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

[Marek Olšák]

On Mon, Oct 29, 2012 at 7:36 PM, Ian Romanick <idr at freedesktop.org> wrote:
> On 10/29/2012 02:47 AM, Philipp Klaus Krause wrote:
>>
>> 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?
>
>
> I got some push-back from an ISV for this reason about my "Enable S3TC
> always" patch.  They want to know if on-line compression is actually
> available.  I think the right way to do that is to expose all of the
> extensions except EXT_texture_compression_s3tc.
>
> Perhaps there should be two flags:
>
> - One for EXT_texture_compression_s3tc
>
> - One for EXT_texture_compression_dxt1, ANGLE_texture_compression_dxt*, and
> S3_s3tc.
>
> This is similar the current situation, but the partitioning is different.

Yeah. However as far as I know, the desktop GL doesn't have a (good)
S3TC extension which doesn't require on-line compression. With what
you say, it looks like such an extension would be useful for us. Don't
you think it would be nice if the OpenGL ARB went ahead and created
such an extension? :)

Marek