package psinterpreter

Import Path
	github.com/go-text/typesetting/font/cff/interpreter (on go.dev)

Dependency Relation
	imports 6 packages, and imported by one package

Involved Source Files

	    charstrings.go
	  d interpreter.go
		Package psinterpreter implement a Postscript interpreter
		required to parse .CFF files, and Type1 and Type2 Charstrings.
		This package provides the low-level mechanisms needed to
		read such formats; the data is consumed in higher level packages,
		which implement `PsOperatorHandler`.
		It also provides helpers to interpret glyph outline descriptions,
		shared between Type1 and CFF font formats.
		
		See https://adobe-type-tools.github.io/font-tech-notes/pdfs/5177.Type2.pdf
Package-Level Type Names (total 8)

	/* sort by: alphabet | popularity */
	 type ArgStack (struct)

		Fields (total 2)
			Top int32
				Effecive size currently in use. The first value to
				pop is at index Top-1

			Vals [513]float64
				// we have to use float64 to properly store floats and int32 values

		Methods (total 4)
			(*ArgStack) Clear()
				Clear clears the stack

			(*ArgStack) Pop() float64
				Pop returns the top level value and decrease `Top`
				It will panic if the stack is empty.

			(*ArgStack) PopN(numPop int32) error
				PopN check and remove the n top levels entries.
				Passing a negative `numPop` clears all the stack.

			(*ArgStack) Uint16() uint16
				Uint16 returns the top level value as uint16,
				without popping the stack.


	 type CharstringReader (struct)
		CharstringReader provides implementation
		of the operators found in a font charstring.

		Fields (total 3)
			Bounds PathBounds
				Acumulated bounds for the glyph outlines

			CurrentPoint Point
			Segments []ot.Segment
				Acumulated segments for the glyph outlines

		Methods (total 22)
			(*CharstringReader) ClosePath()
				ClosePath closes the current contour, adding
				a segment to the first point if needed.

			(*CharstringReader) Flex(state *Machine) error
			(*CharstringReader) Flex1(state *Machine) error
			(*CharstringReader) Hflex(state *Machine) error
			(*CharstringReader) Hflex1(state *Machine) error
			(*CharstringReader) Hhcurveto(state *Machine)
			(*CharstringReader) Hintmask(state *Machine)
			(*CharstringReader) Hlineto(state *Machine)
			(*CharstringReader) Hmoveto(state *Machine) error
			(*CharstringReader) Hstem(state *Machine)
			(*CharstringReader) Hvcurveto(state *Machine)
			(*CharstringReader) Rcurveline(state *Machine) error
			(*CharstringReader) RelativeCurveTo(arg1, arg2, arg3 Point)
				RelativeCurveTo draws a curve with controls points computed from
				the current point and `arg1`, `arg2`, `arg3`

			(*CharstringReader) Rlinecurve(state *Machine) error
			(*CharstringReader) Rlineto(state *Machine)
			(*CharstringReader) Rmoveto(state *Machine) error
			(*CharstringReader) Rrcurveto(state *Machine)
			(*CharstringReader) Vhcurveto(state *Machine)
			(*CharstringReader) Vlineto(state *Machine)
			(*CharstringReader) Vmoveto(state *Machine) error
			(*CharstringReader) Vstem(state *Machine)
			(*CharstringReader) Vvcurveto(state *Machine)

	 type Context uint32 (basic type)
		Context is the flavour of the Postcript language.

		As Outputs Of (at least one exported)
			func OperatorHandler.Context() Context
		As Types Of (total 4)
			const PrivateDict
			const TopDict
			const Type1Charstring
			const Type2Charstring

	 type Machine (struct)
		Machine is a PostScript interpreter.
		A same interpreter may be re-used using muliples `Run` calls.

		Fields (only one)
			ArgStack ArgStack
		Methods (total 4)
			(*Machine) CallSubroutine(index int32, isLocal bool) error
				CallSubroutine calls the subroutine, identified by its index, as found
				in the instructions (that is, before applying the subroutine biased).
				`isLocal` controls whether the local or global subroutines are used.
				No argument stack modification is performed.

			(*Machine) Return() error
				Return returns from a subroutine call.

			(*Machine) Run(instructions []byte, localSubrs, globalSubrs [][]byte, handler OperatorHandler) error
				Run runs the instructions in the PostScript context asked by `handler`.
				`localSubrs` and `globalSubrs` contains the subroutines that may be called in the instructions.

			(*Machine) SkipBytes(count int32)
				SkipBytes skips the next `count` bytes from the instructions, and clears the argument stack.
				It does nothing if `count` exceed the length of the instructions.

		As Inputs Of (at least 23)
			func GlobalSubr(state *Machine) error
			func LocalSubr(state *Machine) error
			func (*CharstringReader).Flex(state *Machine) error
			func (*CharstringReader).Flex1(state *Machine) error
			func (*CharstringReader).Hflex(state *Machine) error
			func (*CharstringReader).Hflex1(state *Machine) error
			func (*CharstringReader).Hhcurveto(state *Machine)
			func (*CharstringReader).Hintmask(state *Machine)
			func (*CharstringReader).Hlineto(state *Machine)
			func (*CharstringReader).Hmoveto(state *Machine) error
			func (*CharstringReader).Hstem(state *Machine)
			func (*CharstringReader).Hvcurveto(state *Machine)
			func (*CharstringReader).Rcurveline(state *Machine) error
			func (*CharstringReader).Rlinecurve(state *Machine) error
			func (*CharstringReader).Rlineto(state *Machine)
			func (*CharstringReader).Rmoveto(state *Machine) error
			func (*CharstringReader).Rrcurveto(state *Machine)
			func (*CharstringReader).Vhcurveto(state *Machine)
			func (*CharstringReader).Vlineto(state *Machine)
			func (*CharstringReader).Vmoveto(state *Machine) error
			func (*CharstringReader).Vstem(state *Machine)
			func (*CharstringReader).Vvcurveto(state *Machine)
			func OperatorHandler.Apply(state *Machine, operator Operator) error

	 type Operator (struct)
		Operator is a postcript command, which may be escaped.

		Fields (total 2)
			IsEscaped bool
			Operator byte
		Methods (only one)
			( Operator) String() string
		Implements (at least 2)
			 Operator : expvar.Var
			 Operator : fmt.Stringer
		As Inputs Of (at least one exported)
			func OperatorHandler.Apply(state *Machine, operator Operator) error

	 type OperatorHandler (interface)
		OperatorHandler defines the behaviour of an operator.

		Methods (total 2)
			( OperatorHandler) Apply(state *Machine, operator Operator) error
				Apply implements the operator defined by `operator` (which is the second byte if `escaped` is true).
				
				Returning `ErrInterrupt` stop the parsing of the instructions, without reporting an error.
				It can be used as an optimization.

			( OperatorHandler) Context() Context
				Context defines the precise behaviour of the interpreter,
				which has small nuances depending on the context.

		As Inputs Of (at least one exported)
			func (*Machine).Run(instructions []byte, localSubrs, globalSubrs [][]byte, handler OperatorHandler) error

	 type PathBounds (struct)
		PathBounds represents a control bounds for
		a glyph outline (in font units).

		Fields (total 2)
			Max Point
			Min Point
		Methods (total 2)
			(*PathBounds) Enlarge(pt Point)
				Enlarge enlarges the bounds to include pt

			(*PathBounds) ToExtents() ot.GlyphExtents
				ToExtents converts a path bounds to the corresponding glyph extents.

		As Outputs Of (at least 2)
			func github.com/go-text/typesetting/font/cff.(*CFF).LoadGlyph(glyph tables.GlyphID) ([]ot.Segment, PathBounds, error)
			func github.com/go-text/typesetting/font/cff.(*CFF2).LoadGlyph(glyph tables.GlyphID, coords []tables.Coord) ([]ot.Segment, PathBounds, error)

	 type Point (struct)
		Point is a 2D Point in font units.

		Fields (total 2)
			X float64
			Y float64
		Methods (only one)
			(*Point) Move(dx, dy float64)
				Move translates the Point.

		As Inputs Of (at least 2)
			func (*CharstringReader).RelativeCurveTo(arg1, arg2, arg3 Point)
			func (*PathBounds).Enlarge(pt Point)


Package-Level Functions (total 2)

	 func GlobalSubr(state *Machine) error
		GlobalSubr pops the subroutine index and call it

	 func LocalSubr(state *Machine) error
		LocalSubr pops the subroutine index and call it


Package-Level Variables (only one)

	  var ErrInterrupt error
		ErrInterrupt signals the interpreter to stop early, without erroring.


Package-Level Constants (total 4)

	const PrivateDict Context = 1 // Private dict in CFF files
	const TopDict Context = 0 // Top dict in CFF files
	const Type1Charstring Context = 3 // Charstring in Type1 font files
	const Type2Charstring Context = 2 // Charstring in CFF files

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