+ Displays a system menu containing the list of various windows
+ commands in the window title bar. Unlike wxMINIMIZE_BOX,
+ wxMAXIMIZE_BOX and wxCLOSE_BOX styles this style can be used without
+ wxCAPTION, at least under Windows, and makes the system menu
+ available without showing it on screen in this case. However it is
+ recommended to only use it together with wxCAPTION for consistent
+ behaviour under all platforms.