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c88ab9ce ER |
1 | ;;; reposition.el --- center a Lisp function or comment on the screen |
2 | ||
3a801d0c ER |
3 | ;; Copyright (C) 1991 Free Software Foundation, Inc. |
4 | ||
e5167999 | 5 | ;; Author: Michael D. Ernst <mernst@theory.lcs.mit.edu> |
d9ecc911 | 6 | ;; Created: Jan 1991 |
e5167999 | 7 | ;; Maintainer: FSF |
57d378a9 RS |
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 | |
e5167999 | 13 | ;; the Free Software Foundation; either version 2, or (at your option) |
57d378a9 RS |
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 | |
23 | ;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. | |
24 | ||
e5167999 ER |
25 | ;;; Commentary: |
26 | ||
57d378a9 RS |
27 | ;;; Reposition-window makes an entire function definition or comment visible, |
28 | ;;; or, if it is already visible, places it at the top of the window; | |
29 | ;;; additional invocations toggle the visibility of comments preceding the | |
30 | ;;; code. For the gory details, see the documentation for reposition-window; | |
31 | ;;; rather than reading that, you may just want to play with it. | |
32 | ||
57d378a9 RS |
33 | ;;; This tries pretty hard to do the recentering correctly; the precise |
34 | ;;; action depends on what the buffer looks like. If you find a situation | |
35 | ;;; where it doesn't behave well, let me know. This function is modeled | |
36 | ;;; after one of the same name in ZMACS, but the code is all-new and the | |
37 | ;;; behavior in some situations differs. | |
38 | ||
e5167999 ER |
39 | ;;; Code: |
40 | ||
657e634f | 41 | ;;;###autoload |
57d378a9 RS |
42 | (defun reposition-window (&optional arg) |
43 | "Make the current definition and/or comment visible. | |
44 | Further invocations move it to the top of the window or toggle the | |
45 | visibility of comments that precede it. | |
46 | Point is left unchanged unless prefix ARG is supplied. | |
47 | If the definition is fully onscreen, it is moved to the top of the | |
48 | window. If it is partly offscreen, the window is scrolled to get the | |
49 | definition (or as much as will fit) onscreen, unless point is in a comment | |
50 | which is also partly offscreen, in which case the scrolling attempts to get | |
51 | as much of the comment onscreen as possible. | |
52 | Initially `reposition-window' attempts to make both the definition and | |
53 | preceding comments visible. Further invocations toggle the visibility of | |
54 | the comment lines. | |
55 | If ARG is non-nil, point may move in order to make the whole defun | |
56 | visible (if only part could otherwise be made so), to make the defun line | |
57 | visible (if point is in code and it could not be made so, or if only | |
58 | comments, including the first comment line, are visible), or to make the | |
59 | first comment line visible (if point is in a comment)." | |
60 | (interactive "P") | |
61 | (let* (;; (here (save-excursion (beginning-of-line) (point))) | |
62 | (here (point)) | |
63 | ;; change this name once I've gotten rid of references to ht. | |
64 | ;; this is actually the number of the last screen line | |
65 | (ht (- (window-height (selected-window)) 2)) | |
66 | (line (repos-count-screen-lines (window-start) (point))) | |
67 | (comment-height | |
68 | ;; The call to max deals with the case of cursor between defuns. | |
69 | (max 0 | |
70 | (repos-count-screen-lines-signed | |
71 | ;; the beginning of the preceding comment | |
72 | (save-excursion | |
73 | (forward-char 1) (end-of-defun -1) | |
74 | ;; Skip whitespace, newlines, and form feeds. | |
75 | (re-search-forward "[^\\s \n\014]") | |
76 | (backward-char 1) | |
77 | (point)) | |
78 | here))) | |
79 | (defun-height | |
80 | (repos-count-screen-lines-signed | |
81 | (save-excursion | |
82 | (end-of-defun 1) ; so comments associate with following defuns | |
83 | (beginning-of-defun 1) | |
84 | (point)) | |
85 | here)) | |
86 | ;; This must be positive, so don't use the signed version. | |
87 | (defun-depth (repos-count-screen-lines here | |
88 | (save-excursion | |
89 | (end-of-defun 1) | |
90 | (point)))) | |
91 | (defun-line-onscreen-p | |
92 | (and (<= defun-height line) | |
93 | (<= (- line defun-height) ht)))) | |
94 | (cond ((or (= comment-height line) | |
95 | (and (= line ht) | |
96 | (> comment-height line) | |
97 | ;; if defun line offscreen, we should be in case 4 | |
98 | defun-line-onscreen-p)) | |
99 | ;; Either first comment line is at top of screen or (point at | |
100 | ;; bottom of screen, defun line onscreen, and first comment line | |
101 | ;; off top of screen). That is, it looks like we just did | |
102 | ;; recenter-definition, trying to fit as much of the comment | |
103 | ;; onscreen as possible. Put defun line at top of screen; that | |
104 | ;; is, show as much code, and as few comments, as possible. | |
105 | ||
106 | (if (and arg (> defun-depth (1+ ht))) | |
107 | ;; Can't fit whole defun onscreen without moving point. | |
108 | (progn (end-of-defun) (beginning-of-defun) (recenter 0)) | |
109 | (recenter (max defun-height 0))) | |
110 | ;;(repos-debug-macro "1") | |
111 | ) | |
112 | ||
113 | ((or (= defun-height line) | |
114 | (= line 0) | |
115 | (and (< line comment-height) | |
116 | (< defun-height 0))) | |
117 | ;; Defun line or cursor at top of screen, OR cursor in comment | |
118 | ;; whose first line is offscreen. | |
119 | ;; Avoid moving definition up even if defun runs offscreen; | |
120 | ;; we care more about getting the comment onscreen. | |
121 | ||
122 | (cond ((= line ht) | |
123 | ;; cursor on last screen line (and so in a comment) | |
124 | (if arg (progn (end-of-defun) (beginning-of-defun))) | |
125 | (recenter 0) | |
126 | ;;(repos-debug-macro "2a") | |
127 | ) | |
128 | ||
129 | ;; This condition, copied from case 4, may not be quite right | |
130 | ||
131 | ((and arg (< ht comment-height)) | |
132 | ;; Can't get first comment line onscreen. | |
133 | ;; Go there and try again. | |
134 | (forward-line (- comment-height)) | |
135 | (beginning-of-line) | |
136 | ;; was (reposition-window) | |
137 | (recenter 0) | |
138 | ;;(repos-debug-macro "2b") | |
139 | ) | |
140 | (t | |
141 | (recenter (min ht comment-height)) | |
142 | ;;(repos-debug-macro "2c") | |
143 | )) | |
144 | ;; (recenter (min ht comment-height)) | |
145 | ) | |
146 | ||
147 | ((and (> (+ line defun-depth -1) ht) | |
148 | defun-line-onscreen-p) | |
149 | ;; Defun runs off the bottom of the screen and the defun line | |
150 | ;; is onscreen. | |
151 | ;; Move the defun up. | |
152 | (recenter (max 0 (1+ (- ht defun-depth)) defun-height)) | |
153 | ;;(repos-debug-macro "3") | |
154 | ) | |
155 | ||
156 | (t | |
157 | ;; If on the bottom line and comment start is offscreen | |
158 | ;; then just move all comments offscreen, or at least as | |
159 | ;; far as they'll go. | |
160 | ||
161 | ;; Try to get as much of the comments onscreen as possible. | |
162 | (if (and arg (< ht comment-height)) | |
163 | ;; Can't get defun line onscreen; go there and try again. | |
164 | (progn (forward-line (- defun-height)) | |
165 | (beginning-of-line) | |
166 | (reposition-window)) | |
167 | (recenter (min ht comment-height))) | |
168 | ;;(repos-debug-macro "4") | |
169 | )))) | |
170 | ||
6503cec3 | 171 | ;;;###autoload |
e5aaf346 | 172 | (define-key esc-map "\C-l" 'reposition-window) |
77176e73 | 173 | |
57d378a9 RS |
174 | ;;; Auxiliary functions |
175 | ||
176 | ;; Return number of screen lines between START and END. | |
177 | (defun repos-count-screen-lines (start end) | |
178 | (save-excursion | |
179 | (save-restriction | |
180 | (narrow-to-region start end) | |
181 | (goto-char (point-min)) | |
182 | (vertical-motion (- (point-max) (point-min)))))) | |
183 | ||
184 | ;; Return number of screen lines between START and END; returns a negative | |
185 | ;; number if END precedes START. | |
186 | (defun repos-count-screen-lines-signed (start end) | |
187 | (let ((lines (repos-count-screen-lines start end))) | |
188 | (if (< start end) | |
189 | lines | |
190 | (- lines)))) | |
191 | ||
192 | ; (defmacro repos-debug-macro (case-no) | |
193 | ; (` (message | |
194 | ; (concat "Case " (, case-no) ": %s %s %s %s %s") | |
195 | ; ht line comment-height defun-height defun-depth))) | |
196 | ||
c88ab9ce | 197 | ;;; reposition.el ends here |