Re: GDK-DirectFB Patches

["Mike Emmel" <mike emmel gmail com>]

On Dec 6, 2007 9:56 AM, Carl Worth <cworth cworth org> wrote:
> On Thu, 06 Dec 2007 09:44:55 +0100, Denis Oliver Kropp wrote:
> > Carl Worth wrote:
> > > For interleaving cairo and non-cairo rendering, cairo provides the
> > > cairo_surface_flush and cairo_surface_mark_dirty APIs. Does
> > > cairo-directfb implement those and does your application use them.
> >
> > Thanks for the pointer. The cairo-directfb backend seems to do nothing
> > in these functions. I'm not sure what it's supposed to do. Should the
> > first accumulate a region to flip and the second actually flips?
>
> I don't know how cairo-directfb surface is implemented exactly. So
> I'll describe the general concepts and then illustrate them by way of
> a fictitious "shadow" backend that is implemented with a
> cairo-image-surface internally and can copy back and forth between
> that and some underlying "system" object.
>
> When an application wants to switch from cairo- to non-cairo-based
> drawing it should call cairo_surface_flush. In this case, our shadow
> backend would copy its state from the image surface to the underlying
> system. (Ideally it would copy a minimal region based on the extents
> of cairo drawing operations that have occurred, but cairo's current
> backend interfaces don't make it easy to know this. But there would be
> no API impact from improving that.)
>
> Then, when an application wants to switch back from non-cairo- to
> cairo-based drawing it should call cairo_surface_mark_dirty_rectangle
> one or more times. Our shadow backend would accumulate a region from
> these rectangles and before the next cairo drawing operation would
> copy that region from the system to the image surface.
>
> Does that make sense?
>
> -Carl
>

Yes Carl this support was added after I stopped actively working on
the Cairo DFB backend.
When we have a format mismatch then a shadow may be the right answer.
Note for directfb you can ask for a different buffer format i.e ARGB
for a window.
But we probably still want to use dirty regions for flipping.

I don't think your getting all of the emails on the topic but it
finally looks like a lot of people
are looking at the problem.

So for now lets see how this resolves.
I know I pulled my hair out on it for a while :)