Рисование точек по координатам

Ring::Ring( QWidget *parent ) :
    QWidget( parent )
{
    dot_1 =1;
    dot_2 =1;
    dot_3 =1;
 
    // Устанавливаем кодеки
    QTextCodec::setCodecForCStrings( QTextCodec::codecForName( "UTF-8" ) );
    QTextCodec::setCodecForTr( QTextCodec::codecForName( "UTF-8" ) );
 
    resize(300, 300);
}
 
void Ring::paintEvent(QPaintEvent *){
 
 int side = qMin(width(), height());
 
 QPainter painter(this);
 painter.setRenderHint(QPainter::Antialiasing);
 painter.translate(width() / 2, height() / 2);
 painter.scale(side / 300.0, side / 300.0);
 
 painter.setPen(Qt::NoPen);
 painter.save();
 
 painter.restore();
 
 painter.setPen(QPen(Qt::black,1,Qt::SolidLine));
 painter.drawEllipse(-50,-50,100,100);
 
 painter.setPen(QPen(Qt::black,1,Qt::SolidLine));
 painter.drawEllipse(-100,-100,200,200);
 
 painter.setPen(QPen(Qt::black,1,Qt::SolidLine));
 painter.drawEllipse(-150,-150,300,300);
 
 painter.drawLine(0,150,0,-150);
 painter.drawLine(-150,0,150,0);
 
 painter.setPen(QPen(Qt::black,2,Qt::SolidLine));
 painter.drawPoint(dot_1,dot_2);
 
 
}

#include <QWidget>
 
class Ring : public QWidget
{
    Q_OBJECT
public:
    Ring( QWidget *parent = 0 );
 
    void setDot(int x, int y, int signal )
    {
        dot_1 = x;
        dot_2 = y;
        dot_3 = signal;
 
        //update();
    }
 
private:
 
int dot_1, dot_2, dot_3;
 
signals:
 
protected:
     void paintEvent( QPaintEvent *event );
    
public slots:
    
};