[cairo] glitz_drawable_swap_buffer_region slow?

[David Reveman]

On Wed, 2006-03-01 at 21:09 +0100, stefan kersten wrote:
> On Wed, Mar 01, 2006 at 06:00:27PM +0100, David Reveman wrote:
> > Swapping part of a drawable is implemented using glCopyPixels from back
> > to front buffer and depending on the driver you're using this may or may
> > not be accelerated. When swapping the complete drawable a call to [glX|
> > agl...]SwapBuffers is made and that's always accelerated, it might even
> > be implemented as a buffer flip and is then basically free.
> 
> ok, thanks david. so how would i go about implementing
> partial updates efficiently? is there a way to find out
> wether glCopyPixels is accelerated or not? would it be
> better to draw each component into an offscreen surface and
> composite the results? how can i find out if cairo+glitz
> offscreen rendering is accelerated?

Keep using glCopyPixels, I don't no of any driver that accelerate
offscreen rendering but not glCopyPixels. I'd likely do some work soon
on the open source drivers to get fast copy from back to front buffer.

glitz_get_drawable_features can be used to check if cairo's glitz
backend will accelerate offscreen rendering.
GLITZ_FEATURE_FRAMEBUFFER_OBJECT_MASK bit should be present for
accelerate offscreen rendering.

> 
> sorry if the answers those questions are obvious ...
> 
> <sk>
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-David