Re: Module Proposal: GNOME Shell

[Emmanuele Bassi <ebassi gmail com>]

On Sun, 2010-04-04 at 11:57 +0800, Sam Spilsbury wrote:

> > There is very little that GNOME Shell does that makes it *inherently*
> > more demanding than Compiz.
> 
> Actually, there is.
> 
> Mutter runs on Clutter, which requires full scene-graph calculations
> and currently cannot handle damage events correctly the last time I
> checked (since it redraws the whole screen).

Clutter 1.2, which is what GNOME Shell requires, does sub-region updates
using the damage events and the copy_sub_buffer extension. the approach
used was limited to texture_from_pixmap actors currently because it was
deemed to unstable to land in every actor in time for the 1.2 release,
but for 1.4 clipped updates are going to be used more and more by
Clutter and by toolkits based on Clutter, since we expose the ability to
queue clipped redraws at the scene graph level.

> In terms of virtualized drivers, Owen is correct in saying that they
> are optimized for the binding method compiz uses, although as far as
> we can tell clutter and kwin don't implement the
> EXT_texture_from_pixmap specification quite as correctly as they
> could, so that is why you see slowness or rendering issues  on virtual
> machines.

I am not aware of any implementation issues for our texture_from_pixmap
actors - though they are a bit convoluted (something we really want to
fix in Clutter 1.4).

having said that, if Clutter is not implementing the support for a GLX
extension correctly then bugs should be filed so that we can fix it. if
VMs (and drivers) require some hand-holding then we're definitely
interested in fixing Clutter.

ciao,
 Emmanuele.

-- 
W: http://www.emmanuelebassi.name
B: http://blogs.gnome.org/ebassi