QOpenGLWindow initializes very slow

[Xv1nX]

Hi guys,
i am playing around with QOpenGLWindow, so i created an example project just like the one of Laszlo Agocs on following site:
qt-weekly-20-completing-the-offering-qopenglwindow-and-qrasterwindow

i just create a subclass with:

Window() : QOpenGLWindow(NoPartialUpdate) {
    QSurfaceFormat format;
    format.setDepthBufferSize(24);
    format.setStencilBufferSize(8);
    setFormat(format);
}

and paint a triangle in paintGL().

The problem is: the blank window pop up for about 1-2 seconds, then the triangle appears. Is there a way to speed up the initializeGL phase? there is an error if i manually call initializeGL().

Thanks in advance,
Vince