New option `org-clock-auto-clockout-timer'

* etc/ORG-NEWS (New option ~org-clock-auto-clockout-timer~):
Mention the new option `org-clock-auto-clockout-timer'.

* doc/org-manual.org (Clocking out automatically after some
idle time): Document `org-clock-auto-clockout-timer'.

* lisp/org.el (org-clock-auto-clockout-insinuate): New
function to add a hook for auto-clocking out the current tasks
after `org-clock-auto-clockout-timer' seconds.

* lisp/org-clock.el (org-clock-auto-clockout-timer): New option.
(org-clock-auto-clockout): New function, use the new option.

doc/org-manual.org

@@ -6886,6 +6886,21 @@ If you only want this from time to time, use three universal prefix
 arguments with ~org-clock-in~ and two {{{kbd(C-u C-u)}}} with
 ~org-clock-in-last~.
 
+**** Clocking out automatically after some idle time
+:PROPERTIES:
+:UNNUMBERED: notoc
+:END:
+#+cindex: auto clocking out after idle time
+
+#+vindex: org-clock-auto-clockout-timer
+When you often forget to clock out before being idle and you don't
+want to manually set the clocking time to take into account, you can
+set ~org-clock-auto-clockout-timer~ to a number of seconds and add
+=(org-clock-auto-clockout-insinuate)= to your =.emacs= file.
+
+When the clock is running and Emacs is idle for more than this number
+of seconds, the clock will be clocked out automatically.
+
 ** Effort Estimates
 :PROPERTIES:
 :DESCRIPTION: Planning work effort in advance.

etc/ORG-NEWS

@@ -79,6 +79,15 @@ Babel Java blocks recognize header argument =:cmdargs= and pass its
 value in call to =java=.
 
 ** New options
+*** New option ~org-clock-auto-clockout-timer~
+
+When this option is set to a number and the user configuration
+contains =(org-clock-auto-clockout-insinuate)=, Org will clock out the
+currently clocked in task after that number of seconds of idle time.
+
+This is useful when you often forget to clock out before being idle
+and don't want to have to manually set the clocking time to take into
+account.
 
 *** New option ~org-table-header-line-p~
 

lisp/org-clock.el

@@ -468,6 +468,19 @@ Valid values are: `today', `yesterday', `thisweek', `lastweek',
 		 (const :tag "Select range interactively" interactive))
   :safe #'symbolp)
 
+(defcustom org-clock-auto-clockout-timer nil
+  "Timer for auto clocking out when Emacs is idle.
+When set to a number, auto clock out the currently clocked in
+task after this number of seconds of idle time.
+
+This is only effective when `org-clock-auto-clockout-insinuate'
+is added to the user configuration."
+  :group 'org-clock
+  :package-version '(Org . "9.4")
+  :type '(choice
+	  (integer :tag "Clock out after Emacs is idle for X seconds")
+	  (const :tag "Never auto clock out" nil)))
+
 (defvar org-clock-in-prepare-hook nil
   "Hook run when preparing the clock.
 This hook is run before anything happens to the task that
@@ -1397,6 +1410,17 @@ the default behavior."
 	 (message "Clock starts at %s - %s" ts org--msg-extra)
 	 (run-hooks 'org-clock-in-hook))))))
 
+(defun org-clock-auto-clockout ()
+  "Clock out the currently clocked in task if Emacs is idle.
+See `org-clock-auto-clockout-timer' to set the idle time span.
+
+Thie is only effective when `org-clock-auto-clockout-insinuate'
+is present in the user configuration."
+  (when (and (numberp org-clock-auto-clockout-timer)
+	     org-clock-current-task)
+    (run-with-idle-timer
+     org-clock-auto-clockout-timer nil #'org-clock-out)))
+
 ;;;###autoload
 (defun org-clock-in-last (&optional arg)
   "Clock in the last closed clocked item.

lisp/org.el

@@ -3766,6 +3766,14 @@ If yes, offer to stop it and to save the buffer with the changes."
   (add-hook 'org-mode-hook 'org-clock-load)
   (add-hook 'kill-emacs-hook 'org-clock-save))
 
+(defun org-clock-auto-clockout-insinuate ()
+  "Set up hook for auto clocking out when Emacs is idle.
+See `org-clock-auto-clockout-timer'.
+
+This function is meant to be added to the user configuration."
+  (require 'org-clock)
+  (add-hook 'org-clock-in-hook #'org-clock-auto-clockout t))
+
 (defgroup org-archive nil
   "Options concerning archiving in Org mode."
   :tag "Org Archive"