glxgears: couldn't get an RGB, Double-buffered visual ?

Jie Luo clotho67 at
Tue Apr 8 15:25:29 PDT 2008

Jens Stroebel wrote:
> 		Hi.
> While trying to take a look at the current state of affairs in git HEAD, 
> I got:
> Error: couldn't get an RGB, Double-buffered visual
> from glxgears.
> All xorg parts (libs, server, xf86-video-intel, mesa, drm) from git 
> checkout of today (2008-04-08), linux kernel
> Is this being looked into already or should I file a (mesa-) bug?
> 		greets,
> 		  jens
I have run into this problem as well. After some debug, I find that 
driConfigEqual used by both glXChooseVisual and glXChooseFBConfig have 
some problems. As Ben Gamari pointed out that driConfigEqual don't take 
care about GLX_DONT_CARE.

When called by glXChooseFBConfig, driConfigEqual will return GL_FALSE 
caused by comparing yInverted (it is not being send out by xserver, and 
default set to GLX_DONT_CARE).

When driConfigEqual is called by glXChooseVisual, it will return 
GL_FALSE caused by comparing bindToTextureRgb, bindToTextureRgba, 
bindToMipmapTexture, yInverted and bindToTextureTargets.

The first four are set to the default value GLX_DONT_CARE and 
bindToTextureTargets are set to default value 0 (I don't know why this 
different from other), because they are not being send to client by 
xserver. I think these five attributes should not be compared for 
XVisual, as they are not send to client by __glXDisp_GetVisualConfigs. 
And yInverted is also should not be used as a compare attribute, as it 
never send to client by both __glXDisp_GetVisualConfigs and DoGetFBConfigs.

So may be these attribute need sent to client from both 
__glXDisp_GetVisualConfigs and DoGetFBConfigs or we should just ignore 
them in driConfigEqual. Here is a patch to make glxinfo and glxgears 
work, but I have no idea whether it is correct.


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