DRI2 RGB / RGBA visual problems [WAS: Re: intel 2.6.0: EXA choppy, UXA has artifacts]

[Michel Dänzer]

On Wed, 2009-01-21 at 04:45 +0000, Peter Clifton wrote:
> 
> Questions to those who might know..
> 
> Should DRI2 be clearing the Alpha channel (even if it requires making a
> copy for these cases)?

It mustn't do this for pixmaps that actually have an alpha channel, and
it shouldn't need to otherwise.


> Should compiz be decorating RGB windows using shadows which require
> RGBA?

I don't think there should be a problem with that; traditionally compiz
doesn't reparent application windows but uses separate drawables for the
decorations.


> Is there some way to fake GL into thinking the non-copied texture from
> DRI2 is in fact RGB, not RGBA, just with a stride of 4 bytes?

That's basically how the DRI1 AIGLX zero-copy tfp code handles this. See
the code calling testTexOffset() in glx/glxdri.c and the corresponding
SetTexOffset hooks in
mesa/src/mesa/drivers/dri/{intel,r200,r300,radeon} . Something similar
should be possible with DRI2.


-- 
Earthling Michel Dänzer           |                http://www.vmware.com
Libre software enthusiast         |          Debian, X and DRI developer