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;;; animate.el --- make text dance -*- lexical-binding:t -*-
;; Copyright (C) 2001-2025 Free Software Foundation, Inc.
;; Maintainer: Richard Stallman <rms@gnu.org>
;; Keywords: games
;; This file is part of GNU Emacs.
;; GNU Emacs 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.
;; GNU Emacs 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 GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;; (animate-string STRING VPOS &optional HPOS)
;; makes the string STRING appear starting at VPOS, HPOS
;; by having each letter swoop into place from random starting position.
;; animate-birthday-present was the first application of this program.
;;; Code:
;;; STRING is the string to be displayed,
;;; and DEST-X, DEST-Y say where on the screen
;;; it should end up.
;;; This function returns a list describing
;;; all the characters and the paths they should take.
;;; Each element has the form
;;; (CHAR START-Y START-X DEST-Y DEST-X).
;;; The start position of each character is chosen randomly.
;;; The destination is chosen to put it in the right place
;;; in the string when the whole string finally reaches its
;;; specified position.
(defgroup animate nil
"Make text dance."
:group 'games
:prefix "animate-")
(defun animate-initialize (string vpos hpos)
(let ((characters nil))
(dotimes (i (length string))
(setq characters
(cons (list (aref string i)
;; Random starting positions.
(random (window-height))
(random (1- (window-width)))
;; All the chars should end up
;; on the specified line.
vpos
;; The Ith character in the string
;; needs to end up I positions later.
(+ hpos i))
characters)))
characters))
;;; Display the characters in CHARACTERS,
;;; each one FRACTION of the way from its start to its destination.
;;; If FRACTION is 0, the characters appear in their starting positions.
;;; If FRACTION is 1, the characters appear in their destinations.
(defun animate-step (characters fraction)
(let ((remains (- 1 fraction)))
(dolist (item characters)
(let ((vpos (+ (* remains (nth 1 item))
(* fraction (nth 3 item))))
(hpos (+ (* remains (nth 2 item))
(* fraction (nth 4 item)))))
(animate-place-char (car item) vpos hpos)))))
;;; Place the character CHAR at position VPOS, HPOS in the current buffer.
(defun animate-place-char (char vpos hpos)
(goto-char (window-start))
(let (abbrev-mode)
(dotimes (_ vpos)
(end-of-line)
(if (= (forward-line 1) 1)
(insert "\n"))))
(beginning-of-line)
(move-to-column (floor hpos) t)
(unless (eolp) (delete-char 1))
(insert-char char 1))
(defcustom animate-n-steps 20
"Number of steps `animate-string' will place a char before its last position."
:type 'natnum
:version "29.1")
(defcustom animate-total-added-delay 0.5
"Total number of seconds to wait in between steps.
This is added to the total time it takes to run `animate-string'
to ensure that the animation is not too fast to be seen."
:type 'float
:version "29.1")
(defvar animation-buffer-name nil
"String naming the default buffer for animations.
When nil animations displayed in the buffer named *Animation*.")
;;;###autoload
(defun animate-string (string vpos &optional hpos)
"Display STRING animations starting at position VPOS, HPOS.
The characters start at randomly chosen places,
and all slide in parallel to their final positions,
passing through `animate-n-steps' positions before the final ones.
If HPOS is nil (or omitted), center the string horizontally
in the current window."
(let ((characters
(animate-initialize string vpos
(or hpos
;; HPOS unspecified, so compute
;; it so as to center the string.
(max 0 (/ (- (window-width) (length string)) 2)))))
(show-trailing-whitespace nil)
;; Make sure indentation does not use tabs.
;; They would confuse things.
(indent-tabs-mode nil))
(dotimes (i animate-n-steps)
;; Bind buffer-undo-list so it will be unchanged when we are done.
;; (We're going to undo all our changes anyway.)
(let (buffer-undo-list
list-to-undo)
;; Display the characters at the Ith position.
;; This inserts them in the buffer.
(animate-step characters (/ i 1.0 animate-n-steps))
;; Make sure buffer is displayed starting at the beginning.
(set-window-start nil 1)
;; Display it, and wait just a little while.
(sit-for (/ (float animate-total-added-delay) (max animate-n-steps 1)))
;; Now undo the changes we made in the buffer.
(setq list-to-undo buffer-undo-list)
(while list-to-undo
(let ((undo-in-progress t))
(setq list-to-undo (primitive-undo 1 list-to-undo))))))
;; Insert the characters in their final positions.
(animate-step characters 1)
;; Put the cursor at the end of the text on the line.
(end-of-line)
;; Redisplay so they appear on the screen there.
(sit-for 0)
;; This is so that the undo command, used afterwards,
;; will undo the "animate" calls one by one.
(undo-boundary)))
;;;###autoload
(defun animate-sequence (list-of-strings space)
"Display animation strings from LIST-OF-STRING with buffer *Animation*.
Strings will be separated from each other by SPACE lines.
When the variable `animation-buffer-name' is non-nil display
animation in the buffer named by variable's value, creating the
buffer if one does not exist."
(let ((vpos (/ (- (window-height)
1 ;; For the mode-line
(* (1- (length list-of-strings)) space)
(length list-of-strings))
2)))
(switch-to-buffer (get-buffer-create
(or animation-buffer-name
"*Animation*")))
(erase-buffer)
(sit-for 0)
(while list-of-strings
(animate-string (car list-of-strings) vpos)
(setq vpos (+ vpos space 1))
(setq list-of-strings (cdr list-of-strings)))))
;;;###autoload
(defun animate-birthday-present (&optional name)
"Return a birthday present in the buffer *Birthday-Present*.
When optional arg NAME is non-nil or called-interactively, prompt for
NAME of birthday present receiver and return a birthday present in
the buffer *Birthday-Present-for-Name*."
(interactive (list (read-string "Birthday present for: "
nil nil)))
;; Make a suitable buffer to display the birthday present in.
(switch-to-buffer (get-buffer-create
(if name
(concat "*A-Present-for-" (capitalize name) "*")
"*Birthday-Present*")))
(erase-buffer)
;; Display the empty buffer.
(sit-for 0)
(if name
(animate-string "Happy Birthday," 6)
(animate-string "Happy Birthday" 6))
(when name (animate-string (format "%s" (capitalize name)) 7))
(sit-for 1)
(animate-string "You are my sunshine," 10 30)
(sit-for .5)
(animate-string "My only sunshine." 11 30)
(sit-for .5)
(animate-string "I'm awful sad that" 12 30)
(sit-for .5)
(animate-string "You've moved away." 13 30)
(sit-for .5)
(animate-string "Let's talk together" 15 30)
(sit-for .5)
(animate-string "And love more deeply." 16 30)
(sit-for .5)
(animate-string "Please bring back" 17 30)
(animate-string "my sunshine" 18 34)
(animate-string "to stay!" 19 34))
(provide 'animate)
;;; animate.el ends here
|
