Re: memory efficient compisiting

On Tue, 2004-03-02 at 22:33, Matt Jones wrote:
> > I think it's likely that a stupid compositing system with lots of transparency
> > is going to easily exceed the bandwidth capability of current hardware if we do
> > it every retrace. So we need to write some code to minimize the per frame work
> > that needs to be done. Continuous composition does look doable with a normal
> > desktop mix where all of the windows aren't translucent. Also, nothing bad
> > happens if it takes two retraces to do a complex composition pass, I doubt if
> > you'll even notice.
> 
> "So we need to write some code to minimize the per frame work that needs
> to be done."
> 
> I was under the impression that this is what the DAMAGE extension does
> (return modified regions - why you can handle a full screen transparent
> object in software rendering). Please correct me if I'm wrong.

You are right.  That is what the damage extension does for
you.

What is more, Damage is clever, and accumulates damage until you tell
flush the region, so you can do a set of commands to composite
the windows onto the screen, knowing that they can be clipped
to the up-to-date areas of the screen that need updating :-).
                            - Jim
-- 
Jim Gettys <[email protected]>
HP Labs, Cambridge Research Laboratory