Add basic D-Bus integration to Gnus

* lisp/gnus/gnus-dbus.el: New library, registering a signal that
closes all Gnus servers when the system is going to sleep.
* lisp/gnus/gnus-start.el: Check new option
`gnus-dbus-close-on-sleep', and register the appropriate D-Bus signal
if it is non-nil.
* lisp/gnus/gnus.el: New gnus-dbus customization group.
* doc/misc/gnus.texi: Document.

doc/misc/gnus.texi

@@ -828,6 +828,7 @@ Various
 * Spam Package::                A package for filtering and processing spam.
 * The Gnus Registry::           A package for tracking messages by Message-ID.
 * The Gnus Cloud::              A package for synchronizing Gnus marks.
+* D-Bus Integration::           Closing Gnus servers on system sleep.
 * Other modes::                 Interaction with other modes.
 * Various Various::             Things that are really various.
 
@@ -22333,6 +22334,7 @@ to you, using @kbd{G b u} and updating the group will usually fix this.
 * Spam Package::                A package for filtering and processing spam.
 * The Gnus Registry::           A package for tracking messages by Message-ID.
 * The Gnus Cloud::              A package for synchronizing Gnus marks.
+* D-Bus Integration::           Closing Gnus servers on system sleep.
 * Other modes::                 Interaction with other modes.
 * Various Various::             Things that are really various.
 @end menu
@@ -26404,6 +26406,26 @@ CloudSynchronizationDataPack(TM)s. It's easiest to set this from the
 Server buffer (@pxref{Gnus Cloud Setup}).
 @end defvar
 
+@node D-Bus Integration
+@section D-Bus Integration
+@cindex dbus
+@cindex D-Bus
+@cindex gnus-dbus
+@cindex system sleep
+@cindex closing servers automatically
+@cindex hung connections
+
+When using laptops or other systems that have a sleep or hibernate
+functionality, it's possible for long-running server connections to
+become ``hung'', requiring the user to manually close and re-open the
+connections after the system resumes.  On systems compiled with D-Bus
+support (check the value of @code{(featurep 'dbusbind)}), Gnus can
+register a D-Bus signal to automatically close all server connections
+before the system goes to sleep.  To enable this, set
+@code{gnus-dbus-close-on-sleep} to a non-nil value.
+
+For more information about D-Bus and Emacs, @pxref{Top,,, dbus, D-Bus integration in Emacs}.
+
 @node Other modes
 @section Interaction with other modes
 

etc/NEWS

@@ -295,6 +295,11 @@ tags to be considered as well.
 
 ** Gnus
 
++++
+*** New option 'gnus-dbus-close-on-sleep'
+On systems with D-Bus support, it is now possible to register a signal
+to close all Gnus servers before the system sleeps.
+
 +++
 *** The key binding of 'gnus-summary-search-article-forward' has changed.
 This command was previously on 'M-s' and shadowed the global 'M-s'

lisp/gnus/gnus-dbus.el

@@ -0,0 +1,68 @@
+;;; gnus-dbus.el --- DBUS integration for Gnus       -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2020  Free Software Foundation, Inc.
+
+;; Author: Eric Abrahamsen <eric@ericabrahamsen.net>
+
+;; This program 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.
+
+;; This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This library contains some Gnus integration for systems using DBUS.
+;; At present it registers a signal to close all Gnus servers before
+;; system sleep or hibernation.
+
+;;; Code:
+
+(require 'gnus)
+(require 'dbus)
+(declare-function gnus-close-all-servers "gnus-start")
+
+(defcustom gnus-dbus-close-on-sleep nil
+  "When non-nil, close Gnus servers on system sleep."
+  :group 'gnus-dbus
+  :type 'boolean)
+
+(defvar gnus-dbus-sleep-registration-object nil
+  "Object returned from `dbus-register-signal'.
+Used to unregister the signal.")
+
+(defun gnus-dbus-register-sleep-signal ()
+  "Use `dbus-register-signal' to close servers on sleep."
+  (when (featurep 'dbusbind)
+    (setq gnus-dbus-sleep-registration-object
+	  (dbus-register-signal :session
+				"org.freedesktop.login1"
+				"/org/freedesktop/login1"
+				"org.freedesktop.login1.Manager"
+				"PrepareForSleep"
+				#'gnus-dbus-sleep-handler))
+    (gnus-add-shutdown #'gnus-dbus-unregister-sleep-signal 'gnus)))
+
+(defun gnus-dbus-sleep-handler (sleep-start)
+  ;; Sleep-start is t before sleeping.
+  (when (and sleep-start
+	     (gnus-alive-p))
+    (condition-case nil
+	(gnus-close-all-servers)
+      (error nil))))
+
+(defun gnus-dbus-unregister-sleep-signal ()
+  (condition-case nil
+      (dbus-unregister-object
+       gnus-dbus-sleep-registration-object)
+    (wrong-type-argument nil)))
+
+(provide 'gnus-dbus)
+;;; gnus-dbus.el ends here

lisp/gnus/gnus-start.el

@@ -31,6 +31,7 @@
 (require 'gnus-range)
 (require 'gnus-util)
 (require 'gnus-cloud)
+(require 'gnus-dbus)
 (autoload 'message-make-date "message")
 (autoload 'gnus-agent-read-servers-validate "gnus-agent")
 (autoload 'gnus-agent-save-local "gnus-agent")
@@ -798,6 +799,8 @@ prompt the user for the name of an NNTP server to use."
 	  (gnus-run-hooks 'gnus-setup-news-hook)
 	  (when gnus-agent
 	    (gnus-request-create-group "queue" '(nndraft "")))
+	  (when gnus-dbus-close-on-sleep
+	    (gnus-dbus-register-sleep-signal))
 	  (gnus-start-draft-setup)
 	  ;; Generate the group buffer.
 	  (gnus-group-list-groups level)

lisp/gnus/gnus.el

@@ -292,6 +292,10 @@ is restarted, and sometimes reloaded."
   :link '(custom-manual "(gnus)Exiting Gnus")
   :group 'gnus)
 
+(defgroup gnus-dbus nil
+  "D-Bus integration for Gnus."
+  :group 'gnus)
+
 (defconst gnus-version-number "5.13"
   "Version number for this version of Gnus.")