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typesetting/pitfall/fontkit/OS2.rkt

79 lines
4.7 KiB
Racket

#lang fontkit/racket
(require restructure)
(provide (all-defined-out))
#|
approximates
https://github.com/mbutterick/fontkit/blob/master/src/tables/OS2.js
|#
(define-subclass VersionedStruct (ROS/2))
(define OS/2 (let ()
(define type-1
(dictify 'typoAscender int16be
'typoDescender int16be
'typoLineGap int16be
'winAscent uint16be
'winDescent uint16be
'codePageRange (+Array uint32be 2)))
(define type-2
(dictify 'xHeight int16be
'capHeight int16be
'defaultChar uint16be
'breakChar uint16be
'maxContent uint16be))
(define type-5
(dictify 'usLowerOpticalPointSize uint16be
'usUpperOpticalPointSize uint16be))
(+ROS/2
uint16be
(dictify
'header (dictify 'xAvgCharWidth int16be ;; average weighted advance width of lower case letters and space
'usWeightClass uint16be ;; visual weight of stroke in glyphs
'usWidthClass uint16be ;; relative change from the normal aspect ratio (width to height ratio)
;; Indicates font embedding licensing rights
'fsType (+Bitfield uint16be '(null noEmbedding viewOnly editable null null null null noSubsetting bitmapOnly))
'ySubscriptXSize int16be ;; recommended horizontal size in pixels for subscripts
'ySubscriptYSize int16be ;; recommended vertical size in pixels for subscripts
'ySubscriptXOffset int16be ;; recommended horizontal offset for subscripts
'ySubscriptYOffset int16be ;; recommended vertical offset form the baseline for subscripts
'ySuperscriptXSize int16be ;; recommended horizontal size in pixels for superscripts
'ySuperscriptYSize int16be ;; recommended vertical size in pixels for superscripts
'ySuperscriptXOffset int16be ;; recommended horizontal offset for superscripts
'ySuperscriptYOffset int16be ;; recommended vertical offset from the baseline for superscripts
'yStrikeoutSize int16be ;; width of the strikeout stroke
'yStrikeoutPosition int16be ;; position of the strikeout stroke relative to the baseline
'sFamilyClass int16be ;; classification of font-family design
'panose (+Array uint8 10) ;; describe the visual characteristics of a given typeface
'ulCharRange (+Array uint32be 4)
'vendorID (+String 4) ;; four character identifier for the font vendor
;; bit field containing information about the font
'fsSelection (+Bitfield uint16 '(italic underscore negative outlined strikeout bold regular useTypoMetrics wws oblique))
'usFirstCharIndex uint16be ;; The minimum Unicode index in this font
'usLastCharIndex uint16be) ;; The maximum Unicode index in this font
0 null
1 type-1
2 (append type-1 type-2)
3 (append type-1 type-2)
4 (append type-1 type-2)
5 (append type-1 type-2 type-5)))))
(test-module
(define ip (open-input-file charter-path))
(define dir (deserialize (read (open-input-file charter-directory-path))))
(define offset (· dir tables OS/2 offset))
(define len (· dir tables OS/2 length))
(check-equal? offset 360)
(check-equal? len 96)
(define ds (+DecodeStream (peek-bytes len offset ip)))
(define version (send uint16be decode ds))
(send OS/2 force-version! version)
(define table-data (send OS/2 decode ds))
(check-equal? (· table-data panose) '(2 0 5 3 6 0 0 2 0 4))
(check-equal? (· table-data sFamilyClass) 0))