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typesetting/pitfall/fontkit/glyph.rkt

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Racket

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#lang fontkit/racket
(require "freetype-ffi.rkt")
(provide Glyph CFFGlyph TTFGlyph)
(module+ test (require rackunit))
#|
/**
* Glyph objects represent a glyph in the font. They have various properties for accessing metrics and
* the actual vector path the glyph represents, and methods for rendering the glyph to a graphics context.
*
* You do not create glyph objects directly. They are created by various methods on the font object.
* There are several subclasses of the base Glyph class internally that may be returned depending
* on the font format, but they all inherit from this class.
*/
|#
;; approximates
;; https://github.com/devongovett/fontkit/blob/master/src/glyph/Glyph.js
(define (is-mark? codepoint)
;; mark classes = Mn Me Mc
(regexp-match #px"\\p{Mn}|\\p{Me}|\\p{Mc}" (string (integer->char codepoint))))
(module+ test
(check-true (and (is-mark? #x300) #t))
(check-false (and (is-mark? #x2ee) #t)))
(define-subclass object% (Glyph id codePoints font)
(field [_font font]
[isMark (andmap is-mark? codePoints)]
[isLigature (> (length codePoints) 1)]
[_metrics #f])
(as-methods
advanceWidth
_getMetrics))
(define/contract (advanceWidth this)
(->m number?)
(hash-ref (_getMetrics this) 'advanceWidth))
(define/contract (_getMetrics this)
(->m hash?)
(unless (· this _metrics)
(define face (· this _font ft-face))
(FT_Load_Glyph face (· this id) FT_LOAD_NO_RECURSE)
(define glyph (FT_FaceRec-glyph face))
(define glyph-metrics (FT_GlyphSlotRec-metrics glyph))
(set-field! _metrics this (mhash))
(hash-set*! (· this _metrics)
'advanceWidth (FT_Glyph_Metrics-horiAdvance glyph-metrics)
'leftBearing (FT_Glyph_Metrics-horiBearingX glyph-metrics)))
(· this _metrics))
(define-subclass Glyph (CFFGlyph)
(error 'cff-glyph-unimplemented))
(define-subclass Glyph (TTFGlyph)
)