According council go Gronde Jasper I decided not to do before an extension in Python. I created a branch in Launchpad called B-Spline.

As I want to make it work with the tool Beizer I have a problem. This is the result I want to see while drawing tool like calligraphic strokes.

Subtraction accurately understand this if, for example, stroke is the width or has a color similar to background. From what I see important that the line where the stroke will go, once completed, should continue as a curve or BSPLINE spiro and not currently a curve Beizer.

For as designed the efect that are updated live to close the path not know if this is possible or not. Does anyone know?