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home: services: Add 'x11-display' service.

* gnu/home/services/desktop.scm (x11-shepherd-service): New procedure.
(home-x11-service-type): New variable.
(redshift-shepherd-service): Add 'requirement' field.
(home-redshift-service-type): Extend 'home-x11-service-type'.
* doc/guix.texi (Desktop Home Services): Document it.

Change-Id: Ibd46d71cbb80fcdff8dbf3e8dbcfc3b24163bdb6
Ludovic Courtès 2023-08-16 19:37:25 +02:00
parent 331d858e21
commit 08d94fe20e
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GPG Key ID: 090B11993D9AEBB5
2 changed files with 135 additions and 8 deletions

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@ -44475,6 +44475,40 @@ The @code{(gnu home services desktop)} module provides services that you
may find useful on ``desktop'' systems running a graphical user
environment such as Xorg.
@cindex X Window, for Guix Home services
@cindex X11, in Guix Home
@defvar home-x11-service-type
This is the service type representing the X Window graphical display
server (also referred to as ``X11'').
X Window is necessarily started by a system service; on Guix System,
starting it is the responsibility of @code{gdm-service-type} and similar
services (@pxref{X Window}). At the level of Guix Home, as an
unprivileged user, we cannot start X Window; all we can do is check
whether it is running. This is what this service does.
As a user, you probably don't need to worry or explicitly instantiate
@code{home-x11-service-type}. Services that require an X Window
graphical display, such as @code{home-redshift-service-type} below,
instantiate it and depend on its corresponding @code{x11-display}
Shepherd service (@pxref{Shepherd Home Service}).
When X Window is running, the @code{x11-display} Shepherd service starts
and sets the @env{DISPLAY} environment variable of the
@command{shepherd} process, using its original value if it was already
set; otherwise, it fails to start.
The service can also be forced to use a given value for @env{DISPLAY},
like so:
@example
herd start x11-display :3
@end example
In the example above, @code{x11-display} is instructed to set
@env{DISPLAY} to @code{:3}.
@end defvar
@defvar home-redshift-service-type
This is the service type for @uref{https://github.com/jonls/redshift,
Redshift}, a program that adjusts the display color temperature

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@ -1,5 +1,5 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2022 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2022-2023 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2022 ( <paren@disroot.org>
;;; Copyright © 2023 conses <contact@conses.eu>
;;; Copyright © 2023 Janneke Nieuwenhuizen <janneke@gnu.org>
@ -30,7 +30,9 @@
#:use-module (guix gexp)
#:use-module (srfi srfi-1)
#:use-module (ice-9 match)
#:export (home-redshift-configuration
#:export (home-x11-service-type
home-redshift-configuration
home-redshift-configuration?
home-redshift-service-type
@ -43,6 +45,79 @@
home-xmodmap-configuration
home-xmodmap-service-type))
;;;
;;; Waiting for X11.
;;;
(define (x11-shepherd-service delay)
(list (shepherd-service
(provision '(x11-display))
(modules '((ice-9 ftw)
(ice-9 match)
(srfi srfi-1)))
(start
#~(lambda* (#:optional (display (getenv "DISPLAY")))
(define x11-directory
"/tmp/.X11-unix")
(define (find-display delay)
;; Wait for an accessible socket to show up in X11-DIRECTORY,
;; up to DELAY seconds.
(let loop ((attempts delay))
(define socket
(find (match-lambda
((or "." "..") #f)
(name
(let ((name (in-vicinity x11-directory
name)))
(access? name O_RDWR))))
(or (scandir x11-directory) '())))
(if (and socket (string-prefix? "X" socket))
(let ((display (string-append
":" (string-drop socket 1))))
(format #t "X11 display server found at ~s.~%"
display)
display)
(if (zero? attempts)
(begin
(format (current-error-port)
"X11 display server did not show up; \
giving up.\n")
#f)
(begin
(sleep 1)
(loop (- attempts 1)))))))
(let ((display (or display (find-display #$delay))))
(when display
;; Note: 'make-forkexec-constructor' calls take their
;; default #:environment-variables value before this service
;; is started and are thus unaffected by the 'setenv' call
;; below. Users of this service have to explicitly query
;; its value.
(setenv "DISPLAY" display))
display)))
(stop #~(lambda (_)
(unsetenv "DISPLAY")
#f))
(respawn? #f))))
(define home-x11-service-type
(service-type
(name 'home-x11-display)
(extensions (list (service-extension home-shepherd-service-type
x11-shepherd-service)))
(default-value 10)
(description
"Create a @code{x11-display} Shepherd service that waits for the X
Window (or ``X11'') graphical display server to be up and running, up to a
configurable delay, and sets the @code{DISPLAY} environment variable of
@command{shepherd} itself accordingly. If no accessible X11 server shows up
during that time, the @code{x11-display} service is marked as failing to
start.")))
;;;
;;; Redshift.
@ -169,11 +244,25 @@ format."))
(list (shepherd-service
(documentation "Redshift program.")
(provision '(redshift))
;; FIXME: This fails to start if Home is first activated from a
;; non-X11 session.
(start #~(make-forkexec-constructor
(list #$(file-append (home-redshift-configuration-redshift config) "/bin/redshift")
"-c" #$config-file)))
;; Depend on 'x11-display', which sets 'DISPLAY' if an X11 server is
;; available, and fails to start otherwise.
(requirement '(x11-display))
(modules '((srfi srfi-1)
(srfi srfi-26)))
(start #~(lambda _
(fork+exec-command
(list #$(file-append
(home-redshift-configuration-redshift config)
"/bin/redshift")
"-c" #$config-file)
;; Inherit the 'DISPLAY' variable set by 'x11-display'.
#:environment-variables
(cons (string-append "DISPLAY=" (getenv "DISPLAY"))
(remove (cut string-prefix? "DISPLAY=" <>)
(default-environment-variables))))))
(stop #~(make-kill-destructor))
(actions (list (shepherd-configuration-action config-file))))))
@ -181,7 +270,11 @@ format."))
(service-type
(name 'home-redshift)
(extensions (list (service-extension home-shepherd-service-type
redshift-shepherd-service)))
redshift-shepherd-service)
;; Ensure 'home-x11-service-type' is instantiated so we
;; can depend on the Shepherd 'x11-display' service.
(service-extension home-x11-service-type
(const #t))))
(default-value (home-redshift-configuration))
(description
"Run Redshift, a program that adjusts the color temperature of display