feat: add flake

[lovesegfault]

This adds a simple flake to the repo with the nixGLIntel and nixVulkanIntel packages, since they are the only one that evaluate purely.

It also exposes an overlay which just adds the nixgl attr to pkgs.

[SuperSandro2000]

I would be for just adding everything even if it does not eval purely.

[lovesegfault]

We could also just remove the packages portion altogether and make the flake only export the overlay, which IMHO is already a huge usability win for those using flakes.

[lovesegfault]

I would be for just adding everything even if it does not eval purely.

Doesn't work since it causes even basic flake commands (e.g. flake metadata) to fail

[guibou]

Exposing the overlay is great because it will force the upstream user to use the same nixpkgs for both their project and nixGL (which will ensures compatibility).

"pure" packages can still be exposed for convenience, but we need to document that the user must make nixgl inputs.nixpkgs "follows" their own nixpkgs.

[lovesegfault]

So, I thought about this more and IMHO only exposing some packages is more confusing than exposing none, and since we already expose the overlay the package is kind of pointless.

So I refactored this to make a flake that just exposes the overlay, which should be good enough, and also means we have no flake inputs :)

[guibou]

Just for my knowledge, is there a reason to exposes the overlay instead of just exposing the nixGL.nix file. Then user can decide if they want to callPackage on it directly, or use it in an overlay? That's just a naive question, we can merge without that.

However, could you please add a line in the readme about flake usage?

[lovesegfault]

Just for my knowledge, is there a reason to exposes the overlay instead of just exposing the nixGL.nix file. Then user can decide if they want to callPackage on it directly, or use it in an overlay? That's just a naive question, we can merge without that.

It's just more of a hassle to do that, as-is the user can still control the callPackage by calling .override on pkgs.nixgl.

It boils down to flakes having a predetermined set of valid outputs (overlay, packages, lib, defaultPackage, modules, ...) and "thing you need to callPackage on to use" not really fitting neatly into any of them IMHO.

Probably the thing we wanted was to expose all the nixgl attrs as flake packages, but the purity issue makes that impossible.

However, could you please add a line in the readme about flake usage?

Done :)

[lovesegfault]

@guibou Friendly merge ping, anything else I need to do? :)

[guibou]

Friendly merge ;) @lovesegfault Thank you!