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35 lines
1.9 KiB
Racket
35 lines
1.9 KiB
Racket
#lang racket/base
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(require xenomorph)
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(provide (all-defined-out))
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#|
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approximates
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https://github.com/mbutterick/fontkit/blob/master/src/tables/hmtx.js
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|#
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(define hmtx-entry (x:struct 'advance uint16be 'bearing int16be))
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(define hmtx (x:struct 'metrics (x:lazy-array #:type hmtx-entry
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#:length (λ (arr) (hash-ref (hash-ref (hash-ref arr 'parent) 'hhea) 'numberOfMetrics)))
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'bearings (x:lazy-array #:type int16be
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#:length (λ (arr) (- (hash-ref (hash-ref (hash-ref arr 'parent) 'maxp) 'numGlyphs)
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(hash-ref (hash-ref (hash-ref arr 'parent) 'hhea) 'numberOfMetrics))))))
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(module+ test
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(require rackunit racket/serialize racket/stream racket/class "../helper.rkt")
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;; same as hmtx but doesn't require resolution of function to get length
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(define hmtx-test (x:struct
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'metrics (x:lazy-array hmtx-entry (λ (t) 229))
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'bearing (x:lazy-array int16be (λ (t) 0))))
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(define ip (open-input-file charter-path))
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(define dir (deserialize (read (open-input-file charter-directory-path))))
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(define hmtx-offset (hash-ref (hash-ref (hash-ref dir 'tables) 'hmtx) 'offset))
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(define hmtx-length (hash-ref (hash-ref (hash-ref dir 'tables) 'hmtx) 'length))
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(check-equal? hmtx-offset 456)
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(check-equal? hmtx-length 916)
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(define hmtx-bytes (peek-bytes hmtx-length hmtx-offset ip))
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(define hmtx-data (decode hmtx-test hmtx-bytes))
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(check-equal? (send hmtx-test x:size) (* 229 (send hmtx-entry x:size)))
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(define H-gid 41) (define OE-gid 142)
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(check-equal? (stream-ref (hash-ref hmtx-data 'metrics) H-gid) (make-hasheq '((bearing . 33) (advance . 738))))
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(check-equal? (stream-ref (hash-ref hmtx-data 'metrics) OE-gid) (make-hasheq '((bearing . 43) (advance . 993))))) |