glXChooseVisual does not handle GLX_RGBA correctly

[Geoff Levner <geoff dot levner at samcef dot com>]

I have an OpenGL-based application executing on a Sun, but displaying on 
a PC running Windows XP and an X server. The app requires a TrueColor 
visual, so when it calls glXChooseVisual, it passes GLX_RGBA in the 
attribute list. This works fine with another X server (Exceed), but when 
using Cygwin/X, glXChooseVisual fails to return a visual.

Running xdpyinfo would seem to indicate that the server has *only* 
TrueColor visuals (see the output below). And in fact if I remove 
GLX_RGBA from the attribute list, glXChooseVisual does return one of 
those visuals. If I ask for information about the visual with 
glXGetConfig, it responds that color buffers store color indices 
(GLX_RGBA is false), yet the application works correctly.

Anybody have a clue what is going on here?

Thanks,
Geoff

Output from xdpyinfo:

 number of visuals:    4
 default visual id:  0x22
 visual:
   visual id:    0x22
   class:    TrueColor
   depth:    24 planes
   available colormap entries:    256 per subfield
   red, green, blue masks:    0xff0000, 0xff00, 0xff
   significant bits in color specification:    8 bits
 visual:
   visual id:    0x23
   class:    TrueColor
   depth:    24 planes
   available colormap entries:    256 per subfield
   red, green, blue masks:    0xff0000, 0xff00, 0xff
   significant bits in color specification:    8 bits
 visual:
   visual id:    0x24
   class:    TrueColor
   depth:    24 planes
   available colormap entries:    256 per subfield
   red, green, blue masks:    0xff0000, 0xff00, 0xff
   significant bits in color specification:    8 bits
 visual:
   visual id:    0x25
   class:    TrueColor
   depth:    24 planes
   available colormap entries:    256 per subfield
   red, green, blue masks:    0xff0000, 0xff00, 0xff
   significant bits in color specification:    8 bits


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