Qt Opengl

glwidget.h

#ifndef GLWIDGET_H
#define GLWIDGET_H

#include <QGLWidget>

class GLWidget : public QGLWidget
{
public:
       GLWidget();

       ~GLWidget();
       void initializeGL();
       void paintGL();
       void resizeGL(int w, int h);
};

#endif // GLWIDGET_H

glwidget.cpp

#include "glwidget.h"

GLWidget::GLWidget()
               : QGLWidget()
{}

GLWidget::~GLWidget()
{}

void GLWidget::initializeGL()
{
   qglClearColor( Qt::black );
}

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

   glLoadIdentity();
   qglColor( Qt::white );

   glBegin(GL_TRIANGLES);
   glVertex3f( 0.0f, 1.0f, 0.0f);
   glVertex3f(-1.0f,-1.0f, 0.0f);
   glVertex3f( 1.0f,-1.0f, 0.0f);
   glEnd();
}

void GLWidget::resizeGL(int w, int h)
{
   h = h < 1 ? 1 : h;
   glViewport( 0, 0, (GLint)w, (GLint)h );
}

main.cpp

#include <QApplication>
#include "glwidget.h"

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

   GLWidget w;
   w.resize(800, 600);
   w.show();

   return app.exec();
}

gl.pro

QT += opengl
TARGET = gl
CONFIG += console
CONFIG -= app_bundle
TEMPLATE = app
SOURCES += main.cpp \
    glwidget.cpp
HEADERS += glwidget.h