[cairo] How to move a path

[fred]

Hi everybody!

I have a lot of shape on a cairo surface, and I would like to move these
shape with the mouse. I don't know the shape, because I have to suppose
that they have been drawn by a user. 
Currently, each time that a user starts a new shape, I create a new
ImageSurface, and save the Path of the draw. 
After, I recover the ImageSurface, and add it to the main context.

When a user want to move a shape, I don't know what could I do in order
to manage it.

I don't think that I use the good method, and I really need help!

thanks
Fred