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Bug#405859: xserver-xorg-video-mga: freeglut error if there's no Virtual line in xorg config file

On Wed, 2007-01-10 at 23:39 +0100, Jens Seidel wrote:
> On Tue, Jan 09, 2007 at 09:07:15AM +0100, Michel Dänzer wrote:
> > On Mon, 2007-01-08 at 23:12 +0100, Jens Seidel wrote:
> > 
> > > > BTW, what exactly is GLUT_ALPHA supposed to achieve?
> > > 
> > > I'm not sure but believe it just enables Alpha Blending, e.g.
> s/e.g./i.e./ (stupid latin abbreviations)
> > > transparency.
> > 
> > Yes, AFAICT from a web search it requests that the drawable contains an
> > alpha component, which is only supported with the Composite extension.
> > So maybe changing the second option above to enable the Composite
> > extension makes a difference?
> No, it doesn't. Please note that I no longer search a solution, I assume
> it's just an error in the mga driver module as indicated by the many
> warnings and errors. 

If you mean the visual related warnings, those are mostly cosmetic and
harmless, see


They certainly don't prevent 32 bit ARGB visuals from working when the
Composite extension is enabled.

> Maybe it is also an OpenGL issue which doesn't allow me to try other
> options (GLUT_RGB instead of GLUT_ALPHA) if one is not supported since
> it seems to stop immediately IIRC.

Yes, libX11's (lack of) error handling sucks.

> > Note that blending such a drawable against
> > another drawable will not work correctly with hardware acceleration
> You refer to the Matrox driver not the general case, right?

It'll ultimately depend on the driver as well, but there still
infrastructural bits and pieces missing for this in the DRI.

> > currently though. Also note that GLUT_ALPHA is not necessary for alpha
> > blending while rendering to the drawable.
> Since I'm not completely sure about this I prefer not to remove it.
> Otherwise it could result in bogus effects.

We might be able to make a guess whether it's really necessary if you
could point us to the app in question or at least describe what it's
trying to achieve.

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

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