XDG standard desktop entries - desktop-file-utils and gtk, and KDE: mechanism of desktop database generation in profiles

[Danny Milosavljevic]

>If a software component comes with desktop files, what's the right place to 
>put them relative to the component's output path?

share/applications

> I think we're doing this already for some Guix packages, but since my
> knowledge of the FreeDesktop standard is limited, I'm not sure if it's
> by accident or if it's intentional.

It's intentional.  I'm actively filing bugs and fixing them if GUI programs 
don't have a desktop file - because that's just silly, having a program you 
can't (easily) run.

See guix/profiles.scm xdg-desktop-database for the profile hook that merges all 
the share/applications directories of the packages in the profile.
For the hook to be run, desktop-file-utils (of freedesktop) has to be an input 
of the package or some of its dependencies (i.e. it has to be available on the 
build side in the environment).

I think we should just make desktop-file-utils a propagated-input of gtk.

(In fact, even gio (part of glib) already supports desktop files: 
https://developer.gnome.org/gio/stable/gio-Desktop-file-based-GAppInfo.html . 
However, there are lots of non-GUI programs using glib.  For example, 
desktop-file-utils uses glib)

Disclaimer: I have no idea how KDE works - but desktop-file-utils seems to be 
missing entirely there.  Qt doesn't require it either.  Weird.

Similar stuff is done if GLIB is a dependency of a package, for 
xdg-mime-database.