[info-performer] Looking for the best visual, glxinfo problem

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From: Dan Johnston (dan.johnston++at++nrc.ca)
Date: 12/11/2003 05:31:37

I have a problem interpreting the data from glXGetConfig.

I decided to write my own version of code to select the best visual for
use by Performer applications. By calling this new function, any
application should get the best of the available visuals on any display,

any operation system.

I know about the pfuChooseFBConfig function in pfutil (and looked
at the source), I have a copy of wglinfo source to check visuals
on MS-Windows. I am planning to make my own function which
is usable on all platforms supported by Performer.

Why? Because the existing code does not include a bias for stereo.
I want stereo if at all possible, even if I loose depth on the buffers.
If no stereo visual is available, then I will consider the 'best' of
the existing visuals, but I need to set a flag to tell my code not
to try any active stereo modes.

My problem is that glXGetConfig returns more positive 'hits'
than I would expect, based on the output from glxinfo on my
test O2. I will be trying a similar test on the Onyx Monster.

If I type 'glxinfo -t' I get lots of stuff on the O2, but only 2
stereo, doublebuffered, truecolor visuals are shown...

Vis Vis Visual Trans buff lev render DB ste color buf aux dep
ste accum buf MS MS
ID Dep Type parent size el type reo r g b a buf th
ncl r g b a num bufs
-----------------------------------------------------------------------------------------------

...
0x30 15 TrueColor 0 16 0 rgba 1 1 5 5 5 1 0 0
0 16 16 16 16 0 0
0x31 15 TrueColor 0 16 0 rgba 1 1 5 5 5 1 0 24
8 16 16 16 16 0 0

As you can see, these are visual ID 30 with a depth of 0, and ID 31 with
a depth of
24. So a no brainer, you pick visual 24. Right? Well my calls to
glXGetConfig
to search for STEREO to be TRUE finds 3 visuals. IDs 30 and 31 both
have
a depth of 15, and ID 32 (which is not even listed by glxinfo) has a
depth of
24.

So which output is correct? Do I trust glxinfo and try to find a bug in
my code
or do I trust my own simple calls and ask for an un-listed visual?

Thanks for any comments and suggestions!

Dan.Johnston++at++nrc.gc.ca

BTW. My O2 is running 6.5.20m. 

--
      ___|__    |
      /  |  \   ||\      Daniel (Dan) Johnston
     /___|___\  || \     Dan.Johnston++at++nrc.gc.ca
    _____|____  ||  \    National Research Council of Canada, London, ON
    |    |    | ||   \   Integrated Manufacturing Technologies Institute
\___|    |    | ||____\  Tel: (519) 430-7081   Fax: (519) 430-7090
 \_o_\___|____|_|______\_    Inst: http://www.nrc.gc.ca/imti
  \                o /    These opinions are my own! Not those of NRC.
   \________________/    Virtual Reality:
                        http://www.nrc.ca/imti/vetc/home.html
 More Tall Ships - Fewer Computers!

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