What element of Qlgwidget I'd pass to a class only to draw ?

[mcosta]

Yes it can be a solution.
In my case, I'd prefer the against proccess.
And, in your opinion, what can be faster ?
my_object.draw
draw(my_object).
(or it is the same ?)
Thanks

IMO both have the same speed.
the main difference is that

• my_object.draw: each object knows how draw itself;
  
• draw(my_object): the object that execute this has to know my_object data to draw it.

in OO style I prefer the first one.