Inheritance and QpaintEvent

[jacek]

But I don t want to create new ones ! Qt does ...

Qt does only what you tell it to do.

Indeed, the problem is in constructor. If you create a widget without a parent, it will be created as a standalone window. So your constructor should be implemented like this:

Son::Son( QWidget *parent ) 
   : Mother( parent )
{
   ...
}

Son::Son( QWidget *parent ) 
   : Mother( parent )
{
   ...
}

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And the Mother class must pass this parent to QWidget's constructor.

I never know if I need to specify *parent or *parent=0

That "= 0" part only indicates a default value for the parameter.