DIRECTORYRope					USING [ ROPE ];EdgeBlt: CEDAR DEFINITIONS~ BEGINEdgeDesc: TYPE ~ RECORD[val: INT32,					-- current value for incrementation, byte address or valuestepsLeft: WORD _ 0,		-- number of increments remaininglength: WORD _ 0,			-- total number of increments to make	hiccups: WORD _ 0,			-- number of offsets (hiccups) to makelngthIncr: INTEGER _ 0,	-- amount to increment byhicIncr: INTEGER _ 0,		-- amount to offset at hiccupbias: INTEGER _ 0,			-- change to number of increments to first offset (for wizards)indirect: BOOLEAN _ TRUE,	-- incrementing addresses if TRUE, else valuesnextEdge: CARD16 _ 0	-- next edge if part of a chain of edges (index in Sequence)];EdgeSequence: TYPE ~ RECORD [length: NAT _ 0, 									 s: SEQUENCE maxLength: NAT OF EdgeBlt.EdgeDesc ];									 EdgeBltOptions: TYPE ~ RECORD[includeStart: BOOL _ TRUE,			-- include start pointincludeEnd: BOOL _ TRUE				-- include endpoint];defaultOptions: EdgeBltOptions ~ [TRUE, TRUE];EdgeBltTable: TYPE ~ RECORD[dst, src: EdgeDesc,options: EdgeBltOptions _ defaultOptions];EdgeBltError: SIGNAL [reason: ErrorDesc];ErrorDesc: TYPE ~ RECORD [code: ATOM, explanation: Rope.ROPE];Incr: PROC[edge: EdgeDesc, array: REF EdgeSequence _ NIL] RETURNS[EdgeDesc];Blt: PROC[ebt: EdgeBltTable];END.  ò  EdgeBlt.mesaCopyright Ó 1987 by Xerox Corporation.  All rights reserved.Frank Crow, June 12, 1987 3:49:32 pm PDTA general-purpose Bresenham incrementer.Type DefinitionsBasic ProceduresThe fractional increment Dy/Dx must be added to y for every new position x.  Whenever the fraction overflows, y is incremented, effectively subtracting 1 from the fraction.  By removing the fractional part from y, we can instead increment by Dy until Dx is reached.  To center the positions of the y-increments along x, the incrementation by Dy should be started at Dx/2.  To further simplify, decrement by 2Dy and start at Dx, testing for < 0.  In the following read Dx as longSize and Dy as shortSize.Increments EdgeDesc once unless runToHiccup is set Ê-  ˜ Ihead2šœ™šœ<™<J™(J™(J™ šÏk	˜	Jšœ	œœ˜——šÏnœœ˜Jšœ˜—šœ™Idefault˜ šœ
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