Hi.

I've downloaded a simple application to see how I can draw using Opengl.

The project has only the main.cpp that have the following code:
Qt Code: 
  1. #include <QtGui/QApplication>
  2. #include <QGLWidget>
  3. #include <QHBoxLayout>
  4. #include <QSize>
  5. #include <QPushButton>
  6.  
  7. class MyGLWidget : public QGLWidget
  8. {
  9.     Q_OBJECT
  10. public:
  11.     MyGLWidget (QWidget* parent ) : QGLWidget(parent)
  12.     {
  13.     }
  14.     float red, blue, green;
  15.     void initializeGL()
  16.     {
  17.         red = 0;
  18.         blue = 0;
  19.         green = 0;
  20.     }
  21.  
  22. public slots:
  23.  
  24.     void resetColor()
  25.     {
  26.         red = 0;
  27.         blue = 0;
  28.         green = 0;
  29.         update();
  30.     }
  31.  
  32.     void paintGL()
  33.     {
  34.         red += 0.007;
  35.         blue += 0.002;
  36.         green += 0.005;
  37.         glClearColor(red,green,blue,0);
  38.         glClear(GL_COLOR_BUFFER_BIT);
  39.     }
  40. };
  41.  
  42.  
  43. class MiaMainWindow:public QWidget
  44. {
  45. public:
  46.     MiaMainWindow ():QWidget(NULL){
  47.         MyGLWidget *glWidget = new MyGLWidget(this);
  48.         QHBoxLayout *layout = new QHBoxLayout(this);
  49.         QPushButton *button = new QPushButton("Get to the Choppa!!!", this);
  50.         setLayout(layout);
  51.         layout->addWidget(glWidget);
  52.         layout->addWidget(button);
  53.         connect(button, SIGNAL(clicked()),glWidget, SLOT(resetColor()));
  54.         setWindowTitle("Hello World!");
  55.         sizeHint();
  56.     }
  57.  
  58.     QSize sizeHint() const
  59.     {
  60.         return QSize(100,100);
  61.     }
  62.  
  63. };
  64.  
  65. int main(int argc, char** argv){
  66.  
  67.     QApplication app(argc, argv);
  68.     MiaMainWindow win;
  69.     win.show();
  70.     int res = app.exec();
  71.     return res;
  72. }
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and the .pro is the following one:

Qt Code: 
  1. #-------------------------------------------------
  2. #
  3. # Project created by QtCreator 2011-09-14T20:01:51
  4. #
  5. #-------------------------------------------------
  6.  
  7. QT       += core
  8. QT       += gui
  9. QT       += opengl
  10.  
  11. TARGET = tryme
  12. CONFIG   += console
  13. CONFIG   -= app_bundle
  14. TEMPLATE = app
  15. SOURCES += main.cpp
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But, when I compile it (using qtcreator 2.3.0 with Qt 4.7.4 and MinGW 4.4), I've the following errror:

debug/main.o: In function `MyGLWidget':
dir\tryme-build-desktop-Qt_4_7_3_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../tryme/main.cpp:12: undefined reference to `vtable for MyGLWidget'
dir\tryme-build-desktop-Qt_4_7_3_for_Desktop_-_MinGW_4_4__Qt_SDK__Debug/../tryme/main.cpp:12: undefined reference to `vtable for MyGLWidget'
collect2: ld returned 1 exit status
mingw32-make[1]: *** [debug\tryme.exe] Error 1
mingw32-make: *** [debug] Error 2
The process "C:\QtSDK\mingw\bin\mingw32-make.exe" exited with code 2.
Error while building project tryme (target: Desktop)
When executing build step 'Make'
I've read something about this error but I don't know where's the error. Can anyone help me, please?

Thanks in advance for your replies.

Regards.