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comparison lisp/prim/reposition.el @ 0:376386a54a3c r19-14

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date Mon, 13 Aug 2007 08:45:50 +0200
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1 ;;; reposition.el --- center a Lisp function or comment on the screen
2
3 ;; Copyright (C) 1991, 1994 Free Software Foundation, Inc.
4
5 ;; Author: Michael D. Ernst <mernst@theory.lcs.mit.edu>
6 ;; Created: Jan 1991
7 ;; Maintainer: FSF
8
9 ;; This file is part of XEmacs.
10
11 ;; XEmacs is free software; you can redistribute it and/or modify it
12 ;; 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 ;; XEmacs is distributed in the hope that it will be useful, but
17 ;; WITHOUT ANY WARRANTY; without even the implied warranty of
18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19 ;; General Public License for more details.
20
21 ;; You should have received a copy of the GNU General Public License
22 ;; along with XEmacs; see the file COPYING. If not, write to the Free
23 ;; Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
24
25 ;;; Synched up with: FSF 19.30.
26
27 ;;; Commentary:
28
29 ;;; Reposition-window makes an entire function definition or comment visible,
30 ;;; or, if it is already visible, places it at the top of the window;
31 ;;; additional invocations toggle the visibility of comments preceding the
32 ;;; code. For the gory details, see the documentation for reposition-window;
33 ;;; rather than reading that, you may just want to play with it.
34
35 ;;; This tries pretty hard to do the recentering correctly; the precise
36 ;;; action depends on what the buffer looks like. If you find a situation
37 ;;; where it doesn't behave well, let me know. This function is modeled
38 ;;; after one of the same name in ZMACS, but the code is all-new and the
39 ;;; behavior in some situations differs.
40
41 ;;; Code:
42
43 ;;;###autoload
44 (defun reposition-window (&optional arg)
45 "Make the current definition and/or comment visible.
46 Further invocations move it to the top of the window or toggle the
47 visibility of comments that precede it.
48 Point is left unchanged unless prefix ARG is supplied.
49 If the definition is fully onscreen, it is moved to the top of the
50 window. If it is partly offscreen, the window is scrolled to get the
51 definition (or as much as will fit) onscreen, unless point is in a comment
52 which is also partly offscreen, in which case the scrolling attempts to get
53 as much of the comment onscreen as possible.
54 Initially `reposition-window' attempts to make both the definition and
55 preceding comments visible. Further invocations toggle the visibility of
56 the comment lines.
57 If ARG is non-nil, point may move in order to make the whole defun
58 visible (if only part could otherwise be made so), to make the defun line
59 visible (if point is in code and it could not be made so, or if only
60 comments, including the first comment line, are visible), or to make the
61 first comment line visible (if point is in a comment)."
62 (interactive "P")
63 (let* (;; (here (save-excursion (beginning-of-line) (point)))
64 (here (point))
65 ;; change this name once I've gotten rid of references to ht.
66 ;; this is actually the number of the last screen line
67 (ht (- (window-height (selected-window)) 2))
68 (line (repos-count-screen-lines (window-start) (point)))
69 (comment-height
70 ;; The call to max deals with the case of cursor between defuns.
71 (max 0
72 (repos-count-screen-lines-signed
73 ;; the beginning of the preceding comment
74 (save-excursion
75 (if (not (eobp)) (forward-char 1))
76 (end-of-defun -1)
77 ;; Skip whitespace, newlines, and form feeds.
78 (if (re-search-forward "[^ \t\n\f]" nil t)
79 (backward-char 1))
80 (point))
81 here)))
82 (defun-height
83 (repos-count-screen-lines-signed
84 (save-excursion
85 (end-of-defun 1) ; so comments associate with following defuns
86 (beginning-of-defun 1)
87 (point))
88 here))
89 ;; This must be positive, so don't use the signed version.
90 (defun-depth (repos-count-screen-lines here
91 (save-excursion
92 (end-of-defun 1)
93 (point))))
94 (defun-line-onscreen-p
95 (and (<= defun-height line)
96 (<= (- line defun-height) ht))))
97 (cond ((or (= comment-height line)
98 (and (= line ht)
99 (> comment-height line)
100 ;; if defun line offscreen, we should be in case 4
101 defun-line-onscreen-p))
102 ;; Either first comment line is at top of screen or (point at
103 ;; bottom of screen, defun line onscreen, and first comment line
104 ;; off top of screen). That is, it looks like we just did
105 ;; recenter-definition, trying to fit as much of the comment
106 ;; onscreen as possible. Put defun line at top of screen; that
107 ;; is, show as much code, and as few comments, as possible.
108
109 (if (and arg (> defun-depth (1+ ht)))
110 ;; Can't fit whole defun onscreen without moving point.
111 (progn (end-of-defun) (beginning-of-defun) (recenter 0))
112 (recenter (max defun-height 0)))
113 ;;(repos-debug-macro "1")
114 )
115
116 ((or (= defun-height line)
117 (= line 0)
118 (and (< line comment-height)
119 (< defun-height 0)))
120 ;; Defun line or cursor at top of screen, OR cursor in comment
121 ;; whose first line is offscreen.
122 ;; Avoid moving definition up even if defun runs offscreen;
123 ;; we care more about getting the comment onscreen.
124
125 (cond ((= line ht)
126 ;; cursor on last screen line (and so in a comment)
127 (if arg (progn (end-of-defun) (beginning-of-defun)))
128 (recenter 0)
129 ;;(repos-debug-macro "2a")
130 )
131
132 ;; This condition, copied from case 4, may not be quite right
133
134 ((and arg (< ht comment-height))
135 ;; Can't get first comment line onscreen.
136 ;; Go there and try again.
137 (forward-line (- comment-height))
138 (beginning-of-line)
139 ;; was (reposition-window)
140 (recenter 0)
141 ;;(repos-debug-macro "2b")
142 )
143 (t
144 (recenter (min ht comment-height))
145 ;;(repos-debug-macro "2c")
146 ))
147 ;; (recenter (min ht comment-height))
148 )
149
150 ((and (> (+ line defun-depth -1) ht)
151 defun-line-onscreen-p)
152 ;; Defun runs off the bottom of the screen and the defun line
153 ;; is onscreen.
154 ;; Move the defun up.
155 (recenter (max 0 (1+ (- ht defun-depth)) defun-height))
156 ;;(repos-debug-macro "3")
157 )
158
159 (t
160 ;; If on the bottom line and comment start is offscreen
161 ;; then just move all comments offscreen, or at least as
162 ;; far as they'll go.
163
164 ;; Try to get as much of the comments onscreen as possible.
165 (if (and arg (< ht comment-height))
166 ;; Can't get defun line onscreen; go there and try again.
167 (progn (forward-line (- defun-height))
168 (beginning-of-line)
169 (reposition-window))
170 (recenter (min ht comment-height)))
171 ;;(repos-debug-macro "4")
172 ))))
173
174 ;;; This key should be bound to switch-to-other-buffer by default so
175 ;;; don't ###autoload it. -jwz
176 (define-key esc-map "\C-l" 'reposition-window)
177
178 ;;; Auxiliary functions
179
180 ;; Return number of screen lines between START and END.
181 (defun repos-count-screen-lines (start end)
182 (save-excursion
183 (save-restriction
184 (narrow-to-region start end)
185 (goto-char (point-min))
186 (vertical-motion (- (point-max) (point-min))))))
187
188 ;; Return number of screen lines between START and END; returns a negative
189 ;; number if END precedes START.
190 (defun repos-count-screen-lines-signed (start end)
191 (let ((lines (repos-count-screen-lines start end)))
192 (if (< start end)
193 lines
194 (- lines))))
195
196 ; (defmacro repos-debug-macro (case-no)
197 ; (` (message
198 ; (concat "Case " (, case-no) ": %s %s %s %s %s")
199 ; ht line comment-height defun-height defun-depth)))
200
201 ;;; reposition.el ends here