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93 lines
3.2 KiB
Racket
93 lines
3.2 KiB
Racket
#lang fontkit/racket
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(require (prefix-in Script- "script.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/opentype/ShapingPlan.js
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|#
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; * ShapingPlans are used by the OpenType shapers to store which
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; * features should by applied, and in what order to apply them.
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; * The features are applied in groups called stages. A feature
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; * can be applied globally to all glyphs, or locally to only
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; * specific glyphs.
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(define-subclass object% (ShapingPlan font script language)
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(field [direction (Script-direction script)]
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[stages empty]
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[globalFeatures (mhasheq)]
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[allFeatures (mhasheq)])
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;; Adds the given features to the last stage.
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;; Ignores features that have already been applied.
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(define/public (_addFeatures features)
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#;(report*/file 'stages-before stages)
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(match-define (list head-stages ... last-stage) stages)
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(set! stages
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`(,@head-stages
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,(append last-stage
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(for/list ([feature (in-list features)]
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#:unless (dict-ref (· this allFeatures) feature #f))
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(dict-set! (· this allFeatures) feature #t)
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feature))))
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#;(report*/file 'stages-after stages)
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stages)
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;; Adds the given features to the global list
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(define/public (_addGlobal features)
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(for ([feature (in-list features)])
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(dict-set! (· this globalFeatures) feature #t)))
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;; Add features to the last stage
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(define/public (add arg [global #t])
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(when (zero? (length (· this stages)))
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(push-end-field! stages this empty))
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(when (string? arg)
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(set! arg (list arg)))
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(cond
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[(list? arg)
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(_addFeatures arg)
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(when global (_addGlobal arg))]
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[(dict? arg)
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(define features (append (or (· arg global) empty)
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(or (· arg local) empty)))
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(_addFeatures features)
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(when (· arg global)
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(_addGlobal (· arg global)))]
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[else (raise-argument-error 'ShapingPlan:add "valid arg" arg)]))
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;; Add a new stage
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(define/public (addStage arg global)
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(cond
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[(procedure? arg)
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(push-end-field! stages this arg)
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(push-end-field! stages this empty)]
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[else (push-end-field! stages this empty)
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(add arg global)]))
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;; Assigns the global features to the given glyphs
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(define/public (assignGlobalFeatures glyphs)
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#;(report*/file glyphs (· this globalFeatures))
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(for* ([glyph (in-list glyphs)]
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[feature (in-dict-keys (· this globalFeatures))])
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(dict-set! (· glyph features) feature #t)))
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;; Executes the planned stages using the given OTProcessor
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(define/public (process processor glyphs [positions #f])
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#;(report*/file 'shaping-plan-process processor)
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(send processor selectScript (· this script) (· this language))
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#;(report/file stages)
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(for ([stage (in-list stages)])
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(cond
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[(and (procedure? stage) (not positions))
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(stage (· this font) glyphs positions)]
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[(> (length stage) 0)
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#;(report*/file 'shaping-plan:applying-features processor)
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(send processor applyFeatures stage glyphs positions)]))))
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