cairo_status_t (*set_source_rgba) (void *cr, double red, double green, double blue, double alpha);
cairo_status_t (*curve_to) (void *cr, double x1, double y1, double x2, double y2, double x3, double y3);
cairo_status_t (*rel_curve_to) (void *cr, double dx1, double dy1, double dx2, double dy2, double dx3, double dy3);
cairo_status_t (*rel_arc_to) (void *cr, double dx1, double dy1, double dx2, double dy2, double radius);
cairo_status_t (*arc) (void *cr, double xc, double yc, double radius, double angle1, double angle2, cairo_bool_t forward);