rp->type == Gcalc_function::shape_polygon)
+        x_prev_state^= 1;
+      int ppb= m_fn->count();
+      if (m_fn->get_shape_kind(x_pi.get_shape()) == Gcalc_function::shape_polygon)
+        m_fn->invert_state(x_pi.get_shape());
+      int ppa= m_fn->count();
+      if (ppa != x_prev_state)
+      {
+        if (x_pi.point()->cmp_dx_dy(x_pi.point()->get_next()) != 0)
+          call_checkpoint(21);
+      }
+      if (cur_t->enabled())
+      {
+        if (m_fn->get_shape_kind(x_pi.get_shape()) == Gcalc_function::shape_polygon)
+          if (ppa == ppb)
+            call_checkpoint(22);
+        else
+          if (ppa != 0 && ppb != 0)
+            call_checkpoint(23);
+      }
+      x_cur_t_hook= (active_thread **) &(*x_cur_t_hook)->next;
+    }
+    m_fn->restore_states();
+  }
+#endif /*NO_TESTING*/
   return 0;
 }
 
 
-int Gcalc_operation_reducer::add_single_point(const Gcalc_heap::Info *p,
-                                              const Gcalc_scan_iterator *si)
+int Gcalc_operation_reducer::add_single_point(const Gcalc_scan_iterator *si)
 {
   res_point *rp= add_res_point(Gcalc_function::shape_point);
   if (!rp)
     return 1;
   rp->glue= rp->up= rp->down= NULL;
-  if (p)
-  {
-    rp->intersection_point= false;
-    rp->pi= p;
-  }
-  else
-  {
-    rp->intersection_point= true;
-    rp->y= si->get_y();
-    rp->x= si->get_events()->x;
-  }
+  rp->set(si);
   return 0;
 }
 
@@ -912,7 +1023,7 @@ int Gcalc_operation_reducer::connect_threads(
     int incoming_a, int incoming_b,
     active_thread *ta, active_thread *tb,
     const Gcalc_scan_iterator::point *pa, const Gcalc_scan_iterator::point *pb,
-    active_thread *prev_range, const Gcalc_heap::Info *ev_p,
+    active_thread *prev_range,
     const Gcalc_scan_iterator *si, Gcalc_function::shape_type s_t)
 {
   if (incoming_a && incoming_b)
@@ -929,18 +1040,8 @@ int Gcalc_operation_reducer::connect_threads(
     rpa->up= rpb->up= NULL;
     ta->rp->up= rpa;
     tb->rp->up= rpb;
-    if (ev_p)
-    {
-      rpa->intersection_point= rpb->intersection_point= false;
-      rpa->pi= rpb->pi= ev_p;
-    }
-    else
-    {
-      rpa->intersection_point= rpb->intersection_point= true;
-      rpa->x= rpb->x= si->get_events()->x;
-      rpa->y= rpb->y= si->get_y();
-    }
-
+    rpa->set(si);
+    rpb->set(si);
     ta->rp= tb->rp= NULL;
     return 0;
   }
@@ -953,35 +1054,30 @@ int Gcalc_operation_reducer::connect_threads(
       return 1;
     rp0->glue= rp1;
     rp1->glue= rp0;
-    if (ev_p)
-    {
-      rp0->intersection_point= rp1->intersection_point= false;
-      rp0->pi= rp1->pi= ev_p;
-    }
-    else
-    {
-      rp0->intersection_point= rp1->intersection_point= true;
-      rp0->x= rp1->x= si->get_events()->x;
-      rp0->y= rp1->y= si->get_y();
-    }
+    rp0->set(si);
+    rp1->set(si);
     rp0->down= rp1->down= NULL;
     ta->rp= rp0;
     tb->rp= rp1;
-    ta->horiz_dir= pa->horiz_dir;
-    ta->dx_dy= pa->dx_dy;
+    ta->p1= pa->pi;
+    ta->p2= pa->next_pi;
 
-    tb->horiz_dir= pb->horiz_dir;
-    tb->dx_dy= pb->dx_dy;
+    tb->p1= pb->pi;
+    tb->p2= pb->next_pi;
 
     if (prev_range)
     {
       rp0->outer_poly= prev_range->thread_start;
       tb->thread_start= prev_range->thread_start;
+      /* Chack if needed */
+      ta->thread_start= prev_range->thread_start;
     }
     else
     {
       rp0->outer_poly= 0;
       ta->thread_start= rp0;
+      /* Chack if needed */
+      tb->thread_start= rp0;
     }
     return 0;
   }
@@ -991,20 +1087,18 @@ int Gcalc_operation_reducer::connect_threads(
   tb->rp= ta->rp;
   tb->thread_start= ta->thread_start;
   if (Gcalc_scan_iterator::point::
-      compare_dx_dy(ta->horiz_dir, ta->dx_dy,
-                    pb->horiz_dir, pb->dx_dy) != 0)
+      cmp_dx_dy(ta->p1, ta->p2, pb->pi, pb->next_pi) != 0)
   {
-    if (ev_p ? continue_range(tb, ev_p, pb->horiz_dir, pb->dx_dy):
-               continue_i_range(tb,
-                                si->get_events()->x, si->get_y(),
-                                pb->horiz_dir, pb->dx_dy))
+    if (si->intersection_step() ?
+          continue_i_range(tb, si->get_cur_ii()) :
+          continue_range(tb, si->get_cur_pi(), pb->next_pi))
+#ifdef TMP_BLOCK
+          continue_range(tb, si->get_cur_pi())
+#endif /*TMP_BLOCK*/
       return 1;
   }
-  else
-  {
-    tb->horiz_dir= pb->horiz_dir;
-    tb->dx_dy= pb->dx_dy;
-  }
+  tb->p1= pb->pi;
+  tb->p2= pb->next_pi;
 
   return 0;
 }
@@ -1012,33 +1106,21 @@ int Gcalc_operation_reducer::connect_threads(
 
 int Gcalc_operation_reducer::start_line(active_thread *t,
                                         const Gcalc_scan_iterator::point *p,
-                                        const Gcalc_heap::Info *ev_p,
                                         const Gcalc_scan_iterator *si)
 {
   res_point *rp= add_res_point(Gcalc_function::shape_line);
   if (!rp)
     return 1;
   rp->glue= rp->down= NULL;
-  if (ev_p)
-  {
-    rp->intersection_point= false;
-    rp->pi= ev_p;
-  }
-  else
-  {
-    rp->intersection_point= true;
-    rp->x= si->get_events()->x;
-    rp->y= si->get_y();
-  }
+  rp->set(si);
   t->rp= rp;
-  t->horiz_dir= p->horiz_dir;
-  t->dx_dy= p->dx_dy;
+  t->p1= p->pi;
+  t->p2= p->next_pi;
   return 0;
 }
 
 
 int Gcalc_operation_reducer::end_line(active_thread *t,
-                                      const Gcalc_heap::Info *ev_p,
                                       const Gcalc_scan_iterator *si)
 {
   DBUG_ASSERT(t->rp->type == Gcalc_function::shape_line);
@@ -1047,17 +1129,7 @@ int Gcalc_operation_reducer::end_line(active_thread *t,
     return 1;
   rp->glue= rp->up= NULL;
   rp->down= t->rp;
-  if (ev_p)
-  {
-    rp->intersection_point= false;
-    rp->pi= ev_p;
-  }
-  else
-  {
-    rp->intersection_point= true;
-    rp->x= si->get_events()->x;
-    rp->y= si->get_y();
-  }
+  rp->set(si);
   t->rp->up= rp;
   t->rp= NULL;
 
@@ -1071,6 +1143,11 @@ int Gcalc_operation_reducer::count_all(Gcalc_heap *hp)
   si.init(hp);
   while (si.more_points())
   {
+#ifndef NO_TESTING
+    printf("Point %d\n", ++ca_counter);
+    if (ca_counter == 12)
+      call_checkpoint(10);
+#endif /*NO_TESTING*/
     if (si.step())
       return 1;
     if (count_slice(&si))
@@ -1094,8 +1171,9 @@ inline int Gcalc_operation_reducer::get_single_result(res_point *res,
 {
   if (res->intersection_point)
   {
-    if (storage->single_point(float_to_coord(res->x),
-			      float_to_coord(res->y)))
+    double x, y;
+    res->ii->calc_xy(&x, &y);
+    if (storage->single_point(x,y))
       return 1;
   }
   else
@@ -1105,6 +1183,9 @@ inline int Gcalc_operation_reducer::get_single_result(res_point *res,
   return 0;
 }
 
+#ifndef NO_TESTING
+int pc_counter= 0;
+#endif /*NO_TESTING*/
 
 int Gcalc_operation_reducer::get_result_thread(res_point *cur,
                                                Gcalc_result_receiver *storage,
@@ -1116,12 +1197,16 @@ int Gcalc_operation_reducer::get_result_thread(res_point *cur,
   double x, y;
   while (cur)
   {
+#ifndef NO_TESTING
+    ++pc_counter;
+    if (pc_counter == 79)
+      call_checkpoint(79);
+#endif /*NO_TESTING*/
     if (!glue_step)
     {
       if (cur->intersection_point)
       {
-        x= float_to_coord(cur->x);
-        y= float_to_coord(cur->y);
+        cur->ii->calc_xy(&x, &y);
       }
       else
       {
diff --git a/sql/gcalc_tools.h b/sql/gcalc_tools.h
index da7be1d9fa7..39704dfeb56 100644
--- a/sql/gcalc_tools.h
+++ b/sql/gcalc_tools.h
@@ -206,26 +206,37 @@ public:
   int get_result(Gcalc_result_receiver *storage);
   void reset();
 
+#ifndef DBUG_OFF
+  int n_res_points;
+#endif /*DBUG_OFF*/
   class res_point : public Gcalc_dyn_list::Item
   {
   public:
-    bool intersection_point;
-    double x,y;
-    res_point *up;
-    res_point *down;
-    res_point *glue;
-    Gcalc_function::shape_type type;
+    int intersection_point;
     union
     {
       const Gcalc_heap::Info *pi;
+      const Gcalc_heap::Intersection_info *ii;
       res_point *first_poly_node;
     };
+#ifdef TMP_BLOCK
     union
     {
+#endif /*TMP_BLOCK*/
       res_point *outer_poly;
       uint32 poly_position;
+#ifdef TMP_BLOCK
     };
+#endif /*TMP_BLOCK*/
+    res_point *up;
+    res_point *down;
+    res_point *glue;
+    Gcalc_function::shape_type type;
     Gcalc_dyn_list::Item **prev_hook;
+#ifndef DBUG_OFF
+    int point_n;
+#endif /*DBUG_OFF*/
+    void set(const Gcalc_scan_iterator *si);
     res_point *get_next() { return (res_point *)next; }
   };
 
@@ -233,9 +244,9 @@ public:
   {
   public:
     res_point *rp;
-    int horiz_dir;
-    double dx_dy;
     res_point *thread_start;
+
+    const Gcalc_heap::Info *p1, *p2;
     res_point *enabled() { return rp; }
     active_thread *get_next() { return (active_thread *)next; }
   };
@@ -273,33 +284,9 @@ public:
   line *new_line() { return (line *) new_item(); }
   poly_border *new_poly_border() { return (poly_border *) new_item(); }
   int add_line(int incoming, active_thread *t,
-               const Gcalc_scan_iterator::point *p)
-  {
-    line *l= new_line();
-    if (!l)
-      return 1;
-    l->incoming= incoming;
-    l->t= t;
-    l->p= p;
-    *m_lines_hook= l;
-    m_lines_hook= &l->next;
-    return 0;
-  }
-
+               const Gcalc_scan_iterator::point *p);
   int add_poly_border(int incoming, active_thread *t, int prev_state,
-                      const Gcalc_scan_iterator::point *p)
-  {
-    poly_border *b= new_poly_border();
-    if (!b)
-      return 1;
-    b->incoming= incoming;
-    b->t= t;
-    b->prev_state= prev_state;
-    b->p= p;
-    *m_poly_borders_hook= b;
-    m_poly_borders_hook= &b->next;
-    return 0;
-  }
+                      const Gcalc_scan_iterator::point *p);
 
 protected:
   Gcalc_function *m_fn;
@@ -310,43 +297,29 @@ protected:
   res_point *result_heap;
   active_thread *m_first_active_thread;
 
-  res_point *add_res_point(Gcalc_function::shape_type type)
-  {
-    res_point *result= (res_point *)new_item();
-    *m_res_hook= result;
-    result->prev_hook= m_res_hook;
-    m_res_hook= &result->next;
-    result->type= type;
-    return result;
-  }
-
+  res_point *add_res_point(Gcalc_function::shape_type type);
   active_thread *new_active_thread() { return (active_thread *)new_item(); }
 
   poly_instance *new_poly() { return (poly_instance *) new_item(); }
 
 private:
   int start_line(active_thread *t, const Gcalc_scan_iterator::point *p,
-                 const Gcalc_heap::Info *ev_p, const Gcalc_scan_iterator *si);
-  int end_line(active_thread *t, const Gcalc_heap::Info *ev_p,
-               const Gcalc_scan_iterator *si);
+                 const Gcalc_scan_iterator *si);
+  int end_line(active_thread *t, const Gcalc_scan_iterator *si);
   int connect_threads(int incoming_a, int incoming_b,
                       active_thread *ta, active_thread *tb,
                       const Gcalc_scan_iterator::point *pa,
                       const Gcalc_scan_iterator::point *pb,
                       active_thread *prev_range,
-                      const Gcalc_heap::Info *ev_p,
                       const Gcalc_scan_iterator *si,
                       Gcalc_function::shape_type s_t);
-  int add_single_point(const Gcalc_heap::Info *p,
-                       const Gcalc_scan_iterator *si);
+  int add_single_point(const Gcalc_scan_iterator *si);
   poly_border *get_pair_border(poly_border *b1);
   int continue_range(active_thread *t, const Gcalc_heap::Info *p,
-                     int horiz_dir, double dx_dy);
-  int continue_i_range(active_thread *t, double x, double y,
-                       int horiz_dir, double dx_dy);
+                     const Gcalc_heap::Info *p_next);
+  int continue_i_range(active_thread *t,
+                       const Gcalc_heap::Intersection_info *ii);
   int end_couple(active_thread *t0, active_thread *t1, const Gcalc_heap::Info *p);
-  int add_single_point(const Gcalc_heap::Info *p);
-
   int get_single_result(res_point *res, Gcalc_result_receiver *storage);
   int get_result_thread(res_point *cur, Gcalc_result_receiver *storage,
 			int move_upward, res_point *first_poly_node);
diff --git a/sql/item_geofunc.cc b/sql/item_geofunc.cc
index 631b63812b5..2c3facb49c8 100644
--- a/sql/item_geofunc.cc
+++ b/sql/item_geofunc.cc
@@ -867,7 +867,8 @@ int Item_func_spatial_rel::func_touches()
       if (cur_func)
       {
         area= scan_it.get_h() *
-              ((ti.rb()->x - ti.lb()->x) + (ti.rt()->x - ti.lt()->x));
+              ((scan_it.get_sp_x(ti.rb()) - scan_it.get_sp_x(ti.lb())) +
+               (scan_it.get_sp_x(ti.rt()) - scan_it.get_sp_x(ti.lt())));
         if (area > GIS_ZERO)
         {
           result= 0;
diff --git a/sql/spatial.cc b/sql/spatial.cc
index 67e36ccb12b..0e535d11056 100644
--- a/sql/spatial.cc
+++ b/sql/spatial.cc
@@ -2230,6 +2230,8 @@ bool Gis_geometry_collection::get_mbr(MBR *mbr, const char **end) const
     return 1;
   n_objects= uint4korr(data);
   data+= 4;
+  if (n_objects == 0)
+    return 1;
 
   while (n_objects--)
   {