Qt Creator Qt 5.7 OpenGL Functions not found

Question

I am using Qt creator ide and Qt 5.7 framework for my program. And i have a widget in my form. This widget controlled by opengl. To be more specific, i want to draw shapes with opengl on that widget. But i can't use glGenVertexArrays, glBindVertexArray. I got these errors:

'glGenVertexArrays': identifier not found
'glBindVertexArray': identifier not found

GLWidget.h:

#ifndef GLWIDGET_H
#define GLWIDGET_H

#include <QOpenGLWidget>
#include <QOpenGLFunctions>

class GLWidget : public QOpenGLWidget, protected QOpenGLFunctions
{
    Q_OBJECT
public:
    explicit GLWidget(QWidget *parent);

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

#endif // GLWIDGET_H

GLWidget.cpp

#include "glwidget.h"

GLWidget::GLWidget(QWidget *parent) : QOpenGLWidget(parent)
{

}

void GLWidget::initializeGL() {
    initializeOpenGLFunctions();
    glClearColor(0, 0, 0, 1);
}

void GLWidget::paintGL() {
    GLuint VertextArrayID;
    glGenVertexArrays(1, &VertextArrayID);
    glBindVertexArray(VertextArrayID);
}

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

}

.pro file

QT       += core gui opengl

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = QtOpenGLTest
TEMPLATE = app

LIBS += -lOpenGL32
SOURCES += main.cpp\
        mainwindow.cpp \
    glwidget.cpp

HEADERS  += mainwindow.h \
    glwidget.h

FORMS    += mainwindow.ui

Answer 1

Vertex arrays-related functions are not in QOpenGLFunctions , as that class aims at the common subset of OpenGL 2.1 (+FBO) and OpenGL ES 2.

They're available in other ways:

• QOpenGLExtraFunctions (aiming at GL 3.x + extensions / ES 3.x)
• QOpenGLVertexArrayObject (wrapper class for the functionality)
• QOpenGLExtension_ARB_vertex_array_object (which just wrapper the corresponding extension. This won't work on ES 2, where you got the OES_ extension, or on Apple devices where you got the APPLE_ extension).