[Mesa-dev] [PATCH] mesa: allow MESA_GL_VERSION_OVERRIDE to override the API type

[Jordan Justen]

On Tue, Sep 4, 2012 at 10:43 AM, Kenneth Graunke <kenneth at whitecape.org> wrote:
> On 09/01/2012 10:14 AM, Jordan Justen wrote:
>> Change the format to [MAJOR.MINOR][CORE|COMPAT]
>> For example: 3.0, CORE, COMPAT, 3.2CORE
>>
>> Signed-off-by: Jordan Justen <jordan.l.justen at intel.com>
>
> Since we aren't going to support compatibility contexts, I would just
> make MESA_GL_VERSION_OVERRIDE=3.1 force API_OPENGL_CORE.  It's simpler
> to use and less code.

OVERRIDE=3.1 causing the API to automatically change seems a little
unexpected to me.

Would we really want to tie the lack of GL>=3.1 + compatibility into
mesa in this way?

> Plus, MESA_GL_VERSION_OVERRIDE=3.2COMPAT is completely useless right
> now, as nothing supports it.  If somebody did ever want to implement
> compatibility mode (and I am strongly opposed to accepting such
> patches), they could add this then.

MESA_GL_VERSION_OVERRIDE lets you put mesa into various levels of
strange/unsupported states already. :)

I'd readily drop the 'COMPAT' part if requested, but I think it might
be useful, and seems somewhat expected when 'CORE' is added.

> There's one key semantic difference worth mentioning: previously,
> MESA_GL_VERSION_OVERRIDE made the drivers lie and advertise support for
> a particular version (even if they normally wouldn't).  Now, I think
> you're trying to change it so setting MESA_GL_VERSION_OVERRIDE=3.2CORE
> makes it actually /give you/ a 3.2 core context.  That seems useful, and
> I agree with the change, I just wanted to point it out.

With various ctx->Version checks in the code, the runtime behaviour of
the driver can be altered in various ways when
MESA_GL_VERSION_OVERRIDE is used today. This doesn't seem like much of
a departure from that.

-Jordan