Draw a line with QPainter using QGraphicsView subclass

Question: I can't make the GraphicsView's paintEvent be called or in other words I don't know how to make QPainter work altogether. I'm using qtcreator's designer to place a QGraphicsView into the main window. I sub-classed QGraphicsView (class Draw) overriding the paintEvent and hold an instance of this subclass (Draw draw) in the main window (I wanted to move the complicated drawing elsewhere) I created a new QGraphicsScene and assign it to both QGraphicsView's (ui->graphicsView and draw) so when I draw inside the Draw it would visibly take effect in the ui->graphicsview as well (I hope). I'm sure when I draw using the new scene object, I get a visible result (however, I don't want to use the scene object for drawing but the QPainter. The reason why is for another question so I hope it's not essential) Therefore I'm trying to subclass the QGraphicsView and override the paintEvent so I get the QPainter p(this) easily. When an event occurs I call MyRepaint() in Window.cpp where I'm trying to invoke paintEvent() on my Draw object - but it's not working. Main window 'Window.cpp': Window::Window(QWidget* parent) : QMainWindow(parent), ui(new Ui::Window), draw(*this) //my own QGraphicsView instance (see class below) { ui->setupUi(this); //assigning a new scene to draw and to window's graphicsView this->scene = new QGraphicsScene(this); this->draw.setScene(scene); this->ui->graphicsView->setScene(scene); } void Window::MyRepaint() { qInfo() << "Repaint - start" << this->draw.scene(); this->draw.scene()->update(this->draw.sceneRect()); this->draw.repaint(); this->draw.viewport()->update(); /*only the following line made the paintEvent executed eventually but without a visible result and with an error in the output*/ this->draw.paintEvent(NULL); qInfo() << "Repaint - end"; } subclassing QGraphicsView, file: Draw.h: class Window; class Draw : public QGraphicsView{ private: Window& parent; public: Draw(Window &parent); void paintEvent(QPaintEvent*e) override; }; Draw.cpp void Draw::paintEvent(QPaintEvent *e) { qInfo() << "trying to draw"; QPainter p(this); p.setPen(QPen(Qt::black, 12, Qt::DashDotLine, Qt::RoundCap)); p.drawLine(0, 0, 200, 200); } Output: Repaint - start QGraphicsScene(0x15c7eca8) trying to draw QWidget::paintEngine: Should no longer be called QPainter::begin: Paint device returned engine == 0, type: 1 QPainter::setPen: Painter not active QPainter::viewport: Painter not active QPainter::end: Painter not active, aborted Repaint - end Maybe I've chosen a completely wrong approach.