Quote Originally Posted by djoul
Ok, in my vision Son is an Object that is not a widget because it's not a "window"
If it's just "an object" then you shouldn't derive it from QWidget. Everything what inherits QWidget is a widget.

In Qt4 you can draw on widgets only in their paintEvent() method. This means that you have to invoke Son::draw() from your widget's paintEvent().

Quote Originally Posted by djoul
That s really weird [...] has become black instead of red !!! and I never gave such dimensions for the widget
No it's not, you just see the Son widget.