1;;; animate.el --- make text dance
2
3;; Copyright (C) 2001, 2002, 2003, 2004, 2005,
4;;   2006, 2007 Free Software Foundation, Inc.
5
6;; Maintainer: Richard Stallman <rms@gnu.org>
7;; Keywords: games
8
9;; This file is part of GNU Emacs.
10
11;; GNU Emacs is free software; you can redistribute it and/or modify
12;; it under the terms of the GNU General Public License as published by
13;; the Free Software Foundation; either version 2, or (at your option)
14;; any later version.
15
16;; GNU Emacs is distributed in the hope that it will be useful,
17;; but WITHOUT ANY WARRANTY; without even the implied warranty of
18;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
19;; GNU General Public License for more details.
20
21;; You should have received a copy of the GNU General Public License
22;; along with GNU Emacs; see the file COPYING.  If not, write to the
23;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
24;; Boston, MA 02110-1301, USA.
25
26;;; Commentary:
27
28;; (animate-string STRING VPOS &optional HPOS)
29;; makes the string STRING appear starting at VPOS, HPOS
30;; by having each letter swoop into place from random starting position.
31
32;; animate-birthday-present was the first application of this program.
33
34;;; Code:
35
36;;; STRING is the string to be displayed,
37;;; and DEST-X, DEST-Y say where on the screen
38;;; it should end up.
39
40;;; This function returns a list describing
41;;; all the characters and the paths they should take.
42;;; Each element has the form
43;;;  (CHAR START-Y START-X DEST-Y DEST-X).
44
45;;; The start position of each character is chosen randomly.
46;;; The destination is chosen to put it in the right place
47;;; in the string when the whole string finally reaches its
48;;; specified position.
49
50(defun animate-initialize (string vpos hpos)
51  (let ((characters nil))
52    (dotimes (i (length string))
53      (setq characters
54	    (cons (list (aref string i)
55			;; Random starting positions.
56			(random (window-height))
57			(random (1- (window-width)))
58			;; All the chars should end up
59			;; on the specified line.
60			vpos
61			;; The Ith character in the string
62			;; needs to end up I positions later.
63			(+ hpos i))
64		  characters)))
65    characters))
66
67;;; Display the characters in CHARACTERS,
68;;; each one FRACTION of the way from its start to its destination.
69;;; If FRACTION is 0, the characters appear in their starting positions.
70;;; If FRACTION is 1, the characters appear in their destinations.
71
72(defun animate-step (characters fraction)
73  (let ((remains (- 1 fraction)))
74    (dolist (item characters)
75      (let ((vpos (+ (* remains (nth 1 item))
76		     (* fraction (nth 3 item))))
77	    (hpos (+ (* remains (nth 2 item))
78		     (* fraction (nth 4 item)))))
79	(animate-place-char (car item) vpos hpos)))))
80
81;;; Place the character CHAR at position VPOS, HPOS in the current buffer.
82(defun animate-place-char (char vpos hpos)
83  (goto-char (window-start))
84  (let (abbrev-mode)
85    (dotimes (i vpos)
86      (end-of-line)
87      (if (= (forward-line 1) 1)
88	  (insert "\n"))))
89  (beginning-of-line)
90  (move-to-column (floor hpos) t)
91  (unless (eolp) (delete-char 1))
92  (insert-char char 1))
93
94(defvar animate-n-steps 10
95  "Number of steps to use `animate-string'.")
96
97;;;###autoload
98(defun animate-string (string vpos &optional hpos)
99  "Display STRING starting at position VPOS, HPOS, using animation.
100The characters start at randomly chosen places,
101and all slide in parallel to their final positions,
102passing through `animate-n-steps' positions before the final ones.
103If HPOS is nil (or omitted), center the string horizontally
104in the current window."
105  (let ((characters
106	 (animate-initialize string vpos
107			     (or hpos
108				 ;; HPOS unspecified, so compute
109				 ;; it so as to center the string.
110				 (max 0 (/ (- (window-width) (length string)) 2))))))
111    (dotimes (i animate-n-steps)
112      ;; Bind buffer-undo-list so it will be unchanged when we are done.
113      ;; (We're going to undo all our changes anyway.)
114      (let (buffer-undo-list
115	    list-to-undo)
116	;; Display the characters at the Ith position.
117	;; This inserts them in the buffer.
118	(animate-step characters (/ i 1.0 animate-n-steps))
119	;; Make sure buffer is displayed starting at the beginning.
120	(set-window-start nil 1)
121	;; Display it, and wait just a little while.
122	(sit-for .05)
123	;; Now undo the changes we made in the buffer.
124	(setq list-to-undo buffer-undo-list)
125	(while list-to-undo
126	  (let ((undo-in-progress t))
127	    (setq list-to-undo (primitive-undo 1 list-to-undo))))))
128    ;; Insert the characters in their final positions.
129    (animate-step characters 1)
130    ;; Put the cursor at the end of the text on the line.
131    (end-of-line)
132    ;; Redisplay so they appear on the screen there.
133    (sit-for 0)
134    ;; This is so that the undo command, used afterwards,
135    ;; will undo the "animate" calls one by one.
136    (undo-boundary)))
137
138;;;###autoload
139(defun animate-sequence (list-of-strings space)
140  "Display strings from LIST-OF-STRING with animation in a new buffer.
141Strings will be separated from each other by SPACE lines."
142  (let ((vpos (/ (- (window-height)
143		    1 ;; For the mode-line
144		    (* (1- (length list-of-strings)) space)
145		    (length list-of-strings))
146		 2)))
147    (switch-to-buffer (get-buffer-create "*Animation*"))
148    (erase-buffer)
149    (sit-for 0)
150    (setq indent-tabs-mode nil)
151    (while list-of-strings
152      (animate-string (car list-of-strings) vpos)
153      (setq vpos (+ vpos space 1))
154      (setq list-of-strings (cdr list-of-strings)))))
155
156;;;###autoload
157(defun animate-birthday-present (&optional name)
158  "Display one's birthday present in a new buffer.
159You can specify the one's name by NAME; the default value is \"Sarah\"."
160  (interactive (list (read-string "Name (default Sarah): "
161				  nil nil "Sarah")))
162  ;; Make a suitable buffer to display the birthday present in.
163  (switch-to-buffer (get-buffer-create (format "*%s*" name)))
164  (erase-buffer)
165  ;; Display the empty buffer.
166  (sit-for 0)
167  ;; Make sure indentation does not use tabs.
168  ;; They would confuse things.
169  (setq indent-tabs-mode nil)
170
171  (animate-string "Happy Birthday," 6)
172  (animate-string (format "%s" name) 7)
173
174  (sit-for 1)
175
176  (animate-string "You are my sunshine," 10 30)
177  (sit-for .5)
178  (animate-string "My only sunshine." 11 30)
179  (sit-for .5)
180  (animate-string "I'm awful sad that" 12 30)
181  (sit-for .5)
182  (animate-string "You've moved away." 13 30)
183  (sit-for .5)
184  (animate-string "Let's talk together" 15 30)
185  (sit-for .5)
186  (animate-string "And love more deeply." 16 30)
187  (sit-for .5)
188  (animate-string "Please bring back" 17 30)
189  (animate-string "my sunshine" 18 34)
190  (animate-string "to stay!" 19 34))
191
192(random t)
193
194(provide 'animate)
195
196;;; arch-tag: 275289a3-6ac4-41da-b527-a1147045392f
197;;; animate.el ends here
198