[Piglit] Issue with Piglit pixel ownership assumptions

Alexander Goins agoins at nvidia.com
Thu Aug 13 10:51:02 PDT 2015

Sorry – at the time I was unable to get git send-email working with NVIDIA’s mail server. It’s fine now.

I resent the patch with the subject ‘[PATCH] winsys-framework Default to showing window’ using git send-email.


From: ibmirkin at gmail.com [mailto:ibmirkin at gmail.com] On Behalf Of Ilia Mirkin
Sent: Wednesday, August 12, 2015 8:56 PM
To: James Jones
Cc: Alexander Goins; piglit at lists.freedesktop.org
Subject: Re: [Piglit] Issue with Piglit pixel ownership assumptions

Unfortunately the patches were attached, which greatly increases the effort required to review. Could you send this out inline using git send-email or equivalent mechanism?
On Aug 12, 2015 8:54 PM, "James Jones" <jajones at nvidia.com<mailto:jajones at nvidia.com>> wrote:
The PIGLIT_NO_WINDOW patch seems like the way to go to me, since defaulting to unreliable behavior seems bad, but allowing users to fall back to it to test on drivers that don't enforce pixel ownership seems fine.  I'd prefer if someone outside NVIDIA could review as well, but for:


Reviewed-by: James Jones <jajones at nvidia.com<mailto:jajones at nvidia.com>>

I'll commit this soon if no one objects.


On 07/20/2015 02:44 PM, Alexander Goins wrote:
Hello all,

During some recent debugging, I seem to have discovered  an issue with
Piglit that could cause problems with some drivers. With -auto, and
without -fbo or PIGLIT_FORCE_WINDOW=1, Piglit defaults to rendering to
the default framebuffer without mapping a window. This means that it
doesn't take pixel ownership, which could cause a problem with some
drivers, particularly NVIDIA's with Unified Back Buffer enabled. The
OpenGL spec requires that pixel ownership be established in order to
guarantee that the window system doesn't clobber the output. There are
more details in the patch descriptions.

It would probably be best to deprecate the functionality of not showing
a window altogether, making users use FBOs if they want offscreen
rendering. I made a patch that simply removes that functionality. As a
softer solution, however, I also made a patch that makes displaying the
window the default, and replaced PIGLIT_FORCE_WINDOW with
PIGLIT_NO_WINDOW, a flag that allows tests to run without mapping a
window. This way, users that have been relying on the existing
functionality can continue using it.

Both patches are included.


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