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+;;; cpp.el --- Highlight or hide text according to cpp conditionals.
+
+;; Copyright (C) 1994 Free Software Foundation
+
+;; Author: Per Abrahamsen <abraham@iesd.auc.dk>
+;; Version: $Id: 0.2 ALPHA RELEASE WITH BUGS $
+;; Keywords: c, faces, tools
+
+;; LCD Archive Entry:
+;; cpp|Per Abrahamsen|abraham@iesd.auc.dk|
+;; Highlight or hide text according to cpp conditionals|
+;; $Date: 1994-07-20 $|$Revision: 0.2 $|~/misc/cpp.Z|
+
+;; This program 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.
+;; 
+;; This program 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 this program; if not, write to the Free Software
+;; Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+;;; Comments:
+
+;; Parse a text for C preprocessor conditionals, and highlight or hide
+;; the text inside the conditionals as you wish.
+
+;; Insert the following in your `emacs' to activate it.  This assumes
+;; you use BAW's superior cc-mode instead of Boring Old C-Mode.
+
+;; (autoload 'cpp-parse-buffer "cpp" "Parse and display cpp conditionals." t)
+  
+;; (eval-after-load "cc-mode"
+;;   '(progn
+;;      (define-key c-mode-map "\C-c\C-x" 'cpp-parse-buffer)
+;;      (define-key-after (bar (lookup-key c-mode-map [ menu-bar c ]))
+;;        [ cpp-parse ] '("Parse Conditionals" . cpp-parse-buffer) 'up))))
+
+;; Requires GNU Emacs 19.
+
+;;; Todo:
+
+;; Should parse "#if" and "#elif" expressions and merge the faces
+;; somehow. 
+
+;; Somehow it is sometimes possible to make changes near a read only
+;; area which you can't undo.  Their are other strange effects in that
+;; area.
+
+;; The Edit buffer should -- optionally -- appear in its own frame.
+
+;; Conditionals seem to be rear-sticky.  They shouldn't be.
+
+;; Restore window configurations when exiting CPP Edit buffer.
+
+;;; Code:
+
+;;; Customization:
+
+(defvar cpp-known-face 'invisible
+  "*Face used for known cpp symbols.")
+
+(defvar cpp-unknown-face 'highlight
+  "*Face used for unknown cpp cymbols.")
+
+(defvar cpp-face-type 'light 
+  "*Indicate what background face type you prefer.
+Can be either light or dark for color screens, mono for monochrome
+screens, and none if you don't use a window system.")
+
+(defvar cpp-known-writable t
+  "*Non-nil means you are allowed to modify the known conditionals.")
+
+(defvar cpp-unknown-writable t
+  "*Non-nil means you are allowed to modify the unknown conditionals.")
+
+;;; Parse Buffer:
+
+(defvar cpp-parse-symbols nil
+  "List of cpp macros used in the local buffer.")
+(make-variable-buffer-local 'cpp-parse-symbols)
+
+(defconst cpp-parse-regexp
+  ;; Regexp matching all tokens needed to find conditionals.
+  (concat
+   "'\\|\"\\|/\\*\\|//\\|"
+   "\\(^[ \t]*#[ \t]*\\(ifdef\\|ifndef\\|if\\|"
+   "elif\\|else\\|endif\\)\\b\\)"))
+
+;;;###autoload
+(defun cpp-parse-buffer (arg)
+  "Parse all conditionals in the current buffer end edit symbols.
+A prefix arg supress editing the symbols."
+  (interactive "P")
+  (setq cpp-parse-symbols nil)
+  (cpp-parse-reset)
+  (if (null cpp-edit-list)
+      (cpp-edit-load))
+  (let (stack)
+    (save-excursion
+      (goto-char (point-min))
+      (cpp-progress-message "Parsing...")
+      (while (re-search-forward cpp-parse-regexp nil t)
+        (cpp-progress-message "Parsing...%d%%"
+                          (/ (* 100 (- (point) (point-min))) (buffer-size)))
+        (let ((match (buffer-substring (match-beginning 0) (match-end 0))))
+          (cond ((or (string-equal match "'")
+                     (string-equal match "\""))
+                 (goto-char (match-beginning 0))
+                 (condition-case nil
+                     (forward-sexp)
+                   (error (cpp-parse-error
+                           "Unterminated string or character"))))
+                ((string-equal match "/*")
+                 (or (search-forward "*/" nil t)
+                     (error "Unterminated comment")))
+                ((string-equal match "//")
+                 (skip-chars-forward "^\n\r"))
+                (t
+                 (end-of-line 1)
+                 (let ((from (match-beginning 1))
+                       (to (1+ (point)))
+                       (type (buffer-substring (match-beginning 2)
+                                               (match-end 2)))
+                       (expr (buffer-substring (match-end 1) (point))))
+                   (cond ((string-equal type "ifdef")
+                          (cpp-parse-open t expr from to))
+                         ((string-equal type "ifndef")
+                          (cpp-parse-open nil expr from to))
+                         ((string-equal type "if")
+                          (cpp-parse-open t expr from to))
+                         ((string-equal type "elif")
+                          (let (cpp-known-face cpp-unknown-face)
+                            (cpp-parse-close from to))
+                          (cpp-parse-open t expr from to))
+                         ((string-equal type "else")
+                          (or stack (cpp-parse-error "Top level #else"))
+                          (let ((entry (list (not (nth 0 (car stack)))
+                                             (nth 1 (car stack))
+                                             from to)))
+                            (cpp-parse-close from to)
+                            (setq stack (cons entry stack))))
+                         ((string-equal type "endif")
+                          (cpp-parse-close from to))
+                         (t
+                          (cpp-parse-error "Parser error"))))))))
+      (message "Parsing...done"))
+    (if stack
+      (save-excursion
+        (goto-char (nth 3 (car stack)))
+        (cpp-parse-error "Unclosed conditional"))))
+  (or arg
+      (null cpp-parse-symbols)
+      (cpp-parse-edit)))
+
+(defun cpp-parse-open (branch expr begin end)
+  ;; Push information about conditional to stack.
+  (while (string-match "\\b[ \t]*/\\*.*\\*/[ \t]*\\b" expr)
+    (setq expr (concat (substring expr 0 (match-beginning 0))
+                       (substring expr (match-end 0)))))
+  (if (string-match "\\b[ \t]*\\(//.*\\)?$" expr)
+      (setq expr (substring expr 0 (match-beginning 0))))
+  (while (string-match "[ \t]+" expr)
+      (setq expr (concat (substring expr 0 (match-beginning 0))
+                         (substring expr (match-end 0)))))
+  (setq stack (cons (list branch expr begin end) stack))
+  (or (member expr cpp-parse-symbols)
+      (setq cpp-parse-symbols
+            (cons expr cpp-parse-symbols)))
+  (if (assoc expr cpp-edit-list)
+      (cpp-make-known-overlay begin end)
+    (cpp-make-unknown-overlay begin end)))
+
+(defun cpp-parse-close (from to)
+  ;; Pop top of stack and create overlay.
+  (let ((entry (assoc (nth 1 (car stack)) cpp-edit-list))
+        (branch (nth 0 (car stack)))
+        (begin (nth 2 (car stack)))
+        (end (nth 3 (car stack))))
+    (setq stack (cdr stack))
+    (if entry
+        (let ((face (nth (if branch 1 2) entry))
+              (read-only (eq (not branch) (nth 3 entry)))
+              (priority (length stack))
+              (overlay (make-overlay end from)))
+          (cpp-make-known-overlay from to)
+          (setq cpp-overlay-list (cons overlay cpp-overlay-list))
+          (if priority (overlay-put overlay 'priority priority))
+          (cond ((eq face 'invisible)
+                 (cpp-make-overlay-hidden overlay))
+                ((eq face 'default))
+                (t
+                 (overlay-put overlay 'face face)))
+          (if read-only
+              (cpp-make-overlay-read-only overlay)
+            (cpp-make-overlay-sticky overlay)))
+      (cpp-make-unknown-overlay from to))))
+
+(defun cpp-parse-error (error)
+  ;; Error message issued by the cpp parser.
+  (error (concat error " at line %d") (count-lines (point-min) (point))))
+
+(defun cpp-parse-reset ()
+  "Reset display of cpp conditionals to normal."
+  (interactive)
+  (while cpp-overlay-list
+    (delete-overlay (car cpp-overlay-list))
+    (setq cpp-overlay-list (cdr cpp-overlay-list))))
+
+;;;###autoload
+(defun cpp-parse-edit ()
+  "Edit display information for cpp conditionals."
+  (interactive)
+  (or cpp-parse-symbols
+      (cpp-parse-buffer t))
+  (let ((buffer (current-buffer)))
+    (pop-to-buffer "*CPP Edit*")
+    (cpp-edit-mode)
+    (setq cpp-edit-buffer buffer)
+    (cpp-edit-reset)))
+
+;;; Overlays:
+
+(defvar cpp-overlay-list nil)
+;; List of cpp overlays active in the current buffer.
+(make-variable-buffer-local 'cpp-overlay-list)
+
+(defun cpp-make-known-overlay (start end)
+  ;; Create an overlay for a known cpp command from START to END.
+  (let ((overlay (make-overlay start end)))
+    (if (eq cpp-known-face 'invisible)
+        (cpp-make-overlay-hidden overlay)
+      (or (eq cpp-known-face 'default)
+          (overlay-put overlay 'face cpp-known-face))
+      (if cpp-known-writable
+          ()
+        (overlay-put overlay 'modification-hooks '(cpp-signal-read-only))
+        (overlay-put overlay 'insert-in-front-hooks '(cpp-signal-read-only))))
+    (setq cpp-overlay-list (cons overlay cpp-overlay-list))))
+
+(defun cpp-make-unknown-overlay (start end)
+  ;; Create an overlay for an unknown cpp command from START to END.
+  (let ((overlay (make-overlay start end)))
+    (cond ((eq cpp-unknown-face 'invisible)
+           (cpp-make-overlay-hidden overlay))
+          ((eq cpp-unknown-face 'default))
+          (t 
+           (overlay-put overlay 'face cpp-unknown-face)))
+    (if cpp-unknown-writable
+        ()
+      (overlay-put overlay 'modification-hooks '(cpp-signal-read-only))
+      (overlay-put overlay 'insert-in-front-hooks '(cpp-signal-read-only)))
+    (setq cpp-overlay-list (cons overlay cpp-overlay-list))))
+
+(defun cpp-make-overlay-hidden (overlay)
+  ;; Make overlay hidden and intangible.
+  (overlay-put overlay 'invisible t)
+  (overlay-put overlay 'intangible t)
+  ;; Unfortunately `intangible' is not implemented for overlays yet,
+  ;; so we make is read-only instead.
+  (overlay-put overlay 'modification-hooks '(cpp-signal-read-only)))
+
+(defun cpp-make-overlay-read-only (overlay)
+  ;; Make overlay read only.
+  (overlay-put overlay 'modification-hooks '(cpp-signal-read-only))
+  (overlay-put overlay 'insert-in-front-hooks '(cpp-signal-read-only))
+  (overlay-put overlay 'insert-behind-hooks '(cpp-signal-read-only)))
+
+(defun cpp-make-overlay-sticky (overlay)
+  ;; Make OVERLAY grow when you insert text at either end.
+  (overlay-put overlay 'insert-in-front-hooks '(cpp-grow-overlay))
+  (overlay-put overlay 'insert-behind-hooks '(cpp-grow-overlay)))
+
+(defun cpp-signal-read-only (overlay start end)
+  ;; Only allow deleting the whole overlay.
+  ;; Trying to change a read-only overlay.
+  (if (or (< (overlay-start overlay) start)
+          (> (overlay-end overlay) end))
+      (error "This text is read only")))
+
+(defun cpp-grow-overlay (overlay start end)
+  ;; Make OVERLAY grow to contain range START to END.
+  (move-overlay overlay
+                (min start (overlay-start overlay))
+                (max end (overlay-end overlay))))
+
+;;; Edit Buffer:
+
+(defvar cpp-edit-list nil
+  "Alist of cpp macros and information about how they should be displayed.
+Each entry is a list with the following elements:
+0. The name of the macro (a string).
+1. Face used for text that is `ifdef' the macro.
+2. Face used for text that is `ifndef' the macro.
+3. `t', `nil', or `both' depending on what text may be edited.")
+
+(defvar cpp-edit-map nil)
+;; Keymap for `cpp-edit-mode'.
+
+(if cpp-edit-map
+    ()
+  (setq cpp-edit-map (make-keymap))
+  (suppress-keymap cpp-edit-map)
+  (define-key cpp-edit-map [ down-mouse-2 ] 'cpp-push-button)
+  (define-key cpp-edit-map [ mouse-2 ] 'ignore)
+  (define-key cpp-edit-map " " 'scroll-up)
+  (define-key cpp-edit-map "\C-?" 'scroll-down)
+  (define-key cpp-edit-map [ delete ] 'scroll-down)
+  (define-key cpp-edit-map "\C-c\C-c" 'cpp-edit-apply)
+  (define-key cpp-edit-map "a" 'cpp-edit-apply)
+  (define-key cpp-edit-map "A" 'cpp-edit-apply)
+  (define-key cpp-edit-map "r" 'cpp-edit-reset)
+  (define-key cpp-edit-map "R" 'cpp-edit-reset)
+  (define-key cpp-edit-map "s" 'cpp-edit-save)
+  (define-key cpp-edit-map "S" 'cpp-edit-save)
+  (define-key cpp-edit-map "l" 'cpp-edit-load)
+  (define-key cpp-edit-map "L" 'cpp-edit-load)
+  (define-key cpp-edit-map "h" 'cpp-edit-home)
+  (define-key cpp-edit-map "H" 'cpp-edit-home)
+  (define-key cpp-edit-map "b" 'cpp-edit-background)
+  (define-key cpp-edit-map "B" 'cpp-edit-background)
+  (define-key cpp-edit-map "k" 'cpp-edit-known)
+  (define-key cpp-edit-map "K" 'cpp-edit-known)
+  (define-key cpp-edit-map "u" 'cpp-edit-unknown)
+  (define-key cpp-edit-map "u" 'cpp-edit-unknown)
+  (define-key cpp-edit-map "t" 'cpp-edit-true)
+  (define-key cpp-edit-map "T" 'cpp-edit-true)
+  (define-key cpp-edit-map "f" 'cpp-edit-false)
+  (define-key cpp-edit-map "F" 'cpp-edit-false)
+  (define-key cpp-edit-map "w" 'cpp-edit-write)
+  (define-key cpp-edit-map "W" 'cpp-edit-write)
+  (define-key cpp-edit-map "X" 'cpp-edit-toggle-known)
+  (define-key cpp-edit-map "x" 'cpp-edit-toggle-known)
+  (define-key cpp-edit-map "Y" 'cpp-edit-toggle-unknown)
+  (define-key cpp-edit-map "y" 'cpp-edit-toggle-unknown)
+  (define-key cpp-edit-map "q" 'bury-buffer)
+  (define-key cpp-edit-map "Q" 'bury-buffer))
+
+(defvar cpp-edit-buffer nil)
+;; Real buffer whose cpp display information we are editing.
+(make-variable-buffer-local 'cpp-edit-buffer)
+
+(defvar cpp-edit-symbols nil)
+;; Symbols defined in the edit buffer.
+(make-variable-buffer-local 'cpp-edit-symbols)
+
+(defun cpp-edit-mode ()
+  "Major mode for editing cpp display information.
+Click on objects to change them.  
+You can also use the keyboard accelerators indicated like this: [K]ey."
+  (kill-all-local-variables)
+  (buffer-disable-undo)
+  (auto-save-mode -1)
+  (setq buffer-read-only t)
+  (setq major-mode 'cpp-edit-mode)
+  (setq mode-name "CPP Edit")
+  (use-local-map cpp-edit-map))
+
+(defun cpp-edit-apply ()
+  "Apply edited display information to original buffer."
+  (interactive)
+  (cpp-edit-home)
+  (cpp-parse-buffer t))
+
+(defun cpp-edit-reset ()
+  "Reset display information from original buffer."
+  (interactive)
+  (let ((buffer (current-buffer))
+        (buffer-read-only nil)
+        (start (window-start))
+        (pos (point))
+        symbols)
+    (set-buffer cpp-edit-buffer)
+    (setq symbols cpp-parse-symbols)
+    (set-buffer buffer)
+    (setq cpp-edit-symbols symbols)
+    (erase-buffer)
+    (insert "CPP Display Information for `")
+    (cpp-make-button (buffer-name cpp-edit-buffer) 'cpp-edit-home)
+    (insert "' ")
+    (cpp-make-button "[H]ome" 'cpp-edit-home)
+    (insert " ")
+    (cpp-make-button "[A]pply" 'cpp-edit-apply)
+    (insert " ")
+    (cpp-make-button "[S]ave" 'cpp-edit-save)
+    (insert " ")
+    (cpp-make-button "[L]oad" 'cpp-edit-load)
+    (insert "\n\nClick mouse-2 on item you want to change or use\n"
+            "keyboard equivalent indicated with brackets like [T]his.\n\n")
+    (insert "[B]ackground: ")
+    (cpp-make-button (car (rassq cpp-face-type cpp-face-type-list))
+                     'cpp-edit-background)
+    (insert "\n[K]nown conditionals: ")
+    (cpp-make-button (cpp-face-name cpp-known-face)
+                     'cpp-edit-known nil t)
+    (insert " [X] ")
+    (cpp-make-button (car (rassq cpp-known-writable cpp-writable-list))
+                     'cpp-edit-toggle-known)
+    (insert "\n[U]nknown conditionals: ")
+    (cpp-make-button (cpp-face-name cpp-unknown-face)
+                     'cpp-edit-unknown nil t)
+    (insert " [Y] ")
+    (cpp-make-button (car (rassq cpp-unknown-writable cpp-writable-list))
+                     'cpp-edit-toggle-unknown)
+    (insert (format "\n\n\n%39s: %14s %14s %7s\n\n" "Expression"
+                    "[T]rue Face" "[F]alse Face" "[W]rite"))
+    (while symbols
+      (let*  ((symbol (car symbols))
+              (entry (assoc symbol cpp-edit-list))
+              (true (nth 1 entry))
+              (false (nth 2 entry))
+              (write (if entry (nth 3 entry) 'both)))
+        (setq symbols (cdr symbols))
+
+        (if (and entry                  ; Make default entries unknown.
+                 (or (null true) (eq true 'default))
+                 (or (null false) (eq false 'default))
+                 (eq write 'both))
+            (setq cpp-edit-list (delq entry cpp-edit-list)
+                  entry nil))
+        
+        (if (> (length symbol) 29)
+            (insert (substring symbol 0 39) ": ")
+          (insert (format "%39s: " symbol)))
+
+        (cpp-make-button (cpp-face-name true)
+                         'cpp-edit-true symbol t 14)
+        (insert " ")
+        (cpp-make-button (cpp-face-name false)
+                         'cpp-edit-false symbol t 14)
+        (insert " ")
+        (cpp-make-button (car (rassq write cpp-branch-list))
+                         'cpp-edit-write symbol nil 6)
+        (insert "\n")))
+    (insert "\n\n")
+    (set-window-start nil start)
+    (goto-char pos)))
+
+(defun cpp-edit-load ()
+  "Load cpp configuration."
+  (interactive)
+  (cond ((file-readable-p ".cpp.el")
+         (load-file ".cpp.el"))
+        ((file-readable-p "~/.cpp.el")
+         (load-file ".cpp.el")))
+  (cpp-edit-reset))
+
+(defun cpp-edit-save ()
+  "Load cpp configuration."
+  (interactive)
+  (require 'pp)
+  (save-excursion
+    (set-buffer cpp-edit-buffer)
+    (let ((buffer (find-file-noselect ".cpp.el")))
+      (set-buffer buffer)
+      (erase-buffer)
+      (pp (list 'setq 'cpp-known-face
+                (list 'quote cpp-known-face)) buffer)
+      (pp (list 'setq 'cpp-unknown-face
+                (list 'quote cpp-unknown-face)) buffer)
+      (pp (list 'setq 'cpp-face-type
+                (list 'quote cpp-face-type)) buffer)
+      (pp (list 'setq 'cpp-known-writable
+                (list 'quote cpp-known-writable)) buffer)
+      (pp (list 'setq 'cpp-unknown-writable
+                (list 'quote cpp-unknown-writable)) buffer)
+      (pp (list 'setq 'cpp-edit-list
+                (list 'quote cpp-edit-list)) buffer)
+      (write-file ".cpp.el"))))
+
+(defun cpp-edit-home ()
+  "Switch back to original buffer."
+  (interactive)
+  (if cpp-button-event
+      (read-event))
+  (pop-to-buffer cpp-edit-buffer))
+
+(defun cpp-edit-background ()
+  "Change default face collection."
+  (interactive)
+  (call-interactively 'cpp-choose-default-face)
+  (cpp-edit-reset))
+
+(defun cpp-edit-known ()
+  "Select default for known conditionals."
+  (interactive)
+  (setq cpp-known-face (cpp-choose-face "Known face" cpp-known-face))
+  (cpp-edit-reset))
+
+(defun cpp-edit-unknown ()
+  "Select default for unknown conditionals."
+  (interactive)
+  (setq cpp-unknown-face (cpp-choose-face "Unknown face" cpp-unknown-face))
+  (cpp-edit-reset))
+
+(defconst cpp-writable-list
+  ;; Names used for the writable property.
+  '(("writable" . t)
+    ("read-only" . nil)))
+
+(defun cpp-edit-toggle-known (arg)
+  "Toggle writable status for known conditionals.
+With optional argument ARG, make them writable iff ARG is positive."
+  (interactive "@P")
+  (if (or (and (null arg) cpp-known-writable)
+          (<= (prefix-numeric-value arg) 0))
+      (setq cpp-known-writable nil)
+    (setq cpp-known-writable t))
+  (cpp-edit-reset))
+
+(defun cpp-edit-toggle-unknown (arg)
+  "Toggle writable status for unknown conditionals.
+With optional argument ARG, make them writable iff ARG is positive."
+  (interactive "@P")
+  (if (or (and (null arg) cpp-unknown-writable)
+          (<= (prefix-numeric-value arg) 0))
+      (setq cpp-unknown-writable nil)
+    (setq cpp-unknown-writable t))
+  (cpp-edit-reset))
+
+(defun cpp-edit-true (symbol face)
+  "Select SYMBOL's true FACE used for highlighting taken conditionals."
+  (interactive
+   (let ((symbol (cpp-choose-symbol)))
+     (list symbol
+           (cpp-choose-face "True face"
+                            (nth 1 (assoc symbol cpp-edit-list))))))
+  (setcar (nthcdr 1 (cpp-edit-list-entry-get-or-create symbol)) face)
+  (cpp-edit-reset))
+
+(defun cpp-edit-false (symbol face)
+  "Select SYMBOL's false FACE used for highlighting untaken conditionals."
+  (interactive
+   (let ((symbol (cpp-choose-symbol)))
+     (list symbol
+           (cpp-choose-face "False face" 
+                            (nth 2 (assoc symbol cpp-edit-list))))))
+  (setcar (nthcdr 2 (cpp-edit-list-entry-get-or-create symbol)) face)
+  (cpp-edit-reset))
+
+(defun cpp-edit-write (symbol branch)
+  "Set which branches of SYMBOL should be writable to BRANCH.
+BRANCH should be either nil (false branch), t (true branch) or 'both."
+  (interactive (list (cpp-choose-symbol) (cpp-choose-branch)))
+  (setcar (nthcdr 3 (cpp-edit-list-entry-get-or-create symbol)) branch)
+  (cpp-edit-reset))
+
+(defun cpp-edit-list-entry-get-or-create (symbol)
+  ;; Return the entry for SYMBOL in `cpp-edit-list'.
+  ;; If it does not exist, create it.
+  (let ((entry (assoc symbol cpp-edit-list)))
+    (or entry
+        (setq entry (list symbol nil nil 'both nil)
+              cpp-edit-list (cons entry cpp-edit-list)))
+    entry))
+
+;;; Prompts:
+
+(defun cpp-choose-symbol ()
+  ;; Choose a symbol if called from keyboard, otherwise use the one clicked on.
+  (if cpp-button-event
+      data
+    (completing-read "Symbol: " (mapcar 'list cpp-edit-symbols) nil t)))
+
+(defconst cpp-branch-list
+  ;; Alist of branches.
+  '(("false" . nil)
+    ("true" . t)
+    ("both" . both)))
+
+(defun cpp-choose-branch ()
+  ;; Choose a branch, either nil, t, or both.
+  (if cpp-button-event
+      (x-popup-menu cpp-button-event
+                    (list "Branch" (cons "Branch" cpp-branch-list)))
+    (cdr (assoc (completing-read "Branch: " cpp-branch-list nil t)
+                cpp-branch-list))))
+
+(defun cpp-choose-face (prompt default)
+  ;; Choose a face from cpp-face-defalt-list.
+  ;; PROMPT is what to say to the user.
+  ;; DEFAULT is the default face.
+  (or (if cpp-button-event
+          (x-popup-menu cpp-button-event
+                        (list prompt (cons prompt cpp-face-default-list)))
+        (let ((name (car (rassq default cpp-face-default-list))))
+          (cdr (assoc (completing-read (if name
+                                           (concat prompt
+                                                   " (default " name "): ")
+                                         (concat prompt ": "))
+                                       cpp-face-default-list nil t)
+                      cpp-face-all-list))))
+      default))
+
+(defconst cpp-face-type-list
+  '(("light color background" . light)
+    ("dark color background" . dark)
+    ("monochrome" . mono)
+    ("tty" . none))
+  "Alist of strings and names of the defined face collections.")
+
+(defun cpp-choose-default-face (type)
+  ;; Choose default face list for screen of TYPE.
+  ;; Type must be one of the types defined in `cpp-face-type-list'.
+  (interactive (list (if cpp-button-event
+                         (x-popup-menu cpp-button-event
+                                       (list "Screen type"
+                                             (cons "Screen type"
+                                                   cpp-face-type-list)))
+                       (cdr (assoc (completing-read "Screen type: "
+                                                    cpp-face-type-list
+                                                    nil t)
+                                   cpp-face-type-list)))))
+  (cond ((null type))
+        ((eq type 'light)
+         (if cpp-face-light-list
+             ()
+           (setq cpp-face-light-list
+                 (mapcar 'cpp-create-bg-face cpp-face-light-name-list))
+           (setq cpp-face-all-list
+                 (append cpp-face-all-list cpp-face-light-list)))
+         (setq cpp-face-type 'light)
+         (setq cpp-face-default-list
+               (append cpp-face-light-list cpp-face-none-list)))
+        ((eq type 'dark)
+         (if cpp-face-dark-list
+             ()
+           (setq cpp-face-dark-list
+                 (mapcar 'cpp-create-bg-face cpp-face-dark-name-list))
+           (setq cpp-face-all-list
+                 (append cpp-face-all-list cpp-face-dark-list)))
+         (setq cpp-face-type 'dark)
+         (setq cpp-face-default-list
+               (append cpp-face-dark-list cpp-face-none-list)))
+        ((eq type 'mono)
+         (setq cpp-face-type 'mono)
+         (setq cpp-face-default-list
+               (append cpp-face-mono-list cpp-face-none-list)))
+        (t
+         (setq cpp-face-type 'none)
+         (setq cpp-face-default-list cpp-face-none-list))))
+
+;;; Buttons:
+
+(defvar cpp-button-event nil)
+;; This will be t in the callback for `cpp-make-button'.
+
+(defun cpp-make-button (name callback &optional data face padding)
+  ;; Create a button at point.
+  ;; NAME is the name of the button.
+  ;; CALLBACK is the function to call when the button is pushed.
+  ;; DATA will be available to CALLBACK as a free variable.
+  ;; FACE means that NAME is the name of a face in `cpp-face-all-list'.
+  ;; PADDING means NAME will be right justified at that length.
+  (let ((name (format "%s" name))
+        from to)
+    (cond ((null padding)
+           (setq from (point))
+           (insert name))
+          ((> (length name) padding)
+           (setq from (point))
+           (insert (substring name 0 padding)))
+          (t
+           (insert (make-string (- padding (length name)) ? ))
+           (setq from (point))
+           (insert name)))
+    (setq to (point))
+    (setq face
+          (if face
+              (let ((check (cdr (assoc name cpp-face-all-list))))
+                (if (memq check '(default invisible))
+                    'bold
+                  check))
+            'bold))
+    (add-text-properties from to
+                         (append (list 'face face)
+                                 '(mouse-face highlight)
+                                 (list 'cpp-callback callback)
+                                 (if data (list 'cpp-data data))))))
+
+(defun cpp-push-button (event)
+  ;; Pushed a CPP button.
+  (interactive "@e")
+  (set-buffer (window-buffer (posn-window (event-start event))))
+  (let ((pos (posn-point (event-start event))))
+    (let ((data (get-text-property pos 'cpp-data))
+          (fun (get-text-property pos 'cpp-callback))
+          (cpp-button-event event))
+      (cond (fun
+             (call-interactively (get-text-property pos 'cpp-callback)))
+            ((lookup-key global-map [ down-mouse-2])
+             (call-interactively (lookup-key global-map [ down-mouse-2])))))))
+
+;;; Faces:
+
+(defvar cpp-face-light-name-list
+  '("light gray" "light blue" "light cyan" "light yellow" "light pink"
+    "pale green" "beige" "orange" "magenta" "violet" "medium purple"
+    "turquoise")
+  "Background colours useful with dark foreground colors.")
+
+(defvar cpp-face-dark-name-list
+  '("dim gray" "blue" "cyan" "yellow" "red"
+    "dark green" "brown" "dark orange" "dark khaki" "dark violet" "purple"
+    "dark turquoise")
+  "Background colours useful with light foreground colors.")
+
+(defvar cpp-face-light-list nil
+  "Alist of names and faces to be used for light backgrounds.")
+
+(defvar cpp-face-dark-list nil
+  "Alist of names and faces to be used for dark backgrounds.")
+
+(defvar cpp-face-mono-list
+  '(("bold" . 'bold)
+    ("bold-italic" . 'bold-italic)
+    ("italic" . 'italic)
+    ("underline" . 'underline))
+  "Alist of names and faces to be used for monocrome screens.")
+
+(defvar cpp-face-none-list
+   '(("default" . default)
+     ("invisible" . invisible))
+   "Alist of names and faces available even if you don't use a window system.")
+
+(defvar cpp-face-all-list
+  (append cpp-face-light-list
+          cpp-face-dark-list
+          cpp-face-mono-list
+          cpp-face-none-list)
+  "All faces used for highligting text inside cpp conditionals.")
+
+(defvar cpp-face-default-list nil
+  "List of faces you can choose from for cpp conditionals.")
+
+(defun cpp-create-bg-face (color)
+  ;; Create entry for face with background COLOR.
+  (let ((name (intern (concat "cpp " color))))
+    (make-face name)
+    (set-face-background name color)
+    (cons color name)))
+
+(cpp-choose-default-face (if window-system cpp-face-type 'none))
+
+(defun cpp-face-name (face)
+  ;; Return the name of FACE from `cpp-face-all-list'.
+  (let ((entry (rassq (if face face 'default) cpp-face-all-list)))
+    (if entry
+        (car entry)
+      (format "<%s>" face))))
+
+;;; Utilities:
+
+(defvar cpp-progress-time 0)
+;; Last time we issued a progress message.
+
+(defun cpp-progress-message (&rest args)
+  ;; Report progress at most once a second.  Take same ARGS as `message'.
+  (let ((time (nth 1 (current-time))))
+    (if (= time cpp-progress-time)
+        ()
+      (setq cpp-progress-time time)
+      (apply 'message args))))
+
+(provide 'cpp)
+
+;;; cpp.el ends here
+