[Xorg] Re: Damage/Composite + direct rendering clients

[Jim Gettys]

On Tue, 2004-05-18 at 10:10, Andy Ritger wrote:

> OK, thanks for the explanation.  I'm not sure how applicable this
> is to the synchronization concerns I have, though.  My biggest
> concern (new damage occuring inbetween when the composite manager
> decides what to recomposite, and when it does the composite)
> wouldn't be helped by this XSync mechanism.
> 

One strategy is to recomposite *everything* on the screen...

Remember, we'll only actually do graphics operations on the damaged
part of the screen; the rest get clipped by the damage region.

> The other concern (how to make sure direct rendering has completed
> by the time the drawable is used as a source in a composite
> operation) conceptually would be solved as you describe, but I
> expect the implementation would be buried deeper -- either an X
> driver doesn't call into the core X server to notify it of damage
> until the direct rendered damage has completed, or the X server
> has to block, as Keith described, when it receives requests that
> uses the pending damaged drawable as a source.  Either way, I think
> it makes sense to leave this up to each vendor; the implementation
> details will likely be influenced by their architecture, etc.
> 

Yeah, we have to sweat through the details and see if this approach
all hangs together, and how DRI and the X server would interact.

The devil is in the details, as usual.
                                  - Jim

-- 
Jim Gettys <Jim.Gettys at hp.com>
HP Labs, Cambridge Research Laboratory