[SDL] 2D Accelerated Hardware Support?

[Mattias Engdegård]

>Not exactly true.  For the longest time, X has had XAA acceleration.

XAA as a name and architecture is new in XFree 4.0. The XFree86 server has
had 2D acceleration for years, but that was not the point since SDL does
not use it. It applies to window to window copies, scrolling, some drawing
primitives, and (recently) to non-shared pixmaps; none of which SDL can
easily use.

>Sure - you could run svgalib GL quake under linux, but thats a single
>video card.  During that time there was already quite a bit of work done
>on making use of video card acceleration.  And this has *nothing* todo
>with DGA 1.0.  Theres more about video card acceleration than just DGA, I
>believe.

I'm not aware that DGA 1 gave you any acceleration at all; it just
presented a dumb frame buffer that you could access over a slow bus.

>Belew, you describe the conditions to get DGA 2.0.  While DGA gives you
>better acceleration, it doesn't mean you aren't using acceleration if you
>aren't using DGA.

Unfortunately, for the purposes of SDL in 2D, it does. Without DGA2,
all you can do is to memcpy directly into video memory (with DGA1),
or use XShmPutImage to let the X server do the same thing, with
about the same (low) speed. (XFree 4.x does this apparently faster on
some hardware, but it still does not use hardware acceleration for blits.)