This config not works. It causes error on building xserver:
'ERROR: In procedure scm-error:
In procedure for-each: Wrong type argument: "Section \"InputClass\"\n        Identifier \"touchpad\"\n        Driver \"libinput\"\n        MatchIsTouchpad \"on\"\n        Option \"Tapping\" \"on\"\nEndSection"'

====
  (services (cons*  
                    ;;(service postgresql-service-type)
                    (service xfce-desktop-service-type)
                    (modify-services      
                      ;;(remove (lambda (service)
                      ;;  (eq? (service-kind service)
                      ;;    wpa-supplicant-service-type))
                      ;;  (remove (lambda (service)
                      ;;    (eq? (service-kind service)
                      ;;      static-networking-service-type))
                          (remove (lambda (service)
                            (eq? (service-kind service)
                              ntp-service-type))
                            (remove (lambda (service)
                              (eq? (service-kind service)
                                avahi-service-type))
                              (modify-services %desktop-services

                                (slim-service-type config =>
                                              (slim-configuration
                                               (xorg-configuration
                                                 (xorg-configuration
                                                  (extra-config
                                                  
"Section \"InputClass\"
        Identifier \"touchpad\"
        Driver \"libinput\"
        MatchIsTouchpad \"on\"
        Option \"Tapping\" \"on\"
EndSection"
                                 )))))
  )  ;end of modify-services 2nd


                            )  ;end of remove avahi
                          )  ;end of remove2 ntp
                        ;;)  ;end of remove3 networking
                      ;)  ;end of remove4 wpa-supplicant
                      (elogind-service-type
                        c => (elogind-configuration (handle-lid-switch 'ignore)))
                    );;end of modify-services 1st desktop-services
  ));;end of services
====


I've found with `info guix` this:

 Let’s say you want your system to use the Turkish keyboard layout
throughout your system—bootloader, console, and Xorg.  Here’s what your
system configuration would look like:

     ;; Using the Turkish layout for the bootloader, the console,
     ;; and for Xorg.

     (operating-system
       ;; ...
       (keyboard-layout (keyboard-layout "tr"))  ;for the console
       (bootloader (bootloader-configuration
                     (bootloader grub-efi-bootloader)
                     (target "/boot/efi")
                     (keyboard-layout keyboard-layout))) ;for GRUB
       (services (modify-services %desktop-services
                   (slim-service-type config =>
                     (slim-configuration
                       (inherit config)
                       (xorg-configuration
                         (xorg-configuration             ;for Xorg
                           (keyboard-layout keyboard-layout))))))))

   In the example above, for GRUB and for Xorg, we just refer to the
‘keyboard-layout’ field defined above, but we could just as well refer
to a different layout.


But word 'touchpad' absents in `ingo guix`. I do not know what to do.



Mar 27, 2019, 6:12 PM by rekado@elephly.net:

>
> znavko@tutanota.com <mailto:znavko@tutanota.com>>  writes:
>
>> Now yes, but I think it is old, cause startx rests there in slim
>> config:
>> https://www.gnu.org/software/guix/manual/en/guix.html#index-slim_002dconfiguration <https://www.gnu.org/software/guix/manual/en/guix.html#index-slim_002dconfiguration>
>>
>
> A copy of the manual that matches the version of Guix you have installed
> comes with Guix itself.  I suggest using that up-to-date manual instead
> of the manual on the web which matches the latest release.
>
> You can access the manual with “info guix” on the command line (or with
> the equivalent in Emacs, which has a much better info reader).  Hit “i”
> for the index and type “slim-configuration” because that’s what the
> error says has an error.
>
> There you’ll find that “slim-configuration” no longer has a “startx”
> field, but instead offers an “xorg-configuration” field.  So we hit “i”
> again and type “xorg-configuration” to get more information about the
> valid values…
>
> The only reason why you passed a value for “startx” originally was just
> to pass an Xorg configuration snippet via “#:extra-config”.  According
> to the manual for “xorg-configuration” you can now do this directly via
> the “extra-config” field of the “xorg-configuration” record.
>
> So you’ll probably end up with something like this:
>
> (service slim-service-type
>  (slim-configuration
>  (xorg-configuration
>  (xorg-configuration
>  (extra-config "…")))))
>
>
> --
> Ricardo
>