[Mesa-dev] MESA_EXTENSION_OVERRIDE problem

[Ilia Mirkin]

On Thu, Nov 19, 2015 at 3:25 PM, Brian Paul <brianp at vmware.com> wrote:
> On 11/19/2015 01:19 PM, Ilia Mirkin wrote:
>>
>> On Thu, Nov 19, 2015 at 3:13 PM, Brian Paul <brianp at vmware.com> wrote:
>>>
>>> Hi Nanley,
>>>
>>> Maybe you can fix an issue I have with the new extension code.
>>>
>>> Previously, I could do something like export
>>> MESA_EXTENSION_OVERRIDE="-ARB_clear_buffer_object" and I would no longer
>>> see
>>> it in the GL_EXTENSIONS string, even if it was an "always on" extension.
>>
>>
>> How sure are you that this worked?
>
>
> I'm pretty sure it worked that way when I first wrote it.
>
>
>> AFAIK there was no way to
>> enable/disable an always-on ext.
>
>
> That's not the point.  The point is to change what
> glGetString(GL_EXTENSIONS) (or the glGetStringi() method) returns to the
> application.  I don't care if the underlying functionality is still working
> in Mesa.  We're trying to tell the application to not use a feature.  I've
> found this extremely helpful when debugging some apps.
>
>
>> That env var never affected the
>> extension strings, but only the actual ctx->Extensions struct, which
>> would indirectly modify the ext string. If the entry in that ext table
>> was a dummy one, it had logic to not futz with it. (But it did so
>> silently.)
>
>
> Yeah, I don't care about the table.  I only care about the return value of
> glGetString(GL_EXTENSIONS).

I was pretty annoyed at that too -- having it affect exts returned by
the driver seemed to be the important bit, but I think I investigated
why it didn't work ~6 months ago, and came to the above conclusion
[that it only futzed with the table]. In fact recently someone was
unable to work around an ARB_dsa shortcoming in nouveau by disabling
it with an override.

IMHO it makes sense for it to affect both the table and the ext
string... i.e. if there's a ctx->Extensions.foo listed, it should turn
that on/off, but if there isn't, it should still touch up the returned
ext list.

  -ilia