-- File CIFRamtekScan.mesa
-- Written by Martin Newell, June 1980
-- Last updated: September 29, 1981  10:28 AM by Pasco

DIRECTORY

CIFDevicesDefs: FROM "CIFDevicesDefs" USING [MaxLENGTHLayerArray,
	LENGTHLayerArray],
CIFRamtekScanDefs: FROM "CIFRamtekScanDefs",
CIFRamtekTypeDefs: FROM "CIFRamtekTypeDefs" USING [Edge, EdgeRecord,
	EdgeAngle, EdgeType],
CIFRamtekUtilsDefs: FROM "CIFRamtekUtilsDefs" USING[ VersatecMakeEdge, FreeEdge, EdgeLessThan, XatY, HorColorLine, DrawTrap],
IODefs: FROM "IODefs" USING [SP, CR, WriteString, WriteLine, WriteOctal,
	WriteChar, WriteDecimal],
Real: FROM "Real" USING [WriteReal];

CIFRamtekScan: PROGRAM
IMPORTS CIFDevicesDefs, CIFRamtekUtilsDefs, IODefs, Real
EXPORTS CIFRamtekScanDefs  =

BEGIN OPEN CIFDevicesDefs, CIFRamtekTypeDefs, CIFRamtekUtilsDefs, IODefs, Real;

InitRamtekScan: PUBLIC PROCEDURE =
	BEGIN
--Initialize EdgeList and ActiveList
	EdgeList _ EdgeListEl _ ActiveList _ ALL[NIL];
	YNext _ YCurr _ YPrev _ ALL[0]; --i.e.not set
	END;

RamtekScanConvert: PUBLIC PROCEDURE [upto: REAL, forceOutput: BOOLEAN] =
-- Run the scan converter up to y=upto
-- forceOutput forces output up to and including upto
	BEGIN
	edge,prevedge: Edge;
	edgetype: EdgeType;
	newActiveList,pendingFreeEdges,nextedge: Edge;
	ptrnewActiveList: POINTER TO Edge;
	i,layer: CARDINAL;
	segleft,trapleft: Edge;
	adepth,edepth: INTEGER;
	StartSegment: PROCEDURE[e: Edge] = BEGIN segleft _ e; END;
	EndSegment: PROCEDURE[e: Edge] =
		BEGIN
		HorColorLine[XatY[segleft,YCurr[layer]], XatY[e,YCurr[layer]], YCurr[layer], layer];
		END;
	StartTrap: PROCEDURE[e: Edge] =
		BEGIN
		trapleft _ e;
		END;
	EndTrap: PROCEDURE[right: Edge] =
		BEGIN
		left: Edge _ trapleft;
		IF left.mate#right THEN
			BEGIN --pairing changed or NIL
			OutTrap[left,YPrev[layer]];
			OutTrap[right,YPrev[layer]];
			left.mate _ right;
			right.mate _ left;
			END;
		IF left.flagout OR right.flagout OR forceOutput THEN
			BEGIN
			OutTrap[left,YCurr[layer]];
			left.flagout _ right.flagout _ FALSE; --mustn't do this in OutTrap because of other calls to it
			END;
		END;
	OutTrap: PROCEDURE[e1: Edge, ytop: REAL] =
		BEGIN
		e2: Edge _ e1.mate;
		IF e2#NIL THEN
			BEGIN
			DrawTrap[e1,e1.lastouty,e2,ytop,layer];
			e1.lastouty _ e2.lastouty _ ytop;
			e1.mate _ e2.mate _ NIL;
			END;
		END;
	UpdateYNextNewALAndprevedge: PROCEDURE[edge: Edge] =
	--Update YNext, newActiveList, and prevedge
		BEGIN
	--YNext:
		YNext[layer] _
			CheckIntersection[prevedge,edge,YCurr[layer],MIN[YNext[layer],edge.yend]];
	--newActiveList:
		edge.next _ NIL;
		ptrnewActiveList^ _ edge;
		ptrnewActiveList _ @edge.next;
	--and prevedge:
		prevedge _ edge;
		END;
	QueueForFreeEdge: PROCEDURE[edge: Edge] =
		BEGIN
		edge.next _ pendingFreeEdges;
		pendingFreeEdges _ edge;
		END;
	FOR layer IN [0..LENGTHLayerArray) DO
	UNTIL (forceOutput AND YPrev[layer]>=upto) OR
			(~forceOutput AND YNext[layer]>=upto) OR
			(ActiveList[layer]=NIL AND EdgeList[layer]=NIL)
		DO
--in one pass through each ActiveList:
--	output trapezoids in previous swath
--	remove terminating edges from previous swath,
--	introduce newly entering ones,
--	drawing capping lines as necessary,
--	and find lowest upper y in YNext
		adepth _ edepth _ 0;
		[edge,edgetype] _ GetEdge[layer];
		prevedge _ NIL;
		YNext[layer] _ upto;
		pendingFreeEdges _ NIL;
		newActiveList _ EdgeListQueue _ NIL;
		ptrnewActiveList _ @newActiveList;
		IF YCurr[layer]=YPrev[layer] THEN
			BEGIN --scan only to find YNext[layer]  (and therefore to do intersections)
			UNTIL edge=NIL DO
				SELECT edgetype FROM
				aterminatingUp,aterminatingDown => QueueForFreeEdge[edge];
				acontinuingUp,acontinuingDown,estartingUp,estartingDown =>
					UpdateYNextNewALAndprevedge[edge];
				ENDCASE;
				[edge,edgetype] _ GetEdge[layer];
			ENDLOOP;
			END
		ELSE
			BEGIN --normal case
			UNTIL edge=NIL DO
				SELECT edgetype FROM
				aterminatingUp =>
					BEGIN
					IF adepth=0 THEN
						BEGIN
						edge.flagout _ TRUE;
						StartTrap[edge];
						IF edepth#0
						THEN EndSegment[edge]
						ELSE StartSegment[edge];
						END;
					adepth _ adepth+1;
					QueueForFreeEdge[edge];
					END;
				aterminatingDown =>
					BEGIN
					adepth _ adepth-1;
					IF adepth=0 THEN
						BEGIN
						edge.flagout _ TRUE;
						EndTrap[edge];
						IF edepth=0
						THEN EndSegment[edge]
						ELSE StartSegment[edge];
						END;
					QueueForFreeEdge[edge];
					END;
				acontinuingUp =>
					BEGIN
					UpdateYNextNewALAndprevedge[edge]; --must do this first incase intersection set .flagout
					IF adepth=0 THEN
						BEGIN
						IF edepth#0 THEN
							BEGIN
							edge.flagout _ TRUE;
							EndSegment[edge];
							END;
						StartTrap[edge];
						END
					ELSE
						BEGIN
						IF edepth=0 THEN
							BEGIN
							edge.lastouty _ YCurr[layer];
							EndSegment[edge];
							END;
						END;
					adepth _ adepth+1;
					edepth _ edepth+1;
					END;
				acontinuingDown =>
					BEGIN
					UpdateYNextNewALAndprevedge[edge];
					adepth _ adepth-1;
					edepth _ edepth-1;
					IF adepth=0 THEN
						BEGIN
						IF edepth#0 THEN
							BEGIN
							edge.flagout _ TRUE;
							StartSegment[edge];
							END;
						EndTrap[edge];
						END
					ELSE
						BEGIN
						IF edepth=0 THEN
							BEGIN
							edge.lastouty _ YCurr[layer];
							StartSegment[edge];
							END;
						END;
					END;
				estartingUp =>
					BEGIN
					UpdateYNextNewALAndprevedge[edge];
					IF edepth=0 THEN
						IF adepth#0
						THEN EndSegment[edge]
						ELSE StartSegment[edge];
					edepth _ edepth+1;
					END;
				estartingDown =>
					BEGIN
					UpdateYNextNewALAndprevedge[edge];
					edepth _ edepth-1;
					IF edepth=0 THEN
						IF adepth=0
						THEN EndSegment[edge]
						ELSE StartSegment[edge];
					END;
				ENDCASE;
				[edge,edgetype] _ GetEdge[layer];
			ENDLOOP;
			END;
		ActiveList[layer] _ newActiveList;
		FOR edge _ pendingFreeEdges,nextedge UNTIL edge=NIL DO
			nextedge _ edge.next;
			FreeEdge[edge];
		ENDLOOP;
		FOR edge _ EdgeListQueue,nextedge UNTIL edge=NIL DO
			nextedge _ edge.next;
			AddToEdgeList[layer,edge];
		ENDLOOP;
		IF EdgeList[layer]#NIL THEN YNext[layer] _ MIN[YNext[layer],EdgeList[layer].ystart];
		YPrev[layer] _ YCurr[layer];
		YCurr[layer] _ YNext[layer];
	ENDLOOP; --UNTIL (...
	ENDLOOP; --FOR layer ...
	FOR i IN [0..LENGTHLayerArray) DO --because next entry requires re-finding YNext[layer]
		YCurr[layer] _ YPrev[layer];
	ENDLOOP;
	END;

CheckIntersection: PROCEDURE[e1,e2: Edge, ylow,yhigh: REAL] RETURNS[y: REAL] =
--check for and deal with intersection of e1 and e2 between ylow and yhigh
--Returns either yhigh or y of intersection
--assumes edges are in order at ylow
	BEGIN
	IF e1#NIL AND XatY[e1,yhigh]>XatY[e2,yhigh] THEN
		BEGIN
		xint,yint: REAL;
		s1: REAL _ Slope[e1];
		s2: REAL _ Slope[e2];
		yint _ IF s1#s2 THEN
					MAX[ylow, MIN[yhigh,
						((e2.ystart*s2 - e1.ystart*s1)-(e2.xstart - e1.xstart))/(s2 - s1)]]
				ELSE yhigh;
		xint _ XatY[IF e1.vert THEN e1 ELSE e2,yint];
		--put upper fragments back onto edgeList
		IF yint<e1.yend THEN
			BEGIN
			e1upper: Edge _ VersatecMakeEdge[xint,yint,Xend[e1],e1.yend,e1.up];
 		--mustn't put it back on edgeList yet in case yint=ylow
			QueueForEdgeList[e1upper];
			END;
		IF yint<e2.yend THEN
			BEGIN
			e2upper: Edge _ VersatecMakeEdge[xint,yint,Xend[e2],e2.yend,e2.up];
			QueueForEdgeList[e2upper];
			END;
		--cut back e1 and e2
		WITH e:e1 SELECT IF e1.vert THEN vertical ELSE oblique FROM
		oblique => e.xend _ xint;
		ENDCASE;
		e1.yend _ yint;
		WITH e:e2 SELECT IF e2.vert THEN vertical ELSE oblique FROM
		oblique => e.xend _ xint;
		ENDCASE;
		e2.yend _ yint;
		IF yint=ylow THEN e1.flagout _ e2.flagout _ TRUE;
		RETURN[yint];
		END
	ELSE RETURN[yhigh];
	END;

--	The next 3 procedures (AddToEdgeList, PeekAtEdgeList, GetFromEdgeList) implement
--		the EdgeList and are subject to replacement

-- In this version the EdgeList is kept doubly linked and search for
--		insertion place is started at last-inserted Edge
--		Back pointers use the .mate field

--AddToEdgeList: PROCEDURE[layer: CARDINAL, edge: Edge] =
--	BEGIN
--	eptr: POINTER TO Edge;
--	y: REAL _ edge.ystart;
--	FOR eptr _ @EdgeList[layer], @eptr.next UNTIL eptr^=NIL DO
--		IF y<eptr.ystart OR (y=eptr.ystart AND EdgeLessThan[edge, eptr^, y]) THEN EXIT;
--	ENDLOOP;
--	edge.next _ eptr^;
--	eptr^ _ edge;
--	END;

AddToEdgeList: PUBLIC PROCEDURE[layer: CARDINAL, edge: Edge] =
	BEGIN
	e,save,start: Edge;
	y: REAL _ edge.ystart;
	start _ EdgeListEl[layer];
	EdgeListEl[layer] _ edge;
	IF EdgeList[layer]=NIL THEN
		BEGIN
		edge.next _ NIL;
		edge.mate _ NIL;
		EdgeList[layer] _ edge;
		RETURN;
		END;
	IF start=NIL THEN start _ EdgeList[layer];
--search forward
	save _ NIL;
	FOR e _ start, e.next UNTIL e=NIL DO
		IF y<e.ystart OR (y=e.ystart AND EdgeLessThan[edge, e, y])
			THEN GOTO searchbackwards;
		save _ e;
	REPEAT
		searchbackwards =>
			BEGIN --edge "<" e
			FOR e _ e.mate, e.mate UNTIL e=NIL DO
				IF e.ystart<y OR (e.ystart=y AND EdgeLessThan[e, edge, y])
					THEN GOTO append;
			REPEAT
				append =>
					BEGIN --append edge to e
					edge.next _ e.next;
					edge.mate _ e;
					e.next.mate _ edge;
					e.next _ edge;
					RETURN;
					END;
			ENDLOOP;
		--reached begin of list - insert edge before 1st element
			edge.next _ EdgeList[layer];
			edge.mate _ NIL;
			EdgeList[layer].mate _ edge;
			EdgeList[layer] _ edge;
			RETURN;
			END;
	ENDLOOP;
--reached end of list - append edge to save
	edge.next _ NIL;
	edge.mate _ save;
	save.next _ edge;
	END;

PeekAtEdgeList: PUBLIC PROCEDURE[layer: CARDINAL] RETURNS[edge: Edge] =
--Returns next edge from EdgeList without removing it from EdgeList
	BEGIN
	edge _ EdgeList[layer];
	END;

GetFromEdgeList: PUBLIC PROCEDURE[layer: CARDINAL] RETURNS[edge: Edge] =
--Returns next edge from EdgeList having removed it from EdgeList
	BEGIN
	edge _ EdgeList[layer];
	IF edge#NIL THEN
		BEGIN
		EdgeList[layer] _ edge.next;
		IF edge.next#NIL THEN edge.next.mate _ NIL; --***IF new
		EdgeListEl[layer] _ edge.next;
		edge.mate _ NIL; --clean up
		END;
	END;

GetEdge: PUBLIC PROCEDURE[layer: CARDINAL] RETURNS[edge: Edge, edgeType: EdgeType] =
	--Get next edge for new active list - filter out zero height edges
	BEGIN
	DO
		[edge,edgeType] _ GetEdge1[layer];
		IF edge=NIL OR edge.yend>edge.ystart THEN EXIT;
		FreeEdge[edge]; --exists and zero height
	ENDLOOP;
	END;

GetEdge1: PROCEDURE[layer: CARDINAL] RETURNS[edge: Edge, edgeType: EdgeType] =
	--Get next edge for new active list
	BEGIN
	peekAtEdgeList: Edge _ PeekAtEdgeList[layer];
	TakeFromActiveList: PROCEDURE =
		BEGIN
		edge _ ActiveList[layer];
		ActiveList[layer] _ ActiveList[layer].next;
		edgeType _	IF edge.yend<=YCurr[layer]
						THEN IF edge.up THEN aterminatingUp ELSE aterminatingDown
						ELSE IF edge.up THEN acontinuingUp ELSE acontinuingDown;
		END;
	TakeFromEdgeList: PROCEDURE =
		BEGIN
		edge _ GetFromEdgeList[layer];
		edgeType _ IF edge.up THEN estartingUp ELSE estartingDown;
	--tidy it up
		edge.flagout _ FALSE;
		edge.lastouty _ edge.ystart;
		edge.mate _ NIL;
		END;

	SELECT TRUE FROM
	ActiveList[layer]=NIL	=>
		BEGIN --take it from EdgeList provided starting at YCurr
		IF peekAtEdgeList#NIL AND peekAtEdgeList.ystart <= YCurr[layer] THEN
			TakeFromEdgeList[]
		ELSE
			BEGIN
			edge _ NIL;
			edgeType _ null;
			END;
		END;
	peekAtEdgeList=NIL => TakeFromActiveList[]; -- must be non-NIL if get here
	ENDCASE => --both lists are candidates
		IF peekAtEdgeList.ystart <= YCurr[layer] AND
			EdgeLessThan[peekAtEdgeList,ActiveList[layer], YCurr[layer]]
		THEN TakeFromEdgeList[]
		ELSE TakeFromActiveList[];
	END;

QueueForEdgeList: PROCEDURE[e: Edge] =
	BEGIN
	e.next _ EdgeListQueue;
	EdgeListQueue _ e;
	END;

Xend: PROCEDURE[edge: Edge] RETURNS[xend: REAL] = INLINE
	BEGIN
	RETURN[WITH e:edge SELECT IF edge.vert THEN vertical ELSE oblique FROM
			oblique => e.xend,
			ENDCASE => edge.xstart --i.e.vertical
	];
	END;

Slope: PROCEDURE[edge: Edge] RETURNS[slope: REAL] = INLINE
	BEGIN
	RETURN[WITH e:edge SELECT IF edge.vert THEN vertical ELSE oblique FROM
			oblique => e.slope,
			ENDCASE => 0 --i.e.vertical
			];
	END;

PrintList: PUBLIC PROCEDURE[list: Edge, layer: CARDINAL] =
	BEGIN
	e: Edge;
	WriteString["YPrev,YCurr,YNext["]; WriteDecimal[layer]; WriteString["]: "];
	WriteFloat[YPrev[layer]]; WriteChar[',];
	WriteFloat[YCurr[layer]]; WriteChar[',];
	WriteFloat[YNext[layer]]; WriteChar[CR];
	SELECT list FROM
	ActiveList[layer] => WriteLine["ActiveList"];
	EdgeList[layer] => WriteLine["EdgeList"];
	ENDCASE;
	WriteOctal[list]; WriteChar[CR];
	FOR e _ list, e.next UNTIL e=NIL DO
		WriteString["next:"]; WriteOctal[e.next]; WriteChar[SP];
		WriteString["xstart:"]; WriteFloat[e.xstart]; WriteChar[SP];
		WriteString["ystart:"]; WriteFloat[e.ystart]; WriteChar[SP];
		WriteString["xend:"]; WriteFloat[Xend[e]]; WriteChar[SP];
		WriteString["yend:"]; WriteFloat[e.yend]; WriteChar[SP];
		WriteString["slope:"]; WriteFloat[Slope[e]]; WriteChar[SP];
		WriteString["slant:"];
			WriteString[IF e.vert THEN "vertical" ELSE "oblique"]; WriteChar[SP];
		WriteString["up:"]; WriteChar[IF e.up THEN 'T ELSE 'F]; WriteChar[SP];
		WriteString["flagout:"]; WriteChar[IF e.flagout THEN 'T ELSE 'F]; WriteChar[SP];
		WriteString["lastouty:"]; WriteFloat[e.lastouty]; WriteChar[SP];
		WriteString["mate:"]; WriteOctal[e.mate]; WriteChar[SP];
		WriteString["XatYCurr: "]; WriteFloat[XatY[e,YCurr[layer]]]; WriteChar[CR];
		WriteChar[CR];
	ENDLOOP;
	END;

WriteFloat: PROCEDURE[r: REAL] =
	BEGIN
	WriteReal[WriteChar,r];
	END;

YNext,YCurr,YPrev: ARRAY [0..MaxLENGTHLayerArray) OF REAL;
EdgeList,EdgeListEl,ActiveList: ARRAY [0..MaxLENGTHLayerArray) OF Edge;
EdgeListQueue: Edge; --isolates edges being thrown back onto edge list

END.
(635)\f8 122b9B489b13B178b14B167b17B354b12B48b10B126b9B55b7B445b7B216b27B326b16B3756b17B1580b13B310b13B1153b14B165b15B348b7B304b8B163b18B271b16B763b16B82b4B206b5B200b9B1317b10B