gnu: vm-image.tmpl: Improve SPICE dynamic resizing.

* gnu/system/examples/vm-image.tmpl (auto-update-resolution-crutch): Delete
variable.
(operating-system) [packages]: Add x-resize.
[services]: Remove auto-update-resolution-crutch mcron service.

Fixes: https://issues.guix.gnu.org/57068
Reported-by: Ludovic Courtès <ludo@gnu.org>
Change-Id: I45cd3d79b94ece2511d324c7b180f8f37bd9ba49

gnu/system/examples/vm-image.tmpl

@@ -8,7 +8,7 @@
 (use-modules (gnu) (guix) (srfi srfi-1))
 (use-service-modules desktop mcron networking spice ssh xorg sddm)
 (use-package-modules bootloaders certs fonts
-                     package-management xorg)
+                     package-management xdisorg xorg)
 
 (define vm-image-motd (plain-file "motd" "
 \x1b[1;37mThis is the GNU system.  Welcome!\x1b[0m
@@ -25,18 +25,6 @@ Run '\x1b[1;37minfo guix\x1b[0m' to browse documentation.
 accounts.\x1b[0m
 "))
 
-;;; XXX: Xfce does not implement what is needed for the SPICE dynamic
-;;; resolution to work (see:
-;;; https://gitlab.xfce.org/xfce/xfce4-settings/-/issues/142).  Workaround it
-;;; by manually invoking xrandr every second.
-(define auto-update-resolution-crutch
-  #~(job '(next-second)
-         (lambda ()
-           (setenv "DISPLAY" ":0.0")
-           (setenv "XAUTHORITY" "/home/guest/.Xauthority")
-           (execl (string-append #$xrandr "/bin/xrandr") "xrandr" "-s" "0"))
-         #:user "guest"))
-
 (operating-system
   (host-name "gnu")
   (timezone "Etc/UTC")
@@ -65,7 +53,7 @@ accounts.\x1b[0m
   (users (cons (user-account
                 (name "guest")
                 (comment "GNU Guix Live")
-                (password "")                     ;no password
+                (password "")           ;no password
                 (group "users")
                 (supplementary-groups '("wheel" "netdev"
                                         "audio" "video")))
@@ -77,8 +65,13 @@ accounts.\x1b[0m
 root ALL=(ALL) ALL
 %wheel ALL=NOPASSWD: ALL\n"))
 
-  (packages (append (list font-bitstream-vera nss-certs)
-                    %base-packages))
+  (packages
+   (append (list font-bitstream-vera nss-certs
+                 ;; Auto-started script providing SPICE dynamic resizing for
+                 ;; Xfce (see:
+                 ;; https://gitlab.xfce.org/xfce/xfce4-settings/-/issues/142).
+                 x-resize)
+           %base-packages))
 
   (services
    (append (list (service xfce-desktop-service-type)
@@ -104,9 +97,6 @@ root ALL=(ALL) ALL
                  ;; integration with the host, etc.
                  (service spice-vdagent-service-type)
 
-                 (simple-service 'cron-jobs mcron-service-type
-                                 (list auto-update-resolution-crutch))
-
                  ;; Use the DHCP client service rather than NetworkManager.
                  (service dhcp-client-service-type))