;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2017 Andy Wingo <wingo@igalia.com>
;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2019, 2020 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2015 Sou Bunnbu <iyzsong@gmail.com>
;;; Copyright © 2018, 2019 Timothy Sample <samplet@ngyro.com>
;;; Copyright © 2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
;;; Copyright © 2019 Tim Gesthuizen <tim.gesthuizen@yahoo.de>
;;; Copyright © 2020 shtwzrd <shtwzrd@protonmail.com>
;;; Copyright © 2020 Jakub Kądziołka <kuba@kadziolka.net>
;;; Copyright © 2020 Alex Griffin <a@ajgrf.com>
;;; Copyright © 2021 Brice Waegeneire <brice@waegenei.re>
;;; Copyright © 2021 Oleg Pykhalov <go.wigust@gmail.com>
;;; Copyright © 2021 Josselin Poiret <josselin.poiret@protonmail.ch>
;;; Copyright © 2022 Chris Marusich <cmmarusich@gmail.com>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.

(define-module (gnu services xorg)
  #:autoload   (gnu services sddm) (sddm-service-type)
  #:use-module (gnu artwork)
  #:use-module (gnu services)
  #:use-module (gnu services shepherd)
  #:use-module (gnu system pam)
  #:use-module (gnu system setuid)
  #:use-module (gnu system keyboard)
  #:use-module (gnu services base)
  #:use-module (gnu services dbus)
  #:use-module (gnu packages base)
  #:use-module (gnu packages guile)
  #:use-module (gnu packages xorg)
  #:use-module (gnu packages fonts)
  #:use-module (gnu packages gl)
  #:use-module (gnu packages glib)
  #:use-module (gnu packages display-managers)
  #:use-module (gnu packages freedesktop)
  #:use-module (gnu packages gnustep)
  #:use-module (gnu packages gnome)
  #:use-module (gnu packages admin)
  #:use-module (gnu packages bash)
  #:use-module (gnu system shadow)
  #:use-module (guix build-system glib-or-gtk)
  #:use-module (guix build-system trivial)
  #:use-module (guix gexp)
  #:use-module (guix store)
  #:use-module (guix packages)
  #:use-module (guix derivations)
  #:use-module (guix records)
  #:use-module (guix deprecation)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-9)
  #:use-module (srfi srfi-26)
  #:use-module (ice-9 match)
  #:export (xorg-configuration
            xorg-configuration?
            xorg-configuration-modules
            xorg-configuration-fonts
            xorg-configuration-drivers
            xorg-configuration-resolutions
            xorg-configuration-extra-config
            xorg-configuration-server
            xorg-configuration-server-arguments

            %default-xorg-modules
            %default-xorg-fonts
            %default-xorg-server-arguments

            xorg-wrapper
            xorg-start-command
            xinitrc
            xorg-server-service-type

            %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-xorg
            slim-configuration-display
            slim-configuration-vt
            slim-configuration-sessreg

            slim-service-type

            screen-locker
            screen-locker?
            screen-locker-service-type
            screen-locker-service

            localed-configuration
            localed-configuration?
            localed-service-type

            gdm-configuration
            gdm-service-type

            handle-xorg-configuration
            set-xorg-configuration))

;;; Commentary:
;;;
;;; Services that relate to the X Window System.
;;;
;;; Code:

(define %default-xorg-modules
  ;; Default list of modules loaded by the server.  When multiple drivers
  ;; match, the first one in the list is loaded.
  (list xf86-video-vesa
        xf86-video-fbdev
        xf86-video-amdgpu
        xf86-video-ati
        xf86-video-cirrus
        xf86-video-intel
        xf86-video-mach64
        xf86-video-nouveau
        xf86-video-nv
        xf86-video-sis

        ;; Libinput is the new thing and is recommended over evdev/synaptics:
        ;; <http://who-t.blogspot.fr/2015/01/xf86-input-libinput-compatibility-with.html>.
        xf86-input-libinput

        xf86-input-evdev
        xf86-input-keyboard
        xf86-input-mouse
        xf86-input-synaptics))

(define %default-xorg-fonts
  ;; Default list of fonts available to the X server.
  (list (file-append font-alias "/share/fonts/X11/75dpi")
        (file-append font-alias "/share/fonts/X11/100dpi")
        (file-append font-alias "/share/fonts/X11/misc")
        (file-append font-alias "/share/fonts/X11/cyrillic")
        (file-append font-misc-misc               ;default fonts for xterm
                     "/share/fonts/X11/misc")
        (file-append font-adobe75dpi "/share/fonts/X11/75dpi")))

(define %default-xorg-server-arguments
  ;; Default command-line arguments for X.
  '("-nolisten" "tcp"))

;; Configuration of an Xorg server.
(define-record-type* <xorg-configuration>
  xorg-configuration make-xorg-configuration
  xorg-configuration?
  (modules          xorg-configuration-modules    ;list of file-like
                    (thunked)
                    ; filter out modules not supported on current system
                    (default (filter
                              (lambda (p)
                                (member (%current-system)
                                        (package-supported-systems p)))
                              %default-xorg-modules)))
  (fonts            xorg-configuration-fonts      ;list of packges
                    (default %default-xorg-fonts))
  (drivers          xorg-configuration-drivers    ;list of strings
                    (default '()))
  (resolutions      xorg-configuration-resolutions ;list of tuples
                    (default '()))
  (keyboard-layout  xorg-configuration-keyboard-layout ;#f | <keyboard-layout>
                    (default #f))
  (extra-config     xorg-configuration-extra-config ;list of strings
                    (default '()))
  (server           xorg-configuration-server     ;file-like
                    (default xorg-server))
  (server-arguments xorg-configuration-server-arguments ;list of strings
                    (default %default-xorg-server-arguments)))

(define (xorg-configuration->file config)
  "Compute an Xorg configuration file corresponding to CONFIG, an
<xorg-configuration> record."
  (let ((xorg-server (xorg-configuration-server config)))
    (define all-modules
      ;; 'xorg-server' provides 'fbdevhw.so' etc.
      (append (xorg-configuration-modules config)
              (list xorg-server)))

    (define build
      #~(begin
          (use-modules (ice-9 match)
                       (srfi srfi-1)
                       (srfi srfi-26))

          (call-with-output-file #$output
            (lambda (port)
              (define drivers
                '#$(xorg-configuration-drivers config))

              (define (device-section driver)
                (string-append "
Section \"Device\"
  Identifier \"device-" driver "\"
  Driver \"" driver "\"
EndSection"))

              (define (screen-section driver resolutions)
                (string-append "
Section \"Screen\"
  Identifier \"screen-" driver "\"
  Device \"device-" driver "\"
  SubSection \"Display\"
    Modes "
  (string-join (map (match-lambda
                      ((x y)
                       (string-append "\"" (number->string x)
                                      "x" (number->string y) "\"")))
                    resolutions)) "
  EndSubSection
EndSection"))

              (define (input-class-section layout variant model options)
                (string-append "
Section \"InputClass\"
  Identifier \"evdev keyboard catchall\"
  MatchIsKeyboard \"on\"
  Option \"XkbLayout\" " (object->string layout)
  (if variant
      (string-append "  Option \"XkbVariant\" \""
                     variant "\"")
      "")
  (if model
      (string-append "  Option \"XkbModel\" \""
                     model "\"")
      "")
  (match options
    (()
     "")
    (_
     (string-append "  Option \"XkbOptions\" \""
                    (string-join options ",") "\""))) "

  MatchDevicePath \"/dev/input/event*\"
  Driver \"evdev\"
EndSection\n"))

              (define (expand modules)
                ;; Append to MODULES the relevant /lib/xorg/modules
                ;; sub-directories.
                (append-map (lambda (module)
                              (filter-map (lambda (directory)
                                            (let ((full (string-append module
                                                                       directory)))
                                              (and (file-exists? full)
                                                   full)))
                                          '("/lib/xorg/modules/drivers"
                                            "/lib/xorg/modules/input"
                                            "/lib/xorg/modules/multimedia"
                                            "/lib/xorg/modules/extensions")))
                            modules))

              (display "Section \"Files\"\n" port)
              (for-each (lambda (font)
                          (format port "  FontPath \"~a\"~%" font))
                        '#$(xorg-configuration-fonts config))
              (for-each (lambda (module)
                          (format port
                                  "  ModulePath \"~a\"~%"
                                  module))
                        (append (expand '#$all-modules)

                                ;; For fbdevhw.so and so on.
                                (list #$(file-append xorg-server
                                                     "/lib/xorg/modules"))))
              (display "EndSection\n" port)
              (display "
Section \"ServerFlags\"
  Option \"AllowMouseOpenFail\" \"on\"
EndSection\n" port)

              (display (string-join (map device-section drivers) "\n")
                       port)
              (newline port)
              (display (string-join
                        (map (cut screen-section <>
                                  '#$(xorg-configuration-resolutions config))
                             drivers)
                        "\n")
                       port)
              (newline port)

              (let ((layout  #$(and=> (xorg-configuration-keyboard-layout config)
                                      keyboard-layout-name))
                    (variant #$(and=> (xorg-configuration-keyboard-layout config)
                                      keyboard-layout-variant))
                    (model   #$(and=> (xorg-configuration-keyboard-layout config)
                                      keyboard-layout-model))
                    (options '#$(and=> (xorg-configuration-keyboard-layout config)
                                       keyboard-layout-options)))
                (when layout
                  (display (input-class-section layout variant model options)
                           port)
                  (newline port)))

              (for-each (lambda (config)
                          (display config port))
                        '#$(xorg-configuration-extra-config config))))))

    (computed-file "xserver.conf" build)))

(define (xorg-configuration-directory modules)
  "Return a directory that contains the @code{.conf} files for X.org that
includes the @code{share/X11/xorg.conf.d} directories of each package listed
in @var{modules}."
  (with-imported-modules '((guix build utils))
    (computed-file "xorg.conf.d"
                   #~(begin
                       (use-modules (guix build utils)
                                    (srfi srfi-1))

                       (define files
                         (append-map (lambda (module)
                                       (find-files (string-append
                                                    module
                                                    "/share/X11/xorg.conf.d")
                                                   "\\.conf$"))
                                     (list #$@modules)))

                       (mkdir #$output)
                       (for-each (lambda (file)
                                   (symlink file
                                            (string-append #$output "/"
                                                           (basename file))))
                                 files)
                       #t))))

(define* (xorg-wrapper #:optional (config (xorg-configuration)))
  "Return a derivation that builds a script to start the X server with the
given @var{config}.  The resulting script should be used in place of
@code{/usr/bin/X}."
  (define exp
    ;; Write a small wrapper around the X server.
    #~(begin
        (setenv "XORG_DRI_DRIVER_PATH" (string-append #$mesa "/lib/dri"))
        (setenv "XKB_BINDIR" (string-append #$xkbcomp "/bin"))

        (let ((X (string-append #$(xorg-configuration-server config) "/bin/X")))
          (apply execl X X
                 "-xkbdir" (string-append #$xkeyboard-config "/share/X11/xkb")
                 "-config" #$(xorg-configuration->file config)
                 "-configdir" #$(xorg-configuration-directory
                                 (xorg-configuration-modules config))
                 (cdr (command-line))))))

  (program-file "X-wrapper" exp))

(define* (xorg-start-command #:optional (config (xorg-configuration)))
  "Return a @code{startx} script in which the modules, fonts, etc. specified
in @var{config}, are available.  The result should be used in place of
@code{startx}."
  (define X
    (xorg-wrapper config))

  (define exp
    ;; Write a small wrapper around the X server.
    #~(apply execl #$X #$X ;; Second #$X is for argv[0].
             "-logverbose" "-verbose" "-terminate"
             #$@(xorg-configuration-server-arguments config)
              (cdr (command-line))))

  (program-file "startx" exp))

(define* (xinitrc #:key fallback-session)
  "Return a system-wide xinitrc script that starts the specified X session,
which should be passed to this script as the first argument.  If not, the
@var{fallback-session} will be used or, if @var{fallback-session} is false, a
desktop session from the system or user profile will be used."
  (define builder
    #~(begin
        (use-modules (ice-9 match)
                     (ice-9 regex)
                     (ice-9 ftw)
                     (ice-9 rdelim)
                     (srfi srfi-1)
                     (srfi srfi-26))

        (define (close-all-fdes)
          ;; Close all the open file descriptors except 0 to 2.
          (let loop ((fd 3))
            (when (< fd 4096)               ;FIXME: use sysconf + _SC_OPEN_MAX
              (false-if-exception (close-fdes fd))
              (loop (+ 1 fd)))))

        (define (exec-from-login-shell command . args)
          ;; Run COMMAND from a login shell so that it gets to see the same
          ;; environment variables that one gets when logging in on a tty, for
          ;; instance.
          (let* ((pw    (getpw (getuid)))
                 (shell (passwd:shell pw)))
            ;; Close any open file descriptors.  This is all the more
            ;; important that SLiM itself exec's us directly without closing
            ;; its own file descriptors!
            (close-all-fdes)

            ;; The '--login' option is supported at least by Bash and zsh.
            (execl shell shell "--login" "-c"
                   (string-join (cons command args)))))

        (define system-profile
          "/run/current-system/profile")

        (define user-profile
          (and=> (getpw (getuid))
                 (lambda (pw)
                   (string-append (passwd:dir pw) "/.guix-profile"))))

        (define (xsession-command desktop-file)
          ;; Read from DESKTOP-FILE its X session command and return it as a
          ;; list.
          (define exec-regexp
            (make-regexp "^[[:blank:]]*Exec=(.*)$"))

          (call-with-input-file desktop-file
            (lambda (port)
              (let loop ()
                (match (read-line port)
                  ((? eof-object?) #f)
                  ((= (cut regexp-exec exec-regexp <>) result)
                   (if result
                       (string-tokenize (match:substring result 1))
                       (loop))))))))

        (define (find-session profile)
          ;; Return an X session command from PROFILE or #f if none was found.
          (let ((directory (string-append profile "/share/xsessions")))
            (match (scandir directory
                            (cut string-suffix? ".desktop" <>))
              ((or () #f)
               #f)
              ((sessions ...)
               (any xsession-command
                    (map (cut string-append directory "/" <>)
                         sessions))))))

        (let* ((home          (getenv "HOME"))
               (xsession-file (string-append home "/.xsession"))
               (session       (match (command-line)
                                ((_)
                                 #$(if fallback-session
                                       #~(list #$fallback-session)
                                       #f))
                                ((_ x ..1)
                                 x))))
          (if (file-exists? xsession-file)
              ;; Run ~/.xsession when it exists.
              (apply exec-from-login-shell xsession-file
                     (or session '()))
              ;; Otherwise, start the specified session or a fallback.
              (apply exec-from-login-shell
                     (or session
                         (find-session user-profile)
                         (find-session system-profile)))))))

  (program-file "xinitrc" builder))

(define-syntax handle-xorg-configuration
  (syntax-rules ()
    "Generate the `compose' and `extend' entries of a login manager
`service-type' to handle specifying the `xorg-configuration' through
a `service-extension', as used by `set-xorg-configuration'."
    ((_ configuration-record service-type-definition)
     (service-type
       (inherit service-type-definition)
       (compose (lambda (extensions)
                  (match extensions
                    (() #f)
                    ((config . _) config))))
       (extend (lambda (config xorg-configuration)
                 (if xorg-configuration
                     (configuration-record
                      (inherit config)
                      (xorg-configuration xorg-configuration))
                     config)))))))

(define (xorg-server-profile-service config)
  ;; XXX: profile-service-type only accepts <package> objects.
  (list
   (package
     (name "xorg-wrapper")
     (version (package-version xorg-server))
     (source (xorg-wrapper config))
     (build-system trivial-build-system)
     (arguments
      '(#:modules ((guix build utils))
        #:builder
        (begin
          (use-modules (guix build utils))
          (let* ((source (assoc-ref %build-inputs "source"))
                 (out (assoc-ref %outputs "out"))
                 (bin (string-append out "/bin")))
            (mkdir-p bin)
            (symlink source (string-append bin "/X"))
            (symlink source (string-append bin "/Xorg"))
            #t))))
     (home-page (package-home-page xorg-server))
     (synopsis (package-synopsis xorg-server))
     (description (package-description xorg-server))
     (license (package-license xorg-server)))))

(define xorg-server-service-type
  (service-type
   (name 'xorg-server)
   (extensions
    (list (service-extension profile-service-type
                             xorg-server-profile-service)))
   (default-value (xorg-configuration))
   (description "Add @command{X} to the system profile, to be used with
@command{sx} or @command{xinit}.")))

\f
;;;
;;; SLiM log-in manager.
;;;

(define %default-slim-theme
  ;; Theme based on work by Felipe López.
  (file-append %artwork-repository "/slim"))

(define %default-slim-theme-name
  ;; This must be the name of the sub-directory in %DEFAULT-SLIM-THEME that
  ;; contains the actual theme files.
  "1.x")

(define-record-type* <slim-configuration>
  slim-configuration make-slim-configuration
  slim-configuration?
  (slim slim-configuration-slim
        (default slim))
  (allow-empty-passwords? slim-configuration-allow-empty-passwords?
                          (default #t))
  (gnupg? slim-configuration-gnupg?
          (default #f))
  (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
                      (default #f))
  (xorg-configuration slim-configuration-xorg
                      (default (xorg-configuration)))
  (display slim-configuration-display
           (default ":0"))
  (vt slim-configuration-vt
      (default "vt7"))
  (sessreg slim-configuration-sessreg
           (default sessreg)))

(define (slim-pam-service config)
  "Return a PAM service for @command{slim}."
  (list (unix-pam-service
         "slim"
         #:login-uid? #t
         #:allow-empty-passwords?
         (slim-configuration-allow-empty-passwords? config)
         #:gnupg?
         (slim-configuration-gnupg? config))))

(define (slim-shepherd-service config)
  (let* ((xinitrc (xinitrc #:fallback-session
                           (slim-configuration-auto-login-session config)))
         (xauth   (slim-configuration-xauth config))
         (startx  (xorg-start-command (slim-configuration-xorg config)))
         (display (slim-configuration-display config))
         (vt (slim-configuration-vt config))
         (shepherd   (slim-configuration-shepherd config))
         (theme-name (slim-configuration-theme-name config))
         (sessreg (slim-configuration-sessreg config))
         (lockfile (string-append "/var/run/slim-" vt ".lock")))
    (define slim.cfg
      (mixed-text-file "slim.cfg"  "
default_path /run/current-system/profile/bin
default_xserver " startx "
display_name " display "
xserver_arguments " vt "
xauth_path " xauth "/bin/xauth
authfile /var/run/slim-" vt ".auth
lockfile " lockfile "
logfile /var/log/slim-" vt ".log

# The login command.  '%session' is replaced by the chosen session name, one
# of the names specified in the 'sessions' setting: 'wmaker', 'xfce', etc.
login_cmd  exec " xinitrc " %session
sessiondir /run/current-system/profile/share/xsessions
session_msg session (F1 to change):
sessionstart_cmd " sessreg "/bin/sessreg -a -l $DISPLAY %user
sessionstop_cmd " sessreg "/bin/sessreg -d -l $DISPLAY %user

halt_cmd " shepherd "/sbin/halt
reboot_cmd " shepherd "/sbin/reboot\n"
(if (slim-configuration-auto-login? config)
    (string-append "auto_login yes\ndefault_user "
                   (slim-configuration-default-user config) "\n")
    "")
(if theme-name
    (string-append "current_theme " theme-name "\n")
    "")))

    (define theme
      (slim-configuration-theme config))

    (list (shepherd-service
           (documentation "Xorg display server")
           (provision (append
                       ;; For compatibility, also provide 'xorg-server'.
                       (if (string=? vt "vt7")
                           '(xorg-server)
                           '())

                       (list (symbol-append 'xorg-server-
                                            (string->symbol vt)))))
           (requirement '(user-processes host-name udev))
           (start
            #~(lambda ()
                ;; A stale lock file can prevent SLiM from starting, so remove it to
                ;; be on the safe side.
                (false-if-exception (delete-file lockfile))

                (fork+exec-command
                 (list (string-append #$(slim-configuration-slim config)
                                      "/bin/slim")
                       "-nodaemon")
                 #:environment-variables
                 (list (string-append "SLIM_CFGFILE=" #$slim.cfg)
                       #$@(if theme
                              (list #~(string-append "SLIM_THEMESDIR=" #$theme))
                              #~())))))
           (stop #~(make-kill-destructor))
           (respawn? #t)))))

(define slim-service-type
  (handle-xorg-configuration slim-configuration
    (service-type (name 'slim)
                  (extensions
                   (list (service-extension shepherd-root-service-type
                                            slim-shepherd-service)
                         (service-extension pam-root-service-type
                                            slim-pam-service)

                         ;; Unconditionally add xterm to the system profile, to
                         ;; avoid bad surprises.
                         (service-extension profile-service-type
                                            (const (list xterm)))))

                  (default-value (slim-configuration))
                  (description
                   "Run the SLiM graphical login manager for X11."))))

\f
;;;
;;; Screen lockers & co.
;;;

(define-record-type <screen-locker>
  (screen-locker name program empty?)
  screen-locker?
  (name    screen-locker-name)                     ;string
  (program screen-locker-program)                  ;gexp
  (empty?  screen-locker-allows-empty-passwords?)) ;Boolean

(define screen-locker-pam-services
  (match-lambda
    (($ <screen-locker> name _ empty?)
     (list (unix-pam-service name
                             #:allow-empty-passwords? empty?)))))

(define screen-locker-setuid-programs
  (compose list file-like->setuid-program screen-locker-program))

(define screen-locker-service-type
  (service-type (name 'screen-locker)
                (extensions
                 (list (service-extension pam-root-service-type
                                          screen-locker-pam-services)
                       (service-extension setuid-program-service-type
                                          screen-locker-setuid-programs)))
                (description
                 "Allow the given program to be used as a screen locker for
the graphical server by making it setuid-root, so it can authenticate users,
and by creating a PAM service for it.")))

(define* (screen-locker-service package
                                #:optional
                                (program (package-name package))
                                #:key allow-empty-passwords?)
  "Add @var{package}, a package for a screen locker or screen saver whose
command is @var{program}, to the set of setuid programs and add a PAM entry
for it.  For example:

@lisp
 (screen-locker-service xlockmore \"xlock\")
@end lisp

makes the good ol' XlockMore usable."
  (service screen-locker-service-type
           (screen-locker program
                          (file-append package "/bin/" program)
                          allow-empty-passwords?)))

\f
;;;
;;; Locale service.
;;;

(define-record-type* <localed-configuration>
  localed-configuration make-localed-configuration
  localed-configuration?
  (localed         localed-configuration-localed
                   (default localed))
  (keyboard-layout localed-configuration-keyboard-layout
                   (default #f)))

(define (localed-dbus-service config)
  "Return the 'localed' D-Bus service for @var{config}, a
@code{<localed-configuration>} record."
  (define keyboard-layout
    (localed-configuration-keyboard-layout config))

  ;; The primary purpose of 'localed' is to tell GDM what the "current" Xorg
  ;; keyboard layout is.  If 'localed' is missing, or if it's unable to
  ;; determine the current XKB layout, then GDM forcefully installs its
  ;; default XKB config (US English).  Here we communicate the configured
  ;; layout through environment variables.

  (if keyboard-layout
      (let* ((layout  (keyboard-layout-name keyboard-layout))
             (variant (keyboard-layout-variant keyboard-layout))
             (model   (keyboard-layout-model keyboard-layout))
             (options (keyboard-layout-options keyboard-layout)))
        (list (wrapped-dbus-service
               (localed-configuration-localed config)
               "libexec/localed/localed"
               `(("GUIX_XKB_LAYOUT" ,layout)
                 ,@(if variant
                       `(("GUIX_XKB_VARIANT" ,variant))
                       '())
                 ,@(if model
                       `(("GUIX_XKB_MODEL" ,model))
                       '())
                 ,@(if (null? options)
                       '()
                       `(("GUIX_XKB_OPTIONS"
                          ,(string-join options ","))))))))
      '()))

(define localed-service-type
  (let ((package (lambda (config)
                   ;; Don't bother if the user didn't specify any keyboard
                   ;; layout.
                   (if (localed-configuration-keyboard-layout config)
                       (list (localed-configuration-localed config))
                       '()))))
    (service-type (name 'localed)
                  (extensions
                   (list (service-extension dbus-root-service-type
                                            localed-dbus-service)
                         (service-extension udev-service-type package)
                         (service-extension polkit-service-type package)

                         ;; Add 'localectl' to the profile.
                         (service-extension profile-service-type package)))

                  ;; This service can be extended, typically by the X login
                  ;; manager, to communicate the chosen Xorg keyboard layout.
                  (compose (lambda (extensions)
                             (find keyboard-layout? extensions)))
                  (extend (lambda (config keyboard-layout)
                            (localed-configuration
                             (inherit config)
                             (keyboard-layout keyboard-layout))))
                  (description
                   "Run the locale daemon, @command{localed}, which can be used
to control the system locale and keyboard mapping from user programs such as
the GNOME desktop environment.")
                  (default-value (localed-configuration)))))

\f
;;;
;;; GNOME Desktop Manager.
;;;

(define %gdm-accounts
  (list (user-group (name "gdm") (system? #t))
        (user-account
         (name "gdm")
         (group "gdm")
         (supplementary-groups '("video"))
         (system? #t)
         (comment "GNOME Display Manager user")
         (home-directory "/var/lib/gdm")
         (shell (file-append shadow "/sbin/nologin")))))

(define %gdm-activation
  ;; Ensure /var/lib/gdm is owned by the "gdm" user.  This is normally the
  ;; case but could be wrong if the "gdm" user was created, then removed, and
  ;; then recreated under a different UID/GID: <https://bugs.gnu.org/37423>.
  (with-imported-modules '((guix build utils))
    #~(begin
        (use-modules (guix build utils))

        (let* ((gdm (getpwnam "gdm"))
               (uid (passwd:uid gdm))
               (gid (passwd:gid gdm))
               (st  (stat "/var/lib/gdm" #f)))
          ;; Recurse into /var/lib/gdm only if it has wrong ownership.
          (when (and st
                     (or (not (= uid (stat:uid st)))
                         (not (= gid (stat:gid st)))))
            (for-each (lambda (file)
                        (chown file uid gid))
                      (find-files "/var/lib/gdm"
                                  #:directories? #t)))))))

(define dbus-daemon-wrapper
  (program-file
   "gdm-dbus-wrapper"
   #~(begin
       (use-modules (srfi srfi-26))

       (define system-profile
         "/run/current-system/profile")

       (define user-profile
         (and=> (getpw (getuid))
                (lambda (pw)
                  (string-append (passwd:dir pw) "/.guix-profile"))))

       ;; If we are able to find the user's profile, we can add it to
       ;; the search paths set below.  We need to do this so that D-Bus
       ;; can start services installed by the user.  This allows
       ;; applications that require session D-Bus services (e.g,
       ;; 'evolution') to work even if those services are only available
       ;; in the user's profile.  See <https://bugs.gnu.org/35267>.
       (define profiles
         (if user-profile
             (list user-profile system-profile)
             (list system-profile)))

       (setenv "XDG_CONFIG_DIRS"
               (string-join (map (cut string-append <> "/etc/xdg") profiles)
                            ":"))
       (setenv "XDG_DATA_DIRS"
               (string-join (map (cut string-append <> "/share") profiles)
                            ":"))
       (apply execl (string-append #$dbus "/bin/dbus-daemon")
              (program-arguments)))))

;; Wrapper script for Wayland sessions, similar to Xsession.
;;
;; See `xinitrc`.  By default, it launches the specified session through a
;; login shell.  With the default Guix configuration, this should source
;; /etc/profile, setting up the Guix profile environment variables.  However,
;; gdm launches its own graphical session through the same method, so we need
;; to ignore this case, since `gdm` doesn't have a login shell.
(define gdm-wayland-session-wrapper
  (program-file
   "gdm-wayland-session-wrapper"
   #~((let* ((user (getpw (getuid)))
	    (name (passwd:name user))
	    (shell (passwd:shell user))
	    (args (cdr (command-line))))
        (if (string=? name "gdm")
	    (apply execl (cons (car args) args))
	    (execl shell shell "--login" "-c" (string-join args)))))))

(define-record-type* <gdm-configuration>
  gdm-configuration make-gdm-configuration
  gdm-configuration?
  (gdm gdm-configuration-gdm (default gdm))
  (allow-empty-passwords? gdm-configuration-allow-empty-passwords? (default #t))
  (auto-login? gdm-configuration-auto-login? (default #f))
  (dbus-daemon gdm-configuration-dbus-daemon (default dbus-daemon-wrapper))
  (debug? gdm-configuration-debug? (default #f))
  (default-user gdm-configuration-default-user (default #f))
  (gnome-shell-assets gdm-configuration-gnome-shell-assets
                      (default (list adwaita-icon-theme font-abattis-cantarell)))
  (xorg-configuration gdm-configuration-xorg
                      (default (xorg-configuration)))
  (x-session gdm-configuration-x-session
             (default (xinitrc)))
  (wayland? gdm-configuration-wayland? (default #f))
  (wayland-session gdm-configuration-wayland-session
                   (default gdm-wayland-session-wrapper)))

(define (gdm-configuration-file config)
  (mixed-text-file "gdm-custom.conf"
                   "[daemon]\n"
                   "#User=gdm\n"
                   "#Group=gdm\n"
                   (if (gdm-configuration-auto-login? config)
                       (string-append
                        "AutomaticLoginEnable=true\n"
                        "AutomaticLogin="
                        (or (gdm-configuration-default-user config)
                            (error "missing default user for auto-login"))
                        "\n")
                       (string-append
                        "AutomaticLoginEnable=false\n"
                        "#AutomaticLogin=\n"))
                   "#TimedLoginEnable=false\n"
                   "#TimedLogin=\n"
                   "#TimedLoginDelay=0\n"
                   ;; Disable initial system setup inside GDM.
                   ;; Whatever settings are set there should already be
                   ;; taken care of through `guix system'.
                   ;; See also
                   ;; <https://debbugs.gnu.org/cgi/bugreport.cgi?bug=39281>.
                   "InitialSetupEnable=false\n"
                   "WaylandEnable=" (if (gdm-configuration-wayland? config)
                                        "true"
                                        "false") "\n"
                   "\n"
                   "[debug]\n"
                   "Enable=" (if (gdm-configuration-debug? config)
                                 "true"
                                 "false") "\n"
                   "\n"
                   "[security]\n"
                   "#DisallowTCP=true\n"
                   "#AllowRemoteAutoLogin=false\n"))

(define (gdm-pam-service config)
  "Return a PAM service for @command{gdm}."
  (list
   (pam-service
    (inherit (unix-pam-service "gdm-autologin"
                               #:login-uid? #t))
    (auth (list (pam-entry
                 (control "optional")
                 (module (file-append (gdm-configuration-gdm config)
                                      "/lib/security/pam_gdm.so")))
                (pam-entry
                 (control "sufficient")
                 (module "pam_permit.so")))))
   (pam-service
    (inherit (unix-pam-service "gdm-launch-environment"))
    (auth (list (pam-entry
                 (control "required")
                 (module "pam_permit.so")))))
   (unix-pam-service "gdm-password"
                     #:login-uid? #t
                     #:allow-empty-passwords?
                     (gdm-configuration-allow-empty-passwords? config))))

(define (gdm-shepherd-service config)
  (list (shepherd-service
         (documentation "Xorg display server (GDM)")
         (provision '(xorg-server))
         (requirement '(dbus-system user-processes host-name udev))
         (start #~(lambda ()
                    (fork+exec-command
                     (list #$(file-append (gdm-configuration-gdm config)
                                          "/bin/gdm"))
                     #:environment-variables
                     (list (string-append
                            "GDM_CUSTOM_CONF="
                            #$(gdm-configuration-file config))
                           (string-append
                            "GDM_DBUS_DAEMON="
                            #$(gdm-configuration-dbus-daemon config))
                           (string-append
                            "GDM_X_SERVER="
                            #$(xorg-wrapper
                               (gdm-configuration-xorg config)))
                           (string-append
                            "GDM_X_SESSION="
                            #$(gdm-configuration-x-session config))
                           (string-append
                            "XDG_DATA_DIRS="
                            ((lambda (ls) (string-join ls ":"))
                             (map (lambda (path)
                                    (string-append path "/share"))
                                  ;; XXX: Remove gnome-shell below when GDM
                                  ;; can depend on GNOME Shell directly.
                                  (cons #$gnome-shell
                                        '#$(gdm-configuration-gnome-shell-assets
                                            config)))))
                           ;; Add XCURSOR_PATH so that mutter can find its
                           ;; cursors.  gdm doesn't login so doesn't source
                           ;; the corresponding line in /etc/profile.
                           "XCURSOR_PATH=/run/current-system/profile/share/icons"
                           (string-append
                            "GDK_PIXBUF_MODULE_FILE="
                            #$gnome-shell "/" #$%gdk-pixbuf-loaders-cache-file)
                           (string-append
                            "GDM_WAYLAND_SESSION="
                            #$(gdm-configuration-wayland-session config))))))
         (stop #~(make-kill-destructor))
         (respawn? #t))))

(define gdm-service-type
  (handle-xorg-configuration gdm-configuration
    (service-type (name 'gdm)
                  (extensions
                   (list (service-extension shepherd-root-service-type
                                            gdm-shepherd-service)
                         (service-extension activation-service-type
                                            (const %gdm-activation))
                         (service-extension account-service-type
                                            (const %gdm-accounts))
                         (service-extension pam-root-service-type
                                            gdm-pam-service)
                         (service-extension profile-service-type
                                            gdm-configuration-gnome-shell-assets)
                         (service-extension dbus-root-service-type
                                            (compose list
                                                     gdm-configuration-gdm))
                         (service-extension localed-service-type
                                            (compose
                                             xorg-configuration-keyboard-layout
                                             gdm-configuration-xorg))))
                  (default-value (gdm-configuration))
                  (description
                   "Run the GNOME Desktop Manager (GDM), a program that allows
you to log in in a graphical session, whether or not you use GNOME."))))

;; Since GDM depends on Rust (gdm -> gnome-shell -> gjs -> mozjs -> rust)
;; and Rust is currently unavailable on non-x86_64 platforms, default to
;; SDDM there (FIXME).
(define* (set-xorg-configuration config
                                 #:optional
                                 (login-manager-service-type
                                  (let ((system (or (%current-target-system)
                                                    (%current-system))))
                                    (if (string-prefix? "x86_64" system)
                                        gdm-service-type
                                        sddm-service-type))))
  "Tell the log-in manager (of type @var{login-manager-service-type}) to use
@var{config}, an <xorg-configuration> record."
  (simple-service 'set-xorg-configuration
                  login-manager-service-type
                  config))

;;; xorg.scm ends here