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#lang fontkit/racket
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(require restructure 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/GPOS.js
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|#
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(define ValueFormat (+Bitfield uint16be '(xPlacement yPlacement xAdvance yAdvance xPlaDevice yPlaDevice xAdvDevice yAdvDevice)))
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(define types
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(mhash
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'xPlacement int16be
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'yPlacement int16be
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'xAdvance int16be
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'yAdvance int16be
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'xPlaDevice uint16be ;; pointer
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'yPlaDevice uint16be ;; pointer
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'xAdvDevice uint16be ;; pointer
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'yAdvDevice uint16be)) ;; pointer
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(define-subclass object% (ValueRecord [key 'valueFormat])
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(define/public (buildStruct parent)
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;; set `struct` to the first Struct object in the chain of ancestors
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;; with the target key
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(define struct (let loop ([x parent])
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(cond
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[(and x (Struct? x) (dict-ref (· x res) key #f)) x]
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[(· x parent) => loop]
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[else #f])))
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(and struct
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(let ()
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(define format (dict-ref (· struct res) key))
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(define fields
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(append
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(dictify 'rel (λ _ (report (get-field _startOffset struct))))
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(for/list ([(key val) (in-dict format)]
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#:when val)
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(cons key (dict-ref types key)))))
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(+Struct fields))))
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(define/public (size val ctx)
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(send (buildStruct ctx) size val ctx))
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(define/public (decode stream parent)
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(define res (send (buildStruct parent) decode stream parent))
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(hash-remove! res 'rel)
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res)
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(define/public (encode . args)
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(error 'GPOS-encode-not-implemented)))
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(define PairValueRecord (+Struct
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(dictify
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'secondGlyph uint16be
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'value1 (+ValueRecord 'valueFormat1)
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'value2 (+ValueRecord 'valueFormat2))))
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(define PairSet (+Array PairValueRecord uint16be))
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(define Class2Record (+Struct
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(dictify
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'value1 (+ValueRecord 'valueFormat1)
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'value2 (+ValueRecord 'valueFormat2))))
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(define Anchor (+VersionedStruct uint16be
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(dictify
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;; Design units only
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1 (dictify 'xCoordinate int16be
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'yCoordinate int16be)
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;; Design units plus contour point
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2 (dictify 'xCoordinate int16be
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'yCoordinate int16be
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'anchorPoint uint16be)
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;; Design units plus Device tables
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3 (dictify 'xCoordinate int16be
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'yCoordinate int16be
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'xDeviceTable uint16be ; pointer
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'yDeviceTable uint16be)))) ; pointer
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(define EntryExitRecord (+Struct
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(dictify 'entryAnchor uint16be ; pointer
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'exitAnchor uint16be))) ; pointer
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(define MarkRecord (+Struct
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(dictify 'class uint16be
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'markAnchor uint16be)))
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(define MarkArray (+Array MarkRecord uint16be))
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(define BaseRecord (+Array uint16be)) ; pointer
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(define BaseArray (+Array BaseRecord uint16be))
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(define ComponentRecord (+Array uint16be)) ; pointer
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(define LigatureAttach (+Array ComponentRecord uint16be))
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(define LigatureArray (+Array uint16be uint16be)) ; pointer
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(define-subclass VersionedStruct (GPOSLookup-VersionedStruct))
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(define GPOSLookup
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(+GPOSLookup-VersionedStruct
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'lookupType
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(dictify
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;; Single Adjustment
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1 (+VersionedStruct uint16be
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(dictify
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;; Single positioning value
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1 (dictify
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'coverage (+Pointer uint16be Coverage)
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'valueFormat ValueFormat
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'value (+ValueRecord))
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2 (dictify
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'coverage uint16be ; pointer
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'valueFormat ValueFormat
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'valueCount uint16be
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'values (+LazyArray (+ValueRecord) 'valueCount))))
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;; Pair Adjustment Positioning
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2 (+VersionedStruct uint16be
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(dictify
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;; Adjustments for glyph pairs
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1 (dictify
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'coverage uint16be ; pointer
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'valueFormat1 ValueFormat
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'valueFormat2 ValueFormat
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'pairSetCount uint16be
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'pairSets (+LazyArray uint16be 'pairSetCount)) ; pointer
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;; Class pair adjustment
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2 (dictify
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'coverage uint16be ; pointer
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'valueFormat1 ValueFormat
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'valueFormat2 ValueFormat
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'classDef1 uint16be ; pointer
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'classDef2 uint16be ; pointer
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'class1Count uint16be
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'class2Count uint16be
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'classRecords (+LazyArray (+LazyArray Class2Record 'class2Count) 'class1Count))))
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;; Cursive Attachment Positioning
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3 (dictify
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'format uint16be
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'coverage uint16be ; pointer
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'entryExitCount uint16be
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'entryExitRecords (+Array EntryExitRecord 'entryExitCount))
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;; MarkToBase Attachment Positioning
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4 (dictify
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'format uint16be
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'markCoverage uint16be ; pointer
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'baseCoverage uint16be ; pointer
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'classCount uint16be
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'markArray uint16be ; pointer
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'baseArray uint16be) ; pointer
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;; MarkToLigature Attachment Positioning
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5 (dictify
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'format uint16be
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'markCoverage uint16be ; pointer
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'ligatureCoverage uint16be ; pointer
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'classCount uint16be
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'markArray uint16be ; pointer
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'ligatureArray uint16be)
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;; MarkToMark Attachment Positioning
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6 (dictify
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'format uint16be
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'mark1Coverage uint16be ; pointer
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'mark2Coverage uint16be ; pointer
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'classCount uint16be
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'mark1Array uint16be ; pointer
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'mark2Array uint16be) ; pointer
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7 Context ;; Contextual positioning
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8 ChainingContext ;; Chaining contextual positioning
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;; Extension positioning
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9 (dictify
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'posFormat uint16be
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'lookupType uint16be ;; cannot also be 9
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'extension uint32be) ; pointer
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)))
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;; Fix circular reference
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;; GPOSLookup.versions[9].extension.type = GPOSLookup;
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(define gpos-common-dict (dictify 'scriptList (+Pointer uint16be ScriptList)
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'featureList (+Pointer uint16be FeatureList)
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'lookupList (+Pointer uint16be (LookupList GPOSLookup))
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))
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(define-subclass VersionedStruct (GPOS-MainVersionedStruct))
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(define GPOS (+GPOS-MainVersionedStruct uint32be
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(dictify
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#x00010000 gpos-common-dict
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;; ignore variations
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#;#x00010001 #;(append gpos-common-dict (dictify 'featureVariations (+Pointer uint32be FeatureVariations))))))
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(test-module)
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