I have developed a full-screen application that hooks into and launched by a 3rd party/client application. The problem is that the client application gets focus soon after it launches my application, with the result that although my application is full screen, and set to be on top, it does not receive keyboard input, as such the user has to click on it to bring it to focus, which makes for a poor user experience.

How can I restore focus to my application after the client acquires it? 

If it matters, my application is written in C++ and has a QT UI.