Hi Pilou, 
 
> The funny of SPiro shown on the escape video 
> is how is managed the control! 
> On an external rectangle curve :) 
 
You mean for controlling the width of the shape?  I think that's a feature of Inkscape for applying a pattern to follow a curve, that part does not have any specific relation to Spiro, Spiro is used there for the centerline curve. 
 
I hope to be able to have something similar to that pattern-applying stuff with some of the deformation tools that I want to work on for v3. 
 
  - Michael 
 |