root/trunk/lisp/textmodes/sgml-mode.el

;;; sgml-mode.el --- SGML- and HTML-editing modes -*- coding: iso-2022-7bit -*-

;; Copyright (C) 1992, 1995, 1996, 1998, 2001, 2002, 2003, 2004,
;;   2005, 2006, 2007, 2008 Free Software Foundation, Inc.

;; Author: James Clark <jjc@jclark.com>
;; Maintainer: FSF
;; Adapted-By: ESR, Daniel Pfeiffer <occitan@esperanto.org>,
;;             F.Potorti@cnuce.cnr.it
;; Keywords: wp, hypermedia, comm, languages

;; 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 3, 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., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.

;;; Commentary:

;; Configurable major mode for editing document in the SGML standard general
;; markup language.  As an example contains a mode for editing the derived
;; HTML hypertext markup language.

;;; Code:

(eval-when-compile
  (require 'skeleton)
  (require 'outline)
  (require 'cl))

(defgroup sgml nil
  "SGML editing mode."
  :link '(custom-group-link :tag "Font Lock Faces group" font-lock-faces)
  :group 'languages)

(defcustom sgml-basic-offset 2
  "*Specifies the basic indentation level for `sgml-indent-line'."
  :type 'integer
  :group 'sgml)

(defcustom sgml-transformation-function 'identity
  "*Default value for `skeleton-transformation-function' in SGML mode."
  :type 'function
  :group 'sgml)

(put 'sgml-transformation-function 'variable-interactive
     "aTransformation function: ")
(defvaralias 'sgml-transformation 'sgml-transformation-function)

(defcustom sgml-mode-hook nil
  "Hook run by command `sgml-mode'.
`text-mode-hook' is run first."
  :group 'sgml
  :type 'hook)

;; As long as Emacs' syntax can't be complemented with predicates to context
;; sensitively confirm the syntax of characters, we have to live with this
;; kludgy kind of tradeoff.
(defvar sgml-specials '(?\")
  "List of characters that have a special meaning for SGML mode.
This list is used when first loading the `sgml-mode' library.
The supported characters and potential disadvantages are:

  ?\\\" Makes \" in text start a string.
  ?'    Makes ' in text start a string.
  ?-    Makes -- in text start a comment.

When only one of ?\\\" or ?' are included, \"'\" or '\"', as can be found in
DTDs, start a string.  To partially avoid this problem this also makes these
self insert as named entities depending on `sgml-quick-keys'.

Including ?- has the problem of affecting dashes that have nothing to do
with comments, so we normally turn it off.")

(defvar sgml-quick-keys nil
  "Use <, >, &, /, SPC and `sgml-specials' keys \"electrically\" when non-nil.
This takes effect when first loading the `sgml-mode' library.")

(defvar sgml-mode-map
  (let ((map (make-keymap))     ;`sparse' doesn't allow binding to charsets.
        (menu-map (make-sparse-keymap "SGML")))
    (define-key map "\C-c\C-i" 'sgml-tags-invisible)
    (define-key map "/" 'sgml-slash)
    (define-key map "\C-c\C-n" 'sgml-name-char)
    (define-key map "\C-c\C-t" 'sgml-tag)
    (define-key map "\C-c\C-a" 'sgml-attributes)
    (define-key map "\C-c\C-b" 'sgml-skip-tag-backward)
    (define-key map [?\C-c left] 'sgml-skip-tag-backward)
    (define-key map "\C-c\C-f" 'sgml-skip-tag-forward)
    (define-key map [?\C-c right] 'sgml-skip-tag-forward)
    (define-key map "\C-c\C-d" 'sgml-delete-tag)
    (define-key map "\C-c\^?" 'sgml-delete-tag)
    (define-key map "\C-c?" 'sgml-tag-help)
    (define-key map "\C-c/" 'sgml-close-tag)
    (define-key map "\C-c8" 'sgml-name-8bit-mode)
    (define-key map "\C-c\C-v" 'sgml-validate)
    (when sgml-quick-keys
      (define-key map "&" 'sgml-name-char)
      (define-key map "<" 'sgml-tag)
      (define-key map " " 'sgml-auto-attributes)
      (define-key map ">" 'sgml-maybe-end-tag)
      (when (memq ?\" sgml-specials)
        (define-key map "\"" 'sgml-name-self))
      (when (memq ?' sgml-specials)
        (define-key map "'" 'sgml-name-self)))
    (define-key map (vector (make-char 'latin-iso8859-1))
      'sgml-maybe-name-self)
    (let ((c 127)
          (map (nth 1 map)))
      (while (< (setq c (1+ c)) 256)
        (aset map c 'sgml-maybe-name-self)))
    (define-key map [menu-bar sgml] (cons "SGML" menu-map))
    (define-key menu-map [sgml-validate] '("Validate" . sgml-validate))
    (define-key menu-map [sgml-name-8bit-mode]
      '("Toggle 8 Bit Insertion" . sgml-name-8bit-mode))
    (define-key menu-map [sgml-tags-invisible]
      '("Toggle Tag Visibility" . sgml-tags-invisible))
    (define-key menu-map [sgml-tag-help]
      '("Describe Tag" . sgml-tag-help))
    (define-key menu-map [sgml-delete-tag]
      '("Delete Tag" . sgml-delete-tag))
    (define-key menu-map [sgml-skip-tag-forward]
      '("Forward Tag" . sgml-skip-tag-forward))
    (define-key menu-map [sgml-skip-tag-backward]
      '("Backward Tag" . sgml-skip-tag-backward))
    (define-key menu-map [sgml-attributes]
      '("Insert Attributes" . sgml-attributes))
    (define-key menu-map [sgml-tag] '("Insert Tag" . sgml-tag))
    map)
  "Keymap for SGML mode.  See also `sgml-specials'.")

(defun sgml-make-syntax-table (specials)
  (let ((table (make-syntax-table text-mode-syntax-table)))
    (modify-syntax-entry ?< "(>" table)
    (modify-syntax-entry ?> ")<" table)
    (modify-syntax-entry ?: "_" table)
    (modify-syntax-entry ?_ "_" table)
    (modify-syntax-entry ?. "_" table)
    (if (memq ?- specials)
        (modify-syntax-entry ?- "_ 1234" table))
    (if (memq ?\" specials)
        (modify-syntax-entry ?\" "\"\"" table))
    (if (memq ?' specials)
        (modify-syntax-entry ?\' "\"'" table))
    table))

(defvar sgml-mode-syntax-table (sgml-make-syntax-table sgml-specials)
  "Syntax table used in SGML mode.  See also `sgml-specials'.")

(defconst sgml-tag-syntax-table
  (let ((table (sgml-make-syntax-table '(?- ?\" ?\'))))
    (dolist (char '(?\( ?\) ?\{ ?\} ?\[ ?\] ?$ ?% ?& ?* ?+ ?/))
      (modify-syntax-entry char "." table))
    table)
  "Syntax table used to parse SGML tags.")

(defcustom sgml-name-8bit-mode nil
  "*When non-nil, insert non-ASCII characters as named entities."
  :type 'boolean
  :group 'sgml)

(defvar sgml-char-names
  [nil nil nil nil nil nil nil nil
   nil nil nil nil nil nil nil nil
   nil nil nil nil nil nil nil nil
   nil nil nil nil nil nil nil nil
   "nbsp" "excl" "quot" "num" "dollar" "percnt" "amp" "apos"
   "lpar" "rpar" "ast" "plus" "comma" "hyphen" "period" "sol"
   nil nil nil nil nil nil nil nil
   nil nil "colon" "semi" "lt" "eq" "gt" "quest"
   "commat" nil nil nil nil nil nil nil
   nil nil nil nil nil nil nil nil
   nil nil nil nil nil nil nil nil
   nil nil nil "lsqb" nil "rsqb" "uarr" "lowbar"
   "lsquo" nil nil nil nil nil nil nil
   nil nil nil nil nil nil nil nil
   nil nil nil nil nil nil nil nil
   nil nil nil "lcub" "verbar" "rcub" "tilde" nil
   nil nil nil nil nil nil nil nil
   nil nil nil nil nil nil nil nil
   nil nil nil nil nil nil nil nil
   nil nil nil nil nil nil nil nil
   "nbsp" "iexcl" "cent" "pound" "curren" "yen" "brvbar" "sect"
   "uml" "copy" "ordf" "laquo" "not" "shy" "reg" "macr"
   "ring" "plusmn" "sup2" "sup3" "acute" "micro" "para" "middot"
   "cedil" "sup1" "ordm" "raquo" "frac14" "frac12" "frac34" "iquest"
   "Agrave" "Aacute" "Acirc" "Atilde" "Auml" "Aring" "AElig" "Ccedil"
   "Egrave" "Eacute" "Ecirc" "Euml" "Igrave" "Iacute" "Icirc" "Iuml"
   "ETH" "Ntilde" "Ograve" "Oacute" "Ocirc" "Otilde" "Ouml" nil
   "Oslash" "Ugrave" "Uacute" "Ucirc" "Uuml" "Yacute" "THORN" "szlig"
   "agrave" "aacute" "acirc" "atilde" "auml" "aring" "aelig" "ccedil"
   "egrave" "eacute" "ecirc" "euml" "igrave" "iacute" "icirc" "iuml"
   "eth" "ntilde" "ograve" "oacute" "ocirc" "otilde" "ouml" "divide"
   "oslash" "ugrave" "uacute" "ucirc" "uuml" "yacute" "thorn" "yuml"]
  "Vector of symbolic character names without `&' and `;'.")

(put 'sgml-table 'char-table-extra-slots 0)

(defvar sgml-char-names-table
  (let ((table (make-char-table 'sgml-table))
        (i 32)
        elt)
    (while (< i 256)
      (setq elt (aref sgml-char-names i))
      (if elt (aset table (make-char 'latin-iso8859-1 i) elt))
      (setq i (1+ i)))
    table)
  "A table for mapping non-ASCII characters into SGML entity names.
Currently, only Latin-1 characters are supported.")

;; nsgmls is a free SGML parser in the SP suite available from
;; ftp.jclark.com and otherwise packaged for GNU systems.
;; Its error messages can be parsed by next-error.
;; The -s option suppresses output.

(defcustom sgml-validate-command "nsgmls -s" ; replaced old `sgmls'
  "*The command to validate an SGML document.
The file name of current buffer file name will be appended to this,
separated by a space."
  :type 'string
  :version "21.1"
  :group 'sgml)

(defvar sgml-saved-validate-command nil
  "The command last used to validate in this buffer.")

;; I doubt that null end tags are used much for large elements,
;; so use a small distance here.
(defcustom sgml-slash-distance 1000
  "*If non-nil, is the maximum distance to search for matching `/'."
  :type '(choice (const nil) integer)
  :group 'sgml)

(defconst sgml-namespace-re "[_[:alpha:]][-_.[:alnum:]]*")
(defconst sgml-name-re "[_:[:alpha:]][-_.:[:alnum:]]*")
(defconst sgml-tag-name-re (concat "<\\([!/?]?" sgml-name-re "\\)"))
(defconst sgml-attrs-re "\\(?:[^\"'/><]\\|\"[^\"]*\"\\|'[^']*'\\)*")
(defconst sgml-start-tag-regex (concat "<" sgml-name-re sgml-attrs-re)
  "Regular expression that matches a non-empty start tag.
Any terminating `>' or `/' is not matched.")

(defface sgml-namespace
  '((t (:inherit font-lock-builtin-face)))
  "`sgml-mode' face used to highlight the namespace part of identifiers."
  :group 'sgml)
(defvar sgml-namespace-face 'sgml-namespace)

;; internal
(defconst sgml-font-lock-keywords-1
  `((,(concat "<\\([!?]" sgml-name-re "\\)") 1 font-lock-keyword-face)
    ;; We could use the simpler "\\(" sgml-namespace-re ":\\)?" instead,
    ;; but it would cause a bit more backtracking in the re-matcher.
    (,(concat "</?\\(" sgml-namespace-re "\\)\\(?::\\(" sgml-name-re "\\)\\)?")
     (1 (if (match-end 2) sgml-namespace-face font-lock-function-name-face))
     (2 font-lock-function-name-face nil t))
    ;; FIXME: this doesn't cover the variables using a default value.
    ;; The first shy-group is an important anchor: it prevents an O(n^2)
    ;; pathological case where we otherwise keep retrying a failing match
    ;; against a very long word at every possible position within the word.
    (,(concat "\\(?:^\\|[ \t]\\)\\(" sgml-namespace-re "\\)\\(?::\\("
              sgml-name-re "\\)\\)?=[\"']")
     (1 (if (match-end 2) sgml-namespace-face font-lock-variable-name-face))
     (2 font-lock-variable-name-face nil t))
    (,(concat "[&%]" sgml-name-re ";?") . font-lock-variable-name-face)))

(defconst sgml-font-lock-keywords-2
  (append
   sgml-font-lock-keywords-1
   '((eval
      . (cons (concat "<"
                      (regexp-opt (mapcar 'car sgml-tag-face-alist) t)
                      "\\([ \t][^>]*\\)?>\\([^<]+\\)</\\1>")
              '(3 (cdr (assoc (downcase (match-string 1))
                              sgml-tag-face-alist)) prepend))))))

;; for font-lock, but must be defvar'ed after
;; sgml-font-lock-keywords-1 and sgml-font-lock-keywords-2 above
(defvar sgml-font-lock-keywords sgml-font-lock-keywords-1
  "*Rules for highlighting SGML code.  See also `sgml-tag-face-alist'.")

(defvar sgml-font-lock-syntactic-keywords
  ;; Use the `b' style of comments to avoid interference with the -- ... --
  ;; comments recognized when `sgml-specials' includes ?-.
  ;; FIXME: beware of <!--> blabla <!--> !!
  '(("\\(<\\)!--" (1 "< b"))
    ("--[ \t\n]*\\(>\\)" (1 "> b")))
  "Syntactic keywords for `sgml-mode'.")

;; internal
(defvar sgml-face-tag-alist ()
  "Alist of face and tag name for facemenu.")

(defvar sgml-tag-face-alist ()
  "Tag names and face or list of faces to fontify with when invisible.
When `font-lock-maximum-decoration' is 1 this is always used for fontifying.
When more these are fontified together with `sgml-font-lock-keywords'.")

(defvar sgml-display-text ()
  "Tag names as lowercase symbols, and display string when invisible.")

;; internal
(defvar sgml-tags-invisible nil)

(defcustom sgml-tag-alist
  '(("![" ("ignore" t) ("include" t))
    ("!attlist")
    ("!doctype")
    ("!element")
    ("!entity"))
  "*Alist of tag names for completing read and insertion rules.
This alist is made up as

  ((\"tag\" . TAGRULE)
   ...)

TAGRULE is a list of optionally t (no endtag) or `\\n' (separate endtag by
newlines) or a skeleton with nil, t or `\\n' in place of the interactor
followed by an ATTRIBUTERULE (for an always present attribute) or an
attribute alist.

The attribute alist is made up as

  ((\"attribute\" . ATTRIBUTERULE)
   ...)

ATTRIBUTERULE is a list of optionally t (no value when no input) followed by
an optional alist of possible values."
  :type '(repeat (cons (string :tag "Tag Name")
                       (repeat :tag "Tag Rule" sexp)))
  :group 'sgml)
(put 'sgml-tag-alist 'risky-local-variable t)

(defcustom sgml-tag-help
  '(("!" . "Empty declaration for comment")
    ("![" . "Embed declarations with parser directive")
    ("!attlist" . "Tag attributes declaration")
    ("!doctype" . "Document type (DTD) declaration")
    ("!element" . "Tag declaration")
    ("!entity" . "Entity (macro) declaration"))
  "*Alist of tag name and short description."
  :type '(repeat (cons (string :tag "Tag Name")
                       (string :tag "Description")))
  :group 'sgml)

(defcustom sgml-xml-mode nil
  "*When non-nil, tag insertion functions will be XML-compliant.
If this variable is customized, the custom value is used always.
Otherwise, it is set to be buffer-local when the file has
a DOCTYPE or an XML declaration."
  :type 'boolean
  :version "22.1"
  :group 'sgml)

(defvar sgml-empty-tags nil
  "List of tags whose !ELEMENT definition says EMPTY.")

(defvar sgml-unclosed-tags nil
  "List of tags whose !ELEMENT definition says the end-tag is optional.")

(defun sgml-xml-guess ()
  "Guess whether the current buffer is XML."
  (save-excursion
    (goto-char (point-min))
    (when (or (string= "xml" (file-name-extension (or buffer-file-name "")))
              (looking-at "\\s-*<\\?xml")
              (when (re-search-forward
                     (eval-when-compile
                 (mapconcat 'identity
                            '("<!DOCTYPE" "\\(\\w+\\)" "\\(\\w+\\)"
                                    "\"\\([^\"]+\\)\"" "\"\\([^\"]+\\)\"")
                                  "\\s-+"))
                     nil t)
                (string-match "X\\(HT\\)?ML" (match-string 3))))
      (set (make-local-variable 'sgml-xml-mode) t))))

(defvar v2)                             ; free for skeleton

(defun sgml-comment-indent-new-line (&optional soft)
  (let ((comment-start "-- ")
        (comment-start-skip "\\(<!\\)?--[ \t]*")
        (comment-end " --")
        (comment-style 'plain))
    (comment-indent-new-line soft)))

(defun sgml-mode-facemenu-add-face-function (face end)
  (if (setq face (cdr (assq face sgml-face-tag-alist)))
      (progn
        (setq face (funcall skeleton-transformation-function face))
        (setq facemenu-end-add-face (concat "</" face ">"))
        (concat "<" face ">"))
    (error "Face not configured for %s mode" mode-name)))

(defun sgml-fill-nobreak ()
  ;; Don't break between a tag name and its first argument.
  (save-excursion
    (skip-chars-backward " \t")
    (and (not (zerop (skip-syntax-backward "w_")))
         (skip-chars-backward "/?!")
         (eq (char-before) ?<))))

;;;###autoload
(define-derived-mode sgml-mode text-mode "SGML"
  "Major mode for editing SGML documents.
Makes > match <.
Keys <, &, SPC within <>, \", / and ' can be electric depending on
`sgml-quick-keys'.

An argument of N to a tag-inserting command means to wrap it around
the next N words.  In Transient Mark mode, when the mark is active,
N defaults to -1, which means to wrap it around the current region.

If you like upcased tags, put (setq sgml-transformation-function 'upcase)
in your `.emacs' file.

Use \\[sgml-validate] to validate your document with an SGML parser.

Do \\[describe-variable] sgml- SPC to see available variables.
Do \\[describe-key] on the following bindings to discover what they do.
\\{sgml-mode-map}"
  (make-local-variable 'sgml-saved-validate-command)
  (make-local-variable 'facemenu-end-add-face)
  ;;(make-local-variable 'facemenu-remove-face-function)
  ;; A start or end tag by itself on a line separates a paragraph.
  ;; This is desirable because SGML discards a newline that appears
  ;; immediately after a start tag or immediately before an end tag.
  (set (make-local-variable 'paragraph-start) (concat "[ \t]*$\\|\
\[ \t]*</?\\(" sgml-name-re sgml-attrs-re "\\)?>"))
  (set (make-local-variable 'paragraph-separate)
       (concat paragraph-start "$"))
  (set (make-local-variable 'adaptive-fill-regexp) "[ \t]*")
  (add-hook 'fill-nobreak-predicate 'sgml-fill-nobreak nil t)
  (set (make-local-variable 'indent-line-function) 'sgml-indent-line)
  (set (make-local-variable 'comment-start) "<!-- ")
  (set (make-local-variable 'comment-end) " -->")
  (set (make-local-variable 'comment-indent-function) 'sgml-comment-indent)
  (set (make-local-variable 'comment-line-break-function)
       'sgml-comment-indent-new-line)
  (set (make-local-variable 'skeleton-further-elements)
       '((completion-ignore-case t)))
  (set (make-local-variable 'skeleton-end-hook)
       (lambda ()
         (or (eolp)
             (not (or (eq v2 '\n) (eq (car-safe v2) '\n)))
             (newline-and-indent))))
  (set (make-local-variable 'font-lock-defaults)
       '((sgml-font-lock-keywords
          sgml-font-lock-keywords-1
          sgml-font-lock-keywords-2)
         nil t nil nil
         (font-lock-syntactic-keywords
          . sgml-font-lock-syntactic-keywords)))
  (set (make-local-variable 'facemenu-add-face-function)
       'sgml-mode-facemenu-add-face-function)
  (sgml-xml-guess)
  (if sgml-xml-mode
      (setq mode-name "XML")
    (set (make-local-variable 'skeleton-transformation-function)
         sgml-transformation-function))
  ;; This will allow existing comments within declarations to be
  ;; recognized.
  ;; I can't find a clear description of SGML/XML comments, but it seems that
  ;; the only reliable ones are <!-- ... --> although it's not clear what
  ;; "..." can contain.  It used to accept -- ... -- as well, but that was
  ;; apparently a mistake.
  (set (make-local-variable 'comment-start-skip) "<!--[ \t]*")
  (set (make-local-variable 'comment-end-skip) "[ \t]*--[ \t\n]*>")
  ;; This definition has an HTML leaning but probably fits well for other modes.
  (setq imenu-generic-expression
        `((nil
           ,(concat "<!\\(element\\|entity\\)[ \t\n]+%?[ \t\n]*\\("
                    sgml-name-re "\\)")
           2)
          ("Id"
           ,(concat "<[^>]+[ \t\n]+[Ii][Dd]=\\(['\"]"
                    (if sgml-xml-mode "" "?")
                    "\\)\\(" sgml-name-re "\\)\\1")
           2)
          ("Name"
           ,(concat "<[^>]+[ \t\n]+[Nn][Aa][Mm][Ee]=\\(['\"]"
                    (if sgml-xml-mode "" "?")
                    "\\)\\(" sgml-name-re "\\)\\1")
           2))))

;; Some programs (such as Glade 2) generate XML which has
;; -*- mode: xml -*-.
;;;###autoload
(defalias 'xml-mode 'sgml-mode)

(defun sgml-comment-indent ()
  (if (looking-at "--") comment-column 0))

(defun sgml-slash (arg)
  "Insert ARG slash characters.
Behaves electrically if `sgml-quick-keys' is non-nil."
  (interactive "p")
  (cond
   ((not (and (eq (char-before) ?<) (= arg 1)))
    (sgml-slash-matching arg))
   ((eq sgml-quick-keys 'indent)
    (insert-char ?/ 1)
    (indent-according-to-mode))
   ((eq sgml-quick-keys 'close)
    (delete-backward-char 1)
    (sgml-close-tag))
   (t
    (sgml-slash-matching arg))))

(defun sgml-slash-matching (arg)
  "Insert `/' and display any previous matching `/'.
Two `/'s are treated as matching if the first `/' ends a net-enabling
start tag, and the second `/' is the corresponding null end tag."
  (interactive "p")
  (insert-char ?/ arg)
  (if (> arg 0)
      (let ((oldpos (point))
            (blinkpos)
            (level 0))
        (save-excursion
          (save-restriction
            (if sgml-slash-distance
                (narrow-to-region (max (point-min)
                                       (- (point) sgml-slash-distance))
                                  oldpos))
            (if (and (re-search-backward sgml-start-tag-regex (point-min) t)
                     (eq (match-end 0) (1- oldpos)))
                ()
              (goto-char (1- oldpos))
              (while (and (not blinkpos)
                          (search-backward "/" (point-min) t))
                (let ((tagend (save-excursion
                                (if (re-search-backward sgml-start-tag-regex
                                                        (point-min) t)
                                    (match-end 0)
                                  nil))))
                  (if (eq tagend (point))
                      (if (eq level 0)
                          (setq blinkpos (point))
                        (setq level (1- level)))
                    (setq level (1+ level)))))))
          (when blinkpos
            (goto-char blinkpos)
            (if (pos-visible-in-window-p)
                (sit-for 1)
              (message "Matches %s"
                       (buffer-substring (line-beginning-position)
                                         (1+ blinkpos)))))))))

;; Why doesn't this use the iso-cvt table or, preferably, generate the
;; inverse of the extensive table in the SGML Quail input method?  -- fx
;; I guess that's moot since it only works with Latin-1 anyhow.
(defun sgml-name-char (&optional char)
  "Insert a symbolic character name according to `sgml-char-names'.
Non-ASCII chars may be inserted either with the meta key, as in M-SPC for
no-break space or M-- for a soft hyphen; or via an input method or
encoded keyboard operation."
  (interactive "*")
  (insert ?&)
  (or char
      (setq char (read-quoted-char "Enter char or octal number")))
  (delete-backward-char 1)
  (insert char)
  (undo-boundary)
  (sgml-namify-char))

(defun sgml-namify-char ()
  "Change the char before point into its `&name;' equivalent.
Uses `sgml-char-names'."
  (interactive)
  (let* ((char (char-before))
         (name
          (cond
           ((null char) (error "No char before point"))
           ((< char 256) (or (aref sgml-char-names char) char))
           ((aref sgml-char-names-table char))
           ((encode-char char 'ucs)))))
    (if (not name)
        (error "Don't know the name of `%c'" char)
      (delete-backward-char 1)
      (insert (format (if (numberp name) "&#%d;" "&%s;") name)))))

(defun sgml-name-self ()
  "Insert a symbolic character name according to `sgml-char-names'."
  (interactive "*")
  (sgml-name-char last-command-char))

(defun sgml-maybe-name-self ()
  "Insert a symbolic character name according to `sgml-char-names'."
  (interactive "*")
  (if sgml-name-8bit-mode
      (let ((mc last-command-char))
        (if (< mc 256)
            (setq mc (unibyte-char-to-multibyte mc)))
        (or mc (setq mc last-command-char))
        (sgml-name-char mc))
    (self-insert-command 1)))

(defun sgml-name-8bit-mode ()
  "Toggle whether to insert named entities instead of non-ASCII characters.
This only works for Latin-1 input."
  (interactive)
  (setq sgml-name-8bit-mode (not sgml-name-8bit-mode))
  (message "sgml name entity mode is now %s"
           (if sgml-name-8bit-mode "ON" "OFF")))

;; When an element of a skeleton is a string "str", it is passed
;; through `skeleton-transformation-function' and inserted.
;; If "str" is to be inserted literally, one should obtain it as
;; the return value of a function, e.g. (identity "str").

(defvar sgml-tag-last nil)
(defvar sgml-tag-history nil)
(define-skeleton sgml-tag
  "Prompt for a tag and insert it, optionally with attributes.
Completion and configuration are done according to `sgml-tag-alist'.
If you like tags and attributes in uppercase do \\[set-variable]
`skeleton-transformation-function' RET `upcase' RET, or put this
in your `.emacs':
  (setq sgml-transformation-function 'upcase)"
  (funcall (or skeleton-transformation-function 'identity)
           (setq sgml-tag-last
                 (completing-read
                  (if (> (length sgml-tag-last) 0)
                      (format "Tag (default %s): " sgml-tag-last)
                    "Tag: ")
                  sgml-tag-alist nil nil nil 'sgml-tag-history sgml-tag-last)))
  ?< str |
  (("") -1 '(undo-boundary) (identity "&lt;")) |        ; see comment above
  `(("") '(setq v2 (sgml-attributes ,str t)) ?>
    (cond
     ((string= "![" ,str)
      (backward-char)
      '(("") " [ " _ " ]]"))
     ((and (eq v2 t) sgml-xml-mode (member ,str sgml-empty-tags))
      '(("") -1 " />"))
     ((or (and (eq v2 t) (not sgml-xml-mode)) (string-match "^[/!?]" ,str))
      nil)
     ((symbolp v2)
      ;; Make sure we don't fall into an infinite loop.
      ;; For xhtml's `tr' tag, we should maybe use \n instead.
      (if (eq v2 t) (setq v2 nil))
      ;; We use `identity' to prevent skeleton from passing
      ;; `str' through `skeleton-transformation-function' a second time.
      '(("") v2 _ v2 "</" (identity ',str) ?>))
     ((eq (car v2) t)
      (cons '("") (cdr v2)))
     (t
      (append '(("") (car v2))
              (cdr v2)
              '(resume: (car v2) _ "</" (identity ',str) ?>))))))

(autoload 'skeleton-read "skeleton")

(defun sgml-attributes (tag &optional quiet)
  "When at top level of a tag, interactively insert attributes.

Completion and configuration of TAG are done according to `sgml-tag-alist'.
If QUIET, do not print a message when there are no attributes for TAG."
  (interactive (list (save-excursion (sgml-beginning-of-tag t))))
  (or (stringp tag) (error "Wrong context for adding attribute"))
  (if tag
      (let ((completion-ignore-case t)
            (alist (cdr (assoc (downcase tag) sgml-tag-alist)))
            car attribute i)
        (if (or (symbolp (car alist))
                (symbolp (car (car alist))))
            (setq car (car alist)
                  alist (cdr alist)))
        (or quiet
            (message "No attributes configured."))
        (if (stringp (car alist))
            (progn
              (insert (if (eq (preceding-char) ?\s) "" ?\s)
                      (funcall skeleton-transformation-function (car alist)))
              (sgml-value alist))
          (setq i (length alist))
          (while (> i 0)
            (insert ?\s)
            (insert (funcall skeleton-transformation-function
                             (setq attribute
                                   (skeleton-read '(completing-read
                                                    "Attribute: "
                                                    alist)))))
            (if (string= "" attribute)
                (setq i 0)
              (sgml-value (assoc (downcase attribute) alist))
              (setq i (1- i))))
          (if (eq (preceding-char) ?\s)
              (delete-backward-char 1)))
        car)))

(defun sgml-auto-attributes (arg)
  "Self insert the character typed; at top level of tag, prompt for attributes.
With prefix argument, only self insert."
  (interactive "*P")
  (let ((point (point))
        tag)
    (if (or arg
            (not sgml-tag-alist)        ; no message when nothing configured
            (symbolp (setq tag (save-excursion (sgml-beginning-of-tag t))))
            (eq (aref tag 0) ?/))
        (self-insert-command (prefix-numeric-value arg))
      (sgml-attributes tag)
      (setq last-command-char ?\s)
      (or (> (point) point)
          (self-insert-command 1)))))

(defun sgml-tag-help (&optional tag)
  "Display description of tag TAG.  If TAG is omitted, use the tag at point."
  (interactive)
  (or tag
      (save-excursion
        (if (eq (following-char) ?<)
            (forward-char))
        (setq tag (sgml-beginning-of-tag))))
  (or (stringp tag)
      (error "No tag selected"))
  (setq tag (downcase tag))
  (message "%s"
           (or (cdr (assoc (downcase tag) sgml-tag-help))
               (and (eq (aref tag 0) ?/)
                    (cdr (assoc (downcase (substring tag 1)) sgml-tag-help)))
               "No description available")))

(defun sgml-maybe-end-tag (&optional arg)
  "Name self unless in position to end a tag or a prefix ARG is given."
  (interactive "P")
  (if (or arg (eq (car (sgml-lexical-context)) 'tag))
      (self-insert-command (prefix-numeric-value arg))
    (sgml-name-self)))

(defun sgml-skip-tag-backward (arg)
  "Skip to beginning of tag or matching opening tag if present.
With prefix argument ARG, repeat this ARG times."
  (interactive "p")
  ;; FIXME: use sgml-get-context or something similar.
  (while (>= arg 1)
    (search-backward "<" nil t)
    (if (looking-at "</\\([^ \n\t>]+\\)")
        ;; end tag, skip any nested pairs
        (let ((case-fold-search t)
              (re (concat "</?" (regexp-quote (match-string 1))
                          ;; Ignore empty tags like <foo/>.
                          "\\([^>]*[^/>]\\)?>")))
          (while (and (re-search-backward re nil t)
                      (eq (char-after (1+ (point))) ?/))
            (forward-char 1)
            (sgml-skip-tag-backward 1))))
    (setq arg (1- arg))))

(defun sgml-skip-tag-forward (arg)
  "Skip to end of tag or matching closing tag if present.
With prefix argument ARG, repeat this ARG times.
Return t if after a closing tag."
  (interactive "p")
  ;; FIXME: Use sgml-get-context or something similar.
  ;; It currently might jump to an unrelated </P> if the <P>
  ;; we're skipping has no matching </P>.
  (let ((return t))
    (with-syntax-table sgml-tag-syntax-table
      (while (>= arg 1)
        (skip-chars-forward "^<>")
        (if (eq (following-char) ?>