Copyright (C) 1992, Digital Equipment Corporation                         
 All rights reserved.                                                      
 See the file COPYRIGHT for a full description.                            
 Last modified on Fri Jun 11 10:51:25 PDT 1993 by meehan 
      modified on Mon Feb  1 21:29:51 PST 1993 by mhb    
      modified on Tue Jun 16 13:08:49 PDT 1992 by muller 
A GuardedBtnVBT 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.


IMPORT ButtonVBT, PaintOp, VBT;

  T <: Public;
  <* SUBTYPE T <: MultiFilter.T *>
  Public =
    ButtonVBT.T OBJECT
      <* LL <= VBT.mu *>
      init (ch: VBT.T; colors: PaintOp.ColorScheme := NIL): T;
      <* LL = VBT.mu *>
      callback (READONLY cd: VBT.MouseRec);

END GuardedBtnVBT.