services: xorg: Document 'slim-configuration' and deprecate 'slim-service'.

* gnu/services/xorg.scm (<slim-configuration>): Provide default values
for all fields.
(slim-service-type)[default-value]: New field.
* doc/guix.texi (X Window): Remove 'slim-service' documentation.
Document 'slim-service-type' and 'slim-configuration'.
* gnu/services/desktop.scm (%desktop-services): Use 'slim-service-type'.

doc/guix.texi

@@ -11001,6 +11001,65 @@ Xorg---is provided by the @code{(gnu services xorg)} module.  Note that
 there is no @code{xorg-service} procedure.  Instead, the X server is
 started by the @dfn{login manager}, currently SLiM.
 
+@defvr {Scheme Variable} slim-service-type
+This is the type for the SLiM graphical login manager for X11.
+
+@cindex session types (X11)
+@cindex X11 session types
+SLiM looks for @dfn{session types} described by the @file{.desktop} files in
+@file{/run/current-system/profile/share/xsessions} and allows users to
+choose a session from the log-in screen using @kbd{F1}.  Packages such
+as @code{xfce}, @code{sawfish}, and @code{ratpoison} provide
+@file{.desktop} files; adding them to the system-wide set of packages
+automatically makes them available at the log-in screen.
+
+In addition, @file{~/.xsession} files are honored.  When available,
+@file{~/.xsession} must be an executable that starts a window manager
+and/or other X clients.
+@end defvr
+
+@deftp {Data Type} slim-configuration
+Data type representing the configuration of @code{slim-service-type}.
+
+@table @asis
+@item @code{allow-empty-passwords?} (default: @code{#t})
+Whether to allow logins with empty passwords.
+
+@item @code{auto-login?} (default: @code{#f})
+@itemx @code{default-user} (default: @code{""})
+When @code{auto-login?} is false, SLiM presents a log-in screen.
+
+When @code{auto-login?} is true, SLiM logs in directly as
+@code{default-user}.
+
+@item @code{theme} (default: @code{%default-slim-theme})
+@itemx @code{theme-name} (default: @code{%default-slim-theme-name})
+The graphical theme to use and its name.
+
+@item @code{auto-login-session} (default: @code{windowmaker})
+The default session to use when none is specified.
+
+@item @code{startx} (default: @code{(xorg-start-command)})
+The command used to start the X11 graphical server.
+
+@item @code{xauth} (default: @code{xauth})
+The XAuth package to use.
+
+@item @code{shepherd} (default: @code{shepherd})
+The Shepherd package used when invoking @command{halt} and
+@command{reboot}.
+
+@item @code{slim} (default: @code{slim})
+The SLiM package to use.
+@end table
+@end deftp
+
+@defvr {Scheme Variable} %default-theme
+@defvrx {Scheme Variable} %default-theme-name
+The default SLiM theme and its name.
+@end defvr
+
+
 @deftp {Data Type} sddm-configuration
 This is the data type representing the sddm service configuration.
 
@@ -11094,6 +11153,7 @@ Relogin after logout.
 @end deftp
 
 @cindex login manager
+@cindex X11 login
 @deffn {Scheme Procedure} sddm-service config
 Return a service that spawns the SDDM graphical login manager for config of
 type @code{<sddm-configuration>}.
@@ -11105,42 +11165,6 @@ type @code{<sddm-configuration>}.
 @end example
 @end deffn
 
-@deffn {Scheme Procedure} slim-service [#:allow-empty-passwords? #f] @
-  [#:auto-login? #f] [#:default-user ""] [#:startx] @
-  [#:theme @var{%default-slim-theme}] @
-  [#:theme-name @var{%default-slim-theme-name}]
-Return a service that spawns the SLiM graphical login manager, which in
-turn starts the X display server with @var{startx}, a command as returned by
-@code{xorg-start-command}.
-
-@cindex X session
-
-SLiM automatically looks for session types described by the @file{.desktop}
-files in @file{/run/current-system/profile/share/xsessions} and allows users
-to choose a session from the log-in screen using @kbd{F1}.  Packages such as
-@var{xfce}, @var{sawfish}, and @var{ratpoison} provide @file{.desktop} files;
-adding them to the system-wide set of packages automatically makes them
-available at the log-in screen.
-
-In addition, @file{~/.xsession} files are honored.  When available,
-@file{~/.xsession} must be an executable that starts a window manager
-and/or other X clients.
-
-When @var{allow-empty-passwords?} is true, allow logins with an empty
-password.  When @var{auto-login?} is true, log in automatically as
-@var{default-user}.
-
-If @var{theme} is @code{#f}, use the default log-in theme; otherwise
-@var{theme} must be a gexp denoting the name of a directory containing the
-theme to use.  In that case, @var{theme-name} specifies the name of the
-theme.
-@end deffn
-
-@defvr {Scheme Variable} %default-theme
-@defvrx {Scheme Variable} %default-theme-name
-The G-Expression denoting the default SLiM theme and its name.
-@end defvr
-
 @deffn {Scheme Procedure} xorg-start-command [#:guile] @
   [#:modules %default-xorg-modules] @
   [#:fonts %default-xorg-fonts] @

gnu/services/desktop.scm

@@ -854,7 +854,7 @@ (define* (xfce-desktop-service #:key (config (xfce-desktop-configuration)))
 
 (define %desktop-services
   ;; List of services typically useful for a "desktop" use case.
-  (cons* (slim-service)
+  (cons* (service slim-service-type)
 
          ;; Screen lockers are a pretty useful thing and these are small.
          (screen-locker-service slock)

gnu/services/xorg.scm

@@ -52,7 +52,20 @@ (define-module (gnu services xorg)
 
             %default-slim-theme
             %default-slim-theme-name
+
             slim-configuration
+            slim-configuration?
+            slim-configuration-slim
+            slim-configuration-allow-empty-passwords?
+            slim-configuration-auto-login?
+            slim-configuration-default-user
+            slim-configuration-theme
+            slim-configuration-theme-name
+            slim-configuration-xauth
+            slim-configuration-shepherd
+            slim-configuration-auto-login-session
+            slim-configuration-startx
+
             slim-service-type
             slim-service
 
@@ -355,17 +368,24 @@ (define-record-type* <slim-configuration>
   slim-configuration?
   (slim slim-configuration-slim
         (default slim))
-  (allow-empty-passwords? slim-configuration-allow-empty-passwords?)
-  (auto-login? slim-configuration-auto-login?)
-  (default-user slim-configuration-default-user)
-  (theme slim-configuration-theme)
-  (theme-name slim-configuration-theme-name)
+  (allow-empty-passwords? slim-configuration-allow-empty-passwords?
+                          (default #t))
+  (auto-login? slim-configuration-auto-login?
+               (default #f))
+  (default-user slim-configuration-default-user
+                (default ""))
+  (theme slim-configuration-theme
+         (default %default-slim-theme))
+  (theme-name slim-configuration-theme-name
+              (default %default-slim-theme-name))
   (xauth slim-configuration-xauth
          (default xauth))
   (shepherd slim-configuration-shepherd
             (default shepherd))
-  (auto-login-session slim-configuration-auto-login-session)
-  (startx slim-configuration-startx))
+  (auto-login-session slim-configuration-auto-login-session
+                      (default (file-append windowmaker "/bin/wmaker")))
+  (startx slim-configuration-startx
+          (default (xorg-start-command))))
 
 (define (slim-pam-service config)
   "Return a PAM service for @command{slim}."
@@ -440,9 +460,10 @@ (define slim-service-type
                        ;; Unconditionally add xterm to the system profile, to
                        ;; avoid bad surprises.
                        (service-extension profile-service-type
-                                          (const (list xterm)))))))
+                                          (const (list xterm)))))
+                (default-value (slim-configuration))))
 
-(define* (slim-service #:key (slim slim)
+(define* (slim-service #:key (slim slim)          ;deprecated
                        (allow-empty-passwords? #t) auto-login?
                        (default-user "")
                        (theme %default-slim-theme)