Shepherd environment question

Shepherd environment question

[Fredrik Salomonsson]

Hi Guix,

After reading the Shepherd 1.0.0 blog post [0], it got me thinking that
with the log rotation etc it would be nice to let shepherd handle sway
and the programs it launches.

As right now I got a simple line in my ~/.bash_profile that if logging
in to tty1 exec sway.  And all the output from sway and its program just
outputs into the ether.

So I migrated all the programs that sway launches from the config to
shepherd services.  And made a shepherd service for sway but disable the
auto-start for it.  So that I can kick it off with my .bash_profile:

Sway launches fine when I login, and I can now see some logs when
checking the status: 

```
herd status sway
● Status of sway:
  It is running since 18:45:58 (27 seconds ago).
  Main PID: 1100
  Command: /gnu/store/c990qdj2nqcgfif7qs2gnyfbshskkp4y-sway-1.10/bin/sway
  It is enabled.
  Provides: sway
  Will be respawned.
  Log file: /home/plattfot/.local/state/log/sway.log

Recent messages (use '-n' to view more or less):
  2025-01-05 18:46:15 (process:1425): GLib-CRITICAL **: 18:46:15.714: g_string_insert_len: assertion 'len == 0 || val != NULL' failed
  2025-01-05 18:46:15 00:00:16.666 [ERROR] [wlr] [xwayland/xwm.c:1500] Unhandled message 'new: ID=rofi/|gnu|store|9z44nwi28zvw3cay7m9q6388b26d74kd-emacs-pgtk-29.4|bin|emacs/1425-0-surt_TIME43379 SCREEN=0 NAME=Emacs DESCRIPTION=Launching\ '/gnu/store/9z44nwi28zvw3cay7m9q6388b26d74kd-emacs-pgtk-29.4/bin/emacs'\ via\ rofi WMCLASS=Emacs BIN=/gnu/store/9z44nwi28zvw3cay7m9q6388b26d74kd-emacs-pgtk-29.4/bin/emacs ICON=emacs APPLICATION_ID=emacs'
  2025-01-05 18:46:15 
  2025-01-05 18:46:15 00:00:16.666 [ERROR] [wlr] [xwayland/xwm.c:1633] xcb error: op ChangeWindowAttributes (no minor), code Window (no extension), sequence 173, value 4194320
  2025-01-05 18:46:21 warn: wayland.c:1619: compositor does not implement the XDG toplevel icon protocol

```

Pretty cool! 🤓

However, the programs that requires a running wayland session did not
go that well — for example mako and swayidle.  Here is a line from the
swayidle log:

```
2025-01-05 18:29:34 2025-01-05 18:29:34 - [Line 1096] Unable to connect to the compositor. If your compositor is running, check or set the WAYLAND_DISPLAY environment variable.
```

What I think I need to do to run them properly, is to run them in the
environment sway creates.  The `make-forkexec-constructor` does have a
`#:environment-variables` argument so I need to somehow extract the
environment variables required from the sway service and feed that into
the constructor for the services that require a wayland session.  Anyone
have any idea how to set that up?  Or am I going about this the wrong way?

Thanks!

Here is what I got so far:

~/.bash_profile
```
# Start sway when logging in on tty
if [ "$(tty)" = "/dev/tty1" ]; then
  herd start sway
fi

```

My sway shepherd services:
```
(define-configuration/no-serialization plt-sway-configuration
  (turn-off-displays?
   (boolean #t)
   "Specify if it should turn off the displays when the machine is idle."))

(define (plt-sway-shepherd config)
  (list
   (shepherd-service
    (provision '(sway))
    (documentation "Start sway")
    (auto-start? #f)
    (start #~(make-forkexec-constructor
              (list (string-append #$sway "/bin/sway"))
              #:log-file (format #f "~a/log/sway.log"
                                 (getenv "XDG_STATE_HOME"))))
    (stop #~(make-kill-destructor)))
   (let ((turn-off-displays? (plt-sway-configuration-turn-off-displays? config)))
     (shepherd-service
      (requirement '(sway))
      (provision '(swayidle))
      (documentation (string-append "Lock screen after 5 min"
                                    (if turn-off-displays?
                                        "and turn them off after 10 min."
                                        ".")))
      (start #~(make-forkexec-constructor
                (append
                 (list (string-append #$swayidle "/bin/swayidle") "-w")
                 (if #$turn-off-displays?
                     '("timeout" "600" "swaymsg 'output * dpms off'"
                       "resume" "swaymsg 'output * dpms on'")
                     '())
                 (list "timeout" "300" (string-append #$swaylock "/bin/swaylock -f -c 000000")
                       "before-sleep" (string-append #$swaylock "/bin/swaylock -f -c 000000")))
             #:log-file (format #f "~a/log/swayidle.log" (getenv "XDG_STATE_HOME"))))
      (stop #~(make-kill-destructor))))
   (shepherd-service
    (provision '(waybar))
    (requirement '(sway))
    (documentation "Start waybar.")
    (start #~(make-forkexec-constructor
              (list (string-append #$waybar "/bin/waybar"))
              #:log-file (format #f "~a/log/waybar.log"
                                 (getenv "XDG_STATE_HOME"))))
    (stop #~(make-kill-destructor)))
   (shepherd-service
    (provision '(mako))
    (requirement '(sway))
    (documentation "Start mako; lightweight Wayland notification daemon.")
    (start #~(make-forkexec-constructor
              (list (string-append #$mako "/bin/mako"))
              #:log-file (format #f "~a/log/mako.log"
                                 (getenv "XDG_STATE_HOME"))))
    (stop #~(make-kill-destructor)))
   (shepherd-service
    (provision '(dbus-update-activation-environment))
    (requirement '(dbus sway))
    (documentation "Tell dbus that we are using sway")
    (one-shot? #t)
    (start #~(make-forkexec-constructor
              (list (string-append #$dbus "/bin/dbus-update-activation-environment")
                    "DISPLAY SWAYSOCK"
                    "WAYLAND_DISPLAY"
                    "XDG_CURRENT_DESKTOP=sway")
              #:log-file (format #f "~a/log/dbus-activate-environment.log"
                                 (getenv "XDG_STATE_HOME"))))
    (stop #~(make-kill-destructor)))
   (shepherd-service
    (requirement '(sway))
    (provision '(playerctld))
    (documentation "Controll the latest active player over MPRIS")
    (start #~(make-forkexec-constructor
              (list (string-append #$playerctl "/bin/playerctld"))
              #:log-file (format #f "~a/log/playerctld.log" (getenv "XDG_STATE_HOME"))))
    (stop #~(make-kill-destructor)))))
```


[0] https://guix.gnu.org/blog/2024/the-shepherd-1.0.0-released

-- 
s/Fred[re]+i[ck]+/Fredrik/g