Qt setGeometry: Unable to set geometry

This warning happens (at least to me) when the size of the widget results to be very small.

Set a minimum size for your widget (so it will be automatically positioned), like:

 // Widget constructor

 QVBoxLayout* vLayout = new QVBoxLayout();
 setLayout(vLayout);

 setMinimumSize(200,200);

You should also parent your widget to a QMainWindow, but will still work.