Arch Linux

how do you want to use this backend without having libva? since the library loads the backend,

Your argument is like saying "libva depends on mplayer. otherwise how would you use libva?" or "the knife depends on the bread". Also if the library loads the backend, then the library should (opt)depend on the backend, not the other way around.

Or perhaps I'm day dreaming ?
-Emil

Glad to see that I'm not dreaming (this time) - libreoffice-common & libreoffice-langpack is a nice example of what I have in mind. On the other hand firefox and it's language packs follow the libva/libva-vdpau-driver (which I believe is) incorrect behaviour.

Perhaps there isn't an common ground amongst Arch developers on the topic. IMHO the libreoffice is the preferred approach but if you feel against it I would not object :)

Cheers
-Emil

Language packs aren't really a good example of that. libreoffice-common require at least one language pack and we decided it will be en-US langpack packaged from the main tarball (libreoffice-fresh includes en-US as well). It makes other languages completely optional. In the same manner libva-vdpau-driver is useless without libva, because the former doesn't provide its own libva library.

OK the language pack was not the best example.
How about
- phonon-qt4
Requires: phonon-qt4-backend
Provided by: phonon-qt4-vlc/phonon-qt4-gstreamer

or perhaps
- apitrace,mpv,sdl2,dosbox...
Requires: libgl
Provided by: mesa-libgl/nvidia-libgl

Afaict the following approach will preserve the sanity check and addresses my concerns.

package: libva
depends: libva-backend

package: libva-vdpau-driver
provides: libva-backend

Cheers,
Emil

Guys does any of the above make sense, or am I (un)officially in the ignore list :)

From the linking side it seems correct to drop the dep. But how do you get the loader installed when you only install the certain backend and there's no dependency
on the loader lib? That way the dependency seems fine to me here.

That's simple imho:
You know that application/package X has optional support for VAAPI as the said package already has it listed. Thus one should really be installing the actual dependency - libva.

Afaict some packages in Arch follow this approach while others, go in the inverse direction. IMHO the former provides clearer link between the components, while the latter is somewhat confusing from dependency POV.

Although yes, I have to agree with you - proposed solution might be a bit picky, depending on one's current state of mind. Ideally we'll have something like the Debian's "Suggests" tag/section, where the backend will list the frontend/loader.

What do you think, does it make sense ?

Can we get this fixed please? Logic and all examples are correct to this date.

Humble ping?

I can prepare some patches if people prefer.

Finally going through my backlog. The libva-mesa-driver package already does that, so I don't see why not. Just pushed a new package.