vbtkit/src/lego/BooleanVBT.i3

 Copyright (C) 1992, Digital Equipment Corporation 
 All rights reserved. 
 See the file COPYRIGHT for a full description. 
 
 Last modified on Fri Jun 11 14:42:58 PDT 1993 by meehan 
      modified on Fri Feb  5 17:39:05 PST 1993 by mhb    
      modified on Tue Jun 16 13:09:03 PDT 1992 by muller 
 modified on Fri Mar 27 01:48:28 1992 by steveg 

<* PRAGMA LL *>
<* PRAGMA SUBTYPE *>

 A BooleanVBT is a multi-filter that maintains a Boolean state for
   its VBT-child.


   When the action procedure of the button would normally be
   invoked, the value of the state of the BooleanVBT is toggled and
   the callback method on the BooleanVBT is invoked.


   The multi-child of a BooleanVBT is defined to be the multi-child
   of the ButtonVBT. 


INTERFACE BooleanVBT;

IMPORT ButtonVBT, HighlightVBT, VBT;

TYPE
  <* SUBTYPE T <: MultiFilter.T *>
  T <: Public;
  Public = HighlightVBT.T OBJECT
           METHODS
             <* LL <= VBT.mu *>
             init (button: ButtonVBT.T): T;
             <* LL = VBT.mu *>
             callback (READONLY cd: VBT.MouseRec);
           END;

 The call v.init(...) initializes v as a BooleanVBT with an
   initial state of FALSE. The default callback method is a no-op.


   Warning: This call modifies the action field of button. 


PROCEDURE Put (v: T; state: BOOLEAN);
<* LL.sup = VBT.mu *>

 Set v's state. 

PROCEDURE Get (v: T): BOOLEAN;
<* LL.sup = VBT.mu *>

 Returns v's current state. 

END BooleanVBT.