1 ;;; reposition.el --- center a Lisp function or comment on the screen
3 ;; Copyright (C) 1991, 1994 Free Software Foundation, Inc.
5 ;; Author: Michael D. Ernst <mernst@theory.lcs.mit.edu>
9 ;; This file is part of XEmacs.
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)
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.
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, Inc., 59 Temple Place - Suite 330, Boston, MA
26 ;;; Synched up with: FSF 19.34.
30 ;; Reposition-window makes an entire function definition or comment visible,
31 ;; or, if it is already visible, places it at the top of the window;
32 ;; additional invocations toggle the visibility of comments preceding the
33 ;; code. For the gory details, see the documentation for reposition-window;
34 ;; rather than reading that, you may just want to play with it.
36 ;; This tries pretty hard to do the recentering correctly; the precise
37 ;; action depends on what the buffer looks like. If you find a situation
38 ;; where it doesn't behave well, let me know. This function is modeled
39 ;; after one of the same name in ZMACS, but the code is all-new and the
40 ;; behavior in some situations differs.
45 (defun reposition-window (&optional arg)
46 "Make the current definition and/or comment visible.
47 Further invocations move it to the top of the window or toggle the
48 visibility of comments that precede it.
49 Point is left unchanged unless prefix ARG is supplied.
50 If the definition is fully onscreen, it is moved to the top of the
51 window. If it is partly offscreen, the window is scrolled to get the
52 definition (or as much as will fit) onscreen, unless point is in a comment
53 which is also partly offscreen, in which case the scrolling attempts to get
54 as much of the comment onscreen as possible.
55 Initially `reposition-window' attempts to make both the definition and
56 preceding comments visible. Further invocations toggle the visibility of
58 If ARG is non-nil, point may move in order to make the whole defun
59 visible (if only part could otherwise be made so), to make the defun line
60 visible (if point is in code and it could not be made so, or if only
61 comments, including the first comment line, are visible), or to make the
62 first comment line visible (if point is in a comment)."
64 (let* (;; (here (save-excursion (beginning-of-line) (point)))
66 ;; change this name once I've gotten rid of references to ht.
67 ;; this is actually the number of the last screen line
68 (ht (- (window-height (selected-window)) 2))
69 (line (repos-count-screen-lines (window-start) (point)))
71 ;; The call to max deals with the case of cursor between defuns.
73 (repos-count-screen-lines-signed
74 ;; the beginning of the preceding comment
76 (if (not (eobp)) (forward-char 1))
78 ;; Skip whitespace, newlines, and form feeds.
79 (if (re-search-forward "[^ \t\n\f]" nil t)
84 (repos-count-screen-lines-signed
86 (end-of-defun 1) ; so comments associate with following defuns
87 (beginning-of-defun 1)
90 ;; This must be positive, so don't use the signed version.
91 (defun-depth (repos-count-screen-lines here
95 (defun-line-onscreen-p
96 (and (<= defun-height line)
97 (<= (- line defun-height) ht))))
98 (cond ((or (= comment-height line)
100 (> comment-height line)
101 ;; if defun line offscreen, we should be in case 4
102 defun-line-onscreen-p))
103 ;; Either first comment line is at top of screen or (point at
104 ;; bottom of screen, defun line onscreen, and first comment line
105 ;; off top of screen). That is, it looks like we just did
106 ;; recenter-definition, trying to fit as much of the comment
107 ;; onscreen as possible. Put defun line at top of screen; that
108 ;; is, show as much code, and as few comments, as possible.
110 (if (and arg (> defun-depth (1+ ht)))
111 ;; Can't fit whole defun onscreen without moving point.
112 (progn (end-of-defun) (beginning-of-defun) (recenter 0))
113 (recenter (max defun-height 0)))
114 ;;(repos-debug-macro "1")
117 ((or (= defun-height line)
119 (and (< line comment-height)
121 ;; Defun line or cursor at top of screen, OR cursor in comment
122 ;; whose first line is offscreen.
123 ;; Avoid moving definition up even if defun runs offscreen;
124 ;; we care more about getting the comment onscreen.
127 ;; cursor on last screen line (and so in a comment)
128 (if arg (progn (end-of-defun) (beginning-of-defun)))
130 ;;(repos-debug-macro "2a")
133 ;; This condition, copied from case 4, may not be quite right
135 ((and arg (< ht comment-height))
136 ;; Can't get first comment line onscreen.
137 ;; Go there and try again.
138 (forward-line (- comment-height))
140 ;; was (reposition-window)
142 ;;(repos-debug-macro "2b")
145 (recenter (min ht comment-height))
146 ;;(repos-debug-macro "2c")
148 ;; (recenter (min ht comment-height))
151 ((and (> (+ line defun-depth -1) ht)
152 defun-line-onscreen-p)
153 ;; Defun runs off the bottom of the screen and the defun line
155 ;; Move the defun up.
156 (recenter (max 0 (1+ (- ht defun-depth)) defun-height))
157 ;;(repos-debug-macro "3")
161 ;; If on the bottom line and comment start is offscreen
162 ;; then just move all comments offscreen, or at least as
163 ;; far as they'll go.
165 ;; Try to get as much of the comments onscreen as possible.
166 (if (and arg (< ht comment-height))
167 ;; Can't get defun line onscreen; go there and try again.
168 (progn (forward-line (- defun-height))
171 (recenter (min ht comment-height)))
172 ;;(repos-debug-macro "4")
175 ;;; This key should be bound to switch-to-other-buffer by default so
176 ;;; don't ###autoload it. -jwz
177 (define-key esc-map "\C-l" 'reposition-window)
179 ;;; Auxiliary functions
181 ;; Return number of screen lines between START and END.
182 (defun repos-count-screen-lines (start end)
185 (narrow-to-region start end)
186 (goto-char (point-min))
187 (vertical-motion (- (point-max) (point-min))))))
189 ;; Return number of screen lines between START and END; returns a negative
190 ;; number if END precedes START.
191 (defun repos-count-screen-lines-signed (start end)
192 (let ((lines (repos-count-screen-lines start end)))
197 ; (defmacro repos-debug-macro (case-no)
199 ; (concat "Case " (, case-no) ": %s %s %s %s %s")
200 ; ht line comment-height defun-height defun-depth)))
202 ;;; reposition.el ends here