cairo:curve-to (cr x1 y1 x2 y2 x3 y3)

cr -- a cairo:context-t instance
x1 -- a number for the x coordinate of the first control point
y1 -- a number for the y coordinate of the first control point
x2 -- a number for the x coordinate of the second control point
y2 -- a number for the y coordinate of the second control point
x3 -- a number for the x coordinate of the third control point
y3 -- a number for the y coordinate of the third control point

Adds a cubic Bezier spline to the path from the current point to position (x3,y3) in user-space coordinates, using (x1,y1) and (x2,y2) as the control points. After this call the current point will be (x3,y3).

If there is no current point before the call to the cairo:curve-to function this function will behave as if preceded by a call to:

(cairo:move-to cr x1 y1)  

The numbers for the arguments are coerced to double floats before being passed to the foreign C function.