One thing I can tell you is happening is that the properties you have seen and applied in qt designer dont appear at run time. In my case, I had manual code to set the stylesheet of my qframe subclass to give it a background color. This made it visible by showing the background. On the other hand the frame is not visible even if I try to set it programatically which brought me to this forum. Also, the subclassed qframes I had instantiated without setting the background color using stylesheet appear invisible to me as well.