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#76667
[PATCH] gnu: home: services: Add 'wayland-display' service.
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* gnu/home/services/desktop.scm (wayland-shepherd-service): New procedure.
(home-wayland-service-type): New variable.
* doc/guix.texi (Desktop Home Services): Document it.
Change-Id: Iab6be6cda732e30213bdddcb5c9a7e53814585d0
---
doc/guix.texi | 36 ++++++++++++++++
gnu/home/services/desktop.scm | 79 +++++++++++++++++++++++++++++++++++
2 files changed, 115 insertions(+)
diff --git a/doc/guix.texi b/doc/guix.texi
index bb5f29277f..36b86cffe1 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -47839,6 +47839,42 @@ In the example above, @code{x11-display} is instructed to set
@env{DISPLAY} to @code{:3}.
@end defvar
+@defvar home-wayland-service-type
+This is the service type representing a Wayland compositor. It
+functions as an equivalent of @code{x11-service-type} for Wayland.
+
+Like X11, Wayland compositors are started by services like
+@code{gdm-service-type}, described in the system configuration. At the
+level of Guix Home, as an unprivileged user, we cannot start our Wayland
+compositor; 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-wayland-service-type}. Services that require an Wayland
+graphical display instantiate this service and depend on its
+corresponding @code{wayland-display} Shepherd service (@pxref{Shepherd
+Home Service}).
+
+If you're writing a Shepherd service that requires the presence of a
+Wayland compositor, you need to depend on this service to ensure Wayland
+is accessible from your service.
+
+When the Wayland compositor is running, the @code{wayland-display}
+Shepherd service starts and sets the @env{WAYLAND_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{WAYLAND_DISPLAY}, like so:
+
+@example
+herd start wayland-display wayland-2
+@end example
+
+In the example above, @code{wayland-display} is instructed to set
+@env{WAYLAND_DISPLAY} to @code{wayland-2}.
+@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
diff --git a/gnu/home/services/desktop.scm b/gnu/home/services/desktop.scm
index fc96ce9295..d12014f997 100644
--- a/gnu/home/services/desktop.scm
+++ b/gnu/home/services/desktop.scm
@@ -33,6 +33,8 @@ (define-module (gnu home services desktop)
#:use-module (ice-9 match)
#:export (home-x11-service-type
+ home-wayland-service-type
+
home-redshift-configuration
home-redshift-configuration?
home-redshift-service-type
@@ -121,6 +123,83 @@ (define home-x11-service-type
during that time, the @code{x11-display} service is marked as failing to
start.")))
+
+;;;
+;;; Waiting for Wayland.
+;;;
+
+(define (wayland-shepherd-service delay)
+ (list (shepherd-service
+ (provision '(wayland-display))
+ (modules '((ice-9 ftw)
+ (ice-9 regex)
+ (ice-9 match)
+ (srfi srfi-1)
+ (shepherd support)))
+ (start
+ #~(lambda* (#:optional (env-wayland-display (getenv "WAYLAND_DISPLAY")))
+
+ (define wayland-socket-regex "wayland-[0-9]+$")
+
+ (define (find-socket directory regex)
+ (find (match-lambda
+ ((or "." "..") #f)
+ (name
+ (let ((name (in-vicinity directory
+ name)))
+ (and (string-match regex name)
+ (access? name O_RDWR)))))
+ ;; Wayland names its sockets ‘wayland-n’. With
+ ;; ‘reverse’, we pick up on the last Wayland instance
+ ;; created (essentially what we always want to do).
+ (or (reverse (scandir directory)) '())))
+
+ (define (find-display delay)
+ (let loop ((attempts delay))
+
+ (define wayland-display
+ (or env-wayland-display
+ (find-socket %user-runtime-dir "wayland-[0-9]+$")))
+
+ (unless wayland-display
+ (unless (zero? attempts)
+ (sleep 1)
+ (loop (- attempts 1)))
+
+ (format (current-error-port)
+ "Wayland server did not show up; giving up.\n"))
+
+ wayland-display))
+
+ (when wayland-display
+ (format #t "Wayland display found at ~s.~%" wayland-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 "WAYLAND_DISPLAY" wayland-display))
+
+ wayland-display))
+
+ (stop #~(lambda (_)
+ (unsetenv "WAYLAND_DISPLAY")
+ #f))
+ (respawn? #f))))
+
+(define home-wayland-service-type
+ (service-type
+ (name 'home-wayland-display)
+ (extensions (list (service-extension home-shepherd-service-type
+ wayland-shepherd-service)))
+ (default-value 10)
+ (description
+ "Create a @code{wayland-display} Shepherd service that waits for a Wayland
+compositor to be up and running, up to a configurable delay, and sets the
+@code{WAYLAND_DISPLAY} environment variable of @command{shepherd} itself
+accordingly. If no accessible Wayland server shows up during that time, the
+@code{wayland-display} service is marked as failing to start.")))
+
;;;
;;; Redshift.
--
2.48.1
This bug report was last modified 104 days ago.
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