Qt5 opengl widget givng error openglfunctions line 656

gtx0908

hey guys
using windows 10 and qt creator qt 5
im trying to out a opengl 3 widget on qt I have looked at some youtube tutorials and such but it is giving me this error when using qt5 with openglwidget using a widget on the ui

main.cpp

#include "mainwindow.h"
#include <QApplication>
#include <thread>
#include <algorithm>
#include <vector>

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

    return a.exec();
}

glwidget.cpp

#include "glwidget.h"

glwidget::glwidget(QWidget *parent):QOpenGLWidget {parent}
{

}

void glwidget::initializeGL()
{
    glClearColor(0,0,0,1);
    initializeOpenGLFunctions();
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_LIGHT0);
    glEnable(GL_LIGHTING);
    glEnable(GL_COLOR_MATERIAL);

}

void glwidget::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);





}

void glwidget::resizeGL(int w, int h)
{






}

void glwidget::qColorToRGB(const QColor &C, float &r, float &g, float &b) const
{





}

float glwidget::normalize_0_1(float val,float min,float max) const
{



    return (val - min) / (max - min);
}

glwidget.h

#ifndef GLWIDGET_H
#define GLWIDGET_H

#include <QGLWidget>
#include <QOpenGLWidget>
#include <QOpenGLFunctions>
#include <QProcess>

class glwidget : public QOpenGLWidget,public QOpenGLFunctions
{
  //  Q_OBJECT
public:
    explicit glwidget(QWidget *parent = nullptr);
protected:
    void initializeGL();
    void paintGL() override;
    void resizeGL(int w,int h) override;
private:
    void qColorToRGB(const QColor &C, float &r,float &g,float &b) const;
    float normalize_0_1(float val,float min,float max) const;
};


#endif // GLWIDGET_H

Mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

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;
}

i have promoted

screenshot of error

![alt text](image url)

Chris Kawa

void glwidget::initializeGL()
{
    glClearColor(0,0,0,1);       // <--- HERE
    initializeOpenGLFunctions();
    ...

You are using a GL function before a pointer to it was resolved. Don't call any glXXX functions before initializeOpenGLFunctions(). Just switch those two lines and you should be good to go.

SGaist

Hi,

The code in your image does not seem to match what you posted.

It's missing the initializeOpenGLFunctions(); call in your initializeGL override.

gtx0908

ah theres a myglwidget that i tried using from a second youtube video tutorial but i went back to glwidget.h/cpp which was the original tutorial the myglwidget.h/cpp file in the image can be ignored

Chris Kawa

void glwidget::initializeGL()
{
    glClearColor(0,0,0,1);       // <--- HERE
    initializeOpenGLFunctions();
    ...

You are using a GL function before a pointer to it was resolved. Don't call any glXXX functions before initializeOpenGLFunctions(). Just switch those two lines and you should be good to go.

gtx0908

@Chris-Kawa ah ok that worked and learned something new thanks