I have a class derived from QGraphicsView that creates a GUI only if created by the main.
So, this works:
Qt Code: 
  1. int main(int argc, char *argv[])
  2. {
  3. 	QApplication a(argc, argv);
  4.  
  6. 	scene.setSceneRect(0, 0, 1024, 768);
  7. 	scene.setBackgroundBrush(QColor::fromRgb(47, 51, 47));
  8.  
  9. 	gui view(&scene);
  10. 	view.setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
  11. 	view.setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
  12. 	view.setWindowFlags(Qt::FramelessWindowHint) ;
  13. 	view.setCacheMode(QGraphicsView::CacheBackground);
  14. 	view.setDragMode(QGraphicsView::NoDrag);
  15. 	view.setFixedSize(1024, 768);
  16. 	view.show();
  17.  
  18. 	return a.exec();
  19. }
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And this doesn't work:

Qt Code: 
  1. int main(int argc, char *argv[])
  2. {
  3. 	QApplication a(argc, argv);
  4. 	Starter s;
  5. 	return a.exec();
  6. }
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Qt Code: 
  1. class Starter : public QObject
  2. {
  3. 	Q_OBJECT
  4.  
  5. 	public:
  6. 		Starter();
  7. };
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Qt Code: 
  1. Starter::Starter()
  2. {
  4. 	s.setSceneRect(0, 0, 1024, 768);
  5. 	s.setBackgroundBrush(QColor::fromRgb(47, 51, 47));
  6.  
  7. 	gui view(&s);
  8.  
  9. 	view.setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
  10. 	view.setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
  11. 	view.setWindowFlags(Qt::FramelessWindowHint) ;
  12. 	view.setCacheMode(QGraphicsView::CacheBackground);
  13. 	view.setDragMode(QGraphicsView::NoDrag);
  14. 	view.setFixedSize(1024, 768);
  15. 	view.show();
  16. }
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Why ?

The main problem is that I need a GUI with an empty constructor as my main application will load a plugin (the GUI) that will create a GUI based on a QGraphicsScene.
So the Starter could create the QGraphicsScene and pass it to the gui class, but it doesn't work.