A2OS/source/OpenTypeInt.Mod

MODULE OpenTypeInt; (** AUTHOR "eos, PL"; PURPOSE "Bluebottle port of OpenType"; *)

CONST
	X* = 1; Y* = 0;							(** indices for coordinates into Coord structure **)

	StackSize* = 8192;

TYPE
	F26D6* = LONGINT;						(** fixed point format 26.6 used for fractional pixel coordinates **)
	F2D14* = INTEGER;						(** fixed point format 2.14 used for unit vectors **)
	FUnit* = INTEGER;						(** unscaled point coordinates **)
	Fixed* = LONGINT;						(** fixed point format 16.16 used for scalar fixed point numbers **)

	(** program code **)
	Code* = POINTER TO ARRAY OF CHAR;

	(** program stack **)
	Stack* = ARRAY StackSize OF LONGINT;

	(** addresses within code blocks **)
	Address* = RECORD
		code*: Code;						(** instruction sequence **)
		len*: LONGINT;						(** code length **)
		pc*: LONGINT;						(** location within code **)
	END;

	(** user defined functions **)
	Functions* = POINTER TO ARRAY OF Address;

	(** user defined instructions **)
	Instruction* = RECORD
		beg*: Address;						(* starting point *)
		opcode*: CHAR;						(* instruction opcode *)
	END;
	Instructions* = POINTER TO ARRAY OF Instruction;

	(** call stack **)
	Frame* = RECORD
		ret*: Address;						(* return address *)
		start*: LONGINT;					(* starting pc of function (within context.code) *)
		count*: INTEGER;					(* number of times the function has to be evaluated *)
	END;
	CallStack* = ARRAY 32 OF Frame;

	(** program store **)
	Store* = POINTER TO ARRAY OF LONGINT;

	(** control value table **)
	CVT* = POINTER TO ARRAY OF F26D6;

	(** glyph zone **)
	Contours* = POINTER TO ARRAY OF INTEGER;
	Coord* = ARRAY 2 OF F26D6;
	Point* = RECORD
		org*, cur*: Coord;					(** original and current point coordinates **)
		onCurve*: BOOLEAN;				(** is point on or off the curve? **)
		touched*: ARRAY 2 OF BOOLEAN;	(** is point touched in x/y direction? **)
	END;
	Points* = POINTER TO ARRAY OF Point;

	Zone* = POINTER TO ZoneDesc;
	ZoneDesc* = RECORD
		contours*: INTEGER;					(** number of contours in this zone **)
		first*: Contours;						(** starting points of each contour; first[contours] contains total number of points in zone **)
		pt*: Points;							(** points in this zone **)
	END;

	(** unit vector **)
	Vector* = RECORD
		x*, y*: F2D14;
	END;

	(** execution context **)
	Context* = RECORD
		code*: Code;						(** program code **)
		codeLen*: LONGINT;				(* code length *)
		stack*: Stack;						(** program stack **)
		callStack*: CallStack;				(** call stack of program **)
		pc*: LONGINT;						(* current position within code *)
		tos*: INTEGER;						(* stack pointer *)
		ctos*: INTEGER;						(* call stack pointer *)

		func*: Functions;					(** user defined functions **)
		instr*: Instructions;					(** user defined instructions **)
		store*: Store;						(** program store **)
		cvt*: CVT;							(** control value table **)
		zone*: ARRAY 2 OF Zone;			(** twilight and glyph zone **)

		ptsize*: F26D6;						(** current point size **)
		xppm*, yppm*, ppm: F26D6;			(** number of pixels per Em in x/y direction **)
		upm*: INTEGER;						(** units per Em **)
		rotated*, stretched*: BOOLEAN;		(* glyph transformation info *)
		xratio, yratio, ratio*: Fixed;			(** aspect ratio **)

		minDist*: F26D6;					(** feature preserving minimum distance **)
		cvtCutIn*: F26D6;					(** control value table cut in **)
		swVal*, swCutIn*: F26D6;			(** single width cut in and single width value **)
		deltaBase*, deltaShift*: INTEGER;	(** delta exception parameters **)
		autoFlip*: BOOLEAN;				(** whether to make CVT entries sign independent **)
		inhibitFit*, ignorePrep*: BOOLEAN;	(** instruction control flags **)
		fixDropouts*: BOOLEAN;			(** scan control flag **)
		scanType*: INTEGER;				(** current scan type **)

		rp0*, rp1*, rp2*: INTEGER;			(** reference points **)
		gep0*, gep1*, gep2*: INTEGER;		(** zone indices **)
		zp0, zp1, zp2: Zone;					(* zone pointers, equal to zone[gepN] *)
		free*, proj*, proj2*: Vector;			(** freedom vector, projection vector, and dual projection vector **)
		period*, phase*, threshold*: F26D6;	(** parameters of current round state **)
		loop*: INTEGER;						(** number of times to execute the next loop-aware instruction **)
	END;

	(** static part of graphics state **)
	State* = RECORD
		minDist: F26D6;
		cvtCutIn: F26D6;
		swVal, swCutIn: F26D6;
		deltaBase, deltaShift: INTEGER;
		autoFlip: BOOLEAN;
		inhibitFit, ignorePrep: BOOLEAN;
		fixDropouts: BOOLEAN;
		scanType: INTEGER;
	END;

	(** debug upcalls **)
	NotifierData* = POINTER TO NotifierDesc;
	NotifierDesc* = RECORD END;
	Notifier* = PROCEDURE (VAR c: Context; data: NotifierData);

	Primitive = PROCEDURE (VAR c: Context);


VAR
	EmptyZone*: Zone;					(** zone containing zero contours and zero points **)
	Builtin: ARRAY 256 OF Primitive;		(* instruction for each opcode *)
	Notify: Notifier;
	NotifyData: NotifierData;



(**--- Arithmetic ---**)

PROCEDURE ShiftDiv* (a, n, d: LONGINT): LONGINT;
	VAR b: LONGINT; 
BEGIN
	b := ASH( 1, 31-n );
	IF (-b <= a) & (a < b) THEN
		RETURN (ASH( a, n ) + d DIV 2) DIV d
	ELSE
		RETURN SHORT(  (ASH( LONG(a), n ) + d DIV 2) DIV d )
	END;
END ShiftDiv;

PROCEDURE MulShift* (a, b, n: LONGINT): LONGINT;
BEGIN
	IF (-10000H <= a) & (a < 10000H) & (-8000H <= b) & (b < 8000H) THEN
		RETURN ASH(a * b, n)
	ELSE
		RETURN SHORT( ASH(LONG(a) * b, n) )
	END
END MulShift;

PROCEDURE MulDiv*( a, b, c: LONGINT ): LONGINT;
BEGIN
	IF (-10000H <= a) & (a < 10000H) & (-8000H <= b) & (b < 8000H) THEN
		IF c > 0 THEN
			RETURN (a * b + c DIV 2) DIV c
		ELSIF c < 0 THEN
			c := -c;
			RETURN -((a * b + c DIV 2) DIV c)
		ELSE
			RETURN 0; (* division by zero -- gracefully ignored ... *)
			HALT(100);  (* a trap is an inacceptable behavior during system startup (e.g. if the font is too small ..) *)
		END
	ELSE
		IF c > 0 THEN
			RETURN SHORT( (LONG(a) * b + c DIV 2) DIV c )
		ELSIF c < 0 THEN
			c := -c;
			RETURN SHORT( -((LONG(a) * b + c DIV 2) DIV c) )
		ELSE
			RETURN 0; (* division by zero -- gracefully ignored ... *)
			HALT(100);  (* a trap is an inacceptable behavior during system startup (e.g. if the font is too small ..) *)
		END
	END
END MulDiv;

PROCEDURE Norm*( x, y: F26D6 ): F26D6;
	VAR n, r, b, t: LONGINT; nh, rh, bh, th: HUGEINT;
BEGIN
	IF (-8000H <= x) & (x < 8000H) & (-8000H <= y) & (y < 8000H) THEN	
		(* x*x + y*y representable in 32 bits *)
		n := x * x + y * y;
		r := 0; b := 40000000H;
		REPEAT
			t := r + b;
			IF t <= n THEN
				DEC(n, t);
				r := t + b
			END;
			r := r DIV 2;  b := b DIV 4
		UNTIL b = 0
	ELSE
		nh := LONG(x)*LONG(x) + LONG(y)*LONG(y);
		rh := 0;  bh := 4000000000000000H;
		REPEAT
			th := rh + bh;
			IF th <= nh THEN
				nh := nh - th;
				rh := th + bh
			END;
			rh := rh DIV 2;  bh := bh DIV 4
		UNTIL bh = 0;
		r := SHORT(rh)
	END;
	RETURN r
END Norm;


(*--- Auxiliary Routines ---*)

PROCEDURE Ratio (VAR c: Context): Fixed;
	VAR x, y: Fixed;
BEGIN
	IF c.ratio = 0 THEN
		IF c.proj.y = 0 THEN
			c.ratio := c.xratio
		ELSIF c.proj.x = 0 THEN
			c.ratio := c.yratio
		ELSE
			x := ASH(c.proj.x * c.xratio, -14);
			y := ASH(c.proj.y * c.yratio, -14);
			c.ratio := Norm(x, y)
		END
	END;
	RETURN c.ratio
END Ratio;

PROCEDURE PPEm (VAR c: Context): F26D6;
BEGIN
	RETURN MulShift(c.ppm, Ratio(c), -16)
END PPEm;

PROCEDURE FUnitToPixel (fu: FUnit; VAR c: Context): F26D6;
BEGIN
	RETURN (LONG(fu) * PPEm(c) + c.upm DIV 2) DIV c.upm
END FUnitToPixel;

PROCEDURE CVTValue (n: LONGINT; VAR c: Context): F26D6;
	VAR ratio: F26D6;
BEGIN
	IF n < 0 THEN
		RETURN 0	(* some fonts use CVT[-1]; FreeType and TTI return 0, too *)
	ELSE
		ratio := Ratio(c);
		IF ratio = 10000H THEN  RETURN c.cvt[n]
		ELSE  RETURN MulShift(c.cvt[n], ratio, -16)
		END
	END
END CVTValue;

PROCEDURE Round (x, period, phase, threshold: F26D6): F26D6;
	VAR sign: F26D6;
BEGIN
	sign := x; x := ABS(x);
	x := x - phase + threshold;
	x := x - x MOD period + phase;
	IF x < 0 THEN  INC(x, period)  END;
	IF sign < 0 THEN  x := -x  END;
	RETURN x
END Round;

PROCEDURE Project (crd: Coord; proj: Vector): F26D6;
BEGIN
	RETURN MulShift(crd[X], proj.x, -14) + MulShift(crd[Y], proj.y, -14)	(* dot product of point and unit vector *)
END Project;

PROCEDURE GetDistance (from, to: Coord; VAR dx, dy: F26D6);
BEGIN
	dx := to[X] - from[X]; dy := to[Y] - from[Y]
END GetDistance;

PROCEDURE Move (VAR p: Point; free, proj: Vector; dist: F26D6);
	VAR dot: LONGINT;
BEGIN
	IF proj.x = 4000H THEN
		IF free.x # 0 THEN
			INC(p.cur[X], dist); p.touched[X] := TRUE;
			IF free.x # 4000H THEN
				INC(p.cur[Y], MulDiv(free.y, dist, free.x)); p.touched[Y] := TRUE
			END
		END
	ELSIF proj.y = 4000H THEN
		IF free.y # 0 THEN
			INC(p.cur[Y], dist); p.touched[Y] := TRUE;
			IF free.y # 4000H THEN
				INC(p.cur[X], MulDiv(free.x, dist, free.y)); p.touched[X] := TRUE
			END
		END
	ELSE
		dot := LONG(proj.x) * LONG(free.x) + LONG(proj.y) * LONG(free.y);
		INC(p.cur[X], MulDiv(4000H*LONG(free.x), dist, dot));  p.touched[X] := TRUE;
		INC(p.cur[Y], MulDiv(4000H*LONG(free.y), dist, dot));  p.touched[Y] := TRUE
	END
END Move;

PROCEDURE GetRefDist (VAR c: Context; flag: BOOLEAN; VAR zone: Zone; VAR ref: LONGINT; VAR dx, dy: F26D6);
	VAR dot: LONGINT; dist: F26D6;
BEGIN
	IF flag THEN	(* rp1 in zp0 *)
		ref := c.rp1; zone := c.zp0
	ELSE	(* use rp2 in zp1 *)
		ref := c.rp2; zone := c.zp1
	END;
	dist := Project(zone.pt[ref].cur, c.proj) - Project(zone.pt[ref].org, c.proj);
	dot := LONG(c.proj.x) * LONG(c.free.x) + LONG(c.proj.y) * LONG(c.free.y);
	IF dot # 0 THEN
		IF (c.free.x # 0) & (c.free.y # 0) THEN
			dx := MulDiv(c.free.x, dist, dot);
			dy := MulDiv(c.free.y, dist, dot)
		ELSIF c.free.x # 0 THEN
			dx := dist; dy := 0
		ELSIF c.free.y # 0 THEN
			dy := dist; dx := 0
		END
	ELSE
		dx := 0; dy := 0
	END
END GetRefDist;


(*--- Pushing Data onto the Interpreter Stack ---*)

(* push n bytes *)
PROCEDURE NPUSHB (VAR c: Context);
	VAR n: LONGINT;
BEGIN
	INC(c.pc); n := ORD(c.code[c.pc]);
	WHILE n > 0 DO
		INC(c.pc); INC(c.tos); c.stack[c.tos] := ORD(c.code[c.pc]);
		DEC(n)
	END;
	INC(c.pc)
END NPUSHB;

(* push n words *)
PROCEDURE NPUSHW (VAR c: Context);
	VAR n, hi, lo: LONGINT;
BEGIN
	INC(c.pc); n := ORD(c.code[c.pc]);
	WHILE n > 0 DO
		INC(c.pc); hi := ORD(c.code[c.pc]);
		IF hi >= 128 THEN DEC(hi, 256) END;
		INC(c.pc); lo := ORD(c.code[c.pc]);
		INC(c.tos); c.stack[c.tos] := 256*hi + lo;
		DEC(n)
	END;
	INC(c.pc)
END NPUSHW;

(* push bytes *)
PROCEDURE PUSHB (VAR c: Context);
	VAR n: LONGINT;
BEGIN
	n := ORD(c.code[c.pc]) - 0B0H;
	WHILE n >= 0 DO
		INC(c.pc); INC(c.tos); c.stack[c.tos] := ORD(c.code[c.pc]);
		DEC(n)
	END;
	INC(c.pc)
END PUSHB;

(* push words *)
PROCEDURE PUSHW (VAR c: Context);
	VAR n, hi, lo: LONGINT;
BEGIN
	n := ORD(c.code[c.pc]) - 0B8H;
	WHILE n >= 0 DO
		INC(c.pc); hi := ORD(c.code[c.pc]);
		IF hi >= 128 THEN DEC(hi, 256) END;
		INC(c.pc); lo := ORD(c.code[c.pc]);
		INC(c.tos); c.stack[c.tos] := 256*hi + lo;
		DEC(n)
	END;
	INC(c.pc)
END PUSHW;


(*--- Managing the Storage Area ---*)

(* read store *)
PROCEDURE RS (VAR c: Context);
BEGIN
	c.stack[c.tos] := c.store[c.stack[c.tos]]; INC(c.pc)
END RS;

(* write store *)
PROCEDURE WS (VAR c: Context);
	VAR value: LONGINT;
BEGIN
	value := c.stack[c.tos]; DEC(c.tos);
	c.store[c.stack[c.tos]] := value; DEC(c.tos);
	INC(c.pc)
END WS;


(*--- Managing the Control Value Table ---*)

(* write control value table in pixels or FUnits *)
PROCEDURE WCVT (VAR c: Context);
	VAR value: F26D6;
BEGIN
	value := c.stack[c.tos]; DEC(c.tos);
	IF c.code[c.pc] = 70X THEN
		value := FUnitToPixel(SHORT(value), c)
	END;
	c.cvt[c.stack[c.tos]] := ShiftDiv(value, 16, Ratio(c)); DEC(c.tos);
	INC(c.pc)
END WCVT;

(* read control value table *)
PROCEDURE RCVT (VAR c: Context);
BEGIN
	c.stack[c.tos] := CVTValue(c.stack[c.tos], c); INC(c.pc)
END RCVT;


(*--- Managing the Graphics State ---*)

(* set freedom and projection vectors to coordinate axis *)
PROCEDURE SVTCA (VAR c: Context);
BEGIN
	IF ODD(ORD(c.code[c.pc])) THEN	(* set to x-axis *)
		c.proj.x := 4000H; c.proj.y := 0
	ELSE	(* set to y-axis *)
		c.proj.x := 0; c.proj.y := 4000H
	END;
	c.free := c.proj;  c.proj2 := c.proj;
	c.ratio := 0;
	INC(c.pc)
END SVTCA;

(* set projection vector to coordinate axis *)
PROCEDURE SPVTCA (VAR c: Context);
BEGIN
	IF ODD(ORD(c.code[c.pc])) THEN	(* set to x-axis *)
		c.proj.x := 4000H; c.proj.y := 0
	ELSE	(* set to y-axis *)
		c.proj.x := 0; c.proj.y := 4000H
	END;
	c.proj2 := c.proj;
	c.ratio := 0;
	INC(c.pc)
END SPVTCA;

(* set freedom vector to coordinate axis *)
PROCEDURE SFVTCA (VAR c: Context);
BEGIN
	IF ODD(ORD(c.code[c.pc])) THEN	(* set to x-axis *)
		c.free.x := 4000H; c.free.y := 0
	ELSE	(* set to y-axis *)
		c.free.x := 0; c.free.y := 4000H
	END;
	INC(c.pc)
END SFVTCA;

(* set projection vector to line *)
PROCEDURE SPVTL (VAR c: Context);
	VAR p1, p2: LONGINT; dx, dy, d: F26D6;
BEGIN
	p1 := c.stack[c.tos]; DEC(c.tos);
	p2 := c.stack[c.tos]; DEC(c.tos);
	GetDistance(c.zp2.pt[p1].cur, c.zp1.pt[p2].cur, dx, dy);	(* note: TTI had zp1 and zp2 swapped *)
	d := Norm(dx, dy);
	IF d = 0 THEN
		dx := 0; dy := 0
	ELSE
		dx := ShiftDiv(dx, 14, d);
		dy := ShiftDiv(dy, 14, d)
	END;
	IF ODD(ORD(c.code[c.pc])) THEN	(* rotate by 90 degrees *)
		c.proj.x := SHORT(-dy); c.proj.y := SHORT(dx)
	ELSE
		c.proj.x := SHORT(dx); c.proj.y := SHORT(dy)
	END;
	c.proj2 := c.proj;
	c.ratio := 0;
	INC(c.pc)
END SPVTL;

(* set freedom vector to line *)
PROCEDURE SFVTL (VAR c: Context);
	VAR p1, p2: LONGINT; dx, dy, d: F26D6;
BEGIN
	p1 := c.stack[c.tos]; DEC(c.tos);
	p2 := c.stack[c.tos]; DEC(c.tos);
	GetDistance(c.zp2.pt[p1].cur, c.zp1.pt[p2].cur, dx, dy);	(* note: TTI had zp1 and zp2 swapped *)
	d := Norm(dx, dy);
	IF d = 0 THEN
		dx := 0; dy := 0
	ELSE
		dx := ShiftDiv(dx, 14, d);
		dy := ShiftDiv(dy, 14, d)
	END;
	IF ODD(ORD(c.code[c.pc])) THEN	(* rotate by 90 degrees *)
		c.free.x := SHORT(-dy); c.free.y := SHORT(dx)
	ELSE
		c.free.x := SHORT(dx); c.free.y := SHORT(dy)
	END;
	INC(c.pc)
END SFVTL;

(* set freedom vector to projection vector *)
PROCEDURE SFVTPV (VAR c: Context);
BEGIN
	c.free := c.proj; INC(c.pc)
END SFVTPV;

(* set dual projection vector to line *)
PROCEDURE SDPVTL (VAR c: Context);
	VAR p1, p2: LONGINT; dx, dy, d: F26D6;
BEGIN
	p1 := c.stack[c.tos]; DEC(c.tos);
	p2 := c.stack[c.tos]; DEC(c.tos);
	GetDistance(c.zp2.pt[p1].org, c.zp1.pt[p2].org, dx, dy);	(* note: TTI had zp1 and zp2 swapped *)
	d := Norm(dx, dy);
	dx := ShiftDiv(dx, 14, d);
	dy := ShiftDiv(dy, 14, d);
	IF ODD(ORD(c.code[c.pc])) THEN	(* rotate by 90 degrees *)
		c.proj2.x := SHORT(-dy); c.proj2.y := SHORT(dx)
	ELSE
		c.proj2.x := SHORT(dx); c.proj2.y := SHORT(dy)
	END;

	(* projection vector must be set as well, but with current coordinates (FreeType agrees on this) *)
	GetDistance(c.zp2.pt[p1].cur, c.zp1.pt[p2].cur, dx, dy);	(* note: TTI had zp1 and zp2 swapped *)
	d := Norm(dx, dy);
	dx := ShiftDiv(dx, 14, d);
	dy := ShiftDiv(dy, 14, d);
	IF ODD(ORD(c.code[c.pc])) THEN	(* rotate by 90 degrees *)
		c.proj.x := SHORT(-dy); c.proj.y := SHORT(dx)
	ELSE
		c.proj.x := SHORT(dx); c.proj.y := SHORT(dy)
	END;
	c.ratio := 0;
	INC(c.pc)
END SDPVTL;

(* set projection vector from stack *)
PROCEDURE SPVFS (VAR c: Context);
BEGIN
	c.proj.y := SHORT(c.stack[c.tos]); DEC(c.tos);
	c.proj.x := SHORT(c.stack[c.tos]); DEC(c.tos);
	c.proj2 := c.proj;
	c.ratio := 0;
	INC(c.pc)
END SPVFS;

(* set freedom vector from stack *)
PROCEDURE SFVFS (VAR c: Context);
BEGIN
	c.free.y := SHORT(c.stack[c.tos]); DEC(c.tos);
	c.free.x := SHORT(c.stack[c.tos]); DEC(c.tos);
	INC(c.pc)
END SFVFS;

(* get projection vector *)
PROCEDURE GPV (VAR c: Context);
BEGIN
	INC(c.tos); c.stack[c.tos] := c.proj.x;
	INC(c.tos); c.stack[c.tos] := c.proj.y;
	INC(c.pc)
END GPV;

(* get freedom vector *)
PROCEDURE GFV (VAR c: Context);
BEGIN
	INC(c.tos); c.stack[c.tos] := c.free.x;
	INC(c.tos); c.stack[c.tos] := c.free.y;
	INC(c.pc)
END GFV;

(* set reference point i *)
PROCEDURE SRPi (VAR c: Context);
	VAR rp: INTEGER;
BEGIN
	rp := SHORT(c.stack[c.tos]); DEC(c.tos);
	CASE c.code[c.pc] OF
	| 10X: c.rp0 := rp
	| 11X: c.rp1 := rp
	| 12X: c.rp2 := rp
	END;
	INC(c.pc)
END SRPi;

(* set zone pointer i *)
PROCEDURE SZPi (VAR c: Context);
	VAR gep: INTEGER;
BEGIN
	gep := SHORT(c.stack[c.tos]); DEC(c.tos);
	CASE c.code[c.pc] OF
	| 13X: c.gep0 := gep; c.zp0 := c.zone[gep]
	| 14X: c.gep1 := gep; c.zp1 := c.zone[gep]
	| 15X: c.gep2 := gep; c.zp2 := c.zone[gep]
	END;
	INC(c.pc)
END SZPi;

(* set zone pointers *)
PROCEDURE SZPS (VAR c: Context);
BEGIN
	c.gep0 := SHORT(c.stack[c.tos]); DEC(c.tos); c.gep1 := c.gep0; c.gep2 := c.gep2;
	c.zp0 := c.zone[c.gep0]; c.zp1 := c.zp0; c.zp2 := c.zp0;
	INC(c.pc)
END SZPS;

(* round to half grid *)
PROCEDURE RTHG (VAR c: Context);
BEGIN
	c.period := 40H; c.phase := 20H; c.threshold := 20H; INC(c.pc)
END RTHG;

(* round to grid *)
PROCEDURE RTG (VAR c: Context);
BEGIN
	c.period := 40H; c.phase := 0; c.threshold := 20H; INC(c.pc)
END RTG;

(* round to double grid *)
PROCEDURE RTDG (VAR c: Context);
BEGIN
	c.period := 20H; c.phase := 0; c.threshold := 10H; INC(c.pc)
END RTDG;

(* round down to grid *)
PROCEDURE RDTG (VAR c: Context);
BEGIN
	c.period := 40H; c.phase := 0; c.threshold := 0; INC(c.pc)
END RDTG;

(* round up to grid *)
PROCEDURE RUTG (VAR c: Context);
BEGIN
	c.period := 40H; c.phase := 0; c.threshold := 3FH; INC(c.pc)
END RUTG;

(* round off *)
PROCEDURE ROFF (VAR c: Context);
BEGIN
	c.period := 1; c.phase := 0; c.threshold := 0; INC(c.pc)
END ROFF;

(* super round and super round 45 degrees *)
PROCEDURE SROUND (VAR c: Context);
	VAR gridPeriod: F26D6; code, cd: LONGINT;
BEGIN
	IF ODD(ORD(c.code[c.pc])) THEN								(* super round 45 degrees *)
		gridPeriod := 45											(* funnily enough, this is really 64*(1/sqrt(2)) *)
	ELSE
		gridPeriod := 64
	END;
	code := c.stack[c.tos]; DEC(c.tos);
	cd := ASH(code, -6) MOD 4;
	CASE cd OF
	| 0: c.period := gridPeriod DIV 2
	| 1: c.period := gridPeriod
	| 2: c.period := 2*gridPeriod
	END;
	cd := ASH(code, -4) MOD 2;
	c.phase := cd * c.period DIV 4;
	cd := code MOD 16;
	IF cd = 0 THEN
		c.threshold := c.period-1
	ELSE
		c.threshold := c.period * (cd-4) DIV 8
	END;
	INC(c.pc)
END SROUND;

(* set loop variable *)
PROCEDURE SLOOP (VAR c: Context);
BEGIN
	c.loop := SHORT(c.stack[c.tos]); DEC(c.tos); INC(c.pc);
	IF c.loop = 0 THEN												(* ERROR, stop execution *)
		c.pc := c.codeLen;
	END;
END SLOOP;

(* set minimum distance *)
PROCEDURE SMD (VAR c: Context);
BEGIN
	c.minDist := c.stack[c.tos]; DEC(c.tos); INC(c.pc)
END SMD;

(* instruction execution control *)
PROCEDURE INSTCTRL (VAR c: Context);
	VAR sel, val: LONGINT;
BEGIN
	sel := c.stack[c.tos]; DEC(c.tos);
	IF sel = 1 THEN c.inhibitFit := FALSE
	ELSIF sel = 2 THEN c.ignorePrep := FALSE
	END;
	val := c.stack[c.tos]; DEC(c.tos);
	IF val # 0 THEN val := sel END;
	IF val = 1 THEN c.inhibitFit := TRUE
	ELSIF val = 2 THEN c.ignorePrep := TRUE
	END;
	INC(c.pc)
END INSTCTRL;

(* scan conversion control *)
PROCEDURE SCANCTRL (VAR c: Context);
	VAR n, thold: LONGINT;
BEGIN
	n := c.stack[c.tos] MOD 10000H; DEC(c.tos);
	thold := n MOD 256;
	IF thold = 0FFH THEN
		c.fixDropouts := TRUE
	ELSIF thold = 0 THEN
		c.fixDropouts := FALSE
	ELSE
		(* should there be a default value in case no condition holds? FreeType doesn't have one *)
		thold := 40H * thold;
		IF ODD(n DIV 100H) & (PPEm(c) <= thold) THEN c.fixDropouts := TRUE END;
		IF ODD(n DIV 200H) & c.rotated THEN c.fixDropouts := TRUE END;
		IF ODD(n DIV 400H) & c.stretched THEN c.fixDropouts := TRUE END;
		IF ODD(n DIV 800H) & (PPEm(c) > thold) THEN c.fixDropouts := FALSE END;
		IF ODD(n DIV 1000H) & ~c.rotated THEN c.fixDropouts := FALSE END;
		IF ODD(n DIV 2000H) & ~c.stretched THEN c.fixDropouts := FALSE END
	END;
	INC(c.pc)
END SCANCTRL;

(* scan type *)
PROCEDURE SCANTYPE (VAR c: Context);
	VAR st: INTEGER;
BEGIN
	st := SHORT(c.stack[c.tos]); DEC(c.tos);
	IF st IN {3, 6, 7} THEN st := 2 END;
	IF (0 <= st) & (st <= 5) THEN
		c.scanType := st
	END;
	INC(c.pc)
END SCANTYPE;

(* set control value table cut in *)
PROCEDURE SCVTCI (VAR c: Context);
BEGIN
	c.cvtCutIn := c.stack[c.tos]; DEC(c.tos); INC(c.pc)
END SCVTCI;

(* set single width cut in *)
PROCEDURE SSWCI (VAR c: Context);
BEGIN
	c.swCutIn := c.stack[c.tos]; DEC(c.tos); INC(c.pc)
END SSWCI;

(* set single width *)
PROCEDURE SSW (VAR c: Context);
BEGIN
	(* FreeType says that the Windows engine seems to interpret this as a Fixed value (not FUnits as in Spec) *)
	c.swVal := ASH(c.stack[c.tos], -10); DEC(c.tos); INC(c.pc)
END SSW;

(* set the auto flip flag *)
PROCEDURE FLIPON (VAR c: Context);
BEGIN
	c.autoFlip := TRUE; INC(c.pc)
END FLIPON;

(* clear the auto flip flag *)
PROCEDURE FLIPOFF (VAR c: Context);
BEGIN
	c.autoFlip := FALSE; INC(c.pc)
END FLIPOFF;

(* set angle weight *)
PROCEDURE SANGW (VAR c: Context);
BEGIN
	DEC(c.tos); INC(c.pc)							(* corresponding instruction AA is obsolete *)
END SANGW;

(* set delta base *)
PROCEDURE SDB (VAR c: Context);
BEGIN
	c.deltaBase := SHORT(c.stack[c.tos]); DEC(c.tos); INC(c.pc)
END SDB;

(* set delta shift *)
PROCEDURE SDS (VAR c: Context);
BEGIN
	c.deltaShift := SHORT(c.stack[c.tos]); DEC(c.tos); INC(c.pc)
END SDS;


(*--- Reading and Writing Data ---*)

(* get coordinate projected onto the projection vector *)
PROCEDURE GC (VAR c: Context);
	VAR p: LONGINT; dist: F26D6;
BEGIN
	p := c.stack[c.tos];
	IF ODD(ORD(c.code[c.pc])) THEN								(* use original coordinates *)
		(* both TTI and FreeType use the dual projection vector with original coordinates *)
		dist := Project(c.zp2.pt[p].org, c.proj2)
	ELSE															(* use current coordinates *)
		dist := Project(c.zp2.pt[p].cur, c.proj)
	END;
	c.stack[c.tos] := dist;
	INC(c.pc)
END GC;

(* set coordinate from stack using projection and freedom vector *)
PROCEDURE SCFS (VAR c: Context);
	VAR dist, d: F26D6; p: LONGINT;
BEGIN
	dist := c.stack[c.tos]; DEC(c.tos);
	p := c.stack[c.tos]; DEC(c.tos);
	d := Project(c.zp2.pt[p].cur, c.proj);
	Move(c.zp2.pt[p], c.free, c.proj, dist - d);
	INC(c.pc)
END SCFS;

(* measure distance *)
PROCEDURE MD (VAR c: Context);
	VAR p1, p2: LONGINT; d1, d2: F26D6;
BEGIN
	(*
		- original implementation used zone 0 for p1 and zone 1 for p2
		- both TTI and FreeType swap opcode semantics (probably bug in spec since odd opcode comes first)
		- spec doesn't mention that dual projection vector has to be used with original coordinates
	*)
	p1 := c.stack[c.tos]; DEC(c.tos);
	p2 := c.stack[c.tos];
	IF ODD(ORD(c.code[c.pc])) THEN				(* use current coordinates *)
		d1 := Project(c.zp1.pt[p1].cur, c.proj);
		d2 := Project(c.zp0.pt[p2].cur, c.proj)
	ELSE											(* use original coordinates *)
		d1 := Project(c.zp1.pt[p1].org, c.proj2);
		d2 := Project(c.zp0.pt[p2].org, c.proj2)
	END;
	c.stack[c.tos] := d2 - d1;
	INC(c.pc)
END MD;

(* measure pixels per em *)
PROCEDURE MPPEM (VAR c: Context);
BEGIN
	INC(c.tos); c.stack[c.tos] := ASH(PPEm(c) + 20H, -6); INC(c.pc)
END MPPEM;

(* measure point size *)
PROCEDURE MPS (VAR c: Context);
BEGIN
	INC(c.tos); c.stack[c.tos] := ASH(c.ptsize + 20H, -6); INC(c.pc)
END MPS;


(*--- Managing Outlines ---*)

(* flip point *)
PROCEDURE FLIPPT (VAR c: Context);
	VAR p: LONGINT; pt: Points;
BEGIN
	(* both TTI and FreeType don't use zp0; instead they work in zone 1 directly *)
	pt := c.zone[1].pt;
	WHILE c.loop > 0 DO
		p := c.stack[c.tos]; DEC(c.tos);
		pt[p].onCurve := ~pt[p].onCurve;
		DEC(c.loop)
	END;
	c.loop := 1;
	INC(c.pc)
END FLIPPT;

(* flip range on/off *)
PROCEDURE FLIPRG (VAR c: Context);
	VAR on: BOOLEAN; hi, lo: LONGINT; pt: Points;
BEGIN
	on := ODD(ORD(c.code[c.pc]));
	hi := c.stack[c.tos]; DEC(c.tos);
	lo := c.stack[c.tos]; DEC(c.tos);
	pt := c.zone[1].pt;
	WHILE lo <= hi DO
		pt[lo].onCurve := on;
		INC(lo)
	END;
	INC(c.pc)
END FLIPRG;

(* shift point by the last point *)
PROCEDURE SHP (VAR c: Context);
	VAR zone: Zone; p: LONGINT; dx, dy: F26D6; pt: Points;
BEGIN
	GetRefDist(c, ODD(ORD(c.code[c.pc])), zone, p, dx, dy);
	pt := c.zp2.pt;
	WHILE c.loop > 0 DO
		p := c.stack[c.tos]; DEC(c.tos);
		IF c.free.x # 0 THEN
			INC(pt[p].cur[X], dx); pt[p].touched[X] := TRUE
		END;
		IF c.free.y # 0 THEN
			INC(pt[p].cur[Y], dy); pt[p].touched[Y] := TRUE
		END;
		DEC(c.loop)
	END;
	c.loop := 1;
	INC(c.pc)
END SHP;

(* shift contour by the last point *)
PROCEDURE SHC (VAR c: Context);
	VAR zone: Zone; ref, cont, cur, last: LONGINT; dx, dy: F26D6; pt: Points;
BEGIN
	(*
		- TTI uses original coordinates (which is probably wrong)
		- FreeType says that points aren't touched (so I don't)
	*)
	GetRefDist(c, ODD(ORD(c.code[c.pc])), zone, ref, dx, dy);
	pt := c.zp2.pt;
	cont := c.stack[c.tos]; DEC(c.tos);
	cur := c.zp2.first[cont]; last := c.zp2.first[cont+1]-1;
	WHILE cur <= last DO
		IF (zone # c.zp2) OR (cur # ref) THEN
			IF c.free.x # 0 THEN
				INC(pt[cur].cur[X], dx)
			END;
			IF c.free.y # 0 THEN
				INC(pt[cur].cur[Y], dy)
			END
		END;
		INC(cur)
	END;
	INC(c.pc)
END SHC;

(* shift zone by the last point *)
PROCEDURE SHZ (VAR c: Context);
	VAR zone, z: Zone; ref, cur, last: LONGINT; dx, dy: F26D6; pt: Points;
BEGIN
	(*
		- TTI uses original coordinates (which is probably wrong)
		- FreeType says that points aren't touched (so I don't)
		- FreeType ignores the argument on the stack and always uses zp2
	*)
	GetRefDist(c, ODD(ORD(c.code[c.pc])), zone, ref, dx, dy);
	z := c.zone[c.stack[c.tos]]; DEC(c.tos);
	pt := z.pt;
	cur := 0; last := z.first[z.contours]-1;
	WHILE cur <= last DO
		IF (zone # z) OR (cur # ref) THEN
			IF c.free.x # 0 THEN
				INC(pt[cur].cur[X], dx)
			END;
			IF c.free.y # 0 THEN
				INC(pt[cur].cur[Y], dy)
			END
		END;
		INC(cur)
	END;
	INC(c.pc)
END SHZ;

(* shift point by a pixel amount *)
PROCEDURE SHPIX (VAR c: Context);
	VAR dist, dx, dy: F26D6; pt: Points; p: LONGINT;
BEGIN
	dist := c.stack[c.tos]; DEC(c.tos);
	dx := MulShift(dist, c.free.x, -14);
	dy := MulShift(dist, c.free.y, -14);
	pt := c.zp2.pt;
	WHILE c.loop > 0 DO
		p := c.stack[c.tos]; DEC(c.tos);
		IF c.free.x # 0 THEN
			INC(pt[p].cur[X], dx); pt[p].touched[X] := TRUE
		END;
		IF c.free.y # 0 THEN
			INC(pt[p].cur[Y], dy); pt[p].touched[Y] := TRUE
		END;
		DEC(c.loop)
	END;
	c.loop := 1;
	INC(c.pc)
END SHPIX;

(* move stack indirect relative point *)
PROCEDURE MSIRP (VAR c: Context);
	VAR dist, d: F26D6; p: LONGINT; org: Coord; pt: Points;
BEGIN
	dist := c.stack[c.tos]; DEC(c.tos);
	p := c.stack[c.tos]; DEC(c.tos);

	(* undocumented behaviour, suggested by FreeType *)
	IF c.gep0 = 0 THEN
		org := c.zp0.pt[c.rp0].org;
		pt := c.zp1.pt; pt[p].org := org; pt[p].cur := org
	END;

	d := Project(c.zp1.pt[p].cur, c.proj) - Project(c.zp0.pt[c.rp0].cur, c.proj);
	Move(c.zp1.pt[p], c.free, c.proj, dist - d);
	c.rp1 := c.rp0; c.rp2 := SHORT(p);	(* TTI didn't implement this *)
	IF ODD(ORD(c.code[c.pc])) THEN
		c.rp0 := SHORT(p)
	END;
	INC(c.pc)
END MSIRP;

(* move direct absolute point *)
PROCEDURE MDAP (VAR c: Context);
	VAR p: LONGINT; d, dist: F26D6;
BEGIN
	p := c.stack[c.tos]; DEC(c.tos);
	IF ODD(ORD(c.code[c.pc])) THEN
		d := Project(c.zp0.pt[p].cur, c.proj);
		dist := Round(d, c.period, c.phase, c.threshold) - d
	ELSE
		dist := 0
	END;
	Move(c.zp0.pt[p], c.free, c.proj, dist);
	c.rp0 := SHORT(p); c.rp1 := SHORT(p);
	INC(c.pc)
END MDAP;

(* move indirect absolute point *)
PROCEDURE MIAP (VAR c: Context);
	VAR cvt, p: LONGINT; dist, d: F26D6; pt: Points; xy: Coord;
BEGIN
	cvt := c.stack[c.tos]; DEC(c.tos);
	p := c.stack[c.tos]; DEC(c.tos);
	dist := CVTValue(cvt, c);
	pt := c.zp0.pt;
	IF c.gep0 = 0 THEN											(* twilight zone *)
		(* why does FreeType use the freedom vector for this? The spec explicitly mentions the projection vector *)
		xy[X] := MulShift(dist, c.proj.x, -14); xy[Y] := MulShift(dist, c.proj.y, -14);
		pt[p].org := xy; pt[p].cur := xy
	END;
	d := Project(pt[p].cur, c.proj);
	IF c.autoFlip & (dist * d < 0) THEN dist := -dist END;			(* got this from TTI; FreeType does nothing similar *)
	IF ODD(ORD(c.code[c.pc])) THEN							(* round and apply cvt cutin *)
		IF ABS(dist - d) > c.cvtCutIn THEN dist := d END;
		dist := Round(dist, c.period, c.phase, c.threshold)
	END;
	Move(pt[p], c.free, c.proj, dist - d);
	c.rp0 := SHORT(p); c.rp1 := SHORT(p);
	INC(c.pc)
END MIAP;

(* move direct relative point *)
PROCEDURE MDRP (VAR c: Context);
	VAR p: LONGINT; d, dist: F26D6;
BEGIN
	p := c.stack[c.tos]; DEC(c.tos);
	d := Project(c.zp1.pt[p].org, c.proj2) - Project(c.zp0.pt[c.rp0].org, c.proj2);
	(* why does FreeType use the absolute value of 'd' for the single width cutin test? *)
	IF (d >= 0) & (ABS(d - c.swVal) < c.swCutIn) THEN d := c.swVal
	ELSIF (d < 0) & (ABS(-d - c.swVal) < c.swCutIn) THEN d := -c.swVal
	END;
	IF ODD(ORD(c.code[c.pc]) DIV 4) THEN									(* round distance *)
		dist := Round(d, c.period, c.phase, c.threshold)
	ELSE
		dist := d
	END;
	IF ODD(ORD(c.code[c.pc]) DIV 8) THEN									(* keep distance greater than minimum distance *)
		IF (d >= 0) & (dist < c.minDist) THEN dist := c.minDist
		ELSIF (d < 0) & (dist > -c.minDist) THEN dist := -c.minDist
		END
	END;
	d := Project(c.zp1.pt[p].cur, c.proj) - Project(c.zp0.pt[c.rp0].cur, c.proj);
	Move(c.zp1.pt[p], c.free, c.proj, dist - d);
	c.rp1 := c.rp0; c.rp2 := SHORT(p);
	IF ODD(ORD(c.code[c.pc]) DIV 16) THEN
		c.rp0 := SHORT(p)
	END;
	INC(c.pc)
END MDRP;

(* move indirect relative point *)
PROCEDURE MIRP (VAR c: Context);
	VAR cvt, p: LONGINT; dcvt, od, cd, dist: F26D6; pt: Points; xy: Coord;
BEGIN
	IF LEN(c.stack) <= c.tos THEN RETURN END;
	cvt := c.stack[c.tos]; DEC(c.tos);
	p := c.stack[c.tos]; DEC(c.tos);
	dcvt := CVTValue(cvt, c);
	pt := c.zp1.pt;
	IF c.gep1 = 0 THEN	(* according to FreeType, MIRP can be used to create twilight points *)
		xy[X] := c.zp0.pt[c.rp0].org[X] + MulShift(dcvt, c.free.x, -14);
		xy[Y] := c.zp0.pt[c.rp0].org[Y] + MulShift(dcvt, c.free.y, -14);
		pt[p].org := xy; pt[p].cur := xy
	END;
	od := Project(pt[p].org, c.proj2) - Project(c.zp0.pt[c.rp0].org, c.proj2);
	cd := Project(pt[p].cur, c.proj) - Project(c.zp0.pt[c.rp0].cur, c.proj);
	IF c.autoFlip & (od * dcvt < 0) THEN
		dcvt := -dcvt
	END;
	IF ODD(ORD(c.code[c.pc]) DIV 4) THEN							(* perform cvtCutIn test and round *)
		IF c.zp0 = c.zp1 THEN										(* according to FreeType, both points have to be in the same zone *)
			IF ABS(od - dcvt) >= c.cvtCutIn THEN
				dcvt := od
			END;
			(* for the single width cut in test, FreeType uses again the value of dcvt directly !? *)
			IF (dcvt >= 0) & (ABS(dcvt - c.swVal) < c.swCutIn) THEN dcvt := c.swVal
			ELSIF (dcvt < 0) & (ABS(-dcvt - c.swVal) < c.swCutIn) THEN dcvt := -c.swVal
			END
		END;
		dist := Round(dcvt, c.period, c.phase, c.threshold)
	ELSE
		dist := dcvt													(* TTI used the original distance, which is almost certainly wrong *)
	END;
	IF ODD(ORD(c.code[c.pc]) DIV 8) THEN							(* perform minimum distance test *)
		IF (od >= 0) & (dist < c.minDist) THEN dist := c.minDist
		ELSIF (od < 0) & (dist > -c.minDist) THEN dist := -c.minDist
		END
	END;
	Move(pt[p], c.free, c.proj, dist - cd);
	c.rp1 := c.rp0; c.rp2 := SHORT(p);
	IF ODD(ORD(c.code[c.pc]) DIV 16) THEN
		c.rp0 := SHORT(p)
	END;
	INC(c.pc)
END MIRP;

(* align relative point *)
PROCEDURE ALIGNRP (VAR c: Context);
	VAR p: LONGINT; dist: F26D6;
BEGIN
	WHILE c.loop > 0 DO
		p := c.stack[c.tos]; DEC(c.tos);
		dist := Project(c.zp1.pt[p].cur, c.proj) - Project(c.zp0.pt[c.rp0].cur, c.proj);
		Move(c.zp1.pt[p], c.free, c.proj, -dist);
		DEC(c.loop)
	END;
	c.loop := 1;
	INC(c.pc)
END ALIGNRP;

PROCEDURE DivHL( a,  b: HUGEINT ): LONGINT;
VAR q: HUGEINT; positive: BOOLEAN;
BEGIN
	positive := TRUE;
	IF a < 0 THEN  positive := ~positive;  a := -a  END;
	IF b < 0 THEN  positive := ~positive;  b := -b  END;	
	q := a DIV b;
	IF ~positive THEN  q := -q  END;	
	RETURN SHORT( q )
END DivHL;

(* move point to intersection of two lines *)
PROCEDURE ISECT (VAR c: Context);
	VAR
		b1, b0, a1, a0, p: LONGINT; pt: Points; 
		ax0, ay0, ax1, ay1, bx0, by0, bx1, by1: F26D6;
		dxa, dya, dxb, dyb, dx, dy, v, det: HUGEINT;
BEGIN
	b1 := c.stack[c.tos];  DEC(c.tos);
	b0 := c.stack[c.tos];  DEC(c.tos);
	a1 := c.stack[c.tos];  DEC(c.tos);
	a0 := c.stack[c.tos];  DEC(c.tos);
	p := c.stack[c.tos];  DEC(c.tos);
	pt := c.zp2.pt;
	pt[p].touched[X] := TRUE;  pt[p].touched[Y] := TRUE;
	ax0 := c.zp1.pt[a0].cur[X];  ay0 := c.zp1.pt[a0].cur[Y];
	ax1 := c.zp1.pt[a1].cur[X];  ay1 := c.zp1.pt[a1].cur[Y];
	bx0 := c.zp0.pt[b0].cur[X];  by0 := c.zp0.pt[b0].cur[Y];
	bx1 := c.zp0.pt[b1].cur[X];  by1 := c.zp0.pt[b1].cur[Y];
	
	dxa := ax1 - ax0;  dya := ay1 - ay0;
	dxb := bx1 - bx0;  dyb := by1 - by0;
	det := dya*dxb - dyb*dxa;
	
	IF ABS(det) >= 80H THEN
		dx := bx0 - ax0;  
		dy := by0 - ay0;
		dyb := -dyb;
		v := dx*dyb + dy*dxb;  
		pt[p].cur[X] := ax0 + DivHL( v*dxa, det ); 
		pt[p].cur[Y] := ay0 + DivHL( v*dya, det );
	ELSE	(* lines are (almost) parallel *)
		pt[p].cur[X] := (ax0 + ax1 + bx0 + bx1) DIV 4;
		pt[p].cur[Y] := (ay0 + ay1 + by0 + by1) DIV 4
	END;
	INC(c.pc)
END ISECT;

(* align points *)
PROCEDURE ALIGNPTS (VAR c: Context);
	VAR p1, p2: LONGINT; dist: F26D6;
BEGIN
	p1 := c.stack[c.tos]; DEC(c.tos);
	p2 := c.stack[c.tos]; DEC(c.tos);
	(* both TTI and FreeType swap use p1 with zp0 and p2 with zp1 (contrary to spec) *)
	dist := (Project(c.zp0.pt[p1].cur, c.proj) - Project(c.zp1.pt[p2].cur, c.proj)) DIV 2;
	Move(c.zp0.pt[p1], c.free, c.proj, -dist);
	Move(c.zp1.pt[p2], c.free, c.proj, dist);
	INC(c.pc)
END ALIGNPTS;

(* interpolate point by the last relative stretch *)
PROCEDURE IP (VAR c: Context);
	VAR od1, od2, cd1, cd2, od, cd, dist: F26D6; pt: Points; p: LONGINT;
BEGIN
	od1 := Project(c.zp0.pt[c.rp1].org, c.proj2);
	od2 := Project(c.zp1.pt[c.rp2].org, c.proj2);
	cd1 := Project(c.zp0.pt[c.rp1].cur, c.proj);
	cd2 := Project(c.zp1.pt[c.rp2].cur, c.proj);
	pt := c.zp2.pt;
	WHILE c.loop > 0 DO
		p := c.stack[c.tos]; DEC(c.tos);
		od := Project(pt[p].org, c.proj2);
		cd := Project(pt[p].cur, c.proj);
		IF (od1 <= od2) & (od <= od1) OR (od1 > od2) & (od >= od1) THEN
			dist := cd1 - od1 + od - cd
		ELSIF (od1 <= od2) & (od2 <= od) OR (od1 > od2) & (od2 >= od) THEN
			dist := cd2 - od2 + od - cd
		ELSE
			dist := MulDiv(cd2 - cd1, od - od1, od2 - od1) + cd1 - cd
		END;
		Move(pt[p], c.free, c.proj, dist);
		DEC(c.loop)
	END;
	c.loop := 1;
	INC(c.pc)
END IP;

(* untouch point *)
PROCEDURE UTP (VAR c: Context);
	VAR p: LONGINT;
BEGIN
	p := c.stack[c.tos]; DEC(c.tos);
	IF c.free.x # 0 THEN
		c.zp2.pt[p].touched[X] := FALSE
	END;
	IF c.free.y # 0 THEN
		c.zp2.pt[p].touched[Y] := FALSE
	END;
	INC(c.pc)
END UTP;

(* interpolate untouched points through the outline *)
PROCEDURE IUP (VAR c: Context);
	VAR
		z: Zone; pt: Points; n, xy, beg, nil, first, end, cur: LONGINT; dxy: F26D6;

	PROCEDURE interpol (p0, p1, rp0, rp1: LONGINT);
		VAR oxy0, cxy0, dxy0, oxy1, cxy1, dxy1, cxy: F26D6;
	BEGIN
		IF p0 <= p1 THEN
			oxy0 := pt[rp0].org[xy]; cxy0 := pt[rp0].cur[xy]; dxy0 := cxy0 - oxy0;
			oxy1 := pt[rp1].org[xy]; cxy1 := pt[rp1].cur[xy]; dxy1 := cxy1 - oxy1;
			IF oxy0 < oxy1 THEN
				WHILE p0 <= p1 DO
					cxy := pt[p0].org[xy];
					IF cxy <= oxy0 THEN INC(cxy, dxy0)
					ELSIF oxy1 <= cxy THEN INC(cxy, dxy1)
					ELSE cxy := cxy0 + MulDiv(cxy - oxy0, cxy1 - cxy0, oxy1 - oxy0)
					END;
					pt[p0].cur[xy] := cxy;
					INC(p0)
				END
			ELSIF oxy1 < oxy0 THEN
				WHILE p0 <= p1 DO
					cxy := pt[p0].org[xy];
					IF cxy <= oxy1 THEN INC(cxy, dxy1)
					ELSIF oxy0 <= cxy THEN INC(cxy, dxy0)
					ELSE cxy := cxy0 + MulDiv(cxy - oxy0, cxy1 - cxy0, oxy1 - oxy0)
					END;
					pt[p0].cur[xy] := cxy;
					INC(p0)
				END
			ELSE
				WHILE p0 <= p1 DO
					cxy := pt[p0].org[xy];
					IF cxy <= oxy0 THEN INC(cxy, dxy0)
					ELSE INC(cxy, dxy1)
					END;
					pt[p0].cur[xy] := cxy;
					INC(p0)
				END
			END
		END
	END interpol;

BEGIN
	z := c.zp2; pt := z.pt; n := 0;
	xy := ORD(c.code[c.pc]) MOD 2;
	WHILE n < z.contours DO
		beg := z.first[n]; nil := z.first[n+1];
		WHILE (beg < nil) & ~pt[beg].touched[xy] DO INC(beg) END;
		IF beg < nil THEN
			first := beg;
			REPEAT
				end := beg+1;
				WHILE (end < nil) & ~pt[end].touched[xy] DO INC(end) END;
				IF end < nil THEN
					interpol(beg+1, end-1, beg, end);
					beg := end+1;
					WHILE (beg < nil) & pt[beg].touched[xy] DO INC(beg) END;
					DEC(beg)
				END
			UNTIL end = nil;
			IF beg = first THEN	(* only one touched point in whole contour => FreeType applies shift here *)
				dxy := pt[beg].cur[xy] - pt[beg].org[xy];
				cur := z.first[n];
				WHILE cur < beg DO INC(pt[cur].cur[xy], dxy); INC(cur) END;
				cur := beg+1;
				WHILE cur < nil DO INC(pt[cur].cur[xy], dxy); INC(cur) END
			ELSE
				interpol(beg+1, nil-1, beg, first);
				IF first > z.first[n] THEN interpol(z.first[n], first-1, beg, first) END
			END
		END;
		INC(n)
	END;
	INC(c.pc)
END IUP;


(*--- Managing Exceptions ---*)

(* delta exception Pn *)
PROCEDURE DELTAP (VAR c: Context);
	VAR base, ppm, n, p, arg: LONGINT;
BEGIN
	base := c.deltaBase;
	IF c.code[c.pc] = 71X THEN INC(base, 16)							(* DELTAP2 *)
	ELSIF c.code[c.pc] = 72X THEN INC(base, 32)						(* DELTAP3 *)
	END;
	ppm := ASH(PPEm(c) + 20H, -6);
	n := c.stack[c.tos]; DEC(c.tos);
	WHILE n > 0 DO
		p := c.stack[c.tos]; DEC(c.tos);
		arg := c.stack[c.tos]; DEC(c.tos);
		IF (base + arg DIV 10H MOD 10H = ppm) & (0 <= p) & (p < LEN(c.zp0.pt^)) THEN
			arg := arg MOD 10H - 8;
			IF arg >= 0 THEN INC(arg) END;
			arg := 40H * arg DIV ASH(1, c.deltaShift);
			Move(c.zp0.pt[p], c.free, c.proj, arg)
		END;
		DEC(n)
	END;
	INC(c.pc)
END DELTAP;

(* delta exception Cn *)
PROCEDURE DELTAC (VAR c: Context);
	VAR base, ppm, n, cvt, arg: LONGINT;
BEGIN
	base := c.deltaBase;
	IF c.code[c.pc] = 74X THEN INC(base, 16)							(* DELTAC2 *)
	ELSIF c.code[c.pc] = 75X THEN INC(base, 32)						(* DELTAC3 *)
	END;
	ppm := ASH(PPEm(c) + 20H, -6);
	n := c.stack[c.tos]; DEC(c.tos);
	WHILE n > 0 DO
		cvt := c.stack[c.tos]; DEC(c.tos);
		arg := c.stack[c.tos]; DEC(c.tos);
		IF base + arg DIV 10H MOD 10H = ppm THEN
			arg := arg MOD 10H - 8;
			IF arg >= 0 THEN INC(arg) END;
			arg := 40H * arg DIV ASH(1, c.deltaShift);
			INC(c.cvt[cvt], ShiftDiv(arg, 16, Ratio(c)))
		END;
		DEC(n)
	END;
	INC(c.pc)
END DELTAC;


(*--- Managing the Stack ---*)

(* duplicate top stack element *)
PROCEDURE DUP (VAR c: Context);
BEGIN
	INC(c.tos); c.stack[c.tos] := c.stack[c.tos-1]; INC(c.pc)
END DUP;

(* pop top stack element *)
PROCEDURE POP (VAR c: Context);
BEGIN
	DEC(c.tos); INC(c.pc)
END POP;

(* clear the entire stack *)
PROCEDURE CLEAR (VAR c: Context);
BEGIN
	c.tos := -1; INC(c.pc)
END CLEAR;

(* swap the top two elements on the stack *)
PROCEDURE SWAP (VAR c: Context);
	VAR tmp: LONGINT;
BEGIN
	tmp := c.stack[c.tos]; c.stack[c.tos] := c.stack[c.tos-1]; c.stack[c.tos-1] := tmp; INC(c.pc)
END SWAP;

(* return depth of the stack *)
PROCEDURE DEPTH (VAR c: Context);
BEGIN
	INC(c.tos); c.stack[c.tos] := c.tos; INC(c.pc)
END DEPTH;

(* copy the indexed element to the top of the stack *)
PROCEDURE CINDEX (VAR c: Context);
	VAR idx: LONGINT;
BEGIN
	idx := c.stack[c.tos]; c.stack[c.tos] := c.stack[c.tos - idx]; INC(c.pc)
END CINDEX;

(* move the indexed element to the top of the stack *)
PROCEDURE MINDEX (VAR c: Context);
	VAR idx, pos, elem: LONGINT;
BEGIN
	idx := c.stack[c.tos];
	pos := c.tos - idx; elem := c.stack[pos];
	WHILE idx > 1 DO
		c.stack[pos] := c.stack[pos+1]; INC(pos); DEC(idx)
	END;
	c.stack[pos] := elem; DEC(c.tos);
	INC(c.pc)
END MINDEX;

(* roll the top three stack elements *)
PROCEDURE ROLL (VAR c: Context);
	VAR elem: LONGINT;
BEGIN
	elem := c.stack[c.tos-2]; c.stack[c.tos-2] := c.stack[c.tos-1]; c.stack[c.tos-1] := c.stack[c.tos]; c.stack[c.tos] := elem;
	INC(c.pc)
END ROLL;


(*--- Managing the Flow of Control ---*)

PROCEDURE Skip (VAR c: Context);
BEGIN
	CASE c.code[c.pc] OF
	| 40X: INC(c.pc, LONG(2 + ORD(c.code[c.pc+1])))						(* NPUSHB *)
	| 41X: INC(c.pc, LONG(2 + 2*ORD(c.code[c.pc+1])))						(* NPUSHW *)
	| 0B0X..0B7X: INC(c.pc, LONG(2 + ORD(c.code[c.pc]) MOD 8))			(* PUSHBx *)
	| 0B8X..0BFX: INC(c.pc, LONG(3 + 2*(ORD(c.code[c.pc]) MOD 8)))		(* PUSHWx *)
	| 58X: INC(c.pc); WHILE c.code[c.pc] # 59X DO Skip(c) END; INC(c.pc)		(* IF..EIF *)
	ELSE INC(c.pc)
	END
END Skip;

(* if test *)
PROCEDURE iF (VAR c: Context);
BEGIN
	IF c.stack[c.tos] = 0 THEN
		INC(c.pc);
		WHILE (c.code[c.pc] # 1BX) & (c.code[c.pc] # 59X) DO				(* terminated by ELSE or EIF *)
			Skip(c)
		END
	END;
	DEC(c.tos); INC(c.pc)
END iF;

(* else part of if-clause *)
PROCEDURE eLSE (VAR c: Context);
BEGIN
	(* only executed if previous IF-test was successful => skip until EIF *)
	REPEAT Skip(c) UNTIL c.code[c.pc] = 59X;
	INC(c.pc)
END eLSE;

(* end mark of if-clause *)
PROCEDURE EIF (VAR c: Context);
BEGIN
	INC(c.pc)
END EIF;

(* jump relative on true *)
PROCEDURE JROT (VAR c: Context);
	VAR true: BOOLEAN;
BEGIN
	true := c.stack[c.tos] # 0; DEC(c.tos);
	IF true THEN
		INC(c.pc, c.stack[c.tos]);
	ELSE
		INC(c.pc)
	END;
	DEC(c.tos)
END JROT;

(* jump relative *)
PROCEDURE JUMPR (VAR c: Context);
BEGIN
	INC(c.pc, c.stack[c.tos]); DEC(c.tos)
END JUMPR;

(* jump relative on false *)
PROCEDURE JROF (VAR c: Context);
	VAR false: BOOLEAN;
BEGIN
	false := c.stack[c.tos] = 0; DEC(c.tos);
	IF false THEN
		INC(c.pc, c.stack[c.tos]);
	ELSE
		INC(c.pc)
	END;
	DEC(c.tos)
END JROF;


(*--- Logical Functions ---*)

(* comparison *)
PROCEDURE COMPARE (VAR c: Context);
	VAR b, a: LONGINT; res: BOOLEAN;
BEGIN
	b := c.stack[c.tos]; DEC(c.tos); a := c.stack[c.tos];
	CASE c.code[c.pc] OF
	| 50X: res := a < b
	| 51X: res := a <= b
	| 52X: res := a > b
	| 53X: res := a >= b
	| 54X: res := a = b
	| 55X: res := a # b
	END;
	IF res THEN c.stack[c.tos] := 1
	ELSE c.stack[c.tos] := 0
	END;
	INC(c.pc)
END COMPARE;

(* odd *)
PROCEDURE oDD (VAR c: Context);
	VAR r: LONGINT;
BEGIN
	r := Round(c.stack[c.tos], c.period, c.phase, c.threshold) DIV 40H;
	IF ODD(r) THEN c.stack[c.tos] := 1 ELSE c.stack[c.tos] := 0 END;
	INC(c.pc)
END oDD;

(* even *)
PROCEDURE EVEN (VAR c: Context);
	VAR r: LONGINT;
BEGIN
	r := Round(c.stack[c.tos], c.period, c.phase, c.threshold) DIV 40H;
	IF ODD(r) THEN c.stack[c.tos] := 0 ELSE c.stack[c.tos] := 1 END;
	INC(c.pc)
END EVEN;

(* logical and *)
PROCEDURE AND (VAR c: Context);
	VAR b, a: LONGINT;
BEGIN
	b := c.stack[c.tos]; DEC(c.tos); a := c.stack[c.tos];
	IF a * b # 0 THEN c.stack[c.tos] := 1 ELSE c.stack[c.tos] := 0 END;
	INC(c.pc)
END AND;

(* logical or *)
PROCEDURE oR (VAR c: Context);
	VAR b, a: LONGINT;
BEGIN
	b := c.stack[c.tos]; DEC(c.tos); a := c.stack[c.tos];
	IF (a # 0) OR (b # 0) THEN c.stack[c.tos] := 1 ELSE c.stack[c.tos] := 0 END;
	INC(c.pc)
END oR;

(* logical not *)
PROCEDURE NOT (VAR c: Context);
BEGIN
	IF c.stack[c.tos] = 0 THEN c.stack[c.tos] := 1 ELSE c.stack[c.tos] := 0 END;
	INC(c.pc)
END NOT;


(*--- Arithmetic and Math Instructions ---*)

PROCEDURE ADD (VAR c: Context);
	VAR b: F26D6;
BEGIN
	b := c.stack[c.tos]; DEC(c.tos); INC(c.stack[c.tos], b); INC(c.pc)
END ADD;

PROCEDURE SUB (VAR c: Context);
	VAR b: F26D6;
BEGIN
	b := c.stack[c.tos]; DEC(c.tos); DEC(c.stack[c.tos], b); INC(c.pc)
END SUB;

PROCEDURE dIV (VAR c: Context);
	VAR b, a: F26D6;
BEGIN
	b := c.stack[c.tos]; DEC(c.tos); a := c.stack[c.tos];
	IF b > 0 THEN c.stack[c.tos] := ShiftDiv(a, 6, b)
	ELSIF b < 0 THEN c.stack[c.tos] := ShiftDiv(-a, 6, -b)
	ELSE c.stack[c.tos] := 0	(* division by zero *)
	END;
	INC(c.pc)
END dIV;

PROCEDURE MUL (VAR c: Context);
	VAR b, a: F26D6;
BEGIN
	b := c.stack[c.tos]; DEC(c.tos); a := c.stack[c.tos];
	c.stack[c.tos] := MulShift(a, b, -6);
	INC(c.pc)
END MUL;

PROCEDURE aBS (VAR c: Context);
BEGIN
	c.stack[c.tos] := ABS(c.stack[c.tos]); INC(c.pc)
END aBS;

PROCEDURE NEG (VAR c: Context);
BEGIN
	c.stack[c.tos] := -c.stack[c.tos]; INC(c.pc)
END NEG;

PROCEDURE Floor (VAR c: Context);
	VAR x: F26D6;
BEGIN
	x := c.stack[c.tos];
	c.stack[c.tos] := x - x MOD 40H;
	INC(c.pc)
END Floor;

PROCEDURE CEILING (VAR c: Context);
	VAR x: F26D6;
BEGIN
	x := c.stack[c.tos] + 3FH;
	c.stack[c.tos] := x - x MOD 40H;
	INC(c.pc)
END CEILING;

PROCEDURE mAX (VAR c: Context);
	VAR b, a: F26D6;
BEGIN
	b := c.stack[c.tos]; DEC(c.tos); a := c.stack[c.tos];
	IF a < b THEN c.stack[c.tos] := b END;
	INC(c.pc)
END mAX;

PROCEDURE mIN (VAR c: Context);
	VAR b, a: F26D6;
BEGIN
	b := c.stack[c.tos]; DEC(c.tos); a := c.stack[c.tos];
	IF a > b THEN c.stack[c.tos] := b END;
	INC(c.pc)
END mIN;


(*--- Compensating for the Engine Characteristics ---*)

(* round value *)
PROCEDURE ROUND (VAR c: Context);
BEGIN
	(* no engine characteristics are implemented *)
	c.stack[c.tos] := Round(c.stack[c.tos], c.period, c.phase, c.threshold);
	INC(c.pc)
END ROUND;

(* compensate without rounding value *)
PROCEDURE NROUND (VAR c: Context);
BEGIN
	INC(c.pc)	(* nothing happens *)
END NROUND;


(*--- Defining and Using Functions and Instructions ---*)

(* function definition *)
PROCEDURE FDEF (VAR c: Context);
	VAR n: LONGINT;
BEGIN
	n := c.stack[c.tos]; DEC(c.tos);
	c.func[n].code := c.code; c.func[n].len := c.codeLen; c.func[n].pc := c.pc;
	REPEAT Skip(c) UNTIL c.code[c.pc] = 2DX;								(* skip until ENDF *)
	INC(c.pc)
END FDEF;

(* end function definition *)
PROCEDURE ENDF (VAR c: Context);
BEGIN
	DEC(c.callStack[c.ctos].count);
	IF c.callStack[c.ctos].count < 0 THEN c.pc := c.codeLen; RETURN END;		(* ERROR, prevent stack trap *)
	IF c.callStack[c.ctos].count = 0 THEN
		c.code := c.callStack[c.ctos].ret.code; c.codeLen := c.callStack[c.ctos].ret.len; c.pc := c.callStack[c.ctos].ret.pc;
		DEC(c.ctos)
	ELSE
		c.pc := c.callStack[c.ctos].start										(* code remains the same *)
	END;
	INC(c.pc)																(* make PC point to instruction after FDEF/IDEF/(LOOP)CALL *)
END ENDF;

(* call function *)
PROCEDURE CALL (VAR c: Context);
	VAR n: LONGINT;
BEGIN
	n := c.stack[c.tos]; DEC(c.tos);
	INC(c.ctos);
	c.callStack[c.ctos].ret.code := c.code; c.callStack[c.ctos].ret.len := c.codeLen;
	c.callStack[c.ctos].ret.pc := c.pc; c.callStack[c.ctos].count := 1;
	c.code := c.func[n].code; c.codeLen := c.func[n].len; c.pc := c.func[n].pc+1	(* make PC point to first instruction after FDEF *)
END CALL;

(* loop and call function *)
PROCEDURE LOOPCALL (VAR c: Context);
	VAR n, count: LONGINT;
BEGIN
	n := c.stack[c.tos]; DEC(c.tos);
	count := c.stack[c.tos]; DEC(c.tos);
	INC(c.ctos);
	c.callStack[c.ctos].ret.code := c.code; c.callStack[c.ctos].ret.len := c.codeLen; c.callStack[c.ctos].ret.pc := c.pc;
	c.callStack[c.ctos].count := SHORT(count); c.callStack[c.ctos].start := c.func[n].pc;
	c.code := c.func[n].code; c.codeLen := c.func[n].len; c.pc := c.func[n].pc+1	(* make PC point to first instruction after FDEF *)
END LOOPCALL;

(* instruction definition *)
PROCEDURE IDEF (VAR c: Context);
	VAR op: CHAR; i: LONGINT;
BEGIN
	op := CHR(c.stack[c.tos]); DEC(c.tos);
	i := 0; WHILE (c.instr[i].beg.code # NIL) & (c.instr[i].opcode # op) DO INC(i) END;
	IF c.instr[i].beg.code = NIL THEN
		c.instr[i].opcode := op; c.instr[i].beg.code := c.code; c.instr[i].beg.len := c.codeLen; c.instr[i].beg.pc := c.pc
	END;
	REPEAT Skip(c) UNTIL c.code[c.pc] = 2DX;								(* skip until ENDF *)
	INC(c.pc)
END IDEF;

(* user defined instructions *)
PROCEDURE UNDEF (VAR c: Context);
	VAR i: LONGINT;
BEGIN
	i := 0; WHILE (c.instr[i].beg.code # NIL) & (c.instr[i].opcode # c.code[c.pc]) DO INC(i) END;
	IF c.instr[i].beg.code # NIL THEN											(* found instruction *)
		INC(c.ctos);
		c.callStack[c.ctos].ret.code := c.code; c.callStack[c.ctos].ret.len := c.codeLen;
		c.callStack[c.ctos].ret.pc := c.pc; c.callStack[c.ctos].count := 1;
		c.code := c.instr[i].beg.code; c.pc := c.instr[i].beg.pc
	END;
	INC(c.pc)
END UNDEF;


(*--- Miscellaneous Instructions ---*)

(* debug call *)
PROCEDURE DEBUG (VAR c: Context);
BEGIN
	DEC(c.tos); INC(c.pc);													(* pop the value off the stack *)
	IF Notify # NIL THEN Notify(c, NotifyData) END
END DEBUG;

(* get information *)
PROCEDURE GETINFO (VAR c: Context);
	VAR sel, val: LONGINT;
BEGIN
	sel := c.stack[c.tos]; val := 0;
	IF ODD(sel) THEN END;	(* give back version number 0 *)
	IF ODD(sel DIV 2) & c.rotated THEN INC(val, 100H) END;	(* glyph rotation status *)
	IF ODD(sel DIV 4) & c.stretched THEN INC(val, 200H) END;	(* glyph scale status *)
	c.stack[c.tos] := val;
	INC(c.pc)
END GETINFO;


(*--- Initialization ---*)

PROCEDURE InitBuiltins;
	VAR i: LONGINT;
BEGIN
	FOR i := 0 TO 0FFH DO Builtin[i] := UNDEF END;

	(* pushing data onto the interpreter stack *)
	Builtin[40H] := NPUSHB; Builtin[41H] := NPUSHW;
	FOR i := 0B0H TO 0B7H DO Builtin[i] := PUSHB END;
	FOR i := 0B8H TO 0BFH DO Builtin[i] := PUSHW END;

	(* managing the storage area *)
	Builtin[43H] := RS; Builtin[42H] := WS;

	(* managing the control value table *)
	Builtin[44H] := WCVT; Builtin[70H] := WCVT; Builtin[45H] := RCVT;

	(* managing the graphics state *)
	Builtin[0] := SVTCA; Builtin[1] := SVTCA;
	Builtin[2] := SPVTCA; Builtin[3] := SPVTCA;
	Builtin[4] := SFVTCA; Builtin[5] := SFVTCA;
	Builtin[6] := SPVTL; Builtin[7] := SPVTL;
	Builtin[8] := SFVTL; Builtin[9] := SFVTL;
	Builtin[0EH] := SFVTPV;
	Builtin[86H] := SDPVTL; Builtin[87H] := SDPVTL;
	Builtin[0AH] := SPVFS; Builtin[0BH] := SFVFS;
	Builtin[0CH] := GPV; Builtin[0DH] := GFV;

	Builtin[10H] := SRPi; Builtin[11H] := SRPi; Builtin[12H] := SRPi;
	Builtin[13H] := SZPi; Builtin[14H] := SZPi; Builtin[15H] := SZPi; Builtin[16H] := SZPS;

	Builtin[19H] := RTHG; Builtin[18H] := RTG; Builtin[3DH] := RTDG; Builtin[7DH] := RDTG; Builtin[7CH] := RUTG;
	Builtin[7AH] := ROFF; Builtin[76H] := SROUND; Builtin[77H] := SROUND;

	Builtin[17H] := SLOOP; Builtin[1AH] := SMD; Builtin[8EH] := INSTCTRL;
	Builtin[85H] := SCANCTRL; Builtin[8DH] := SCANTYPE;
	Builtin[1DH] := SCVTCI; Builtin[1EH] := SSWCI; Builtin[1FH] := SSW;
	Builtin[4DH] := FLIPON; Builtin[4EH] := FLIPOFF;
	Builtin[7EH] := SANGW; Builtin[5EH] := SDB; Builtin[5FH] := SDS;

	(* reading and writing data *)
	Builtin[46H] := GC; Builtin[47H] := GC; Builtin[48H] := SCFS; Builtin[49H] := MD; Builtin[4AH] := MD;
	Builtin[4BH] := MPPEM; Builtin[4CH] := MPS;

	(* managing outlines *)
	Builtin[80H] := FLIPPT; Builtin[81H] := FLIPRG; Builtin[82H] := FLIPRG;
	Builtin[32H] := SHP; Builtin[33H] := SHP; Builtin[34H] := SHC; Builtin[35H] := SHC;
	Builtin[36H] := SHZ; Builtin[37H] := SHZ; Builtin[38H] := SHPIX;
	Builtin[3AH] := MSIRP; Builtin[3BH] := MSIRP; Builtin[2EH] := MDAP; Builtin[2FH] := MDAP;
	Builtin[3EH] := MIAP; Builtin[3FH] := MIAP;
	FOR i := 0C0H TO 0DFH DO Builtin[i] := MDRP END;
	FOR i := 0E0H TO 0FFH DO Builtin[i] := MIRP END;
	Builtin[3CH] := ALIGNRP; Builtin[0FH] := ISECT; Builtin[27H] := ALIGNPTS;
	Builtin[39H] := IP; Builtin[29H] := UTP; Builtin[30H] := IUP; Builtin[31H] := IUP;

	(* managing exceptions *)
	Builtin[5DH] := DELTAP; Builtin[71H] := DELTAP; Builtin[72H] := DELTAP;
	Builtin[73H] := DELTAC; Builtin[74H] := DELTAC; Builtin[75H] := DELTAC;

	(* managing the stack *)
	Builtin[20H] := DUP; Builtin[21H] := POP; Builtin[22H] := CLEAR; Builtin[23H] := SWAP;
	Builtin[24H] := DEPTH; Builtin[25H] := CINDEX; Builtin[26H] := MINDEX; Builtin[8AH] := ROLL;

	(* managing the flow of control *)
	Builtin[58H] := iF; Builtin[1BH] := eLSE; Builtin[59H] := EIF;
	Builtin[78H] := JROT; Builtin[1CH] := JUMPR; Builtin[79H] := JROF;

	(* logical functions *)
	Builtin[50H] := COMPARE; Builtin[51H] := COMPARE; Builtin[52H] := COMPARE;
	Builtin[53H] := COMPARE; Builtin[54H] := COMPARE; Builtin[55H] := COMPARE;
	Builtin[56H] := oDD; Builtin[57H] := EVEN;
	Builtin[5AH] := AND; Builtin[5BH] := oR; Builtin[5CH] := NOT;

	(* arithmetic and math instructions *)
	Builtin[60H] := ADD; Builtin[61H] := SUB; Builtin[62H] := dIV; Builtin[63H] := MUL;
	Builtin[64H] := aBS; Builtin[65H] := NEG; Builtin[66H] := Floor; Builtin[67H] := CEILING;
	Builtin[8BH] := mAX; Builtin[8CH] := mIN;

	(* compensating for the engine characteristics *)
	FOR i := 68H TO 6BH DO Builtin[i] := ROUND END;
	FOR i := 6CH TO 6FH DO Builtin[i] := NROUND END;

	(* defining and using functions and instructions *)
	Builtin[2CH] := FDEF; Builtin[2DH] := ENDF; Builtin[2BH] := CALL; Builtin[2AH] := LOOPCALL; Builtin[89H] := IDEF;

	(* miscellaneous instructions *)
	Builtin[4FH] := DEBUG; Builtin[88H] := GETINFO
END InitBuiltins;


(*--- Exported Interface ---*)

(** allocation procedures for all dynamically sized memory structures **)
PROCEDURE NewCode* (VAR code: Code; size: LONGINT);
BEGIN
	IF size > 0 THEN NEW(code, size) ELSE code := NIL END
END NewCode;

PROCEDURE NewFunctions* (VAR func: Functions; size: LONGINT);
BEGIN
	IF size > 0 THEN NEW(func, size) ELSE func := NIL END
END NewFunctions;

PROCEDURE NewInstructions* (VAR instr: Instructions; size: LONGINT);
BEGIN
	IF size > 0 THEN NEW(instr, size) ELSE instr := NIL END
END NewInstructions;

PROCEDURE NewStore* (VAR store: Store; size: LONGINT);
BEGIN
	IF size > 0 THEN NEW(store, size) ELSE store := NIL END
END NewStore;

PROCEDURE NewCVT* (VAR cvt: CVT; size: LONGINT);
BEGIN
	IF size > 0 THEN NEW(cvt, size) ELSE cvt := NIL END
END NewCVT;

PROCEDURE NewZone* (VAR zone: Zone; contours, points: INTEGER);
BEGIN {EXCLUSIVE}
	NEW(zone); zone.contours := contours;
	NEW(zone.first, contours+1);
	IF points > 0 THEN NEW(zone.pt, points) ELSE zone.pt := NIL END;
	zone.first[contours] := points
END NewZone;

(** set context stacks **)
PROCEDURE SetStacks* (VAR c: Context; stack: Stack; callStack: CallStack);
BEGIN
	c.stack := stack; c.callStack := callStack
END SetStacks;

(** set context structures **)
PROCEDURE SetStructures* (VAR c: Context; func: Functions; instr: Instructions; store: Store; cvt: CVT);
BEGIN
	c.func := func; c.instr := instr; c.store := store; c.cvt := cvt
END SetStructures;

(** set instance specific context parameters **)
PROCEDURE SetResolution* (VAR c: Context; ptsize, xppm, yppm: F26D6; upm: INTEGER; rotated, stretched: BOOLEAN);
BEGIN
	c.ptsize := ptsize; c.xppm := xppm; c.yppm := yppm;
	IF xppm >= yppm THEN
		c.ppm := xppm; c.xratio := 10000H; c.yratio := ShiftDiv(yppm, 10H, xppm)
	ELSE
		c.ppm := yppm; c.xratio := ShiftDiv(xppm, 10H, yppm); c.yratio := 10000H
	END;
	c.upm := upm; c.rotated := rotated; c.stretched := stretched
END SetResolution;

(** initialize graphic state default values **)
PROCEDURE InitState* (VAR c: Context);
BEGIN
	c.cvtCutIn := 40H * 17 DIV 16;
	c.swCutIn := 0; c.swVal := 0;
	c.minDist := 40H;
	c.deltaBase := 9; c.deltaShift := 3;
	c.autoFlip := TRUE;
	c.inhibitFit := FALSE; c.ignorePrep := FALSE;
	c.fixDropouts := FALSE
END InitState;

(** save static part of graphic state (e.g. after executing CVT program) **)
PROCEDURE SaveState* (VAR c: Context; VAR s: State);
BEGIN
	s.cvtCutIn := c.cvtCutIn;
	s.swCutIn := c.swCutIn; s.swVal := c.swVal;
	s.minDist := c.minDist;
	s.deltaBase := c.deltaBase; s.deltaShift := c.deltaShift;
	s.autoFlip := c.autoFlip;
	s.inhibitFit := c.inhibitFit; s.ignorePrep := c.ignorePrep;
	s.fixDropouts := c.fixDropouts; s.scanType := c.scanType
END SaveState;

(** restore static part of graphic state (e.g. before executing a glyph program) **)
PROCEDURE RestoreState* (VAR c: Context; VAR s: State);
BEGIN
	c.cvtCutIn := s.cvtCutIn;
	c.swCutIn := s.swCutIn; c.swVal := s.swVal;
	c.minDist := s.minDist;
	c.deltaBase := s.deltaBase; c.deltaShift := s.deltaShift;
	c.autoFlip := s.autoFlip;
	c.inhibitFit := s.inhibitFit; c.ignorePrep := s.ignorePrep;
	c.fixDropouts := s.fixDropouts; c.scanType := s.scanType
END RestoreState;

(** execute program **)
PROCEDURE Execute* (VAR c: Context; code: Code; len: LONGINT; z0, z1: Zone);
BEGIN
	c.code := code; c.codeLen := len; c.pc := 0; c.tos := -1; c.ctos := -1;
	c.zone[0] := z0; c.zone[1] := z1;
	c.free.x := 4000H; c.free.y := 0;
	c.proj := c.free; c.proj2 := c.free;
	c.gep0 := 1; c.gep1 := 1; c.gep2 := 1;
	c.zp0 := c.zone[c.gep0]; c.zp1 := c.zone[c.gep1]; c.zp2 := c.zone[c.gep2];
	c.rp0 := 0; c.rp1 := 0; c.rp2 := 0;
	c.period := 40H; c.phase := 0; c.threshold := 20H;
	c.loop := 1;
	c.ratio := 0;
	IF Notify # NIL THEN Notify(c, NotifyData) END;
	WHILE c.pc < c.codeLen DO
		Builtin[ORD(c.code[c.pc])](c)									(* call primitive for current instruction *)
	END;
	IF Notify # NIL THEN Notify(c, NotifyData) END
END Execute;

(** install notify procedure for debug events **)
PROCEDURE InstallNotifier* (notify: Notifier; data: NotifierData);
BEGIN
	Notify := notify; NotifyData := data
END InstallNotifier;


BEGIN
	InitBuiltins;
	NewZone(EmptyZone, 0, 0);
	Notify := NIL; NotifyData := NIL
END OpenTypeInt.