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Re: [E-devel] Buffer canvas and transparent background

On Sat, 01 Apr 2006 09:56:12 -0500 Jason Tackaberry <tack@sault.org> babbled:

> Hi all,
> I've been quite out of the loop for a while (new job, relocated), so I
> haven't been following evas changes very well.  I've just upgraded from
> to 026 and I've noticed a change in behavior in the buffer
> canvas with respect to transparent (or rather I guess "undefined")
> backgrounds.
> Previously (with 022 and possibly other versions prior to 026) if I, for
> example, added a bit of text or an image to an otherwise empty canvas
> using the buffer engine, I could move the object without any artifacting
> problems.  This is in contrast with the X11 engine, for example, where I
> would often see artifacting in the object's previous position.  For X11
> engine, this behavior is understandable.  But now, in 026, I'm seeing
> this same issue in the buffer engine too.  If I move an object on a
> buffer canvas whose background is transparent, I see random artifacts in
> its previous position.  This issue persists in cvs as of today.
> I hope this is accidental behavior and not intentional.  We (the Freevo
> project) use evas's buffer engine to provide OSD over mplayer and xine,
> and transparent background is essential.  I haven't waded through any of
> evas's source yet to try to isolate the problem, but I was hoping it
> might be an issue easily recognized by a core developer :)
> Happy to provide more info.  Let me know.

how are you using it? using ecore_evas? are you using the update region
callback by hand (not ecore_evas) ? i am looking at the code here - if u ask
for EVAS_ENGINE_BUFFER_DEPTH_ARGB32 depth - it will zero out the alpha channel
every render update - but ONLY the regions rendered to. it won't do it on
startup though. so that might be your problem as those regions never get
objects and never get a render update as you manually manage your canvas and
damage regions (you don't send an initial one)

> Cheers,
> Jason.
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------------- Codito, ergo sum - "I code, therefore I am" --------------
The Rasterman (Carsten Haitzler)    raster@rasterman.com
Tokyo, Japan (東京 日本)