GetModuleHandle(NULL) get the exe handle. Sometimes the window couldn't be found because the window wasn't created in the .exe but in a dll. Thats why I list all dll HANDLES and try to find the main window handle.
Every class has a job. Overlay is to show an overlay not to hook windows functions.
Hook_Manager's job is to manage hooks and should not contain a reference to the overlay. (It should not contains any reference to directX or OpenGL either but I'll see that later... Maybe)
This makes the overlay code much cleaner and "could" be used in Linux as well.