allegro5，C-循环显示位图的副本

Question

In my program I load bitmap from file (source) and I want to copy it and display copy on the screen each time mouse button pressed. I pasted making copy and displaying bitmap, but it doesn't work. Displaying original works in my code.

    while( true )
    {
      ALLEGRO_EVENT event;
      al_wait_for_event( queue, &event );

      if( event.type == ALLEGRO_EVENT_KEY_DOWN && event.keyboard.keycode == ALLEGRO_KEY_ESCAPE )
      {
          destroy( queue, source, display );
          al_destroy_bitmap( copy );
          return 0;
      }

      if( event.type == ALLEGRO_EVENT_MOUSE_BUTTON_DOWN )
      {
          if( copy )
            al_destroy_bitmap( copy );

          copy = al_create_bitmap( al_get_bitmap_width(source), al_get_bitmap_height(source) );

          al_set_target_bitmap( copy );
          al_draw_bitmap( source, 0, 0, 0 );
          al_flip_display();
      }
    }

Answer 1

I've found a solution already, to do a deep-copy of bitmap : ALLEGRO_BITMAP* al_clone_bitmap( BITMAP* source) function can be used.

while( true )
{
  ALLEGRO_EVENT event;
  al_wait_for_event( queue, &event );

  if( event.type == ALLEGRO_EVENT_KEY_DOWN && event.keyboard.keycode == ALLEGRO_KEY_ESCAPE )
  {
      destroy( queue, source, display );
      al_destroy_bitmap( copy );
      return 0;
  }

  if( event.type == ALLEGRO_EVENT_MOUSE_BUTTON_DOWN )
  {
      if( copy )
        al_destroy_bitmap( copy );

      copy = al_clone_bitmap( source );
      al_draw_bitmap( copy, 0, 0, 0 );
      al_flip_display();
  }
}