waylandloginmanager: Use the nested systemd-user solution from xrdp, …

…don't limit to one systemd --user initilized session

neutrinolabs/xrdp#2491 (comment)

The kwin issue seems to be a recent issue that impacts non systemd initiated instances, and the gnome-shell issue appears when systemd --user is running as normal
Two instance of systemd initilized kwin start in parallel. reactivation does work on older versions of kwin

The nested instance has its own dbus socket in its own XDG_RUNTIME_DIR (one under the real XDG_RUNTIME_DIR) the guest systemd user service runs as a transient service started by the user's main session.
This allows one user to start multiple sessions as themselves, a good use case for users testing multiple desktops and switching between them on a live cd

git-svn-id: https://svn.code.sf.net/p/rebeccablackos/code@8052 b52b6941-3400-464c-9f42-43200397181c

rebeccablackos_files/usr/bin/waylandloginmanager

@@ -232,6 +232,24 @@ function UserSessionWorker
   journalctl -f -b _SYSTEMD_SESSION=$XDG_SESSION_ID >> $WLM_SESSION_LOG 2>/dev/null &
   JournalctlPID=$!
 
+  #Create an isolated systemd user session running under the current systemd user session. This allows multiple systemd managed sessions to allow to run as the same user at the same time. The initilization of the "systemctl --user" instance comes from xrdp.
+  if [[ $WLM_NO_DBUS_RUN_SESSION == 1 ]]
+  then
+    BASE_DBUS_SESSION_BUS_ADDRESS=$DBUS_SESSION_BUS_ADDRESS
+    BASE_XDG_RUNTIME_DIR=$XDG_RUNTIME_DIR
+    WLM_XDG_RUNTIME_DIR=/run/user/`id -u`/wlm-rd-"$WAYLAND_GUEST"
+    WLM_DBUS_SESSION_BUS_ADDRESS="unix:path=$WLM_XDG_RUNTIME_DIR/bus"
+    install -dDTm700 $WLM_XDG_RUNTIME_DIR
+    systemd-run --user -u "wlm-systemd-$WAYLAND_GUEST" -E XDG_RUNTIME_DIR="$WLM_XDG_RUNTIME_DIR" -E DBUS_SESSION_BUS_ADDRESS="$WLM_DBUS_SESSION_BUS_ADDRESS" systemd --user
+    export DBUS_SESSION_BUS_ADDRESS=$WLM_DBUS_SESSION_BUS_ADDRESS
+    export XDG_RUNTIME_DIR=$WLM_XDG_RUNTIME_DIR
+    #Wait for the socket to be active
+    while [[ ! -e "$WLM_XDG_RUNTIME_DIR/bus" ]]
+    do
+      $SLEEPCMD .1
+    done
+  fi
+
   if [[ $BackendType == WKS || $BackendType == WL ]]
   then
     export WLM_HOST_LOG="$HOME"/.cache/wlsessionlogs/waylandhost_${WLM_SEAT}.log
@@ -297,16 +315,7 @@ function UserSessionWorker
     then
       dbus-run-session -- ${ArgArray[@]} &>> $WLM_SESSION_LOG &
     else
-      if systemctl --quiet --user is-active graphical-session.target
-      then
-        echo "systemd only allows one session using systemd-user for one user. Another session is running. Exiting this session." >> $WLM_SESSION_LOG
-        export WLR_RENDERER_ALLOW_SOFTWARE=1
-        export WLR_LIBINPUT_NO_DEVICES=1
-        export WLR_NO_HARDWARE_CURSORS=1
-        cage -d -s -m extend -- foot -- dialog --msgbox "This session uses systemd to manage its startup."$'\n'"Unfortunately, there already is another session that does so for this user."$'\n'"A systemd limitation prevents a user from having multiple of these types of sessions running at a time."$'\n'"Will now exit." 10 70 &>> $WLM_SESSION_LOG &
-      else
-        ${ArgArray[@]} &>> $WLM_SESSION_LOG &
-      fi
+      ${ArgArray[@]} &>> $WLM_SESSION_LOG &
     fi
   fi
   GuestServerPID=$!
@@ -333,6 +342,12 @@ function UserSessionWorker
     fi
   fi
 
+  #Stop the nested systemctl --user session if it was started.
+  if [[ $WLM_NO_DBUS_RUN_SESSION == 1 ]]
+  then
+    XDG_RUNTIME_DIR=$BASE_XDG_RUNTIME_DIR DBUS_SESSION_BUS_ADDRESS=$BASE_DBUS_SESSION_BUS_ADDRESS systemctl --user stop "wlm-systemd-$WAYLAND_GUEST"
+  fi
+
   #Write the error code into the logfile
   echo -e "\nSession exited with the error code: $SessionReturnCode" >> $WLM_SESSION_LOG
   $SLEEPCMD 1