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#lang debug racket/base
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(require racket/serialize
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racket/list
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racket/match
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sugar/unstable/dict
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"table/loca.rkt"
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"table-stream.rkt"
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"directory.rkt"
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"struct.rkt"
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fontland/glyph
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fontland/ttf-glyph
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fontland/cff-glyph
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xenomorph
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racket/dict
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fontland/table/cff/cff-font
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fontland/table/cff/cff-top
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fontland/table/cff/cff-standard-strings)
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(provide subset +subset
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ttf-subset +ttf-subset ttf-subset?
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cff-subset +cff-subset cff-subset?
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subset-add-glyph! encode-to-port create-subset)
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#|
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from
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https://github.com/mbutterick/fontkit/blob/master/src/TTFFont.js
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|#
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(define (create-subset font)
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((if (has-table? font #"CFF_")
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+cff-subset
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+ttf-subset) font))
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#|
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approximates
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https://github.com/mbutterick/fontkit/blob/master/src/subset/Subset.js
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|#
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(define (+subset font [glyphs empty] [mapping (mhash)])
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(define ss (subset font glyphs mapping))
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(subset-add-glyph! ss 0)
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ss)
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(define (encode-to-port ss)
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(define p (open-output-bytes))
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((if (cff-subset? ss)
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cff-subset-encode
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ttf-subset-encode) ss p)
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p)
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(define (subset-add-glyph! ss glyph-or-gid) ; fka `includeGlyph`
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(define new-gid ((if (glyph? glyph-or-gid) glyph-id values) glyph-or-gid))
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;; put the new glyph at the end of `glyphs`,
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;; and put its index in the mapping
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(hash-ref! (subset-mapping ss) new-gid
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(λ ()
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(set-subset-glyphs! ss (append (subset-glyphs ss) (list new-gid)))
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(sub1 (length (subset-glyphs ss))))))
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#|
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approximates
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https://github.com/mbutterick/fontkit/blob/master/src/subset/CFFSubset.js
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|#
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(define (+cff-subset font [glyphs empty] [mapping (mhash)]
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[cff (get-table font 'CFF_)]
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[strings #f]
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[charstrings #f]
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[gsubrs #f])
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(define ss (cff-subset font glyphs mapping cff strings charstrings gsubrs))
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(subset-add-glyph! ss 0)
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ss)
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(require racket/format racket/string)
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(define (bytes->hexes bs)
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(string-join
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(for/list ([b (in-bytes bs)])
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(~r #:base 16 b #:min-width 2 #:pad-string "0")) " "))
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(define (subset-charstrings this)
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(set-cff-subset-charstrings! this null)
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(define gsubrs (make-hasheq))
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(for ([gid (in-list (subset-glyphs this))])
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(set-cff-subset-charstrings!
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this
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(append (cff-subset-charstrings this)
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(list (get-char-string (cff-subset-cff this) gid))))
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(define glyph (get-glyph (subset-font this) gid))
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(unless (cff-glyph-path glyph) (getPath glyph)) ;; this causes the glyph to be parsed
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(for ([subr (in-hash-keys (cff-glyph-_usedGsubrs glyph))])
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(hash-set! gsubrs subr #true)))
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(set-cff-subset-gsubrs! this (subset-subrs
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this
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(hash-ref (cff-subset-cff this) 'globalSubrIndex)
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gsubrs)))
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(define (subset-subrs this subrs used)
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(for/vector ([(subr i) (in-indexed subrs)])
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(cond
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[(hash-ref used i #false)
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(pos (hash-ref (cff-subset-cff this) 'stream) (index-item-offset subr))
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(read-bytes (index-item-length subr) (hash-ref (cff-subset-cff this) 'stream))]
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[else (bytes 11)])))
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(define (subset-font-dict this topDict)
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(error 'subsetFontdict-unimplemented))
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(define (create-cid-fontdict this top-dict)
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(define used-subrs (make-hasheq))
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(for ([gid (in-list (subset-glyphs this))])
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(define glyph (get-glyph (subset-font this) gid))
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(unless (cff-glyph-path glyph) (getPath glyph)) ;; this causes the glyph to be parsed
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(for ([subr (in-hash-keys (cff-glyph-_usedSubrs glyph))])
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(hash-set! used-subrs subr #true)))
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(define cff-topDict (hash-ref (cff-subset-cff this) 'topDict))
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(define private-dict (hash-copy (hash-ref cff-topDict 'Private (make-hasheq))))
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(when (and (hash-has-key? cff-topDict 'Private) (hash-has-key? (hash-ref cff-topDict 'Private) 'Subrs))
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(hash-set! private-dict 'Subrs (subset-subrs this
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(hash-ref (hash-ref cff-topDict 'Private) 'Subrs)
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used-subrs)))
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(hash-set! top-dict 'FDArray (list (dictify 'Private private-dict)))
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(hash-set! top-dict 'FDSelect (dictify 'version 3
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'nRanges 1
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'ranges (list (dictify 'first 0 'fd 0))
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'sentinel (length (cff-subset-charstrings this))))
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(hash-ref top-dict 'FDSelect))
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(define (add-string this [string #f])
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(cond
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[(not string) #false]
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[else
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(unless (cff-subset-strings this)
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(set-cff-subset-strings! this null))
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(set-cff-subset-strings! this
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(append (cff-subset-strings this) (list string)))
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(+ (vector-length standard-strings) (sub1 (length (cff-subset-strings this))))]))
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(define (cff-subset-encode this stream)
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(subset-charstrings this)
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(define charset
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(dictify 'version (if (> (length (cff-subset-charstrings this)) 255) 2 1)
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'ranges (list (dictify 'first 1 'nLeft (- (length (cff-subset-charstrings this)) 2)))))
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(define top-dict (hash-copy (hash-ref (cff-subset-cff this) 'topDict)))
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(hash-set*! top-dict
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'Private #false
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'charset charset
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'Encoding #false
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'CharStrings (cff-subset-charstrings this))
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(for ([key (in-list '(version Notice Copyright FullName
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FamilyName Weight PostScript
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BaseFontName FontName))])
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(hash-update! top-dict key
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(λ (tdk-val) (add-string this (CFFont-string (cff-subset-cff this) tdk-val)))))
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(hash-set! top-dict 'ROS (list (add-string this "Adobe") (add-string this "Identity") 0))
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(hash-set! top-dict 'CIDCount (length (cff-subset-charstrings this)))
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(if (hash-ref (cff-subset-cff this) 'isCIDFont)
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(subset-font-dict this top-dict)
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(create-cid-fontdict this top-dict))
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(define top
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(mhasheq 'version 1
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'hdrSize (hash-ref (cff-subset-cff this) 'hdrSize)
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'offSize 4
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'header (hash-ref (cff-subset-cff this) 'header #f)
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'nameIndex (list (CFFFont-postscriptName (cff-subset-cff this)))
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'topDictIndex (list top-dict)
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'stringIndex (cff-subset-strings this)
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'globalSubrIndex (cff-subset-gsubrs this)))
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(for ([k (in-list (sort (dict-keys top-dict) symbol<?))])
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(match (dict-ref top-dict k)
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[(or (? list? (? dict?))) k]
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[val val]))
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(encode CFFTop top stream))
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#;(module+ test
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(require "font.rkt" "helper.rkt")
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(define otf (open-font (path->string fira-otf-path)))
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(define cffss (+cff-subset otf))
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cffss)
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#|
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approximates
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https://github.com/mbutterick/fontkit/blob/master/src/subset/TTFSubset.js
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|#
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(struct ttf-subset subset (glyf offset loca hmtx) #:transparent #:mutable)
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(define (+ttf-subset font [glyphs empty] [mapping (mhash)]
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[glyf #f]
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[offset #f]
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[loca #f]
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[hmtx #f])
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(define ss (ttf-subset font glyphs mapping glyf offset loca hmtx))
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(subset-add-glyph! ss 0)
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ss)
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(define (ttf-subset-add-glyph ss gid)
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;; glyph-decode unpacks the `glyf` table data corresponding to a certin gid.
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;; here, it's not necessary for non-composite glyphs
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;; because they just get copied entirely into the subset.
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;; it's just used to detect composite glyphs and handle them specially.
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;; so an optimization would be to detect composite / noncomposite without full glyph-decode.
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(define glyph (get-glyph (subset-font ss) gid))
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(define ttf-glyf-data (glyph-decode glyph))
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;; get the offset to the glyph from the loca table
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(match-define (list this-offset next-offset)
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(take (drop (hash-ref (get-table (subset-font ss) 'loca) 'offsets) gid) 2))
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(define port (get-table-stream (subset-font ss) 'glyf))
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(pos port (+ (pos port) this-offset))
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(define glyf-bytes (read-bytes (- next-offset this-offset) port))
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;; if it is a compound glyph, include its components
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(when (and ttf-glyf-data (negative? (hash-ref ttf-glyf-data 'numberOfContours)))
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(for ([ttf-glyph-component (in-list (hash-ref ttf-glyf-data 'components))])
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(define gid (subset-add-glyph! ss (ttf-glyph-component-glyph-id ttf-glyph-component)))
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;; note: this (ttf-glyph-component-pos component) is correct. It's a field of a Component object, not a port
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(bytes-copy! glyf-bytes (ttf-glyph-component-pos ttf-glyph-component) (encode uint16be gid #f))))
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;; `loca` table v0 stores offsets as half of actual value
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;; so we need an even number of bytes to encode
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(define glyf-bytes-even (if (odd? (bytes-length glyf-bytes))
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(bytes-append glyf-bytes #"0")
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glyf-bytes))
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(set-ttf-subset-glyf! ss (append (ttf-subset-glyf ss) (list glyf-bytes-even)))
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(hash-update! (ttf-subset-loca ss) 'offsets
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(λ (os)
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(append os (list (ttf-subset-offset ss)))))
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(hash-update! (ttf-subset-hmtx ss) 'metrics
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(λ (ms) (append ms
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(list (mhash 'advance (glyph-advance-width glyph)
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'bearing (hash-ref (get-glyph-metrics glyph) 'leftBearing))))))
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(set-ttf-subset-offset! ss (+ (ttf-subset-offset ss) (bytes-length glyf-bytes-even)))
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(sub1 (length (ttf-subset-glyf ss))))
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;; tables required by PDF spec:
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;; head, hhea, loca, maxp, cvt, prep, glyf, hmtx, fpgm
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;; additional tables required for standalone fonts:
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;; name, cmap, OS/2, post
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(define (clone-deep val) (deserialize (serialize val)))
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(define (ttf-subset-encode ss port)
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(set-ttf-subset-glyf! ss empty)
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(set-ttf-subset-offset! ss 0)
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(set-ttf-subset-loca! ss (mhash 'offsets empty))
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(set-ttf-subset-hmtx! ss (mhash 'metrics empty 'bearings empty))
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;; include all the glyphs used in the document
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;; not using `in-list` because we need to support adding more
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;; glyphs to the array as component glyphs are discovered & enqueued
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(for ([idx (in-naturals)]
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#:break (= idx (length (subset-glyphs ss))))
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(define gid (list-ref (subset-glyphs ss) idx))
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(ttf-subset-add-glyph ss gid))
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(define new-maxp-table (clone-deep (get-maxp-table (subset-font ss))))
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(dict-set! new-maxp-table 'numGlyphs (length (ttf-subset-glyf ss)))
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;; populate the new loca table
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(dict-update! (ttf-subset-loca ss) 'offsets (λ (vals) (append vals (list (ttf-subset-offset ss)))))
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(loca-pre-encode (ttf-subset-loca ss))
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(define new-head-table (clone-deep (get-head-table (subset-font ss))))
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(dict-set! new-head-table 'indexToLocFormat (dict-ref (ttf-subset-loca ss) x:version-key))
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(define new-hhea-table (clone-deep (get-hhea-table (subset-font ss))))
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(dict-set! new-hhea-table 'numberOfMetrics (length (dict-ref (ttf-subset-hmtx ss) 'metrics)))
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(define new-tables
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(filter cdr (dictify 'head new-head-table
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'hhea new-hhea-table
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'loca (ttf-subset-loca ss)
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'maxp new-maxp-table
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'cvt_ (and (has-table? (subset-font ss) 'cvt_)
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(get-cvt_-table (subset-font ss)))
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'prep (and (has-table? (subset-font ss) 'prep)
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(get-prep-table (subset-font ss)))
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'glyf (ttf-subset-glyf ss)
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'hmtx (ttf-subset-hmtx ss)
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'fpgm (and (has-table? (subset-font ss) 'fpgm)
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(get-fpgm-table (subset-font ss))))))
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(encode directory (mhash 'tables new-tables) port)
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(void))
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