[MPlayer-dev-eng] draw_alpha_* reads from video mem :((

[D Richard Felker III]

While looking into some performance problems (slowdown with subtitles;
fine without them), I realized that the draw_alpha_* functions read
from the same destination image they're writing to. This is a very bad
thing if the image is in video memory. I'd like to change it so that
when direct rendering isn't in use, the vo driver can use the mpi
passed to it from the filter layer as the source for draw_alpha_*
(modifying draw_alpha_* to take a third buffer, sourceimage). However,
this will not work with slices as far as I can tell, since the vo
driver never seems to get the mpi. Is there any reasonable way around
this problem?

Rich