2 files changed, 70 insertions, 0 deletions

diff --git a/generic/Geo.c b/generic/Geo.c
index 16cee3e..cf07dc3 100644
--- a/generic/Geo.c
+++ b/generic/Geo.c
@@ -498,6 +498,9 @@ ShiftLine(ZnPoint	*p1,
   else {
     dy_neg = False;
   }
+  if ((dy == 0) && (dx == 0)) {
+    return;
+  }
   if (dy <= dx) {
     dy = ((dist * shift_table[(dy*128)/dx]) + 64) / 128;
     if (!dx_neg) {
@@ -1072,6 +1075,58 @@ PointInAngle(int	start_angle,
 	  ((angle_extent < 0) && ((angle_diff - 360) >= angle_extent)));
 }
 
+/*
+ * PointPolarToCartesian --
+ *	Convert a point in polar coordinates (rho, theta)
+ *	in a reference system described by angle heading
+ *	(angles running clockwise) to a point in cartesian
+ *	coordinates (delta_x, delta_y).
+ *
+ */
+void
+PointPolarToCartesian(ZnReal	heading,
+		      int	rho,
+		      int	theta,
+		      int	*delta_x,
+		      int	*delta_y)
+{
+  double	to_angle;
+
+  /* Compute angle in trigonometric system */
+  to_angle = DegreesToRadian(theta) + heading - M_PI_2;
+  /*  to_angle = heading - DegreesToRadian(theta);*/
+  /* Compute cartesian coordinates */
+  *delta_x = (int) (rho * cos(to_angle));
+  *delta_y = (int) (rho * sin(to_angle));
+}
+
+/*
+ * Return a vector angle given its projections
+ */
+ZnReal
+ProjectionToAngle(ZnDim	dx,
+		  ZnDim	dy)
+{
+  if (dx == 0) {
+    if (dy < 0) {
+      return -M_PI_2;
+    }
+    else if (dy > 0) {
+      return M_PI_2;
+    }
+    else {
+      return 0.0;
+    }
+  }
+  else if (dx < 0) {
+    return atan((double) dy / (double) dx) - M_PI;
+  }
+  else {
+    return atan((double) dy / (double) dx);
+  }
+  return 0.0;
+}
+
 
 /*
  * Tell if an horizontal line intersect an axis aligned
diff --git a/generic/Geo.h b/generic/Geo.h
index 8a173b1..8403819 100644
--- a/generic/Geo.h
+++ b/generic/Geo.h
@@ -64,6 +64,10 @@
 
 #define DegreesToRadian(angle) \
   (M_PI * (double) (angle) / 180.0)
+#define RadianToDegrees(angle) \
+  (fmod((angle) * 180.0 / M_PI, 360.0))
+#define RadianToDegrees360(angle) \
+  (fmod(RadianToDegrees(angle)+360.0,360.0))
 
 #define REAL_TO_INT(double) \
   (((int) ((double) + (((double) > 0) ? 0.5 : -0.5))))
@@ -174,6 +178,17 @@ PointInAngle(int	start_angle,
 	     int	angle_extent,
 	     ZnPoint	*p);
 
+void
+PointPolarToCartesian(ZnReal	heading,
+		      int	rho,
+		      int	theta,
+		      int	*delta_x,
+		      int	*delta_y);
+
+ZnReal
+ProjectionToAngle(ZnDim	dx,
+		  ZnDim	dy);
+
 double
 RectangleToPointDist(ZnBBox	*bbox,
 		     ZnPoint	*p);