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89 lines
3.2 KiB
Racket
89 lines
3.2 KiB
Racket
7 years ago
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#lang fontkit/racket
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(require xenomorph br/cond "opentype.rkt")
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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/GSUB.js
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|#
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(define Sequence (+Array uint16be uint16be))
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(define AlternateSet Sequence)
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(define Ligature (+Struct
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(dictify
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'glyph uint16be
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'compCount uint16be
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'components (+Array uint16be (λ (t) (sub1 (· t compCount)))))))
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(define LigatureSet (+Array (+Pointer uint16be Ligature) uint16be))
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(define-subclass VersionedStruct (GSUBLookup-VersionedStruct))
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(define GSUBLookup
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(+GSUBLookup-VersionedStruct
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'lookupType
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(dictify
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;; Single Substitution
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1 (+VersionedStruct uint16be
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(dictify
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1 (dictify
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'coverage (+Pointer uint16be Coverage)
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'deltaGlyphID int16be)
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2 (dictify
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'coverage (+Pointer uint16be Coverage)
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'glyphCount uint16be
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'substitute (+LazyArray uint16be 'glyphCount))))
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2 ;; Multiple Substitution
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(dictify
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'substFormat uint16be
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'coverage (+Pointer uint16be Coverage)
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'count uint16be
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'sequences (+LazyArray (+Pointer uint16be Sequence) 'count))
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3 ;; Alternate Substitution
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(dictify
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'substFormat uint16be
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'coverage (+Pointer uint16be Coverage)
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'count uint16be
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'alternateSet (+LazyArray (+Pointer uint16be AlternateSet) 'count))
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4 ;; Ligature Substitution
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(dictify
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'substFormat uint16be
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'coverage (+Pointer uint16be Coverage)
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'count uint16be
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'ligatureSets (+LazyArray (+Pointer uint16be LigatureSet) 'count))
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5 Context ;; Contextual Substitution
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6 ChainingContext ;; Chaining Contextual Substitution
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7 ;; Extension Substitution
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(dictify
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'substFormat uint16be
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'lookupType uint16be ; cannot also be 7
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'extension (+Pointer uint32be (λ () (error 'circular-reference-unfixed))))
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8 ;; Reverse Chaining Contextual Single Substitution
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(dictify
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'substFormat uint16be
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'coverage (+Pointer uint16be Coverage)
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'backTrackCoverage (+Array (+Pointer uint16be Coverage) 'backtrackGlyphCount)
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'lookaheadGlyphCount uint16be
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'lookaheadCoverage (+Array (+Pointer uint16be Coverage) 'lookaheadGlyphCount)
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'glyphCount uint16be
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'substitute (+Array uint16be 'glyphCount)))))
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;; Fix circular reference
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(ref*-set! GSUBLookup 'versions 7 'extension 'type GSUBLookup)
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(define-subclass VersionedStruct (GSUB-MainVersionedStruct))
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(define GSUB (+GSUB-MainVersionedStruct uint32be
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(dictify
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'header (dictify 'scriptList (+Pointer uint16be ScriptList)
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'featureList (+Pointer uint16be FeatureList)
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'lookupList (+Pointer uint16be (LookupList GSUBLookup))
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)
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#x00010000 (dictify)
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#;#x00010001 #;(+Pointer uint32be FeatureVariations))))
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(test-module)
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