[Mesa-dev] [PATCH] pkgconfig: Fix gl.pc when glvnd is enabled

[Kyle Brenneman]

On 06/15/2018 10:46 AM, Dylan Baker wrote:
> Quoting Kyle Brenneman (2018-05-30 06:18:27)
>> On 05/29/2018 12:04 PM, Adam Jackson wrote:
>>> On Tue, 2018-05-29 at 09:54 -0700, Dylan Baker wrote:
>>>> Quoting Adam Jackson (2018-05-29 06:50:46)
>>>>> GL_LIB expands to GLX_mesa, but applications should not link against
>>>>> that. -lGL is never wrong, just hardcode it.
>>>> Actually.... There is this really stupid option in the autotools build called
>>>> --gl-lib-name. We should remove that.
>>>>
>>>> Emil and I had also discussed that glvnd should provide the gl.pc file when used
>>>> instead of mesa. It appears he never got around to that, but it seems like a
>>>> useful thing to do.
>>> https://github.com/NVIDIA/libglvnd/pull/86
>>>
>>> Branch is a bit stale but better than reinventing everything.
>>>
>>> Part of the reason I didn't get much further on that is the question of
>>> distributing the _headers_. It would be a bit awkward if glvnd provided
>>> the library you link to but not the headers defining its interface -
>>> though, I guess no more awkward than the current situation. At any rate
>>> glvnd doesn't install any, and there's no way to generate <GL/gl.h>
>>> from the Khronos scripts at the moment (it's assumed to be a platform
>>> implementation detail, and the version in Mesa is just handcoded
>>> history).
>>>
>>> - ajax
>>>
>> Yeah, the headers versus libraries question is what makes it awkward.
>> Libglvnd provides the libraries that an application links against, but
>> the header files are basically from the Khronos repository. Treating
>> libglvnd as the source for the libraries and the Khronos tree as the
>> source for the headers would seem to be the cleanest option, but the
>> pkg-config files would have to include the paths to both.
>>
>> Now that I think about it, though, since the Khronos registry is on
>> Github now instead of SVN, maybe a git submodule would work?
>>
>> -Kyle
>>
> Could we make a package for the headers separate from glvnd or mesa, with it's
> own pkg-config (basically just a fork with a pkg-config)? Then mesa and glvnd
> could rely on that package? Or maybe Khronos would be willing to accept something
> upstream?
>
> I don't know what the feasibility of either is, I'm just throwing out ideas.
>
> Dylan
>
The Khronos repository basically is a package for the headers. The 
challenge is that the pkg-config file has to specify an include path and 
a library path. The include path depends on where you put the header 
files (which are in the Khronos repository), but library path depends on 
how you configure libglvnd.

The libglvnd tree probably does make the most sense: That's where the 
libraries are from, and so it should be the only thing you need to build 
and link an OpenGL application. It also has a copy of the GL header 
files that it uses to build. It could install those copies, but the 
challenge then is keeping libglvnd's copy of the header files up to date.

-Kyle