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;;; tv-util.el --- support for Tai Viet -*- lexical-binding: t; -*-
;; Copyright (C) 2007, 2008, 2009, 2010, 2011
;; National Institute of Advanced Industrial Science and Technology (AIST)
;; Registration Number H13PRO009
;; Keywords: multilingual, Tai Viet, 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 3 of the License, 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. If not, see <https://www.gnu.org/licenses/>.
;;; Code
;; Regexp matching with a sequence of Tai Viet characters.
(defconst tai-viet-re "[\xaa80-\xaac2\xaadb-\xaadf]+")
;; Char-table of information about glyph type of Tai Viet characters.
(defconst tai-viet-glyph-info
(let ((table (make-char-table nil))
(specials '((right-overhang . "ꪊꪋꪌꪍꪏꪓꪖꪜꪞꪡꪤꪨ")
(left-overhang . "ꫂ")
(combining-vowel . "ꪴꪰꪲꪳꪷꪸꪾ")
(combining-tone . "꪿꫁")
(misc . "-"))))
;; Set all TaiViet characters to t.
(set-char-table-range table (cons #xaa80 #xaac2) t)
(set-char-table-range table (cons #xaadb #xaadf) t)
;; Overwrite it for special characters.
(dolist (elt specials)
(let ((category (car elt))
(chars (cdr elt)))
(dotimes (i (length chars))
(aset table (aref chars i) category))))
table))
(defun tai-viet-compose-string (from to string)
"Compose Tai Viet characters in STRING between indices FROM and TO."
(let* ((ch (aref string from))
(info (aref tai-viet-glyph-info ch))
prev-info)
(if (eq info 'non-spacing)
(compose-string string from (1+ from) (string ch ?\t)))
(setq from (1+ from) prev-info info)
(while (and (< from to)
(>= #xaa80 (setq ch (aref string from)))
(<= #xaaDF ch))
(setq info (aref tai-viet-glyph-info ch))
(if (and (eq info 'non-spacing)
(eq prev-info 'non-spacing))
(compose-string from (1+ from) (string ?\t ch)))
(setq from (1+ from) prev-info info))
(if (eq info 'right-overhang)
(compose-string string (1- from) from (string ch ?\t)))
from))
(defun tai-viet-compose-region (from to)
"Compose Tai Viet characters in the region between FROM and TO."
(decompose-region from to)
(let ((normal-rule '(Br . Bl))
(tone-rule '(tr . bl))
(prev-viet nil)
ch info pos components overhang)
(while (< from to)
(or ch
(setq ch (char-after from)
info (aref tai-viet-glyph-info ch)))
(setq from (1+ from))
(if (not info)
(setq prev-viet nil
ch nil)
(if (memq info '(combining-vowel combining-tone))
(progn
;; Display this as a spacing glyph.
(compose-region (1- from) from (string ?\t ch))
(setq prev-viet t
ch nil))
(setq pos (1- from)
components ch
overhang (if (eq info 'right-overhang)
'right-overhang
(if (and (not prev-viet) (eq info 'left-overhang))
'left-overhang))
prev-viet t
ch nil)
(if (and (< from to)
(setq ch (char-after from)
info (aref tai-viet-glyph-info ch)))
(if (memq info '(combining-vowel combining-tone))
(progn
(setq components
(list components normal-rule ch)
from (1+ from)
ch nil)
(if (and (< from to)
(setq ch (char-after from)
info (aref tai-viet-glyph-info ch))
(eq info 'combining-tone))
(setq components (nconc components
(list tone-rule ch))
from (1+ from)))
(if (eq overhang 'left-overhang)
(setq components (cons ?\t
(cons normal-rule components)))
(if (and (eq overhang 'right-overhang)
(>= from to))
(setq components (nconc components
(list normal-rule ?\t)))))
(compose-region pos from components))
(if (eq overhang 'left-overhang)
(compose-region pos from (string ?\t components))))
(if (eq overhang 'left-overhang)
(compose-region pos from (string ?\t components))
(if (and (eq overhang 'right-overhang) (>= from to))
(compose-region pos from (string components ?\t))))))))
from))
;;;###autoload
(defun tai-viet-composition-function (from _to _font-object string _direction)
(if string
(if (string-match tai-viet-re string from)
(tai-viet-compose-string from (match-end 0) string))
(goto-char from)
(if (looking-at tai-viet-re)
(tai-viet-compose-region from (match-end 0)))))
(provide 'tai-viet-util)
;;; tv-util.el ends here
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