This thread is for discussions of Multiple Undo/Redo.

This is very useful code.  Thanks.  I fixed what seem to me to be a couple of bugs.

Bug 1

If the Delete key is used to delete the next character, status will not get updated.

Fix For Bug 1

In Code:

RichTextBox1_KeyDown

, after

       Code:

.ModifyType = urDeleteText
       AddToUndoStack cUndo

I added

       Code:

UpdateStatus

This is necessary because, if you just delete the next character, you have not changed the selection start point or the selection length (0), so Code:

RichTextBox1_SelChange

, which includes a call of Code:

UpdateStatus

, will not get triggered.

Bug 2

After a redo followed by an undo, the redo could not be done again.

Maybe this is supposed to be a feature rather than a bug, but I think it is a bug:  that is not how Microsoft Word or the VB6 editor behave, and I do not want it to happen in my program.

Fix For Bug 2

Delete the following code.

Code:

Private Sub RichTextBox1_Change()
If bRedoing Then
   bRedoing = False
   ClearStack RedoStack
End If
End Sub

This code is excellent. Most people should find it simple to understand and very easy to integrate with an application.

Found one bug. If you highlight a block of text, then press the TAB key, the text is properly replaced. However, you can't undo the action. This bug can be fixed as follows:

In rtDoc_KeyPress(KeyAscii As Integer)

Change this line:

   ElseIf KeyAscii >= 32 Or KeyAscii = 13 Then

To this:
   
   ElseIf KeyAscii >= 32 Or KeyAscii = 13 Or KeyAscii = vbKeyTab Then