DIRECTORYCD USING [Rect, Design];CDDrawQueue: CEDAR DEFINITIONS = BEGINDrawQueue: TYPE = REF DrawQueueRep; DrawQueueRep: TYPE;Request: TYPE = RECORD [key: REF, rect: CD.Rect];queueEmpty: PRIVATE READONLY REF;finishedForEver: PRIVATE READONLY REF;Create: PROC [design: CD.Design, stopFlag: REF BOOL, clip: CD.Rect _ [1,1,0,0] ] RETURNS [DrawQueue];ChangeClipArea: PROC [dq: DrawQueue, clip: CD.Rect _ [1,1,0,0] ];Destroy: PROC [dq: DrawQueue];Flush: PROC [dq: DrawQueue];QueueInsertDrawCommand: PROC [dq: DrawQueue, req: Request];InsertDrawCommand: PROC [design: CD.Design, req: Request];FetchCommand: PROC [dq: DrawQueue] RETURNS [req: Request];END.   V  CDDrawQueue.mesa   (a ChipNDale module)Copyright c 1983, 1984 by Xerox Corporation.  All rights reserved.by Christian Jacobi,  May 3, 1983 10:40 am last edited by Christian Jacobi,  September 19, 1985 2:58:03 am PDTThis module dispatches view refresh requests onto different queues which may bequerried by different viewer implementation.  --Think a DrawQueue representing a viewer--one DrawQueue is executed (emptied) by max one process--but arbitrary (typically only one) processes may fill the DrawQueue--$redraw: 	completely redraw this rect--$draw: 	draw this rect (over what's there)--queueEmpty: generated implicitely; hint that some lower priority stuff might be done; Do not insert this key explicitely.--finishedForEver: generated implicitely; hint that this is the last request for ever in this table; Do not insert this key explicitely.--Creates a DrawQueue--stopFlag^ tells any drawing process to stop volunterly and to fetch the next request. --stopFlag^ must not be modified any more outside this monitor!! until Delete is called--clip: initial clip area.--Users may request a stop by calling Flush.--changes the clipping aera for this DrawQueue--no more calls of QueueInsertDrawCommand on dq allowed!!--redraw process must disapear from itself,--when redraw process dispears and contains nomore--reference of dq, it is subject for garbage collection --The stopFlag is immediately set to TRUE and later--reset to FALSE when the redraw --process stopped the current command, if it then fetches another --command it gets the disapearforever command.--the drawing may stop after some time only,--and NOT immediately with procedure return--insert request into particular DrawQueue--insert request into all DrawQueue's of this design--returns next request--If not available waits until request is available or DrawQueue deletedÊS  ˜ codešœ'™'Kšœ
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