typesetting/pitfall/fontkit/fpgm.rkt

#lang fontkit/racket
(require restructure)
(provide (all-defined-out))
#|
approximates
https://github.com/mbutterick/fontkit/blob/master/src/tables/fpgm.js
|#

;; A list of instructions that are executed once when a font is first used.
;; These instructions are known as the font program. The main use of this table
;; is for the definition of functions that are used in many different glyph programs.


(define-subclass RStruct (Rfpgm))

(define fpgm (make-object Rfpgm
               (dictify
                'instructions (make-object RArray uint8))))

(test-module
 (require "directory.rkt")
 (define ip (open-input-file charter-path))
 (define dir (directory-decode ip))
 (define offset (· dir tables fpgm offset))
 (define len (· dir tables fpgm length))
 (check-equal? offset 4140)
 (check-equal? len 371)
 (set-port-position! ip 0)
 (define ds (make-object RDecodeStream (peek-bytes len offset ip)))
 (check-equal? (hash-ref (send fpgm decode ds) 'instructions) '(184
  0
  0
  44
  75
  184
  0
  9
  80
  88
  177
  1
  1
  142
  89
  184
  1
  255
  133
  184
  0
  68
  29
  185
  0
  9
  0
  3
  95
  94
  45
  184
  0
  1
  44
  32
  32
  69
  105
  68
  176
  1
  96
  45
  184
  0
  2
  44
  184
  0
  1
  42
  33
  45
  184
  0
  3
  44
  32
  70
  176
  3
  37
  70
  82
  88
  35
  89
  32
  138
  32
  138
  73
  100
  138
  32
  70
  32
  104
  97
  100
  176
  4
  37
  70
  32
  104
  97
  100
  82
  88
  35
  101
  138
  89
  47
  32
  176
  0
  83
  88
  105
  32
  176
  0
  84
  88
  33
  176
  64
  89
  27
  105
  32
  176
  0
  84
  88
  33
  176
  64
  101
  89
  89
  58
  45
  184
  0
  4
  44
  32
  70
  176
  4
  37
  70
  82
  88
  35
  138
  89
  32
  70
  32
  106
  97
  100
  176
  4
  37
  70
  32
  106
  97
  100
  82
  88
  35
  138
  89
  47
  253
  45
  184
  0
  5
  44
  75
  32
  176
  3
  38
  80
  88
  81
  88
  176
  128
  68
  27
  176
  64
  68
  89
  27
  33
  33
  32
  69
  176
  192
  80
  88
  176
  192
  68
  27
  33
  89
  89
  45
  184
  0
  6
  44
  32
  32
  69
  105
  68
  176
  1
  96
  32
  32
  69
  125
  105
  24
  68
  176
  1
  96
  45
  184
  0
  7
  44
  184
  0
  6
  42
  45
  184
  0
  8
  44
  75
  32
  176
  3
  38
  83
  88
  176
  64
  27
  176
  0
  89
  138
  138
  32
  176
  3
  38
  83
  88
  35
  33
  176
  128
  138
  138
  27
  138
  35
  89
  32
  176
  3
  38
  83
  88
  35
  33
  184
  0
  192
  138
  138
  27
  138
  35
  89
  32
  176
  3
  38
  83
  88
  35
  33
  184
  1
  0
  138
  138
  27
  138
  35
  89
  32
  176
  3
  38
  83
  88
  35
  33
  184
  1
  64
  138
  138
  27
  138
  35
  89
  32
  184
  0
  3
  38
  83
  88
  176
  3
  37
  69
  184
  1
  128
  80
  88
  35
  33
  184
  1
  128
  35
  33
  27
  176
  3
  37
  69
  35
  33
  35
  33
  89
  27
  33
  89
  68
  45
  184
  0
  9
  44
  75
  83
  88
  69
  68
  27
  33
  33
  89
  45)))