DIRECTORY 
IO USING [STREAM],
Rope USING [ROPE];

SimpleStreams: CEDAR DEFINITIONS ~ BEGIN 
Create: PROC [header: Rope.ROPE ¬ NIL, echo: BOOL ¬ TRUE, windowSystem: REF ¬ NIL] RETURNS [in, out, err: IO.STREAM, hasEcho: BOOL];


CreateProcType: TYPE = PROC [header: Rope.ROPE ¬ NIL, echo: BOOL ¬ TRUE, windowSystem: REF ¬ NIL] RETURNS [in, out, err: IO.STREAM ¬ NIL, hasEcho: BOOL ¬ FALSE];

ImplementCreate: PROC [windowSystem: REF, create: CreateProcType, setCurrent: BOOL ¬ TRUE];
SetCurrentCreate: PROC [windowSystem: REF, scope: REF ¬ NIL];
END.

   |  
SimpleStreams.mesa
Copyright Ó 1988, 1992 by Xerox Corporation.  All rights reserved.
Christian Jacobi, August 26, 1988 11:12:22 am PDT
Christian Jacobi, October 6, 1988 12:50:03 pm PDT


Simple, window system independent stream IO facility.

--Creates top level window with input, output and error stream for typescript-style I/O.
--header: may be header line or simply first output, depending on window system.
--windowSystem: preferred window system.  Use this windowSystem if it is implemented,  
--	but otherwise use the "current" window system.  Usually NIL or an atom.
--echo: Whether input echos to the output stream.  If no echo, streams returned are 
--	extremely simple, the input stream offers no editing, comment filtering, 
--	or echoing to the output stream.  The client is free to layer these features  
--	anyway on top using the IO or EditedStream interface.
--	Restriction: there might be "windowSystem" implementors which fail to
--	implement the non echoed input stream; Clients can test for this using
--	the returned hasEcho boolean.
--Returns in, out, err: streams; out and err might be identical; err is useful for 
--	simulating unix, but is mostly ignored by more Cedarish clients.
--The streams will raise IO.EndOfStream if the window is interactively destroyed (using
--	a "windowSystem" dependent action).
--Closing a stream might or might not remove the window.
Backdoor features
--Type used for implementations of Create
--Provides procedure called on client requests for Create.
--It is ok to return NIL for err.
--It is ok to implement only non-echoed streams.
--It is tolerated but not liked to implement only echoed streams.
--See doc for restrictions on certain TYPE's of the windowSystem REF.

--Defines windowSystem to be used if windowSystem parameter in Create is defaulted
--No-op in case of non-implemented windowSystem  
--scope: validity range for call; see doc 

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