Hi Paul
I know what you want to achieve, but I really think this way around it is a very bad idea (as I mentioned in the past). The plugin-dissector code still runs in the epan context, and there it does not have a Qt reference it can apply for.
The GUI part of the plugin is another question, but for that you find the code in the pluginifdemo, where the selection is taking place in the uihandler wrapper, which has to decide if it should create a QApplication context or reuse Wiresharks context.
cheers,
Roland