--- a/ValueModel.st	Sat May 06 16:15:18 1995 +0200
+++ b/ValueModel.st	Tue May 09 02:23:22 1995 +0200
@@ -1,5 +1,7 @@
-Model subclass:#ValueModel 
-	 instanceVariableNames:'accepted'
+'From Smalltalk/X, Version:2.10.5 on 9-may-1995 at 12:03:02 pm'!
+
+Model subclass:#ValueModel
+	 instanceVariableNames:'accepted interrest'
 	 classVariableNames:''
 	 poolDictionaries:''
 	 category:'Interface-Support'
@@ -7,14 +9,42 @@
 
 !ValueModel class methodsFor:'documentation'!
 
+Model class methodsFor:'documentation'!
+
+copyright
+"
+ COPYRIGHT (c) 1995 by Claus Gittinger
+              All Rights Reserved
+
+ This software is furnished under a license and may be used
+ only in accordance with the terms of that license and with the
+ inclusion of the above copyright notice.   This software may not
+ be provided or otherwise made available to, or used by, any
+ other person.  No title to or ownership of the software is
+ hereby transferred.
+"
+!
+
+version
+"
+$Header: /cvs/stx/stx/libview2/ValueModel.st,v 1.4 1995-05-09 00:22:56 claus Exp $
+"
+!
+
 documentation
 "
     abstract superclass for ValueHolders and Adaptors.
+    It does not itself know how and where the value is stored,
+    but knows about interrested objects (which get informed, whenever
+    the value changes) and keeps track if the value was ever accepted.
 
     Notice: this class was implemented using protocol information
     from alpha testers - it may not be complete or compatible to
     the corresponding ST-80 class. If you encounter any incompatibilities,
     please forward a note to the ST/X team.
+
+    subclasses must redefine: #setValue: and #value
+    (and optionally redefine #value:)
 "
 ! !
 
@@ -24,14 +54,33 @@
     ^ (super new) initialize
 ! !
 
-!ValueModel methodsFor:'initialization'!
+!ValueModel methodsFor:'change notification'!
 
-initialize
-    accepted := false
+notifyChange:aSymbol
+    interrest notNil ifTrue:[
+        interrest keysAndValuesDo:[:someone :selector |
+            someone perform:selector
+        ].
+    ].
+    self changed:aSymbol
 ! !
 
 !ValueModel methodsFor:'accessing'!
 
+value:anObject
+    |oldValue|
+
+    oldValue := self value.
+    self setValue:anObject.
+    anObject ~= oldValue ifTrue:[
+        self notifyChange:#value
+    ]
+!
+
+accepted
+    ^ accepted
+!
+
 accept
     accepted := true
 !
@@ -42,15 +91,35 @@
 
 setValue:newValue 
     self subclassResponsibility
+! !
+
+!ValueModel methodsFor:'initialization'!
+
+initialize
+    accepted := false
+! !
+
+!ValueModel methodsFor:'interrest'!
+
+retractInterrestFor:someone
+    "release interrest i.e. do no longer send changeMsg to changeReceiver
+     iff someone is the changeReceiver.
+     This can be used to (temporarily) turn off information sends,
+     to break endless cycles (if two values change each other)"
+
+    interrest notNil ifTrue:[
+	interrest removeKey:someone ifAbsent:nil
+    ]
 !
 
-value:anObject
-    |oldValue|
+onChangeSend:selector to:someone
+    "add an interrest, arranging that
+     a message with selector will be sent to someone 
+     when my value changes."
 
-    oldValue := self value.
-    self setValue:anObject.
-    anObject ~= oldValue ifTrue:[
-	self changed:#value
-    ]
+    interrest isNil ifTrue:[
+	interrest := IdentityDictionary new
+    ].
+    interrest at:someone put:selector
 ! !