set_display_switch_callback - Installs a switching notification callback. Allegro game programming

       Installs a notification callback  for  the  switching  mode  that  was  previously  selected  by  calling
       set_display_switch_mode().  The  direction  parameter  can  either  be SWITCH_IN or SWITCH_OUT, depending
       whether you want to be notified about switches away from your program or back to your  program.  You  can
       sometimes  install  callbacks for both directions at the same time, but not every platform supports this.
       You can install several switch callbacks, but no more than eight on any platform.

       set_display_switch_callback  -  Installs  a  switching  notification  callback.  Allegro game programming
       library.

       Returns zero on success, decreasing the number of empty callback slots by one. Returns -1 if the  request
       is impossible for the current platform or you have reached the maximum number of allowed callbacks.

remove_display_switch_callback(3alleg4), set_display_switch_mode(3alleg4), exswitch(3alleg4)

Allegro                                           version 4.4.3             set_display_switch_callback(3alleg4)

#include<allegro.h>intset_display_switch_callback(intdir,void(*cb)());