Your QwtPlot is probably eating the key events. Try implementing an event filter method in your QtPlotTab class (see QObject::eventFilter()) and installing it on the QwtPlot instance (QObject::installEventFilter()), and look for the key events there.

If you do that, be sure to pass the other events along if you aren't handling them. See the installEventFilter() docs for an example of how to do it correctly.

I also notice that you aren't initializing the base class of QtPlotsTab in the constructor. This could be part of your problem if the event loop isn't being set up properly for your class instance.