al_register_bitmap_loader( ".ext", ?*(*al_loader

al_register_bitmap_loader( ".ext", ?(al_loader_fnxn)? )

Durendal

Member #16,024

July 2015

The title refers to the unknown second argument desired by the al_register_bitmap_loader() function. In fact, the documentation and the MSVS snippet auto-completer disagree on exactly what it wants, the former designating an "ALLEGRO_BITMAP *(*loader)(const char *filename)"; the latter demanding an "ALLEGRO_IIO_LOADER_FUNCTION loader". I assume that these types are identical, though how this is so is beyond my ken, and all attempts to satisfy the wanton desires of this function have proven fruitless.

So I am asking for someone to explain in clear terms the reason why this function was implemented and how to provide it an argument which allows me to make use of it. ( I am aware that the NULL pointer allows you to compile without error, but it still precludes actual use of it to load bitmaps, which is the whole idea. )

RPG Hacker

Member #12,492

January 2011

I'd assume you just need to pass it any pointer to a function that returns and ALLEGRO_BITMAP* while taking a const char*. This would make most sense, if you think about it.

As an example:

#SelectExpand
  1ALLEGRO_BITMAP* load_psd_file(const char* filename)
  2{
  3    /* Code for loading a PSD file here */
  4}
  5
  6int main()
  7{
  8    /* Allegro initialization code here */
  9
 10    al_register_bitmap_loader(".psd", &load_psd_file);
 11
 12    ALLEGRO_BITMAP* bitmap = al_load_bitmap("GameDataFolder/MyTestBitmap.psd");
 13
 14    /* Draw bitmap to screen here */
 15
 16    /* Free resources here */
 17
 18    return 0;
 19}