class GLWidget : public QGLWidget
{
Q_OBJECT
...
}

#ifndef GLWIDGET_H
#define GLWIDGET_H

#include <QtOpenGL>

class GLWidget : public QGLWidget
{
public:
    GLWidget(QWidget *parent = 0);

protected:
    void initializeGL();
    void resizeGL(int nWidth, int nHeight);
    void paintGL();

};

#endif // WIDGET_H

#include "glwidget.h"

GLWidget::GLWidget(QWidget *parent)
    : QGLWidget(parent)
{
}


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

void GLWidget::resizeGL(int nWidth, int nHeight){


}

void GLWidget::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT);
}

glBegin(GL_POINTS);
glEnd();