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

;;; hide-ifdef-mode.el --- hides selected code within ifdef.

;; Copyright (C) 1988, 1994 Free Software Foundation, Inc.

;; Author: Daniel LaLiberte <liberte@holonexus.org>
;; Maintainer: FSF
;; Keywords: c, outlines

;; 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:

;; To initialize, toggle the hide-ifdef minor mode with
;;
;; M-x hide-ifdef-mode
;;
;; This will set up key bindings and call hide-ifdef-mode-hook if it
;; has a value.  To explicitly hide ifdefs using a buffer-local
;; define list (default empty), type
;;
;; M-x hide-ifdefs  or C-c @ h
;;
;; Hide-ifdef suppresses the display of code that the preprocessor wouldn't
;; pass through.  The support of constant expressions in #if lines is 
;; limited to identifiers, parens, and the operators: &&, ||, !, and
;; "defined".  Please extend this.
;;
;; The hidden code is marked by ellipses (...).  Be
;; cautious when editing near ellipses, since the hidden text is
;; still in the buffer, and you can move the point into it and modify
;; text unawares.  If you don't want to see the ellipses, set 
;; selective-display-ellipses to nil.  But this can be dangerous.
;; You can make your buffer read-only while hide-ifdef-hiding by setting
;; hide-ifdef-read-only to a non-nil value.  You can toggle this 
;; variable with hide-ifdef-toggle-read-only (C-c @ C-q).
;;
;; You can undo the effect of hide-ifdefs by typing
;;
;; M-x show-ifdefs  or C-c @ s
;;
;; Use M-x hide-ifdef-define (C-c @ d) to define a symbol.
;; Use M-x hide-ifdef-undef (C-c @ u) to undefine a symbol.
;;
;; If you define or undefine a symbol while hide-ifdef-mode is in effect,
;; the display will be updated.  Only the define list for the current
;; buffer will be affected.  You can save changes to the local define
;; list with hide-ifdef-set-define-alist.  This adds entries 
;; to hide-ifdef-define-alist.
;;
;; If you have defined a hide-ifdef-mode-hook, you can set
;; up a list of symbols that may be used by hide-ifdefs as in the
;; following example:
;;
;; (setq hide-ifdef-mode-hook
;;      (lambda ()
;;       (if (not hide-ifdef-define-alist)
;;           (setq hide-ifdef-define-alist
;;                '((list1 ONE TWO)
;;                  (list2 TWO THREE)
;;                  )))
;;       (hide-ifdef-use-define-alist 'list2) ; use list2 by default
;;       ))
;;
;; You can call hide-ifdef-use-define-alist (C-c @ U) at any time to specify
;; another list to use.
;;
;; To cause ifdefs to be hidden as soon as hide-ifdef-mode is called,
;; set hide-ifdef-initially to non-nil.
;;
;; If you set hide-ifdef-lines to t, hide-ifdefs hides all the #ifdef lines.
;; In the absence of highlighting, that might be a bad idea.  If you set
;; hide-ifdef-lines to nil (the default), the surrounding preprocessor
;; lines will be displayed.  That can be confusing in its own
;; right.  Other variations on display are possible, but not much
;; better.
;;
;; You can explicitly hide or show individual ifdef blocks irrespective
;; of the define list by using hide-ifdef-block and show-ifdef-block.
;;
;; You can move the point between ifdefs with forward-ifdef, backward-ifdef,
;; up-ifdef, down-ifdef, next-ifdef, and previous-ifdef.
;;
;; If you have minor-mode-alist in your mode line (the default) two labels
;; may appear.  "Ifdef" will appear when hide-ifdef-mode is active.  "Hiding"
;; will appear when text may be hidden ("hide-ifdef-hiding" is non-nil).
;;
;; Written by Brian Marick, at Gould, Computer Systems Division, Urbana IL.
;; Extensively modified by Daniel LaLiberte (while at Gould).
;;
;; You may freely modify and distribute this, but keep a record
;; of modifications and send comments to:
;;       liberte@a.cs.uiuc.edu  or  ihnp4!uiucdcs!liberte
;; I will continue to upgrade hide-ifdef-mode
;; with your contributions.

;;; Code:

(require 'cc-mode)

(defgroup hide-ifdef nil
  "Hide selected code within `ifdef'."
  :group 'c)

(defvar hide-ifdef-mode-submap nil
  "Keymap used with Hide-Ifdef mode.")

(defvar hide-ifdef-mode-map nil
  "Keymap used with Hide-Ifdef mode.")

(defconst hide-ifdef-mode-prefix-key "\C-c@"
  "Prefix key for all Hide-Ifdef mode commands.")

;; Set up the submap that goes after the prefix key.
(if hide-ifdef-mode-submap
    ()                          ; Don't redefine it.
  (setq hide-ifdef-mode-submap (make-sparse-keymap))
  (define-key hide-ifdef-mode-submap "d" 'hide-ifdef-define)
  (define-key hide-ifdef-mode-submap "u" 'hide-ifdef-undef)
  (define-key hide-ifdef-mode-submap "D" 'hide-ifdef-set-define-alist)
  (define-key hide-ifdef-mode-submap "U" 'hide-ifdef-use-define-alist)

  (define-key hide-ifdef-mode-submap "h" 'hide-ifdefs)
  (define-key hide-ifdef-mode-submap "s" 'show-ifdefs)
  (define-key hide-ifdef-mode-submap "\C-d" 'hide-ifdef-block)
  (define-key hide-ifdef-mode-submap "\C-s" 'show-ifdef-block)

  (define-key hide-ifdef-mode-submap "\C-q" 'hide-ifdef-toggle-read-only)
  (let ((where (where-is-internal 'toggle-read-only '(keymap) t)))
    (if where
        (define-key hide-ifdef-mode-submap
          where
          'hide-ifdef-toggle-outside-read-only)))
  )

;; Set up the mode's main map, which leads via the prefix key to the submap.
(if hide-ifdef-mode-map
    ()
  (setq hide-ifdef-mode-map (make-sparse-keymap))
  (define-key hide-ifdef-mode-map hide-ifdef-mode-prefix-key
    hide-ifdef-mode-submap))

;; Autoload for the benefit of `make-mode-line-mouse-sensitive'.
;;;###autoload
(defvar hide-ifdef-mode nil
  "Non-nil when hide-ifdef-mode is activated.")

(defvar hide-ifdef-hiding nil
  "Non-nil when text may be hidden.")

;; Arrange to use the mode's map when the mode is enabled.
(or (assq 'hide-ifdef-mode minor-mode-map-alist)
    (setq minor-mode-map-alist
          (cons (cons 'hide-ifdef-mode hide-ifdef-mode-map)
                minor-mode-map-alist)))

(or (assq 'hide-ifdef-hiding minor-mode-alist)
    (setq minor-mode-alist
          (cons '(hide-ifdef-hiding " Hiding")
                minor-mode-alist)))

(or (assq 'hide-ifdef-mode minor-mode-alist)
    (setq minor-mode-alist
          (cons '(hide-ifdef-mode " Ifdef")
                minor-mode-alist)))

;; fix c-mode syntax table so we can recognize whole symbols.
(defvar hide-ifdef-syntax-table
  (copy-syntax-table c-mode-syntax-table)
  "Syntax table used for tokenizing #if expressions.")

(modify-syntax-entry ?_ "w" hide-ifdef-syntax-table)
(modify-syntax-entry ?& "." hide-ifdef-syntax-table)
(modify-syntax-entry ?\| "." hide-ifdef-syntax-table)

(defvar hide-ifdef-env nil
  "An alist of defined symbols and their values.")

(defvar hif-outside-read-only nil
  "Internal variable.  Saves the value of `buffer-read-only' while hiding.")

;;;###autoload
(defun hide-ifdef-mode (arg)
  "Toggle Hide-Ifdef mode.  This is a minor mode, albeit a large one.
With ARG, turn Hide-Ifdef mode on if arg is positive, off otherwise.
In Hide-Ifdef mode, code within #ifdef constructs that the C preprocessor
would eliminate may be hidden from view.  Several variables affect
how the hiding is done:

hide-ifdef-env
        An association list of defined and undefined symbols for the
        current buffer.  Initially, the global value of `hide-ifdef-env'
        is used.

hide-ifdef-define-alist
        An association list of defined symbol lists.  
        Use `hide-ifdef-set-define-alist' to save the current `hide-ifdef-env'
        and `hide-ifdef-use-define-alist' to set the current `hide-ifdef-env'
        from one of the lists in `hide-ifdef-define-alist'.

hide-ifdef-lines
        Set to non-nil to not show #if, #ifdef, #ifndef, #else, and
        #endif lines when hiding.

hide-ifdef-initially
        Indicates whether `hide-ifdefs' should be called when Hide-Ifdef mode
        is activated.

hide-ifdef-read-only
        Set to non-nil if you want to make buffers read only while hiding.
        After `show-ifdefs', read-only status is restored to previous value.

\\{hide-ifdef-mode-map}"

  (interactive "P")
  (make-local-variable 'hide-ifdef-mode)
  (setq hide-ifdef-mode
        (if (null arg)
            (not hide-ifdef-mode)
          (> (prefix-numeric-value arg) 0)))
  
  (force-mode-line-update)

  (if hide-ifdef-mode
      (progn
        ; inherit global values
        (make-local-variable 'hide-ifdef-env)
        (setq hide-ifdef-env (default-value 'hide-ifdef-env))

        (make-local-variable 'hide-ifdef-hiding)
        (setq hide-ifdef-hiding (default-value 'hide-ifdef-hiding))

        (make-local-variable 'hif-outside-read-only)
        (setq hif-outside-read-only buffer-read-only)

        (run-hooks 'hide-ifdef-mode-hook)

        (if hide-ifdef-initially
            (hide-ifdefs)
          (show-ifdefs))
        (message "Enter Hide-Ifdef mode")
        )
     ; else end hide-ifdef-mode
    (if hide-ifdef-hiding
        (show-ifdefs))
    (message "Exit Hide-Ifdef mode")
    ))
  

;; from outline.el with docstring fixed.
(defun hif-outline-flag-region (from to flag)
  "Hides or shows lines from FROM to TO, according to FLAG.
If FLAG is \\n (newline character) then text is shown, while if FLAG is \\^M
\(control-M) the text is hidden."
  (let ((modp (buffer-modified-p)))
    (unwind-protect (progn
                      (subst-char-in-region from to
                              (if (= flag ?\n) ?\^M ?\n)
                              flag t) )
      (set-buffer-modified-p modp))
    ))

(defun hif-show-all ()
  "Show all of the text in the current buffer."
  (interactive)
  (hif-outline-flag-region (point-min) (point-max) ?\n))

;; By putting this on after-revert-hook, we arrange that it only
;; does anything when revert-buffer avoids turning off the mode.
;; (That can happen in VC.)
(defun hif-before-revert-function ()
  (and hide-ifdef-mode hide-ifdef-hiding
       (hide-ifdefs t)))
(add-hook 'after-revert-hook 'hif-before-revert-function)

(defun hide-ifdef-region (start end)
  "START is the start of a #if or #else form.  END is the ending part.
Everything including these lines is made invisible."
  (hif-outline-flag-region start end ?\^M)
  )

(defun hif-show-ifdef-region (start end)
  "Everything between START and END is made visible."
  (hif-outline-flag-region start end ?\n)
  )



;===%%SF%% evaluation (Start)  ===

;; It is not useful to set this to anything but `eval'.
;; In fact, the variable might as well be eliminated.
(defvar hide-ifdef-evaluator 'eval
  "The function to use to evaluate a form.
The evaluator is given a canonical form and returns t if text under
that form should be displayed.")

(defvar hif-undefined-symbol nil
  "...is by default considered to be false.")


(defun hif-set-var (var value)
  "Prepend (var value) pair to hide-ifdef-env."
  (setq hide-ifdef-env (cons (cons var value) hide-ifdef-env)))


(defun hif-lookup (var)
;  (message "hif-lookup %s" var)
  (let ((val (assoc var hide-ifdef-env)))
    (if val
        (cdr val)
      hif-undefined-symbol)))

(defun hif-defined (var)
  (hif-lookup var)
  ; when #if expressions are fully supported, defined result should be 1
  ;  (if (assoc var  hide-ifdef-env)
  ;      1
  ;    nil)
)


;===%%SF%% evaluation (End)  ===



;===%%SF%% parsing (Start)  ===
;;;  The code that understands what ifs and ifdef in files look like.

(defconst hif-cpp-prefix "\\(^\\|\r\\)[ \t]*#[ \t]*")
(defconst hif-ifndef-regexp (concat hif-cpp-prefix "ifndef"))
(defconst hif-ifx-regexp (concat hif-cpp-prefix "if\\(n?def\\)?[ \t]+"))
(defconst hif-else-regexp (concat hif-cpp-prefix "else"))
(defconst hif-endif-regexp (concat hif-cpp-prefix "endif"))
(defconst hif-ifx-else-endif-regexp
  (concat hif-ifx-regexp "\\|" hif-else-regexp "\\|" hif-endif-regexp))

; Used to store the current token and the whole token list during parsing.
; Only bound dynamically.
(defvar hif-token)
(defvar hif-token-list)

(defun hif-infix-to-prefix (token-list)
  "Convert list of tokens in infix into prefix list"
                                        ;  (message "hif-infix-to-prefix: %s" token-list)
  (if (= 1 (length token-list))
      `(hif-lookup (quote ,(car token-list)))
    (hif-parse-if-exp token-list))
  )

; pattern to match initial identifier, !, &&, ||, (, or ).
; Added ==, + and -: garyo@avs.com 8/9/94
(defconst hif-token-regexp "^\\(&&\\|||\\|[!=]=\\|!\\|[()+-]\\|[<>]=?\\|\\w+\\)")
(defconst hif-end-of-comment "\\*/")


(defun hif-tokenize (expr-string)
  "Separate string into a list of tokens"
  (let ((token-list nil)
        (expr-start 0)
        (expr-length (length expr-string))
        (current-syntax-table (syntax-table)))
    (unwind-protect
        (progn
          (set-syntax-table hide-ifdef-syntax-table)
          (while (< expr-start expr-length) 
;           (message "expr-start = %d" expr-start) (sit-for 1)
            (cond
             ((string-match "^[ \t]+" expr-string expr-start)
              ;; skip whitespace
              (setq expr-start (match-end 0))
              ;; stick newline in string so ^ matches on the next string-match
              (aset expr-string (1- expr-start) ?\n))

             ((string-match "^/\\*" expr-string expr-start)
              (setq expr-start (match-end 0))
              (aset expr-string (1- expr-start) ?\n)
              (or
               (string-match hif-end-of-comment
                             expr-string expr-start) ; eat comment
               (string-match "$" expr-string expr-start)) ; multi-line comment
              (setq expr-start (match-end 0))
              (aset expr-string (1- expr-start) ?\n))

             ((string-match "^//" expr-string expr-start)
              (string-match "$" expr-string expr-start)
              (setq expr-start (match-end 0)))

             ((string-match hif-token-regexp expr-string expr-start)
              (let ((token (substring expr-string expr-start (match-end 0))))
                (setq expr-start (match-end 0))
                (aset expr-string (1- expr-start) ?\n)
;               (message "token: %s" token) (sit-for 1)
                (setq token-list
                      (cons
                       (cond
                        ((string-equal token "||") 'or)
                        ((string-equal token "&&") 'and)
                        ((string-equal token "==") 'equal)
                        ((string-equal token "!=") 'hif-notequal)
                        ((string-equal token "!")  'not)
                        ((string-equal token "defined") 'hif-defined)
                        ((string-equal token "(") 'lparen)
                        ((string-equal token ")") 'rparen)
                        ((string-equal token ">") 'hif-greater)
                        ((string-equal token "<") 'hif-less)
                        ((string-equal token ">=") 'hif-greater-equal)
                        ((string-equal token "<=") 'hif-less-equal)
                        ((string-equal token "+") 'hif-plus)
                        ((string-equal token "-") 'hif-minus)
                        (t (intern token)))
                       token-list))))
             (t (error "Bad #if expression: %s" expr-string)))))
      (set-syntax-table current-syntax-table))
    (nreverse token-list)))

;;;-----------------------------------------------------------------
;;; Translate C preprocessor #if expressions using recursive descent.
;;; This parser is limited to the operators &&, ||, !, and "defined".
;;; Added ==, !=, +, and -.  Gary Oberbrunner, garyo@avs.com, 8/9/94

(defun hif-parse-if-exp (hif-token-list)
  "Parse the TOKEN-LIST.  Return translated list in prefix form."
  (hif-nexttoken)
  (prog1
      (hif-expr)
    (if hif-token ; is there still a token?
        (error "Error: unexpected token: %s" hif-token))))

(defun hif-nexttoken ()
  "Pop the next token from token-list into the let variable \"hif-token\"."
  (setq hif-token (car hif-token-list))
  (setq hif-token-list (cdr hif-token-list))
  hif-token)

(defun hif-expr ()
  "Parse an expression as found in #if.
       expr : term | expr '||' term."
  (let ((result (hif-term)))
    (while (eq hif-token 'or)
      (hif-nexttoken)
      (setq result (list 'or result (hif-term))))
  result))

(defun hif-term ()
  "Parse a term : eq-expr | term '&&' eq-expr."
  (let ((result (hif-eq-expr)))
    (while (eq hif-token 'and)
      (hif-nexttoken)
      (setq result (list 'and result (hif-eq-expr))))
    result))

(defun hif-eq-expr ()
  "Parse an eq-expr : math | eq-expr `=='|`!='|`<'|`>'|`>='|`<=' math."
  (let ((result (hif-math))
        (eq-token nil))
    (while (memq hif-token '(equal hif-notequal hif-greater hif-less
                             hif-greater-equal hif-less-equal))
      (setq eq-token hif-token)
      (hif-nexttoken)
      (setq result (list eq-token result (hif-math))))
    result))

(defun hif-math ()
  "Parse an expression with + or - and simpler things.
       math : factor | math '+|-' factor."
  (let ((result (hif-factor))
        (math-op nil))
    (while (or (eq hif-token 'hif-plus) (eq hif-token 'hif-minus))
      (setq math-op hif-token)
      (hif-nexttoken)
      (setq result (list math-op result (hif-factor))))
  result))
  
(defun hif-factor ()
  "Parse a factor: '!' factor | '(' expr ')' | 'defined(' id ')' | id."
  (cond
   ((eq hif-token 'not)
    (hif-nexttoken)
    (list 'not (hif-factor)))

   ((eq hif-token 'lparen)
    (hif-nexttoken)
    (let ((result (hif-expr)))
      (if (not (eq hif-token 'rparen))
          (error "Bad token in parenthesized expression: %s" hif-token)
        (hif-nexttoken)
        result)))

   ((eq hif-token 'hif-defined)
    (hif-nexttoken)
    (if (not (eq hif-token 'lparen))
        (error "Error: expected \"(\" after \"defined\""))
    (hif-nexttoken)
    (let ((ident hif-token))
      (if (memq hif-token '(or and not hif-defined lparen rparen))
          (error "Error: unexpected token: %s" hif-token))
      (hif-nexttoken)
      (if (not (eq hif-token 'rparen))
          (error "Error: expected \")\" after identifier"))
      (hif-nexttoken)
      `(hif-defined (quote ,ident))
      ))

   (t                                   ; identifier
    (let ((ident hif-token))
      (if (memq ident '(or and))
          (error "Error: missing identifier"))
      (hif-nexttoken)
      `(hif-lookup (quote ,ident))
      ))
   ))

(defun hif-mathify (val)
  "Treat VAL as a number: if it's t or nil, use 1 or 0."
  (cond ((eq val t)
         1)
        ((null val)
         0)
        (t val)))

(defun hif-plus (a b)
  "Like ordinary plus but treat t and nil as 1 and 0."
  (+ (hif-mathify a) (hif-mathify b)))
(defun hif-minus (a b)
  "Like ordinary minus but treat t and nil as 1 and 0."
  (- (hif-mathify a) (hif-mathify b)))
(defun hif-notequal (a b)
  "Like (not (equal A B)) but as one symbol."
  (not (equal a b)))
(defun hif-greater (a b)
  "Simple comparison."
  (> (hif-mathify a) (hif-mathify b)))
(defun hif-less (a b)
  "Simple comparison."
  (< (hif-mathify a) (hif-mathify b)))
(defun hif-greater-equal (a b)
  "Simple comparison."
  (>= (hif-mathify a) (hif-mathify b)))
(defun hif-less-equal (a b)
  "Simple comparison."
  (<= (hif-mathify a) (hif-mathify b)))
;;;----------- end of parser -----------------------


(defun hif-canonicalize ()
  "When at beginning of #ifX, returns a Lisp expression for its condition."
  (save-excursion
    (let ((negate (looking-at hif-ifndef-regexp)))
      (re-search-forward hif-ifx-regexp)
      (let* ((expr-string
              (buffer-substring (point)
                                (progn (skip-chars-forward "^\n\r") (point))))
             (expr (hif-infix-to-prefix (hif-tokenize expr-string))))
;       (message "hif-canonicalized: %s" expr)
        (if negate
            (list 'not expr)
          expr)))))


(defun hif-find-any-ifX ()
  "Move to next #if..., or #ifndef, at point or after."
;  (message "find ifX at %d" (point))
  (prog1
      (re-search-forward hif-ifx-regexp (point-max) t)
    (beginning-of-line)))


(defun hif-find-next-relevant ()
  "Move to next #if..., #else, or #endif, after the current line."
;  (message "hif-find-next-relevant at %d" (point))
  (end-of-line)
  ; avoid infinite recursion by only going to beginning of line if match found
  (if (re-search-forward hif-ifx-else-endif-regexp (point-max) t)
      (beginning-of-line)))

(defun hif-find-previous-relevant ()
  "Move to previous #if..., #else, or #endif, before the current line."
;  (message "hif-find-previous-relevant at %d" (point))
  (beginning-of-line)
  ; avoid infinite recursion by only going to beginning of line if match found
  (if (re-search-backward hif-ifx-else-endif-regexp (point-min) t)
     (beginning-of-line)))


(defun hif-looking-at-ifX ()            ;; Should eventually see #if
  (looking-at hif-ifx-regexp))
(defun hif-looking-at-endif ()
  (looking-at hif-endif-regexp))
(defun hif-looking-at-else ()
  (looking-at hif-else-regexp))



(defun hif-ifdef-to-endif ()
  "If positioned at #ifX or #else form, skip to corresponding #endif."
;  (message "hif-ifdef-to-endif at %d" (point)) (sit-for 1)
  (hif-find-next-relevant)
  (cond ((hif-looking-at-ifX)
         (hif-ifdef-to-endif) ; find endif of nested if
         (hif-ifdef-to-endif)) ; find outer endif or else
        ((hif-looking-at-else)
         (hif-ifdef-to-endif)) ; find endif following else
        ((hif-looking-at-endif)
         'done)
        (t
         (error "Mismatched #ifdef #endif pair"))))


(defun hif-endif-to-ifdef ()
  "If positioned at #endif form, skip backward to corresponding #ifX."
;  (message "hif-endif-to-ifdef at %d" (point))
  (let ((start (point)))
    (hif-find-previous-relevant)
    (if (= start (point))
        (error "Mismatched #ifdef #endif pair")))
  (cond ((hif-looking-at-endif)
         (hif-endif-to-ifdef) ; find beginning of nested if
         (hif-endif-to-ifdef)) ; find beginning of outer if or else
        ((hif-looking-at-else)
         (hif-endif-to-ifdef))
        ((hif-looking-at-ifX)
         'done)
        (t)))                   ; never gets here


(defun forward-ifdef (&optional arg)
  "Move point to beginning of line of the next ifdef-endif.
With argument, do this that many times."
  (interactive "p")
  (or arg (setq arg 1))
  (if (< arg 0)
      (backward-ifdef (- arg)))
  (while (< 0 arg)
    (setq arg (- arg))
    (let ((start (point)))
      (if (not (hif-looking-at-ifX))
          (hif-find-next-relevant))
      (if (hif-looking-at-ifX)
          (hif-ifdef-to-endif)
        (goto-char start)
        (error "No following #ifdef")
        ))))


(defun backward-ifdef (&optional arg)
  "Move point to beginning of the previous ifdef-endif.
With argument, do this that many times."
  (interactive "p")
  (or arg (setq arg 1))
  (if (< arg 0)
      (forward-ifdef (- arg)))
  (while (< 0 arg)
    (setq arg (1- arg))
    (beginning-of-line)
    (let ((start (point)))
      (if (not (hif-looking-at-endif))
          (hif-find-previous-relevant))
      (if (hif-looking-at-endif)
          (hif-endif-to-ifdef)
        (goto-char start)
        (error "No previous #ifdef")))))


(defun down-ifdef ()
  "Move point to beginning of nested ifdef or else-part."
    (interactive)
    (let ((start (point)))
      (hif-find-next-relevant)
      (if (or (hif-looking-at-ifX) (hif-looking-at-else))
          ()
        (goto-char start)
        (error "No following #ifdef"))))


(defun up-ifdef ()
  "Move point to beginning of enclosing ifdef or else-part."
  (interactive)
  (beginning-of-line)
  (let ((start (point)))
    (if (not (hif-looking-at-endif))
        (hif-find-previous-relevant))
    (if (hif-looking-at-endif)
        (hif-endif-to-ifdef))
      (if (= start (point))
          (error "No previous #ifdef"))))

(defun next-ifdef (&optional arg)
  "Move to the beginning of the next #ifX, #else, or #endif.
With argument, do this that many times."
  (interactive "p")
  (or arg (setq arg 1))
  (if (< arg 0)
      (previous-ifdef (- arg)))
  (while (< 0 arg)
    (setq arg (1- arg))
    (hif-find-next-relevant)
    (if (eolp)
        (progn
          (beginning-of-line)
          (error "No following #ifdefs, #elses, or #endifs")))))

(defun previous-ifdef (&optional arg)
  "Move to the beginning of the previous #ifX, #else, or #endif.
With argument, do this that many times."
  (interactive "p")
  (or arg (setq arg 1))
  (if (< arg 0)
      (next-ifdef (- arg)))
  (while (< 0 arg)
    (setq arg (1- arg))
    (let ((start (point)))
      (hif-find-previous-relevant)
      (if (= start (point))
          (error "No previous #ifdefs, #elses, or #endifs")
        ))))


;===%%SF%% parsing (End)  ===


;===%%SF%% hide-ifdef-hiding (Start)  ===


;;; A range is a structure with four components:
;;; ELSE-P      True if there was an else clause for the ifdef.
;;; START       The start of the range. (beginning of line)
;;; ELSE        The else marker (beginning of line)
;;;                     Only valid if ELSE-P is true.
;;; END         The end of the range.  (beginning of line)

(defun hif-make-range (else-p start end &optional else)
  (list else-p start else end))

(defun hif-range-else-p (range)  (elt range 0))
(defun hif-range-start (range) (elt range 1))
(defun hif-range-else (range) (elt range 2))
(defun hif-range-end (range) (elt range 3))



;;; Find-Range
;;; The workhorse, it delimits the #if region.  Reasonably simple:
;;; Skip until an #else or #endif is found, remembering positions.  If
;;; an #else was found, skip some more, looking for the true #endif.

(defun hif-find-range ()
  "Returns a Range structure describing the current #if region.
Point is left unchanged."
;  (message "hif-find-range at %d" (point))
  (save-excursion
    (beginning-of-line)
    (let ((start (point))
          (else-p nil)
          (else nil)
          (end nil))
      ;; Part one.  Look for either #endif or #else.
      ;; This loop-and-a-half dedicated to E. Dijkstra.
      (hif-find-next-relevant)
      (while (hif-looking-at-ifX)               ; Skip nested ifdef
        (hif-ifdef-to-endif)
        (hif-find-next-relevant))
      ;; Found either a #else or an #endif.
      (cond ((hif-looking-at-else)
             (setq else-p t)
             (setq else (point)))
            (t
             (setq end (point)) ; (save-excursion (end-of-line) (point))
             ))
      ;; If found #else, look for #endif.
      (if else-p
          (progn
            (hif-find-next-relevant)
            (while (hif-looking-at-ifX) ; Skip nested ifdef
              (hif-ifdef-to-endif)
              (hif-find-next-relevant))
            (if (hif-looking-at-else)
                (error "Found two elses in a row?  Broken!"))
            (setq end (point))  ; (save-excursion (end-of-line) (point))
            ))
      (hif-make-range else-p start end else))))

          
;;; A bit slimy.
;;; NOTE:  If there's an #ifdef at the beginning of the file, we can't
;;; hide it.  There's no previous newline to replace.  If we added
;;; one, we'd throw off all the counts.  Feh.

(defun hif-hide-line (point)
  "Hide the line containing point.  Does nothing if `hide-ifdef-lines' is nil."
  (if hide-ifdef-lines
      (save-excursion
        (goto-char point)
        (let ((modp (buffer-modified-p)))
          (unwind-protect
              (progn
                (beginning-of-line)
                (if (not (= (point) 1))
                    (hide-ifdef-region (1- (point)) (point))))
            (set-buffer-modified-p modp))
          ))
    ))
                  

;;;  Hif-Possibly-Hide
;;;  There are four cases.  The #ifX expression is "taken" if it
;;;  the hide-ifdef-evaluator returns T.  Presumably, this means the code
;;;  inside the #ifdef would be included when the program was
;;;  compiled.  
;;;
;;;  Case 1:  #ifX taken, and there's an #else.
;;;     The #else part must be hidden.  The #if (then) part must be
;;;     processed for nested #ifX's.
;;;  Case 2:  #ifX taken, and there's no #else.
;;;     The #if part must be processed for nested #ifX's.
;;;  Case 3:  #ifX not taken, and there's an #else.
;;;     The #if part must be hidden.  The #else part must be processed
;;;     for nested #ifs.
;;;  Case 4:  #ifX not taken, and there's no #else.
;;;     The #ifX part must be hidden.
;;;
;;;  Further processing is done by narrowing to the relevant region
;;;  and just recursively calling hide-ifdef-guts.
;;;
;;;  When hif-possibly-hide returns, point is at the end of the
;;;  possibly-hidden range.

(defun hif-recurse-on (start end)
  "Call `hide-ifdef-guts' after narrowing to end of START line and END line."
  (save-excursion
    (save-restriction
      (goto-char start)
      (end-of-line)
      (narrow-to-region (point) end)
      (hide-ifdef-guts))))

(defun hif-possibly-hide ()
  "Called at #ifX expression, this hides those parts that should be hidden.
It uses the judgement of `hide-ifdef-evaluator'."
;  (message "hif-possibly-hide") (sit-for 1)
    (let ((test (hif-canonicalize))
          (range (hif-find-range)))
;      (message "test = %s" test) (sit-for 1)
      
      (hif-hide-line (hif-range-end range))
      (if (funcall hide-ifdef-evaluator test)
          (cond ((hif-range-else-p range) ; case 1
                 (hif-hide-line (hif-range-else range))
                 (hide-ifdef-region (hif-range-else range) 
                                    (1- (hif-range-end range)))
                 (hif-recurse-on (hif-range-start range)
                                 (hif-range-else range)))
                (t ; case 2
                 (hif-recurse-on (hif-range-start range)
                                 (hif-range-end range))))
        (cond ((hif-range-else-p range) ; case 3
               (hif-hide-line (hif-range-else range))
               (hide-ifdef-region (hif-range-start range)
                                  (1- (hif-range-else range)))
               (hif-recurse-on (hif-range-else range)
                               (hif-range-end range)))
              (t ; case 4
               (hide-ifdef-region (point)
                                  (1- (hif-range-end range))))
              ))
      (hif-hide-line (hif-range-start range))   ; Always hide start.
      (goto-char (hif-range-end range))
      (end-of-line)
      ))



(defun hide-ifdef-guts ()
  "Does most of the work of `hide-ifdefs'.
It does not do the work that's pointless to redo on a recursive entry."
;  (message "hide-ifdef-guts")
  (save-excursion
    (goto-char (point-min))
    (while (hif-find-any-ifX)
      (hif-possibly-hide))))

;===%%SF%% hide-ifdef-hiding (End)  ===


;===%%SF%% exports (Start)  ===

;;;###autoload
(defcustom hide-ifdef-initially nil
  "*Non-nil means call `hide-ifdefs' when Hide-Ifdef mode is first activated."
  :type 'boolean
  :group 'hide-ifdef)

;;;###autoload
(defcustom hide-ifdef-read-only nil
  "*Set to non-nil if you want buffer to be read-only while hiding text."
  :type 'boolean
  :group 'hide-ifdef)

;;;###autoload
(defcustom hide-ifdef-lines nil
  "*Non-nil means hide the #ifX, #else, and #endif lines."
  :type 'boolean
  :group 'hide-ifdef)

(defun hide-ifdef-toggle-read-only ()
  "Toggle hide-ifdef-read-only."
  (interactive)
  (setq hide-ifdef-read-only (not hide-ifdef-read-only))
  (message "Hide-Read-Only %s"
           (if hide-ifdef-read-only "ON" "OFF"))
  (if hide-ifdef-hiding
      (setq buffer-read-only (or hide-ifdef-read-only hif-outside-read-only)))
  (force-mode-line-update))

(defun hide-ifdef-toggle-outside-read-only ()
  "Replacement for `toggle-read-only' within Hide-Ifdef mode."
  (interactive)
  (setq hif-outside-read-only (not hif-outside-read-only))
  (message "Read only %s"
           (if hif-outside-read-only "ON" "OFF"))
  (setq buffer-read-only
        (or (and hide-ifdef-hiding hide-ifdef-read-only)
            hif-outside-read-only)
        )
  (force-mode-line-update))

      
(defun hide-ifdef-define (var)
  "Define a VAR so that #ifdef VAR would be included."
  (interactive "SDefine what? ")
  (hif-set-var var 1)
  (if hide-ifdef-hiding (hide-ifdefs)))

(defun hide-ifdef-undef (var)
  "Undefine a VAR so that #ifdef VAR would not be included."
  (interactive "SUndefine what? ")
  (hif-set-var var nil)
  (if hide-ifdef-hiding (hide-ifdefs)))


(defun hide-ifdefs (&optional nomsg)
  "Hide the contents of some #ifdefs.  
Assume that defined symbols have been added to `hide-ifdef-env'.  
The text hidden is the text that would not be included by the C
preprocessor if it were given the file with those symbols defined.

Turn off hiding by calling `show-ifdefs'."

  (interactive)
  (message "Hiding...")
  (setq hif-outside-read-only buffer-read-only)
  (if (not hide-ifdef-mode)
      (hide-ifdef-mode 1)) ; turn on hide-ifdef-mode
  (if hide-ifdef-hiding
      (show-ifdefs))                    ; Otherwise, deep confusion.
  (let ((inhibit-read-only t))
    (setq selective-display t)
    (setq hide-ifdef-hiding t)
    (hide-ifdef-guts))
  (setq buffer-read-only (or hide-ifdef-read-only hif-outside-read-only))
  (or nomsg
      (message "Hiding done")))


(defun show-ifdefs ()
  "Cancel the effects of `hide-ifdef': show the contents of all #ifdefs."
  (interactive)
  (setq buffer-read-only hif-outside-read-only)
  (setq selective-display nil)  ; defaults
  (let ((inhibit-read-only t))
    (hif-show-all))
  (setq hide-ifdef-hiding nil))


(defun hif-find-ifdef-block ()
  "Utility for hide and show `ifdef-block'.
Return as (TOP . BOTTOM) the extent of ifdef block."
  (let (max-bottom)
    (cons (save-excursion
            (beginning-of-line)
            (if (not (or (hif-looking-at-else) (hif-looking-at-ifX)))
                (up-ifdef))
            (prog1 (point)
              (hif-ifdef-to-endif)
              (setq max-bottom (1- (point)))))
          (save-excursion
            (beginning-of-line)
            (if (not (hif-looking-at-endif))
                (hif-find-next-relevant))
            (while (hif-looking-at-ifX)
              (hif-ifdef-to-endif)
              (hif-find-next-relevant))
            (min max-bottom (1- (point)))))))


(defun hide-ifdef-block ()
  "Hide the ifdef block (true or false part) enclosing or before the cursor."
  (interactive)
  (if (not hide-ifdef-mode)
      (hide-ifdef-mode 1))
  (setq selective-display t)
  (let ((top-bottom (hif-find-ifdef-block))
        (inhibit-read-only t))
    (hide-ifdef-region (car top-bottom) (cdr top-bottom))
    (if hide-ifdef-lines
        (progn
          (hif-hide-line (car top-bottom))
          (hif-hide-line (1+ (cdr top-bottom)))))
    (setq hide-ifdef-hiding t))
  (setq buffer-read-only (or hide-ifdef-read-only hif-outside-read-only)))


(defun show-ifdef-block ()
  "Show the ifdef block (true or false part) enclosing or before the cursor."
  (interactive)
  (let ((inhibit-read-only t))
    (if hide-ifdef-lines
        (save-excursion
          (beginning-of-line)
          (hif-show-ifdef-region (1- (point)) (progn (end-of-line) (point))))

      (let ((top-bottom (hif-find-ifdef-block)))
        (hif-show-ifdef-region (1- (car top-bottom)) (cdr top-bottom))))))


;;;  definition alist support

(defvar hide-ifdef-define-alist nil
  "A global assoc list of pre-defined symbol lists")

(defun hif-compress-define-list (env)
  "Compress the define list ENV into a list of defined symbols only."
  (let ((defs (mapcar (lambda (arg)
                        (if (hif-lookup (car arg)) (car arg)))
                      env))
        (new-defs nil))
    (while defs
      (if (car defs)
          (setq new-defs (cons (car defs) new-defs)))
      (setq defs (cdr defs)))
    new-defs))

(defun hide-ifdef-set-define-alist (name)
  "Set the association for NAME to `hide-ifdef-env'."
  (interactive "SSet define list: ")
  (setq hide-ifdef-define-alist
        (cons (cons name (hif-compress-define-list hide-ifdef-env))
              hide-ifdef-define-alist)))

(defun hide-ifdef-use-define-alist (name)
  "Set `hide-ifdef-env' to the define list specified by NAME."
  (interactive "SUse define list: ")
  (let ((define-list (assoc name hide-ifdef-define-alist)))
    (if define-list
        (setq hide-ifdef-env
              (mapcar (lambda (arg) (cons arg t))
                      (cdr define-list)))
      (error "No define list for %s" name))
    (if hide-ifdef-hiding (hide-ifdefs))))

(provide 'hideif)

;;; hideif.el ends here