# HG changeset patch
# User ca
# Date 855934751 -3600
# Node ID 5e4319953a0ba41a73ff83e7a0b0e0d908b554c6
# Parent  8301d6b9e67c176b1d10298e8450d05c246fc474
*** empty log message ***

diff -r 8301d6b9e67c -r 5e4319953a0b UIObjectView.st
--- a/UIObjectView.st	Fri Feb 14 16:35:32 1997 +0100
+++ b/UIObjectView.st	Fri Feb 14 16:39:11 1997 +0100
@@ -7,6 +7,13 @@
 	category:'Interface-UIPainter'
 !
 
+Object subclass:#UndoHistory
+	instanceVariableNames:'history transaction enabled modifiedAction'
+	classVariableNames:''
+	poolDictionaries:''
+	privateIn:UIObjectView
+!
+
 
 !UIObjectView class methodsFor:'defaults'!
 
@@ -1539,6 +1546,209 @@
 
 ! !
 
+!UIObjectView::UndoHistory class methodsFor:'constants'!
+
+maxHistorySize
+    "returns maximum size of history before removing oldest
+     record
+    "
+    ^ 50
+
+
+! !
+
+!UIObjectView::UndoHistory class methodsFor:'instance creation'!
+
+new
+    ^ self basicNew initialize
+
+
+! !
+
+!UIObjectView::UndoHistory methodsFor:'accessing'!
+
+modifiedAction:aBlockWithOneArg
+    "the block is evaluated whenever the history changed; the argument to the
+     block is the newest transaction identifier retrived from 'openTransaction'
+    "
+    modifiedAction := aBlockWithOneArg
+
+
+! !
+
+!UIObjectView::UndoHistory methodsFor:'initialization'!
+
+initialize
+    super initialize.
+    self  reinitialize.
+
+
+!
+
+reinitialize
+    "reinitialize all attributes
+    "
+    history := OrderedCollection new.
+    transaction := nil.
+    enabled := true.
+
+
+! !
+
+!UIObjectView::UndoHistory methodsFor:'notifications'!
+
+modified
+    "raise notification; history changed
+    "
+    modifiedAction notNil ifTrue:[
+        |what|
+
+        history isEmpty ifTrue:[what := nil]
+                       ifFalse:[what := history last first].
+
+        modifiedAction value:what
+    ]
+
+
+! !
+
+!UIObjectView::UndoHistory methodsFor:'testing'!
+
+isEmpty
+    "returns true if undo history is empty
+    "
+    ^ history isEmpty
+
+
+!
+
+isTransactionOpen
+    ^ (enabled and:[transaction notNil])
+!
+
+notEmpty
+    "returns true if undo history is not empty
+    "
+    ^ history notEmpty
+
+
+! !
+
+!UIObjectView::UndoHistory methodsFor:'transaction'!
+
+addUndoBlock:anUndoBlock
+    "undo block to restore changes; add block to current transaction
+    "
+    enabled ifTrue:[
+        transaction isNil ifTrue:[
+            "no existing transaction
+            "
+            self halt
+        ] ifFalse:[
+            (transaction at:2) add:anUndoBlock
+        ]
+    ]
+
+
+!
+
+closeTransaction
+    "close current transaction
+    "
+    self isTransactionOpen ifTrue:[
+        transaction last isEmpty ifTrue:[
+            "empty undo transaction
+            "
+            transaction := nil
+        ] ifFalse:[
+            history addLast:transaction.
+            transaction := nil.
+
+            history size > (self class maxHistorySize) ifTrue:[
+                history removeFirst
+            ].
+            self modified
+        ]
+    ]
+
+
+!
+
+disabledTransitionDo:aBlock
+    "disable transitions during evaluating the block
+    "
+    |oldState|
+
+    oldState := enabled.
+    enabled  := false.
+    aBlock value.
+    enabled  := oldState.
+!
+
+openTransaction:what
+    "open a new transaction
+    "
+    enabled ifTrue:[
+        transaction notNil ifTrue:[
+            "transaction within transaction
+            "
+            self halt.
+        ] ifFalse:[
+            transaction := Array with:what with:OrderedCollection new
+        ]
+    ]
+
+!
+
+transactionNamed:what do:aBlock
+    "open a transaction; perform the block; at least close the transaction
+    "
+    self isTransactionOpen ifFalse:[
+        self openTransaction:what.
+        aBlock value.
+        self closeTransaction
+    ] ifTrue:[
+        aBlock value
+    ]
+! !
+
+!UIObjectView::UndoHistory methodsFor:'undo'!
+
+undoLast
+    "undo last transactions; an open transaction will be closed;
+     transactions during undo are disabled
+    "
+    self undoLast:1
+
+
+!
+
+undoLast:nTransactions
+    "undo last n transactions; an open transaction will be closed;
+     transactions during undo are disabled
+    "
+    |actions n|
+
+    transaction := nil.
+    n := nTransactions min:(history size).
+
+    n ~~ 0 ifTrue:[
+        enabled := false.
+
+        n timesRepeat:[
+            actions := (history removeLast) last.
+
+            actions reverseDo:[:aUndoBlock|
+                aUndoBlock value
+            ]
+        ].
+        enabled := true.
+        self modified.
+    ]
+
+
+! !
+
 !UIObjectView class methodsFor:'documentation'!
 
 version