Question

I notice that Project 2007 has the functions that allow operations that can be undone to be placed in a single stack item, or ‘undo transaction’. For example:

Application.OpenUndoTransaction 'Create 6 tasks' Dim i As Integer For i = 1 To 6     ActiveProject.Tasks.Add 'UndoMe ' & i Next Application.CloseUndoTransaction  

What this means is that the user can undo all of the actions in a single undo action, rather than 6 times.

This would be great to implement in Word and/or Excel, as I’m doing some things in VSTO that make multiple changes at once, and it’ll be a bit annoying for the user if they have to click on Undo several times if they make a mistake. Although those specific functions don’t appear to exist, does anyone know if / how this can be done in some way?

Answer 1

You can simulate transactional behavior in Word by overwriting the Undo and Redo command routines in VBA (I don’t think that overwriting built-in Word commands is possible using VSTO alone, though). The start of a transaction is marked by adding a bookmark, the end is marked by removing the bookmark.

When calling undo, we check whether the transaction mark bookmark is present and repeat the undo until the marker is gone. Redo is working the same way. This mechanism supports transactional undo/redo of all modifications done to the document content. However, to allow undo/redo of modifications to the document properties a special mechanism needs to be implemented using the SetCustomProp macro. Document properties should not be set directly but via this macro only.

Update: I forgot to clearly mention that this approach only works with the keyboard shortcuts and the menu commands, clicking the toolbar button still does a single-step undo. We therefore decided to replace the toolbar buttons with custom ones. The code has been in use for quite a while With Word 2003 (it’s not tested with Word 2007, so be prepared for surprise 😉

Option Explicit  ' string constants for Undo mechanism Public Const BM_IN_MACRO As String = '_InMacro_'  Public Const BM_DOC_PROP_CHANGE As String = '_DocPropChange_' Public Const BM_DOC_PROP_NAME As String = '_DocPropName_' Public Const BM_DOC_PROP_OLD_VALUE As String = '_DocPropOldValue_' Public Const BM_DOC_PROP_NEW_VALUE As String = '_DocPropNewValue_'  '----------------------------------------------------------------------------------- ' Procedure : EditUndo ' Purpose   : Atomic undo of macros '             Note: This macro only catches the menu command and the keyboard shortcut, '                   not the toolbar command '----------------------------------------------------------------------------------- Public Sub EditUndo() ' Catches Ctrl-Z      'On Error Resume Next     Dim bRefresh As Boolean     bRefresh = Application.ScreenUpdating     Application.ScreenUpdating = False      Do         If ActiveDocument.Bookmarks.Exists(BM_DOC_PROP_CHANGE) Then             Dim strPropName As String             Dim strOldValue As String              strPropName = ActiveDocument.Bookmarks(BM_DOC_PROP_NAME).Range.Text             strOldValue = ActiveDocument.Bookmarks(BM_DOC_PROP_OLD_VALUE).Range.Text             ActiveDocument.CustomDocumentProperties(strPropName).Value = strOldValue         End If      Loop While (ActiveDocument.Undo = True) _        And ActiveDocument.Bookmarks.Exists(BM_IN_MACRO)      Application.ScreenUpdating = bRefresh End Sub  '----------------------------------------------------------------------------------- ' Procedure : EditRedo ' Purpose   : Atomic redo of macros '             Note: This macro only catches the menu command and the keyboard shortcut, '                   not the toolbar command '----------------------------------------------------------------------------------- Public Sub EditRedo() ' Catches Ctrl-Y      Dim bRefresh As Boolean     bRefresh = Application.ScreenUpdating     Application.ScreenUpdating = False      Do         If ActiveDocument.Bookmarks.Exists(BM_DOC_PROP_CHANGE) Then             Dim strPropName As String             Dim strNewValue As String              strPropName = ActiveDocument.Bookmarks(BM_DOC_PROP_NAME).Range.Text             strNewValue = ActiveDocument.Bookmarks(BM_DOC_PROP_NEW_VALUE).Range.Text             ActiveDocument.CustomDocumentProperties(strPropName).Value = strNewValue         End If      Loop While (ActiveDocument.Redo = True) _        And ActiveDocument.Bookmarks.Exists(BM_IN_MACRO)      Application.ScreenUpdating = bRefresh  End Sub  '----------------------------------------------------------------------------------- ' Procedure : SetCustomProp ' Purpose   : Sets a custom document property '----------------------------------------------------------------------------------- Public Function SetCustomProp(oDoc As Document, strName As String, strValue As String)      Dim strOldValue As String      On Error GoTo existsAlready     strOldValue = ''     oDoc.CustomDocumentProperties.Add _         Name:=strName, LinkToContent:=False, Value:=Trim(strValue), _         Type:=msoPropertyTypeString     GoTo exitHere  existsAlready:     strOldValue = oDoc.CustomDocumentProperties(strName).Value     oDoc.CustomDocumentProperties(strName).Value = strValue  exitHere:     ' support undo / redo of changes to the document properties     'On Error Resume Next     Dim bCalledWithoutUndoSupport  As Boolean      If Not ActiveDocument.Bookmarks.Exists(BM_IN_MACRO) Then         ActiveDocument.Range.Bookmarks.Add BM_IN_MACRO, ActiveDocument.Range         bCalledWithoutUndoSupport = True     End If      Dim oRange As Range     Set oRange = ActiveDocument.Range      oRange.Collapse wdCollapseEnd     oRange.Text = ' '     oRange.Bookmarks.Add 'DocPropDummy_', oRange      oRange.Collapse wdCollapseEnd     oRange.Text = strName     oRange.Bookmarks.Add BM_DOC_PROP_NAME, oRange      oRange.Collapse wdCollapseEnd     oRange.Text = strOldValue     oRange.Bookmarks.Add BM_DOC_PROP_OLD_VALUE, oRange      oRange.Collapse wdCollapseEnd     oRange.Text = strValue     oRange.Bookmarks.Add BM_DOC_PROP_NEW_VALUE, oRange      oRange.Bookmarks.Add BM_DOC_PROP_CHANGE     ActiveDocument.Bookmarks(BM_DOC_PROP_CHANGE).Delete      Set oRange = ActiveDocument.Bookmarks(BM_DOC_PROP_NEW_VALUE).Range     ActiveDocument.Bookmarks(BM_DOC_PROP_NEW_VALUE).Delete     If Len(oRange.Text) > 0 Then oRange.Delete      Set oRange = ActiveDocument.Bookmarks(BM_DOC_PROP_OLD_VALUE).Range     ActiveDocument.Bookmarks(BM_DOC_PROP_OLD_VALUE).Delete     If Len(oRange.Text) > 0 Then oRange.Delete      Set oRange = ActiveDocument.Bookmarks(BM_DOC_PROP_NAME).Range     ActiveDocument.Bookmarks(BM_DOC_PROP_NAME).Delete     If Len(oRange.Text) > 0 Then oRange.Delete      Set oRange = ActiveDocument.Bookmarks('DocPropDummy_').Range     ActiveDocument.Bookmarks('DocPropDummy_').Delete     If Len(oRange.Text) > 0 Then oRange.Delete      If bCalledWithoutUndoSupport And ActiveDocument.Bookmarks.Exists(BM_IN_MACRO) Then         ActiveDocument.Bookmarks(BM_IN_MACRO).Delete     End If  End Function  '----------------------------------------------------------------------------------- ' Procedure : SampleUsage ' Purpose   : Demonstrates a transaction '----------------------------------------------------------------------------------- Private Sub SampleUsage()      On Error Resume Next      ' mark begin of transaction     ActiveDocument.Range.Bookmarks.Add BM_IN_MACRO      Selection.Text = 'Hello World'     ' do other stuff      ' mark end of transaction     ActiveDocument.Bookmarks(BM_IN_MACRO).Delete  End Sub