;;; uni-input.el --- Hex Unicode input method

;; Copyright (C) 2001  Free Software Foundation, Inc.

;; Author: Dave Love <fx@gnu.org>
;; Keywords: i18n

;; This file is part of GNU Emacs.

;; This file 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 file 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:

;; Provides an input method for entering characters by hex unicode in
;; the form `uxxxx', similarly to the Yudit editor.

;; This is not really a Quail method, but uses some Quail functions.
;; There is probably A Better Way.

;; Compare `ucs-insert', which explicitly inserts a unicoded character
;; rather than supplying an input method.

;;; Code:

(require 'quail)

;; Maybe stolen from Mule-UCS -- I don't remember.
(define-ccl-program utf-8-ccl-encode
  `(4 (if (r0 < ?\x80)
	((write r0))
      (if (r0 < #x800)
	  ((write ((r0 >> 6) | ?\xC0))
	   (write ((r0 & ?\x3F) | ?\x80)))
	(if (r0 < #x10000)
	    ((write ((r0 >> 12) | ?\xE0))
	     (write (((r0 >> 6) & ?\x3F) | ?\x80))
	     (write ((r0 & ?\x3F) | ?\x80)))
	  (if (r0 < #x200000)
	      ((write ((r0 >> 18) | ?\xF0))
	       (write (((r0 >> 12) & ?\x3F) | ?\x80))
	       (write (((r0 >> 6) & ?\x3F) | ?\x80))
	       (write ((r0 & ?\x3F) | ?\x80)))
	    (if (r0 < #x4000000)
		((write ((r0 >> 24) | ?\xF8))
		 (write (((r0 >> 18) & ?\x3F) | ?\x80))
		 (write (((r0 >> 12) & ?\x3F) | ?\x80))
		 (write (((r0 >> 6) & ?\x3F) | ?\x80))
		 (write ((r0 & ?\x3F) | ?\x80)))
	      ((write ((r0 >> 30) | ?\xFC))
	       (write (((r0 >> 24) & ?\x3F) | ?\x80))
	       (write (((r0 >> 18) & ?\x3F) | ?\x80))
	       (write (((r0 >> 12) & ?\x3F) | ?\x80))
	       (write (((r0 >> 6) & ?\x3F) | ?\x80))
	       (write ((r0 & ?\x3F) | ?\x80))))))))))

(defun ucs-input-method (key)
  (if (or buffer-read-only
	  (and (/= key ?U) (/= key ?u)))
      (list key)
    (quail-setup-overlays nil)
    (let ((current-prefix-arg)
	  (last-command-char key))
      (call-interactively 'self-insert-command))
    (let ((modified-p (buffer-modified-p))
	  (buffer-undo-list t)
	  (input-method-function nil)
	  (echo-keystrokes 0)
	  (help-char nil)
	  (events (list key))
	  (str "    "))
      (unwind-protect
	  (catch 'non-digit
	    (progn
	      (dotimes (i 4)
		(let ((seq (read-key-sequence nil))
		      key)
		  (if (and (stringp seq)
			   (= 1 (length seq))
			   (setq key (aref seq 0))
			   (memq key '(?0 ?1 ?2 ?3 ?4 ?5 ?6 ?7 ?8 ?9 ?a
				       ?b ?c ?d ?e ?f ?A ?B ?C ?D ?E ?F)))
		      (progn
			(push key events)
			(let ((last-command-char key)
			      (current-prefix-arg))
			  (call-interactively 'self-insert-command)))
		    (let ((last-command-char key)
			  (current-prefix-arg))
		      (condition-case nil
			  (call-interactively (key-binding seq))))
		    (quail-delete-region)
		    (throw 'non-digit (append (reverse events)
					      (listify-key-sequence seq))))))
	      (quail-delete-region)
	      (let* ((n (string-to-number (apply 'string
						 (cdr (nreverse events)))
					  16))
		     (c (decode-char 'ucs n))
		    (status (make-vector 9 nil)))
		(if c
		    (list c)
		  (aset status 0 n)
		  (string-to-list (ccl-execute-on-string
				   'utf-8-ccl-encode status ""))))))
	(quail-delete-overlays)
	(set-buffer-modified-p modified-p)
	(run-hooks 'input-method-after-insert-chunk-hook)))))

(defun ucs-input-activate (&optional arg)
  "Activate UCS input method.
With arg, activate UCS input method if and only if arg is positive.

While this input method is active, the variable
`input-method-function' is bound to the function `ucs-input-method'."
  (if (and arg
	  (< (prefix-numeric-value arg) 0))
      (unwind-protect
	  (progn
	    (quail-hide-guidance-buf)
	    (quail-delete-overlays)
	    (setq describe-current-input-method-function nil))
	(kill-local-variable 'input-method-function))
    (setq inactivate-current-input-method-function 'ucs-input-inactivate)
    (setq describe-current-input-method-function 'ucs-input-help)
    (quail-delete-overlays)
    (if (eq (selected-window) (minibuffer-window))
	(add-hook 'minibuffer-exit-hook 'quail-exit-from-minibuffer))
    (add-hook 'kill-buffer-hook 'quail-kill-guidance-buf nil t)
    (set (make-local-variable 'input-method-function)
	 'ucs-input-method)))

(defun ucs-input-inactivate ()
  "Inactivate UCS input method."
  (interactive)
  (ucs-input-activate -1))

(defun ucs-input-help ()
  (interactive)
  (with-output-to-temp-buffer "*Help*"
    (princ "\
Input method: ucs (mode line indicator:U)

Input as Unicode: U<hex> or u<hex>, where <hex> is a four-digit hex number.")))

(register-input-method "ucs" "UTF-8" 'ucs-input-activate "U+"
		       "Unicode input as hex in the form Uxxxx.")

(provide 'uni-input)

;;; uni-input.el ends here