glXChooseVisual does not handle GLX_RGBA correctly
Larry Hall (Cygwin X)
Wed May 16 22:26:00 GMT 2007
Geoff Levner wrote:
> Larry Hall (Cygwin X) wrote:
>> 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
>>> 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.
> That sounds reasonable, but GLX_RGB is not defined, and I can't find any
> reference to it in the GLX 1.4 specifications. According to the
> documentation, GLX_RGBA just means you want TrueColor or DirectColor
> visuals; it says nothing about alpha. And we do not ask for any alpha
Yup, you're right. I was thinking of something else.
Perhaps it's just your combination of attributes. You might check that.
The combination below has worked for me before, albeit from a Linux
machine to Cygwin/X:
int visual_attributes =
Larry Hall http://www.rfk.com
RFK Partners, Inc. (508) 893-9779 - RFK Office
216 Dalton Rd. (508) 893-9889 - FAX
Holliston, MA 01746
Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
Problem reports: http://cygwin.com/problems.html
More information about the Cygwin-xfree