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79 lines
3.0 KiB
Racket
79 lines
3.0 KiB
Racket
#lang fontkit/racket
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(require "gsub-processor.rkt" "gpos-processor.rkt" "glyphinfo.rkt" (prefix-in Shapers- "shapers.rkt") "shaping-plan.rkt")
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(provide (all-defined-out))
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#|
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https://github.com/mbutterick/fontkit/blob/master/src/opentype/OTLayoutEngine.js
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|#
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(define-subclass object% (OTLayoutEngine font)
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(field [glyphInfos #f]
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[shaper #f]
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[plan #f]
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[GSUBProcessor #f]
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[GPOSProcessor #f])
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#;(report/file 'starting-ot-layout-engine)
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(when (· font has-gsub-table?)
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(set-field! GSUBProcessor this (+GSUBProcessor font (or (· font GSUB) (error 'no-gsub-table)))))
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(when (· font has-gpos-table?)
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(set-field! GPOSProcessor this (+GPOSProcessor font (or (· font GPOS) (error 'no-gpos-table)))))
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(define/public (setup glyphs features script language)
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;; Map glyphs to GlyphInfo objects so data can be passed between
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;; GSUB and GPOS without mutating the real (shared) Glyph objects.
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(set! glyphInfos (map (λ (glyph) (+GlyphInfo (· this font) (· glyph id) (· glyph codePoints))) glyphs))
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;; Choose a shaper based on the script, and setup a shaping plan.
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;; This determines which features to apply to which glyphs.
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(set! shaper (Shapers-choose script))
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(set! plan (+ShapingPlan (· this font) script language))
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#;(report/file shaper)
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(send (make-object shaper) plan (· this plan) (· this glyphInfos) features))
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(define/public (substitute glyphs . _)
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(cond
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[(· this GSUBProcessor)
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#;(report/file (· this glyphInfos))
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(send (· this plan) process (· this GSUBProcessor) (· this glyphInfos))
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#;(report/file (· this glyphInfos))
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;; Map glyph infos back to normal Glyph objects
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(for/list ([glyphInfo (in-list (· this glyphInfos))])
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(send (· this font) getGlyph (· glyphInfo id) (· glyphInfo codePoints)))]
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[else glyphs]))
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(define/public (position glyphs positions . _)
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(report*/file glyphs positions shaper)
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(define static-shaper (make-object shaper))
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(when (eq? (· static-shaper zeroMarkWidths) 'BEFORE_GPOS)
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(zeroMarkAdvances positions))
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(when GPOSProcessor
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(report/file GPOSProcessor)
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(send (· this plan) process GPOSProcessor glyphInfos positions))
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(when (eq? (· static-shaper zeroMarkWidths) 'AFTER_GPOS)
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(zeroMarkAdvances positions))
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;; Reverse the glyphs and positions if the script is right-to-left
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(when (eq? (· this plan direction) 'rtl)
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(set! glyphs (reverse glyphs))
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(set! positions (reverse positions)))
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(report/file (and GPOSProcessor (· GPOSProcessor features))))
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(define/public (zeroMarkAdvances positions)
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(set! positions
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(for/list ([glyphInfo (in-list glyphInfos)]
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[position (in-list positions)])
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(when (· glyphInfo isMark)
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(dict-set*! position
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'xAdvance 0
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'yAdvance 0))
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position)))
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) |