I'm fairly new to Qt. I'm trying to make a custom VJ application. For my video-output I want to use OpenGL, which I control by another mainwindow. The problem is, It just renders black. I copypasted what the NeHe tutorial says for drawing a simple white triangle and rectangle, but it's still black. I don't get what's wrong with it. Is there anything I missed?
this is my glscreen.h
Qt Code: 
  1. #ifndef GLSCREEN_H
  2. #define GLSCREEN_H
  3.  
  4. #include <QMainWindow>
  5. #include <QGLWidget>
  6.  
  7. class VJOutput : public QGLWidget{
  8.     Q_OBJECT
  9. public:
  10.     VJOutput();
  11. protected:
  12.     void initializeGL();
  13.     void paintGL();
  14.     void resizeGL(int w, int h);
  15. public slots:
  16.     void Herteken();
  17.  
  18. };
  19.  
  20.  
  21. #endif // GLSCREEN_H
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here's the glscreen.cpp code

Qt Code: 
  1. #include "glscreen.h"
  2. #include "ui_glscreen.h"
  3. #include <iostream>
  4. #include <QTimer>
  5. #include <math.h>
  6.  
  7. void VJOutput::initializeGL(){
  8.     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);		// Clear The Screen And The Depth Buffer
  9.     glLoadIdentity();						// Reset The View
  10. }
  11. VJOutput::VJOutput(){
  12.     initializeGL();
  13.     QTimer *RedrawTimer = new QTimer(this);
  14.     connect(RedrawTimer,SIGNAL(timeout()),this,SLOT(Herteken()));
  15.     RedrawTimer->start(20);
  16.  
  17. }
  18. void VJOutput::resizeGL(int w, int h){
  19.  
  20. }
  21.  
  22. void VJOutput::paintGL(){
  23.     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  24.     glLoadIdentity();
  25.  
  26.     glTranslatef(-1.5f,0.0f,-6.0f);
  27.  
  28.     glBegin(GL_TRIANGLES);
  29.       glVertex3f( 0.0f, 1.0f, 0.0f);
  30.       glVertex3f(-1.0f,-1.0f, 0.0f);
  31.       glVertex3f( 1.0f,-1.0f, 0.0f);
  32.     glEnd();
  33.  
  34.     glTranslatef(3.0f,0.0f,0.0f);
  35.  
  36.     glBegin(GL_QUADS);
  37.       glVertex3f(-1.0f, 1.0f, 0.0f);
  38.       glVertex3f( 1.0f, 1.0f, 0.0f);
  39.       glVertex3f( 1.0f,-1.0f, 0.0f);
  40.       glVertex3f(-1.0f,-1.0f, 0.0f);
  41.     glEnd();
  42. }
  43. void VJOutput::Herteken(){
  44.     updateGL();
  45. }
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my VJ.pro file has:
Qt Code: 
  1. # -------------------------------------------------
  2. # Project created by QtCreator 2010-01-15T13:07:06
  3. # -------------------------------------------------
  4. QT += network \
  5.     opengl \
  6.     sql \
  7.     xml \
  8.     xmlpatterns \
  9.     phonon \
  10.     dbus
  11. CONFIG += thread
  12. TARGET = VJ
  13. TEMPLATE = app
  14. SOURCES += main.cpp \
  15.     mainwindow.cpp \
  16.     lib/Rhythm.cpp \
  17.     lib/MidiDevices.cpp \
  18.     lib/RtMidi.cpp \
  19.     visualLib/glscreen.cpp
  20. HEADERS += mainwindow.h \
  21.     lib/Rhythm.h \
  22.     lib/MidiDevices.h \
  23.     lib/RtMidi.h \
  24.     lib/RtError.h \
  25.     visualLib/glscreen.h
  26. LIBS += -L/alsa/ \
  27.     -lasound \
  28.     -lpthread
  29. FORMS += mainwindow.ui
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I'm using ubuntu and Qt Creator