Xrender cursor performance / double buffering?

[Adam Jackson]

On Tue, 2007-04-17 at 13:07 -0400, Jim Gettys wrote:
> Jordan,
> 
> One can compute the cursor image once to match the depth of the root
> window once and store it in devprivates.  Then the server can composite
> the image using the fast path image compositing hardware, no matter what
> the depth is (it won't matter if computing the cursor to match the
> screen takes a bit of time; it's the compositing while the cursor moves
> that really hurts).

That won't work if the root window depth is 16.  You won't have any
place to store your alpha channel.  You can do a transparency blit, but
then your smooth edges go away.

Also, the software alpha cursor code in X sucks out loud.  It'll use the
normal Render path, yes, but it still blinks violently.

- ajax