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#lang debug racket/base
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(require racket/serialize
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racket/class
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racket/list
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racket/match
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sugar/unstable/dict
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sugar/unstable/js
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"table/loca.rkt"
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"table-stream.rkt"
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"directory.rkt"
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fontland/glyph
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fontland/ttf-glyph
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xenomorph)
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(provide subset +subset ttf-subset +ttf-subset subset-include-glyph encode-to-port createSubset)
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#|
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approximates
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https://github.com/devongovett/fontkit/blob/master/src/subset/Subset.js
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|#
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; glyphs = list of glyph ids in the subset
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; mapping = of glyph ids to indexes in glyphs
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(struct subset (font glyphs mapping) #:transparent #:mutable)
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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-include-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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(encode ss p)
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p)
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(define (subset-include-glyph ss glyph-or-gid)
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(define new-gid (if (object? glyph-or-gid)
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(· glyph-or-gid id)
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glyph-or-gid))
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(hash-ref! (subset-mapping ss) new-gid
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(λ ()
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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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(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/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-include-glyph ss 0)
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ss)
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;; Returns a Subset for this font.
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(define (createSubset this)
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#;(->m Subset?)
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;; no CFF support
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#;(make-object (if (· this has-cff-table?)
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CFFSubset
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TTFSubset) this)
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(+ttf-subset this))
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(define (ttf-subset-add-glyph ss gid)
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(define glyph (getGlyph (subset-font 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 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) (take (drop (hash-ref (dump (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 buffer (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? (· ttf-glyf-data numberOfContours)))
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(for ([ttf-glyph-component (in-list (· ttf-glyf-data components))])
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(define gid (subset-include-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! buffer (ttf-glyph-component-pos ttf-glyph-component) (send uint16be encode #f gid))))
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;; skip variation shit
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(set-ttf-subset-glyf! ss (append (ttf-subset-glyf ss) (list buffer)))
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(hash-update! (ttf-subset-loca ss) 'offsets (λ (os)
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(append os (list (ttf-subset-offset ss)))))
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(hash-update! (ttf-subset-hmtx ss) 'metrics (λ (ms) (append ms
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(list (mhash 'advance (glyph-advance-width glyph)
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'bearing (· (get-glyph-metrics glyph) leftBearing))))))
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(set-ttf-subset-offset! ss (+ (ttf-subset-offset ss) (bytes-length buffer)))
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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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(require racket/sequence)
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(define (encode ss port)
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#;(output-port? . ->m . void?)
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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 maxp (clone-deep (· (get-maxp-table (subset-font ss)) to-hash)))
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(dict-set! maxp '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 head (clone-deep (· (get-head-table (subset-font ss)) to-hash)))
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(dict-set! head 'indexToLocFormat (· (ttf-subset-loca ss) version))
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(define hhea (clone-deep (· (get-hhea-table (subset-font ss)) to-hash)))
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(dict-set! hhea 'numberOfMetrics (length (· (ttf-subset-hmtx ss) metrics)))
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(define table-mhash
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(let ([mh (make-hasheq)])
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(define kvs (list 'head head
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'hhea hhea
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'loca (ttf-subset-loca ss)
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'maxp maxp
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'cvt_ (get-cvt_-table (subset-font ss))
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'prep (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 (get-fpgm-table (subset-font ss))))
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(for ([kv (in-slice 2 kvs)])
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(unless (second kv)
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(error 'encode (format "missing value for ~a" (first kv))))
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(hash-set! mh (first kv) (second kv)))
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mh))
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(send Directory encode port (mhash 'tables table-mhash))
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#;(report* (bytes-length (send stream dump)) (send stream dump))
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#;(report* (bytes-length (file->bytes "out.bin")) (file->bytes "out.bin"))
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(void)
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)
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