Вызов функции С++ из Qml, Qt

#ifndef CIRCLE1_H
#define CIRCLE1_H
#include <QObject>
#include <QPainter>
#include <QtQuick>
 
class circle1 : public QObject
{
    Q_OBJECT
    Q_PROPERTY(int radius READ radius WRITE setRadius NOTIFY RadiusChanged)
    Q_PROPERTY(int wavelength READ wavelength WRITE setWavelength NOTIFY WavelengthChanged)
    Q_PROPERTY(int distance_to_the_screen READ distance_to_the_screen WRITE setDistance_to_the_screen NOTIFY Distance_to_the_screenChanged)
    Q_PROPERTY(int distance_to_the_screen2 READ distance_to_the_screen2 WRITE setDistance_to_the_screen2 NOTIFY Distance_to_the_screen2Changed)
private:
    int _wavelength;
    int _radius;
    int _distance_to_the_screen;
    int _distance_to_the_screen2;
public:
    explicit circle1(QObject *parent = 0);
//    //Запуск класса
//    void start(int &a,int &b,int &c,int &d);
    //Вывод изображения
    Q_INVOKABLE void draw(QPainter *painter);
    //Get-функции
    int radius();
    int wavelength();
    int distance_to_the_screen();
    int distance_to_the_screen2();
    //Set-функции
    void setWavelength(int &a);
    void setRadius(int &a);
    void setDistance_to_the_screen(int &a);
    void setDistance_to_the_screen2(int &a);
signals:
    //Сигналы для Set-функций
    void RadiusChanged();
    void WavelengthChanged();
    void Distance_to_the_screenChanged();
    void Distance_to_the_screen2Changed();
    void PaintChanged();
public slots:
};
#endif // CIRCLE1_H

void circle1::draw(QPainter *painter)
{
    painter->save();
 
    double m;
    QPen pen = QPen(Qt::NoPen);
    QBrush black_brush = QBrush(Qt::black);
    QBrush red_brush = QBrush(Qt::red);
    painter->setPen(pen);
    m=100000*(_radius*_radius)/_wavelength;
    m=m*(1/_distance_to_the_screen+1/(_distance_to_the_screen2-_distance_to_the_screen));
    int k=int(m);
    if(k!=0)
    {
        m=120/k;
        for(int i=1;i<=k;i++)
        {
            if(i%2==1)
            {
                painter->setBrush(red_brush);
                painter->drawEllipse(2+m*(i-1),2+m*(i-1),210-m*(i-1)*2,210-m*(i-1)*2);
            }
            else
            {
                painter->setBrush(black_brush);
                painter->drawEllipse(2+m*(i-1),2+m*(i-1),210-m*(i-1)*2,210-m*(i-1)*2);
            }
        }
    }
    else
    {
        int i;
        painter->setBrush(red_brush);
        painter->drawEllipse(2+m*(i-1),2+m*(i-1),210-m*(i-1)*2,210-m*(i-1)*2);
    }
    painter->restore();
    emit PaintChanged();
}

...
        Rectangle{
            id: for_start;
            x: 600
            anchors.top: rectangle1.bottom
            anchors.topMargin: 11
            anchors.right: parent.right
            anchors.rightMargin: 424
            Button{
                id:start
                text:"Start"
                onClicked: {
                    Circle1.radius = slider2.value
                    Circle1.wavelength = slider1.value
                    Circle1.distance_to_the_screen = slider3.value
                    Circle1.distance_to_the_screen2 = slider4.value
                    Circle1.draw(rectangle2)
                }
            }
        }
...