remove_display_switch_callback man page
remove_display_switch_callback — Removes a switching notification callback. Allegro game programming library.
void remove_display_switch_callback(void (*cb)());
Removes a notification callback that was previously installed by calling set_display_switch_callback(). All the callbacks will automatically be removed when you call set_display_switch_mode(). You can safely call this function even if the callback you want to remove is not installed.