DIRECTORYImagerPixelMap USING [DeviceRectangle];ImagerManhattan: CEDAR DEFINITIONS~ BEGINDeviceRectangle: TYPE ~ ImagerPixelMap.DeviceRectangle;Polygon: TYPE ~ LIST OF DeviceRectangle;Validate: PROC [polygon: Polygon] RETURNS [Polygon];InvalidManhattanPolygon: ERROR;CreateFromRuns: PROC [runs: PROC[ -- Create calls this backrun: PROC[sMin, fMin: INTEGER, fSize: NAT],  -- client calls this from inside runs.repeat: PROC[timesToRepeatScanline: NAT]  -- client calls this to repeat a scanline]] RETURNS [Polygon];CreateFromBox: PROC [deviceRectangle: DeviceRectangle] RETURNS [Polygon];Destroy: PROC [rectangleList: LIST OF DeviceRectangle];Copy: PROC [polygon: Polygon] RETURNS [Polygon];Union: PROC [a, b: Polygon] RETURNS [Polygon];Intersection: PROC [a, b: Polygon] RETURNS [Polygon];Difference: PROC [a, b: Polygon] RETURNS [Polygon];Shift: PROC [polygon: Polygon, sShift, fShift: INTEGER];Canonicalize: PROC [rectangleList: LIST OF DeviceRectangle] RETURNS [Polygon];BoundingBox: PROC [polygon: Polygon] RETURNS [DeviceRectangle];CountBoxes: PROC [polygon: Polygon] RETURNS [INT];CountRuns: PROC [polygon: Polygon] RETURNS [INT];MapRuns: PROC [polygon: Polygon, run: PROC [sMin, fMin: INTEGER, fSize: NAT]];Visibility: TYPE ~ {visible, partlyVisible, invisible};IsVisible: PROC [mask, clipper: Polygon] RETURNS [Visibility];END.  \  ImagerManhattan.mesaCopyright c 1984, 1985 by Xerox Corporation.  All rights reserved.Michael Plass, December 30, 1983 2:22 pmDoug Wyatt, March 7, 1985 2:38:55 pm PSTProvides operations on manhattan polygons.The coordinates are given in terms of s and f (for slow and fast).Data typesRECORD [sMin, fMin: INTEGER, sSize, fSize: NAT];If a and b are consecutive boxes in the list, must have eithera.sMin = b.sMin AND a.sSize = b.sSize AND a.fMin+a.fSize <= b.fMinORa.sMin+a.sSize <= b.sMinChecks that the above invariant is satisfied.May be raised by Validate.Polygon CreationThe runs proc should call run for each run, in non-descreasing s. It may call repeat to duplicate a scanline just entered.Polygon DestructionPuts the nodes on an avail list to be re-used;  much faster than letting the garbage collector do the work, but don't destroy a list unless you are sure nobody is depending on it.  (The avail list nodes will get garbage collected eventually if they are unneeded.)Making new Polygons from oldModifying existing PolygonsTurns a list of arbitrary rectangles into a valid Polygon.  Re-uses the storage, so copy first if rectangleList might be shared.Extracting info from PolygonsSELECT Intersection[mask, clipper] FROM= empty => invisible,= mask => visible,ENDCASE => partlyVisible;N. B. will return invisible if mask is empty.Êü  ˜ code™Kšœ
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