[OpenGL] Drawing simple polygon crashes application

[Doles]

Hi there,
I`m new OpenGL programmer but I have some experience from programming with WinAPI+OpenGL or plain GLUT. Now I decided to move into Qt4 + OpenGL but I have plenty of troubles during getting first steps in this topic I was looking at example source code for OpenGL programs but there are too sophisicated (I don`t want to use any sliders or rotate something yet). I tried to write as simple app as it can be using source code from here:
http://doc.trolltech.com/4.4/opengl-hellogl.html
My programm compile (wrote in Qt Creator under Windows XP) without any errors but it crash and I just see Window`s error dialog with sending report about bug (i hope you know what i mean). I don`t know how to debuge OpenGL apps, so there is my whole source code:
File: window.h

#ifndef WINDOW_H
#define WINDOW_H
 
#include <QtGui/QWidget>
#include <QHBoxLayout>
#include "ui_window.h"
#include "glwidget.h"
 
 
class Window : public QWidget
{
    Q_OBJECT
 
public:
    Window(QWidget *parent = 0, Qt::WFlags flags = 0);
    ~Window();
 
private:
    Ui::WindowClass ui;
    GLWidget* glWidget;
};
 
#endif // WINDOW_H

#ifndef WINDOW_H
#define WINDOW_H

#include <QtGui/QWidget>
#include <QHBoxLayout>
#include "ui_window.h"
#include "glwidget.h"


class Window : public QWidget
{
    Q_OBJECT

public:
    Window(QWidget *parent = 0, Qt::WFlags flags = 0);
    ~Window();

private:
    Ui::WindowClass ui;
    GLWidget* glWidget;
};

#endif // WINDOW_H

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File: window.cpp

#include "window.h"
 
Window::Window(QWidget *parent, Qt::WFlags flags)
    : QWidget(parent, flags)
{
    ui.setupUi(this);
    QHBoxLayout *mainLayout = new QHBoxLayout();
    mainLayout->addWidget(glWidget);
    setLayout(mainLayout);
 
    setWindowTitle(tr("Hello OpenGL"));
}
 
Window::~Window()
{
 
}

#include "window.h"

Window::Window(QWidget *parent, Qt::WFlags flags)
    : QWidget(parent, flags)
{
    ui.setupUi(this);
    QHBoxLayout *mainLayout = new QHBoxLayout();
    mainLayout->addWidget(glWidget);
    setLayout(mainLayout);

    setWindowTitle(tr("Hello OpenGL"));
}

Window::~Window()
{

}

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and most important files, I guess...
File: glwidget.h

#ifndef GLWIDGET_H
#define GLWIDGET_H
#include <QGLWidget>
#include <QtOpenGL>
 
class GLWidget: public QGLWidget
{
    Q_OBJECT
  public:
        GLWidget(QWidget *parent = 0);
        ~GLWidget();
 
 
  protected:
        void    initializeGL();
        void    paintGL();
        void    resizeGL(int width, int height);
};
#endif // GLWIDGET_H

#ifndef GLWIDGET_H
#define GLWIDGET_H
#include <QGLWidget>
#include <QtOpenGL>

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


  protected:
        void    initializeGL();
        void    paintGL();
        void    resizeGL(int width, int height);
};
#endif // GLWIDGET_H

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File: glwidget.cpp

#include "glwidget.h"
 
GLWidget::GLWidget(QWidget* parent): QGLWidget(parent)
{
}
 
GLWidget::~GLWidget()
{
}
 
void GLWidget::initializeGL()
{
    qglClearColor(QColor(255, 0, 0, 127));
    glEnable(GL_DEPTH_TEST);
}
 
void GLWidget::resizeGL(int width, int height)
{
    int side = qMin(width, height);
    glViewport((width - side) / 2, (height - side)/2, side, side);
    glMatrixMode(GL_PROJECTION);
 
    glLoadIdentity();
    glMatrixMode(GL_MODELVIEW);
}
 
void GLWidget::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    glBegin(GL_POLYGON);
        //glColor3f(1.0f, 0.4f, 0.5f);
        glVertex3f(-1.0f , 4.0f, 0.0f);
        glVertex3f(2.0f, -1.0f, 0.0f);
        glVertex3f(4.0f, -4.0f, -1.0f);
        //glColor3f(0.4f, 0.4f, 0.4f);
        glVertex3f(1.3f, -2.3f, -2.0f);
        glVertex3f(0.0f, 4.0f, -2.0f);
    glEnd();
}

#include "glwidget.h"

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

GLWidget::~GLWidget()
{
}

void GLWidget::initializeGL()
{
    qglClearColor(QColor(255, 0, 0, 127));
    glEnable(GL_DEPTH_TEST);
}

void GLWidget::resizeGL(int width, int height)
{
    int side = qMin(width, height);
    glViewport((width - side) / 2, (height - side)/2, side, side);
    glMatrixMode(GL_PROJECTION);

    glLoadIdentity();
    glMatrixMode(GL_MODELVIEW);
}

void GLWidget::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    glBegin(GL_POLYGON);
        //glColor3f(1.0f, 0.4f, 0.5f);
        glVertex3f(-1.0f , 4.0f, 0.0f);
        glVertex3f(2.0f, -1.0f, 0.0f);
        glVertex3f(4.0f, -4.0f, -1.0f);
        //glColor3f(0.4f, 0.4f, 0.4f);
        glVertex3f(1.3f, -2.3f, -2.0f);
        glVertex3f(0.0f, 4.0f, -2.0f);
    glEnd();
}

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Main.cpp is of course very simple:

#include <QtGui/QApplication>
#include "window.h"
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    Window *window = new Window();
    window->show();
    return app.exec();
}

#include <QtGui/QApplication>
#include "window.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    Window *window = new Window();
    window->show();
    return app.exec();
}

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Thank you for attention, I`m waiting for any help

[stephanepoirier]

Hi,

I am trying to use glut.h along in a qt application under windows. My application won't build, I get 4 unresolved references: __glutInitWithExit, __glutCreateWindowWithExit, __glutCreateMenuWithExit and the only glut function I am explicitely calling in my code glutSolidCube.

Anyone know the trick to use glut.h functionality along with Qtcreator in Windows?

Stephane

[ComaWhite]

stephanepoirier please don't hijack threads

[spud]

It seems glWidget is an uninitialized variable.
You need the line

glWidget = new GlWidget;

glWidget = new GlWidget;

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somewhere in your code.