painter:curveto(x1,y1,x2,y2,x3,y3)
Expression painter:curveto(x1,y1,x2,y2,x3,y3)
appends a section of a cubic Bezier curve to the current path.
The curve starts on the current point and ends in point (x3,y3)
using (x1,y1) and (x2,y2) as the Bezier control points.
The endpoint (x3,y3) then becomes the new current point.
The behavior of this function is undefined when the current point is not set
See also: PostScript operator curveto.