1;;; reposition.el --- center a Lisp function or comment on the screen 2 3;; Copyright (C) 1991, 1994, 2001, 2002, 2003, 2004, 4;; 2005, 2006, 2007 Free Software Foundation, Inc. 5 6;; Author: Michael D. Ernst <mernst@theory.lcs.mit.edu> 7;; Created: Jan 1991 8;; Maintainer: FSF 9 10;; This file is part of GNU Emacs. 11 12;; GNU Emacs is free software; you can redistribute it and/or modify 13;; it under the terms of the GNU General Public License as published by 14;; the Free Software Foundation; either version 2, or (at your option) 15;; any later version. 16 17;; GNU Emacs is distributed in the hope that it will be useful, 18;; but WITHOUT ANY WARRANTY; without even the implied warranty of 19;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 20;; GNU General Public License for more details. 21 22;; You should have received a copy of the GNU General Public License 23;; along with GNU Emacs; see the file COPYING. If not, write to the 24;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, 25;; Boston, MA 02110-1301, USA. 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. 46Further invocations move it to the top of the window or toggle the 47visibility 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 50window. If it is partly offscreen, the window is scrolled to get the 51definition (or as much as will fit) onscreen, unless point is in a comment 52which is also partly offscreen, in which case the scrolling attempts to get 53as much of the comment onscreen as possible. 54 Initially `reposition-window' attempts to make both the definition and 55preceding comments visible. Further invocations toggle the visibility of 56the comment lines. 57 If ARG is non-nil, point may move in order to make the whole defun 58visible (if only part could otherwise be made so), to make the defun line 59visible (if point is in code and it could not be made so, or if only 60comments, including the first comment line, are visible), or to make the 61first 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;;;###autoload (define-key esc-map "\C-l" 'reposition-window) 175 176;;; Auxiliary functions 177 178;; Return number of screen lines between START and END. 179(defun repos-count-screen-lines (start end) 180 (save-excursion 181 (save-restriction 182 (narrow-to-region start end) 183 (goto-char (point-min)) 184 (vertical-motion (- (point-max) (point-min)))))) 185 186;; Return number of screen lines between START and END; returns a negative 187;; number if END precedes START. 188(defun repos-count-screen-lines-signed (start end) 189 (let ((lines (repos-count-screen-lines start end))) 190 (if (< start end) 191 lines 192 (- lines)))) 193 194;; (defmacro repos-debug-macro (case-no) 195;; `(message (concat "Case " ,case-no ": %s %s %s %s %s") 196;; ht line comment-height defun-height defun-depth)) 197 198(provide 'reposition) 199 200;;; arch-tag: 79487039-3bd7-4ab5-a3e8-ecf3b4919010 201;;; reposition.el ends here 202