Remove setting of background-color on iconed group box children just in case that was causing Tiy's problem. Is useless until PaintOnScreen + border-radius is resolved anyway.
#include <QApplication>
#include "mainform.h"
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
MyWindow *mainWin = new MyWindow;
mainWin->show();
return app.exec();
}