+static void grow_spline_points (spline* s);
+static void mid_point (double x0, double y0, double x1, double y1,
+ double *mx, double *my);
+static int can_approx_with_line (double x0, double y0, double x2,
+ double y2, double x3, double y3);
+static void add_line (spline* s, double x0, double y0, double x1, double y1);
+static void add_bezier_arc (spline* s,
+ double x0, double y0, double x1, double y1,
+ double x2, double y2, double x3, double y3);
+static void third_point (double x0, double y0, double x1, double y1,
+ double *tx, double *ty);
+static void calc_section (spline* s, double cminus1x, double cminus1y,
+ double cx, double cy, double cplus1x, double cplus1y,
+ double cplus2x, double cplus2y);