Re: [AD] C/Asm integration (was [AD] Improvement on alphablending...)

[George Foot <gfoot@xxxxxxxxxx>]

On Sun, Aug 05, 2001 at 08:27:45PM -0400, Bob wrote:
> George Foot wrote:
> > But as I said I might be misunderstanding -- I'm not really sure
> > what these blenders are.  Are they user-supplied?
> 
> No, but they could be.
>   Allegro comes with a few blenders, which are awefully slow. The idea 
> is to be able to work with full lines of pixels at a time, instread of 
> just 1 pixel at a time. This would greatly reduce the overhead of 
> function calls in the blender, and also allow working with several 
> pixels at a time to speed up computations.
>   I wanted to open the API up so users can use their own custom line 
> blenders, as well as provide backward compatibility support for pixel 
> based blenders (yb using a dummy blender which calls back the pixel 
> blender for every pixel). I'm not sure that's entirely doable now.

I think it's doable.  Your setup code before calling the line
blenders has to copy the source into a malloced block if it's
not already in the data segment, and bmp_select the dest bitmap.
Then C blenders read direct from the source buffer using
pointers, and read/write the dest using bmp_writenn etc, and asm
blenders read direct from the source buffer but read/write the
dest in the FS segment (I think).  For non-djgpp compilers we
need bmp_select to actually set FS to ES, which doesn't happen
at the moment.

George