(* Copyright (C) 1992, Digital Equipment Corporation                         *)
(* All rights reserved.                                                      *)
(* See the file COPYRIGHT for a full description.                            *)
(*                                                                           *)
(* Last modified on Mon Aug 10  0:23:25 PDT 1992 by meehan *)
(*      modified on Tue Jun 16 13:08:49 PDT 1992 by muller *)
(*      modified on Mon Jun 15 21:02:02 1992 by mhb *)

(* A "GuardedBtnVBT" is a "ButtonVBT" that protects
   its child against unintentional mouse clicks.  While the guard
   is displayed, mouse clicks are not forwarded.  To remove the
   guard, click on the button.  The guard is restored after the
   next upclick, chord-cancel, or when the mouse leaves the
   domain of the "VBT".

   Typically, a "GuardedBtnVBT" is placed above a ``dangerous''
   button, like one that terminates an application.  This forces the
   user to click twice to terminate the application---the first time
   to remove the guard, and the second time to invoke the button
   that terminates the application.

   A "GuardedBtnVBT" is much closer to being a VBTkit switch
   than a Trestle button.  There's a "callback" method
   (invoked when the guard is removed), and the guard is a
   multi-filter.  However, the client does not provide a feedback;
   it is hard-wired into the "GuardedBtnVBT" implementation. *)

INTERFACE GuardedBtnVBT;

IMPORT ButtonVBT, MultiClass, PaintOp, VBT;

TYPE
  T <: Public;
  Public = ButtonVBT.T OBJECT
           METHODS
             init (ch        : VBT.T;
                   colors    : PaintOp.ColorScheme := NIL;
                   multiclass: MC                  := NIL  ): T;
             callback (READONLY cd: VBT.MouseRec);
           END;

  MC <: MultiClass.T;
(* The type "MC" overrides the "replace", "pred", and "succ" methods
   of "MultiClass.T". *)

END GuardedBtnVBT.