I already saw that thread but its not exactly what i want to do. I need an event that detects only once if the focus is lost or the focus got back. It goes more in the direction of UGameViewportClient::LostFocus and UGameViewportClient::ReceivedFocus but Im not sure how to implement it. I`m relatively new to c++ and unreal programming. I already looked at https://answers.unrealengine.com/questions/225658/application-lost-focus-event.html