Nix desktop shortcuts in dom0

[ma...@lamarciana.com]

Hi,

This question is regarding a debian-8 standalone VM, but I guess it would be the same for template VMs.

I have installed [Nix](http://nixos.org/nix/) package manager. With it, I have installed latest firefox release. Then, I wanted the shortcut icon to nix installed firefox to appear in dom0 desktop. Reading [Managing shortcuts to applications in AppVMs](https://www.qubes-os.org/doc/managing-appvm-shortcuts/) and with some investigation I have achieve it. Here are the steps I have followed:

- I created a symlink to `/home/user/.nix-profile/share/applications/firefox.desktop` in `/user/share/applications`
- I run `qvm-sync-appmenus MyVM` from dom0
- I added new available shortcut

Then, I see I could do that for every GUI application I install from nix. But, is there any way to make `qvm-sync-appmenus` also read from `/home/user/.nix-profile/share/applications/`? Or should I investigate from the Nix side how to automatically create symlinks to `/usr/share/applications`?

Thanks

[J. Eppler]

Hello,

I would do the following:

> should I investigate from the Nix side how to automatically create symlinks to `/usr/share/applications`?

in the other case you would have to modify `qvm-sync-appmenus`, which is implemented in python.

However, I think for a single VM it is easier to go with the symlink solution.

[ma...@lamarciana.com]

> Hello,
>
> I would do the following:
>
> > should I investigate from the Nix side how to automatically create symlinks to `/usr/share/applications`?

Thaks for your answer. I'm trying with it, but without luck for now :) :

http://unix.stackexchange.com/questions/310666/nix-desktop-files

[ma...@lamarciana.com]

Hi. Finally I get some light from the other side :)

It seems that freedesktop Desktop Menu Specification defines an environment variable which should contain a path with all directories with .desktop files:

https://specifications.freedesktop.org/menu-spec/menu-spec-latest.html#paths

$XDG_DATA_DIRS/applications/

This directory contains a .desktop file for each possible menu item. Each directory in the $XDG_DATA_DIRS search path should be used (i.e. desktop entries are collected from all of them, not just the first one that exists). When two desktop entries have the same name, the one appearing earlier in the path is used.

The <DefaultAppDirs> element in a menu file indicates that this default list of desktop entry locations should be scanned at that point. If a menu file does not contain <DefaultAppDirs>, then these locations are not scanned.

I have looked at `qvm-sync-appmenus` and I don't see it reading that variable. Can anyone confirm this point?

Thanks

[Marek Marczykowski-Górecki]

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Yes, I can confirm:

[user@testvm ~]$ cat /etc/qubes-rpc/qubes.GetAppmenus
find /usr/share/applications/ /usr/local/share/applications/ -name '*.desktop' -print0 2>/dev/null | \
xargs -0 awk '
BEGINFILE { entry="" }
/^\[/ { if (tolower($0) != "\[desktop entry\]") nextfile }
/^Exec=/ { entry = entry FILENAME ":Exec=qubes-desktop-run " FILENAME "\n"; next }
/^NoDisplay *= *true$/ { entry=""; nextfile }
/=/ { entry = entry FILENAME ":" $0 "\n" }
ENDFILE { print entry }
' 2> /dev/null

It uses /usr/share/applications/ /usr/local/share/applications/
directly.

Does Nix set $XDG_DATA_DIRS?

- --
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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[Marc Busqué]

> It uses /usr/share/applications/ /usr/local/share/applications/
> directly.
>
> Does Nix set $XDG_DATA_DIRS?

I think it doesn't. At least, it didn't set it during my installation.
But it could be set manually.

Furthermore, I don't see this variable set in debian and template VMs. I
don't have "canonical" fedora/debian machines to test it there. If it is
set there, I think qubes should follow the convention. But then, that
variable should also be set in debian/fedora VMs.

What do you think?


Marc Busqué
http://waiting-for-dev.github.io/about/

[Marek Marczykowski-Górecki]

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On Fri, Sep 23, 2016 at 04:53:10PM +0200, Marc Busqué wrote:
> > It uses /usr/share/applications/ /usr/local/share/applications/
> > directly.
> >
> > Does Nix set $XDG_DATA_DIRS?
>
> I think it doesn't. At least, it didn't set it during my installation.
> But it could be set manually.

If it doesn't, supporting XDG_DATA_DIRS would not help with Nix.

Current implementation simply assume default value, according to
spec[1]:

If $XDG_DATA_DIRS is either not set or empty, a value equal to
/usr/local/share/:/usr/share/ should be used.

[1]
https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html

- --
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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[Marc Busqué]

> If it doesn't, supporting XDG_DATA_DIRS would not help with Nix.

But couldn't I set it manually? Then Qubes should read from it that change is introduced.