Inheritance and QpaintEvent

[djoul]

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().

Ok, so here what I don t understand :
In my Current class, where I do all the drawing in the Current:aintEvent.
I create a Son(which is not a Widget), and I call Son->draw().
I want this function for example to draw an ellipse on the Current (which is the widget).
So in Son::draw I just do update(), which calls the Son:aintEvent which will draw the Ellipse.
Then, in my Son:aintEvent what do I do ???? that s the point that I do not understand !!! I can t do QPainter painter(this)
son.cpp(106): error C2664: 'QPainter::QPainter(QPaintDevice *)'*: impossible de convertir le paramètre 1 de Son*const ' en 'QPaintDevice *'

That s why I was doing all the thing with passing the Widget to the Son so he knows where to draw !!!!!

[jacek]

Ok, so here what I don t understand :
In my Current class, where I do all the drawing in the Current::paintEvent.
I create a Son(which is not a Widget), and I call Son->draw().

So in this case you should have something like this:

class Son
{
    public:
        Son() { ... }
        void draw( QWidget *widget ) const
        {
            QPainter painter( widget ); // <--
            painter.drawEllipse( ... );
            ...
        }
    ...
};
 
void Current::paintEvent( QPaintEvent * )
{
   ...
   Son s;
   s.draw( this );
   ...
}

class Son
{
    public:
        Son() { ... }
        void draw( QWidget *widget ) const
        {
            QPainter painter( widget ); // <--
            painter.drawEllipse( ... );
            ...
        }
    ...
};

void Current::paintEvent( QPaintEvent * )
{
   ...
   Son s;
   s.draw( this );
   ...
}

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[djoul]

Jacek, A statue of you should be built for the help you gave me, it WORKS.
THANK YOU,
YYYYYYYYYYYHHHHHAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA