RE: [Caml-list] LablGtk3 beta1

[David Allsopp <dra-news@metastack.com>]

Emilio Jesús Gallego Arias wrote:
> Jacques Garrigue <garrigue@math.nagoya-u.ac.jp> writes:
> 
> > Emilio, I do agree with you on that.
> 
> > I added a conf-gtk3 as was suggested to me, and since lablgtk3
> > requires gtk 3.18, if dependes on a versioned package conf-gtk3.18
> > (i.e. cong-gtk3 ">= 18”) However, if somebody else introduces a
> > conf-gtk3.22 version, that one will be installed by default (even for
> > lablgtk3), and fail if one gtk-3.18 is available, so this does not
> > seem to be the right solution for versioning, and I see no other way to
> do it with the current opam.
> 
> Indeed, IMVHO lablgtk should follow the packaging structure hinted at
> https://github.com/garrigue/lablgtk/pull/14 and don't depend on `conf-
> gtk`.
> 
> This would have the important additional benefit of allowing fully
> automatic OPAM releases, which are trickier to do when the conf-foo
> package is there.

If I may, there seems to be a little bit of "throwing the baby out with the bath water" where the conf- packages are concerned. It's also worth remembering that the layout of a package in opam-repository is the concern of opam-repository's maintainers (I'm not one, btw), not necessarily packagers.

At present, it is indeed not possible in opam to depend on the versions of system packages (with the exception of OCaml). The only way, without new support, is to mirror all the releases - as is done for the ocaml package - but that's likely to be a real PITA to maintain, and overkill.

However, the conf package remains the only place in which the depext information (i.e. OS-dependent packages) should be. Anything else involves duplication and so is fundamentally not a better solution.

I do have one question, as I know comparatively little about distributions of GTK itself - if on any system I request gtk3 and I get, say, gtk 3.17 then on most systems, what would I need to do to get gtk 3.18? Is it easy? For example, if I'm on Ubuntu 16.04 and I want gtk3 3.20, it looks quite tricky to achieve that, I think?

If it's the case that the user is most likely stuck with the version on their system and cannot easily change it, then it looks to me as though this should really have been conf-gtk3.0 which simply installs whatever is available (no minimum version check) and then the lablgtk packages should check the version and fail their *build* if the version isn't recent enough.

The other option is still to have conf-gtk3.0 do whatever is necessary to install gtk3 on the system and then have an entirely separate conf-gtk318 package which encodes the ">= 3.18" check - that has the benefit of centralising OS-specific version probing. You would then add an entirely separate conf-gtk322 package if someone else needed the ">= 3.22" check. That's not terribly elegant or scalable, but would be a reasonable workaround for the few specific packages where this matters, prior to opam being able to include dependency on available versions of system packages.


David

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