vbtkit/src/lego/ReactivityVBT.i3

 Copyright (C) 1992, Digital Equipment Corporation                         
 All rights reserved.                                                      
 See the file COPYRIGHT for a full description.                            
                                                                           
 Last modified on Thu Feb  8 22:56:41 PST 1996 by mhb                      
      modified on Fri Jun 11 21:44:25 PDT 1993 by meehan                   
      modified on Tue Jun 16 13:08:25 PDT 1992 by muller                   
      modified on Fri Mar 27 01:59:50 PST 1992 by steveg                   

<* PRAGMA LL *>

 A ReactivityVBT is a filter that can make its child active,
   passive, dormant, and invisible.  The {\em active\/} state does
   nothing; mouse and keyboard events are relayed to child. The {\em
   passive\/} state doesn't allow mouse or keyboard events to go to
   the child.
   The {\em dormant\/} state doesn't send mouse or keyboard events to
   the child; it also grays out the child.  The {\em vanish\/} state
   also doesn't send mouse or keyboard events to go to the child; in
   addition, it draws over the child in the background color, thereby
   making it invisible.


   When the state of a ReactivityVBT is set, the caller also
   specifies a cursor to be used.


   If a VBT-descendant of a ReactivityVBT is painted, it will appear
   correctly.  For example, if the ReactivityVBT is in the vanished
   state, the descendant will not appear until the state changes; if
   the ReactivityVBT is in a dormant state, the descendant will be
   grayed out.


   A ReactivityVBT also passes on any miscellaneous events to take
   the keyboard focus to the descendant that last acquired the
   keyboard focus. 


INTERFACE ReactivityVBT;

IMPORT Cursor, ETAgent, PaintOp, Rect, VBT;

TYPE
  State = {Active, Passive, Dormant, Vanish};
  T <: Public;
  Public =
    ETAgent.T OBJECT
    METHODS
      <* LL.sup <= VBT.mu *>
      init (ch: VBT.T; colors: PaintOp.ColorScheme := NIL): T;
      <* LL = VBT.mu.v *>
      paintDormant (r: Rect.T; colors: PaintOp.ColorScheme);
    END;

 The call v.init(..) initializes v as a ReactivityVBT
   with child ch and with an initial state of Active.  If
   colors is NIL, then PaintOp.bgFg is used instead.  The
   colors are used to draw the vanished and dormant states.


   The implementation calls v.paintDormant(r, colors) to paint
   the part of ch bounded by rectangle r when v's state
   is Dormant.  The ``current colors'' of v are passed as
   colors.  Initially, the current colors are those that were
   specified when the ReactivityVBT was initialized.  They can
   be changed using the SetColors procedure.  The default
   method paints a Pixmap.Gray texture using
   colors.transparentBg.  


PROCEDURE Set (v: T; state: State; cursor: Cursor.T);
<* LL.sup = VBT.mu *>

 Change v's state and cursor, and mark v for redisplay. 

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

 Retrieve v's current state. 

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

 Retrieve v's current cursor. 

PROCEDURE SetColors (v: T; colors: PaintOp.ColorScheme);
<* LL.sup = VBT.mu *>

 Change the colors that v uses for the Dormant and Vanish
   states.  If v is currently in the Dormant or Vanish
   state, mark v for redisplay. 

END ReactivityVBT.