1;;; later-do.el --- execute lisp code ... later
2
3;; Copyright (C) 2004, 2005, 2006, 2007, 2008,
4;;   2009, 2018 Free Software Foundation, Inc.
5
6;; Author: Jorgen Schaefer <forcer@forcix.cx>
7
8;;; This program is free software; you can redistribute it and/or
9;;; modify it under the terms of the GNU General Public License
10;;; as published by the Free Software Foundation; either version 3
11;;; of the License, or (at your option) any later version.
12
13;;; This program is distributed in the hope that it will be useful,
14;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
15;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16;;; GNU General Public License for more details.
17
18;;; You should have received a copy of the GNU General Public License
19;;; along with this program; if not, write to the Free Software
20;;; Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
21;;; 02110-1301 USA
22
23;;; Commentary
24
25;; This file will execute lisp code ``later on''.  This way it is
26;; possible to work while elisp does some longer calculations, if you
27;; can convert those calculations into a sequence of function calls.
28
29;;; Code:
30
31(defvar later-do-version "0.2emms4 (2018-04-07)"
32  "Version string of later-do.")
33
34(defgroup later-do nil
35  "*Running functions ... later!"
36  :prefix "later-do-"
37  :group 'development)
38
39(defcustom later-do-interval 0.5
40  "How many seconds to wait between running events."
41  :group 'later-do
42  :type 'number)
43
44(defcustom  later-do-batch 20
45  "How many functions to process before waiting `later-do-interval'.
46The functions are processed from `later-do-list'.  Must be 1 or
47greater.  Too high a value might make Emacs slower while the
48list is being processed."
49  :group 'later-do
50  :type 'number)
51
52(defvar later-do-list nil
53  "A list of functions to be called later on.")
54
55(defvar later-do-timer nil
56  "The timer that later-do uses.")
57
58(defun later-do (function &rest args)
59  "Apply FUNCTION to ARGS later on.  This is an unspecified
60amount of time after this call, and definitely not while lisp is
61still executing.  Code added using `later-do' is guaranteed to be
62executed in the sequence it was added."
63  (setq later-do-list (nconc later-do-list
64                              (list (cons function args))))
65  (unless later-do-timer
66    (setq later-do-timer
67          (run-with-timer later-do-interval nil 'later-do-timer))))
68
69(defun later-do-timer ()
70  "Run the next element in `later-do-list', or do nothing if it's
71empty."
72  (if (null later-do-list)
73      (setq later-do-timer nil)
74    (let (res)
75      (unwind-protect
76          (dotimes (b (min later-do-batch (length later-do-list)) res)
77            (let ((fun (caar later-do-list))
78                  (args (cdar later-do-list)))
79              (setq later-do-list (cdr later-do-list))
80              (setq res (apply fun args)))))
81      (setq later-do-timer (run-with-timer later-do-interval
82                                           nil
83                                           'later-do-timer)))))
84
85(provide 'later-do)
86;;; later-do.el ends here
87