resume in ttfglyph:decodeSimple
parent
af3938170c
commit
2fc8afff93
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#lang fontkit/racket
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(require "glyph.rkt" restructure)
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(provide (all-defined-out))
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;; The header for both simple and composite glyphs
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(define-subclass Struct (RGlyfHeader))
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(define GlyfHeader (+RGlyfHeader
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(dictify 'numberOfContours int16be ;; if negative, this is a composite glyph
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'xMin int16be
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'yMin int16be
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'xMax int16be
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'yMax int16be)))
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;; Flags for simple glyphs
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(define ON_CURVE (expt 2 0))
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(define X_SHORT_VECTOR (expt 2 1))
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(define Y_SHORT_VECTOR (expt 2 2))
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(define REPEAT (expt 2 3))
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(define SAME_X (expt 2 4))
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(define SAME_Y (expt 2 5))
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;; Flags for composite glyphs
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(define ARG_1_AND_2_ARE_WORDS (expt 2 0))
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(define ARGS_ARE_XY_VALUES (expt 2 1))
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(define ROUND_XY_TO_GRID (expt 2 2))
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(define WE_HAVE_A_SCALE (expt 2 3))
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(define MORE_COMPONENTS (expt 2 5))
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(define WE_HAVE_AN_X_AND_Y_SCALE (expt 2 6))
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(define WE_HAVE_A_TWO_BY_TWO (expt 2 7))
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(define WE_HAVE_INSTRUCTIONS (expt 2 8))
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(define USE_MY_METRICS (expt 2 9))
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(define OVERLAP_COMPOUND (expt 2 10))
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(define SCALED_COMPONENT_OFFSET (expt 2 11))
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(define UNSCALED_COMPONENT_OFFSET (expt 2 12))
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;; Represents a point in a simple glyph
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(define-subclass object% (Point onCurve endContour [x 0] [y 0])
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(define/public (copy)
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(+Point onCurve endContour x y)))
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;; Represents a component in a composite glyph
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(define-subclass object% (Component glyphID dx dy)
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(field [pos 0]
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[scaleX 1]
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[scaleY 1]
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[scale01 0]
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[scale10 0])
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)
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;; Represents a TrueType glyph.
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(define-subclass Glyph (TTFGlyph)
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(inherit-field _font id)
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;; Parses just the glyph header and returns the bounding box
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(define/override (_getCBox internal)
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(unfinished))
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;; Parses a single glyph coordinate
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(define/public (_parseGlyphCoord steam prev short same)
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(unfinished))
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;; Decodes the glyph data into points for simple glyphs,
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;; or components for composite glyphs
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(define/public (_decode)
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(define offsets (hash-ref (send _font _getTable 'loca) 'offsets))
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(define glyfPos (list-ref offsets id))
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(define nextPos (list-ref offsets (add1 id)))
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;; Nothing to do if there is no data for this glyph
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(unless (= glyfPos nextPos)
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(define stream (send _font _getTableStream 'glyf))
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(increment-field! pos stream glyfPos)
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(define startPos (· stream pos))
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(define glyph (send GlyfHeader decode stream))
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(let ([contour-count (· glyph numberOfContours)])
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(cond
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[(positive? contour-count)
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(_decodeSimple glyph stream)]
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[(negative? contour-count)
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(_decodeComposite glyph stream startPos)]))
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glyph))
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(define/public (_decodeSimple glyph stream)
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(unless (RGlyfHeader? glyph)
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(raise-argument-error 'TTFGlyph-_decodeSimple "glyph" glyph))
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(unless (DecodeStream? stream)
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(raise-argument-error 'TTFGlyph-_decodeSimple "stream" stream))
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;; this is a simple glyph
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(hash-set! glyph 'points empty)
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(define endPtsOfContours (send (+Array uint16be (· glyph numberOfContours)) decode stream))
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(hash-set! glyph 'instructions (send (+Array uint8be uint16be) decode stream))
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(define numCoords (add1 (list-ref endPtsOfContours (sub1 (length endPtsOfContours)))))
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(define flags
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(reverse
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(for/fold ([flags empty])
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([i (in-naturals)]
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#:when (< (length flags) numCoords))
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(define flag (send stream readUInt8))
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;; check for repeat flag
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(define repeated-flags
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(cond
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[(not (zero? (bitwise-and flag REPEAT)))
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(define count (send stream readUInt8))
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(make-list count flag)]
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[else empty]))
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(append repeated-flags (cons flag flags)))))
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(unfinished))
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(define/public (_decodeComposite glyph stream [offset 0])
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(unfinished)))
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