@primeos, thanks for your PR! By analyzing the history of the files in this pull request, we identified @edolstra, @nbp and @vcunat to be potential reviewers.

This does not fix the problem with sddm. I actually find the current display-manager script too complex and would actually prefer to have a script per desktop file instead of relying on shell scripts parsing.

@Mic92 Are you running NixOS 17.03? On nixos-unstable it seems like the xsession script doesn't actually get any parameters (at least that's the case on both of my GUI systems...).

I actually find the current display-manager script too complex

Agreed 😄

would actually prefer to have a script per desktop file instead of relying on shell scripts parsing.

I'd rather improve the documentation/comments and refactor the code. Normally I would expect that the xsession script is getting called like this: /nix/store/XXX-xsession none\ +\ i3 which shouldn't be that problematic to parse ($1=none\ +\ i3 or $2, if $0=$1 which seems to be the case).

Here is what I get:

Apr 25 20:56:15 turingmachine xsession[29898]: first: none
Apr 25 20:56:15 turingmachine xsession[29898]: second: +
Apr 25 20:56:15 turingmachine xsession[29898]: third: awesome
Apr 25 20:56:15 turingmachine xsession[29898]: forth:
Apr 25 20:56:15 turingmachine xsession[29898]: fifth:
Apr 25 20:56:15 turingmachine xsession[29898]: first: none
Apr 25 20:56:15 turingmachine xsession[29898]: second:
Apr 25 20:56:15 turingmachine xsession[29898]: third:
Apr 25 20:56:15 turingmachine xsession[29898]: forth:
Apr 25 20:56:15 turingmachine xsession[29898]: fifth:
Apr 25 20:56:15 turingmachine xsession[29898]: 28

I added the following:

  # Handle being called by SDDM.
   if test "''${1:0:1}" = / ; then eval exec $1 $2 ; fi
+ echo "first: $1"
+ echo "second: $2"
+ echo "third: $3"
+ echo "forth: $4"
+ echo "fifth: $5"

it is rexeced twice. It may work for you because you are using a desktop manager rather then a window manager.

It may work for you because you are using a desktop manager rather then a window manager.

It actually doesn't but looking at the specification I hoped it would. I expected that $1 would contain "DM + WM" but the specifications unfortunately doesn't say if the double quotes actually escape the spaces... :o This actually fixes lightdm but breaks slim and sddm. The current situation seems to be horribly broken -> I'll update this PR and change " + " to "+" (no spaces). This should fix everything for sddm and lightdm but will most likely break slim (I'll add a workaround if it doesn't work).

This should fix "everything". I'll run some final tests and merge this in ~1-2h. If it doesn't cause any problems on nixos-unstable (I'll wait 1-2 weeks) I'll test this on 17.03 and backport it to stable if it doesn't cause any problems.

Let's hope that this doesn't break anything :D
But it should be pretty save (tested with all login/display managers) and after I realized that it's a bad Idea to assume that stderr output won't be redirected to /dev/null everything made sense again (that's also why it looked like SDDM wasn't providing any parameters).

Backported to 17.03 (c893d7a and 9283310) and tested with SDDM, LightDM and SLiM.