Re: [PATCH] intel: fix fullscreen damage posting on pageflip

[Chris Wilson <chris@chris-wilson.co.uk>]

On Thu, 11 Oct 2012 18:12:18 +1000, Dave Airlie <airlied@gmail.com> wrote:
> On Thu, Oct 11, 2012 at 5:53 PM, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> > On Thu, 11 Oct 2012 14:30:29 +1000, Dave Airlie <airlied@gmail.com> wrote:
> >> From: Dave Airlie <airlied@redhat.com>
> >>
> >> While playing with MPX and sw cursor I noticed page flips won't
> >> end up misrendering some bits, so the sw cursor was replacing the
> >> bits on the wrong pixmap.
> >>
> >> Fix the damage handling to be correct and append damage before swapping
> >> the pointers and process damage after.
> >>
> >> This fixes misrendering with MPX cursors under a fullscreen compositor,
> >> that pageflips.
> >
> > Wow, what magic is this? The created region is the same and
> > front->drawable left unmodified by the exchange. The exchange only
> > manipulates the devPrivates and has not other side effects. The only
> > uncertain quantity there is the intel_glamor_exchange_buffers()...
> >
> > So the change is that we append the same damage to the same drawable
> > earlier, yet still process that damage at the same time, with no
> > apparent side-effects between the two operations. I'm just not
> > understanding why this has any effect.
> 
> Hence why I didn't do it right in the first place, I thought I
> understood how damage worked :-)
> 
> We have pre-rendering damage reporting and post-rendering damage
> reporting!, so sw cursors really wants it before the fact so it can
> copy the area out underneath itself,
> 
> damage append will process the pre-damage stuff, and pending will
> process post-damage hooks.

Thanks for the explanation, I had forgotten that not everything was
PostOp reported!

commit dadffd0061e2b14db397608e3cedfe9c76e546c8
Author: Dave Airlie <airlied@redhat.com>
Date:   Thu Oct 11 14:30:29 2012 +1000

    intel: fix fullscreen damage posting on pageflip
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre