[Mesa-dev] [PATCH] [rfc] mesa: don't allow GLSL 1.30 without GL3.

[Eric Anholt]

On Fri, 20 Jan 2012 11:06:56 +0000, Dave Airlie <airlied at gmail.com> wrote:
> On Wed, Jan 11, 2012 at 5:40 PM, Paul Berry <stereotype441 at gmail.com> wrote:
> > On 10 January 2012 13:38, Christoph Bumiller <e0425955 at student.tuwien.ac.at>
> > wrote:
> >>
> >> On 01/10/2012 10:09 PM, Dave Airlie wrote:
> >> > On Tue, Jan 10, 2012 at 7:28 PM, Eric Anholt <eric at anholt.net> wrote:
> >> >> On Tue, 10 Jan 2012 11:52:57 +0000, Dave Airlie <airlied at gmail.com>
> >> >> wrote:
> >> >>> From: Dave Airlie <airlied at redhat.com>
> >> >>>
> >> >>> Things can get confused if you expose one without the other which can
> >> >>> happen
> >> >>> if you are missing one or two of the extensions (like say float
> >> >>> textures).
> >> >>
> >> >> Can you clarify what "things can get confused" means?
> >> >
> >> > Well piglit starts to fail in wierd and wonderful way, I just don't
> >> > think we have any valid use cases for exposing GLSL1.30 without GL3
> >> > and I'd like to enforce that.
> >> >
> >>
> >> Some tests only check for GLSL 1.3 and then use functions like
> >> glUniform*ui that glew only sets up if GL_VERSION_3_0 and as a result
> >> they call a NULL pointer.
> >
> >
> > Personally I would call this a flaw in the piglit tests.  If sloppy
> > dependency checking in piglit tests is our only reason for making this
> > change, then I'd rather fix the piglit tests rather than constrain what GLSL
> > version Mesa can advertise.  It was really useful for us in our GL 3.0 work
> > on Sandy Bridge to be able to enable GLSL 1.30 support when it was ready,
> > and not have to wait until we had all the components of GL 3.0 in place
> > before we could start testing the GLSL 1.30 features.
> 
> At a guess you guys used version overrides, so I can't see how this
> constraint would stop it being really useful.
> 
> The thing is no application in existance is expected GL2.1 + GLSL
> 1.30, like what features of GLSL1.30 would a GL2 targeted app use? and
> the fact that our own test suite chokes on it should show this.

Actually, I've been surprised to find over the course of my benchmarking
recently that apps *do* use 1.30 features, successfully, based on only
the presence of GLSL 1.30.  An example is nexuiz:

MESA_GL_VERSION_OVERRIDE=2.1 INTEL_DEBUG=wm mesagl nexuizd |& grep txd

shows it using derivatives.

MESA_GLSL_VERSION_OVERRIDE=120 MESA_GL_VERSION_OVERRIDE=2.1 INTEL_DEBUG=wm mesagl nexuizd |& grep txd

does not.
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