[compiz] Composite retained drawing protocol

[David Reveman]

On Thu, 2007-03-01 at 20:19 -0500, Robert Carr wrote:
> I've recently drafted a rough idea of a composite manager agnostic
> protocol for leveraging the compositor for retained drawing in a way
> suitable for highly interactive and flexible applications.
> 
> It seems to be that for anything like this to be a success it would
> have to be developed with the support of multiple window managers, and
> I would appreciate any feedback, ideas, and contributions to the draft
> on behalf of the Compiz crowd.
> 
> The RFC is available at:
> http://wiki.freedesktop.org/wiki/Standards_2fComposite_2dretained_2ddrawing
> 
> PDF (much better formatting) at:
> http://gitweb.beryl-project.org/?p=users/racarr/architecture/.git;a=blob_plain;f=cmrds.pdf;hb=HEAD
> 

>From reading the draft it's not obvious that it's a retained mode
drawing interface. It looks more like an immediate mode drawing
interface to me.

Anyhow, whatever we'll come up with for retained mode rendering, I
strongly believe that the retained model should be completely separated
from the communication protocol.

I don't know what kind of retained mode drawing interface that will be
good for the future and I'm not really interested in selecting one. I'm
interested in coming up with a very general description that only
defines a loose hierarchical model which can be extended to fit whatever
retained mode drawing that we want today and tomorrow.

The current drawing code in compiz needs some work. It was originally
design for much less than what it's doing today, it still does a decent
job today. We've been extending and tweaking it to make it work for what
we want to do and we've been able to do this without making it too messy
but it's far from good. I have some pretty exciting ideas for how we can
re-design the drawing infrastructure in compiz and incrementally make
changes to get there. I'll send an outline for this to the compiz list
sometime soon so it can be discussed more. However, the re-design of the
compiz drawing framework relates very much to the need for being able to
provide retained mode drawing interfaces and I look forward to
discussing this more.

- David