Bug 34265

Summary: GLX fbconfigs without visuals erroneously set window and pixmap bits
Product: xorg Reporter: Ian Romanick <idr>
Component: Server/Ext/GLXAssignee: Adam Jackson <ajax>
Status: RESOLVED FIXED QA Contact: Xorg Project Team <xorg-team>
Severity: normal    
Priority: medium CC: krh
Version: unspecified   
Hardware: All   
OS: All   
Whiteboard: 2011BRB_Reviewed
i915 platform: i915 features:

Description Ian Romanick 2011-02-14 10:00:56 UTC 
A recently updated version of glxinfo shows the following output with the -v option:

48 GLXFBConfigs:
FBConfig ID: 6d  Visual ID=0  depth=0  class=TrueColor, type=window,pixmap,pbuffer
    bufferSize=16 level=0 renderType=rgba doubleBuffer=0 stereo=0
    rgba: redSize=5 greenSize=6 blueSize=5 alphaSize=0 float=N sRGB=N
    auxBuffers=0 depthSize=0 stencilSize=0
    accum: redSize=0 greenSize=0 blueSize=0 alphaSize=0
    multiSample=0  multiSampleBuffers=0
    visualCaveat=None
    Opaque.
FBConfig ID: 73  Visual ID=9d  depth=24  class=TrueColor, type=window,pixmap,pbuffer
    bufferSize=24 level=0 renderType=rgba doubleBuffer=0 stereo=0
    rgba: redSize=8 greenSize=8 blueSize=8 alphaSize=0 float=N sRGB=N
    auxBuffers=0 depthSize=0 stencilSize=0
    accum: redSize=0 greenSize=0 blueSize=0 alphaSize=0
    multiSample=0  multiSampleBuffers=0
    visualCaveat=None
    Opaque.

Note that the fbconfig with an associated visual ID of 0 says that it can be used to create a window, a pixmap, or a pbuffer.  While this may technically be legal (I see nothing in the GLX spec that strictly forbids it), it is utter nonsense.  It is possible to have an fbconfig that has a visual ID of 0 that may be compatible with some other visual.  However, no driver supported by xorg does this.

We should filter the window bit and the pixmap bit on fbconfigs that lack a visual.
Comment 1 Ian Romanick 2011-03-25 17:24:47 UTC 
The piglit test glx-fbconfig-sanity reproduces this issue.
Comment 2 Adam Jackson 2014-04-10 15:36:09 UTC 
Pretty sure this was fixed in:

commit 3e8270b869ebf788778d5d56107f6d47c7c050d0
Author: Adam Jackson <ajax@redhat.com>
Date:   Tue Apr 12 15:30:25 2011 -0400

    glx: Fix fbconfigs with no corresponding visual

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