Register a callback to be fired whenever the app is put into the background.
#include <glview/glview.h>
GLVIEW_API int glview_register_background_callback(background_callback background_callback)
The callback to be fired on a background event. If this parameter is NULL then any previously set callback is disabled.
Calling glview_register_background_callback() with a NULL background callback will disable any previously set callback from being fired on a background event.
GLVIEW_SUCCESS