Add support for running as a dinit service (#728)

* Added dinit services

* Added dinit support to niri-session

* Replaced shutdown script for dinit with a single command execution

* Added dinit service files to Getting Started install tables

* Fix typo in resources/dinit/niri

Co-authored-by: Ivan Molodetskikh <yalterz@gmail.com>

* Fixed mistakes in wiki/Getting-Started.md

Co-authored-by: Ivan Molodetskikh <yalterz@gmail.com>

* niri-session does not start dinit anymore

---------

Co-authored-by: Ivan Molodetskikh <yalterz@gmail.com>

resources/dinit/niri

@@ -0,0 +1,8 @@
+type              = process
+command           = niri --session
+restart           = false
+working-dir       = $HOME
+depends-on        = dbus
+after             = niri-shutdown
+chain-to          = niri-shutdown
+options:          always-chain

resources/dinit/niri-shutdown

@@ -0,0 +1,3 @@
+type               = scripted
+command            = dinitctl -u setenv WAYLAND_DISPLAY= XDG_SESSION_TYPE= XDG_CURRENT_DESKTOP= NIRI_SOCKET=
+restart            = false

resources/niri-session

@@ -11,31 +11,51 @@ if [ -n "$SHELL" ] &&
   fi
 fi
 
-# Make sure there's no already running session.
-if systemctl --user -q is-active niri.service; then
-  echo 'A niri session is already running.'
-  exit 1
+# Try to detect the service manager that is being used
+if hash systemctl &> /dev/null; then
+    # Make sure there's no already running session.
+    if systemctl --user -q is-active niri.service; then
+      echo 'A niri session is already running.'
+      exit 1
+    fi
+
+    # Reset failed state of all user units.
+    systemctl --user reset-failed
+
+    # Import the login manager environment.
+    systemctl --user import-environment
+
+    # DBus activation environment is independent from systemd. While most of
+    # dbus-activated services are already using `SystemdService` directive, some
+    # still don't and thus we should set the dbus environment with a separate
+    # command.
+    if hash dbus-update-activation-environment 2>/dev/null; then
+        dbus-update-activation-environment --all
+    fi
+
+    # Start niri and wait for it to terminate.
+    systemctl --user --wait start niri.service
+
+    # Force stop of graphical-session.target.
+    systemctl --user start --job-mode=replace-irreversibly niri-shutdown.target
+
+    # Unset environment that we've set.
+    systemctl --user unset-environment WAYLAND_DISPLAY XDG_SESSION_TYPE XDG_CURRENT_DESKTOP NIRI_SOCKET
+elif hash dinitctl &> /dev/null; then
+    # Check that the user dinit daemon is running
+    if ! pgrep -u $(id -u) dinit &> /dev/null; then
+      echo "dinit user daemon is not running."
+      exit 1
+    fi
+
+    # Make sure there's no already running session.
+    if dinitctl --user is-started niri &> /dev/null; then
+      echo 'A niri session is already running.'
+      exit 1
+    fi
+
+    # Start niri
+    dinitctl --user start niri
+else
+    echo "No systemd or dinit detected, please use niri --session instead."
 fi
-
-# Reset failed state of all user units.
-systemctl --user reset-failed
-
-# Import the login manager environment.
-systemctl --user import-environment
-
-# DBus activation environment is independent from systemd. While most of
-# dbus-activated services are already using `SystemdService` directive, some
-# still don't and thus we should set the dbus environment with a separate
-# command.
-if hash dbus-update-activation-environment 2>/dev/null; then
-    dbus-update-activation-environment --all
-fi
-
-# Start niri and wait for it to terminate.
-systemctl --user --wait start niri.service
-
-# Force stop of graphical-session.target.
-systemctl --user start --job-mode=replace-irreversibly niri-shutdown.target
-
-# Unset environment that we've set.
-systemctl --user unset-environment WAYLAND_DISPLAY XDG_SESSION_TYPE XDG_CURRENT_DESKTOP NIRI_SOCKET