How come allegro automatically handles minimize button, but not close button?

Question

Here is a sample from Allegro5 tutorial: (to see the original sample, follow the link, I've simplified it a bit for illustratory purposes.

#include <allegro5/allegro.h>

int main(int argc, char **argv)
{
   ALLEGRO_DISPLAY *display = NULL;
   ALLEGRO_EVENT_QUEUE *event_queue = NULL;
   al_init()
   display = al_create_display(640, 480);
   event_queue = al_create_event_queue();
   al_register_event_source(event_queue, al_get_display_event_source(display));
   al_clear_to_color(al_map_rgb(0,0,0));
   al_flip_display();
   while(1)
   {
      ALLEGRO_EVENT ev;
      ALLEGRO_TIMEOUT timeout;
      al_init_timeout(&timeout, 0.06);
      bool get_event = al_wait_for_event_until(event_queue, &ev, &timeout);
      //-->// if(get_event && ev.type == ALLEGRO_EVENT_DISPLAY_CLOSE) {
      //-->//   break;
      //-->// }

      al_clear_to_color(al_map_rgb(0,0,0));
      al_flip_display();
   }

   al_destroy_display(display);
   al_destroy_event_queue(event_queue);

   return 0;
}

If I don't manually check for the ALLEGRO_EVENT_DISPLAY_CLOSE, then I can't close the window or terminate the program (without killing the process through task manager). I understand this. But in this case I don't understand how the minimize button works without me manually handling it. Can someone please explain?

Answer 1

Disclaimer: I don't know Allegro.

Minimizing a window at the most basic level only involves work from the process that deals with the windows (the Window Manager), not the process itself. Terminating a program, usually requires files to be closed or memory to be freed or something else that only the process itself can do.