[SDL] DirectX 7?

Neil Griffiths n.griffiths at virgin.net
Thu Sep 26 06:58:00 PDT 2002


DO> It might be better if it dropped back to DX3 - but then again, anyone
DO> that actually cares could just contribute a backend for it, if it's that 
DO> important...

Sure, for certain. I'm not against having a DirectX7 backend either -
I'm just against people saying "No! Not DirectX8! It wouldn't work!"
when it would.

DO> Good point. And we either have prefectly fine OpenGL support, or
DO> basically no acceleration at all. Same situation, really; DX8 or GDI - 
DO> OpenGL or Xlib/fbdev/<whatever>.

Absolutely, that's my point. :)

DO> Right. There's only one thing I'm worried about: How do you take
DO> advantage of the power of OpenGL and DX8 while still maintaining the same 
DO> API for 2D APIs and software rendering?

Now THAT is an issue for discussion, I agree. But then, at a most
basic level, what 2D graphics could we do using OpenGL and DX8 that we
couldn't support using DirectDraw or fbdev? I mean, so long as we keep
it simple so that we're still providing a surface, the same palette
information and so on, I don't see a problem. As long as externally
it's the same...

Of course, you would know more about this than me because of your work
on glSDL. :)

DO> The obvious way is the way of the current glSDL; just don't provide 
DO> anything new but raw speed. glSDL even deliberately "breaks" surface 
DO> alpha on RGBA textures the same way SDL does, just to be compatible.

Then why couldn't we change way the alpha works so that we get the
speed advantages in OpenGL/DX8 and it still works in software?

DO> The other way is to figure out a reasonable feature set for "advanced 
DO> 2D", and make sure that there's a software fallback for every feature 
DO> added. Some things (like sub-pixel accurate blitting) could simply be 
DO> ignored when there's no acceleration, but transformations and blending 
DO> effects aren't that easy to fake...

Yes, I see where you're coming from. Well, as for blending, are you
just talking alpha here? That's not so hard to fake - but it is, of
course, slow. And I guess by transformations you mean rotations and
perhaps even skewing? If so, is this something that we'd want to
provide from a _Simple_ DirectMedia Layer?

I guess it would be best to come up with a wish-list of the features that
people would like to see supported by SDL 2.0 and design an API based
around that and see if there would be any obvious flaws or benefits...


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