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Filename : BENG-OTF.flt
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;; BENG-OTF.flt -- Font Layout Table for Bengali OpenType fonts
;; Copyright (C) 2004, 2007, 2010 AIST (H15PRO112)
;; See the end for copying conditions.

(font layouter beng-otf nil
      (version "1.6.0")
      (font (nil nil unicode-bmp :otf=beng)))

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

;; After-base glyph order for rendering:
;; 1. below form consonants
;; 2. below matra
;; 3. reph
;; 4. candrabindu (0981)
;; 5. post form consonants
;; 6. post matra
;; 7. anusvara (0982) and visarga (0983)

(category
 ;; X: generic
 ;; V: independent vowel
 ;; C: consonant
 ;; B: BA
 ;; Y: YA
 ;; R: RA
 ;; 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)
 ;; N: ZWNJ
 ;; J: ZWJ
 (0x0980 0x09FF	?X)			; generic
 (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	?R)			; LETTER RA WITH MIDDLE DIAGONAL
 (0x09F1	?C)			; LETTER RA WITH LOWER DIAGONAL

 (0x200C	?N)			; ZWNJ
 (0x200D	?J)			; ZWJ
 (0x25CC	?X)			; DOTTED CIRCLE

 (rphf		?r)
 (pstf		?P)
 )

;; Stage 0
;; Preprocessing
(generator
 (0
  (cond
   ;; Decompose two-part vowel signs.
   ((0x09CB)
    0x09C7 0x09BE)
   ((0x09CC)
    0x09C7 0x09D7)

   ;; Many fonts still do not have KHANDA-TA.
   ((0x09CE)
    (cond
     ((font-facility 0x09CE) =)
     (".+" 0x09A4 0x09CD 0x200D)))

   ;; consonant + NUKTA
   ((0x09A1 0x09BC)
    0x09DC)
   ((0x09A2 0x09BC)
    0x09DD)
   ((0x09AF 0x09BC)
    0x09DF)

   ("." =))
  *))

;; Stage 1
;; Syllable identification
(generator
 (0
  (cond
   ;; Syllables with an independent vowel
   ("(RH)?(Vn?)((J?H[BYR])?m?b?p?n?a?A?)"
    < | (1 = =) (2 :otf=beng=nukt+) (3 = *) | >)

   ;; KHANDA-TA combines only with reph.
   ("(RH)?(T)"
    < (2 =) (1 :otf=beng=rphf+) >)

   ;; Consonant-based syllables
   ;;1        23                   4
   ("([CBYR]n?((J?H|HJ?)[CBYR]n?)*)(H[NJ]?|m?([NJ]?b)?p?n?a?A?)"
    < |
    (cond
     (".+HJ$" :otf=beng=nukt,akhn+)
     ("(.+)(H)N?$" (1 :otf=beng=nukt,akhn+) (2 =) 0x200C)
     (".+" :otf=beng=nukt,akhn+))
    | >)

   ;; Two-part vowel signs
   ((0x09C7 0x09BE)
    (cond
     ((font-facility 0x25CC) < = 0x25CC = >)
     (".+" [ 0x09CB ])))
   ((0x09C7 0x09D7)
    (cond
     ((font-facility 0x25CC) < = 0x25CC = >)
     (".+" [ 0x09CC ])))

   ;; Combining marks are displayed with a DOTTED CIRCLE.
   ("m"
    (cond
     ((font-facility 0x25CC) < = 0x25CC >)
     ("." [ = ])))
   ("[nHbpaA]"
    (cond
     ((font-facility 0x25CC) < 0x25CC = >)
     ("." [ = ])))

   ;; Isolated blwf and pstf are displayed with a DOTTED CIRCLE in the
   ;; next stage.
   ("(J)(H)([BYR])"
    < | (1 =) (3 =) (2 =) | >)

   ("." =))
  *))

;; Stage 2
;; Reorder halant for blwf and pstf
(generator
 (0
  (cond
   ;; Isolated blwf and pstf
   (" J([BYR]H) "
    (cond
     ((font-facility 0x25CC) < 0x25CC (1 :otf=beng=blwf,pstf+) >)
     (" J([BYR]H) " [ (1 :otf=beng=blwf,pstf+) ])))

   ;; Syllables with an overt halant
   (" (RHJ?)?([^ ]+)(HN) "
    | (1 = *) (2 reorder) (3 = =) |)

   ;; Syllables with a below matra
   (" (RHJ?)?([^mbpaA ]*[^mbpaANJ ])(m?[NJ]?bp?n?a?A?) "
    | (1 = *) (2 reorder) (3 = *) |)

   ;; Other syllables
   (" (RHJ?)?([^mbpaA ]+)(m?p?n?a?A?) "
    | (1 = *) (2 reorder) (3 = *) |)

   ("." =))
  *)

 (reorder
  ("(.|.+([^YJ]|JY|HJ))((J?HY)*)$"
   (1 reorder-BR *) (3 reorder-Y *)))
 
 ;; Unlike Devanagari and Gujarati, vattu in Bengali does not have a
 ;; half form.  Therefore the sequence CHRHC can be safely reordered
 ;; to CRHHC.  Same for CHBHC.
 (reorder-BR
  (cond
   ("J?(H)([BR])"
    (2 =) (1 =))
   ("." =)))

 (reorder-Y
  ("J?(H)(Y)"
   (2 =) (1 =)))
 )

;; Stage 3
;; Language forms and matra reordering
(generator
 (0
  (cond
   ;; Overt halant forms
   (" (RHJ?)?([^ ]+)(HN) "
    |
    (1 (cond ("RHJ" :otf=beng=half+)
	     ("RH" :otf=beng=rphf+)))
    (2 b4post) (2 post) (3 = =) |)

   ;; Syllables with a below matra
   ;; 1      2              3     4         5
   (" (RHJ?)?([^mb]*[^mbNJ])(mn?)?([NJ]?bn?)(p?n?a?A?) "
    | (3 = *)
    (1 (cond ("RHJ" :otf=beng=half+)
	     ("RH" :otf=beng=rphf+)))
    (2 b4post) (4 = *) (2 post) (5 = *) |)

   ;; Other syllables
   ;; 1      2          3     4
   (" (RHJ?)?([^mpaA ]*)(mn?)?(p?n?a?A?) "
    | (3 = *)
    (1 (cond ("RHJ" :otf=beng=half+)
	     ("RH" :otf=beng=rphf+)))
    (2 b4post) (2 post) (4 = *) |)

   ("." =))
  *)

 (b4post
  (cond
   ("(.H)J?(.*)"
    (1 :otf=beng=half+)
    (2 ("(.|.+([^YH]|JY|[BR]H))((YH)*)$" (1 lang-forms *))))
   ("(.|.+([^YH]|JY|[BR]H))((YH)*)"
    (1 lang-forms *))))

 (lang-forms
  (cond
   ("(.H)J" (1 :otf=beng=half+))
   (".H" :otf=beng=blwf,half,vatu+)
   ("." =)))

 (post
  ("(.|.+([^YH]|JY|[BR]H))((YH)+)$"
   (3 :otf=beng=pstf+)))
 )

;; Stage 4
;; Final reordering #1 (Move pre-base matra after the last halant)
(generator
 (0
  (cond
   ;; 1    2         3
   (" (mn?)([^ ]+HJ?)([^H ]+) "
    | (2 = *) (1 = *) (3 = *) |)

   ("." =))
  *))

;; Stage 5
;; Final reordering #2 (Move reph after the first halant)
(generator
 (0
  (cond
   ;; Syllables with a reph and an explicit halant
   ;; 1     2  3           4
   (" (mn?)?(r)([^HP ]+HJ?)([^ ]*) "
    | (1 = *) (3 = *) (2 =) (4 = *) |)

   ;; A reph without explicit halant
   ;; 1     2  3          4
   (" (mn?)?(r)([^PpaA ]+)(P*(HN)?p?n?a?A?) "
    | (1 = *) (3 = *) (2 =) (4 = *) |)

   ("." =))
  *))

;; Stage 6
;; Nukta for matra and Presentation forms
(generator
 (0
  (cond
   (" (mn?)?([^ ]+) "
    | (1 :otf=beng=nukt,init+) (2 :otf=beng=nukt,pres,abvs,blws,psts,haln+) |)

   ("." =))
  *))

;; Stage 7
;; Remove ZWNJ/ZWJ
(generator
 (0
  (cond
   ("[NJ]")

   ("." =))
  *))

;; Stage 8
;; GPOS processing
(generator
 (0
  (cond
   (" ([^ ]+) "
    (1 :otf=beng=+abvm,blwm,dist))

   ("." =))
  *))

;; Copyright (C) 2004, 2007, 2010
;;   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.

;; Local Variables:
;; mode: emacs-lisp
;; End: