X11 acceleration issues

random stuff:

(1) A co-worker, hacking on voodoo3 code, claims it is able to
do both accelerated colourkeyed blits and masked blits. Thus X11 should
be able to make use of that even for copies with a clip_mask, making
an accelerated X11 target for SDL much more workable.

Can anyone with XFree86 4.x confirm this, is XCopyArea with a clip_mask
accelerated?

(2) Keith Packard’s new X11 Rendering extension is interesting. Especially
useful for SDL are the new compositioning (alpha-blending) operator
and the transform operator (since most of us agree that it would be
nice to have stretches/rotations in SDL one day).
However it seems that he uses premultiplied alpha exclusively, which
neither SDL nor OpenGL does. Can common video hardware use premultiplied
alpha?

This may not be a problem in practice, as long as hardware surfaces
are created once, and rarely used in any other way than for blitting
to the screen. SDL may have to add support for premultiplied alpha
if that would make operations faster, but right now we don't do it
to cut down on needless complexity (and to have the same format as
openGL).