Add that PBM and XBM image specs may have :foreground nil, and

[emacs.git] / lisp / progmodes / hideshow.el

;;; hideshow.el --- minor mode cmds to selectively display blocks of code

;; Copyright (C) 1994, 95, 96, 97, 98, 99, 2000, 01 Free Software Foundation

;; Author: Thien-Thi Nguyen <ttn@gnu.org>
;;      Dan Nicolaescu <dann@ics.uci.edu>
;; Keywords: C C++ java lisp tools editing comments blocks hiding outlines
;; Maintainer-Version: 5.26
;; Time-of-Day-Author-Most-Likely-to-be-Recalcitrant: early morning

;; 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, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:

;; * Commands provided
;;
;; This file provides Hideshow Minor Mode.  When active, nine commands
;; are available, implementing block hiding and showing.  They (and their
;; keybindings) are:
;;
;;   hs-hide-block                      C-c @ C-h
;;   hs-show-block                      C-c @ C-s
;;   hs-hide-all                        C-c @ C-M-h
;;   hs-show-all                        C-c @ C-M-s
;;   hs-hide-level                      C-c @ C-l
;;   hs-toggle-hiding                   C-c @ C-c
;;   hs-mouse-toggle-hiding             [(shift button-2)]
;;   hs-hide-initial-comment-block
;;
;; Blocks are defined per mode.  In c-mode, c++-mode and java-mode, they
;; are simply text between curly braces, while in Lisp-ish modes parens
;; are used.  Multi-line comment blocks can also be hidden.  Read-only
;; buffers are not a problem, since hideshow doesn't modify the text.
;;
;; The command `M-x hs-minor-mode' toggles the minor mode or sets it
;; (similar to other minor modes).

;; * Customization
;;
;; You can use `M-x customize-variable' on the following variables:
;;
;; - hs-hide-comments-when-hiding-all -- self-explanatory!
;; - hs-hide-all-non-comment-function -- if non-nil, when doing a
;;                                       `hs-hide-all', this function
;;                                       is called w/ no arguments
;; - hs-isearch-open                  -- what kind of hidden blocks to
;;                                       open when doing isearch
;;
;; Some languages (e.g., Java) are deeply nested, so the normal behavior
;; of `hs-hide-all' (hiding all but top-level blocks) results in very
;; little information shown, which is not very useful.  You can use the
;; variable `hs-hide-all-non-comment-function' to implement your idea of
;; what is more useful.  For example, the following code shows the next
;; nested level in addition to the top-level:
;;
;;   (defun ttn-hs-hide-level-1 ()
;;     (hs-hide-level 1)
;;     (forward-sexp 1))
;;   (setq hs-hide-all-non-comment-function 'ttn-hs-hide-level-1)
;;
;; Hideshow works w/ incremental search (isearch) by setting the variable
;; `hs-headline', which is the line of text at the beginning of a hidden
;; block that contains a match for the search.  You can have this show up
;; in the mode line by modifying the variable `mode-line-format'.  For
;; example, the following code prepends this info to the mode line:
;;
;;   (unless (memq 'hs-headline mode-line-format)
;;     (setq mode-line-format
;;           (append '("-" hs-headline) mode-line-format)))
;;
;; See documentation for `mode-line-format' for more info.
;;
;; Hooks are run after some commands:
;;
;;   hs-hide-hook     in      hs-hide-block, hs-hide-all, hs-hide-level
;;   hs-show-hook             hs-show-block, hs-show-all
;;
;; One of `hs-hide-hook' or `hs-show-hook' is run for the toggling
;; commands when the result of the toggle is to hide or show blocks,
;; respectively.  All hooks are run w/ `run-hooks'.  See docs for each
;; variable or hook for more info.
;;
;; Normally, hideshow tries to determine appropriate values for block
;; and comment definitions by examining the buffer's major mode.  If
;; there are problems, hideshow will not activate and in that case you
;; may wish to override hideshow's heuristics by adding an entry to
;; variable `hs-special-modes-alist'.  Packages that use hideshow should
;; do something like:
;;
;;   (let ((my-mode-hs-info '(my-mode "{{" "}}" ...)))
;;     (if (not (member my-mode-hs-info hs-special-modes-alist))
;;         (setq hs-special-modes-alist
;;               (cons my-mode-hs-info hs-special-modes-alist))))
;;
;; If you have an entry that works particularly well, consider
;; submitting it for inclusion in hideshow.el.  See docstring for
;; `hs-special-modes-alist' for more info on the entry format.

;; * Suggested usage
;;
;; First make sure hideshow.el is in a directory in your `load-path'.
;; You can optionally byte-compile it using `M-x byte-compile-file'.
;; Then, add the following to your ~/.emacs:
;;
;; (load-library "hideshow")
;; (add-hook 'X-mode-hook               ; other modes similarly
;;           '(lambda () (hs-minor-mode 1)))
;;
;; where X = {emacs-lisp,c,c++,perl,...}.  You can also manually toggle
;; hideshow minor mode by typing `M-x hs-minor-mode'.  After hideshow is
;; activated or deactivated, `hs-minor-mode-hook' is run w/ `run-hooks'.

;; * Bugs
;;
;; (1) Hideshow does not work w/ emacs 18 because emacs 18 lacks the
;;     function `forward-comment' (among other things).  If someone
;;     writes this, please send me a copy.
;;
;; (2) Sometimes `hs-headline' can become out of sync.  To reset, type
;;     `M-x hs-minor-mode' twice (that is, deactivate then activate
;;     hideshow).
;;
;; (3) Hideshow 5.x is developed and tested on GNU Emacs 20.4.
;;     XEmacs compatibility may have bitrotted since 4.29.
;;
;; (4) Some buffers can't be `byte-compile-file'd properly.  This is because
;;     `byte-compile-file' inserts the file to be compiled in a temporary
;;     buffer and switches `normal-mode' on.  In the case where you have
;;     `hs-hide-initial-comment-block' in `hs-minor-mode-hook', the hiding of
;;     the initial comment sometimes hides parts of the first statement (seems
;;     to be only in `normal-mode'), so there are unbalanced "(" and ")".
;;
;;     The workaround is to clear `hs-minor-mode-hook' when byte-compiling:
;;
;;     (defadvice byte-compile-file (around
;;                                   byte-compile-file-hideshow-off
;;                                   act)
;;       (let ((hs-minor-mode-hook nil))
;;         ad-do-it))

;; Correspondance welcome; please indicate version number.  Send bug
;; reports and inquiries to <ttn@gnu.org>.

;; * Thanks
;;
;; Thanks go to the following people for valuable ideas, code and
;; bug reports.
;;
;;     Dean Andrews, Alf-Ivar Holm, Holger Bauer, Christoph Conrad, Dave
;;     Love, Dirk Herrmann, Gael Marziou, Jan Djarv, Guillaume Leray,
;;     Moody Ahmad, Preston F. Crow, Lars Lindberg, Reto Zimmermann,
;;     Keith Sheffield, Chew Meng Kuan, Tony Lam, Pete Ware, François Pinard
;;
;; Special thanks go to Dan Nicolaescu, who reimplemented hideshow using
;; overlays (rather than selective display), added isearch magic, folded
;; in custom.el compatibility, generalized comment handling, incorporated
;; mouse support, and maintained the code in general.  Version 4.0 is
;; largely due to his efforts.

;; * History
;;
;; Hideshow was inspired when I learned about selective display.  It was
;; reimplemented to use overlays for 4.0 (see above).  WRT older history,
;; entries in the masterfile corresponding to versions 1.x and 2.x have
;; been lost.  XEmacs support is reliable as of 4.29.  State save and
;; restore was added in 3.5 (not widely distributed), and reliable as of
;; 4.30.  Otherwise, the code seems stable.  Passes checkdoc as of 4.32.
;; Version 5.x uses new algorithms for block selection and traversal,
;; unbundles state save and restore, and includes more isearch support.

;;; Code:

(require 'easymenu)

;;---------------------------------------------------------------------------
;; user-configurable variables

(defgroup hideshow nil
  "Minor mode for hiding and showing program and comment blocks."
  :prefix "hs-"
  :group 'languages)

;;;###autoload
(defcustom hs-hide-comments-when-hiding-all t
  "*Hide the comments too when you do an `hs-hide-all'."
  :type 'boolean
  :group 'hideshow)

(defcustom hs-minor-mode-hook nil
  "*Hook called when hideshow minor mode is activated or deactivated."
  :type 'hook
  :group 'hideshow
  :version "21.1")

(defcustom hs-isearch-open 'block
  "*What kind of hidden blocks to open when doing `isearch'.
One of the following symbols:

  block   -- open only blocks
  comment -- open only comments
  t       -- open both blocks and comments
  nil     -- open neither blocks nor comments

This has effect iff `search-invisible' is set to `open'."
  :type '(choice (const :tag "open only blocks" block)
                 (const :tag "open only comments" comment)
                 (const :tag "open both blocks and comments" t)
                 (const :tag "don't open any of them" nil))
  :group 'hideshow)

;;;###autoload
(defvar hs-special-modes-alist
  '((c-mode "{" "}" "/[*/]" nil hs-c-like-adjust-block-beginning)
    (c++-mode "{" "}" "/[*/]" nil hs-c-like-adjust-block-beginning)
    (bibtex-mode ("^@\\S(*\\(\\s(\\)" 1))
    (java-mode "{" "}" "/[*/]" nil hs-c-like-adjust-block-beginning)
    )
  "*Alist for initializing the hideshow variables for different modes.
Each element has the form
  (MODE START END COMMENT-START FORWARD-SEXP-FUNC ADJUST-BEG-FUNC).

If non-nil, hideshow will use these values as regexps to define blocks
and comments, respectively for major mode MODE.

START, END and COMMENT-START are regular expressions.  A block is
defined as text surrounded by START and END.

As a special case, START may be a list of the form (COMPLEX-START
MDATA-SELECTOR), where COMPLEX-START is a regexp w/ multiple parts and
MDATA-SELECTOR an integer that specifies which sub-match is the proper
place to adjust point, before calling `hs-forward-sexp-func'.  For
example, see the `hs-special-modes-alist' entry for `bibtex-mode'.

For some major modes, `forward-sexp' does not work properly.  In those
cases, FORWARD-SEXP-FUNC specifies another function to use instead.

See the documentation for `hs-adjust-block-beginning' to see what is the
use of ADJUST-BEG-FUNC.

If any of the elements is left nil or omitted, hideshow tries to guess
appropriate values.  The regexps should not contain leading or trailing
whitespace.  Case does not matter.")

(defvar hs-hide-all-non-comment-function nil
  "*Function called if non-nil when doing `hs-hide-all' for non-comments.")

(defvar hs-hide-hook nil
  "*Hook called (with `run-hooks') at the end of commands to hide text.
These commands include the toggling commands (when the result is to hide
a block), `hs-hide-all', `hs-hide-block' and `hs-hide-level'.")

(defvar hs-show-hook nil
  "*Hook called (with `run-hooks') at the end of commands to show text.
These commands include the toggling commands (when the result is to show
a block), `hs-show-all' and `hs-show-block'..")

;;---------------------------------------------------------------------------
;; internal variables

(defvar hs-minor-mode nil
  "Non-nil if using hideshow mode as a minor mode of some other mode.
Use the command `hs-minor-mode' to toggle or set this variable.")

(defvar hs-minor-mode-map nil
  "Keymap for hideshow minor mode.")

(defvar hs-minor-mode-menu nil
  "Menu for hideshow minor mode.")

(defvar hs-c-start-regexp nil
  "Regexp for beginning of comments.
Differs from mode-specific comment regexps in that
surrounding whitespace is stripped.")

(defvar hs-block-start-regexp nil
  "Regexp for beginning of block.")

(defvar hs-block-start-mdata-select nil
  "Element in `hs-block-start-regexp' match data to consider as block start.
The internal function `hs-forward-sexp' moves point to the beginning of this
element (using `match-beginning') before calling `hs-forward-sexp-func'.")

(defvar hs-block-end-regexp nil
  "Regexp for end of block.")

(defvar hs-forward-sexp-func 'forward-sexp
  "Function used to do a `forward-sexp'.
Should change for Algol-ish modes.  For single-character block
delimiters -- ie, the syntax table regexp for the character is
either `(' or `)' -- `hs-forward-sexp-func' would just be
`forward-sexp'.  For other modes such as simula, a more specialized
function is necessary.")

(defvar hs-adjust-block-beginning nil
  "Function used to tweak the block beginning.
The block is hidden from the position returned by this function,
as opposed to hiding it from the position returned when searching
for `hs-block-start-regexp'.

For example, in c-like modes, if we wish to also hide the curly braces
(if you think they occupy too much space on the screen), this function
should return the starting point (at the end of line) of the hidden
region.

It is called with a single argument ARG which is the the position in
buffer after the block beginning.

It should return the position from where we should start hiding.

It should not move the point.

See `hs-c-like-adjust-block-beginning' for an example of using this.")

(defvar hs-headline nil
  "Text of the line where a hidden block begins, set during isearch.
You can display this in the mode line by adding the symbol `hs-headline'
to the variable `mode-line-format'.  For example,

  (unless (memq 'hs-headline mode-line-format)
    (setq mode-line-format
          (append '(\"-\" hs-headline) mode-line-format)))

Note that `mode-line-format' is buffer-local.")

;;---------------------------------------------------------------------------
;; system dependency

; ;; xemacs compatibility
; (when (string-match "xemacs\\|lucid" emacs-version)
;   ;; use pre-packaged compatiblity layer
;   (require 'overlay))
;
; ;; xemacs and emacs-19 compatibility
; (when (or (not (fboundp 'add-to-invisibility-spec))
;           (not (fboundp 'remove-from-invisibility-spec)))
;   ;; `buffer-invisibility-spec' mutators snarfed from Emacs 20.3 lisp/subr.el
;   (defun add-to-invisibility-spec (arg)
;     (cond
;      ((or (null buffer-invisibility-spec) (eq buffer-invisibility-spec t))
;       (setq buffer-invisibility-spec (list arg)))
;      (t
;       (setq buffer-invisibility-spec
;             (cons arg buffer-invisibility-spec)))))
;   (defun remove-from-invisibility-spec (arg)
;     (if buffer-invisibility-spec
;         (setq buffer-invisibility-spec
;               (delete arg buffer-invisibility-spec)))))

;; hs-match-data
(defalias 'hs-match-data 'match-data)

;;---------------------------------------------------------------------------
;; support functions

(defun hs-discard-overlays (from to)
  "Delete hideshow overlays in region defined by FROM and TO."
  (when (< to from)
    (setq from (prog1 to (setq to from))))
  (let ((ovs (overlays-in from to)))
    (while ovs
      (let ((ov (car ovs)))
        (when (overlay-get ov 'hs)
          (delete-overlay ov)))
      (setq ovs (cdr ovs)))))

(defun hs-isearch-show (ov)
  "Delete overlay OV, and set `hs-headline' to nil.

This function is meant to be used as the `isearch-open-invisible'
property of an overlay."
  (setq hs-headline nil)
  (delete-overlay ov))

(defun hs-isearch-show-temporary (ov hide-p)
  "Hide or show overlay OV, and set `hs-headline', all depending on HIDE-P.
If HIDE-P is non-nil, `hs-headline' is set to nil and overlay OV is hidden.
Otherwise, `hs-headline' is set to the line of text at the head of OV, and
OV is shown.

This function is meant to be used as the `isearch-open-invisible-temporary'
property of an overlay."
  (setq hs-headline
        (if hide-p
            nil
          (or hs-headline
              (let ((start (overlay-start ov)))
                (buffer-substring
                 (save-excursion (goto-char start)
                                 (beginning-of-line)
                                 (skip-chars-forward " \t")
                                 (point))
                 start)))))
  (force-mode-line-update)
  (overlay-put ov 'invisible (and hide-p 'hs)))

(defun hs-flag-region (from to flag)
  "Hide or show lines from FROM to TO, according to FLAG.
If FLAG is nil then text is shown, while if FLAG is non-nil the text is
hidden.  Actually flag is really either `comment' or `block' depending
on what kind of block it is supposed to hide."
  (save-excursion
    ;; first clear it all out
    (hs-discard-overlays from to)
    ;; now create overlays if needed
    (when flag
      (let ((overlay (make-overlay from to)))
        (overlay-put overlay 'invisible 'hs)
        (overlay-put overlay 'hs flag)
        (when (or (eq hs-isearch-open t) (eq hs-isearch-open flag))
          (overlay-put overlay 'isearch-open-invisible 'hs-isearch-show)
          (overlay-put overlay
                       'isearch-open-invisible-temporary
                       'hs-isearch-show-temporary))
        overlay))))

(defun hs-forward-sexp (match-data arg)
  "Adjust point based on MATCH-DATA and call `hs-forward-sexp-func' w/ ARG.
Original match data is restored upon return."
  (save-match-data
    (set-match-data match-data)
    (goto-char (match-beginning hs-block-start-mdata-select))
    (funcall hs-forward-sexp-func arg)))

(defun hs-hide-comment-region (beg end &optional repos-end)
  "Hide a region from BEG to END, marking it as a comment.
Optional arg REPOS-END means reposition at end."
  (hs-flag-region (progn (goto-char beg) (end-of-line) (point))
                  (progn (goto-char end) (end-of-line) (point))
                  'comment)
  (goto-char (if repos-end end beg)))

(defun hs-hide-block-at-point (&optional end comment-reg)
  "Hide block iff on block beginning.
Optional arg END means reposition at end.
Optional arg COMMENT-REG is a list of the form (BEGIN END) and
specifies the limits of the comment, or nil if the block is not
a comment.

The block beginning is adjusted by `hs-adjust-block-beginning'
and then further adjusted to be at the end of the line."
  (if comment-reg
      (hs-hide-comment-region (car comment-reg) (cadr comment-reg) end)
    (if (looking-at hs-block-start-regexp)
        (let* ((mdata (hs-match-data t))
               (pure-p (match-end 0))
               (p
                ;; `p' is the point at the end of the block beginning,
                ;; which may need to be adjusted
                (save-excursion
                  (goto-char (funcall (or hs-adjust-block-beginning
                                          'identity)
                                      pure-p))
                  ;; whatever the adjustment, we move to eol
                  (end-of-line)
                  (point)))
               (q
                ;; `q' is the point at the end of the block
                (progn (hs-forward-sexp mdata 1)
                       (end-of-line)
                       (point))))
          (if (and (< p (point)) (> (count-lines p q) 1))
              (overlay-put (hs-flag-region p q 'block)
                           'hs-ofs
                           (- pure-p p)))
          (goto-char (if end q (min p pure-p)))))))

(defun hs-safety-is-job-n ()
  "Warn if `buffer-invisibility-spec' does not contain symbol `hs'."
    (unless (and (listp buffer-invisibility-spec)
                 (assq 'hs buffer-invisibility-spec))
      (message "Warning: `buffer-invisibility-spec' does not contain hs!!")
      (sit-for 2)))

(defun hs-inside-comment-p ()
  "Return non-nil if point is inside a comment, otherwise nil.
Actually, return a list containing the buffer position of the start
and the end of the comment.  A comment block can be hidden only if on
its starting line there is only whitespace preceding the actual comment
beginning.  If we are inside of a comment but this condition is not met,
we return a list having a nil as its car and the end of comment position
as cdr."
  (save-excursion
    ;; the idea is to look backwards for a comment start regexp, do a
    ;; forward comment, and see if we are inside, then extend extend
    ;; forward and backward as long as we have comments
    (let ((q (point)))
      (when (or (looking-at hs-c-start-regexp)
                (re-search-backward hs-c-start-regexp (point-min) t))
        (forward-comment (- (buffer-size)))
        (skip-chars-forward " \t\n\f")
        (let ((p (point))
              (not-hidable nil))
          (beginning-of-line)
          (unless (looking-at (concat "[ \t]*" hs-c-start-regexp))
            ;; we are in this situation: (example)
            ;; (defun bar ()
            ;;      (foo)
            ;;                ) ; comment
            ;;                 ^
            ;;   the point was here before doing (beginning-of-line)
            ;; here we should advance till the next comment which
            ;; eventually has only white spaces preceding it on the same
            ;; line
            (goto-char p)
            (forward-comment 1)
            (skip-chars-forward " \t\n\f")
            (setq p (point))
            (while (and (< (point) q)
                        (> (point) p)
                        (not (looking-at hs-c-start-regexp)))
              (setq p (point));; use this to avoid an infinite cycle
              (forward-comment 1)
              (skip-chars-forward " \t\n\f"))
            (if (or (not (looking-at hs-c-start-regexp))
                    (> (point) q))
                ;; we cannot hide this comment block
                (setq not-hidable t)))
          ;; goto the end of the comment
          (forward-comment (buffer-size))
          (skip-chars-backward " \t\n\f")
          (end-of-line)
          (if (>= (point) q)
              (list (if not-hidable nil p) (point))))))))

(defun hs-grok-mode-type ()
  "Set up hideshow variables for new buffers.
If `hs-special-modes-alist' has information associated with the
current buffer's major mode, use that.
Otherwise, guess start, end and `comment-start' regexps; `forward-sexp'
function; and adjust-block-beginning function."
  (if (and (boundp 'comment-start)
           (boundp 'comment-end)
           comment-start comment-end)
      (let* ((lookup (assoc major-mode hs-special-modes-alist))
             (start-elem (or (nth 1 lookup) "\\s(")))
        (if (listp start-elem)
            ;; handle (START-REGEXP MDATA-SELECT)
            (setq hs-block-start-regexp (car start-elem)
                  hs-block-start-mdata-select (cadr start-elem))
          ;; backwards compatibility: handle simple START-REGEXP
          (setq hs-block-start-regexp start-elem
                hs-block-start-mdata-select 0))
        (setq hs-block-end-regexp (or (nth 2 lookup) "\\s)")
              hs-c-start-regexp (or (nth 3 lookup)
                                    (let ((c-start-regexp
                                           (regexp-quote comment-start)))
                                      (if (string-match " +$" c-start-regexp)
                                          (substring c-start-regexp
                                                     0 (1- (match-end 0)))
                                        c-start-regexp)))
              hs-forward-sexp-func (or (nth 4 lookup) 'forward-sexp)
              hs-adjust-block-beginning (nth 5 lookup)))
    (progn
      (setq hs-minor-mode nil)
      (error "%s Mode doesn't support Hideshow Minor Mode" mode-name))))

(defun hs-find-block-beginning ()
  "Reposition point at block-start.
Return point, or nil if original point was not in a block."
  (let ((done nil)
        (here (point)))
    ;; look if current line is block start
    (if (looking-at hs-block-start-regexp)
        (point)
      ;; look backward for the start of a block that contains the cursor
      (while (and (re-search-backward hs-block-start-regexp nil t)
                  (not (setq done
                             (< here (save-excursion
                                       (hs-forward-sexp (hs-match-data t) 1)
                                       (point)))))))
      (if done
          (point)
        (goto-char here)
        nil))))

(defun hs-hide-level-recursive (arg minp maxp)
  "Recursively hide blocks ARG levels below point in region (MINP MAXP)."
  (when (hs-find-block-beginning)
    (setq minp (1+ (point)))
    (funcall hs-forward-sexp-func 1)
    (setq maxp (1- (point))))
  (hs-flag-region minp maxp nil)        ; eliminate weirdness
  (goto-char minp)
  (while (progn
           (forward-comment (buffer-size))
           (and (< (point) maxp)
                (re-search-forward hs-block-start-regexp maxp t)))
    (if (> arg 1)
        (hs-hide-level-recursive (1- arg) minp maxp)
      (goto-char (match-beginning hs-block-start-mdata-select))
      (hs-hide-block-at-point t)))
    (hs-safety-is-job-n)
  (goto-char maxp))

(defmacro hs-life-goes-on (&rest body)
  "Evaluate BODY forms iff variable `hs-minor-mode' is non-nil.
In the dynamic context of this macro, `inhibit-point-motion-hooks'
and `case-fold-search' are both t."
  `(when hs-minor-mode
     (let ((inhibit-point-motion-hooks t)
           (case-fold-search t))
       ,@body)))

(put 'hs-life-goes-on 'edebug-form-spec '(&rest form))

(defun hs-already-hidden-p ()
  "Return non-nil if point is in an already-hidden block, otherwise nil."
  (save-excursion
    (let ((c-reg (hs-inside-comment-p)))
      (if (and c-reg (nth 0 c-reg))
          ;; point is inside a comment, and that comment is hidable
          (goto-char (nth 0 c-reg))
        (if (and (not c-reg)
                 (hs-find-block-beginning)
                 (looking-at hs-block-start-regexp))
            ;; point is inside a block
            (goto-char (match-end 0)))))
    (end-of-line)
    (let ((overlays (overlays-at (point)))
          (found nil))
      (while (and (not found) (overlayp (car overlays)))
           (setq found (overlay-get (car overlays) 'hs)
                 overlays (cdr overlays)))
      found)))

(defun hs-c-like-adjust-block-beginning (initial)
  "Adjust INITIAL, the buffer position after `hs-block-start-regexp'.
Actually, point is never moved; a new position is returned that is
the end of the C-function header.  This adjustment function is meant
to be assigned to `hs-adjust-block-beginning' for C-like modes."
  (save-excursion
    (goto-char (1- initial))
    (forward-comment (- (buffer-size)))
    (point)))

;;---------------------------------------------------------------------------
;; commands

(defun hs-hide-all ()
  "Hide all top level blocks, displaying only first and last lines.
Move point to the beginning of the line, and run the normal hook
`hs-hide-hook'.  See documentation for `run-hooks'.
If `hs-hide-comments-when-hiding-all' is non-nil, also hide the comments."
  (interactive)
  (hs-life-goes-on
   (message "Hiding all blocks ...")
   (save-excursion
     (hs-flag-region (point-min) (point-max) nil) ; eliminate weirdness
     (goto-char (point-min))
     (let ((count 0)
           (re (concat "\\("
                       hs-block-start-regexp
                       "\\)"
                       (if hs-hide-comments-when-hiding-all
                           (concat "\\|\\("
                                   hs-c-start-regexp
                                   "\\)")
                         ""))))
       (while (progn
                (unless hs-hide-comments-when-hiding-all
                  (forward-comment (point-max)))
                (re-search-forward re (point-max) t))
         (if (match-beginning 1)
             ;; we have found a block beginning
             (progn
               (goto-char (match-beginning 1))
               (if hs-hide-all-non-comment-function
                   (funcall hs-hide-all-non-comment-function)
                 (hs-hide-block-at-point t)))
           ;; found a comment, probably
           (let ((c-reg (hs-inside-comment-p)))         ; blech!
             (when (and c-reg (car c-reg))
               (if (> (count-lines (car c-reg) (nth 1 c-reg)) 1)
                   (hs-hide-block-at-point t c-reg)
                 (goto-char (nth 1 c-reg))))))
         (message "Hiding ... %d" (setq count (1+ count)))))
     (hs-safety-is-job-n))
   (beginning-of-line)
   (message "Hiding all blocks ... done")
   (run-hooks 'hs-hide-hook)))

(defun hs-show-all ()
  "Show everything then run `hs-show-hook'.  See `run-hooks'."
  (interactive)
  (hs-life-goes-on
   (message "Showing all blocks ...")
   (hs-flag-region (point-min) (point-max) nil)
   (message "Showing all blocks ... done")
   (run-hooks 'hs-show-hook)))

(defun hs-hide-block (&optional end)
  "Select a block and hide it.  With prefix arg, reposition at END.
Upon completion, point is repositioned and the normal hook
`hs-hide-hook' is run.  See documentation for `run-hooks'."
  (interactive "P")
  (hs-life-goes-on
   (let ((c-reg (hs-inside-comment-p)))
     (cond
      ((and c-reg (or (null (nth 0 c-reg))
                      (<= (count-lines (car c-reg) (nth 1 c-reg)) 1)))
       (message "(not enough comment lines to hide)"))
      ((or c-reg
           (looking-at hs-block-start-regexp)
           (hs-find-block-beginning))
       (hs-hide-block-at-point end c-reg)
       (hs-safety-is-job-n)
       (run-hooks 'hs-hide-hook))))))

(defun hs-show-block (&optional end)
  "Select a block and show it.
With prefix arg, reposition at END.  Upon completion, point is
repositioned and the normal hook `hs-show-hook' is run.
See documentation for functions `hs-hide-block' and `run-hooks'."
  (interactive "P")
  (hs-life-goes-on
   (or
    ;; first see if we have something at the end of the line
    (catch 'eol-begins-hidden-region-p
      (let ((here (point))
            (ovs (save-excursion (end-of-line) (overlays-at (point)))))
        (while ovs
          (let ((ov (car ovs)))
            (when (overlay-get ov 'hs)
              (goto-char
               (cond (end (overlay-end ov))
                     ((eq 'comment (overlay-get ov 'hs)) here)
                     (t (+ (overlay-start ov) (overlay-get ov 'hs-ofs)))))
              (delete-overlay ov)
              (throw 'eol-begins-hidden-region-p t)))
          (setq ovs (cdr ovs)))
        nil))
    ;; not immediately obvious, look for a suitable block
    (let ((c-reg (hs-inside-comment-p))
          p q)
      (cond (c-reg
             (when (car c-reg)
               (setq p (car c-reg)
                     q (cadr c-reg))))
            ((and (hs-find-block-beginning)
                  (looking-at hs-block-start-regexp)) ; fresh match-data, ugh
             (setq p (point)
                   q (progn (hs-forward-sexp (hs-match-data t) 1) (point)))))
      (when (and p q)
        (hs-flag-region p q nil)
        (goto-char (if end q (1+ p)))))
    (hs-safety-is-job-n)
    (run-hooks 'hs-show-hook))))

(defun hs-hide-level (arg)
  "Hide all blocks ARG levels below this block.
The hook `hs-hide-hook' is run; see `run-hooks'."
  (interactive "p")
  (hs-life-goes-on
   (save-excursion
     (message "Hiding blocks ...")
     (hs-hide-level-recursive arg (point-min) (point-max))
     (message "Hiding blocks ... done"))
   (hs-safety-is-job-n)
   (run-hooks 'hs-hide-hook)))

(defun hs-toggle-hiding ()
  "Toggle hiding/showing of a block.
See `hs-hide-block' and `hs-show-block'."
  (interactive)
  (hs-life-goes-on
   (if (hs-already-hidden-p)
       (hs-show-block)
     (hs-hide-block))))

(defun hs-mouse-toggle-hiding (e)
  "Toggle hiding/showing of a block.
This command should be bound to a mouse key.
Argument E is a mouse event used by `mouse-set-point'.
See `hs-hide-block' and `hs-show-block'."
  (interactive "@e")
  (hs-life-goes-on
   (mouse-set-point e)
   (hs-toggle-hiding)))

(defun hs-hide-initial-comment-block ()
  "Hide the first block of comments in a file.
This can be useful if you have huge RCS logs in those comments."
  (interactive)
  (hs-life-goes-on
   (let ((c-reg (save-excursion
                  (goto-char (point-min))
                  (skip-chars-forward " \t\n\f")
                  (hs-inside-comment-p))))
     (when c-reg
       (let ((beg (car c-reg)) (end (cadr c-reg)))
         ;; see if we have enough comment lines to hide
         (when (> (count-lines beg end) 1)
           (hs-hide-comment-region beg end)))))))

;;;###autoload
(defun hs-minor-mode (&optional arg)
  "Toggle hideshow minor mode.
With ARG, turn hideshow minor mode on if ARG is positive, off otherwise.
When hideshow minor mode is on, the menu bar is augmented with hideshow
commands and the hideshow commands are enabled.
The value '(hs . t) is added to `buffer-invisibility-spec'.

The main commands are: `hs-hide-all', `hs-show-all', `hs-hide-block',
`hs-show-block', `hs-hide-level' and `hs-toggle-hiding'.  There is also
`hs-hide-initial-comment-block' and `hs-mouse-toggle-hiding'.

Turning hideshow minor mode off reverts the menu bar and the
variables to default values and disables the hideshow commands.

Lastly, the normal hook `hs-minor-mode-hook' is run using `run-hooks'.

Key bindings:
\\{hs-minor-mode-map}"

  (interactive "P")
  (setq hs-headline nil
        hs-minor-mode (if (null arg)
                          (not hs-minor-mode)
                        (> (prefix-numeric-value arg) 0)))
  (if hs-minor-mode
      (progn
        (hs-grok-mode-type)
        (easy-menu-add hs-minor-mode-menu)
        (make-variable-buffer-local 'line-move-ignore-invisible)
        (setq line-move-ignore-invisible t)
        (add-to-invisibility-spec '(hs . t)))
    (easy-menu-remove hs-minor-mode-menu)
    (remove-from-invisibility-spec '(hs . t)))
  (run-hooks 'hs-minor-mode-hook))

;;---------------------------------------------------------------------------
;; load-time actions

;; keymaps and menus
(if hs-minor-mode-map
    nil
  (setq hs-minor-mode-map (make-sparse-keymap))
  (easy-menu-define hs-minor-mode-menu
    hs-minor-mode-map
    "Menu used when hideshow minor mode is active."
    (cons "Hide/Show"
          (mapcar
           ;; Interpret each table entry as follows: first, populate keymap
           ;; with elements 2 and 1; then, for easymenu, use entry directly
           ;; unless element 0 is nil, in which case the entry is "omitted".
           (lambda (ent)
             (define-key hs-minor-mode-map (aref ent 2) (aref ent 1))
             (if (aref ent 0) ent "-----"))
           ;; These bindings roughly imitate those used by Outline mode.
           ;; menu entry      command                key
           '(["Hide Block"    hs-hide-block          "\C-c@\C-h"]
             ["Show Block"    hs-show-block          "\C-c@\C-s"]
             ["Hide All"      hs-hide-all            "\C-c@\C-\M-h"]
             ["Show All"      hs-show-all            "\C-c@\C-\M-s"]
             ["Hide Level"    hs-hide-level          "\C-c@\C-l"]
             ["Toggle Hiding" hs-toggle-hiding       "\C-c@\C-c"]
             [nil             hs-mouse-toggle-hiding [(shift button2)]]
             )))))

;; some housekeeping
(or (assq 'hs-minor-mode minor-mode-map-alist)
    (setq minor-mode-map-alist
          (cons (cons 'hs-minor-mode hs-minor-mode-map)
                minor-mode-map-alist)))
(or (assq 'hs-minor-mode minor-mode-alist)
    (setq minor-mode-alist (append minor-mode-alist
                                   (list '(hs-minor-mode " hs")))))

;; make some variables permanently buffer-local
(let ((vars '(hs-minor-mode
              hs-c-start-regexp
              hs-block-start-regexp
              hs-block-start-mdata-select
              hs-block-end-regexp
              hs-forward-sexp-func
              hs-adjust-block-beginning)))
  (while vars
    (let ((var (car vars)))
      (make-variable-buffer-local var)
      (put var 'permanent-local t))
    (setq vars (cdr vars))))

;;---------------------------------------------------------------------------
;; that's it

(provide 'hideshow)

;;; hideshow.el ends here