Here is a patch that enables SGI_make_current_read for the MGA driver.
I have only tested this with progs/xdemos/wincopy, and it works as
expected. It should be fairly trivial for people to make similar
patches for the other drivers. Drivers that support pageflipping will
be a bit more tricky, but that shouldn't be a significant problem.
Assuming everyone likes this patch, I'll commit it tomorrow.
HOWEVER, the wincopy demo runs about as fast with this patch as with
indirect, software rasterization. The software path for glCopyPixels is
*death*. Could people who are working on drivers *please* implement
screen-to-screen blits for at least the common, easy cases of
glCopyPixels? I understand that glCopyPixels isn't a common performance
critical path, but the a lot of the code used to accelerate that should
be re-usable for accelerating glCopyTexImage and some other pbuffer
related functionality when the time comes.