Demonstration of "callback function" in C

callback.c

void *(mouse_listener)(int, int);

// Print coordinates if mouse is clicked
void on_mouse_clicked(int x, int y){
  printf("%d, %d", x, y);
}

// Tell other code what to do when mouse is clicked by registering a event listener
void register_mouse_listener(void *(func_pointer)(int, int)){
  mouse_listener = func_pointer;
}

// The actual code that does mouse click (usually this is done elsewhere by other code,
// but we can simulate the functionality here)
void click_mouse(int x, int y){
  do_something();
  if(NULL != mouse_listener)
   (*mouse_listener)(x, y);
}

int main(){
  register_mouse_listener(on_mouse_clicked);
  click_mouse(100, 200);
  // on_mouse_clicked will be called;
}