--File: MergeDefs.mesa
-- Written by Maureen Stone, October 1980
-- based on Polygon, Written by Martin Newell, May 1980
-- Last updated: October 31, 1980  6:32 PM

DIRECTORY
	PointDefs: FROM "PointDefs";

MergeDefs: DEFINITIONS =

BEGIN

AreaDescriptor: TYPE = POINTER TO AreaBlock;

AreaCreate: PUBLIC PROCEDURE RETURNS[area: AreaDescriptor];
-- Create new polygon

AreaNewBox: PUBLIC PROCEDURE[area: AreaDescriptor,
	tl,br: PointDefs.ScrPt,z: INTEGER];
-- Add box to area

AreaGenerate: PUBLIC PROCEDURE[area: AreaDescriptor,
					outputBox: PROCEDURE[tl,br: PointDefs.ScrPt, z: INTEGER]];
-- Generate the area defined up to last AreaNewBox 
-- This procedure AreaDestroys the area, which therefore is no longer valid 

AreaDestroy: PUBLIC PROCEDURE[area: AreaDescriptor];
-- Destroy area

-- Internal types

Edge: TYPE = POINTER TO EdgeRecord;
EdgeRecord: TYPE = RECORD[
	next: Edge,
	x: INTEGER,
	ystart: INTEGER,
	yend: INTEGER,
	z: INTEGER,	--an indication of overlap order.  z constant for whole box
	lastouty: INTEGER,		--y value where edge of deferred box was last output
	mate: Edge,			--other edge making up a deferred box
	up: BOOLEAN,			--TRUE if edge defined in increasing y
	flagout: BOOLEAN	--TRUE if edge will need to be output at ycurr
];
AreaBlock: TYPE = RECORD[
		edgeList: Edge,			--unprocessed edges
		edgeListEl: Edge,		--last edge added to EdgeList
		activeList: Edge		--edges being processed
		];

END.(635)\206b9B24b14B32b10B73b10B98b12B235b11B78b4B32b10B400b9B