QWidget::paintEngine: Should no longer be called

Staslend

I saw topics of people who has the same error. I understand that all using of QPainter must happened in the paintEvent. I done this, but problem still exist.
This is the code of function:

void GraphicsView::painEvent(QPaintEvent *event)
{
    QPainter  painter(viewport());

    painter.setPen(Qt::blue);
    painter.setFont(QFont("Arial", 30));
    painter.drawText(rect(), Qt::AlignCenter, "Qt");
}

In short, I create class that inherited from QGraphicsView. I rewrite some functions, but I do not think that problem in them. There is a full code of my program:

GraphicsView.h

#include <QGraphicsView>
#include <QEvent>
#include <QPainter>
#include <QPaintEvent>

class GraphicsView : public QGraphicsView
{
    Q_OBJECT

    using  QObject :: event;
    using  QGraphicsView :: paintEvent;

public:
    GraphicsView();
    virtual ~GraphicsView();


    bool eventFilter(QObject *object, QEvent *event);
    virtual void painEvent(QPaintEvent * event);
};

GraphicsView.cpp

#include "graphicsview.h"

GraphicsView::GraphicsView():QGraphicsView ()
{
    this->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    this->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
}


GraphicsView::~GraphicsView()
{

}


// I changed there the event when wheel is moving
bool GraphicsView::eventFilter(QObject *object, QEvent *event)
{
    if(event->type() == QEvent::Wheel)
    {
        return  true;
    }
    return true;
}

void GraphicsView::painEvent(QPaintEvent *event)
{
    QPainter  painter(viewport());

    painter.setPen(Qt::blue);
    painter.setFont(QFont("Arial", 30));
    painter.drawText(rect(), Qt::AlignCenter, "Qt");
}

main.cpp

#include "graphicsview.h"
#include <QApplication>
#include <QGraphicsScene>
#include <QGraphicsView>

#include <QMouseEvent>
#include <QUrl>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);


    QRect r;
    r.setX(0);
    r.setY(0);
    r.setWidth(1920);
    r.setHeight(1080);

    QGraphicsScene  scene(r);

    GraphicsView  view;
    view.setScene(&scene);

    
    view.update();
    view.showFullScreen();

    return a.exec();
}

This is the errors, may be it will help:

QWidget::paintEngine: Should no longer be called
QPainter::begin: Paint device returned engine == 0, type: 1
QPainter::setPen: Painter not active
QPainter::setFont: Painter not active

Can somebody help me? Thanks in advance.

Christian Ehrlicher

I don't see any debug / warning output on Linux with qt5.12/13

JonB

@Staslend

I understand that all using of QPainter must happened in the paintEvent

void GraphicsView::painEvent(QPaintEvent *event)

Look at your typing/spelling!? (Or is that not relevant here? I assume you're trying to override?)

SGaist

Hi,

When re-implementing a function like that, use the override keyword. It will trigger a warning during build if no matching method can be found in one of the base class.

Staslend

@SGaist thank you for help, I have no errors not with QPainter. But I can't use override word with paintEvent, I have this error: 'paintEvent' marked 'override' but does not override any member function. With eventFilter it working.

Christian Ehrlicher

@JonB said in QWidget::paintEngine: Should no longer be called:

painEvent

The override keyword works, when you've the function name right.

JonB

@Staslend
http://doc.qt.io/qt-5/qgraphicsview.html#paintEvent

void QGraphicsView::paintEvent(QPaintEvent *event)    [override virtual protected]

JonB

@Christian-Ehrlicher said in QWidget::paintEngine: Should no longer be called:

@JonB said in QWidget::paintEngine: Should no longer be called:

painEvent

The override keyword works, when you've the function name right.

But that's what I've been saying to the OP...! I quoted what he has written.... He is now saying he cannot use paintEvent spelt correctly with override, so I guess he needs to show us what actually tried?

Staslend

Thanks for everyone! I am sorry for this mistake. The QtCreator write painEvent using Italic so I thought that the name of function was written right. Everything is working now.

Pablo J. Rogina

@Staslend if your issue is solved, please don't forget to mark your post as such! Thanks.