Re: [AD] power-of-two textures?

[Elias Pschernig <elias@xxxxxxxxxx>]

On Tue, 2008-02-12 at 00:45 +1100, Peter Wang wrote:
> 
> > Another problem is maximum texture size. In theory, old drivers might
> > have a limit as low as 256x256 - but I guess every normally we could
> > expect at least 2048x2048. Still, if the user creates a 3000x500 bitmap,
> > I don't think this should be allowed to fail. So in a similar way, my
> > idea is to allow "composed bitmaps". Those are bitmaps consisting of
> > multiple smaller ones.
> 
> How would al_lock_bitmap work on them?

Hm, good question. One idea would be to slightly change the locking API:

Instead of the current:

ALLEGRO_LOCKED_REGION *
al_lock_bitmap_region(
	ALLEGRO_BITMAP *bitmap,
	int x,
	int y,
	int width,
	int height,
	ALLEGRO_LOCKED_REGION *locked_region,
	int flags)
void al_unlock_bitmap(ALLEGRO_BITMAP *bitmap)

Change it to:

ALLEGRO_LOCKED_REGION *
al_lock_bitmap_region(
	ALLEGRO_BITMAP *bitmap,
	int x,
	int y,
	int width,
	int height,
	int flags)
void al_unlock_bitmap(ALLEGRO_LOCKED_REGION *region)

Then add a ->next pointer to ALLEGRO_LOCKED_REGION which contains
additional regions in case the area overlapped several sub bitmaps. The
API change is necessary so they can be allocated and freed again.

Since al_lock_bitmap_region is a very low level operation (you have to
know the exact pixel format) I think this ->next pointer should not be a
big problem.

-- 
Elias Pschernig <elias@xxxxxxxxxx>