[Mesa-dev] [PATCH 2/2] mesa: use the EXT_texture_compression_s3tc enable flag for all S3TC extensions

Eric Anholt eric at anholt.net
Mon Oct 29 11:41:00 PDT 2012

Philipp Klaus Krause <pkk at spth.de> writes:

> Am 28.10.2012 20:51, schrieb Kenneth Graunke:
>> This makes sense to me.  The original reason for splitting out the ANGLE
>> vs. EXT bits was that the ANGLE extension only requires decompression,
>> while the other two require both compression and decompression.  So that
>> one could be advertised even without libtxc_dxtn.
>> Of course, now that we've decided to simply lie and fall back to
>> GL_COMPRESSED_RGB[A] when the user asks for online compression and we
>> don't have libtxc_dxtn, this isn't a problem.  So we can simplify.
> I can see how one wants to lie about EXT_texture_compression_s3tc and
> give users a broken GL by default, since that's what they want. AFAIK
> previously it was a driconf option, but enabling it was too much of a
> burden on the user.
> Still there might be some users that want standard-compliant behaviour
> without having libtxc_dxtn installed. Why not give them a driconf option
> they can use to disable EXT_texture_compression_s3tc when libtxc_dxtn is
> not there?

We used to have a more-strict-correctness flag like that in the intel
driver for other cases of strict correctness.  It turned out that users
actually didn't want it, and it was a trap for QA which would say "ooh,
more correctness, we should be testing that code instead, right?" and
thus not test the code that shipped.  So I deleted it.
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