glXChooseVisual does not handle GLX_RGBA correctly

Larry Hall (Cygwin X)
Mon May 14 12:17:00 GMT 2007

Geoff Levner wrote:
> 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?

Looks to me like you're app is looking for 32 bits while Cygwin-X is
only providing 24 bits.  Unless you know you absolutely need transparency,
I think you'll find everything works fine with the visuals you can get.
Just ask for GLX_RGB instead.

Larry Hall                    
RFK Partners, Inc.                      (508) 893-9779 - RFK Office
216 Dalton Rd.                          (508) 893-9889 - FAX
Holliston, MA 01746

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