;; BENG-OTF.flt -- Font Layout Table for Bengali OpenType font
;; Copyright (C) 2004, 2007
;;   National Institute of Advanced Industrial Science and Technology (AIST)
;;   Registration Number H15PRO112

;; This file is part of the m17n database; a sub-part of the m17n
;; library.

;; The m17n library is free software; you can redistribute it and/or
;; modify it under the terms of the GNU Lesser General Public License
;; as published by the Free Software Foundation; either version 2.1 of
;; the License, or (at your option) any later version.

;; The m17n library 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
;; Lesser General Public License for more details.

;; You should have received a copy of the GNU Lesser General Public
;; License along with the m17n library; if not, write to the Free
;; Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.

;;; <li> BENG-OTF.flt
;;;
;;; For Bengali OpenType fonts to draw the Bengali script.  

(font layouter beng-otf nil
      (font (nil nil unicode-bmp :otf=beng=rphf)))

(category
 ;; X: generic
 ;; V: independent vowel
 ;; C: consonant (except for R, B and Y)
 ;; R: consonant RA
 ;; B: consonant BA
 ;; Y: consonant YA
 ;; T: KHANDA TA
 ;; n: NUKTA
 ;; H: HALANT
 ;; m: vowel sign (pre)
 ;; b: vowel sign (below)
 ;; p: vowel sign (post)
 ;; A: vowel modifier (above)
 ;; a: vowel modifier (post)
 ;; Z: internal use
 ;; N: ZWNJ (ZERO WIDTH NON-JOINER)
 ;; J: ZWJ (ZERO WIDTH JOINER)
 (0x0980 0x09FF	?X)			; generic
 (0x0980	?Z)			; internal use
 (0x0981	?A)			; SIGN CANDRABINDU
 (0x0982 0x0983	?a)			; SIGN ANUSVARA .. VISARGA
 (0x0985 0x0994	?V)			; LETTER A .. AU
 (0x0995 0x09B9	?C)			; LETTER KA .. HA
 (0x09AC	?B)			; LETTER BA
 (0x09AF	?Y)			; LETTER YA
 (0x09B0	?R)			; LETTER RA
 (0x09BC	?n)			; SIGN NUKTA
 (0x09BE	?p)			; VOWEL SIGN AA
 (0x09BF	?m)			; VOWEL SIGN I
 (0x09C0	?p)			; VOWEL SIGN II
 (0x09C1 0x09C4	?b)			; VOWEL SIGN U .. RR
 (0x09C7 0x09C8	?m)			; VOWEL SIGN E .. AI
 (0x09CD	?H)			; SIGN VIRAMA
 (0x09CE	?T)			; LETTER KHANDA TA
 (0x09D7	?p)			; AU LENGTH MARK
 (0x09DC 0x09DF	?C)			; LETTER RRA .. YYA
 (0x09E0 0x09E1	?V)			; LETTER VOCALIC RR, LL
 (0x09E2 0x09E3	?b)			; VOWEL SIGN L .. LL
 (0x09F0 0x09F1	?C)			; LETTER RR WITH MIDDLE/LOWER DIAGONAL
 (0x0964 0x0965	?X)			; DANDA .. DOUBLE DANDA
 (0x200C	?N)			; ZWNJ
 (0x200D	?J)			; ZWJ
 )

;; Change consonant 
(generator
 (0
  (cond
   ;; Decompose two-part vowel signs.
   ((0x09CB)
    0x09C7 0x09BE)
   ((0x09CC)
    0x09C7 0x09D7)
   ;; TA + HALANT + ZWJ -> KHANDA-TA
   ((0x09A4 0x09CD 0x200D)
    0x09CE)
   ;; consonant + NUKTA
   ((0x09A1 0x09BC)
    0x09DC)
   ((0x09A2 0x09BC)
    0x09DD)
   ((0x09AF 0x09BC)
    0x09DF)
   ("." =))
  *))

;; Syllable identification and reordering.
(generator
 (0
  (cond
   ;; Khanda-Ta
   ("(RH)?(T)"
    < | (2 =) (1 otf:beng=rphf+) | >)

   ;; Standalone Ya-phalaa
   ("JHY"
    < | post | >)

   ;; A syllable with a pre-base vowel sign.
   ;;1    2        3       4      5       6  7   8   9
   ("(RH)?([CRBY]n?(HCn?)*(H[RB])?(J?HY)?)(m)(p)?(A)?(a)?"
    < | (6 =) (2 pre-below) (1 otf:beng=rphf+) (8 =) (2 post) (7 =) (9 =) | >)

   ;; A syllable with a non-pre-base vowel sign.
   ;;1    2        3       4      5       6     78   9   10  11
   ("(RH)?([CRBY]n?(HCn?)*(H[RB])?(J?HY)?)(N)?J?((b)|(p))(A)?(a)?"
    < | (6 =) (2 pre-below) (8 =) (1 otf:beng=rphf+) (10 =)
    (2 post) (9 =) (11 =) | >)

   ;; A syllable with a vowel modifier and no vowel signs.
   ;;1    2        3      4       5       67   8
   ("(RH)?([CRBY]n?(HCn?)*(H[RB])?(J?HY)?)((A)|(a))"
    < | (2 pre-below) (1 otf:beng=rphf+) (7 =) (2 post) (8 =) | >)

   ;; A syllable ending with a halant.
   ;;1    2        3      4       5       6
   ("(RH)?([CRBY]n?(HCn?)*(H[RB])?(J?HY)?)(H)?N?"
    < | (2 pre-below) (6 =) (1 otf:beng=rphf+) (2 post) | >)

   ;; A syllable starting with an independent vowel.
   ;;1  2      3
   ("(V)(J?HY)?(A?a?)"
    < | (1 =) 0x0980 (2 post) (3 = *) | >)

   ("." =))
  *)

 ;; Move a halant after the base consonant to the end.
 ;; Put a special mark after the final belew-base consonant.
 ;; Remove post-base parts.
 (pre-below
  (cond
   ("(.+)(H)([RB])(J?HY)?$"
    (1 = *) (3 =) (2 =) 0x0980)
   ("([^J]+)J?HY$"
    (1 = *) 0x0980)
   (".+"
    = * 0x0980)))

 ;; Extract post-base parts and add a halant at the end.
 ;; Produce nothing if there are no post-base parts.
 (post
  (cond
   (".*(H)(Y)$"
    (2 =) (1 =))
   (".+"
    ))))

;; Apply'nukt' and 'akhn'.
(generator
 (0
  (cond
   (" ([^Z]+)(Z[^ ]*) "
    | (1 otf:beng=nukt,akhn+) (2 = *) |)
   ("." =))
  *))

;; Apply 'blwf' and 'pstf' to the concerning parts.
(generator
 (0
  (cond
   (" (N?m?.)([^Z]*)(Z)([^ ]*) "
    | (1 = *) (2 otf:beng=blwf+) (3 =) (4 otf:beng=pstf+) |)
   (" (YH) "
    | (1 otf:beng=pstf+) |)
   ("." =))
  *))

;; Get pre-base and below-base conjuncts.
(generator
 (0
  (cond
   (" (N?m?)([^Z]+)(Z)([^ ]*) "
    | (1 = *) (2 otf:beng=half,vatu,pres,blws+) (3 =) (4 = *) |)
   ("." =))
  *))

;; When the number of glyphs between a pre-base vowel sign and the
;; post-below mark is more than one, move the pre-base vowel sign
;; before the final glyph.
(generator
 (0
  (cond
   (" (N)?(m)([^Z]+)([^Z])Z([^ ]*) "
    | (1 =) (3 = *) (2 =) (4 =) (5 = *) |)
   (" ([^Z]+)Z([^ ]*) "
    | (1 = *) (2 = *) |)
   ("." =))
  *))

;; Get matra conjuncts.
;; Do not apply 'blws' to syllables that begins with ZWNJ.
(generator
 (0
  (cond
   (" N([^ ]+) "
    (1 otf:beng=init,pres,abvs,psts,haln))
   (" ([^ ]+) "
    (1 otf:beng=init,pres,abvs,blws,psts,haln))
   ("."
    [ otf:beng=+ ]))
  *))

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