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224 lines
8.4 KiB
Racket
224 lines
8.4 KiB
Racket
#lang racket/base
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(require "racket.rkt")
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(require "font.rkt" fontland "reference.rkt")
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(provide EmbeddedFont)
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#|
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approximates
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https://github.com/mbutterick/pdfkit/blob/master/lib/font/embedded.coffee
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|#
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(define-subclass PDFFont (EmbeddedFont document font id)
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(field [subset (· this font createSubset)]
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;; we make `unicode` and `width` fields integer-keyed hashes not lists
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;; because they offer better random access and growability
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[unicode (mhash 0 '(0))] ; always include the missing glyph (gid = 0)
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[widths (mhash 0 (send (send (· this font) getGlyph 0) advanceWidth))]
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;; always include the width of the missing glyph (gid = 0)
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[name (· font postscriptName)]
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[scale (/ 1000 (· font unitsPerEm))]
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[ascender (* (· font ascent) scale)]
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[descender (* (· font descent) scale)]
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[lineGap (* (· font lineGap) scale)]
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[bbox (· font bbox)])
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(as-methods
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widthOfString
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encode
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embed
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toUnicodeCmap))
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(define width-cache (make-hash))
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(define (widthOfString this string size [features #f])
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((string? number?) ((option/c (listof symbol?))) . ->*m . number?)
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; #f disables features ; null enables default features ; list adds features
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(hash-ref! width-cache
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(list string size (and features (sort features symbol<?)))
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(λ ()
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(define run (send (· this font) layout string features))
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(define width (· run advanceWidth))
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(define scale (/ size (+ (· this font unitsPerEm) 0.0)))
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(* width scale))))
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;; called from text.rkt
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(define/contract (encode this text [features #f])
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((string?) ((option/c list?)) . ->*m .
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(list/c (listof string?) (listof GlyphPosition?)))
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#;(report*/file 'starting-layout-in-embedded (description (· this font)))
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(define glyphRun (send (· this font) layout text features))
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(define glyphs (· glyphRun glyphs))
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(for ([g (in-list glyphs)])
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(· g id))
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(define positions (· glyphRun positions))
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#;(report/file (for/list ([p (in-list positions)])
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(list (· p xAdvance) (· p xOffset))))
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(define-values (subset-idxs new-positions)
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(for/lists (idxs posns)
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([(glyph i) (in-indexed glyphs)]
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[posn (in-list positions)])
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(define gid (send (· this subset) includeGlyph (· glyph id)))
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(define subset-idx (toHex gid))
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(set-field! advanceWidth posn (· glyph advanceWidth))
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(hash-ref! (· this widths) gid (λ () (· posn advanceWidth)))
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(hash-ref! (· this unicode) gid (λ () (· glyph codePoints)))
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(send posn scale (· this scale))
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(values subset-idx posn)))
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(list subset-idxs new-positions))
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(define-macro (sum-flags [COND VAL] ...)
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#'(for/sum ([c (in-list (list COND ...))]
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[v (in-list (list VAL ...))]
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#:when c)
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v))
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(define/contract (embed this)
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(->m void?)
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(define isCFF (is-a? (· this subset) CFFSubset))
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(define fontFile (· this document ref))
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(when isCFF
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(hash-set! (· fontFile payload) 'Subtype "CIDFontType0C"))
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(send fontFile end (get-output-bytes (· this subset encode-to-port)))
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(define familyClass (let ([val (if (send (· this font) has-table? 'OS/2)
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(· this font OS/2 sFamilyClass)
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0)])
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(floor (/ val 256)))) ; equivalent to >> 8
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;; font descriptor flags
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(match-define (list FIXED_PITCH SERIF SYMBOLIC SCRIPT _UNUSED NONSYMBOLIC ITALIC)
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(map (curry expt 2) (range 7)))
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(define flags (sum-flags
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[(not (zero? (· this font post isFixedPitch))) FIXED_PITCH]
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[(<= 1 familyClass 7) SERIF]
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[#t SYMBOLIC] ; assume the font uses non-latin characters
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[(= familyClass 10) SCRIPT]
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[(· this font head macStyle italic) ITALIC]))
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;; generate a random tag (6 uppercase letters. 65 is the char code for 'A')
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(when (test-mode) (random-seed 0))
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(define tag (list->string (for/list ([i (in-range 6)])
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(integer->char (random 65 (+ 65 26))))))
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(define name (string-append tag "+" (· this font postscriptName)))
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(define bbox (· this font bbox))
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(define descriptor (send (· this document) ref
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(mhash
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'Type "FontDescriptor"
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'FontName name
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'Flags flags
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'FontBBox (map (curry * (· this scale))
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(list (· bbox minX) (· bbox minY)
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(· bbox maxX) (· bbox maxY)))
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'ItalicAngle (· this font italicAngle)
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'Ascent (· this ascender)
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'Descent (· this descender)
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'CapHeight (* (or (· this font capHeight) (· this sfont ascent)) (· this scale))
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'XHeight (* (or (· this font xHeight) 0) (· this scale))
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'StemV 0)))
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(hash-set! (· descriptor payload) (if isCFF
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'FontFile3
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'FontFile2) fontFile)
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(· descriptor end)
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#;(report (· descriptor toString) 'descriptor-id)
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(define descendantFont (send (· this document) ref
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(mhash
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'Type "Font"
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'Subtype (string-append "CIDFontType" (if isCFF "0" "2"))
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'BaseFont name
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'CIDSystemInfo
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(mhash
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'Registry (String "Adobe")
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'Ordering (String "Identity")
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'Supplement 0)
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'FontDescriptor descriptor
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'W (list 0 (for/list ([idx (in-range (length (hash-keys (· this widths))))])
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(hash-ref (· this widths) idx (λ () (error 'embed (format "hash key ~a not found" idx)))))))))
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(· descendantFont end)
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#;(report (· descendantFont toString) 'descendantFont)
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(hash-set*! (· this dictionary payload)
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'Type "Font"
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'Subtype "Type0"
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'BaseFont name
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'Encoding "Identity-H"
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'DescendantFonts (list descendantFont)
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'ToUnicode (· this toUnicodeCmap))
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(· this dictionary end))
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(define/contract (toUnicodeCmap this)
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(->m (is-a?/c PDFReference))
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(define cmap (· this document ref))
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(define entries
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(for/list ([idx (in-range (length (hash-keys (· this unicode))))])
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(define codePoints (hash-ref (· this unicode) idx))
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(define encoded ; encode codePoints to utf16
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;; todo: full utf16 support. for now just utf8
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(for/list ([value (in-list codePoints)])
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(toHex value)))
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(format "<~a>" (string-join encoded " "))))
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(define unicode-cmap-str #<<HERE
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/CIDInit /ProcSet findresource begin
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12 dict begin
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begincmap
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/CIDSystemInfo <<
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/Registry (Adobe)
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/Ordering (UCS)
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/Supplement 0
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>> def
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/CMapName /Adobe-Identity-UCS def
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/CMapType 2 def
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1 begincodespacerange
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<0000><ffff>
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endcodespacerange
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1 beginbfrange
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<0000> <~a> [~a]
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endbfrange
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endcmap
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CMapName currentdict /CMap defineresource pop
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end
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end
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HERE
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)
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(send cmap end (format unicode-cmap-str (toHex (sub1 (length entries))) (string-join entries " ")))
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#;(report (· cmap toString) 'cmap-id)
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cmap)
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(define/contract (toHex . codePoints)
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(() () #:rest (listof number?) . ->*m . string?)
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(string-append*
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(for/list ([code (in-list codePoints)])
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(~r code #:base 16 #:min-width 4 #:pad-string "0"))))
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(module+ test
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(require rackunit fontland)
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(define f (openSync "test/assets/Charter.ttf" #f))
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(define ef (make-object EmbeddedFont #f f #f))
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(check-equal? (send ef widthOfString "f" 1000) 321.0)
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(check-equal? (· ef ascender) 980)
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(check-equal? (· ef descender) -238)
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(check-equal? (· ef lineGap) 0)
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(check-equal? (bbox->list (· ef bbox)) '(-161 -236 1193 963))
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(define H-gid 41)
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(check-equal? (· ef widths) (mhash 0 278))
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(check-equal? (send (send (· ef font) getGlyph H-gid) advanceWidth) 738)
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) |