[Nix-dev] Discussion: env vars as glue

[Lluís Batlle i Rossell]

On Mon, Apr 15, 2013 at 11:07:16PM +0300, phreedom at yandex.ru wrote:
> On Понедельник 15 апреля 2013 21:40:08 Lluís Batlle i Rossell wrote:
> > On Mon, Apr 15, 2013 at 10:17:23PM +0300, phreedom at yandex.ru wrote:
> > > On Понедельник 15 апреля 2013 18:59:52 Lluís Batlle i Rossell wrote:
> > > > What uses do you have for:
> > > > ALSA_PLUGIN_DIRS
> > > 
> > > This is used for LADSPA plugins(various sound processing apps) and for
> > > input/output plugins(eg by pulseaudio).
> > 
> > Ok, now, can we make this a nixos-only option? Containing only a path
> > prepared by nixos. People who want LADSPAT plugins, set them up with nixos.
> 
> ALSA_PLUGIN_DIRS is a nixpkgs patch (at least used to be). So installing 
> plugins via nix for non-nix-installed apps is impossible. Otherwise, it's a 
> quite useful feature to quickly install another sound effect.

I don't mean removing the patch. I mean it not pointing to user profiles, only
to the system profile, by default.

> > > > GST_PLUGIN_PATH
> > > 
> > > Gstreamer plugins which do all the work. Apparently these are loaded
> > > dynamically. Typical case: kde app plays media via phonon, which uses
> > > phonon_backend_gstreamer to do the actual processing.
> > 
> > Don't people usually set this up in nixos, instead of the user profiles?
> > What kind of plugins people install with nix-env?
> 
> Currently KDE in nixos pulls all available GST plugins. A KDE app installed 
> via nix-env still needs this var to access the plugins.

As above, it'd be fine for me if the variable didn't include the user profiles
by default.

> > > > QTWEBKIT_PLUGIN_PATH
> > > 
> > > Apparently, this helps webkit steal mozilla's extensions.  Likely any
> > > kde app which is a browser or can use KParts(such as akregator) would
> > > want this set.
> > Maybe this can be set easily up to work with a wrapper like firefox? What
> > kind of browsers would use that? If only konqueror, maybe that can be
> > handled by nixos instead.
> 
> konqueror, rekonq, akregator, pretty much everything else which might display 
> a web page in KDE.

So, can this be set up to point only to the system profile?
> 
> > > You managed to overlook the innocently-looking KDEDIRS. On a typical KDE
> > > install this place contains 1k+ libs. Among these are KIPI plugins
> > > shared by at least gwenview, krita and digikam, Kparts plugins which
> > > are at least shared by konqueror and akregator and are always installed
> > > by the app supplying the part.... While KDE usually requires ABI
> > > compatibility in such cases, it doesn't help client apps  compiled
> > > against newer version.
> > 
> > Right, KDEDIRS! :)
> > 
> > Don't most KDE programs require being set up by nixos anyway? Or this
> > KDEDIRS was an addition towards allowing the install of extra KDE programs
> > in profiles? This does not help much installing KDE programs without KDE in
> > NixOS, in any case.
> 
> Yes, same as always: a quick install of a missing app, development of an app.  
> KDE setup in nixos consists of setting the vars and installing several core 
> packages. Could be done by hand if necessary. Concurrently running KDE apps 
> linked against substantially different KDE versions may be a bad idea though 
> even if frameworks troubles are sorted out.

Maybe then a user could at will change those variables, if he is "hacking
something" (to label that not very supported situation), pointing them into his
profiles.

What do you think?