frameGeometry vs Geometry

[bossy]

I read a few post about this and somehow I'm still not clear on how i get the frame size of my main window.

in this exemple, geometry and frameGeometry only have 1 of difference. I get the same result if i query after the window is painted

QGraphicsScene *scene = new QGraphicsScene();
    myview = new QGraphicsView(scene);
    QRect myrect = this->geometry();
    QRect frameRect = this->frameGeometry();

QGraphicsScene *scene = new QGraphicsScene();
    myview = new QGraphicsView(scene);
    QRect myrect = this->geometry();
    QRect frameRect = this->frameGeometry();

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ultimately i want to be able to move my child widget only within the frame of my main window

thanks