[PATCH] complete (I hope!) i830 EXA support

Alex Deucher alexdeucher at gmail.com
Mon Sep 12 07:12:55 PDT 2005

On 9/12/05, Keith Packard <keithp at keithp.com> wrote:
> On Sun, 2005-09-11 at 23:21 -0400, Alex Deucher wrote:
> > most hardware overlays support alpha blending with the graphics layer,
> > couldn't we hook that in some way with render?  Like if it's Xv, short
> > circuit to the overlay  blend rather than compositing.
> (I'm not familiar with this kind of hardware, having only dealt with
> color-key based overlays myself).
> Figuring out when you could use this particular capability in the
> current framework would be pretty tricky, I suspect you'd have to expose
> it to the compositing manager and let it set things up when possible.
> A lot of the use cases I've seen place graphics translucently over the
> video though, which doesn't seem like it will work here.

Radeon for example supports 3 overlay modes: color-key, global alpha,
and per-pixel alpha (last one only works with ARGB visuals).  I've
implemented global alpha in the current radeon Xv driver.  you can
specify alpha values for the graphics layer and the overlay.  It
actually works quite well if you turn off the colorkey.  Savage has
similar capabilites.  I'm sure others may as well.  The DirectFB
compositing layer is able to utilize these features.
Unfortunately, I'm not too familiar with how I would need to hook this
into composite to make it work or attempt to make it work.


> -keith
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