path: root/lisp/ediff.el

;;; ediff.el --- a visual interface to diff & patch
;;; Copyright (C) 1994 Free Software Foundation, Inc.

;; Author: Michael Kifer <[email protected]>
;; Created: February 2, 1994
;; Version: 1.65e
;; Keywords: comparing, merging, patching, version control.

(defvar ediff-version "1.65e" "The current version of Ediff")
(defvar ediff-date "September 1, 1994" "Date of last update")  

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to
;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.


;;; Commentary:
;;  ----------

;; Never read those diff outputs again!
;; Apply patch selectively, like a pro!

;; This package provides a convenient way of simultaneous browsing through
;; the differences between a pair of files or buffers.  The two files being
;; compared (file-A and file-B) are shown in separate windows (side by
;; side, one above the another, or in separate frames), and the differences
;; are highlighted as you step through them.  You can also copy difference
;; regions from one buffer to another (and recover old differences if you
;; change your mind).

;; In addition, Ediff can apply a patch to a file and then let you step
;; though both files, the patched and the original one, simultaneously,
;; difference-by-difference.  You can even apply a patch right out of a
;; mail buffer, i.e., patches received by mail don't even have to be saved.
;; Since Ediff lets you copy differences between buffers, you can, in
;; effect, apply patches selectively (i.e., you can copy a difference
;; region from file.orig to file, thereby undoing any particular patch that
;; you don't like).

;; This package builds upon the ideas borrowed from emerge.el.  It is still
;; using half a dozen of functions defined there. Several other Ediff's
;; functions are adaptations from emerge.el. Ediff requires, at least, 
;; Version 5 of emerge.el. This version comes with standard distributions
;; of Emacs and Lemacs.  Make sure you don't have some stray old copy of
;; Emerge on your load path.

;; Ediff is complimentary to Emerge.  While Emerge is primarily intended
;; for merging of files, Ediff is by far superior for browsing through
;; files compared via diff and for patching files with patch.
;; Furthermore, Ediff is more convenient even for merging, when one of the
;; files is a designated output.  This situation arises while patching
;; files or when comparing an old version of a file with a newer version
;; (in such cases, it is often desirable to selectively revert some
;; portions of the new file to its old state).

;; Ediff also supports version control via vc.el (in the standard
;; distribution of Emacs 19) and rcs.el. The latter is a package written by 
;; Sebastian Kremer <[email protected]>, which is available in
;;
;;         ftp.cs.buffalo.edu:pub/Emacs/rcs.tar.Z
;;         ftp.uni-koeln.de:/pub/gnu/emacs/rcs.tar.Z
;;
;; To specify which version control package you are using, set the variable
;; ediff-version-control-package, e.g.,
;;	(setq ediff-version-control-package 'rcs)
;; The default, is 'vc'.


;; Window configuration:
;; ----------------------

;; By default, Ediff sets things up in one frame, splitting it between a
;; small control window and the two windows for file-A and file-B.  The
;; split between these latter windows can be horizontal or vertical, which
;; can be changed interactively by hitting 's' while the cursor is in the
;; control window.
;;
;; In a multi-frame situation, Ediff would work as follows.  When it starts,
;; it will place the control window in the frame that was selected at the
;; time of the invocation.  If file-A or file-B is seen in one of the
;; frames, Ediff will leave it there.  If a file (A/B) is not visible in any
;; frame, Ediff will arrange that it will share a frame with the control
;; window. (If none of the files is visible, then both will share the
;; control window frame.) The same algorithm works when you hit 'c'
;; (ediff-recenter), 'p' (ediff-previous-difference), 'n', etc.
;;
;; Thus, you can compare files in one frame or in different frames.
;; The former is done by default, while the latter can be achieved by
;; arranging files A and B to be seen in different frames.  Ediff
;; respects these arrangements, automatically adapting itself to 
;; the multi-frame mode.


;; To those who like to go where noone has gone before:

;;  Ediff lets the user run multiple sessions at once, i.e., you can invoke
;;  Ediff on different functions several times in a row, without exiting
;;  the previous Ediff sessions. Different sessions may even operate on the
;;  same pair of files.  So, in principle, it is possible to do, say,
;;  pairwise comparison of three (or more) different files.  Each session
;;  would have its own Ediff Control Panel and all the regarding a
;;  particular session is local to the associated control panel buffer.
;;  You can switch between sessions by suspending one session and then
;;  switching to another control panel. (Different control panel buffers
;;  are distinguished by a numerical suffix, e.g., Ediff Control Panel<3>.)
;;  Thus, if you would like to compare three files pairwise, you can do
;;  this by preparing three different frames, each with its own control
;;  window.  (This would require a very wide screen, and I never claimed
;;  that such 3-way comparison is very easy to do.)
;;
;; If you need to conduct multiple Ediff sessions on the same file, one
;; thing should be kept in mind: each time you invoke Ediff on a buffer that
;; already participates in another Ediff session, that buffer should not
;; have any ASCII Ediff flags in it. (Highlighting with faces is OK.)  If
;; flags are not removed, difference overlays won't be set correctly
;; for the second invocation of Ediff.  The simplest way to remove ASCII
;; flags from an Ediff buffer is to hit `h' and thus switch to highlighting
;; with faces (unhighlighting on a dumb terminal).

;;;  Remote and Compressed Files
;;   ---------------------------

;;  Ediff will work with remote, compressed, and encrypted files. Ediff
;;  supports ange-ftp.el, jka-compr.el, uncompress.el and crypt++.el, but
;;  it may work with other similar packages as well. This
;;  means that you can compare files residing on another machine, or you
;;  can apply a patch to a file on another machine (even the patch itself
;;  can be a remote file!).
;;
;;  When patching compressed or remote files, Ediff doesn't rename the
;;  source file into source-file-name.orig (unlike what `patch' would
;;  usually do). Instead, the source file retains its name and the result
;;  of applying the patch is placed in a temporary file that has the suffix
;;  `.patched'.  Generally, this applies to files that are handled using
;;  black magic, such as special file handlers (ange-ftp and some
;;  compression and encryption packages all use this method).
;;
;;  Regular files are treated by `patch' in the usual manner, i.e., the
;;  original is renamed into source-name.orig and the result of the patch
;;  is placed into the file source-name.


;;; Remarks: 
;;  -------

;;  1. Ediff is heavily dependent on the new features of Emacs 19.
;;     It won't run under Emacs 18 at all.
;;  2. If running Lucid Emacs, Ediff requires at least version 19.9.
;;  3. The function ediff-revision requires the version of vc.el that comes
;;     with Emacs 19.22 and later, or rcs.el version 1.67 or later.


;;; Installation and use:
;;  --------------------

;; You can invoke Ediff interactively using the following functions:
;;
;;  	    ediff-buffers   	    	    	 - compare buffers
;;  	    ediff   	    	    	    	 - alias for ediff-files)
;;  	    ediff-files   	    	    	 - compare files
;;  	    ediff-patch-file	    	    	 - patch file then compare
;;  	    epatch  	    	    	    	 - alias for ediff-patch-file
;;  	    ediff-patch-buffer	    	    	 - patch buffer then compare
;;  	    epatch-buffer   	    	    	 - alias for ediff-patch-buffer
;;  	    ediff-revision 	    	    	 - compare buffer & version
;;
;;
;; To use Ediff, put this in your .emacs file:
;;
;;  (autoload 'ediff-buffers "ediff" "Visual interface to diff" t)
;;  (autoload 'ediff  "ediff"  "Visual interface to diff" t)
;;  (autoload 'ediff-files "ediff" "Visual interface to diff" t)
;;  (autoload 'epatch  "ediff"  "Visual interface to patch" t)
;;  (autoload 'ediff-patch-file "ediff" "Visual interface to patch" t)
;;  (autoload 'ediff-patch-buffer "ediff" "Visual interface to patch" t)
;;  (autoload 'epatch-buffer "ediff" "Visual interface to patch" t)
;;  (autoload 'ediff-revision "ediff"
;;  	    	    	"Interface to diff & version control" t) 
;;
;;
;; If you want Ediff to be loaded from the very beginning, you should have
;;
;;  (require 'ediff)
;;
;; in your .emacs file.  This way it is also easier to figure out changes
;; to the default Ediff setting, if such changes become necessary --- see
;; Customization.
;;

;;; Compilation
;;  -----------
;;
;; When you byte-compile Ediff, you will get some warnings about functions
;; being undefined.  These can be safely ignored.
;;
;;   Important:
;;   =========
;;
;;    If you are using advice.el (directly or indirectly, via one of the
;;    other packages), Ediff may not compile properly.  In this case, you
;;    should do:
;;
;;    	  M-x ad-deactivate-all RET
;;
;;  	  M-x byte-compile-file RET ediff.el RET
;;
;;  	  M-x ad-activate-all RET
;;
;;    This precaution will not be needed starting with GNU Emacs 19.23 and
;;    Lucid Emacs 19.10, due to fixing a bug in advice.el.

;;; Customization:
;;  -------------

;; Hooks:
;; -----
;; If you don't like the default setting, you can change it through the
;; various variables and hooks.  In particular, the following hooks are
;; available: 

;;	    ediff-load-hooks
;;  	    ediff-before-setup-windows-hooks
;;  	    ediff-startup-hooks
;;  	    ediff-select-hooks
;;  	    ediff-unselect-hooks
;;  	    ediff-suspend-hooks
;;  	    ediff-quit-hooks
;;  	    ediff-prepare-buffer-hooks

;; The hooks in ediff-load-hooks can be used to change defaults after Ediff
;; is loaded.
;; The hooks in ediff-before-setup-windows-hooks, ediff-suspend-hooks, and
;; ediff-quit-hooks can be used to save and then restore whatever window
;; configuration you want.  However, make sure you understand what you are
;; doing.  Many variables that drive Ediff are local to the different
;; Ediff Control Panel buffers.  Take a look at ediff-default-suspend-hook and
;; ediff-default-quit-hook to see what's involved.
;; The hooks in ediff-prepare-buffer-hooks are executed for each Ediff buffer
;; (A and B) right after these buffers are arranged.
;;
;;
;; Selective browsing: Control over stepping through difference regions
;; ----------------------------------------------- 
;;
;; Sometimes it is convenient to be able to step through only some
;; difference regions, those that satisfy certain conditions and to ignore
;; all others. The commands `#f' and `#h' let the user specify regular
;; expressions to control the way Ediff skips to the next or previous
;; difference. Typing `#f' lets one specify a pair of regular expressions,
;; regexp-A and regexp-B.
;; Ediff will then start stepping only through those difference regions where
;; the region in buffer A matches regexp-A and the region in buffer B
;; matches regexp-B.
;; Similarly, using `#h', one specifies expressions that match difference
;; regions to be ignored while stepping through the differences. That is, if
;; the buf A part matches regexp-A and the buf B part matches regexp B then
;; the region will be ignored by ediff-next-difference and
;; ediff-previous-difference commands.
;;
;;  Hitting `#f' and `#h' toggles this feature on/off.
;;
;; Note that selective browsing affects only ediff-next-difference and
;; ediff-previous-difference, i.e., the commands invoked by typing n/SPC
;; and p/DEL. You can still jump directly (using `j' or `ga/gb') to any
;; numbered  difference. Also, it should be understood, that #f and #h do
;; not change the position of the point in the buffers. The effect of these
;; commands is seen only when the user types `n' or `p', i.e., when
;; Ediff is told to jump to the next or previous difference.
;;
;; Users can supply their own functions that specify how Ediff should do
;; selective browsing. To change the default Ediff function, add a function to
;; ediff-load-hooks which will do the following assignments:
;;
;;  	(fset ediff-hide-regexp-matches 'your-hide-function) 
;;  	(fset ediff-focus-on-regexp-matches 'your-focus-function)
;;
;; Useful hints: To specify a regexp that matches everything, don't simply
;; type RET in response to a prompt. Typing RET tells Ediff to accept the
;; default value, which may not be what you want. Instead, one should enter
;; something like `^' or `$' --- which would match every line. 
;;
;; If the user doesn't remember if selective browsing is in effect and
;; which regexps are being used, the status command, `i', will supply
;; the requisite information.
;;
;; In addition to the ability to ignore regions that match regular
;; expressions, Ediff can be ordered to start skipping over certain
;; `inessential' regions. This is controlled by the variable
;;
;;      ediff-ignore-similar-regions
;;
;; which, if set to t, will cause Ediff to skip over difference regions
;; that has been found similar, i.e., where the only differences are those
;; in the white space and newlines.
;;
;; Note: In order for this feature to work, auto-refining of difference
;; regions must be on, since otherwise Ediff won't know if there are no
;; fine differences between regions. Under X, auto-refining is a default,
;; but it is nixed on a dumb terminal or in an Xterm window. Therefore, in
;; a non-windowing environment, the user must explicitly turn
;; auto-refining on (e.g., by typing `@').
;;
;; CAUTION: If many inessential regions appear in a row, Ediff may take a
;; long time to jump to the next region because it has to compute fine
;; differences of all intermediate regions.
;;
;;
;; Highlighting difference regions
;; -------------------------------
;; The second group of Ediff variables that could be changed, if you so
;; wish, is: 
;;
;;  	    ediff-before-flag-eol
;;  	    ediff-after-flag-eol
;;  	    ediff-before-flag-mol
;;  	    ediff-after-flag-mol
;;
;;  	    ediff-current-diff-face-A
;;  	    ediff-current-diff-face-B
;;  	    ediff-fine-diff-face-A
;;  	    ediff-fine-diff-face-B
;;  	    ediff-even-diff-face-A
;;  	    ediff-even-diff-face-B
;;  	    ediff-odd-diff-face-A
;;  	    ediff-odd-diff-face-B
;
;; The first four are ASCII strings that mark the beginning and the end of
;; the differences found in file-A and file-B. Ediff uses different flags
;; to highlight regions that begin/end at the beginning of a line or in a
;; middle of a line.

;; The rest are the faces used to highlight text on X displays.  On X
;; displays, Ediff uses ediff-current-diff-face-A and
;; ediff-current-diff-face-B to highlight the current difference regions.
;; The faces ediff-fine-diff-face-A and ediff-fine-diff-face-B
;; are used to show the fine differences between the current differences
;; regions in buffer A and B.
;; Other (non-current) difference regions are displayed in alternating
;; faces: ediff-even/odd-diff-face-A/B.   The odd and the even
;; faces are actually identical on monochrome displays, because it is
;; rather poor in what you can do on such a display. So, I chose to use
;; italics to highlight other differences. Any ideas would be welcome.
;; There are two ways to change the default setting for highlighting faces:
;; either change the variables, as in
;;
;; (setq ediff-current-diff-face-A 'bold-italic)
;;
;; or
;;
;; (setq ediff-current-diff-face-A
;;  	 (copy-face 'bold-italic 'ediff-current-diff-face-A))
;;
;; or by selectively modifying the defaults:
;;
;; (add-hook 'ediff-load-hooks
;;   (function (lambda () 
;;                (set-face-foreground ediff-current-diff-face-B "blue")
;;                (set-face-background ediff-current-diff-face-B "red")
;;                (make-face-italic ediff-current-diff-face-B))))
;;
;; You may also want to take a look at how the above faces are defined in
;; Ediff. 
;;
;; Note: it is not recommended to use `internal-get-face' (or `get-face' in
;;  	 Lucid) when defining faces for Ediff, since this may cause
;;  	 problems when there are several frames with different font sizes.
;;       Instead, use copy-face or set/make-face-* as shown above.
;;
;; The last group of variables in this group,
;;
;;  	    ediff-want-faces
;;  	    ediff-highlight-all-diffs
;;  	    ediff-want-default-menus
;;
;; indicate whether---on a window system---you want differences to be
;; marked using ASCII strings (like on a dumb terminal) or using colors and
;; highlighting. If ediff-want-faces is t, then highlighting with faces is
;; used. Normally, Ediff highlights all differences, but the selected
;; difference is highlighted more visibly. You can cycle through various
;; modes of highlighting by hitting `h'. By default, Ediff starts in the
;; mode where all difference regions are highlighted. If you prefer to
;; start in the mode where unselected differences are not highlighted, you
;; should set ediff-highlight-all-diffs to nil. 
;; You will still be able to turn on highlighting of all differences by
;; hitting `h'.
;; The variable `ediff-want-default-menus', if true, will cause Ediff to
;; set up a pair of menues in the menu bar, so you can invoke it from there.
;; If you don't like the look of the default menus, set this variable to
;; nil and design your own menus.
;;
;; If you plan on changing these variables, they must be set
;; BEFORE ediff.el is loaded. 
;;
;; Note: Ediff lets you switch between the two types of highlighting.  That
;; is you can switch, interactively, from highlighting using faces to
;; highlighting using ASCII flags, and back.  Of course, toggling has
;; effect only on a window system.  On a dumb terminal or in an xterm
;; window, the only available option is highlighting with ASCII flags.
;;
;; Refining difference regions
;; ---------------------------
;; Ediff has variables that control the way fine differences are
;; highlighted. This feature lets the user highlight the exact words that 
;; make the difference regions in buffer A and B different. This process
;; ignores spaces, tabs, and newlines.
;;
;;  	    ediff-auto-refine
;;  	    ediff-auto-refine-limit
;;
;; By default, `ediff-auto-refine' is `'on', which means that fine differences
;; within regions will be highlighted automatically. On a slow system, this
;; feature may be undesirable. In any case, the user can always toggle
;; auto-refining on/off/nix by hitting `@'. When auto-refining is off, fine
;; differences will be shown only for regions for which these differences
;; have been computed and saved before. If auto-refining is nixed, fine
;; differences will not be shown at all. Hitting `*' will compute and
;; display fine differences for the current difference region regardless of
;; whether auto-refining is on, off, or nixed. 
;; If auto-refining is on, the variable `ediff-auto-refine-limit' limits
;; the size of the regions to be auto-refined. This variable guards against
;; possible slow-down that may be caused by an extraordinary large
;; difference region. However, the user can always force refining by
;; hitting `*'.
;;
;;  	    ediff-fine-diff-program
;;  	    ediff-fine-diff-options
;;  	    ediff-forward-word-function
;;
;; These variables let the user control how fine differences are computed.
;; `ediff-fine-diff-program' is diff, by default. However, you can use
;; any function as long as it produces output consistent with diff.
;; `ediff-forward-word-function' is a lisp function that determines how the
;; current difference region is split into words. (Fine diferences are
;; computed by first splitting the current difference region into words and
;; then passing this along to `ediff-fine-diff-program'. For the default
;; wordify function, `ediff-forward-word', a word is a string consisting of
;; letters, `-', or `_', or a string consisting of symbols that are neither
;; space, nor a letter.)
;;
;; Patch and diff programs
;; -----------------------
;; The next group of variables determines the programs to be used for
;; applying patches and for computing the main difference regions (not the
;; fine difference regions):
;;
;;  	    ediff-patch-program
;;  	    ediff-patch-options
;;  	    ediff-diff-program
;;  	    ediff-diff-options
;;
;; These specify the functions that produce differences and do patching.
;; The *-options variables specify which options to pass to these programs.
;; It is unlikely that you would want to change these.  One possible
;; exception is when you may want to generate differences with context
;; lines in order to send a patch file through email.  Then, you might want
;; to set ediff-diff-options to '-c'. Sometimes, you may also want to tell
;; diff to ignore spaces and such. Use the option '-w' for that. Diff
;; has several other useful options (type 'man diff' to find out).
;;
;; The output from diff is found in *ediff-diff* buffer, which you can save.
;; However, using Ediff for producing a diff output makes sense only if you
;; also intend to use Ediff to browse through the diff'ed files before
;; sending the patch.  This is because diff.el, which also comes with
;; Emacs, is much faster in yielding the output of diff  (Ediff is a big
;; gun, if used for this simple purpose).
;;
;; Mode line
;; ---------
;;
;; When Ediff is running, the mode line of Ediff Control Panel buffer
;; displays the current difference being displayed and the total number of
;; difference regions in the two files. 
;;
;; The mode line of the buffers being compared displays the type of the
;; buffer (`A:' or `B:') and (usually) the file name. Ediff is trying to be
;; intelligent in choosing mode line buffer identification. In particular,
;; it works well with uniquify.el and mode-line.el packages (which improve
;; on the default way in which Emacs displays buffer identification).
;; If you don't like the way Ediff identifies its buffers, there is always
;; ediff-prepare-buffer-hooks, which can be used to modify the mode line.
;;
;; Miscellaneous
;; -------------
;; The last set of variables that can be modified is
;;
;;  	    ediff-split-window-function
;;  	    ediff-use-last-dir
;;  	    ediff-no-help-in-control-buffer
;;  	    ediff-toggle-read-only-function
;;
;; ediff-split-window-function controls the way you want the window be
;; split between file-A and file-B.  It defaults to vertical split, but you
;; can set it to 'split-window-horizontally, if you want.  Ediff lets you
;; toggle the way windows are split, so you can try different settings
;; interactively.  Note: if file-A and file-B are in different frames,
;; windows are not split, regardless of the value
;; ediff-split-window-function.  Instead, other windows on these frames are
;; deleted and Ediff starts displaying file-A and file-B using these two
;; frames, one file per frame.  You can then switch to one-frame mode
;; simply by hiding the file-A/B buffer that is displayed on a frame other
;; than the control-window frame.
;;
;; Note that if Ediff sees that the two buffers it compares are residing in
;; separate frames, it assumes that the user wants them to be so displayed
;; and stops splitting windows.  Instead, it will arrange each buffer to
;; occupy its own frame (possibly shared with Ediff's help window).
;;
;; The variable ediff-use-last-dir controls the way Ediff presents the
;; default directory when it prompts the user for files to compare.  If nil,
;; Ediff will use the default directory of the current buffer when it
;; prompts the user for file names.  Otherwise, it will use the
;; directories it had previously used for file-A and file-B. 
;;
;; The variable ediff-no-help-in-control-buffer, if set to t, makes C-h
;; behave like the DEL key, i.e., it will move you back to the previous
;; difference rather than invoking help.  This is useful when, in an xterm
;; window or on a dumb terminal, the Backspace key is bound to C-h and is
;; positioned more conveniently than the DEL key.
;;
;; The variable ediff-toggle-read-only-function can be used to change the
;; way Ediff toggles the read-only property in its buffers.
;; By default, Ediff uses toggle-read-only. For files under version
;; control, Ediff first tries to check the files out.


;;; Commands
;;  --------

;; All Ediff commands are displayed in a help window, unless you hit '?' to
;; shrink it to just one line.  You can redisplay the help window by hitting
;; '?' again.
;;
;; Many Ediff commands take numeric prefix arguments.  For instance, if you
;; hit a number, N, and then 'j' (ediff-jump-to-difference), Ediff will
;; take you to Nth difference.  Hitting a number, N, and then 'ab'
;; (ediff-diff-to-diff) will copy Nth difference from buffer A to buffer B.
;; Hitting 'ba' does copying in the other direction.
;; Likewise, a number, N, followed by 'ra' will restore the Nth difference
;; region in buffer A (if it was previously saved as a result of copying
;; from B to A). 
;;
;; Without the prefix argument, all commands operate on the current
;; difference region.
;;
;; The total number of differences and the current difference number are
;; always displayed in the mode line of the control window. 
;;
;; If, after making changes to buffers A and B, you decide to save them, it
;; is recommended to use `ediff-save-buffer', which is bound to `wa' and
;; `wb' (`wa will save buffer A and `wb' saves buffer B).
;;
;; Typing `wf' will also save the diff output in a file. 

;;; Display Modes
;;  -------------

;; Ediff can display files in one frame, stacked side-by-side or one on top
;; of another; or it can display the files in different frames.  When you
;; start Ediff, it assumes a 1-frame mode.  You can toggle the side-by-side
;; and one-on-top-of-another displays by simply hitting 's'.
;;
;; Ediff switches to the multi-frame mode when:
;;
;;  1. file-A and file-B are in different frames (you have to put them into
;;     different frames manually); or
;;  2. Ediff Control Panel is visible in one frame and one other file (A
;;     or B) is visible in another frame.  If, say, fileA is visible in a
;;     different frame than Ediff Control Panel, fileB doesn't have to be
;;     visible.  If it is, Ediff will continue displaying fileB in the frame
;;     where it was visible before.  If it isn't then Ediff will arrange for
;;     fileB to share a frame with Ediff Control Panel.
;;
;;  If all three buffers are in separate frames, Ediff will switch to a
;;  3-frame mode.  If Ediff buffers are currently visible only in two
;;  frames, Ediff will work in a 2-frame mode.  In this mode, one of the
;;  frames will be shared by Ediff Control Panel and file-A or file-B
;;  (whichever is appropriate).


;;; Bugs:
;;  ----

;;  1. The undo command doesn't restore deleted regions well. That is, if
;;  you delete all characters in a difference region and then invoke
;;  `undo', the reinserted text will most likely be reinserted outside of
;;  what Ediff thinks is the current difference region. (This problem
;;  doesn't seem to exist with Lucid Emacs.)
;;
;;  If at any point you feel that difference regions are no longer correct,
;;  you can hit '!' to recompute the differences.

;;  2. Emacs 19.xx, where xx < 23, has several bugs related to overlays and
;;  faces. Somethimes, these may cause highlighting of the refinements or
;;  of the unselected differences to disappear. Hitting `!' will bring them
;;  back.  In version 19.23 and later, these problems no longer occur.

;;  3. On a monochrome display, the repertoire of faces with which to
;;  highlight fine differences is limited. By default, Ediff is using
;;  underlining. However, if the region is already underlied by some other
;;  overlays, there is no simple way to temporarily remove that residual
;;  underlining. This problem occurs when a buffer is highlighted with
;;  hilit19.el or font-lock.el packages. If this residual highlighting gets
;;  in the way, you can do the following. Both font-lock.el and hilit19.el
;;  provide commands for unhighlighting buffers. You can either place these
;;  commands in `ediff-prepare-buffer-hooks' (which will unhighlight every
;;  buffer used by Ediff) or you can execute them interactively, at any time
;;  and on any buffer.

;;  4. In Lucid Emacs (statically linked with Motif libraries), emerge.el
;;  and hence ediff.el won't start, unless you set (setq scrollbar-width 0).
;;  This is a Motif-related bug, I was told.


;;; Change Log:
;;  ----------

;; Thu Feb  3, 1994 

;;     Added ediff-read-file-name, which is a stub that takes care of Lemacs
;;     versions of Emerge. (Thanks to Alastair Burt <[email protected]>.)
;;
;;     Fixed a bug in ediff-setup-windows that caused control window to
;;     appear in a wrong place when split-window-keep-point is nil
;;     (Thanks to Kevin Broadey <[email protected]>.)
;;
;;     Added mechanism for using faces instead of before/after flags.  This
;;     looks much better on an X display, especially on a color one.
;;     (Thanks to Boris Goldowsky <[email protected]> for the code
;;     that led to ediff-highlight-diff.
;;     Also, thanks to Kevin Esler <[email protected]> for suggestions
;;     regarding highlighting differences on X displays.)
;;
;;     Added functions to apply patches.
;;     (Thanks to Kevin Broadey <[email protected]> for this
;;     suggestion.)

;; Fri Feb  4, 1994 

;;     Added mechanism for toggling vertical/horizontal window split.
;;     (Inspired by a suggestion from Allan Gottlieb
;;     <[email protected]> -- thanks.)
;;
;;     Added mechanism for toggling between highlighting using faces and
;;     highlighting using ASCII flags.
;;
;;     Fixed a problem with undo.  Now, Ediff has smartened up and doesn't
;;     keep undo info on ASCII flags inserted in buffer-A and buffer-B.
;;     So, if you edit the files while browsing through them, undo behaves
;;     as you would expect, i.e., faces/flags don't get in the way.

;; Sun Feb  6, 1994 

;;     Added horizontal scrolling.  Added ediff-position-region to ensure
;;     that difference regions in buffer-A and buffer-B are aligned with
;;     each other.  Disabled ediff-toggle-split when buffers are displayed
;;     in different frames.

;; Mon Feb  7, 1994

;;     Added toggle-window help (Suggested by Boris Goldowsky
;;     <[email protected]>.)
;;     Added functions to copy differences from one buffer to another and to
;;     recover old differences.
;;     Added prefix arguments to ediff-next-difference and
;;     ediff-previous-difference.

;; Tue Feb  8, 1994

;;     Replaced text properties with overlays.  Fixed ediff-setup-windows.
;;     Added ediff-save-buffer to local-write-file-hooks to prevent user
;;     from saving corrupted states. (Thanks to <[email protected]>
;;     for suggestion.)  Instead, Ediff now has a pair of functions for
;;     safe saving of buffers. 
;;     Changed ediff-read-file-name to be more intuitive on ediff-files.
;;     Added ediff-prepare-buffer-hooks. (Thanks to Kevin Esler
;;     <[email protected]> for the idea.)

;; Wed Feb  9, 1994

;;     Cleanups in ediff-patch-file.  Protected ediff-copy-diff against
;;     a bug that Emacs has in kill-region.

;; Thu Feb 10, 1994

;;     Added support for Lemacs. (Thanks to Alastair Burt
;;     <[email protected]> for coercing Ediff into working under Lemacs.)
;;     Added ediff-kill-buffer-carefully and other suggestions by Boris
;;     Goldowsky <[email protected]>.
;;     Refined the protection against interference with highlighting caused
;;     by Hilit19.  Added the variable ediff-third-party-highlighting.
;;     Added mechanisn for unhighlighting regions highlighted with Hilit19
;;     before hightlighting them with Ediff's overlays. (And for
;;     rehighlighting them with Hilit19, when the current difference moves on.)

;; Sun Feb 13, 1994

;;     Added ediff-place-flags-in-buffer and ediff-remote-exit, which are
;;     modifications of Emerge's similar functions.  The difference is that
;;     in Ediff they make ediff-before-flag and ediff-after-flag into
;;     read-only regions, so the user can't change them by mistake.
;;
;;     Adopted a suggestion by Boris Goldowsky <[email protected]>
;;     that led to a more elegant treatment of faces.
;;
;;     Added protection against interference with Font-Lock highlighting
;;     similar to that of Hilit19's protection.

;; Tue Feb 15, 1994

;;     Deleted spurious (auto-save-mode 1) in ediff-control-buffer, which
;;     was causing this buffer to be auto-saved for no good reason.
;;     Added read-only protection to ediff-before/after-flags in Lemacs.
;;     (Thanks to Alastair Burt <[email protected]> for help in testing.)

;; Wed Feb 16, 1994

;;     Further fixes in the Lemacs part.  Changed highlighted region in
;;     ediff-highlight-diff so that an extra character will be highlighted
;;     only if a difference is empty (thereby allowing the user to see where an
;;     insertion or a deletion has taken place).
;;
;;     Simplified interaction with other highlighting packages by giving
;;     Ediff overlays the highest priority. (Taking a cue from
;;     ediff-highlight-diff-lemacs written by Alastair Burt
;;     <[email protected]>.) Zapped ediff-third-party-highlighting
;;     variable and hooks that were previously used to
;;     unhighlight/rehighlight buffers when hilit19/font-lock are on.

;; Fri Feb 18, 1994

;;     Added a bit more sophistication to ediff-read-file-name.  Now,
;;     ediff-files remembers both, the file-A and the file-B directories.
;;     They are offered as defaults when ediff-use-last-dir is set to t.

;; Fri Feb 22, 1994

;;     Added ediff-before-change-guard to remove ASCII highlighting when
;;     the user attempts to change buffer-A/B.  This is needed because
;;     otherwise the undo info may become screwed up in those buffers.
;;     Hitting 'h' (ediff-toggle-hilit) on a dumb terminal will toggle
;;     between ASCII highlighting and no highlighting.

;; Fri Feb 24, 1994

;;     Fixed problems with multiple Ediff sessions running simultaneously.

;; Tue Mar 1, 1994

;;     Added vc-ediff, the Ediff interface to vc.el. (Thanks to Eric
;;     Freudenthal <[email protected]> for contributing this
;;     function.) 

;; Sun Mar 6, 1994

;;     Added rcs-ediff, an Ediff interface to RCS via rcs.el. (Thanks to
;;     Alastair Burt  <[email protected]>.)
;;     Some minor improvements.

;; Tue March 15, 1994

;;     Fixed a buglet in defining ediff-current-diff-face-A/B.
;;     (Thanks to Job Ganzevoort  <[email protected]>.) 

;; Tue March 22, 1994

;;     Fixed a bug with ediffing narrowed buffers, reported by Kevin
;;     Broadey <[email protected]>.
;;     Made Ediff to work with files that have incomplete last line.
;;     Made Ediff execute diff and patch using Bourne Shell, which
;;     should eliminate problems with $prompt that some people had.

;; Thu March 24, 1994

;;     Achieved quadratic speedup in the size of the file by replacing the
;;     slow goto-line by forward-line.  Ediff is now *much* faster than
;;     Emerge on large files.  Converted demarkation of difference regions
;;     from markers to overlays.  This will later allow us to highlight all
;;     diffs, not just the current one.

;; Wed March 30, 1994

;;     Under X, Ediff now highlights all differences in dim colors and the
;;     current difference in bright colors. Improved Lucid Emacs support.

;; Thu March 31, 1994

;;     Changed toggle hilit to cycle through 3 states: highlighting all
;;     diffs, highlighting only the current diff, and highlighting using
;;     ASCII flags.
;;     Added support for difference regions that are not full lines.

;; Fri April 1, 1994

;;     Fixed bugs related to writing buffers A and B.
;;     Added commands 'ga', 'gb' to jump directly to the closest diff in
;;     buffer A and B, respectively.

;; Fri April 11, 1994

;;     Added `ediff-recompute-diffs', a function that lets the user recompute
;;     difference regions after extensive editing done to buffers A and B
;;     (bound to `!').

;; Wed April 13, 1994

;;     Added the new feature: refining the current difference region.
;;     This would highlight the precise differences between the regions in
;;     buffer A and B. (A way to implement this was suggested by Boris
;;     Goldowsky <[email protected]>.)
;;
;;     Fixed Ediff to be immune to several different versions of rcs.el
;;     that are currently in distribution.

;; Thu April 14, 1994

;;     Ediff now respects X resources for the faces it uses. It no longer
;;     barks when the colormap has no colors it is using; or when face
;;     fonts can't be italicized, etc.

;; Fri April 15, 1994

;;     Changed `ediff-setup-windows' to minimize the need to delete and
;;     create windows. Now jumps faster from diff to diff.

;; Sat April 16, 1994

;;     Added Ediff to the File menu on the menu bar (FSF's version).

;; Mon April 18, 1994

;;     Fixed to work with OS/2's PM-Emacs.

;; Thu April 21, 1994

;;     Lemacs' menus added (thanks to Alastair Burt for the help).

;; Wed April 28, 1994

;;     Fixed ediff-leave-window-config (thanks to Norbert Kiesel 
;;     <[email protected]>), ediff-shell and
;;     ediff-protect-metachars (thanks to Richard Stanton
;;     <[email protected]>). Made access to difference
;;     overlays structure-independent, making it less bug-prone.
;;     Patched ediff-read-file-name to work more intuitively with directory
;;     names (thanks to Kevin Broadey <[email protected]>).

;; Mon May 2, 1994

;;     Added `ediff-frame-has-menubar' to guard against the possibility that
;;     the current frame has no menu bar.

;; Fri May 6, 1994

;;     Fixed buglet in vc-ediff (thanks to Ray Nickson <[email protected]>).

;; Wed May 18, 1994

;;     Modified ediff-read-file-name to not put long file names in the
;;     default prompt area, as suggested by [email protected].
;;     Applied patch supplied by [email protected], fixing a problem with
;;     ediff-diff-to-diff in Lemacs.

;; Tue May 31, 1994

;;     Added ediff-forward-word-function (as suggested by Job Ganzevoort
;;     <[email protected]>). Modified ediff-default-quit-hook so it
;;     will clean things up in a more satisfactory way.

;; Thu Jun 2, 1994

;;     Added `ediff-toggle-regexp-match', which allows the user to step
;;     through only those difference regions that match some regexp; or,
;;     vice versa, to skip over regions that match a regexp. (This feature
;;     was suggested by Andy Scott <[email protected]>.)
;;     Added ediff-eval-in-buffer, which is a modified emerge-eval-in-buffer.
;;     The function ediff-status-info, bound to `i', now replaces and extends
;;     ediff-file-names and ediff-line-numbers, which were bound to `f'
;;     and `i', respectively.

;; Wed Jun 8, 1994

;;     Made `ediff-frame-has-menubar' into a function; copied
;;     `emerge-defvar-local' and turned it into `ediff-defvar-local' 
;;     This is supposed to make the same ediff.elc file work for both Emacs
;;     and Lucid Emacs, at least, if compiled under Lucid Emacs. (Thanks
;;     to Eric Eide <[email protected]>.)

;; Wed Jun 10, 1994

;;     Improved `ediff-read-file-name' and `ediff-buffers' so they are now
;;     providing more intuitive defaults. Modified `ediff-read-file-name'
;;     so it won't cause problems under OS/2.

;; Fri Jun 24, 1994

;;     Modified ediff-find-file, ediff-files-internal, and made
;;     emerge-verify-file-buffer into ediff-verify-file-buffer so that
;;     Ediff will work correctly with remote and compressed
;;     files. (Suggested by Sandy Rutherford <[email protected]>.)

;; Fri Jun 28, 1994

;;     Fixed ediff-patch-files to work with remote and compressed files.

;; Wed July 20, 1994

;;     Changed menu bar items per RMS's suggestion. Changed odd/even faces
;;     in Lemacs to italic.  Changed ediff-*-face-* variables so that they
;;     will contain names of faces instead of the face internal
;;     representation.  (Copy-face works better with face names than with
;;     face internal representation.  With face internal representation, if
;;     a face vector mentions a font explicitly, copy-face may attempt to
;;     copy this font, which would cause an error if the font has a wrong
;;     size for one of the existing frames.)  Improved the way
;;     mode-line-buffer-identification is set in ediff-setup so that Ediff
;;     will accommodate the way buffers are identified in mode-line.el and
;;     uniquify.el.

;; Fri August 5, 1994

;;     Ediff can now automatically skip over regions that differ only in
;;     the white space and line breaks. This is controled with the variable
;;     `ediff-ignore-similar-regions' and can be toggled on/off by typing
;;     `##'.

;; Mon August 8, 1994

;;     If ediff-save-buffer is invoked with `wf', it'll save the diff
;;     output in a file.

;; Wed August 24, 1994

;;     Fixed ediff-toggle-read-only and ediff-patch-file so that they will
;;     check out version-controled files before modifying them. This will
;;     permit checking the modified versions back in. In earlier
;;     versions, such modifications could be lost, unless the user takes
;;     special care of preserving them.

;; Tue August 30, 1994

;;     Added ediff-submit-report.
;;     Introduced ediff-revision as a uniform way of calling vc.el and
;;     rcs.el. This is controled by ediff-version-control-package
;;     variable. Functions vc-ediff, rcs-ediff are replaced by their
;;     internal versions.
;;     Added ediff-find-file-name-handler function to smooth out the
;;     transition from Emacs 19.22/Lucid 19.9 to 19.23/19/10

;; Thus September 1, 1994

;;     Made ediff-overlay-put and ediff-move-overlay into bona fide
;;     functions (rather than fset symbols). These now check if overlay's
;;     buffer is alive. If not, overlay is deleted. This overcomes some of
;;     the problems with Lemacs.


;;; Acknowledgements:

;; Special thanks to Alastair Burt <[email protected]>, Kevin Esler
;; <[email protected]>, Kevin Broadey <[email protected]>, 
;; Harald Boegeholz <[email protected]>,
;; Robert Estes <[email protected]>, Eric Eide <[email protected]>,
;; Eric Freudenthal  <[email protected]>, Job Ganzevoort 
;; <[email protected]>, Boris Goldowsky <[email protected]>,
;; Allan Gottlieb <[email protected]>, Xiaoli Huang
;; <[email protected]>, [email protected], [email protected],
;; David Karr, <[email protected]>, Norbert Kiesel 
;; <[email protected]>, Heinz Knutzen
;; <[email protected]>, Martin Maechler
;; <[email protected]>, Richard Mlynarik <[email protected]>,
;; Eyvind Ness <[email protected]>, Ray Nickson <[email protected]>,
;; Sandy Rutherford <[email protected]>,  Andy Scott
;; <[email protected]>, Richard Stallman <[email protected]>,
;; Richard Stanton, <[email protected]>, Peter Stout
;; <[email protected]> for contributing ideas, patches, and bug reports. 
;;
;; Thanks also to many others who felt obliged to drop a thanks note.



;;; Code:

(require 'emerge) ;; Ediff uses some functions defined in emerge.el


;;; Macros
(defmacro ediff-if-lucid ()
  (` (string-match "Lucid" emacs-version)))

(defmacro ediff-odd-p (arg)
  (` (eq (logand (, arg) 1) 1)))

(defmacro ediff-buffer-live-p (buf)
  (` (and (, buf) (get-buffer (, buf)) (buffer-name (get-buffer (, buf))))))

(defmacro ediff-get-buffer (arg)
  (` (cond ((eq (, arg) 'A) ediff-A-buffer)
	   ((eq (, arg) 'B) ediff-B-buffer)
	   )
  ))
	   
(defmacro ediff-char-to-buftype (arg)
  (` (cond ((eq (, arg) ?a) 'A)
	   ((eq (, arg) ?b) 'B)
	   )
  ))
  
(defmacro ediff-get-difference (n)
  (` (aref ediff-difference-vector (, n))))
  
;; tell if it has been previously found that the region doesn't
;; contain diffs other than the white space and newlines
;; The argument, N, is the diff region number used by Ediff to index the
;; diff vector. It is 1 less than the number seen by the user.
(defmacro ediff-no-fine-diffs (n)
  (` (aref (ediff-get-difference n) 3)))
  
(defmacro ediff-get-diff-overlay-from-vector (vec buf-type)
  (` (aref (, vec)
	   (cond ((eq (, buf-type) 'A) 0)
		 ((eq (, buf-type) 'B) 1)
		 )
	   )))
  
(defmacro ediff-get-diff-overlay (n buf-type)  
  (` (ediff-get-diff-overlay-from-vector
      (ediff-get-difference (, n))
      (, buf-type))))

(defmacro ediff-get-fine-diff-vector-from-vec (current-diff-vec)
  (` (aref (, current-diff-vec) 2)))
      
(defmacro ediff-set-fine-diff-vector (n fine-vec)
  (` (aset (ediff-get-difference (, n)) 2 (, fine-vec))))

;; if flag is t, puts a mark on diff region saying that 
;; the differences are in white space only. If flag is nil,
;; the region is marked as essential (i.e., differences are
;; not just in the white space and newlines.)
(defmacro ediff-mark-diff-as-space-only (n flag)
  (` (aset (ediff-get-difference (, n)) 3 (, flag))))
  
(defmacro ediff-get-fine-diff-vector (n)
  (` (ediff-get-fine-diff-vector-from-vec (ediff-get-difference (, n)))))
  
  
(defmacro ediff-defvar-local (var value doc) 
  "Defines SYMBOL as an advertised local variable.  
Performs a defvar, then executes `make-variable-buffer-local' on
the variable.  Also sets the `preserved' (Emacs) or `permanent-local' (Lucid)
property, so that `kill-all-local-variables' (called by major-mode setting
commands) won't destroy Ediff control variables.

This is a merge of `emerge-defvar-local' for Emacs and Lucid Emacs.  It is
needed to make the same ediff.elc work under both Emacsen."
  (` (progn
       (defvar (, var) (, value) (, doc))
       (make-variable-buffer-local '(, var))
       (put '(, var)
	    (if (ediff-if-lucid) 'permanent-local 'preserved)
	    t))))
    
(defmacro ediff-eval-in-buffer (buffer &rest forms)
  "Macro to switch to BUFFER, evaluate FORMS, returns to original buffer.
Differs from `save-excursion' in that it doesn't save the point and mark.
This is essentially `emerge-eval-in-buffer' with the test for live buffers."
  (` (let ((StartBuffer (current-buffer)))
       (if (ediff-buffer-live-p (, buffer))
	   (unwind-protect
	       (progn
		 (set-buffer (, buffer))
		 (,@ forms))
	     (set-buffer StartBuffer))
	 (beep 1)
	 (message "You seem to have killed an essential Ediff buffer---quit!"))
       )))


;;; Functions

(defun ediff-mode ()
  "Ediff mode is used by the Ediff file-difference package.
It is entered only through one of the following commands:
	`ediff'
	`ediff-files'
	`ediff-buffers'
	`epatch'
	`ediff-patch-file'
	`ediff-patch-buffer'
	`epatch-buffer'
	`ediff-revision'

Commands:
\\{ediff-mode-map}"
  (interactive)
  (kill-all-local-variables)
  (setq major-mode 'ediff-mode)
  (setq mode-name "Ediff"))

(defun ediff-version ()
  "Return string describing the version of Ediff.
When called interactively, displays the version."
  (interactive)
  (if (interactive-p)
      (message (ediff-version))
    (format "Ediff %s of %s" ediff-version ediff-date)))


;; Hook variables

(defvar ediff-before-setup-windows-hooks nil
  "*Hooks to run before Ediff sets its own window config. 
This can be used to save the previous window config, which can be restored
on ediff-quit or ediff-suspend.") 
(defvar ediff-startup-hooks nil
  "*Hooks to run in the control buffer after Ediff has been set up.")
(defvar ediff-select-hooks nil
  "*Hooks to run after a difference has been selected.")
(defvar ediff-unselect-hooks nil
  "*Hooks to run after a difference has been unselected.")
(defvar ediff-prepare-buffer-hooks  nil
  "*Hooks called after buffers A and B are set up.")
(defvar ediff-load-hooks nil
  "*Hook run after Ediff is loaded.  Can be used to change defaults.")

(defvar ediff-suspend-hooks (list 'ediff-default-suspend-hook)
  "*Hooks to run in the Ediff control buffer when Ediff is suspended.")
(defvar ediff-quit-hooks (list 'ediff-default-quit-hook)
  "*Hooks to run in the Ediff control buffer after finishing Ediff.") 

(make-variable-buffer-local 'local-write-file-hooks)
(make-variable-buffer-local 'before-change-function)

;; Help messages

(defconst ediff-help-message-long
  "    Moving around      |     Toggling features     |       Miscellaneous
=======================|===========================|===========================
p,DEL -previous diff   |     s -vert/horiz split   | ab/ba -copy diff A->B/B->A
n,SPC -next diff       |     h -hiliting           | ra/rb -restore diff in A/B
    j -jump to diff    |     @ -auto-refining      |     * -refine diff
ga/gb -to point in A/B |---------------------------|     ! -recompute diffs
    c -recenter        |    ## -skip whitespace    |---------------------------
  v/V -scroll up/down  | #f/#h -focus/hide regions | wa/wb -save buf A/B
  </> -scroll lft/rght |   A/B -read-only buf A/B  |    wf -save diff output
=======================|===========================|===========================
		       |   bug -submit bug report  |
    i -status info     |     ? -toggle help window |   z/q -suspend/quit Ediff"
  )
			  
(defconst ediff-help-message-short
  "                             ? - toggle help window")

(defvar ediff-help-message ediff-help-message-long
  "*The actual help message.")
 
;; diff stuff.
(defvar ediff-diff-program "diff"
  "*Name of the program that compares two files.")
(defvar ediff-diff-options ""  
  "*Options to pass to `ediff-diff-program'. 
If diff\(1\) is used as `ediff-diff-program', then the most useful options are
`-w', to ignore space, and `-i', to ignore case of letters.")
  
;; Fine differences 
(defvar ediff-forward-word-function 'ediff-forward-word
  "*Function to call to move to the next word.
Used for splitting difference regions into individual words.")

(defvar ediff-fine-diff-program "diff"
  "*Name of the program that compares the current diff regions for fine differences.
  
This program should produce output in the format of diff. One could
possibly use `spiff' here if appropriate options are set.")

(defvar ediff-fine-diff-options ""  
  "*Options to pass to `ediff-fine-diff-program'.
If diff\(1\) is used as `ediff-diff-program', then the most useful options are
`-w', to ignore space, and `-i', to ignore case of letters.")
  
(defvar ediff-whitespace " \n\t\C-j"
  "*White space. Used to split strings into words.")

(defvar ediff-word-1 "a-zA-Z---_`'.?!:"
  "*Characters matching this regexp constitute words of type 1.
  
Ediff is using a very simple schema for splitting text into words, which is
used to determine fine differences between regions. There are two types of
words. One consists entirely out of characters in `ediff-word-1'  and
another out of characters matching `ediff-word-1'.")

(defvar ediff-word-2 "^a-zA-Z---_`'.?!: \t\n\C-j"
  "*Characters matching this regexp constitute words of type 2.
See `ediff-word-1' for more details.")  

;; Selective browsing

(ediff-defvar-local ediff-skip-diff-region-function 'ediff-show-all-diffs
  "Function that determines the next/previous diff region to show.
Should return t for regions to be ignored and nil otherwise.
This function gets a region number as an argument. The region number
is the one used internally by Ediff. It is 1 less than the number seen
by the user.")

(ediff-defvar-local ediff-regexp-focus-A ""
  "Regexp that determines buf A regions to focus on when skipping to diff.")
(ediff-defvar-local ediff-regexp-focus-B ""
  "Regexp that determines buf B regions to focus on when skipping to diff.")
  
(ediff-defvar-local ediff-regexp-hide-A ""
  "Regexp that determines buf A regions to ignore when skipping to diff.")
(ediff-defvar-local ediff-regexp-hide-B ""
  "Regexp that determines buf B regions to ignore when skipping to diff.")  
  

;; Support for patches 

(defvar ediff-patch-program "patch"
  "*Name of the program that applies patches.")
(defvar ediff-patch-options ""
  "*Options to pass to ediff-patch-program.")
  
(defvar ediff-shell (cond ((eq system-type 'emx) "cmd") ;; OS/2
			  (t  "sh")) ;; unix
  "*The shell used to run diff and patch.  If user's .profile or
.cshrc files are set up correctly, any shell will do.  However, some people
set $prompt or other things incorrectly, which leads to undesirable output
messages.  These may cause Ediff to fail.  In such a case, set ediff-shell
to a shell that you are not using or, better, fix your shell's startup file.")
  
(defvar ediff-diff-ok-lines-regexp  
  "^\\([0-9,]+[acd][0-9,]+$\\|[<>] \\|---\\|Warning:\\)"
  "Regexp that matches normal output lines from `ediff-diff-program'.
This is mostly lifted from Emerge, except that Ediff also considers the
'Missing newline' message to be 'normal output.'
Lines that do not match are assumed to be error messages.")

(defvar ediff-fine-diff-ok-lines-regexp  
  "^\\([0-9,]+[acd][0-9,]+$\\|[<>] \\|---\\|Warning:\\)"
  "Regexp that matches normal output lines from `ediff-fine-diff-program'.
This is mostly lifted from Emerge, except that Ediff also considers the
'Missing newline' message to be 'normal output.'
Lines that do not match are assumed to be error messages.")

(defvar ediff-match-diff-line (let ((x "\\([0-9]+\\)\\(\\|,\\([0-9]+\\)\\)"))
				(concat "^" x "\\([acd]\\)" x "$"))
  "Pattern to match lines produced by diff that describe differences.")
  
(defvar ediff-patch-buf nil
  "The buffer of the patch file.")
(defvar ediff-patch-diagnostics nil
  "The buffer where patch would display its diagnostics.")
  


;; Copying difference regions between buffers.    
(ediff-defvar-local ediff-killed-diffs-alist nil
  "A list of killed diffs. 
A diff is saved here if it is replaced by a diff
from another buffer.  This alist has the form:
\((num (A . diff) (B . diff)) ...),
where A or B parts may be missing.")


;; Highlighting
(defvar ediff-before-flag-bol
  ;"vvvvvvvvvvvvvvvv---- ediff ----vvvvvvvvvvvvvvv\n"
  ">>--->>>\n"
  "*Flag placed above the highlighted block of differences. 
Must end with newline.  Must be set before Ediff is loaded.")
(defvar ediff-after-flag-bol
  ;"^^^^^^^^^^^^^^^^---- ediff ----^^^^^^^^^^^^^^^\n"
  "<<<---<<\n"
  "*Flag placed below the highlighted block of differences.
Must end with newline.  Must be set before Ediff is loaded.")

(defvar ediff-before-flag-mol ">>--->>>"
  "*Like ediff-before-flag, used when a difference starts in mid-line.")
(defvar ediff-after-flag-mol "<<<---<<"
  "*Like ediff-after-flag, used when a difference starts in mid-line.")

(ediff-defvar-local ediff-before-flag-A nil
  "This is the actual ASCII before-flag in effect in buffer A.
It is either `ediff-before-flag-mol' or `ediff-before-flag-bol' depending
on whether the selected difference region starts in the middle of a line 
or at the beginning of a line.")
(ediff-defvar-local ediff-after-flag-A nil
  "This is the actual ASCII after-flag in effect in buffer A.
It is either `ediff-before-flag-mol' or `ediff-before-flag-bol' depending
on whether the selected difference region starts in the middle of a line 
or at the beginning of a line.")
(ediff-defvar-local ediff-before-flag-B nil
  "This is the actual ASCII before-flag in effect in buffer B.
It is either `ediff-before-flag-mol' or `ediff-before-flag-bol' depending
on whether the selected difference region starts in the middle of a line 
or at the beginning of a line.")
(ediff-defvar-local ediff-after-flag-B nil
  "This is the actual ASCII after-flag in effect in buffer B.
It is either `ediff-before-flag-mol' or `ediff-before-flag-bol' depending
on whether the selected difference region starts in the middle of a line 
or at the beginning of a line.")

  
(ediff-defvar-local ediff-want-faces t
  "If t, differences are highlighted using faces on a window system.
If nil, they are highlighted using ASCII flags, ediff-before-flag
and ediff-after-flag.  On a non-window system, differences are always
highlighted using ASCII flags.

This variable can be set either in .emacs or toggled interactively, using
ediff-toggle-hilit.") 

(ediff-defvar-local ediff-want-default-menus t
  "If t, Ediff will set up menus in the menu bar.
This variable must be set before Ediff is loaded. If you don't like the
look of the default menus, set this variable to nil and make your own
menus.")  

(ediff-defvar-local ediff-auto-refine (if window-system 'on 'nix)
  "If `'on', Ediff auto-highlights fine diffs for the current diff region.
If `off', auto-highlighting is not used. If `'nix', no fine diffs are shown
at all, unless the user force-refines the region by hitting `*'.

This variable can be set either in .emacs or toggled interactively, using
ediff-toggle-hilit.") 

(ediff-defvar-local ediff-ignore-similar-regions nil
  "*If t, skip over difference regions that differ only in the white space and line breaks.")

(ediff-defvar-local ediff-auto-refine-limit 700
  "Auto-refine only those regions that are smaller than this number of bytes.")

(ediff-defvar-local ediff-highlight-all-diffs t
  "If nil, only the selected differences are highlighted.
This variable can be set either in .emacs or toggled interactively, using
ediff-toggle-hilit.") 

(ediff-defvar-local ediff-highlighting-style nil
  "A var local to each control panel buffer.
Indicates highlighting style in effect for this buffer: `face', `ascii',
nil -- temporarily unhighlighted, `off' -- turned off \(on a dumb
terminal only\).")

  

;; Variables that control each Ediff session.  They are local to the
;; control buffer. 

;; Mode variables
(ediff-defvar-local ediff-A-buffer nil
  "The buffer in which the A variant is stored.")
(ediff-defvar-local ediff-B-buffer nil
  "The buffer in which the B variant is stored.")
(ediff-defvar-local ediff-control-buffer nil
  "The control buffer of ediff. ")

;(ediff-defvar-local ediff-control-buffer-suffix nil
;  "The suffix of the control buffer name. ")
  
(ediff-defvar-local ediff-control-window nil
  "The control window.")
(ediff-defvar-local ediff-window-config-saved ""
  "Ediff's window configuration.
Used to minimize the need to rearrange windows.")


(ediff-defvar-local ediff-A-buffer-values nil
  "Keeps working values of ediff-saved-variables for ediff-A-buffer.")
(ediff-defvar-local ediff-B-buffer-values nil
  "Keeps working values of ediff-saved-variables for ediff-B-buffer.")

(ediff-defvar-local ediff-A-buffer-values-setup nil
  "Remembers ediff-saved-variables for ediff-A-buffer as they were at setup.")
(ediff-defvar-local ediff-B-buffer-values-setup nil
  "Remembers ediff-saved-variables for ediff-B-buffer as they were at setup.")

(ediff-defvar-local ediff-difference-vector nil
  "Vector of differences between the variants. 
Each difference is represented by a vector of two overlays.  The first
overlays the difference section in the A buffer and the second overlays the
diff in the B buffer. If a difference section is empty, the corresponding
overlay's endpoints coincide. ")

(ediff-defvar-local ediff-current-difference -1
  "The difference that is currently selected.")
(ediff-defvar-local ediff-number-of-differences nil
  "Number of differences found.")
  
(ediff-defvar-local ediff-diff-buffer nil
  "Buffer containing the output of diff, which is used by Ediff to step
through files.")
(ediff-defvar-local ediff-fine-diff-buffer nil
  "Buffer used for diff-style fine differences between regions.")
(ediff-defvar-local ediff-tmp-buffer nil
  "Temporary buffer used for computing fine differences.")
(ediff-defvar-local ediff-error-buffer nil
  "Buffer containing the output of diff when diff returns errors.")

(ediff-defvar-local ediff-this-buffer-control-sessions  nil
  "List of ediff control panels associated with each buffer A/B.")

(defvar ediff-disturbed-overlays nil
  "List of difference overlays disturbed by working with the current diff.")
  
(defvar ediff-shaded-overlay-priority  100
  "Priority of non-selected overlays.")


(if (ediff-if-lucid)
    (progn
      (fset 'ediff-overlayp (symbol-function 'extentp))
      (fset 'ediff-make-overlay (symbol-function 'make-extent))
      (fset 'ediff-delete-overlay (symbol-function 'delete-extent))
      ;;(fset 'ediff-overlay-put (symbol-function 'set-extent-property))
      ;;(fset 'ediff-move-overlay (symbol-function 'set-extent-endpoints))
      (fset 'ediff-overlay-buffer (symbol-function 'extent-buffer))
      (fset 'ediff-overlay-start (symbol-function 'extent-start-position))
      (fset 'ediff-overlay-end (symbol-function 'extent-end-position))
      (fset 'ediff-overlay-get (symbol-function 'extent-property)))
  (fset 'ediff-overlayp (symbol-function 'overlayp))
  (fset 'ediff-make-overlay (symbol-function 'make-overlay))
  (fset 'ediff-delete-overlay (symbol-function 'delete-overlay))
  ;;(fset 'ediff-overlay-put (symbol-function 'overlay-put))
  ;;(fset 'ediff-move-overlay (symbol-function 'move-overlay))
  (fset 'ediff-overlay-buffer (symbol-function 'overlay-buffer))
  (fset 'ediff-overlay-start (symbol-function 'overlay-start))
  (fset 'ediff-overlay-end (symbol-function 'overlay-end))
  (fset 'ediff-overlay-get (symbol-function 'overlay-get)))
  
(if window-system
    (if (ediff-if-lucid)
	(progn
	  (fset 'ediff-select-frame (symbol-function 'select-screen))
	  (fset 'ediff-window-frame (symbol-function 'window-screen))
	  (fset 'ediff-display-color-p (symbol-function 'x-color-display-p))
	  (fset 'ediff-valid-color-p (symbol-function 'x-valid-color-name-p))
	  (fset 'ediff-get-face (symbol-function 'get-face)))
      (fset 'ediff-window-frame (symbol-function 'window-frame))
      (fset 'ediff-select-frame (symbol-function 'select-frame))
      (fset 'ediff-display-color-p (symbol-function 'x-display-color-p))
      
      ;; This is a temporary fix for OS/2 users
      ;; pm-win.el in PM-Emacs should be fixed.
      (if (eq window-system 'pm)
	  (fset 'ediff-valid-color-p 
		(function (lambda (color) (assoc color pm-color-alist))))
	(fset 'ediff-valid-color-p (symbol-function 'x-color-defined-p))
	)
	
      (fset 'ediff-get-face (symbol-function 'internal-get-face)))
  ;; not a window system
  (fset 'ediff-window-frame (function (lambda (wind) (if wind 1 nil)) ))
  (fset 'ediff-select-frame (symbol-function 'identity))
  (fset 'ediff-make-current-diff-overlay (function (lambda (type) nil)))
  (fset 'ediff-unhighlight-diffs-totally (function (lambda () nil))))
  

(if (not window-system)
    ()
  (defun ediff-set-face (ground face color)
    "Sets face foreground/background."
    (if (ediff-valid-color-p color)
	(if (eq ground 'foreground)
	    (set-face-foreground face color)
	  (set-face-background face color))
      (cond ((memq face
		   '(ediff-current-diff-face-A ediff-current-diff-face-B))
	     (copy-face 'highlight face))
	    ((memq face
		   '(ediff-fine-diff-face-A ediff-fine-diff-face-B))
	     (copy-face 'secondary-selection face)
	     (set-face-underline-p face t))
	    ((memq face
		   '(ediff-odd-diff-face-A ediff-odd-diff-face-B
		     ediff-even-diff-face-A ediff-even-diff-face-B))
	     (copy-face 'secondary-selection face)))))
      
  (defvar ediff-current-diff-face-A
    (progn
      (make-face 'ediff-current-diff-face-A)
      (or (face-differs-from-default-p 'ediff-current-diff-face-A)
	  (cond ((ediff-display-color-p)
		 (ediff-set-face
		  'foreground 'ediff-current-diff-face-A "firebrick")
		 (ediff-set-face
		  'background 'ediff-current-diff-face-A "pale green"))
		(t
		 (if (ediff-if-lucid)
		     (copy-face 'modeline 'ediff-current-diff-face-A)
		   (copy-face 'highlight 'ediff-current-diff-face-A))
		 )))
      'ediff-current-diff-face-A)
      ;;(ediff-get-face 'ediff-current-diff-face-A))
    "Face for highlighting the selected difference in buffer A.")

  (defvar ediff-current-diff-face-B
    (progn
      (make-face 'ediff-current-diff-face-B)
      (or (face-differs-from-default-p 'ediff-current-diff-face-B)
	  (cond ((ediff-display-color-p)
		 (ediff-set-face
		  'foreground 'ediff-current-diff-face-B "DarkOrchid")
		 (ediff-set-face
		  'background 'ediff-current-diff-face-B "Yellow"))
		(t 
		 (if (ediff-if-lucid)
		     (copy-face 'modeline 'ediff-current-diff-face-B)
		   (copy-face 'highlight 'ediff-current-diff-face-B))
		 )))
      'ediff-current-diff-face-B)
      ;;(ediff-get-face 'ediff-current-diff-face-B))
    "Face for highlighting the selected difference in buffer B.")

  (defvar ediff-fine-diff-face-A
    (progn
      (make-face 'ediff-fine-diff-face-A)
      (or (face-differs-from-default-p 'ediff-fine-diff-face-A)
	  (cond ((ediff-display-color-p)
		 (ediff-set-face 'foreground 'ediff-fine-diff-face-A
				 "Navy")
		 (ediff-set-face 'background 'ediff-fine-diff-face-A
				 "sky blue"))
		(t (set-face-underline-p 'ediff-fine-diff-face-A t))))
      'ediff-fine-diff-face-A)
      ;;(ediff-get-face 'ediff-fine-diff-face-A))
    "Face for highlighting the refinement of the selected diff in buffer A.")

  (defvar ediff-fine-diff-face-B
    (progn
      (make-face 'ediff-fine-diff-face-B)
      (or (face-differs-from-default-p 'ediff-fine-diff-face-B)
	  (cond ((ediff-display-color-p)
		 (ediff-set-face 'foreground 'ediff-fine-diff-face-B "Black")
		 (ediff-set-face 'background 'ediff-fine-diff-face-B "cyan"))
		(t (set-face-underline-p 'ediff-fine-diff-face-B t))))
      'ediff-fine-diff-face-B)
      ;;(ediff-get-face 'ediff-fine-diff-face-B))
    "Face for highlighting the refinement of the selected diff in buffer B.")


  (defvar ediff-even-diff-face-A
    (progn
      (make-face 'ediff-even-diff-face-A)
      (or (face-differs-from-default-p 'ediff-even-diff-face-A)
	  (cond ((ediff-display-color-p)
		 (ediff-set-face
		  'foreground 'ediff-even-diff-face-A "black")
		 (ediff-set-face
		  'background 'ediff-even-diff-face-A "light grey"))
		(t 
		 (copy-face 'italic 'ediff-even-diff-face-A))))
      'ediff-even-diff-face-A)
      ;;(ediff-get-face 'ediff-even-diff-face-A))
    "Face used to highlight even-numbered differences in buffer A.")
      
  (defvar ediff-even-diff-face-B
    (progn
      (make-face 'ediff-even-diff-face-B)
      (or (face-differs-from-default-p 'ediff-even-diff-face-B)
	  (cond ((ediff-display-color-p)
		 (ediff-set-face
		  'foreground 'ediff-even-diff-face-B "White")
		 (ediff-set-face
		  'background 'ediff-even-diff-face-B "Gray"))
		(t 
		 (copy-face 'italic 'ediff-even-diff-face-B))))
      'ediff-even-diff-face-B)
      ;;(ediff-get-face 'ediff-even-diff-face-B))
    "Face used to highlight even-numbered differences in buffer B.")
  
  (defvar ediff-odd-diff-face-A
    (progn
      (make-face 'ediff-odd-diff-face-A)
      (or (face-differs-from-default-p 'ediff-odd-diff-face-A)
	  (cond ((ediff-display-color-p)
		 (ediff-set-face
		  'foreground 'ediff-odd-diff-face-A "White")
		 (ediff-set-face
		  'background 'ediff-odd-diff-face-A "Gray"))
		(t 
		 (copy-face 'italic 'ediff-odd-diff-face-A))))
      'ediff-odd-diff-face-A)
      ;;(ediff-get-face 'ediff-odd-diff-face-A))
    "Face used to highlight odd-numbered differences in buffer A.")
      
  (defvar ediff-odd-diff-face-B
    (progn
      (make-face 'ediff-odd-diff-face-B)
      (or (face-differs-from-default-p 'ediff-odd-diff-face-B)
	  (cond ((ediff-display-color-p)
		 (ediff-set-face
		  'foreground 'ediff-odd-diff-face-B "Black")
		 (ediff-set-face
		  'background 'ediff-odd-diff-face-B "light grey"))
		(t 
		 (copy-face 'italic 'ediff-odd-diff-face-B))))
      'ediff-odd-diff-face-B)
      ;;(ediff-get-face 'ediff-odd-diff-face-B))
    "Face used to highlight odd-numbered differences in buffer B.")

  ;; Create *-var faces. These are the actual faces used to highlight
  ;; odd-numbered difference regions.
  ;; They are used as follows: when highlighting is turned on,
  ;; ediff-odd/even-diff-face-A/B are copied
  ;; into ediff-odd/even-diff-face-A/B-var, and all odd/even overlays become
  ;; highlighted. When highlighting is turned off, then the face 'default is
  ;; copied into ediff-odd/even-diff-face-A/B-var, thereby unhighlighting all
  ;; difference regions.
  (make-face 'ediff-even-diff-face-A-var)
  (make-face 'ediff-even-diff-face-B-var)
  (make-face 'ediff-odd-diff-face-A-var)
  (make-face 'ediff-odd-diff-face-B-var)
  
  ;; initialize *-var faces
  (defun ediff-init-var-faces ()
    (copy-face (if (and ediff-want-faces ediff-highlight-all-diffs)
		   ediff-even-diff-face-A 'default)
	       'ediff-even-diff-face-A-var)
    (copy-face (if (and ediff-want-faces ediff-highlight-all-diffs)
		   ediff-even-diff-face-B 'default)
	       'ediff-even-diff-face-B-var)
    (copy-face (if (and ediff-want-faces ediff-highlight-all-diffs)
		   ediff-odd-diff-face-A 'default)
	       'ediff-odd-diff-face-A-var)
    (copy-face (if (and ediff-want-faces ediff-highlight-all-diffs)
		   ediff-odd-diff-face-B 'default)
	       'ediff-odd-diff-face-B-var))
      

  ;;; Overlays

  (ediff-defvar-local ediff-current-diff-overlay-A nil
    "Overlay specifying the current difference region in buffer A.")
  (ediff-defvar-local ediff-current-diff-overlay-B nil
    "Overlay specifying the current difference region in buffer B.")
  
  (defun ediff-make-current-diff-overlay (type)
      (let ((overlay (if (eq type 'A)
			 'ediff-current-diff-overlay-A
		       'ediff-current-diff-overlay-B))
	    (buffer (ediff-get-buffer type))
	    (face (if (eq type 'A) 
		      (face-name ediff-current-diff-face-A)
		    (face-name ediff-current-diff-face-B))))
	(set overlay (ediff-make-overlay (point-max) (point-max) buffer))
	(ediff-overlay-put (eval overlay) 'face face)
	(ediff-overlay-put (eval overlay) 'ediff ediff-control-buffer)
	))
	
  ;; Compute priority of ediff overlay.
  (defun ediff-highest-priority (start end buffer)
    (let ((pos (max 1 (1- start)))
	  ovr-list)
      (if (ediff-if-lucid)
	  (1+ ediff-shaded-overlay-priority)
	(ediff-eval-in-buffer
	 buffer
	 (while (< pos (min (point-max) (1+ end)))
	   (setq ovr-list (append (overlays-at pos) ovr-list))
	   (setq pos (next-overlay-change pos)))
	 (1+ (eval
	      (cons '+
		    (mapcar (function
			     (lambda (ovr)
			       (if ovr
				   (or (ediff-overlay-get ovr 'priority) 0)
				 0)))
			    ovr-list)
		    )))
	 ))))

)  ; end of window-system-only code.
  
    
;; Ediff toggle read-only stuff
(defvar ediff-toggle-read-only-function nil
  "*Specifies the function to be used to toggle read-only.
If nil, Ediff tries to deduce the function from the binding of C-x C-q.
Normally, this is the `toggle-read-only' function, but, if version
control is used, it could be `vc-toggle-read-only' or `rcs-toggle-read-only'.")

(ediff-defvar-local ediff-local-checkout-flag nil
  "If t, indicates that buffer has been already checked out.")
  


;;; Misc

(defvar ediff-split-window-function 'split-window-vertically
  "*The function to split the main window between buffer-A and buffer-B.
You can set it to be split horizontally instead of the
default vertical split by setting this variable to
'split-window-horizontally.  You can also have your own function for fancy
splits.  This variable has no effect when buffer-A and buffer-B are shown in
different frames.  In this case, Ediff will use those frames to display
these buffers.")

		 
(defconst ediff-saved-variables
  '(;;buffer-read-only
    buffer-auto-save-file-name)
  "Buffer-local variables saved and restored during an Ediff session.")

;;(defconst ediff-working-values '(nil nil)
(defconst ediff-working-values '(nil)
  "Values to be assigned to `ediff-saved-variables' during diff.")
  
(defvar ediff-use-last-dir nil
  "*If t, Ediff uses previous directory as default when reading file name.")
  
(defvar ediff-no-help-in-control-buffer nil
  "*Non-nil means C-h should not invoke Emacs help in control buffer.
Instead, C-h jumps to previous difference.")

(defvar ediff-version-control-package 'vc
  "Version control package used.
Currently, Ediff supports vc.el and rcs.el.")
  
(defvar ediff-temp-file-prefix
  (let ((env (or (getenv "TMPDIR")
		 (getenv "TMP")
		 (getenv "TEMP")))
	d)
    (setq d (if (and env (> (length env) 0))
		env
	      "/tmp"))
    (if (= (aref d (1- (length d))) ?/)
	(setq d (substring d 0 -1)))
    (concat d "/ediff"))
  "*Prefix to put on Ediff temporary file names.
Do not start with `~/' or `~user-name/'.")  

(defvar ediff-temp-file-mode 384	; u=rw only
  "*Mode for Ediff temporary files.")
  
(ediff-defvar-local ediff-temp-file-A nil
  "Temporary file used for refining difference regions in buffer B.")
(ediff-defvar-local ediff-temp-file-B nil
  "Temporary file used for refining difference regions in buffer B.")
  
(defvar ediff-last-dir-A nil
  "Last directory used by an Ediff command for file-A.")
(defvar ediff-last-dir-B nil
  "Last directory used by an Ediff command for file-B.")
(defvar ediff-last-dir-patch nil
  "Last directory used by an Ediff command for file to patch.")
  
;; Build keymaps

(defvar ediff-mode-map nil
  "Local keymap used in Ediff mode.")
  
(defun ediff-frame-has-menubar ()
  (if (ediff-if-lucid)
      current-menubar
    (< 0 (cdr (assq 'menu-bar-lines (frame-parameters (selected-frame)))))
    ))

;;; This is split in three parts to avoid
;;; making a line in loaddefs.el that is too long for patch.
;;; Note that autoload.el currently looks for cookies
;;; only at top level in the file.
;;; So I moved these to top level.  But the conditionals on
;;; purify-flag make these no-ops when you load ediff.
;;; They only do something in loaddefs.el.
;;;###autoload
(if purify-flag
  (progn
    (defvar menu-bar-epatch-menu (make-sparse-keymap "Epatch"))
    (fset 'menu-bar-epatch-menu (symbol-value 'menu-bar-epatch-menu))
    (defvar menu-bar-ediff-menu (make-sparse-keymap "Ediff"))
    (fset 'menu-bar-ediff-menu (symbol-value 'menu-bar-ediff-menu))))


;;;###autoload
(if purify-flag
    (progn
      (define-key menu-bar-ediff-menu [ediff-revision]
	'("File with a version ..." . ediff-revision))
      (define-key menu-bar-ediff-menu [ediff-buffers]
	'("Buffers ..." . ediff-buffers))
      (define-key menu-bar-ediff-menu [ediff-files]
	'("Files ..." . ediff-files))))

;;;###autoload
(if purify-flag
    (progn
      (define-key menu-bar-epatch-menu [ediff-patch-buffer]
	'("To a Buffer ..." . ediff-patch-buffer))
      (define-key menu-bar-epatch-menu [ediff-patch-file]
	'("To a File ..." . ediff-patch-file))))
	

(if (and window-system ediff-want-default-menus (ediff-frame-has-menubar))
    (cond ((ediff-if-lucid)
	   (defvar ediff-menu
	     '(""
	      ["Files ..."  ediff-files t]
	      ["Buffers ..." ediff-buffers t]
	      ["File with a version ..."  ediff-revision t]))
	   (defvar epatch-menu
	     '(""
	       ["To a file ..."  ediff-patch-file t]
	       ["To a buffer ..." ediff-patch-buffer t]))
	   (add-menu '("File") "Compare" 
		     ediff-menu
		     "New Screen")
	   (add-menu '("File") "Apply Patch" 
		     epatch-menu
		     "New Screen")
	   ;; Display a solid horizontal line 
	   (add-menu-item '("File") "---" nil nil "New Screen"))
	  (t  ;; FSF Emacs
	   (define-key menu-bar-file-menu [epatch]
	     '("Apply Patch" . menu-bar-epatch-menu))
	   (define-key menu-bar-file-menu [ediff]
	     '("Compare" . menu-bar-ediff-menu)))))



(defun ediff-setup-keymap ()
  "Set up the keymap used in the control buffer of Ediff."
  (setq ediff-mode-map (make-sparse-keymap))
  (suppress-keymap ediff-mode-map)
  
  (define-key ediff-mode-map "p" 'ediff-previous-difference)
  (define-key ediff-mode-map "\C-?" 'ediff-previous-difference)
  (define-key ediff-mode-map "\C-h" (if ediff-no-help-in-control-buffer
					'ediff-previous-difference nil))
  (define-key ediff-mode-map "n" 'ediff-next-difference)
  (define-key ediff-mode-map " " 'ediff-next-difference)
  (define-key ediff-mode-map "j" 'ediff-jump-to-difference)
  (define-key ediff-mode-map "g"  nil)
  (define-key ediff-mode-map "ga" 'ediff-jump-to-difference-at-point)
  (define-key ediff-mode-map "gb" 'ediff-jump-to-difference-at-point)
  (define-key ediff-mode-map "q" 'ediff-quit)
  (define-key ediff-mode-map "z" 'ediff-suspend)
  (define-key ediff-mode-map "c" 'ediff-recenter)
  (define-key ediff-mode-map "s" 'ediff-toggle-split)
  (define-key ediff-mode-map "h" 'ediff-toggle-hilit)
  (define-key ediff-mode-map "@" 'ediff-toggle-autorefine)
  (define-key ediff-mode-map "v" 'ediff-scroll-up)
  (define-key ediff-mode-map "\C-v" 'ediff-scroll-up)
  (define-key ediff-mode-map "^" 'ediff-scroll-down)
  (define-key ediff-mode-map "\M-v" 'ediff-scroll-down)
  (define-key ediff-mode-map "V" 'ediff-scroll-down)
  (define-key ediff-mode-map "<" 'ediff-scroll-left)
  (define-key ediff-mode-map ">" 'ediff-scroll-right)
  (define-key ediff-mode-map "i" 'ediff-status-info)
  (define-key ediff-mode-map "?" 'ediff-toggle-help)
  (define-key ediff-mode-map "!" 'ediff-recompute-diffs)
  (define-key ediff-mode-map "*" 'ediff-make-fine-diffs)
  (define-key ediff-mode-map "a"  nil)
  (define-key ediff-mode-map "ab" 'ediff-diff-to-diff)
  (define-key ediff-mode-map "b"  nil)
  (define-key ediff-mode-map "ba" 'ediff-diff-to-diff)
  (define-key ediff-mode-map "bug" 'ediff-submit-report)
  (define-key ediff-mode-map "r"  nil)
  (define-key ediff-mode-map "ra" 'ediff-restore-diff)
  (define-key ediff-mode-map "rb" 'ediff-restore-diff)
  (define-key ediff-mode-map "#"  nil)
  (define-key ediff-mode-map "#h"  'ediff-toggle-regexp-match)
  (define-key ediff-mode-map "#f"  'ediff-toggle-regexp-match)
  (define-key ediff-mode-map "##"  'ediff-toggle-skip-similar)
  (define-key ediff-mode-map "o"   nil)
  (define-key ediff-mode-map "A"  'ediff-toggle-read-only)
  (define-key ediff-mode-map "B"  'ediff-toggle-read-only)
  (define-key ediff-mode-map "w"   nil)
  (define-key ediff-mode-map "wa"  'ediff-save-buffer)
  (define-key ediff-mode-map "wb"  'ediff-save-buffer)
  (define-key ediff-mode-map "wf"  'ediff-save-buffer)
  (define-key ediff-mode-map "k"   nil)
  (define-key ediff-mode-map "kkk" 'ediff-reload-keymap) ;; for debugging
  ;; Allow ediff-mode-map to be referenced indirectly
  (fset 'ediff-mode-map ediff-mode-map))


;;; Setup functions

(defun ediff-find-file (file-var buffer &optional last-dir hooks-var)
  "Visit FILE and arrange its buffer to Ediff's liking. 
FILE is actually a variables symbol that must contain a true file name.
BUFFER is a variable symbol, which will get the buffer object into which
FILE is read.  LAST-DIR is the directory variable symbol where FILE's
directory name should be returned. HOOKS is a variable symbol that will be
assigned the hook to be executed after `ediff-strartup' is finished.
`ediff-find-file' arranges that the temp files it might create will be
deleted. 
Arguments: (file buffer &optional last-dir hooks)"
  (let* ((file (eval file-var))
	 (file-magic (ediff-find-file-name-handler file)))
    (if (not (file-readable-p file))
	(error "File `%s' does not exist or is not readable" file))
  
    ;; Record the directory of the file
    (if last-dir
	(set last-dir (expand-file-name (file-name-directory file))))
    
    ;; Setup the buffer
    (set buffer (find-file-noselect file))
  
    (ediff-eval-in-buffer 
     (eval buffer)
     (widen)  ;; Make sure the entire file is seen
     (cond (file-magic  ;; file has handler, such as jka-compr-handler or
	            	;; ange-ftp-hook-function--arrange for temp file
	    (ediff-verify-file-buffer 'magic)
	    (setq file (ediff-make-temp-file))
	    (set hooks-var (cons (` (lambda () (delete-file (, file))))
				 (eval hooks-var))))
	   ;; file processed via auto-mode-alist, a la uncompress.el
	   ((not (equal (file-truename file)
			(file-truename (buffer-file-name))))
	    (setq file (ediff-make-temp-file))
	    (set hooks-var (cons (` (lambda () (delete-file (, file))))
				 (eval hooks-var))))
	   (t ;; plain file---just check that the file matches the buffer
	     (ediff-verify-file-buffer))))
    (set file-var file)))

(defun ediff-files-internal (file-A file-B &optional startup-hooks)
  (let (buffer-A buffer-B)
    (message "Reading file %s ... " file-A)(sit-for 0)
    (ediff-find-file 'file-A 'buffer-A 'ediff-last-dir-A 'startup-hooks)
    (message "Reading file %s ... " file-B)(sit-for 0)
    (ediff-find-file 'file-B 'buffer-B 'ediff-last-dir-B 'startup-hooks)
    (ediff-setup buffer-A file-A buffer-B file-B startup-hooks)))
  
(defun ediff-get-patch-buffer (dir)
  "Obtain patch buffer.  If patch is already in a buffer---use it.
Else, read patch file into a new buffer."
  (if (y-or-n-p "Is the patch file already in a buffer? ")
      (setq ediff-patch-buf
	    (get-buffer (read-buffer "Patch buffer name: " nil t))) ;must match
    (setq ediff-patch-buf
	  (find-file-noselect (read-file-name "Patch file name: " dir))))
  
  ;; secure the patch buffer against accidental changes
  (ediff-eval-in-buffer
   ediff-patch-buf
   (setq buffer-read-only t))
   
  (setq ediff-patch-diagnostics
	(get-buffer-create "*ediff patch diagnostics*"))
  (ediff-eval-in-buffer
   ediff-patch-diagnostics
   (insert-buffer ediff-patch-buf))
  )

;; Start up Ediff on two files
(defun ediff-setup (buffer-A file-A buffer-B file-B startup-hooks)
  (setq file-A (expand-file-name file-A))
  (setq file-B (expand-file-name file-B))
  (let* ((control-buffer-name 
	  (emerge-unique-buffer-name "Ediff Control Panel" ""))
	 (control-buffer (ediff-eval-in-buffer
			  buffer-A
			  (get-buffer-create control-buffer-name))))
    (ediff-eval-in-buffer
     control-buffer
     (ediff-mode) ;; in control buffer only
     (setq buffer-read-only nil) ;; in control buffer only
     (setq ediff-A-buffer buffer-A)
     (setq ediff-B-buffer buffer-B)
     (setq ediff-control-buffer control-buffer)
;    (setq ediff-control-buffer-suffix
;	   (if (string-match "<[0-9]*>" control-buffer-name)
;	       (substring control-buffer-name
;			  (match-beginning 0) (match-end 0))
;	     "<1>"))
     (setq ediff-error-buffer (get-buffer-create (emerge-unique-buffer-name
						  "*ediff-errors" "*")))
     (ediff-remember-buffer-characteristics t) ;; remember at setup
     
     (ediff-set-keys)
     (setq ediff-difference-vector (ediff-setup-diff-regions file-A file-B))
     (setq ediff-number-of-differences (length ediff-difference-vector))
     (setq ediff-current-difference -1)
     (ediff-make-current-diff-overlay 'A)
     (ediff-make-current-diff-overlay 'B)
     (if window-system
	 (ediff-init-var-faces))
     (run-hooks 'ediff-before-setup-windows-hooks)
     (ediff-setup-windows buffer-A buffer-B control-buffer t)
         
     ;; all these must be inside ediff-eval-in-buffer control-buffer,
     ;; since these vars are local to control-buffer
     ;; These won't run if there are errors in diff
     (ediff-eval-in-buffer
      ediff-A-buffer
      (add-hook 'local-write-file-hooks 'ediff-block-write-file)
      (setq before-change-function 'ediff-before-change-guard)
      ;; add control-buffer to the list of sessions
      (or (memq control-buffer ediff-this-buffer-control-sessions)
	  (setq ediff-this-buffer-control-sessions
		(cons control-buffer ediff-this-buffer-control-sessions)))
      (setq mode-line-buffer-identification
	    (cons "A: "
		  (if (string-match "\\(^ \\|^[^ \t]*: \\)"
				    (car mode-line-buffer-identification))
		      (cons (substring (car mode-line-buffer-identification)
				       (match-end 0))
			    (cdr mode-line-buffer-identification))
		    mode-line-buffer-identification)))
      (run-hooks 'ediff-prepare-buffer-hooks))
     (ediff-eval-in-buffer
      ediff-B-buffer
      (add-hook 'local-write-file-hooks 'ediff-block-write-file)
      (setq before-change-function 'ediff-before-change-guard)
      ;; add control-buffer to the list of sessions
      (or (memq control-buffer ediff-this-buffer-control-sessions)
	  (setq ediff-this-buffer-control-sessions
		(cons control-buffer ediff-this-buffer-control-sessions)))
      (setq mode-line-buffer-identification
	    (cons "B: "
		  (if (string-match "\\(^ \\|^[^ \t]*: \\)"
				    (car mode-line-buffer-identification))
		      (cons (substring (car mode-line-buffer-identification)
				       (match-end 0))
			    (cdr mode-line-buffer-identification))
		    mode-line-buffer-identification)))
      (run-hooks 'ediff-prepare-buffer-hooks))

     (ediff-eval-in-buffer control-buffer
			    (run-hooks 'startup-hooks 'ediff-startup-hooks)
			    (setq buffer-read-only t)))))

;; Generate the difference vector and overlays for the two files
;; With optional arg `refine', create refining difference regions
(defun ediff-setup-diff-regions (file-A file-B 
					&optional use-old refine-region
					          diff-program diff-options
						  diff-ok-lines-regexp)
						  
  (setq diff-program (or diff-program ediff-diff-program)
	diff-options (or diff-options ediff-diff-options)
	diff-ok-lines-regexp
	             (or diff-ok-lines-regexp ediff-diff-ok-lines-regexp))
		     
  (or use-old (setq ediff-diff-buffer 
		    (get-buffer-create
		     (emerge-unique-buffer-name "*ediff-diff" "*"))
		    ediff-fine-diff-buffer
		    (get-buffer-create
		     (emerge-unique-buffer-name "*ediff-fine-diff" "*"))
		    ))
  (ediff-eval-in-buffer
   (if refine-region ediff-fine-diff-buffer ediff-diff-buffer)
   (erase-buffer)
   ;; shell-command tends to display old shell command buffers even when it
   ;; puts output in another buffer---probably an Emacs bug.
   (ediff-kill-buffer-carefully "*Shell Command Output*")
   (let ((shell-file-name ediff-shell))
     (if refine-region
	 (message "Refining difference region %d ..." (1+ refine-region))
       (message "Computing differences ...")(sit-for 0))
     (shell-command
      (format "%s %s %s %s"
	      diff-program diff-options
	      (ediff-protect-metachars file-A)
	      (ediff-protect-metachars file-B))
      t)
     ))
  
   
  (if refine-region
      (progn
	(ediff-prepare-error-list diff-ok-lines-regexp ediff-fine-diff-buffer)
	(message "Refining difference region %d ... Done." (1+ refine-region))
	(ediff-convert-diffs-to-overlays-refine
	 ediff-A-buffer ediff-B-buffer
	 (ediff-extract-diffs ediff-fine-diff-buffer)
	 refine-region))
    (ediff-prepare-error-list diff-ok-lines-regexp ediff-diff-buffer)
    (message "Computing differences ... Done.")(sit-for 0)
    (ediff-convert-diffs-to-overlays
     ediff-A-buffer ediff-B-buffer
     (ediff-extract-diffs ediff-diff-buffer
			  ediff-A-buffer ediff-B-buffer))))
  
    
(defun ediff-prepare-error-list (ok-regexp diff-buff)
    (ediff-eval-in-buffer
     ediff-error-buffer
     (erase-buffer)
     (insert-buffer diff-buff)
     (delete-matching-lines ok-regexp)))

;;; Function to start Ediff by patching a file

;;;###autoload
(defun ediff-patch-file (source-filename &optional startup-hooks)
  "Run Ediff by patching FILE-TP-PATCH."
  (interactive 
   (list (ediff-read-file-name "File to patch"
			       (if ediff-use-last-dir
				   ediff-last-dir-patch
				 default-directory)
			       nil)))
  
  (ediff-get-patch-buffer (file-name-directory source-filename))
  (let* ((backup-extension 
	  ;; if the user specified a -b option, extract the backup
	  ;; extension from there; else use `.orig'
	  (substring ediff-patch-options
		     (if (string-match "-b[ \t]+" ediff-patch-options)
			 (match-end 0) 0)
		     (if (string-match "-b[ \t]+[^ \t]+" ediff-patch-options)
			 (match-end 0) 0)))
	 (backup-extension (if (string= backup-extension "")
			       "orig" backup-extension))
	 (shell-file-name ediff-shell)
	 ;; ediff-find-file may use a temp file to do the patch
	 ;; so, we save source-filename and true-source-filename as a var
	 ;; that initially is source-filename but may be changed to a temp
	 ;; file for the purpose of patching.
	 (true-source-filename source-filename)
	 (target-filename source-filename)
	 target-buf buf-to-patch file-name-magic-p)
					
    ;; Make a temp file, if source-filename has a magic file handler (or if
    ;; it is handled via auto-mode-alist and similar magic).
    ;; Check if there is a buffer visiting source-filename and if they are in
    ;; synch; arrange for the deletion of temp file.
    (ediff-find-file 'true-source-filename 'buf-to-patch
		     'ediff-last-dir-patch 'startup-hooks)

    ;; Check if source file name has triggered black magic, such as file name
    ;; handlers or auto mode alist, and make a note of it.
    (setq file-name-magic-p (not (equal (file-truename true-source-filename)
					(file-truename source-filename))))
    
    ;; Checkout orig file, if necessary so that the patched file could be
    ;; checked back in.
    (ediff-toggle-read-only buf-to-patch)
    
    (ediff-eval-in-buffer
     ediff-patch-diagnostics
     (message "Applying patch ... ")(sit-for 0)
     ;; always pass patch the -f option, so it won't ask any questions
     (shell-command-on-region 
      (point-min) (point-max)
      (format "%s -f %s %s"
	      ediff-patch-program ediff-patch-options
	      (expand-file-name true-source-filename))
      t))
    (message "Applying patch ... Done.")(sit-for 0)
    (switch-to-buffer ediff-patch-diagnostics)
    (sit-for 0) ;; synchronize
    
    (or (file-exists-p (concat true-source-filename "." backup-extension))
	(error "Patch failed or didn't modify the original file."))
  
    ;; If black magic is involved, apply patch to a temp copy of the
    ;; file. Otherwise, apply patch to the orig copy.
    ;; If patch is applied to temp copy, we name the result
    ;; ***.patched. The orig file name isn't changed, and the temp copy of
    ;; the original is later deleted.
    ;; Without magic, the original file is renamed (usually into
    ;; old-name.orig) and the result of patching will have the 
    ;; same name as the original.
    (if (not file-name-magic-p)
	(ediff-eval-in-buffer
	 buf-to-patch
	 (set-visited-file-name (concat source-filename "." backup-extension))
	 (set-buffer-modified-p nil))
      (setq target-filename (concat true-source-filename ".patched"))
      (rename-file true-source-filename target-filename t)
      
      ;; arrange that the temp copy of orig will be deleted
      (rename-file (concat true-source-filename "." backup-extension)
		   true-source-filename t))
    
    ;; make orig buffer read-only
    (setq startup-hooks
	  (cons 'ediff-toggle-read-only-patch-orig startup-hooks))
    
    ;; set up a buf for the patched file
    (ediff-eval-in-buffer
     (setq target-buf (find-file-noselect target-filename))
     ;; files to be patched are always checked out first
     (setq ediff-local-checkout-flag t))
    
    (ediff-buffers buf-to-patch target-buf startup-hooks)
  
    (bury-buffer ediff-patch-diagnostics)
    (message "Patch diagnostics available in buffer %s."
	     (buffer-name ediff-patch-diagnostics))))

(defalias 'epatch 'ediff-patch-file)
(defalias 'epatch-buffer 'ediff-patch-buffer)

;;; Function to start Ediff on files

;;;###autoload
(defun ediff-files (file-A file-B &optional startup-hooks)
  "Run Ediff on a pair files, FILE-A and FILE-B."
  (interactive
   (let (f)
     (list (setq f (ediff-read-file-name "File A to compare" 
					 (if ediff-use-last-dir
					     ediff-last-dir-A
					   default-directory)
					 nil))
	   (ediff-read-file-name "File B to compare" 
				 (if ediff-use-last-dir
				     ediff-last-dir-B  nil)
				 f)
	   )))
  (ediff-files-internal file-A 
			(if (file-directory-p file-B)
			    (expand-file-name
			     (file-name-nondirectory file-A) file-B)
			  file-B)
			startup-hooks))


(defalias 'ediff 'ediff-files)


;;; Function to start Ediff on buffers

;;;###autoload
(defun ediff-buffers (buffer-A buffer-B &optional startup-hooks)
  "Run Ediff on a pair of buffers, BUFFER-A and BUFFER-B."
  (interactive 
   (list (read-buffer "Buffer A to compare: " (current-buffer) t)
	 (read-buffer "Buffer B to compare: "
		      (progn
			;; realign buffers so that two visible bufs will be
			;; at the top
			(save-window-excursion (other-window 1))
			(other-buffer (current-buffer) t))
		      t)))
  (if (not (ediff-buffer-live-p buffer-A))
      (error "Buffer %S doesn't exist." buffer-A))
  (if (not (ediff-buffer-live-p buffer-B))
      (error "Buffer %S doesn't exist." buffer-B))
      
  (let (file-A file-B)
    (ediff-eval-in-buffer
     buffer-A
     (setq file-A (ediff-make-temp-file)))
    (ediff-eval-in-buffer
     buffer-B
     (setq file-B (ediff-make-temp-file)))
    (ediff-setup (get-buffer buffer-A) file-A
		 (get-buffer buffer-B) file-B
		 (cons (` (lambda ()
			    (delete-file (, file-A))
			    (delete-file (, file-B))))
		       startup-hooks)
		 )))
		  
;;;###autoload
(defun ediff-patch-buffer (buffer-name &optional startup-hooks)		  
  "Run Ediff by patching BUFFER-NAME."
  (interactive "bBuffer to patch: ")
  
  (let* ((file-buffer (get-buffer buffer-name))
	 (file-name (if file-buffer (buffer-file-name  file-buffer))))
    (if (not file-name)
	(error "Buffer %s doesn't exist or doesn't visit any file.  Why patch?"
	       file-name))
    
    (ediff-patch-file file-name startup-hooks)))
      

;;; Versions Control functions      
      
;;;###autoload
(defun ediff-revision (revision)
  "Call `vc.el' or `rcs.el' depending on `ediff-version-control-package'.
This function is introduced to provide a uniform interface to version
control packages from Ediff."
  (interactive "sVersion to Ediff with (default is the latest version): ")
  (funcall
   (intern (format "%S-ediff-internal" ediff-version-control-package))
   revision))
      
(defun vc-ediff-internal (rev)
;; Note: this function will work only with Emacs 19.22 and higher.
  "Run Ediff on version REV of the current buffer in another window.
If the current buffer is named `F', the version is named `F.~REV~'.
If `F.~REV~' already exists, it is used instead of being re-created."
  (or (featurep 'vc)
      (if (locate-library "vc") ;; if vc.el is available
	  (require 'vc-hooks) 
	(error "The vc.el package is apparently not installed")))
  (define-key vc-prefix-map "=" 'ediff-revision)
  (let ((newvers (current-buffer)))
    (vc-version-other-window rev)
    ;; current-buffer is supposed to contain the old version
    ;; in another window
    (ediff-buffers newvers (current-buffer)) 
    ))
    
(defun rcs-ediff-view-revision (&optional rev)
  "View previous RCS revision of current file.
With prefix argument, prompts for a revision name." 
  (interactive (list (if current-prefix-arg 
			 (read-string "Revision: "))))
  (let* ((filename (buffer-file-name (current-buffer)))
	 (switches (append '("-p")
			   (if rev (list (concat "-r" rev)) nil)))
	 (buff (concat (file-name-nondirectory filename) ".~" rev "~")))
    (message "Working...")
    (setq filename (expand-file-name filename))
    (with-output-to-temp-buffer buff
      (let ((output-buffer (ediff-rcs-get-output-buffer filename buff)))
	(delete-windows-on output-buffer)
	(save-excursion
	  (set-buffer output-buffer)
	  (apply 'call-process "co" nil t nil
		 ;; -q: quiet (no diagnostics)
		 (append switches rcs-default-co-switches
			 (list "-q" filename))))) 
      (message "")
      buff)))    
      
(defun ediff-rcs-get-output-buffer (file name)
  ;; Get a buffer for RCS output for FILE, make it writable and clean it up.
  ;; Optional NAME is name to use instead of `*RCS-output*'.
  ;; This is a modified version from rcs.el v1.1. I use it here to make
  ;; Ediff immune to changes in rcs.el
  (let* ((default-major-mode 'fundamental-mode);; no frills!
	 (buf (get-buffer-create name)))
    (save-excursion
      (set-buffer buf)
      (setq buffer-read-only nil
	    default-directory (file-name-directory (expand-file-name file)))
      (erase-buffer))
    buf))

(defun rcs-ediff-internal (rev)
  "Run Ediff on the current buffer, comparing it with previous RCS revision."
  (or (featurep 'rcs)
      (if (locate-library "rcs")      
	  (require 'rcs)
	(error "The rcs.el package is apparently not installed")))
  (global-set-key "\C-cD" 'ediff-revision)
  (let ((newvers (current-buffer))
	(oldvers (rcs-ediff-view-revision rev)))
    (ediff-buffers newvers oldvers)
    ))




;; Select the lowest window on the frame.
(defun ediff-select-lowest-window ()
  (let* ((lowest-window (selected-window))
	 (bottom-edge (car (cdr (cdr (cdr (window-edges))))))
         (last-window (previous-window))
         (window-search t))
    (while window-search
      (let* ((this-window (next-window))
             (next-bottom-edge (car (cdr (cdr (cdr 
                                               (window-edges this-window)))))))
        (if (< bottom-edge next-bottom-edge)
            (progn
              (setq bottom-edge next-bottom-edge)
              (setq lowest-window this-window)))

        (select-window this-window)
        (if (eq last-window this-window)
            (progn
              (select-window lowest-window)
              (setq window-search nil)))))))

;;; Common setup routines

;; Set up the window configuration.  If POS is given, set the points to
;; the beginnings of the buffers.
(defun ediff-setup-windows (buffer-A buffer-B control-buffer &optional pos)
  ;; Make sure we are not in the minibuffer window when we try to delete
  ;; all other windows.
  (if (eq (selected-window) (minibuffer-window))
      (other-window 1))
  (or (ediff-leave-window-config control-buffer)
      (progn
	(delete-other-windows)
	(switch-to-buffer control-buffer)
	(ediff-refresh-mode-line)
  
	(ediff-arrange-buffer buffer-A buffer-B (current-buffer) pos)
	(ediff-arrange-buffer buffer-B buffer-A (current-buffer) pos)
	;; ediff-arrange-buffer always leaves in ctl buffer
	;; setup ctl wind if it is not set.
	(ediff-setup-control-window)
  
	;; If diff reports errors, show them then quit.
	(if (/= 0 (ediff-eval-in-buffer ediff-error-buffer (buffer-size)))
	    (let ((diff-output-buf  ediff-diff-buffer))
	      (switch-to-buffer ediff-error-buffer)
	      (ediff-kill-buffer-carefully control-buffer)
	      (error "Errors found in diff output.  Diff output buffer is %s"
		     diff-output-buf))))))


;; Arranges goal-buf on the screen.
(defun ediff-arrange-buffer (goal-buf other-buf ctl-buf &optional pos)
  (let* ((ctl-wind (ediff-get-visible-buffer-window ctl-buf)) 
	 (goal-wind (ediff-get-visible-buffer-window goal-buf))
	 (other-wind (ediff-get-visible-buffer-window other-buf))
	 (ctl-frame (ediff-window-frame ctl-wind))
	 (goal-frame (if goal-wind (ediff-window-frame goal-wind)))
	 (other-frame (if other-wind (ediff-window-frame other-wind)))
	 (ctl-frame-shared (or (eq ctl-frame goal-frame)
			       (eq ctl-frame other-frame))))
			  
    (cond ((and goal-frame
		(not (eq goal-wind other-wind)))
	    	    ;; goal buffer is visible and we are not comparing file
		    ;; against itself (by mistake).
		    ;; Note:  goal-frame != ctl-frame, as we deleted other
		    ;; windows  on ctl-frame.
	    	      (ediff-select-frame goal-frame)
		      (select-window goal-wind)
		      (delete-other-windows)) 
	    	    	    	    	      
	  ;; goal-buf invisible, ctl-frame has only ctl-buf
	  ;; then put goal-buf on ctl-frame
	  ((null ctl-frame-shared)
		      (ediff-select-frame ctl-frame)
		      (split-window-vertically)
		      (ediff-select-lowest-window)
		      (setq ctl-wind (selected-window))
		      (switch-to-buffer ctl-buf)
		      (ediff-setup-control-window)
		      (other-window 1)
		      (switch-to-buffer goal-buf)) ; goal-buf set
	  ;; goal-buf invisible, ctl-frame has ctl-buf and other-buf
	  ;; So, put everything in one frame
	  (other-frame   ;; share with the other buf
	    	       (ediff-select-frame ctl-frame)
		       (select-window other-wind)
		       (funcall ediff-split-window-function)
		       (other-window 1)
		       (switch-to-buffer goal-buf))
	  (t ;; debug
	   (error "Funny window combination (Ediff bug?)")))

      (if pos
	  (goto-char (point-min)))
	  
      (ediff-select-frame ctl-frame)
      (select-window ctl-wind)
      (switch-to-buffer ctl-buf)))
      
;; This function assumes that we are in the window where control buffer is
;; to reside.
(defun ediff-setup-control-window ()
  "Set up window for control buffer."
  (let ((window-min-height 2))
    (erase-buffer)
    (insert ediff-help-message)
    (shrink-window-if-larger-than-buffer)
    (setq ediff-control-window (selected-window))
    (setq ediff-window-config-saved
	  (format "%S%S%S%S"
		  ediff-control-window
		  (ediff-get-visible-buffer-window ediff-A-buffer)
		  (ediff-get-visible-buffer-window ediff-B-buffer)
		  ediff-split-window-function))
    (goto-char (point-min))
    (skip-chars-forward ediff-whitespace)))
  
(defun ediff-leave-window-config (control-buf)
  (and (eq control-buf (current-buffer))
       (/= (buffer-size) 0)
       (ediff-eval-in-buffer
	control-buf
	(string= ediff-window-config-saved
		 (format "%S%S%S%S"
			 (ediff-get-visible-buffer-window ediff-control-buffer)
			 (ediff-get-visible-buffer-window ediff-A-buffer)
			 (ediff-get-visible-buffer-window ediff-B-buffer)
			 ediff-split-window-function)))))
      

;; Set up the keymap in the control buffer
(defun ediff-set-keys ()
  "Set up Ediff keymap, if necessary."
  (if (null ediff-mode-map)
      (ediff-setup-keymap))
  (use-local-map ediff-mode-map))
  
;; Reload Ediff keymap.  For debugging only.
(defun ediff-reload-keymap ()
  (interactive)
  (setq ediff-mode-map nil)
  (ediff-set-keys))

(defun ediff-before-change-guard (start end)
  "If buffer is highlighted with ASCII flags, remove highlighting.
Arguments, START and END are not used, but are provided
because this is required by `before-change-function'."
  (let (rehighlight-key)
    (save-window-excursion
      (mapcar
       (function
	(lambda (buf)
	  (ediff-eval-in-buffer
	   buf
	   (if (eq ediff-highlighting-style 'ascii)
	       (progn
		 (ediff-unselect-and-select-difference
		  ediff-current-difference 
		  'unselect-only 'no-recenter)
		 (setq rehighlight-key
		       (substitute-command-keys "\\[ediff-recenter]"))
		 )))))
       ediff-this-buffer-control-sessions)
      (if rehighlight-key
	  (error 
	   "ASCII flags removed. You can edit now. Hit %S to rehighlight."
	   rehighlight-key))
     )))
     
(defun ediff-recompute-diffs ()
  "Recompute difference regions in buffers A and B."
  (interactive)
  (let ((point-A (ediff-eval-in-buffer ediff-A-buffer (point)))
	(point-B (ediff-eval-in-buffer ediff-B-buffer (point)))
	file-A file-B)
    (ediff-unselect-and-select-difference -1)
    (ediff-eval-in-buffer
     ediff-A-buffer
     (setq file-A (ediff-make-temp-file)))
    (ediff-eval-in-buffer
     ediff-B-buffer
     (setq file-B (ediff-make-temp-file)))
    (ediff-clear-diff-vector ediff-difference-vector 'fine-diffs-also)
    (setq ediff-killed-diffs-alist nil) ; saved kills will no longer be valid
    	    	    	    	    	; after recompute
    (setq ediff-difference-vector
	  (ediff-setup-diff-regions file-A file-B 'use-old))
    (setq ediff-number-of-differences (length ediff-difference-vector))
    (delete-file file-A)
    (delete-file file-B)
    (ediff-eval-in-buffer ediff-A-buffer (goto-char point-A))
    (ediff-jump-to-difference (ediff-diff-at-point 'A))
    (beep 1)
    (if (y-or-n-p 
	"Ediff is at last posn in buff A. Stay (or goto last posn in B)? ")
	()
      (ediff-eval-in-buffer ediff-B-buffer (goto-char point-B))
      (ediff-jump-to-difference (ediff-diff-at-point 'B)))
    (message "")
    ))

(defun ediff-remember-buffer-characteristics (&optional arg)
  "Record certain properties of the buffers being compared.
Must be called in the control buffer.  Saves `read-only', `modified',
and `auto-save' properties in buffer local variables.  Turns off
`auto-save-mode'.  These properties are restored via a call to
`ediff-restore-buffer-characteristics'."

  ;; remember and alter buffer characteristics
  (set  (if arg 'ediff-A-buffer-values-setup 'ediff-A-buffer-values)
	(ediff-eval-in-buffer
	 ediff-A-buffer
	 (prog1
	     (emerge-save-variables ediff-saved-variables)
	   (emerge-restore-variables ediff-saved-variables
				     ediff-working-values))))
  (set  (if arg 'ediff-B-buffer-values-setup 'ediff-B-buffer-values)
	(ediff-eval-in-buffer
	 ediff-B-buffer
	 (prog1
	     (emerge-save-variables ediff-saved-variables)
	   (emerge-restore-variables ediff-saved-variables
				     ediff-working-values)))))

(defun ediff-restore-buffer-characteristics (&optional arg)
  "Restores properties saved by `ediff-remember-buffer-characteristics'."
  (let ((A-values (if arg ediff-A-buffer-values-setup ediff-A-buffer-values))
	(B-values (if arg ediff-B-buffer-values-setup ediff-B-buffer-values)))
	
    (ediff-eval-in-buffer ediff-A-buffer
			  (emerge-restore-variables ediff-saved-variables
						    A-values))
    (ediff-eval-in-buffer ediff-B-buffer
			  (emerge-restore-variables ediff-saved-variables
						    B-values))))


;; If optional A-buffer and B-buffer are given, then construct a vector of
;; diff using point values. Otherwise, use line offsets.
(defun ediff-extract-diffs (diff-buffer &optional A-buffer B-buffer)
  (let (diff-list
	(a-prev 1) ;; this is needed to set the first diff line correctly
	(b-prev 1))

    (if (and A-buffer B-buffer)
	(progn    ;; reset point in buffers A and B
	  (ediff-eval-in-buffer
	   A-buffer
	   (goto-char (point-min)))
	  (ediff-eval-in-buffer
	   B-buffer
	   (goto-char (point-min)))))
    
    (ediff-eval-in-buffer
     diff-buffer
     (goto-char (point-min))
     (while (re-search-forward ediff-match-diff-line nil t)
       (let* ((a-begin (string-to-int (buffer-substring (match-beginning 1)
							(match-end 1))))
	      (a-end  (let ((b (match-beginning 3))
			    (e (match-end 3)))
			(if b
			    (string-to-int (buffer-substring b e))
			  a-begin)))
	      (diff-type (buffer-substring (match-beginning 4) (match-end 4)))
	      (b-begin (string-to-int (buffer-substring (match-beginning 5)
							(match-end 5))))
	      (b-end (let ((b (match-beginning 7))
			   (e (match-end 7)))
		       (if b
			   (string-to-int (buffer-substring b e))
			 b-begin)))
	      a-begin-pt a-end-pt b-begin-pt b-end-pt)
	 ;; fix the beginning and end numbers, because diff is somewhat
	 ;; strange about how it numbers lines
	 (if (string-equal diff-type "a")
	     (setq b-end (1+ b-end)
		   a-begin (1+ a-begin)
		   a-end a-begin)
	   (if (string-equal diff-type "d")
	       (setq a-end (1+ a-end)
		     b-begin (1+ b-begin)
		     b-end b-begin)
	     ;; (string-equal diff-type "c")
	     (setq a-end (1+ a-end)
		   b-end (1+ b-end))))
	 (if (and A-buffer B-buffer)
	     (progn    ;; computing main diff vector
	       ;; convert to relative line numbers    
	       (ediff-eval-in-buffer
		A-buffer
		(forward-line (- a-begin a-prev))
		(setq a-begin-pt (point))
		(forward-line (- a-end a-begin))
		(setq a-end-pt (point)
		      a-prev a-end))
	       (ediff-eval-in-buffer
		B-buffer
		(forward-line (- b-begin b-prev))
		(setq b-begin-pt (point))
		(forward-line (- b-end b-begin))
		(setq b-end-pt (point)
		      b-prev b-end))
	       (setq diff-list 
		     (nconc diff-list (list (vector a-begin-pt a-end-pt
						    b-begin-pt b-end-pt)))))
	   ;; computing refinement vector
	   (setq  diff-list 
		  (nconc diff-list (list (vector (- a-begin a-prev)
						 (- a-end a-begin)
						 (- b-begin b-prev)
						 (- b-end b-begin))))
		  a-prev a-end
		  b-prev b-end))
		  
	 ))) ;; end ediff-eval-in-buffer
    diff-list
    ))
    
(defun ediff-convert-diffs-to-overlays (A-buffer B-buffer diff-list)
  (let* ((current-diff -1)
	 (total-diffs (length diff-list))
;	 (control-buffer-suffix ediff-control-buffer-suffix)
	 diff-overlay-list list-element
	 a-begin a-end b-begin b-end
	 a-overlay b-overlay)

    (while diff-list
      (setq current-diff (1+ current-diff)
	    list-element (car diff-list)
	    a-begin 	 (aref list-element 0)
	    a-end 	 (aref list-element 1)
	    b-begin 	 (aref list-element 2)
	    b-end 	 (aref list-element 3))
	    
      ;; Put overlays at appropriate places in buffers
      (setq a-overlay (ediff-make-overlay a-begin a-end A-buffer))
      ;; Priorities of overlays should be equal in all ediff control
      ;; panels buffers. Otherwise it won't work due to Emacs
      ;; bug---insert-in-front-hooks will be called 
      ;; only on behalf of the buffer with higher priority.
      (ediff-overlay-put a-overlay 'priority ediff-shaded-overlay-priority)
      (ediff-overlay-put a-overlay 'ediff-diff-num current-diff)
      (ediff-overlay-put a-overlay
			 'insert-in-front-hooks '(ediff-insert-in-front))
;     (ediff-overlay-put a-overlay
;			 'ediff-control-buffer control-buffer-suffix)
      (ediff-overlay-put a-overlay 
			 'face (if (ediff-odd-p current-diff) ;; odd diff
				   'ediff-odd-diff-face-A-var
				 'ediff-even-diff-face-A-var))
			 
      (setq b-overlay (ediff-make-overlay b-begin b-end B-buffer))
      (ediff-overlay-put b-overlay 'priority ediff-shaded-overlay-priority)
      (ediff-overlay-put b-overlay 'ediff-diff-num current-diff)
      (ediff-overlay-put b-overlay
			 'insert-in-front-hooks '(ediff-insert-in-front))
;     (ediff-overlay-put b-overlay
;			 'ediff-control-buffer control-buffer-suffix)
      (ediff-overlay-put b-overlay 
			 'face (if (ediff-odd-p current-diff) ;; odd diff
				   'ediff-odd-diff-face-B-var
				 'ediff-even-diff-face-B-var))
				 
      (if (ediff-if-lucid) ;; chars inserted at end will be inside extent
	  (progn
	    (ediff-overlay-put a-overlay
			       'ediff-marker 
			       (move-marker (make-marker) a-begin A-buffer))
	    (ediff-overlay-put b-overlay
			       'ediff-marker 
			       (move-marker (make-marker) b-begin B-buffer))
	    (ediff-overlay-put a-overlay 'end-open nil)
	    (ediff-overlay-put b-overlay 'end-open nil)))
			 
      ;; record all overlays for this difference
      (setq diff-overlay-list
	    (nconc diff-overlay-list
		   (list (vector a-overlay b-overlay nil nil)))
	    diff-list
	    (cdr diff-list))
      (message "Processing diff region %d of %d"
	       current-diff total-diffs)
      ) ;; while
    ;; this is just to avoid confusing the user with diff num < total-diffs
    (message "Processing diff region %d of %d"
	       (1+ current-diff) total-diffs)
    ;; convert the list of difference information into a vector for
    ;; fast access
    (apply 'vector diff-overlay-list)))



;;; Commands

(defun ediff-recenter (&optional no-rehighlight)
  "Bring the highlighted region of all buffers A and B into view.
Reestablish the default three-window display."
  (interactive)
  (setq ediff-disturbed-overlays nil) ;; clear after use
  (let (buffer-read-only)
    (if (and (ediff-buffer-live-p ediff-A-buffer)
	     (ediff-buffer-live-p ediff-B-buffer))
	(ediff-setup-windows
	 ediff-A-buffer ediff-B-buffer ediff-control-buffer)))
  ;; Redisplay whatever buffers are showing, if there is a selected difference
  (if (and (ediff-buffer-live-p ediff-A-buffer)
	   (ediff-buffer-live-p ediff-B-buffer)
	   (>= ediff-current-difference 0)
	   (< ediff-current-difference ediff-number-of-differences))
      (let* ( ;; context must be saved before switching to windows A/B
	     (buffer-A ediff-A-buffer)
	     (buffer-B ediff-B-buffer)
	     (wind (selected-window))
	     (control-buf ediff-control-buffer)
	     (before-flag-shift-A (if (eq ediff-highlighting-style 'ascii)
				      (1- (length ediff-before-flag-A))
				    0))
	     (after-flag-shift-A (if (eq ediff-highlighting-style 'ascii)
				     (1- (length ediff-after-flag-A))
				   0))
	     (before-flag-shift-B (if (eq ediff-highlighting-style 'ascii)
				      (1- (length ediff-before-flag-B))
				    0))
	     (after-flag-shift-B (if (eq ediff-highlighting-style 'ascii)
				     (1- (length ediff-after-flag-B))
				   0))
	     (window-A (ediff-get-visible-buffer-window buffer-A))
	     (window-B (ediff-get-visible-buffer-window buffer-B)))
	
	(or no-rehighlight
	    (ediff-operate-on-flags 'insert))
	    
	(if window-A (progn
		       (select-window window-A)
		       (ediff-position-region
			(- (ediff-get-diff-posn 'A 'beg nil control-buf)
			   before-flag-shift-A)
			(+ (ediff-get-diff-posn 'A 'end nil control-buf)
			   after-flag-shift-A)
			(ediff-get-diff-posn 'A 'beg nil control-buf))))
	(if window-B (progn
		       (select-window window-B)
		       (ediff-position-region
			(- (ediff-get-diff-posn 'B 'beg nil control-buf)
			   before-flag-shift-B)
			(+ (ediff-get-diff-posn 'B 'end nil control-buf)
			   after-flag-shift-B)
			(ediff-get-diff-posn 'B 'beg nil control-buf))))
	(select-window wind))))
	
(defun ediff-toggle-split ()
  "Toggle vertical/horizontal window split. 
Does nothing if file-A and file-B are in different frames."
  (interactive)
  (let* ((wind-A (ediff-get-visible-buffer-window ediff-A-buffer))
	 (wind-B (ediff-get-visible-buffer-window ediff-B-buffer))
	 (frame-A (if wind-A (ediff-window-frame wind-A)))
	 (frame-B (if wind-B (ediff-window-frame wind-B))))
    (if (eq frame-A frame-B)
	(setq ediff-split-window-function
	      (if (eq ediff-split-window-function 'split-window-vertically)
		  'split-window-horizontally
		'split-window-vertically))
      (message "No splitting: Buffers A and B are in different frames."))
    (ediff-recenter 'no-rehighlight)))
  
(defun ediff-toggle-hilit ()
  "Switch between highlighting using ASCII flags and highlighting using faces.
On a dumb terminal, switches between ASCII highlighting and no highlighting." 
  (interactive)
  (if (not window-system)
      (if (eq ediff-highlighting-style 'ascii)
	  (progn
	    (message "ASCII highlighting flags removed.")
	    (ediff-unselect-and-select-difference ediff-current-difference
						  'unselect-only)
	    (setq ediff-highlighting-style 'off))
	(ediff-unselect-and-select-difference ediff-current-difference
					      'select-only))
    (ediff-unselect-and-select-difference ediff-current-difference
					  'unselect-only)
    ;; cycle through highlighting
    (cond ((and ediff-want-faces ediff-highlight-all-diffs)
	   (message "Unhighlighting unselected difference regions.")
	   (setq ediff-highlight-all-diffs nil))
	  (ediff-want-faces
	   (message "Highlighting with ASCII flags.")
	   (setq ediff-want-faces nil))
	  (t
	   (message "Re-highlighting all difference regions.")
	   (setq ediff-want-faces t
		 ediff-highlight-all-diffs t)))
		 
    (if (and ediff-want-faces ediff-highlight-all-diffs)
	(if (not (face-differs-from-default-p 'ediff-odd-diff-face-A-var))
	    (progn
	      (copy-face ediff-odd-diff-face-A 'ediff-odd-diff-face-A-var)
	      (copy-face ediff-odd-diff-face-B 'ediff-odd-diff-face-B-var)
	      (copy-face ediff-even-diff-face-A 'ediff-even-diff-face-A-var)
	      (copy-face ediff-even-diff-face-B 'ediff-even-diff-face-B-var)))
      (copy-face 'default 'ediff-odd-diff-face-A-var)
      (copy-face 'default 'ediff-odd-diff-face-B-var)
      (copy-face 'default 'ediff-even-diff-face-A-var)
      (copy-face 'default 'ediff-even-diff-face-B-var))
    
    (ediff-unselect-and-select-difference
     ediff-current-difference 'select-only))
  (ediff-operate-on-flags 'insert)
  )
  
(defun ediff-toggle-autorefine ()
  "Toggle auto-refine mode."
  (interactive)
  (cond ((eq ediff-auto-refine 'nix)
	 (setq ediff-auto-refine 'on)
	 (ediff-make-fine-diffs ediff-current-difference 'noforce)
	 (message "Auto-refining is ON."))
	((eq ediff-auto-refine 'on)
	 (message "Auto-refining is OFF.")
	 (setq ediff-auto-refine 'off))
	(t
	 (ediff-set-fine-diff-properties ediff-current-difference 'default)
	 (message "Refinements are HIDDEN.")
	 (setq ediff-auto-refine 'nix))
	))
  
(defun ediff-toggle-help ()
  "Toggle short/long help message."
  (interactive)
  (let (buffer-read-only)
    (erase-buffer)
    (if (string= ediff-help-message ediff-help-message-long)
	(setq ediff-help-message ediff-help-message-short)
      (setq ediff-help-message ediff-help-message-long)))
  (setq ediff-window-config-saved "") ;; force redisplay
  (ediff-recenter 'no-rehighlight))
  
  
(defun ediff-toggle-read-only-patch-orig ()
  "Used as a startup hook to set `.orig' patch file read-only."
  (ediff-toggle-read-only ediff-A-buffer))
  
(defun ediff-toggle-read-only (&optional buff)
  "Toggles read-only in buffers A and B.
If buffer is under version control and locked, check it out first."
  (interactive)
  ;; Optional argument, BUF, is passed only in a startup hook.
  (or buff (ediff-recenter))
  
  (ediff-eval-in-buffer
   (or buff (if (eq last-command-char ?A) ediff-A-buffer ediff-B-buffer))
   (let* ((file (buffer-file-name (current-buffer)))
	  (file-writable (and file (file-writable-p file)))
	  (toggle-ro-cmd (cond (ediff-toggle-read-only-function)
			       (ediff-local-checkout-flag 
				(if (and file (not file-writable))
				    (progn
				      (beep 1)
				      (message "Warning: file %s is read-only."
					       (abbreviate-file-name file))))
				'toggle-read-only)
			       (file-writable 'toggle-read-only)
			       (t (key-binding "\C-x\C-q")))))
     (if (and toggle-ro-cmd 
	      (string-match "toggle-read-only" (symbol-name toggle-ro-cmd)))
	 (save-window-excursion
	   (setq ediff-local-checkout-flag t)
	   (or buff
	       (select-window
		(ediff-get-visible-buffer-window (current-buffer))))
	   (command-execute toggle-ro-cmd))
       (error "Don't know how to toggle read-only in buffer %S"
	      (current-buffer))))))
   


;;; Window scrolling operations

;; Perform some operation on the two file windows (if they are showing).
;; Catches all errors on the operation in the A and B windows.
;; Usually, errors come from scrolling off the
;; beginning or end of the buffer, and this gives nice nice error messages.
(defun ediff-operate-on-windows (operation arg)
  (let* ((buffer-A ediff-A-buffer)
	 (buffer-B ediff-B-buffer)
	 (wind (selected-window))
	 (window-A (ediff-get-visible-buffer-window buffer-A))
	 (window-B (ediff-get-visible-buffer-window buffer-B)))
      (if window-A (progn
		     (select-window window-A)
		     (condition-case nil
			 (funcall operation arg)
		       (error))))
      (if window-B (progn
		     (select-window window-B)
		     (condition-case nil
			 (funcall operation arg)
		       (error))))
      (select-window wind)
		       ))

(defun ediff-scroll-up (&optional arg)
  "Scroll up buffers A and B, if they are in windows.
With optional argument ARG, scroll ARG lines; otherwise scroll by nearly
the height of window-A."
  (interactive "P")
  (ediff-operate-on-windows
   'scroll-up 
   ;; calculate argument to scroll-up
   ;; if there is an explicit argument
   (if (and arg (not (equal arg '-)))
       ;; use it
       (prefix-numeric-value arg)
     ;; if not, see if we can determine a default amount (the window height)
     (let* ((window-A (ediff-get-visible-buffer-window ediff-A-buffer))
	    (window-B (ediff-get-visible-buffer-window ediff-B-buffer))
	    default-amount)
       (if (or (null window-A) (null window-B))
	   (setq default-amount 0)
	 (setq default-amount 
	       (- (min (window-height window-A) (window-height window-B))
		  1 next-screen-context-lines)))
       ;; the window was found
       (if arg
	   ;; C-u as argument means half of default amount
	   (/ default-amount 2)
	 ;; no argument means default amount
	 default-amount)))))

(defun ediff-scroll-down (&optional arg)
  "Scroll down buffers A and B, if they are in windows.
With optional argument ARG, scroll ARG lines; otherwise scroll by nearly
the height of window-A."
  (interactive "P")
  (ediff-operate-on-windows
   'scroll-down
   ;; calculate argument to scroll-down
   ;; if there is an explicit argument
   (if (and arg (not (equal arg '-)))
       ;; use it
       (prefix-numeric-value arg)
     ;; if not, see if we can determine a default amount (the window height)
     (let* ((window-A (ediff-get-visible-buffer-window ediff-A-buffer))
	    (window-B (ediff-get-visible-buffer-window ediff-B-buffer))
	    default-amount)
       (if (or (null window-A) (null window-B))
	   (setq default-amount 0)
	 (setq default-amount 
	       (- (min (window-height window-A) (window-height window-B))
		  1 next-screen-context-lines)))
       ;; the window was found
       (if arg
	   ;; C-u as argument means half of default amount
	   (/ default-amount 2)
	 ;; no argument means default amount
	 default-amount)))))

(defun ediff-scroll-left (&optional arg)
  "Scroll left buffer-A and buffer-B, if they are in windows.
If an argument is given, that is how many columns are scrolled, else nearly
the width of the A and B windows."
  (interactive "P")
  (ediff-operate-on-windows
   'scroll-left
   ;; calculate argument to scroll-left
   ;; if there is an explicit argument
   (if (and arg (not (equal arg '-)))
       ;; use it
       (prefix-numeric-value arg)
     ;; if not, see if we can determine a default amount
     ;; (half the window width)
     (if (null ediff-control-window)
	 ;; no control window, use nil
	 nil
       (let ((default-amount
	       (- (/ (window-width ediff-control-window) 2) 3)))
	 ;; the window was found
	 (if arg
	     ;; C-u as argument means half of default amount
	     (/ default-amount 2)
	   ;; no argument means default amount
	   default-amount))))))

(defun ediff-scroll-right (&optional arg)
  "Scroll right buffer-A and buffer-B, if they are in windows.
If an argument is given, that is how many columns are scrolled, else nearly
the width of the A and B windows."
  (interactive "P")
  (ediff-operate-on-windows
   'scroll-right
   ;; calculate argument to scroll-right
   ;; if there is an explicit argument
   (if (and arg (not (equal arg '-)))
       ;; use it
       (prefix-numeric-value arg)
     ;; if not, see if we can determine a default amount
     ;; (half the window width)
     (if (null ediff-control-window)
	 ;; no control window, use nil
	 nil
       (let ((default-amount
	       (- (/ (window-width ediff-control-window) 2) 3)))
	 ;; the window was found
	 (if arg
	     ;; C-u as argument means half of default amount
	     (/ default-amount 2)
	   ;; no argument means default amount
	   default-amount))))))

(defun ediff-position-region (beg end pos)
  "This is a variation on `emerge-position-region'. 
The difference is that it always tries to align difference regions in
buffer-A and buffer-B, so that it will be easier to compare them."
  (set-window-start (selected-window) beg)
  (if (pos-visible-in-window-p end)
      ;; Determine the number of lines that the region occupies
      (let ((lines 0))
	(while (> end (progn
			(move-to-window-line lines)
			(point)))
	  (setq lines (1+ lines)))
	;; And position the beginning on the right line
	(goto-char beg)
	(recenter (/ (1+ (max (- (1- (window-height (selected-window)))
				 lines)
			      1)
			 )
		     2))))
  (goto-char pos)
  )


(defun ediff-next-difference (&optional arg)
  "Advance to the next difference. 
With a prefix argument, go back that many differences."
  (interactive "P")
  (if (< ediff-current-difference ediff-number-of-differences)
      (let ((n (min ediff-number-of-differences
		    (+ ediff-current-difference (if arg arg 1))))
	    buffer-read-only)
	    
	(while (and (< n ediff-number-of-differences)
		    (funcall ediff-skip-diff-region-function n))
	  (setq n (1+ n)))
	
	(ediff-unselect-and-select-difference n)
	;; possibly skip inessential difference regions
	(while (and ediff-ignore-similar-regions
		    (< n ediff-number-of-differences)
		    (ediff-no-fine-diffs n))
	  (setq n (1+ n))
	  (ediff-unselect-and-select-difference n))
	) ;; let
    (error "At end of the difference list.")))

(defun ediff-previous-difference (&optional arg)
  "Go to the previous difference. 
With a prefix argument, go back that many differences."
  (interactive "P")
  (if (> ediff-current-difference -1)
      (let ((n (max -1 (- ediff-current-difference (if arg arg 1))))
	    buffer-read-only)
	    
	(while (and (funcall ediff-skip-diff-region-function n)
		    (> n -1))
	  (setq n (1- n)))
	(ediff-unselect-and-select-difference n)
	;; possibly skip inessential difference regions
	(while (and ediff-ignore-similar-regions
		    (> n -1)
		    (ediff-no-fine-diffs n))
	  (setq n (1- n))
	  (ediff-unselect-and-select-difference n))
	) ;; let
    (error "At beginning of the difference list.")))

(defun ediff-jump-to-difference (difference-number)
  "Go to the difference specified as a prefix argument."
  (interactive "p")
  (let (buffer-read-only)
    (setq difference-number (1- difference-number))
    (if (and (>= difference-number -1)
	     (< difference-number (1+ ediff-number-of-differences)))
	(ediff-unselect-and-select-difference difference-number)
      (error "Bad difference number"))))
      
(defun ediff-jump-to-difference-at-point ()
  "Go to the difference closest to the point in buffer A or B.
If this command is invoked via `\\[ediff-jump-to-difference-at-point]' 
then the point in buffer B is used.
Otherwise, buffer A's point is used."
  (interactive)
  (let ((buf-type (ediff-char-to-buftype last-command-char))
	buffer-read-only)
    (ediff-jump-to-difference (ediff-diff-at-point buf-type))))
	
      
;; find region "most related to the current point position      

(defun ediff-diff-at-point (buf-type)
  (let ((buffer (ediff-get-buffer buf-type))
	(ctl-buffer ediff-control-buffer)
	(max-dif-num (1- ediff-number-of-differences))
	(diff-no -1)
	(prev-beg 0)
	(prev-end 0)
	(beg 0)
	(end 0))
	
    (ediff-eval-in-buffer
     buffer
     (while (and (or (< (point) prev-beg) (> (point) beg))
		 (< diff-no max-dif-num))
       (setq diff-no (1+ diff-no))
       (setq prev-beg beg
	     prev-end end)
       (setq beg (ediff-get-diff-posn buf-type 'beg diff-no ctl-buffer)
	     end (ediff-get-diff-posn buf-type 'end diff-no ctl-buffer))
       )
      
     (if (< (abs (- (point) prev-end))
	    (abs (- (point) beg)))
	 diff-no
       (1+ diff-no))  ;; jump-to-diff works with diff nums higher by 1
     )))

;;; Copying diffs.

(defun ediff-diff-to-diff (arg)
  "Copy buffer-A'th diff to buffer B.
If numerical prefix argument, copy this diff specified in the arg.
Otherwise, copy the difference given by `ediff-current-difference'." 
  (interactive "P")
  (if arg
      (ediff-jump-to-difference arg))
  (let* ((key1 (aref (this-command-keys) 0))
	 (key2 (aref (this-command-keys) 1))
	 (char1 (if (ediff-if-lucid) (event-key key1) key1))
	 (char2 (if (ediff-if-lucid) (event-key key2) key2)))
    (ediff-copy-diff ediff-current-difference
		     (ediff-char-to-buftype char1)
		     (ediff-char-to-buftype char2))
    (ediff-recenter 'no-rehighlight)))


(defun ediff-copy-diff (n from-buf-type to-buf-type)
  "Copy diff N from FROM-BUF-TYPE \(given as 'A or 'B\) to TO-BUF-TYPE."
  (let* ((to-buf (ediff-get-buffer to-buf-type))
	 (from-buf (ediff-get-buffer from-buf-type))
	 (ctrl-buf ediff-control-buffer)
	 reg-to-copy reg-to-delete
	 reg-to-delete-beg reg-to-delete-end)
	
    (ediff-operate-on-flags 'remove)
    (setq reg-to-delete-beg
	  (ediff-get-diff-posn to-buf-type 'beg n ctrl-buf))
    (setq reg-to-delete-end
	  (ediff-get-diff-posn to-buf-type 'end n ctrl-buf))
    (setq reg-to-copy (ediff-eval-in-buffer
		       from-buf
		       (buffer-substring (ediff-get-diff-posn
					  from-buf-type 'beg n ctrl-buf)
					 (ediff-get-diff-posn
					  from-buf-type 'end n ctrl-buf))))
    (setq reg-to-delete (ediff-eval-in-buffer
			 to-buf
			 (buffer-substring reg-to-delete-beg
					   reg-to-delete-end)))
    (setq ediff-disturbed-overlays nil) ;; clear before use
    
    (if (string= reg-to-delete reg-to-copy)
	(progn
	  (ding)
	  (message
	   "Diff regions %d are identical in buffers %S and %S. Nothing copied." 
	   (1+ n) from-buf-type to-buf-type))
	
      ;; seems ok to copy
      (if (ediff-test-save-region n to-buf-type)
	    (condition-case conds
		(progn
		  (ediff-eval-in-buffer
		   to-buf
		   ;; to prevent flags from interfering if buffer is writable
		   (let ((inhibit-read-only (null buffer-read-only))
			 before-change-function)
		     (goto-char reg-to-delete-end)
		     (insert-before-markers reg-to-copy)
		     (if (ediff-if-lucid)
			 (progn
			   (ediff-collect-extents-lucid reg-to-delete-beg)
			   (if (> reg-to-delete-end reg-to-delete-beg)
			       (progn
				 (kill-region reg-to-delete-beg
					      reg-to-delete-end) 
				 (if (string= reg-to-copy "")
				     (ediff-adjust-disturbed-extents-lucid
				      reg-to-delete-beg)))))
		       (if (> reg-to-delete-end reg-to-delete-beg)
			   (kill-region reg-to-delete-beg reg-to-delete-end)
			 (ediff-move-disturbed-overlays reg-to-delete-beg)))
		     ))
		  (ediff-save-diff-region n to-buf-type reg-to-delete))
	      (error (message "%s %s"
			      (car conds)
			      (mapconcat 'prin1-to-string (cdr conds) " "))
		     (beep 1))))
      )
    (ediff-operate-on-flags 'insert)
    ))
     
(defun ediff-save-diff-region (n buf-type reg)
  "Save Nth diff of buffer BUF-TYPE \(`A' or `B'\).
That is to say, the Nth diff on the `ediff-killed-diffs-alist'.  REG
is the region to save.  It is redundant here, but is passed anyway, for
convenience."

  (let* ((n-th-diff-saved (assoc n ediff-killed-diffs-alist))
	 (this-buf-n-th-diff-saved (assoc buf-type (cdr n-th-diff-saved))))
	 
    (if this-buf-n-th-diff-saved
	;; either nothing saved for n-th diff and buffer or we OK'ed
	;; overriding
	(setcdr this-buf-n-th-diff-saved reg)
      (if n-th-diff-saved ;; n-th diff saved, but for another buffer
	  (nconc n-th-diff-saved  (list (cons buf-type reg)))
	(setq ediff-killed-diffs-alist  ;; create record for n-th diff
	      (cons (list n (cons buf-type reg))
		    ediff-killed-diffs-alist))))
    (message "Saved diff region #%d for buffer %S. To recover hit 'r%s'."
	     (1+ n) buf-type
	     (downcase (symbol-name buf-type)))))
    
(defun ediff-test-save-region (n buf-type)
  "Test if saving Nth difference region of buffer BUF-TYPE is possible."
  (let* ((n-th-diff-saved (assoc n ediff-killed-diffs-alist))
	 (this-buf-n-th-diff-saved (assoc buf-type (cdr n-th-diff-saved))))
	 
    (if this-buf-n-th-diff-saved
	(if (yes-or-no-p
	     (format 
	      "You've previously copied diff region %d to buffer %S. Confirm."
	      (1+ n) buf-type))
	    t
	  (error "Quit."))
      t)))
	  
(defun ediff-pop-diff (n buf-type)
  "Pop last killed Nth diff region from buffer BUF-TYPE."
  (let* ((n-th-record (assoc n ediff-killed-diffs-alist))
	 (saved-rec (assoc buf-type (cdr n-th-record)))
	 (buf (ediff-get-buffer buf-type))
	 saved-diff reg-beg reg-end recovered)
	
    (if (cdr saved-rec)
	(setq saved-diff (cdr saved-rec))
      (if (> ediff-number-of-differences 0)
	  (error "Nothing saved for diff %d in buffer %S." (1+ n) buf-type)
	(error "No differences found.")))
    
    (ediff-operate-on-flags 'remove)
	
    (setq reg-beg (ediff-get-diff-posn buf-type 'beg n ediff-control-buffer))
    (setq reg-end (ediff-get-diff-posn buf-type 'end n ediff-control-buffer))
    (setq ediff-disturbed-overlays nil) ;; clear before use
    
    (condition-case conds
	(ediff-eval-in-buffer
	 buf
	 (let ((inhibit-read-only (null buffer-read-only))
	       (before-change-function nil))
	   (goto-char reg-end)
	   (insert-before-markers saved-diff)
	   
	   (if (ediff-if-lucid)
	       (progn
		 (ediff-collect-extents-lucid reg-beg)
		 (if (> reg-end reg-beg)
		     (progn
		       (kill-region reg-beg reg-end)
		       (if (string= saved-diff "")
			   (ediff-adjust-disturbed-extents-lucid reg-beg)))))
	     (if (> reg-end reg-beg)
		 (kill-region reg-beg reg-end)
	       (ediff-move-disturbed-overlays reg-beg)))
	     
	   (setq recovered t)
	   ))
      (error (message "%s %s"
		      (car conds)
		      (mapconcat 'prin1-to-string (cdr conds) " "))
	     (beep 1)))
    
    (ediff-operate-on-flags 'insert)
    (if recovered
	(progn
	  (setq  n-th-record (delq saved-rec n-th-record))
	  (message "Restored diff region %d in buffer %S." (1+ n) buf-type)))
    ))
      
(defun ediff-restore-diff  (arg)
  "Restore ARGth diff from `ediff-killed-diffs-alist'.
ARG is a prefix argument.  If ARG is nil, restore current-difference."
  (interactive "P")
  (if arg
      (ediff-jump-to-difference arg))
  (ediff-pop-diff ediff-current-difference 
		  (ediff-char-to-buftype last-command-char))
  (ediff-recenter 'no-rehighlight))
  
(defun ediff-toggle-regexp-match ()
  "Toggle focus on difference regions that match a regexp or hide those diffs."
  (interactive)
  (let (regexp-A regexp-B)
    (cond
     ((or (and (eq ediff-skip-diff-region-function 'ediff-focus-on-regexp-matches)
	       (eq last-command-char ?f))
	  (and (eq ediff-skip-diff-region-function 'ediff-hide-regexp-matches)
	       (eq last-command-char ?h)))
      (message "Selective browsing by regexp turned off.")
      (setq ediff-skip-diff-region-function 'ediff-show-all-diffs))
     ((eq last-command-char ?h)
      (setq ediff-skip-diff-region-function 'ediff-hide-regexp-matches
	    regexp-A 
	    (read-string
	     (format 
	      "Ignore A-regions matching this regexp (default \"%s\"): "
	      (regexp-quote ediff-regexp-hide-A)))
	    regexp-B
	    (read-string
	     (format 
	      "Ignore B-regions matching this regexp (default \"%s\"): "
	      (regexp-quote ediff-regexp-hide-B))))
      (message "Hide difference regions matching regexp.")
      (or (string= regexp-A "") (setq ediff-regexp-hide-A regexp-A))
      (or (string= regexp-B "") (setq ediff-regexp-hide-B regexp-B)))
     ((eq last-command-char ?f)
      (setq ediff-skip-diff-region-function 'ediff-focus-on-regexp-matches
	    regexp-A 
	    (read-string
	     (format 
	      "Focus on A-regions matching this regexp (default \"%s\"): "
	      (regexp-quote ediff-regexp-focus-A)))
	    regexp-B
	    (read-string
	     (format 
	      "Focus on B-regions matching this regexp (default \"%s\"): "
	      (regexp-quote ediff-regexp-focus-B))))
      (message "Focus on difference regions matching regexp.")
      (or (string= regexp-A "") (setq ediff-regexp-focus-A regexp-A))
      (or (string= regexp-B "") (setq ediff-regexp-focus-B regexp-B))))))
      
(defun ediff-toggle-skip-similar ()
  (interactive)
  (setq ediff-ignore-similar-regions (not ediff-ignore-similar-regions))
  (if ediff-ignore-similar-regions
      (message "Skipping over regions that differ only in white space & line breaks.")
    (message "Skipping over white-space differences turned off.")))
  
(defun ediff-show-all-diffs (n)
  "Don't skip difference regions."
  nil)
  
(defun ediff-focus-on-regexp-matches (n)
  "Focus on diffs that match regexp `ediff-regexp-focus-A/B'.
Regions to be ignored according to this function are those where   
buf A region doesn't match `ediff-regexp-focus-A' and buf B region
doesn't match `ediff-regexp-focus-B'.
This function returns nil if the region number N (specified as
an argument) is not to be ignored and t if region N is to be ignored.

N is a region number used by Ediff internally. It is 1 less
the number seen by the user."
  (if (and (>= n 0) (< n ediff-number-of-differences))
      (let* ((ctl-buf ediff-control-buffer)
	     (regex-A ediff-regexp-focus-A)
	     (regex-B ediff-regexp-focus-B)
	     (reg-A-match (ediff-eval-in-buffer
			   ediff-A-buffer
			   (goto-char (ediff-get-diff-posn 'A 'beg n ctl-buf))
			   (re-search-forward
			    regex-A
			    (ediff-get-diff-posn 'A 'end n ctl-buf)
			    t)))
	     (reg-B-match (ediff-eval-in-buffer
			   ediff-B-buffer
			   (goto-char (ediff-get-diff-posn 'B 'beg n ctl-buf))
			   (re-search-forward
			    regex-B
			    (ediff-get-diff-posn 'B 'end n ctl-buf)
			    t))))
	(not (and reg-A-match reg-B-match)))))
  
(defun ediff-hide-regexp-matches (n)  
  "Hide diffs that match regexp `ediff-regexp-hide-A/B'.
Regions to be ignored are those where buf A region matches
`ediff-regexp-hide-A' and buf B region matches `ediff-regexp-hide-B'.
This function returns nil if the region number N (specified as
an argument) is not to be ignored and t if region N is to be ignored.

N is a region number used by Ediff internally. It is 1 less
the number seen by the user."
  (if (and (>= n 0) (< n ediff-number-of-differences))
      (let* ((ctl-buf ediff-control-buffer)
	     (regex-A ediff-regexp-hide-A)
	     (regex-B ediff-regexp-hide-B)
	     (reg-A-match (ediff-eval-in-buffer
			   ediff-A-buffer
			   (goto-char (ediff-get-diff-posn 'A 'beg n ctl-buf))
			   (re-search-forward
			    regex-A
			    (ediff-get-diff-posn 'A 'end n ctl-buf)
			    t)))
	     (reg-B-match (ediff-eval-in-buffer
			   ediff-B-buffer
			   (goto-char (ediff-get-diff-posn 'B 'beg n ctl-buf))
			   (re-search-forward
			    regex-B
			    (ediff-get-diff-posn 'B 'end n ctl-buf)
			    t))))
	(and reg-A-match reg-B-match))))
    

;;; Quitting, suspending, etc.
(defun ediff-quit ()
  "Finish an Ediff session and exit Ediff.
Unselects the selected difference, if any, restores the read-only and modified
flags of the compared file buffers, kills Ediff buffers for this session
\(but not file-A and file-B\)."
  (interactive)
  (if (prog1
	  (y-or-n-p "Do you really want to exit Ediff? ")
	(message ""))
      (ediff-really-quit)))


;; Perform the quit operations.
(defun ediff-really-quit ()
  (setq ediff-help-message ediff-help-message-long)
  (ediff-restore-buffer-characteristics t) ;; restore as they were at setup
  (ediff-unhighlight-diffs-totally)
  (ediff-clear-diff-vector ediff-difference-vector 'fine-diffs-also)
  (if ediff-temp-file-A (delete-file ediff-temp-file-A))
  (if ediff-temp-file-B (delete-file ediff-temp-file-B))
  
  ;; restore buffer mode line id's in buffer-A/B
  (let ((control-buffer ediff-control-buffer))
    (condition-case nil
	(ediff-eval-in-buffer
	 ediff-A-buffer
	 (setq before-change-function nil)
	 (setq ediff-this-buffer-control-sessions 
	       (delq control-buffer ediff-this-buffer-control-sessions))
	 (if (null ediff-this-buffer-control-sessions)
	     (setq local-write-file-hooks 
		   (delq 'ediff-block-write-file local-write-file-hooks)))
	 (kill-local-variable 'ediff-local-checkout-flag)
	 (kill-local-variable 'mode-line-buffer-identification))
      (error))
      
    (condition-case nil
	(ediff-eval-in-buffer
	 ediff-B-buffer
	 (setq ediff-this-buffer-control-sessions 
	       (delq control-buffer ediff-this-buffer-control-sessions))
	 (if (null ediff-this-buffer-control-sessions)
	     (setq local-write-file-hooks 
		   (delq 'ediff-block-write-file local-write-file-hooks)))
	 (setq before-change-function nil)
	 (kill-local-variable 'ediff-local-checkout-flag)
	 (kill-local-variable 'mode-line-buffer-identification))
      (error)))
   
  (run-hooks 'ediff-quit-hooks))
  
(defun ediff-kill-buffer-carefully (buf)
  "Kill buffer BUF if it exists."
  (if (ediff-buffer-live-p buf)
      (kill-buffer (get-buffer buf))))

;; The default way of quitting Ediff.
;; Kills control buffers and leaves the
;; frame split between the two diff'ed files.
(defun ediff-default-quit-hook ()
  (let ((buff-A ediff-A-buffer)
	(buff-B ediff-B-buffer))
    (ediff-kill-buffer-carefully ediff-diff-buffer)
    (ediff-kill-buffer-carefully ediff-fine-diff-buffer)
    (ediff-kill-buffer-carefully ediff-tmp-buffer)
    (ediff-kill-buffer-carefully ediff-error-buffer)
    (ediff-kill-buffer-carefully ediff-control-buffer)
    (ediff-kill-buffer-carefully ediff-patch-diagnostics)
    (delete-other-windows)
    
    ;; display only if not visible
    (condition-case nil
	(or (ediff-get-visible-buffer-window buff-B)
	    (switch-to-buffer buff-B))
      (error))
    (condition-case nil
	(or (ediff-get-visible-buffer-window buff-A)
	    (progn
	      (if (ediff-get-visible-buffer-window buff-B)
		  (split-window-vertically))
	      (switch-to-buffer buff-A)))
      (error))
    (message "")
    ))
    
;; The default way of suspending Ediff.
;; Buries Ediff buffers, kills all windows.
(defun ediff-default-suspend-hook ()
  (let ((buf-A ediff-A-buffer)
	(buf-B ediff-B-buffer)
	(buf-patch ediff-patch-buf)
	(buf-patch-diag ediff-patch-diagnostics)
	(buf-err  ediff-error-buffer)
	(buf-diff ediff-diff-buffer)
	(buf-fine-diff ediff-fine-diff-buffer))
    (bury-buffer) ;; ediff-control-buffer
    (delete-other-windows)
    (bury-buffer buf-err)
    (bury-buffer buf-diff)
    (bury-buffer buf-fine-diff)
    (bury-buffer buf-patch)
    (bury-buffer buf-patch-diag)
    (bury-buffer buf-A)
    (bury-buffer buf-B)))
     
     
(defun ediff-suspend ()
  "Suspend Ediff.
To resume, switch to the appropriate `Ediff Control Panel'
buffer and then type \\[ediff-recenter].  Ediff will automatically set
up an appropriate window config."
  (interactive)
  (let ((key (substitute-command-keys "\\[ediff-recenter]")))
  (run-hooks 'ediff-suspend-hooks)
  (message
   "To resume Ediff, switch to Ediff Control Panel and hit '%S'" key)))


(defun ediff-status-info ()
  "Show the names of the buffers or files being operated on by Ediff.
Hit \\[ediff-recenter] to reset the windows afterward."
  (interactive)
  (with-output-to-temp-buffer " *ediff-info*"
    (princ (ediff-version))
    (princ "\n\n")
    (ediff-eval-in-buffer ediff-A-buffer
			   (if buffer-file-name
			       (princ
				(format "File A is: %s\n" buffer-file-name))
			     (princ 
			      (format "Buffer A is: %s\n" (buffer-name)))))
    (ediff-eval-in-buffer ediff-B-buffer
			   (if buffer-file-name
			       (princ
				(format "File B is: %s\n" buffer-file-name))
			     (princ 
			      (format "Buffer B is: %s\n" (buffer-name)))))
			      
    (let* ((A-line (ediff-eval-in-buffer ediff-A-buffer
				       (count-lines (point-min) (point))))
	   (B-line (ediff-eval-in-buffer ediff-B-buffer
				       (count-lines (point-min) (point)))))
      (princ (format "\nPoint position in buffer A = %d\n" A-line))
      (princ (format "Point position in buffer B = %d\n" B-line)))
      
    (princ (format "\nCurrent difference number = %S\n"
		   (cond ((< ediff-current-difference 0) 'start)
			 ((>= ediff-current-difference
			      ediff-number-of-differences) 'end)
			 (t (1+ ediff-current-difference)))))

    (cond (ediff-ignore-similar-regions
	   (princ "\nSkipping over regions that differ only in white space & line breaks."))
	  (t 
	   (princ "\nNo skipping over regions that differ in white space & line breaks.")))
	   
    (cond ((eq ediff-skip-diff-region-function 'ediff-show-all-diffs)
	   (princ "\nSelective browsing by regexp is off.\n"))
	  ((eq ediff-skip-diff-region-function 'ediff-hide-regexp-matches)
	   (princ
	    "\nIgnoring regions that match")
	   (princ
	    (format "\n\t regexp `%s' in buffer A  and\n\t regexp `%s' in buffer B\n"
		    ediff-regexp-hide-A ediff-regexp-hide-B)))
	  ((eq ediff-skip-diff-region-function 'ediff-focus-on-regexp-matches)
	   (princ
	    "\nFocusing on regions that match")
	   (princ
	    (format "\n\t regexp `%s' in buffer A  and\n\t regexp `%s' in buffer B\n"
		    ediff-regexp-focus-A ediff-regexp-focus-B)))
	  (t (princ "\nSelective browsing via a user-defined method.\n")))
    
    (princ "\nBugs:  M-x ediff-submit-report")
    ))



;;; Support routines

;; Select a difference by placing the ASCII flags around the appropriate
;; group of lines in the A, B buffers
(defun ediff-select-difference (n)
  (if (and (ediff-buffer-live-p ediff-A-buffer)
	   (ediff-buffer-live-p ediff-B-buffer)
	   (>= n 0) (< n ediff-number-of-differences))
      (progn
	(ediff-remember-buffer-characteristics)
	(if (and window-system ediff-want-faces)
	    (progn
	      (ediff-highlight-diff n)
	      (setq ediff-highlighting-style 'face))
	  (setq ediff-highlighting-style 'ascii)
	  (ediff-place-flags-in-buffer 'A ediff-A-buffer
				       ediff-control-buffer n)
	  (ediff-place-flags-in-buffer 'B ediff-B-buffer
				       ediff-control-buffer n)) 
	  
	(cond ((eq ediff-auto-refine 'on)
	       (if (and
		    (> ediff-auto-refine-limit
		       (- (ediff-get-diff-posn 'A 'end n)
			  (ediff-get-diff-posn 'A 'beg n)))
		    (> ediff-auto-refine-limit
		       (- (ediff-get-diff-posn 'B 'end n)
			  (ediff-get-diff-posn 'B 'beg n))))
		   (ediff-make-fine-diffs n 'noforce)
		 (ediff-make-fine-diffs n 'skip)))
	      
	      ((eq ediff-auto-refine 'off)       ; highlight iff fine diffs
	       (ediff-make-fine-diffs n 'skip))) ; already exist 
     
	(ediff-restore-buffer-characteristics)
	(run-hooks 'ediff-select-hooks))))
	

;; Unselect a difference by removing the ASCII flags in the buffers.
(defun ediff-unselect-difference (n)
  (if (and (>= n 0) (< n ediff-number-of-differences))
      (progn 
	(ediff-remember-buffer-characteristics)
	
	(cond ((and window-system ediff-want-faces)
	       (ediff-unhighlight-diff))
	      ((eq ediff-highlighting-style 'ascii)
	       (ediff-remove-flags-from-buffer
		ediff-A-buffer
		(ediff-get-diff-posn 'A 'beg n)
		(ediff-get-diff-posn 'A 'end n)
		ediff-before-flag-A ediff-after-flag-A)
	       (ediff-remove-flags-from-buffer
		ediff-B-buffer
		(ediff-get-diff-posn 'B 'beg n)
		(ediff-get-diff-posn 'B 'end n)
		ediff-before-flag-B ediff-after-flag-B)))
		
	(ediff-restore-buffer-characteristics)
	(setq ediff-highlighting-style nil)
	
	;; unhighlight fine diffs
	(ediff-set-fine-diff-properties ediff-current-difference 'default)
	
	(run-hooks 'ediff-unselect-hooks))))
  

;; Unselects prev diff and selects a new one, if FLAG has value other than
;; 'select-only or 'unselect-only.  If FLAG is 'select-only, the
;; next difference is selected, but the current selection is not
;; unselected.  If FLAG is 'unselect-only then the current selection is
;; unselected, but the next one is not selected.  If NO-RECENTER is non-nil,
;; don't recenter buffers after selecting/unselecting.
;; 
;; Don't use `ediff-select-difference' and `ediff-unselect-difference'
;; directly, since this will screw up the undo info in the presence of
;; ASCII flags. 
;; Instead, use `ediff-unselect-and-select-difference' with appropriate
;; flags.

(defun ediff-unselect-and-select-difference (n &optional flag no-recenter)
  (let (;; save buf modified info
	(control-buf ediff-control-buffer)
	(buf-A-modified (buffer-modified-p ediff-A-buffer))
	(buf-B-modified (buffer-modified-p ediff-B-buffer))
	;; temporarily disable undo so highlighting won't confuse the user
	buf-A-undo buf-B-undo)
	
    (let ((ediff-current-difference n))
      (or no-recenter
	  (ediff-recenter 'no-rehighlight)))
	  
    (if (and (ediff-buffer-live-p ediff-A-buffer) 
	     (ediff-buffer-live-p ediff-B-buffer))
	(progn
	  (ediff-eval-in-buffer
	   ediff-A-buffer
	   (setq buf-A-undo buffer-undo-list))
	  (ediff-eval-in-buffer
	   ediff-B-buffer
	   (setq buf-B-undo buffer-undo-list))
    
	  (buffer-disable-undo ediff-A-buffer)
	  (buffer-disable-undo ediff-B-buffer)))
    
    (unwind-protect    ;; we don't want to lose undo info due to error
	(progn
	  (or (eq flag 'select-only)
	      (ediff-unselect-difference ediff-current-difference))
	  
	  ;; Auto-save buffers while Ediff flags are temporarily removed.
	  (ediff-eval-in-buffer
	   ediff-A-buffer
	   (if buf-A-modified
	       (do-auto-save)))
	  (ediff-eval-in-buffer
	   ediff-B-buffer
	   (if buf-B-modified
	       (do-auto-save)))
	  
	  (or (eq flag 'unselect-only)
	      (ediff-select-difference n))
	  (setq ediff-current-difference n)
	  ) ;; end protected section
      
      (ediff-eval-in-buffer
       control-buf
       (ediff-refresh-mode-line)
       ;; restore undo and buffer-modified info
       (ediff-eval-in-buffer
	ediff-A-buffer
	(set-buffer-modified-p buf-A-modified)
	(setq buffer-undo-list buf-A-undo)))
      
      (ediff-eval-in-buffer
       control-buf
       (ediff-eval-in-buffer
	ediff-B-buffer
	(set-buffer-modified-p buf-B-modified)
	(setq buffer-undo-list buf-B-undo)))
      )))

;; Revise the mode line to display which difference we have selected

(defun ediff-refresh-mode-line ()
  (setq mode-line-buffer-identification
	(cond ((< ediff-current-difference 0)
	       (list (format "%%b:  At start of %d diffs"
			     ediff-number-of-differences)))
	      ((>= ediff-current-difference ediff-number-of-differences)
	       (list (format "%%b:  At end of %d diffs"
			     ediff-number-of-differences)))
	      (t
	       (list (format "%%b:  diff %d of %d"
			     (1+ ediff-current-difference)
			     ediff-number-of-differences)))))
  ;; Force mode-line redisplay
  (force-mode-line-update))



;; Verify that we have a difference selected.
(defun ediff-validate-difference ()
  (if (not (and (>= ediff-current-difference 0)
		(< ediff-current-difference ediff-number-of-differences)))
      (error "No difference selected")))

(defun ediff-read-file-name (prompt default-dir default-file)
; This is a modified version of a similar function in `emerge.el'.
; PROMPT should not have trailing ': ', so that it can be modified
; according to context.
; If default-file is set, it should be used as the default value.
; If default-dir is non-nil, use it as the default directory.
; Otherwise, use the value of Emacs' variable `default-directory.'

  ;; hack default-dir if it is not set
  (setq default-dir
	(file-name-as-directory
	 (abbreviate-file-name
	  (expand-file-name (or default-dir
				(and default-file
				     (file-name-directory default-file))
				default-directory)))))

  ;; strip the directory from default-file
  (if default-file
      (setq default-file (file-name-nondirectory default-file)))

  (let (f)
    (setq f (expand-file-name
	     (read-file-name
	      (format "%s%s: "
		      prompt
		      (if default-file
			  (concat " (default " default-file ")")
			""))
	      default-dir
	      default-file
	      'confirm
	      default-file
	      )
	     default-dir
	     ))
    ;; If user enters a directory name, expand the default file in that
    ;; directory.  This allows the user to enter a directory name for the
    ;; B-file and diff against the default-file in that directory instead
    ;; of a DIRED listing!
    (if (and (file-directory-p f) default-file)
	(setq f (expand-file-name
		 (file-name-nondirectory default-file) f)))
    f)) 
  
;; If `prefix' is given, then it is used as a prefix for the temp file
;; name. Otherwise, `.buffer-name' is used. If `file' is given, use this
;; file and don't create a new one.
(defun ediff-make-temp-file (&optional prefix given-file)
  (let ((f (or given-file
	       (make-temp-name (concat
				ediff-temp-file-prefix
				(or prefix
				    (format
				     ".%s"
				     "buf")))))))
    ;; create the file
    (write-region (point-min) (point-max) f nil 'no-message) 
    (set-file-modes f ediff-temp-file-mode)
    f))

;; Quote metacharacters (using \) when executing diff in Unix, but not in
;; EMX OS/2
(defun ediff-protect-metachars (str)
  (or (eq system-type 'emx)
      (let ((limit 0))
	(while (string-match emerge-metachars str limit)
	  (setq str (concat (substring str 0 (match-beginning 0))
			  "\\"
			  (substring str (match-beginning 0))))
	  (setq limit (1+ (match-end 0))))))
  str)

;; Make sure the current buffer (for a file) has the same contents as the
;; file on disk, and attempt to remedy the situation if not.
;; Signal an error if we can't make them the same, or the user doesn't want
;; to do what is necessary to make them the same.
;; If file has file handlers (indicated by the optional arg), then we
;; offer to instead of saving. This is one difference with Emerge. 
;; Another is that we always offer to revert obsolete files, whether they
;; are modified or not.
(defun ediff-verify-file-buffer (&optional file-magic)
  ;; First check if the file has been modified since the buffer visited it.
  (if (verify-visited-file-modtime (current-buffer))
      (if (buffer-modified-p)
	  ;; If buffer is not obsolete and is modified, offer to save
	  (if (yes-or-no-p 
	       (format "Buffer out of sync with visited file. %s file %s? "
		       (if file-magic "Revert" "Save")
		       buffer-file-name))
	      (if (not file-magic)
		  (save-buffer)
		;; for some reason, file-name-handlers append instead of
		;; replacing, so we have to erase first.
		(erase-buffer)
		(revert-buffer t t))
	    (error "Buffer out of sync for file %s" buffer-file-name))
	;; If buffer is not obsolete and is not modified, do nothing
	nil)
    ;; If buffer is obsolete, offer to revert
    (if (yes-or-no-p
	 (format "Buffer out of sync with visited file. Revert file %s? "
		 buffer-file-name))
	(progn
	  (if file-magic
	      (erase-buffer))
	  (revert-buffer t t))
      (error "Buffer out of sync for file %s" buffer-file-name))))


(defun ediff-block-write-file ()    
  "Prevent writing files A and B directly."
  (if (ediff-check-for-ascii-flags)
      (error "Type 'wa' and 'wb' in Ediff Control Panel to save buffs A/B.")))

(defun ediff-check-for-ascii-flags ()
  (eval
   (cons 'or
	 (mapcar (function (lambda (buf)
			     (if (ediff-buffer-live-p buf)
				 (ediff-eval-in-buffer
				  buf
				  (eq ediff-highlighting-style 'ascii)))))
		 ediff-this-buffer-control-sessions))))

(defun ediff-insert-in-front (overl beg end)
  "Capture overlays that had insertions in the front.
Called when overlay OVERL gets insertion in front."
  (if (ediff-overlay-get overl 'ediff-diff-num)
      (setq ediff-disturbed-overlays
	    (cons overl ediff-disturbed-overlays)))
  )
  
(defun ediff-collect-extents-lucid (pos)
  "Collects all extents at POS having property `ediff-diff-num'.
Lucid Emacs causes headache by detaching empty extents, so I have to save
them before they disappear."
  (let (lis elt)
    (while (setq elt (extent-at pos nil 'ediff-diff-num elt))
      (setq lis (cons elt lis)))
    (setq ediff-disturbed-overlays lis)))
  
(defun ediff-move-disturbed-overlays (posn)  
  (mapcar (function (lambda (overl)
		       (ediff-move-overlay overl
					   posn
					   (ediff-overlay-end overl))
		       ))
	  ediff-disturbed-overlays)
  (setq ediff-disturbed-overlays nil))
  
(defun ediff-adjust-disturbed-extents-lucid (posn &optional posn-type)
;; POSN-TYPE tells if POSN should become a new start of the extents
;; (if 'new-start) or a new end (if 'new-end). If POSN-TYPE is nil, then
;; POSN is both the new start and the new end.
  (mapcar (function (lambda (overl)
		       (cond ((and (null posn-type)
				   (equal (ediff-overlay-start overl)
					  (ediff-overlay-end overl)))
			      (ediff-move-overlay overl posn posn))
			   
			     (posn-type
			      (ediff-move-overlay
			       overl
			       (if (eq posn-type 'new-start)
				   posn
				 (ediff-overlay-start overl))
			       (if (eq posn-type 'new-end)
				   posn
				 (ediff-overlay-end overl)))))))
	  ediff-disturbed-overlays)
    (setq ediff-disturbed-overlays nil))
  
(defun ediff-save-buffer ()
  "Safe way of saving buffers A, B, and the diff output.
`wa' saves buffer A, `wb' saves buffer B, and `wf' saves the diff output."
  (interactive)
  (let ((hooks local-write-file-hooks))
    (ediff-unselect-and-select-difference ediff-current-difference
					  'unselect-only)
    (unwind-protect
	(ediff-eval-in-buffer
	 (cond ((eq last-command-char ?a)
		ediff-A-buffer)
	       ((eq last-command-char ?b)
		ediff-B-buffer)
	       ((eq last-command-char ?f)
		(message "Saving diff output ...")(sit-for 1)
		ediff-diff-buffer))
	 ;; temporarily remove writing block 
	 (setq hooks (delq 'ediff-block-write-file hooks))
	 (let ((local-write-file-hooks hooks))
	   (save-buffer)))
      (ediff-unselect-and-select-difference ediff-current-difference
					    'select-only)
      )))
    

       
;; Essentially `emerge-remove-flags-in-buffer', modified to allow deletion
;; of read-only flags.
(defun ediff-remove-flags-from-buffer (buffer before-posn after-posn
					      before-flag after-flag)
  (ediff-eval-in-buffer
   buffer
   (let ((before-flag-length (length before-flag))
	 (after-flag-length (length after-flag))
	 (inhibit-read-only t)
	 buffer-read-only
	 before-change-function)
     (goto-char after-posn)
     (setq after-posn (point-marker)) ;; after-posn is now a marker
     ;; remove the flags, if they're there
     (goto-char (- before-posn before-flag-length))
     (if (ediff-if-lucid)
	 (ediff-collect-extents-lucid (+ (point) before-flag-length)))
     (if (looking-at (regexp-quote before-flag))
	 (delete-region (point) (+ (point) before-flag-length))
       ;; the flag isn't there
       (ding)
       (message "Trouble removing ASCII flag"))
     (if (ediff-if-lucid)
	 (ediff-adjust-disturbed-extents-lucid (point)))
     
     (if (ediff-if-lucid)
	 (ediff-collect-extents-lucid (point)))
     (goto-char after-posn)
     (if (looking-at (regexp-quote after-flag))
	 (delete-region (point) (+ (point) after-flag-length))
       ;; the flag isn't there
       (ding)
       (message "Trouble removing ASCII flag"))
     (if (ediff-if-lucid)
	 (ediff-adjust-disturbed-extents-lucid (point)))
     (setq after-posn nil) ;; after has become a marker--garbage-collect
     )))


;; This is a modified `emerge-place-flags-in-buffer'.
(defun ediff-place-flags-in-buffer (buf-type buffer ctl-buffer difference)
  (ediff-eval-in-buffer
   buffer
   (ediff-place-flags-in-buffer1 buf-type ctl-buffer difference)))

;; Modified `emerge-place-flags-in-buffer1'.
(defun ediff-place-flags-in-buffer1 (buf-type ctl-buffer difference)
  (let ((before-flag-name (if (eq buf-type 'A)
			       'ediff-before-flag-A
			    'ediff-before-flag-B))
	(after-flag-name (if (eq buf-type 'A)
			       'ediff-after-flag-A
			     'ediff-after-flag-B))
	(inhibit-read-only t)
	buffer-read-only before-change-function beg-of-line flag)
	
    ;; insert the flag before the difference
    (let ((before (ediff-get-diff-posn buf-type 'beg difference ctl-buffer)))
      (goto-char before)
      (setq beg-of-line (bolp))
      
      (setq flag (ediff-eval-in-buffer
		  ctl-buffer
		  (if beg-of-line
		      (set before-flag-name ediff-before-flag-bol)
		    (set before-flag-name ediff-before-flag-mol))))
	 
      ;; insert the flag itself
      (if (ediff-if-lucid)
	  (ediff-collect-extents-lucid (point)))
      (insert-before-markers flag)
      (if (ediff-if-lucid)
	  ;; Lucid's extent end-points behave strangely; they won't
	  ;; respect insert-before-markers
	  (ediff-adjust-disturbed-extents-lucid (point) 'new-start))
      )
    ;; insert the flag after the difference
    (let* ((after (ediff-get-diff-posn buf-type 'end difference ctl-buffer)))
      (goto-char after)
      (setq beg-of-line (bolp))

      (setq flag (ediff-eval-in-buffer
		  ctl-buffer
		  (if beg-of-line
		      (set after-flag-name ediff-after-flag-bol)
		    (set after-flag-name ediff-after-flag-mol))))

      ;; insert the flag itself
      (if (ediff-if-lucid)
	  (ediff-collect-extents-lucid (point)))
      (insert flag)
      (if (ediff-if-lucid)
	  (ediff-adjust-disturbed-extents-lucid after 'new-end))
      )))

  
(defun ediff-get-diff-posn (buf-type pos &optional n control-buf)
  "Returns positions of difference sectors in the BUF-TYPE buffer.
BUF-TYPE should be a symbol--either `A' or `B'. 
POS is either `beg' or `end'--it specifies whether you want the position at the
beginning of a difference or at the end.

The optional argument N says which difference \(default:
`ediff-current-difference'\).  The optional argument CONTROL-BUF says
which control buffer is in effect in case it is not the current
buffer."
  (let (diff-overlay)
    (or control-buf
	(setq control-buf (current-buffer)))

    (ediff-eval-in-buffer
     control-buf
     (or n  (setq n ediff-current-difference))
     (if (or (< n 0) (>= n ediff-number-of-differences))
	 (if (> ediff-number-of-differences 0)
	     (error "There is no diff %d. Valid diffs are 1 to %d."
		    (1+ n) ediff-number-of-differences)
	   (error "No differences found.")))
     (setq diff-overlay (ediff-get-diff-overlay n buf-type)))
     
    (if (ediff-overlay-get diff-overlay 'detached)
	(ediff-move-overlay diff-overlay
			    (ediff-overlay-get diff-overlay 'ediff-marker)
			    (ediff-overlay-get diff-overlay 'ediff-marker)))
    (if (eq pos 'beg)
	(ediff-overlay-start diff-overlay)
      (ediff-overlay-end diff-overlay))
    ))
    


;; These would highlight differences under X
(defun ediff-highlight-diff (n)
  "Put face on diff N.  Invoked for X displays only."
  (let* ((last-A (ediff-eval-in-buffer ediff-A-buffer (point-max)))
	 (last-B (ediff-eval-in-buffer ediff-B-buffer (point-max)))
	 (begin-A (ediff-get-diff-posn 'A 'beg n))
	 (end-A (ediff-get-diff-posn 'A 'end n))
	 (xtraA (if (equal begin-A end-A) 1 0))
	 (end-A-hilit (min last-A (+ end-A xtraA)))
	 
	 (begin-B (ediff-get-diff-posn 'B 'beg n))
	 (end-B (ediff-get-diff-posn 'B 'end n))
	 (xtraB (if (equal begin-B end-B) 1 0))
	 (end-B-hilit (min last-B (+ end-B xtraB))))
	  
    (if (ediff-if-lucid)
	(progn 
	  (ediff-move-overlay
	   ediff-current-diff-overlay-A begin-A end-A-hilit)
	  (ediff-move-overlay
	   ediff-current-diff-overlay-B begin-B end-B-hilit))
      ;; Emacs 19.22 has a bug, which requires that ediff-move-overlay will
      ;; have the buffer as a parameter.  Believed fixed in 19.23.
      (ediff-move-overlay ediff-current-diff-overlay-A
			  begin-A end-A-hilit ediff-A-buffer)
      (ediff-move-overlay ediff-current-diff-overlay-B
			  begin-B end-B-hilit ediff-B-buffer))
    ;; giving priority of 0 and then changing it may look funny, but
    ;; this is intended to overcome an Emacs bug.
    (ediff-overlay-put ediff-current-diff-overlay-A 'priority  0)
    (ediff-overlay-put ediff-current-diff-overlay-B 'priority  0)
    (ediff-overlay-put ediff-current-diff-overlay-A 'priority  
		 (ediff-highest-priority begin-A end-A-hilit ediff-A-buffer))
    (ediff-overlay-put ediff-current-diff-overlay-B 'priority 
		 (ediff-highest-priority begin-B end-B-hilit ediff-B-buffer))
		 
    (or (face-differs-from-default-p 'ediff-odd-diff-face-A-var)
	(not ediff-highlight-all-diffs)
	(progn
	  (copy-face ediff-odd-diff-face-A 'ediff-odd-diff-face-A-var)
	  (copy-face ediff-odd-diff-face-B 'ediff-odd-diff-face-B-var)
	  (copy-face ediff-even-diff-face-A 'ediff-even-diff-face-A-var)
	  (copy-face ediff-even-diff-face-B 'ediff-even-diff-face-B-var)))
	  
    ;; unhighlight the background overlay for the diff n so they won't
    ;; interfere with the current diff overlay
    (ediff-overlay-put (ediff-get-diff-overlay n 'A) 'face nil)
    (ediff-overlay-put (ediff-get-diff-overlay n 'B) 'face nil)
    
    ;; (sit-for 0) ;; needed synch for some reason in v19.22
    ))


(defun ediff-unhighlight-diff ()
  "Remove overlays from buffers A and B."
    
  (ediff-move-overlay ediff-current-diff-overlay-A 1 1)
  (ediff-move-overlay ediff-current-diff-overlay-B 1 1)
  
  ;; rehighlight the overlay in the background of the
  ;; current difference region
  (let ((overlay-A (ediff-get-diff-overlay ediff-current-difference 'A))
	(overlay-B (ediff-get-diff-overlay ediff-current-difference 'B)))
    (ediff-overlay-put overlay-A
		       'face (if (ediff-odd-p ediff-current-difference)
				 'ediff-odd-diff-face-A-var
			       'ediff-even-diff-face-A-var))
    (ediff-overlay-put overlay-B
		       'face (if (ediff-odd-p ediff-current-difference)
				 'ediff-odd-diff-face-B-var
			       'ediff-even-diff-face-B-var))
  ))


;; delete highlighting overlays, restore faces to their original form
(defun ediff-unhighlight-diffs-totally ()
  (let (buffer-read-only)
    (ediff-unselect-and-select-difference -1)
    
    (if (and window-system ediff-want-faces)
	(let ((inhibit-quit t))
	  (if (face-differs-from-default-p 'ediff-odd-diff-face-A-var)
	      (progn
		(copy-face 'default 'ediff-odd-diff-face-A-var)
		(copy-face 'default 'ediff-odd-diff-face-B-var)
		(copy-face 'default 'ediff-even-diff-face-A-var)
		(copy-face 'default 'ediff-even-diff-face-B-var)))
	  (if (ediff-overlayp ediff-current-diff-overlay-A)
	      (ediff-delete-overlay ediff-current-diff-overlay-A))
	  (setq ediff-current-diff-overlay-A nil)
	  (if (ediff-overlayp ediff-current-diff-overlay-B)
	      (ediff-delete-overlay ediff-current-diff-overlay-B))
	  (setq ediff-current-diff-overlay-B nil)))
    ))
    
(defun ediff-clear-diff-vector (vec &optional fin-diffs-also)
  ;; null out the difference overlays so they won't slow down future
  ;; editing operations
  (mapcar (function
	   (lambda (elt)
	     (ediff-delete-overlay (ediff-get-diff-overlay-from-vector elt 'A))
	     (ediff-delete-overlay (ediff-get-diff-overlay-from-vector elt 'B))
	     (if fin-diffs-also
		 (ediff-clear-diff-vector 
		  (ediff-get-fine-diff-vector-from-vec elt)))
	     ))
	  vec)
  ;; allow them to be garbage collected
  (setq vec nil))
	  
(defun ediff-operate-on-flags (action)
  "Re/unhighlights buffers A and B with all flags from all Ediff sessions.
This is usually needed only when a
buffer is involved in multiple Ediff sessions."
  (let* ((A-sessions (ediff-eval-in-buffer
		      ediff-A-buffer
		      ediff-this-buffer-control-sessions))
	 (B-sessions (ediff-eval-in-buffer
		      ediff-B-buffer
		      ediff-this-buffer-control-sessions))
	 (sessions (ediff-union A-sessions B-sessions))
	 (flag (if (eq action 'remove) 'unselect-only 'select-only)))
	 
    (mapcar (function (lambda (buf)
			(ediff-eval-in-buffer
			 buf
			 (or (if (eq action 'insert)
				 (memq ediff-highlighting-style '(ascii off))
			       (not (eq ediff-highlighting-style 'ascii)))
			     (ediff-unselect-and-select-difference
			      ediff-current-difference 
			      flag 'no-recenter))
			 )))
	    sessions)))



;;; Refinement of current diff	    
;; Split region along word boundaries. Each word will be on its own line.
;; Output to buffer out-buffer.
(defun ediff-forward-word ()
  "Move point one word forward. Used for splitting diff regions into words.
This is the default for `ediff-forward-word-function'."
  (or (> (skip-chars-forward ediff-word-1) 0)
      (> (skip-chars-forward ediff-word-2) 0)))

(defun ediff-wordify (beg end in-buffer out-buffer)
  (let (sv-point string)
    (save-excursion
     (set-buffer in-buffer)
     (setq string (buffer-substring beg end))

     (set-buffer out-buffer)
     (erase-buffer)
     (insert string)
     (goto-char (point-min))
     (skip-chars-forward ediff-whitespace)
     (delete-region (point-min) (point))
     
     (while (not (eobp))
       (funcall ediff-forward-word-function)
       (setq sv-point (point))
       (skip-chars-forward ediff-whitespace)
       (delete-region sv-point (point))
       (insert "\n")))))

;; `n' is the diff region to work on. 
;; if `flag' is 'noforce then make fine-diffs only if this region's fine
;; diffs have not been computed before.
;; if `flag' is 'skip then don't compute fine diffs for this region.
(defun ediff-make-fine-diffs (&optional n flag)       
  (interactive)
  (or n  (setq n ediff-current-difference))
  
  (if (< ediff-number-of-differences 1)
      (error "No differences found."))
  
  (or (< n 0)
      (>= n ediff-number-of-differences)
      ;; n is within the range
      (let ((file-A ediff-temp-file-A)
	(file-B ediff-temp-file-B))
	
	(cond ((and (eq flag 'noforce) (ediff-get-fine-diff-vector n))
	       nil)
	      ((eq flag 'skip)
	       (or (ediff-get-fine-diff-vector n)
		   (eq ediff-auto-refine 'off)
		   (message "Region %d is larger than auto-refine limit. Hit %S to force-refine."
			    (1+ n)
			    (substitute-command-keys
			     "\\[ediff-make-fine-diffs]")
			    )))
	      (t
	       ;; delete old fine diffs
	       (ediff-clear-diff-vector (ediff-get-fine-diff-vector n))
	       ;; recompute fine diffs
	       (setq ediff-tmp-buffer (get-buffer-create "*ediff-tmp*"))
	       
	       (ediff-wordify
		(ediff-get-diff-posn 'A 'beg n)
		(ediff-get-diff-posn 'A 'end n)
		ediff-A-buffer
		ediff-tmp-buffer)
	       (ediff-eval-in-buffer
		ediff-tmp-buffer
		(setq file-A (ediff-make-temp-file ".fine-diffs-A" file-A)))
	       
	       (ediff-wordify
		(ediff-get-diff-posn 'B 'beg n)
		(ediff-get-diff-posn 'B 'end n)
		ediff-B-buffer
		ediff-tmp-buffer)
	       (ediff-eval-in-buffer
		ediff-tmp-buffer
		(setq file-B (ediff-make-temp-file ".fine-diffs-B" file-B)))
	       
	       ;; save temp file names.
	       (setq ediff-temp-file-A file-A
		     ediff-temp-file-B file-B)
	       
	       ;; set the new vector of fine diffs, if none exists
	       (ediff-set-fine-diff-vector
		n
		(ediff-setup-diff-regions file-A file-B 'use-old-diff-buf n
					  ediff-fine-diff-program
					  ediff-fine-diff-options
					  ediff-fine-diff-ok-lines-regexp))
	       (if (eq (length (ediff-get-fine-diff-vector n)) 0)
		   (progn
		     (message "No diffs found in region %d, except for white space and line breaks."
			      (1+ n))
		     (ediff-mark-diff-as-space-only n t))
		 (ediff-mark-diff-as-space-only n nil)))
	      ) ;; end cond
	(ediff-set-fine-diff-properties n)
	)))
    
    
(defun ediff-set-fine-diff-properties (n &optional default)
  (or (not window-system)
      (< n 0)
      (>= n ediff-number-of-differences)
      ;; in a window system, set faces and priorities of fine overlays
      (let ((fine-diff-vector  (ediff-get-fine-diff-vector n))
	    (face-A (if default 'default (face-name ediff-fine-diff-face-A)))
	    (face-B (if default 'default (face-name ediff-fine-diff-face-B)))
	    (priority-A (if default
			    0
			  (1+ (ediff-overlay-get ediff-current-diff-overlay-A
						 'priority))))
	    (priority-B (if default
			    0
			  (1+ (ediff-overlay-get ediff-current-diff-overlay-B
						 'priority)))))
	(mapcar
	 (function (lambda (vec)
		     (ediff-overlay-put 
		      (ediff-get-diff-overlay-from-vector vec 'A)
		      'face face-A)
		     (ediff-overlay-put
		      (ediff-get-diff-overlay-from-vector vec 'A)
		      'priority priority-A)
		     
		     (ediff-overlay-put
		      (ediff-get-diff-overlay-from-vector vec 'B)
		      'face face-B)
		     (ediff-overlay-put
		      (ediff-get-diff-overlay-from-vector vec 'B)
		      'priority priority-B)
		     ))
	 fine-diff-vector)
	)))
    
(defun ediff-convert-diffs-to-overlays-refine (A-buffer B-buffer
						diff-list refine-region)
  (let* ((current-diff -1)
	 (reg-A-start (ediff-get-diff-posn 'A 'beg refine-region))
	 (reg-B-start (ediff-get-diff-posn 'B 'beg refine-region))
	 diff-overlay-list list-element
	 a-begin a-end b-begin b-end
	 a-overlay b-overlay)

    (ediff-eval-in-buffer A-buffer (goto-char reg-A-start))
    (ediff-eval-in-buffer B-buffer (goto-char reg-B-start))
     
    (while diff-list
      (setq current-diff (1+ current-diff)
	    list-element (car diff-list)
	    a-begin 	 (aref list-element 0)
	    a-end 	 (aref list-element 1)
	    b-begin 	 (aref list-element 2)
	    b-end 	 (aref list-element 3))
	    
      ;; put overlays at appropriate places in buffers
      (setq a-overlay (ediff-make-overlay 
		       (ediff-goto-word (1+ a-begin) A-buffer)
		       (ediff-goto-word a-end A-buffer 'end)
		       A-buffer))
			 
    (setq b-overlay (ediff-make-overlay 
		     (ediff-goto-word (1+ b-begin) B-buffer)
		     (ediff-goto-word b-end B-buffer 'end)
		     B-buffer))
			 
      ;; record all overlays for this difference
      (setq diff-overlay-list (nconc diff-overlay-list
				     (list (vector a-overlay b-overlay)))
	    diff-list (cdr diff-list))
      ) ;; while
    ;; convert the list of difference information into a vector for
    ;; fast access
    (apply 'vector diff-overlay-list)))

;; goto word #n starting at current position in buffer `buf'
;; For ediff, a word is either a string of a-z,A-Z, incl `-' and `_';
;; or a string of other non-blanks. A blank is a \n\t\C-j
;; If `flag' is non-nil, goto the end of the n-th word.
(defun ediff-goto-word (n buf &optional flag)
  (ediff-eval-in-buffer
   buf
   (skip-chars-forward ediff-whitespace)
   (while (> n 1)
     (funcall ediff-forward-word-function)
     (skip-chars-forward ediff-whitespace)
     (setq n (1- n)))
   ;(if flag
   (if (and flag (> n 0))
       (funcall ediff-forward-word-function))
   (point)))
   
(defun ediff-get-visible-buffer-window (wind)
  (if (ediff-if-lucid)
      (get-buffer-window wind t)
    (get-buffer-window wind 'visible)))

  
       
       

;;; Misc

;; These two functions are here to neutralize Lemacs' unwillingless to
;; handle overlays whose buffers have been deleted.
(defun ediff-move-overlay (overlay beg end &optional buffer)
  "Calls `move-overlay' in Emacs and `set-extent-endpoints' in Lemacs.
Checks if overlay's buffer exists before actually doing the move."
  (let ((buf (ediff-overlay-buffer overlay)))
    (if (ediff-buffer-live-p buf)
	(if (ediff-if-lucid)
	    (set-extent-endpoints overlay beg end)
	  (move-overlay overlay beg end buffer))
      (ediff-delete-overlay overlay))))
	  
(defun ediff-overlay-put (overlay prop value)
  "Calls `overlay-put' or `set-extent-property' depending on Emacs version.
Checks if overlay's buffer exists."
  (if (ediff-buffer-live-p (ediff-overlay-buffer overlay))
      (if (ediff-if-lucid)
	  (set-extent-property overlay prop value)
	(overlay-put overlay prop value))
    (ediff-delete-overlay overlay)))
    

;; In Emacs 19.23 and Lucid 19.10, the number of variables to
;; file-name-handler has changed.
(defun ediff-find-file-name-handler (file)
  (let (newvers)
    (setq newvers
	  (cond ((and (boundp 'emacs-major-version)
		      (> emacs-major-version 19))
		 t)
		((boundp 'emacs-minor-version)
		 (if (ediff-if-lucid)
		     (> emacs-minor-version 9)
		   (> emacs-minor-version 22)))
		(t nil)))
    (if newvers
	(find-file-name-handler file 'find-file-noselect)
      (find-file-name-handler file))))
		 
		
  

(defun ediff-submit-report ()
  "Submit bug report on Ediff."
  (interactive)
  (let ((reporter-prompt-for-summary-p t)
	varlist salutation)
    (setq varlist '(ediff-diff-program ediff-diff-options
		    ediff-fine-diff-program ediff-fine-diff-options
		    ediff-patch-program ediff-patch-options
		    ediff-shell
		    ediff-want-faces ediff-want-default-menus
		    ediff-auto-refine ediff-highlighting-style
		    ediff-A-buffer ediff-B-buffer ediff-control-buffer
		    ediff-forward-word-function))
    (setq salutation "
Congratulations! You are about to report a bug in Ediff!

Please make a concise, accurate summary of what happened
and mail it to the address above.

Some ``bugs'' may actually not be bugs at all. For instance, if you are
reporting that certain difference regions are not matched as you think they
should, this is most likely due to the way Unix diff program decides what
constitutes a difference region. Ediff is an Emacs interface to diff, and
it has nothing to do with those decisions---it only takes the output from
diff and presents it in a way that is better suited for human browsing and
manipulation.

Another popular topic for reports are ``error messages'' arising from
byte-compilation. Because Ediff interfaces to several other packages and
runs under Emacs and Lucid Emacs, byte-compilation may produce output like
this:
       While compiling toplevel forms in file ediff.el:
	 ** reference to free variable pm-color-alist
	   ........................
       While compiling the end of the data:
	 ** The following functions are not known to be defined: 
	   ediff-valid-color-p, ediff-display-color-p, ediff-set-face,
	   ........................

These are NOT errors, but inevitable warnings that should be ignored.

So, please don't report those and similar things.  However, if all you wanted
is to tell us how much you liked Ediff, go ahead and send this message anyway.

------------------------------------------------------------------")

    (require 'reporter)
    
    (reporter-submit-bug-report "[email protected]"
				(ediff-version)
				varlist
				nil nil
				salutation)
    ))
			     
       
(defun ediff-union (list1 list2)
  "Combine LIST1 and LIST2 using a set-union operation.
The result list contains all items that appear in either LIST1 or LIST2.
This is a non-destructive function; it makes a copy of the data if necessary
to avoid corrupting the original LIST1 and LIST2.
This is a slightly simplified version from `cl-seq.el'.  Added here to
avoid loading cl-*."
  (cond ((null list1) list2) ((null list2) list1)
	((equal list1 list2) list1)
	(t
	 (or (>= (length list1) (length list2))
	     (setq list1 (prog1 list2 (setq list2 list1))))
	 (while list2
	   (or (memq (car list2) list1)
	       (setq list1 (cons (car list2) list1)))
	   (setq list2 (cdr list2)))
	 list1)))

;(defun ediff-debug ()
;  (interactive)
;  (with-output-to-temp-buffer "*ediff-debug*"
;    (princ 
;     (format "Ctl buffer: %S\n\nediff-difference-vector:\n"
;	     ediff-control-buffer))
;    (mapcar (function
;	     (lambda (overl-vec)
;	       (princ (format "Diff %d:  %S %S %S\n\t %S %S %S\n" 
;			      (1+ (ediff-overlay-get (aref overl-vec 0)
;						     'ediff-diff-num))
;			      (ediff-overlay-get (aref overl-vec 0)
;						 'ediff-control-buffer) 
;			      (ediff-overlay-get (aref overl-vec 0)
;						 'insert-in-front-hooks)
;			      (aref overl-vec 0)
;			      (ediff-overlay-get (aref overl-vec 1)
;						 'ediff-control-buffer) 
;			      (ediff-overlay-get (aref overl-vec 0)
;						 'insert-in-front-hooks)
;			      (aref overl-vec 1)
;			      ))))
;	    ediff-difference-vector)
;    (princ "\nediff-disturbed-overlays:\n")
;    (mapcar (function
;	     (lambda (overl)
;	       (princ (format "%S  %S\n"
;			      (ediff-overlay-get overl 'ediff-control-buffer)
;			      overl
;			      ))))
;	    ediff-disturbed-overlays)))

  
(run-hooks 'ediff-load-hooks)
  

(provide 'ediff)

;;; ediff.el ends here