Qt GUI design programmatically

I'm try to create a GUI application.

The main window, a QMainWindow, contains 9 labels with fixed size and also the size of the main window.

I tried to make it programmatically without Qt GUI Designer. The project is built without error but I cannot see any label nor layout shown on the main window. it's just blank.

Here is my source code:

WCwindow::WCwindow()
{
   // initialize widgets with text
   CAM111 = new QLabel("CAM 01");
   CAM121 = new QLabel("CAM 02");
   CAM131 = new QLabel("CAM 03");

   CAM211 = new QLabel("CAM 04");
   CAM221 = new QLabel("CAM 05");
   CAM231 = new QLabel("CAM 06");

   CAM311 = new QLabel("CAM 07");
   CAM321 = new QLabel("CAM 08");
   CAM331 = new QLabel("CAM 09");

   CAM111->setFixedSize(wcW,wcH);
   CAM121->setFixedSize(wcW,wcH);
   CAM131->setFixedSize(wcW,wcH);
   CAM211->setFixedSize(wcW,wcH);
   CAM221->setFixedSize(wcW,wcH);
   CAM231->setFixedSize(wcW,wcH);
   CAM311->setFixedSize(wcW,wcH);
   CAM321->setFixedSize(wcW,wcH);
   CAM331->setFixedSize(wcW,wcH);

   QGridLayout *layout = new QGridLayout;
   layout->addWidget(CAM111,0,0);
   layout->addWidget(CAM121,0,1);
   layout->addWidget(CAM131,0,2);

   layout->addWidget(CAM211,1,0);
   layout->addWidget(CAM221,1,1);
   layout->addWidget(CAM231,1,2);

   layout->addWidget(CAM311,2,0);
   layout->addWidget(CAM321,2,1);
   layout->addWidget(CAM331,2,2);

   setLayout(layout);

   setWindowTitle("Camera Window");
   setFixedSize(1000, 800);

}

of course, the class is initialized and evoked in main.cpp:

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    WCwindow *WCwin = new WCwindow;

    WCwin->show();

    return app.exec();
}

what kind of bug am I having??