[RESOLVED] Infinite undo/redo: how do you implement it?

[bergerkiller]

Hello everyone.

I did this before, but it was really REALLY (really) messy and all it did was basically add and remove text and selection information from a stack. Result: When using Undo/Redo the selection got messed up, the text moved, sometimes causing lag of epic proportions. I need a way of having complete and smooth undo/redo class for storing all information I would possible need.

How to know whether or not to add an undo stack is easy, I just checked if the user clicked in the text or moved using the arrow keys. As soon a previous marking was given for "next text change needs to be backed up", it was backed up. At that point I stored the RTF and selection start/length.

Up to the question. What do I have to store of a RichTextbox control to be able to restore it to a previous state, and how can I reset it back to a previous state? See it as having a "RichTextBoxState" class:

Public Class RichTextBoxState
    Sub New(ByVal RTB As RichTextBox)
        Me.text = RTB.RTF
        Me.selectionstart = RTB.SelectionStart
        Me.selectionlength = RTB.SelectionLength
        '???
    End Sub
    Public text As String
    Public selectionstart As Integer
    Public selectionlength As Integer
    Public ??? As ???
    Public Sub Restore(ByVal RTB As RichTextBox)
        RTB.RTF = text
        RTB.Select(selectionstart, selectionlength)
        '???
    End Sub
End Class

After restoring it must display the EXACT same thing as when it was saved as a state.

Any help greatly appreciated.