Re: [Mesa3d-users] Why no RGBA visual in XFree86 4.1 software Mesa?

[Brian P. <br...@tu...>]

Brian Paul wrote:
> 
> Geoffrey Broadwell wrote:
> >
> > Unfortunately, I've had no luck with this problem in any of the XFree86
> > places I've tried (the newbie and xpert mailing lists, as well as
> > #xfree86), but I did get a response to try my question here.  So here
> > goes:
> >
> > I'm trying to get Perl's OpenGL support working on my systems, which do
> > not currently have hardware acceleration support under Mesa.  However,
> > Perl's OpenGL support requires an RGBA visual,
> 
> Perl shouldn't require an alpha channel.  The OpenGL spec says they're
> optional.  But anyway...
> 
> > but for some reason the
> > visuals available under software Mesa (the one builtin to XFree 4.1) are
> > all RGB-only for me.
> >
> > I've hit the same problem on both a laptop and a desktop, both installed
> > recently with Debian Woody, and both running the 4.1.0-16 X packages.
> > The XF86Config-4 files were both built using the debconf magic in the
> > X packages.  Both are running at 1024x768, 24-bit color, with 4MB RAM.
> > The systems both have lots of system memory available, 128MB on one, and
> > 256MB on the other.  Attached are the output of xdpyinfo and glxinfo; let
> > me know if you need the contents of the XF86Config-4 and/or XFree86.0.log
> > files.
> >
> > Anyone have any clue what's going on?  As far as I can interpret the tea
> > leaves in the X log, it looks like I'm really running with 32-bit pixels,
> > so I don't see a problem there, assuming that for some reason Mesa was
> > fixing its internal pixel format to X's.
> 
> The file that needs attention is xc/programs/Xserver/GL/mesa/src/X/xf86glx.c.
> That's where a set of default GLX visuals are defined for the case in
> which we don't have a DRI hardware accelerated driver.
> 
> If you feel adventurous and want to compile a new GLX module you could
> try editing that file and adding a GLX visual with an alpha channel.
> 
> Otherwise, I'll try to fix this for a future release since it would be
> useful to have a visual with alpha.
> 
> Another work-around would be to use stand-alone Mesa (which builds a libGL
> that knows nothing about the X server's GLX) since it supports visuals with
> alpha channels.  glxinfo won't report a visual with alpha but if you
> request it with glXChooseVisual() you'll get it. (long story)


I've changed xf86glx.c so that there's now a GLX visual with an alpha
channel.  It's always 8 bits deep even if the RGB depths are 5/6/5 or
3/3/2 since it's allocated by Mesa with a malloc'd buffer, not part of
the actual framebuffer.

-Brian