1;;; compare-w.el --- compare text between windows for Emacs
2
3;; Copyright (C) 1986, 1989, 1993, 1997, 2001, 2002, 2003, 2004,
4;;   2005, 2006, 2007 Free Software Foundation, Inc.
5
6;; Maintainer: FSF
7;; Keywords: convenience files
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
13;; the Free Software Foundation; either version 2, or (at your option)
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 the
23;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
24;; Boston, MA 02110-1301, USA.
25
26;;; Commentary:
27
28;; This package provides one entry point, compare-windows.  It compares
29;; text starting from point in two adjacent windows, advancing point
30;; until it finds a difference.  Option variables permit you to ignore
31;; whitespace differences, or case differences, or both.
32
33;;; Code:
34
35(defgroup compare-windows nil
36  "Compare text between windows."
37  :prefix "compare-"
38  :group 'tools)
39
40(defcustom compare-windows-whitespace "\\(\\s-\\|\n\\)+"
41  "*Regexp or function that defines whitespace sequences for `compare-windows'.
42That command optionally ignores changes in whitespace.
43
44The value of `compare-windows-whitespace' is normally a regexp, but it
45can also be a function.  The function's job is to categorize any
46whitespace around (including before) point; it should also advance
47past any whitespace.  The function is called in each window, with
48point at the current scanning point.  It gets one argument, the point
49where \\[compare-windows] was originally called; it should not look at
50any text before that point.
51
52If the function returns the same value for both windows, then the
53whitespace is considered to match, and is skipped."
54  :type '(choice regexp function)
55  :group 'compare-windows)
56
57(defcustom compare-ignore-whitespace nil
58  "*Non-nil means `compare-windows' ignores whitespace."
59  :type 'boolean
60  :group 'compare-windows
61  :version "22.1")
62
63(defcustom compare-ignore-case nil
64  "*Non-nil means `compare-windows' ignores case differences."
65  :type 'boolean
66  :group 'compare-windows)
67
68(defcustom compare-windows-sync 'compare-windows-sync-default-function
69  "*Function or regexp that is used to synchronize points in two
70windows if before calling `compare-windows' points are located
71on mismatched positions.
72
73The value of `compare-windows-sync' can be a function.  The
74function's job is to advance points in both windows to the next
75matching text.  If the value of `compare-windows-sync' is a
76regexp, then points in both windows are advanced to the next
77occurrence of this regexp.
78
79The current default value is the general function
80`compare-windows-sync-default-function' that is able to
81synchronize points by using quadratic algorithm to find the first
82matching 32-character string in two windows.
83
84The other useful values of this variable could be such functions
85as `forward-word', `forward-sentence', `forward-paragraph', or a
86regexp containing some field separator or a newline, depending on
87the nature of the difference units separator.  The variable can
88be made buffer-local.
89
90If the value of this variable is `nil' (option \"No sync\"), then
91no synchronization is performed, and the function `ding' is called
92to beep or flash the screen when points are mismatched."
93  :type '(choice function regexp (const :tag "No sync" nil))
94  :group 'compare-windows
95  :version "22.1")
96
97(defcustom compare-windows-sync-string-size 32
98  "*Size of string from one window that is searched in second window.
99
100Small number makes difference regions more fine-grained, but it
101may fail by finding the wrong match.  The bigger number makes
102difference regions more coarse-grained.
103
104The default value 32 is good for the most cases."
105  :type 'integer
106  :group 'compare-windows
107  :version "22.1")
108
109(defcustom compare-windows-recenter nil
110  "*List of two values, each of which is used as argument of
111function `recenter' called in each of two windows to place
112matching points side-by-side.
113
114The value `(-1 0)' is useful if windows are split vertically,
115and the value `((4) (4))' for horizontally split windows."
116  :type '(list sexp sexp)
117  :group 'compare-windows
118  :version "22.1")
119
120(defcustom compare-windows-highlight t
121  "*Non-nil means compare-windows highlights the differences.
122The value t removes highlighting immediately after invoking a command
123other than `compare-windows'.
124The value `persistent' leaves all highlighted differences.  You can clear
125out all highlighting later with the command `compare-windows-dehighlight'."
126  :type '(choice (const :tag "No highlighting" nil)
127		 (const :tag "Persistent highlighting" persistent)
128		 (other :tag "Highlight until next command" t))
129  :group 'compare-windows
130  :version "22.1")
131
132(defface compare-windows
133  '((t :inherit lazy-highlight))
134  "Face for highlighting of compare-windows difference regions."
135  :group 'compare-windows
136  :version "22.1")
137
138(defvar compare-windows-overlay1 nil)
139(defvar compare-windows-overlay2 nil)
140(defvar compare-windows-overlays1 nil)
141(defvar compare-windows-overlays2 nil)
142(defvar compare-windows-sync-point nil)
143
144;;;###autoload
145(defun compare-windows (ignore-whitespace)
146  "Compare text in current window with text in next window.
147Compares the text starting at point in each window,
148moving over text in each one as far as they match.
149
150This command pushes the mark in each window
151at the prior location of point in that window.
152If both windows display the same buffer,
153the mark is pushed twice in that buffer:
154first in the other window, then in the selected window.
155
156A prefix arg means reverse the value of variable
157`compare-ignore-whitespace'.  If `compare-ignore-whitespace' is
158nil, then a prefix arg means ignore changes in whitespace.  If
159`compare-ignore-whitespace' is non-nil, then a prefix arg means
160don't ignore changes in whitespace.  The variable
161`compare-windows-whitespace' controls how whitespace is skipped.
162If `compare-ignore-case' is non-nil, changes in case are also
163ignored.
164
165If `compare-windows-sync' is non-nil, then successive calls of
166this command work in interlaced mode:
167on first call it advances points to the next difference,
168on second call it synchronizes points by skipping the difference,
169on third call it again advances points to the next difference and so on."
170  (interactive "P")
171  (if compare-ignore-whitespace
172      (setq ignore-whitespace (not ignore-whitespace)))
173  (let* (p1 p2 maxp1 maxp2 b1 b2 w2
174	    (progress 1)
175	    (opoint1 (point))
176	    opoint2
177	    skip-func-1
178	    skip-func-2
179	    (sync-func (if (stringp compare-windows-sync)
180                           'compare-windows-sync-regexp
181                         compare-windows-sync)))
182    (setq p1 (point) b1 (current-buffer))
183    (setq w2 (next-window (selected-window)))
184    (if (eq w2 (selected-window))
185	(setq w2 (next-window (selected-window) nil 'visible)))
186    (if (eq w2 (selected-window))
187	(error "No other window"))
188    (setq p2 (window-point w2)
189	  b2 (window-buffer w2))
190    (setq opoint2 p2)
191    (setq maxp1 (point-max))
192
193    (setq skip-func-1 (if ignore-whitespace
194			  (if (stringp compare-windows-whitespace)
195			      (lambda (pos)
196				(compare-windows-skip-whitespace pos)
197				t)
198			    compare-windows-whitespace)))
199
200    (with-current-buffer b2
201      (setq skip-func-2 (if ignore-whitespace
202			    (if (stringp compare-windows-whitespace)
203			      (lambda (pos)
204				(compare-windows-skip-whitespace pos)
205				t)
206			      compare-windows-whitespace)))
207      (push-mark p2 t)
208      (setq maxp2 (point-max)))
209    (push-mark)
210
211    (while (> progress 0)
212      ;; If both windows have whitespace next to point,
213      ;; optionally skip over it.
214      (and skip-func-1
215	   (save-excursion
216	     (let (p1a p2a w1 w2 result1 result2)
217	       (setq result1 (funcall skip-func-1 opoint1))
218	       (setq p1a (point))
219	       (set-buffer b2)
220	       (goto-char p2)
221	       (setq result2 (funcall skip-func-2 opoint2))
222	       (setq p2a (point))
223	       (if (and result1 result2 (eq result1 result2))
224		   (setq p1 p1a
225			 p2 p2a)))))
226
227      (let ((size (min (- maxp1 p1) (- maxp2 p2)))
228	    (case-fold-search compare-ignore-case))
229	(setq progress (compare-buffer-substrings b2 p2 (+ size p2)
230						  b1 p1 (+ size p1)))
231	(setq progress (if (zerop progress) size (1- (abs progress))))
232	(setq p1 (+ p1 progress) p2 (+ p2 progress)))
233      ;; Advance point now rather than later, in case we're interrupted.
234      (goto-char p1)
235      (set-window-point w2 p2)
236      (when compare-windows-recenter
237        (recenter (car compare-windows-recenter))
238        (with-selected-window w2 (recenter (cadr compare-windows-recenter)))))
239
240    (if (= (point) opoint1)
241	(if (not sync-func)
242            (ding)
243          ;; If points are not advanced (i.e. already on mismatch position),
244          ;; then synchronize points between both windows
245          (save-excursion
246            (setq compare-windows-sync-point nil)
247            (funcall sync-func)
248            (setq p1 (point))
249            (set-buffer b2)
250            (goto-char p2)
251            (funcall sync-func)
252            (setq p2 (point)))
253          (goto-char p1)
254          (set-window-point w2 p2)
255          (when compare-windows-recenter
256            (recenter (car compare-windows-recenter))
257            (with-selected-window w2 (recenter (cadr compare-windows-recenter))))
258          ;; If points are still not synchronized, then ding
259          (when (and (= p1 opoint1) (= p2 opoint2))
260            ;; Display error message when current points in two windows
261            ;; are unmatched and next matching points can't be found.
262            (compare-windows-dehighlight)
263            (ding)
264            (message "No more matching points"))))))
265
266;; Move forward over whatever might be called whitespace.
267;; compare-windows-whitespace is a regexp that matches whitespace.
268;; Match it at various starting points before the original point
269;; and find the latest point at which a match ends.
270;; Don't try starting points before START, though.
271;; Value is non-nil if whitespace is found.
272;; If there is whitespace before point, but none after,
273;; then return t, but don't advance point.
274(defun compare-windows-skip-whitespace (start)
275  (let ((end (point))
276	(beg (point))
277	(opoint (point)))
278    (while (or (and (looking-at compare-windows-whitespace)
279		    (<= end (match-end 0))
280		    ;; This match goes past END, so advance END.
281		    (progn (setq end (match-end 0))
282			   (> (point) start)))
283	       (and (/= (point) start)
284		    ;; Consider at least the char before point,
285		    ;; unless it is also before START.
286		    (= (point) opoint)))
287      ;; keep going back until whitespace
288      ;; doesn't extend to or past end
289      (forward-char -1))
290    (setq beg (point))
291    (goto-char end)
292    (or (/= beg opoint)
293	(/= end opoint))))
294
295;; Move forward to the next synchronization regexp.
296(defun compare-windows-sync-regexp ()
297  (if (stringp compare-windows-sync)
298      (re-search-forward compare-windows-sync nil t)))
299
300;; Function works in two passes: one call on each window.
301;; On the first call both matching points are computed,
302;; and one of them is stored in compare-windows-sync-point
303;; to be used when this function is called on second window.
304(defun compare-windows-sync-default-function ()
305  (if (not compare-windows-sync-point)
306      (let* ((w1 (selected-window))
307             (w2 (next-window w1))
308             (b2 (window-buffer w2))
309             (point-max2 (with-current-buffer b2 (point-max)))
310             (op2 (window-point w2))
311             (op1 (point))
312             (region-size compare-windows-sync-string-size)
313             (string-size compare-windows-sync-string-size)
314             in-bounds-p s1 p2 p12s p12)
315        (while (and
316                ;; until matching points are found
317                (not p12s)
318                ;; until size exceeds the maximum points of both buffers
319                ;; (bounds below take care to not overdo in each of them)
320                (or (setq in-bounds-p (< region-size (max (- (point-max) op1)
321                                                          (- point-max2 op2))))
322                    ;; until string size becomes smaller than 4
323                    (> string-size 4)))
324          (if in-bounds-p
325              ;; make the next search in the double-sized region;
326              ;; on first iteration it is 2*compare-windows-sync-string-size,
327              ;; on last iterations it exceeds both buffers maximum points
328              (setq region-size (* region-size 2))
329            ;; if region size exceeds the maximum points of both buffers,
330            ;; then start to halve the string size until 4;
331            ;; this helps to find differences near the end of buffers
332            (setq string-size (/ string-size 2)))
333          (let ((p1 op1)
334                (bound1 (- (min (+ op1 region-size) (point-max)) string-size))
335                (bound2 (min (+ op2 region-size) point-max2)))
336            (while (< p1 bound1)
337              (setq s1 (buffer-substring-no-properties p1 (+ p1 string-size)))
338              (setq p2 (with-current-buffer b2
339                         (goto-char op2)
340                         (let ((case-fold-search compare-ignore-case))
341                           (search-forward s1 bound2 t))))
342              (when p2
343                (setq p2 (- p2 string-size))
344                (setq p12s (cons (list (+ p1 p2) p1 p2) p12s)))
345              (setq p1 (1+ p1)))))
346        (when p12s
347          ;; use closest matching points (i.e. points with minimal sum)
348          (setq p12 (cdr (assq (apply 'min (mapcar 'car p12s)) p12s)))
349          (goto-char (car p12))
350          (compare-windows-highlight op1 (car p12) (current-buffer) w1
351                                     op2 (cadr p12) b2 w2))
352        (setq compare-windows-sync-point (or (cadr p12) t)))
353    ;; else set point in the second window to the pre-calculated value
354    (if (numberp compare-windows-sync-point)
355        (goto-char compare-windows-sync-point))
356    (setq compare-windows-sync-point nil)))
357
358;; Highlight differences
359(defun compare-windows-highlight (beg1 end1 b1 w1 beg2 end2 b2 w2)
360  (when compare-windows-highlight
361    (if compare-windows-overlay1
362        (move-overlay compare-windows-overlay1 beg1 end1 b1)
363      (setq compare-windows-overlay1 (make-overlay beg1 end1 b1))
364      (overlay-put compare-windows-overlay1 'face 'compare-windows)
365      (overlay-put compare-windows-overlay1 'priority 1000))
366    (overlay-put compare-windows-overlay1 'window w1)
367    (if compare-windows-overlay2
368        (move-overlay compare-windows-overlay2 beg2 end2 b2)
369      (setq compare-windows-overlay2 (make-overlay beg2 end2 b2))
370      (overlay-put compare-windows-overlay2 'face 'compare-windows)
371      (overlay-put compare-windows-overlay2 'priority 1000))
372    (overlay-put compare-windows-overlay2 'window w2)
373    (if (not (eq compare-windows-highlight 'persistent))
374	;; Remove highlighting before next command is executed
375	(add-hook 'pre-command-hook 'compare-windows-dehighlight)
376      (when compare-windows-overlay1
377	(push (copy-overlay compare-windows-overlay1) compare-windows-overlays1)
378	(delete-overlay compare-windows-overlay1))
379      (when compare-windows-overlay2
380	(push (copy-overlay compare-windows-overlay2) compare-windows-overlays2)
381	(delete-overlay compare-windows-overlay2)))))
382
383(defun compare-windows-dehighlight ()
384  "Remove highlighting created by `compare-windows-highlight'."
385  (interactive)
386  (remove-hook 'pre-command-hook 'compare-windows-dehighlight)
387  (mapc 'delete-overlay compare-windows-overlays1)
388  (mapc 'delete-overlay compare-windows-overlays2)
389  (and compare-windows-overlay1 (delete-overlay compare-windows-overlay1))
390  (and compare-windows-overlay2 (delete-overlay compare-windows-overlay2)))
391
392(provide 'compare-w)
393
394;;; arch-tag: 4177aab1-48e6-4a98-b7a1-000ee285de46
395;;; compare-w.el ends here
396