My QOpenGLWidget is being created, but it doesn't work

[mrjbom]

Hello.

I have a simple form in which I add an OpenGLWidget, and then set my "MyOpenGLWidget" class to the Promoted Class,

it is successfully created, but is not displayed.
Its constructor is called, but the initializeGL, resizeGL, and paintGL functions are not called.

Project file: HERE

Here is all my code:
main.cpp

#include "mainwindow.h"

#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

ui_mainwindow.h

class Ui_MainWindow
{
public:
    QWidget *centralwidget;
    MyOpenGLWidget *openGLWidget;

    void setupUi(QMainWindow *MainWindow)
    {
        if (MainWindow->objectName().isEmpty())
            MainWindow->setObjectName(QString::fromUtf8("MainWindow"));
        MainWindow->resize(420, 300);
        centralwidget = new QWidget(MainWindow);
        centralwidget->setObjectName(QString::fromUtf8("centralwidget"));
        openGLWidget = new MyOpenGLWidget(centralwidget);
        openGLWidget->setObjectName(QString::fromUtf8("openGLWidget"));
        openGLWidget->setGeometry(QRect(60, 50, 300, 200));
        MainWindow->setCentralWidget(centralwidget);

        retranslateUi(MainWindow);

        QMetaObject::connectSlotsByName(MainWindow);
    } // setupUi

    void retranslateUi(QMainWindow *MainWindow)
    {
        MainWindow->setWindowTitle(QCoreApplication::translate("MainWindow", "MainWindow", nullptr));
    } // retranslateUi

};

namespace Ui {
    class MainWindow: public Ui_MainWindow {};
} // namespace Ui

QT_END_NAMESPACE

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

myopenglwidget.cpp

#include "myopenglwidget.h"
#include "globalvars.h"
#include "gl/GLU.h"

MyOpenGLWidget::MyOpenGLWidget(QWidget* parent)
{
    qInfo() << "MyOpenGLWidget called";
}

MyOpenGLWidget::~MyOpenGLWidget()
{
    qInfo() << "~MyOpenGLWidget called";
}

void MyOpenGLWidget::initializeGL()
{
    qInfo() << "initializeGL called!";
    initializeOpenGLFunctions();
    globalOpenGLContext = this->context();
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(-this->width() / 2, this->width() / 2, -this->height() / 2, this->height() / 2);
    glViewport(0, 0, this->width(), this->height());

}

void MyOpenGLWidget::resizeGL(int w, int h)
{
    qInfo() << "resizeGL called!";
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(-w / 2, w / 2, -h / 2, h / 2);
    glViewport(0, 0, w, h);
}

void MyOpenGLWidget::paintGL()
{
    qInfo() << "paintGL called!";
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glColor3f(1, 1, 1);
    glPushMatrix();
    glBegin(GL_POLYGON);
    glVertex3f(-100, 100, 0);
    glVertex3f(100, 100, 0);
    glVertex3f(100, -100, 0);
    glVertex3f(-100, -100, 0);
    glEnd();
    glPopMatrix();

    update();
}

myopenglwidget.h

#ifndef MYOPENGLWIDGET_H
#define MYOPENGLWIDGET_H

#include <QDebug>
#include <QOpenGLWidget>
#include <qopenglfunctions_3_3_core.h>
#include <gl/GLU.h>

class MyOpenGLWidget : public QOpenGLWidget, protected QOpenGLFunctions_3_3_Core
{
    Q_OBJECT
public:
    MyOpenGLWidget(QWidget *parent = nullptr);
    ~MyOpenGLWidget();

protected:
    void initializeGL();
    void resizeGL(int w, int h);
    void paintGL();
};

#endif // MYOPENGLWIDGET_H

[jsulm]

@mrjbom said in My QOpenGLWidget is being created, but it doesn't work:

void initializeGL();
void resizeGL(int w, int h);
void paintGL();

You should change this to

void initializeGL() override;
void resizeGL(int w, int h) override;
void paintGL() override;

to make sure you're really overriding.

[mrjbom]

@jsulm, I added these changes to myopenglwidget.h, it didn't help.

[SGaist]

Hi,

You should put it in a layout inside the centralwidget.

[mrjbom]

@SGaist @jsulm
Hi. The problem was that in myopenglwidget.cpp I didn't pass "parent" to the QOpenGLWidget() constructor.
Thanks.