;;; disp-table.el --- functions for dealing with char tables

;; Copyright (C) 1987, 1994, 1995, 1999 Free Software Foundation, Inc.

;; Author: Erik Naggum <erik@naggum.no>
;; Based on a previous version by Howard Gayle
;; Maintainer: FSF
;; Keywords: i18n

;; 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:

;;; Code:

(put 'display-table 'char-table-extra-slots 6)

;;;###autoload
(defun make-display-table ()
  "Return a new, empty display table."
  (make-char-table 'display-table nil))

(or standard-display-table
    (setq standard-display-table (make-display-table)))

;;; Display-table slot names.  The property value says which slot.

(put 'truncation 'display-table-slot 0)
(put 'wrap 'display-table-slot 1)
(put 'escape 'display-table-slot 2)
(put 'control 'display-table-slot 3)
(put 'selective-display 'display-table-slot 4)
(put 'vertical-border 'display-table-slot 5)

;;;###autoload
(defun display-table-slot (display-table slot)
  "Return the value of the extra slot in DISPLAY-TABLE named SLOT.
SLOT may be a number from 0 to 5 inclusive, or a slot name (symbol).
Valid symbols are `truncation', `wrap', `escape', `control',
`selective-display', and `vertical-border'."
  (let ((slot-number
	 (if (numberp slot) slot
	   (or (get slot 'display-table-slot)
	       (error "Invalid display-table slot name: %s" slot)))))
    (char-table-extra-slot display-table slot-number)))

;;;###autoload
(defun set-display-table-slot (display-table slot value)
  "Set the value of the extra slot in DISPLAY-TABLE named SLOT to VALUE.
SLOT may be a number from 0 to 5 inclusive, or a name (symbol).
Valid symbols are `truncation', `wrap', `escape', `control',
`selective-display', and `vertical-border'."
  (let ((slot-number
	 (if (numberp slot) slot
	   (or (get slot 'display-table-slot)
	       (error "Invalid display-table slot name: %s" slot)))))
    (set-char-table-extra-slot display-table slot-number value)))

;;;###autoload
(defun describe-display-table (dt)
  "Describe the display table DT in a help buffer."
  (with-output-to-temp-buffer "*Help*"
    (princ "\nTruncation glyph: ")
    (prin1 (display-table-slot dt 'truncation))
    (princ "\nWrap glyph: ")
    (prin1 (display-table-slot dt 'wrap))
    (princ "\nEscape glyph: ")
    (prin1 (display-table-slot dt 'escape))
    (princ "\nCtrl glyph: ")
    (prin1 (display-table-slot dt 'control))
    (princ "\nSelective display glyph sequence: ")
    (prin1 (display-table-slot dt 'selective-display))
    (princ "\nVertical window border glyph: ")
    (prin1 (display-table-slot dt 'vertical-border))
    (princ "\nCharacter display glyph sequences:\n")
    (save-excursion
      (set-buffer standard-output)
      (let ((vector (make-vector 256 nil))
	    (i 0))
	(while (< i 256)
	  (aset vector i (aref dt i))
	  (setq i (1+ i)))
	(describe-vector vector))
      (help-mode))
    (print-help-return-message)))

;;;###autoload
(defun describe-current-display-table ()
  "Describe the display table in use in the selected window and buffer."
  (interactive)
  (let ((disptab (or (window-display-table (selected-window))
		     buffer-display-table
		     standard-display-table)))
    (if disptab
	(describe-display-table disptab)
      (message "No display table"))))

;;;###autoload
(defun standard-display-8bit (l h)
  "Display characters in the range L to H literally."
  (while (<= l h)
    (if (and (>= l ?\ ) (< l 127))
	(aset standard-display-table l nil)
      (aset standard-display-table l (vector l)))
    (setq l (1+ l))))

;;;###autoload
(defun standard-display-default (l h)
  "Display characters in the range L to H using the default notation."
  (while (<= l h)
    (if (and (>= l ?\ ) (char-valid-p l))
	(aset standard-display-table l nil))
    (setq l (1+ l))))

;; This function does NOT take terminal-dependent escape sequences.
;; For that, you need to go through create-glyph.  Use one of the
;; other functions below, or roll your own.
;;;###autoload
(defun standard-display-ascii (c s)
  "Display character C using printable string S."
  (aset standard-display-table c (vconcat s)))

;;;###autoload
(defun standard-display-g1 (c sc)
  "Display character C as character SC in the g1 character set.
This function assumes that your terminal uses the SO/SI characters;
it is meaningless for an X frame."
  (if (memq window-system '(x w32))
      (error "Cannot use string glyphs in a windowing system"))
  (aset standard-display-table c
	(vector (create-glyph (concat "\016" (char-to-string sc) "\017")))))

;;;###autoload
(defun standard-display-graphic (c gc)
  "Display character C as character GC in graphics character set.
This function assumes VT100-compatible escapes; it is meaningless for an
X frame."
  (if (memq window-system '(x w32))
      (error "Cannot use string glyphs in a windowing system"))
  (aset standard-display-table c
	(vector (create-glyph (concat "\e(0" (char-to-string gc) "\e(B")))))

;;;###autoload
(defun standard-display-underline (c uc)
  "Display character C as character UC plus underlining."
  (aset standard-display-table c
	(vector 
	 (if window-system
	     (logior uc (lsh (face-id 'underline) 19))
	   (create-glyph (concat "\e[4m" (char-to-string uc) "\e[m"))))))

;;;###autoload
(defun create-glyph (string)
  "Allocate a glyph code to display by sending STRING to the terminal."
  (if (= (length glyph-table) 65536)
      (error "No free glyph codes remain"))
  ;; Don't use slots that correspond to ASCII characters.
  (if (= (length glyph-table) 32)
      (setq glyph-table (vconcat glyph-table (make-vector 224 nil))))
  (setq glyph-table (vconcat glyph-table (list string)))
  (1- (length glyph-table)))

;;;###autoload
(defun standard-display-european (arg)
  "Semi-obsolete way to toggle display of ISO 8859 European characters.

This function is semi-obsolete; if you want to do your editing with
unibyte characters, it is better to `set-language-environment' coupled
with either the `--unibyte' option or the EMACS_UNIBYTE environment
variable, or else customize `enable-multibyte-characters'.

With prefix argument, this command enables European character display
if arg is positive, disables it otherwise.  Otherwise, it toggles
European character display.

When this mode is enabled, characters in the range of 160 to 255
display not as octal escapes, but as accented characters.  Codes 146
and 160 display as apostrophe and space, even though they are not the
ASCII codes for apostrophe and space.

Enabling European character display with this command noninteractively
from Lisp code also selects Latin-1 as the language environment, and
selects unibyte mode for all Emacs buffers \(both existing buffers and
those created subsequently).  This provides increased compatibility
for users who call this function in `.emacs'."

  (if (or (<= (prefix-numeric-value arg) 0)
	  (and (null arg)
	       (char-table-p standard-display-table)
	       ;; Test 161, because 160 displays as a space.
	       (equal (aref standard-display-table 161) [161])))
      (progn
	(standard-display-default 160 255)
	(unless (or (memq window-system '(x w32))
		    (interactive-p))
	  (and (terminal-coding-system)
	       (set-terminal-coding-system nil))))
    ;; If the user does this explicitly from Lisp (as in .emacs),
    ;; turn off multibyte chars for more compatibility.
    (unless (interactive-p)
      (setq-default enable-multibyte-characters nil)
      (mapcar (lambda (buffer)
		(with-current-buffer buffer
		  (if enable-multibyte-characters
		      (set-buffer-multibyte nil))))
	      (buffer-list)))
    ;; If the user does this explicitly,
    ;; switch to Latin-1 language environment
    ;; unless some other has been specified.
    (unless (interactive-p)
      (if (equal current-language-environment "English")
	  (set-language-environment "latin-1")))
    (unless (or noninteractive (memq window-system '(x w32))
		(interactive-p))
      ;; Send those codes literally to a character-based terminal.
      ;; If we are using single-byte characters,
      ;; it doesn't matter which coding system we use.
      (set-terminal-coding-system
       (let ((c (intern (downcase current-language-environment))))
	 (if (coding-system-p c) c 'latin-1))))
    (standard-display-european-internal)))

(provide 'disp-table)

;;; disp-table.el ends here
