SDL_ActiveEvent- Application visibility event structure
0 if the event is a loss or 1 if it is a gain.
SDL_APPMOUSEFOCUS if mouse focus was gained or lost, SDL_APPINPUTFOCUS if input
focus was gained or lost, or SDL_APPACTIVE if the application was iconified
(gain=0) or restored(gain=1).
SDL_ActiveEvent is a member of the SDL_Event union and is used when an event of
type SDL_ACTIVEEVENT is reported.
When the mouse leaves or enters the window area a SDL_APPMOUSEFOCUS type
activation event occurs, if the mouse entered the window then gain will be 1,
otherwise gain will be 0. A SDL_APPINPUTFOCUS type activation event occurs when
the application loses or gains keyboard focus. This usually occurs when another
application is made active. Finally, a SDL_APPACTIVE type event occurs when the
application is either minimised/iconified (gain=0) or restored.
This event does not occur when an application window is first created.